# How does an aircraft's wing work?



## RogerS (7 Sep 2012)

My theoretical understanding is, apparently, wrong!

What do you think?


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## mailee (7 Sep 2012)

:?: :?: :?: it would help to know what your theory is first? Air travels faster over the upper surface of the wing creating a lower pressure so lifting the wing, as far as I know :?


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## Eric The Viking (7 Sep 2012)

It's all down to the bolts inside, which you can't see, that fix the wing securely to the fuselage, thus preventing it falling off. 

The other wing is usually exactly the same, only a mirror image of the first one.

Simples really

E.


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## Tom K (7 Sep 2012)

Yeah just blurt it out Rog did you think air passing under the wing held the plane up?


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## duncanh (7 Sep 2012)

mailee":23z7wk6j said:


> :?: :?: :?: it would help to know what your theory is first? Air travels faster over the upper surface of the wing creating a lower pressure so lifting the wing, as far as I know :?



Agreed.



RogerS":23z7wk6j said:


> My theoretical understanding is, apparently, wrong!
> What do you think?



I assume that your understanding was that this difference in air speed was due to: for adjacent air particles at the front of the wing, the one that goes over the top of the wing has to travel faster so that it can meet up again at the back. This causes less air pressure above the wing. This is the explanation is often given but it doesn't make sense as there's no reason for the 2 air particles to need to be together at the back of the wing - they're not connected in any way.


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## James C (7 Sep 2012)

The particles aren't connected in any form it just an easier way of imagining the actual situation. The plane moves through the air at a constant speed.


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## Lons (8 Sep 2012)

Thanks for that question just a week before our flights :roll: #-o 

Anyway, loads of info on the web - heres an interesting argument on the theories; 
http://iopscience.iop.org/0031-9120/38/ ... _6_001.pdf

Bob


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## RogerS (8 Sep 2012)

Theory 1

Think about a light aircraft like a Piper Cub. Flies at, say, 125 knots. Seats 4. Think about the wing area. Visualise it.

Now think about a Jumbo. Flies at, say, 500 knots. So that's 4x the speed of the Piper. So that's 4 x 4 seats. = 16 seats. But a Jumbo can hold 480 passengers. So thats 30x the wing area needed compared to that of the Piper. Visualise it. Doesn't fit, does it?

So Theory 1 says that it is the belief of the passengers that it can fly. That's what keeps it up in the air.

Theory 2

The commonly held theory. Top of the wing is curved so the air has to go faster thus creating an area of low pressure above the wing which creates lift. If that is the case then why is it that aircraft with wings of a symmetrical cross-sectional area fly? Because they do.

Theory 3

It's all to do with the speed of the aircraft and the angle of the wing from the horizontal. It is the downward thrust of the air flowing beneath the wing that, following Newton's Law 3rd law, there is an equal thrust upwards and that is what keeps the plane in the air.


Personally I believe Theory 1.


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## Eric The Viking (8 Sep 2012)

Seriously, the "low pressure on top" thing has been discussed as a bit of a canard (ouch!) for a while now. 

Aircraft wings haven't had a 'bird's wing' cross section since the early days of flight* and the smart money seems to be on a different mechanism entirely, as most planes are fairly happy flying upside down, even if crew and passengers probably aren't. 

I've seen discussion of the air current from forward motion being reflected into downthrust, but that still doesn't explain inverted flight well. It makes most sense that wings work because of a number of different aerodynamic effects, and different ones dominate at different speeds, attitudes and air pressures. That's most certainly true of aircraft capable of speeds approaching and exceeding the sound barrier. Like many things, it looks simple but is in reality pretty complex.

You can't really use sailing boats as a complete analogy either, as an aircraft has no equivalent to a keel or centreboard/plate. In that instance though laminar flow is very important. Boats with foresails (jibs) perform better going towards the wind, i.e. getting 'lift,' than those with a single sail. The jib encourages laminar flow over the leeward side of the leading edge of the mainsail, considered to be more important than the extra 'lift' it creates on its own. It's also true that boats with streamlined masts, where the mast is aerodynamically shaped and faired into the leading edge of the mainsail, perform better to windward than boats with the same sail area but a simple, circular mast.

But I digress (typically!). I too am watching this thread with interest.

E.

*OK the bottom part of the wing was sometimes open in the early days (still is in microlights, many kites and hang gliders), but that wouldn't affect the bird's wing theory, apart from adding turbulence to the discussion. That said, I've got a couple of Flexifoil kites, which are self-inflating bird's wing designs, and the lift compared to traditional kites is phenomenal. In light winds, with the right spars installed, they're easily capable of flying with the lines beyond vertical, and two of them stacked (six-footers) can lift me off my feet.


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## Eric The Viking (8 Sep 2012)

RogerS":2jn021bo said:


> So Theory 1 says that it is the belief of the passengers that it can fly. That's what keeps it up in the air...
> ... Personally I believe Theory 1.



It's a good theory. After all, a very similar mechanism is keeping the British economy going (and more so the Euro), even as I type. ;-)


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## duncanh (8 Sep 2012)

Loads of stuff on the Nasa website including some interesting applets which simulate different wing profiles in air flows, including a rotating cylindrical wing and a ball.


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## Tom K (8 Sep 2012)

The truth is all aircraft have to have their wings left slightly loose. Combined with a slightly bumpy runway the oscillation induced allows your plane to mimic the humble sparrow thus taking us airborne. All other theories are hokum. (homer)


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## nev (8 Sep 2012)

I'll go with E's Pratchetesque theory, and extend the belief factor to multiplied by a % proportionately to the fewer people on board, or in the case of an unmanned craft, the person who's footing the bill


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## Jonzjob (8 Sep 2012)

All you have to do is to join the Royal Air Force and they will teach you the complete theory of flight like wot they did me 8) 

If you think of a glider, that's the easiest one cause it didn't got an engine unless it's a powered glider then it has, then it's never going up as far as the air around it is concerned, it's always going down, and the only time it will go up, when not being towed or winched, is when the surrounding air is going up faster than it is going down.

With me so far?

If you have a single engined aircraft,say like the Piper Cub Roger mentioned, the only reason it's got a fan on the front is to keep the driver cool. This is easy to see because if it stops when it's flying you can see the driver start to sweat profusely until he can start it again, then he cools down again.

If you are going to go flying with someone you don't know, like a big airline, then the best seat you can choose is the one directly above the 'black box', because it's designed to withstand all sorts of rough handling, vertical landings, etc., and if that's the only thing they want to retrieve then it's probably a good idea to be strapped to it :mrgreen: By the way, it's BRIGHT orange.. I used to have to service those in their early daze.

The theory that the air going over the top of the wing compaired tends to go out of the window when you havea symmetrical wing section come ça, third one down







Then, unless you point the front up the air has the same distance to go on either side. They are used on aircraft that fly upside down just as well as upside up and don't normally carry travelling passengers. They normally rely on brute force to get them into the air and can be quite fast.

The 747 and A380 don't have symmectrical section wings because if they did fly upside down 2 things would happen. 1. the drivers coffee would leak out of its cup and 2. all of the passengers would complain bitterly when they hit the roof, literally!

While we are talking flying. Does anyone know why the toiley windows are opaque? Who the hell's going to look in at 35,000 feet up? And just like trains, you aren't supposed to use them when you are on the ground..


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## Steve Maskery (8 Sep 2012)

John
But does you symmetrical wind fly when it is level like that? Surely it only flies when it is tilted up at the front? Or at least, tilted down at the back (ailerons, are they called?). In which case the pressure differential still holds.
S


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## RogerS (8 Sep 2012)

Steve Maskery":1ubbk3yf said:


> John
> But does you symmetrical wind fly when it is level like that? Surely it only flies when it is tilted up at the front? Or at least, tilted down at the back (ailerons, are they called?). In which case the pressure differential still holds.
> S



They require an angle of attack. It still isn't anything to do with pressure differential between top and bottom though.

The droopy things you are referring to are called 'flaps'. Flaps go down together (usually). When they are extended they let the aircraft slow down but still have enough lift to stay up in the air. That way the aircraft can land at a much slower speed. 

When they aren't able to extend the flaps (as sometimes happens) then you land really really fast. And then they keep you waiting at the end of the runway with lots of red lorries with flashing lights to see if your wheels are going to catch fire because the brakes got hot as a result of trying to brake a several hundred ton monster from hurtling off the end of the runway. And then when they finally let you taxi to the airport terminal, you find waiting for you another shiny red lorry with flashing lights....just in case the firemen in the other red lorries were asleep and failed to see the flames. DAMHIKT.

The waggly bits at the extreme end of the wings are the ailerons and when one goes up..the other goes down..


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## Jonzjob (8 Sep 2012)

It relies on a slight angle of attack and, normally, high speed. Ailerons are the movable controls at the ends of the wings normally and one moves up whilst the other moves down and they are used to start a turn. There are variations to that though. The ones on the trailing edge that normally only go down are flaps and they are used to produce more lift at slow speeds like take off or when fully lowered both lift and drag to help the aircraft in landing. In some cases both ailerons can be moved up and the flaps lowered, called 'crow breaking', and it's a very efficient way of slowing down without loosing control and stalling.

Then you can have things like flaperons, flap/aileron mix, elevons, elevator/aileron mix used on flying wings and ruddervators, rudder/elevator mix used on 'V' tails. Good 'ere 'init :mrgreen: 

The theory of flight is a fascinating subject and I really enjoyed it all those 52 years ago!! :shock: It still gets used because of my interest of RC gliders.

Edit : - Didn't see your reply Roger.. You're learning though ain't yer :mrgreen:


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## RogerS (8 Sep 2012)

Jonzjob":29ewci2t said:


> ......
> Edit : - Didn't see your reply Roger.. You're learning though ain't yer :mrgreen:



Cheeky pipper! I used to fly gliders.


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## Jonzjob (8 Sep 2012)

That's wot I said :mrgreen: Yer lernin in't yer.... =D> =D> 

Since when did glider guiders ever know about the theory :twisted: :twisted: 

This is one of mine






On this, the ailerons are so programmed so that on landing both of them can be moved upwards so as to spoil the lift. They still work as ailerons and if you want/need to turn left for instance the Starboard aileron goes down and the port wing drops because the Starboard wing now has a bit more lift than the Port jobbie.. There aren't any flaps or spoilers on it and before I programmed it to do this it was a very fast landing at times!! :shock: Wingspan 2.2 meters. Weight, just over 2 lbs..


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## Dibs-h (8 Sep 2012)

Wow - missed this! LOL! Reminds me of the past, when someone I know, asked the same question ages ago. In the end almost told him to turnip off as he was doing my head in. Not that this thread is going that way. LOL!

I always understood it to be - as a few have pointed out - due to the differential pressure between the top surface and the bottom surface generates the lift (pressure being force over area) and lift has to equal or exceed the gravitational effect.

Angle of attack, wing profiles - man that takes me back to my R\C days!

Dibs


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## RogerS (8 Sep 2012)

Dibs-h":31hgfy8y said:


> ....
> I always understood it to be - as a few have pointed out - due to the differential pressure between the top surface and the bottom surface generates the lift (pressure being force over area) and lift has to equal or exceed the gravitational effect.
> ......
> 
> Dibs



But it isn't!


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## Jonzjob (8 Sep 2012)

RogerS":2szbrj69 said:


> Dibs-h":2szbrj69 said:
> 
> 
> > ....
> ...



OK Einstien? Wot is it then??? :mrgreen:


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## mailee (8 Sep 2012)

Yeah, c'mon Roger tell us your theory. :?


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## mailee (8 Sep 2012)

Yeah, c'mon Roger tell us your theory. :?


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## newt (8 Sep 2012)

Wing Angle of attack relates to lift only while the airflow remains laminar, as the AofA increases and flow separates (becomes turbulent) wing begines to stall and lift reduces. To recover from the flow separation there are several options go faster, reduce AofA or change wing profile (flaps). Pressure difference still has some indirect influence, you will have seen water vapour forming above the wing on a fast jet in humid air also same effect on an F1 cars rear wing but upside down. What is for sure is the behaviour of wing dynamics is different between low speed flight, high speed (transonic) supersonic and hypersonic.


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## RogerS (9 Sep 2012)

What newt says !


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## Dibs-h (9 Sep 2012)

RogerS":2g1wevtc said:


> Dibs-h":2g1wevtc said:
> 
> 
> > ....
> ...



Rog

Sorry mate, have to disagree. I studied Mech Eng at Uni and Fluid Dynamics in particular and having an interest in R\C planes, you can be assured I made sure I studied this one matter at least. How a wing generates lift is explained by Bernoulli's theory.

Here's the quote - 

"In fluid dynamics, air is actually considered to be, and typically modeled as, a fluid. When modeling fluid movement, a scientist named Bernoulli discovered that a faster moving fluid has exerts less pressure than a slower moving fluid."

The exact page along with a Professor's (Cambridge Uni) explanation,

http://sciencebasedlife.wordpress.com/2 ... rate-lift/

Newt - the pressure differential has a direct bearing on Lift generation, not an indirect one.

Dibs


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## newt (9 Sep 2012)

Dibs-h":l44cwo5v said:


> RogerS":l44cwo5v said:
> 
> 
> > Dibs-h":l44cwo5v said:
> ...



Dibs what I should have said is that pressure difference has a secondary effect depending on type of aero foil and speed. I think the reason why the classical theory is being questioned is that there are significant differences in behaviour when you compare low subsonic with supersonic. No dispute with faster air producing lower pressure, just that it is not the only parameter involving lift.


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## RogerS (9 Sep 2012)

Dibs-h":345jvnwo said:


> RogerS":345jvnwo said:
> 
> 
> > Dibs-h":345jvnwo said:
> ...



So does a wing with a symmetrical cross-section work? :?


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## Dibs-h (9 Sep 2012)

RogerS":11o2f30d said:


> So does a wing with a symmetrical cross-section work? :?



A symmetrical aerofoil produces equal lift on both sides - so no net lift. For useful lift - there must be a positive angle of attack, in which case there is net lift.

Bernoulli's theory isn't the one size fits all - Newtons 1st and 3rd laws also apply.

Dibs

p.s. Rog - this might be useful, http://www.grc.nasa.gov/WWW/k-12/airplane/short.html section labelled lift. The following is interesting too - http://www.grc.nasa.gov/WWW/k-12/airplane/bernnew.html


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## Jonzjob (9 Sep 2012)

"So does a wing with a symmetrical cross-section work? "

It did on this







I used to live just down the road from a retired navigator on Lightnings. Very interesting bloke!!


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## AES (9 Sep 2012)

No it didn't Jonzjob - the Lightning (no Marks of that aeroplane - it's a Mk 6 in your pic) did NOT have a symmetrical wing section! 

The only full-size aeroplanes which do have "more or less" symmetrical wing sections are the specilaist aerobatic contest machines like the Yak, Extra, etc.

And BTW, sorry to spoil your fun but no Lightnings ever carried a Navigator - not in the RAF, the RSAF (Saudi Arabia), or the Kuwaiti Air Force. And the Thunder Bay Lightnings in South Africa (now grounded following a very unfortunate fatal accident) also never carried Navs. There were only 2 marks with 2 seats, the T4 and the T5. As the designation suggests, they were 2 seat trainers - all the rest were single seaters. I used to work on them for my sins!

I thought this thread started out as fun, and in the first page or so it was (I certainly got a laugh out of some of the posts anyway), but now there's been so much "serious tosh" posted that - being a boring old realist - I feel it necessary to dispell some myths.

Apart from the above specialist machines there are no aeroplanes that I can think of off hand which have truly symmetrical wing sections - close to it in parts (most airliners and other commercial aircraft) but not truly symmetrical. How do they fly? As someone said a page or two back, it all comes down to Bernouli a physicst (an Italian Swiss I think) who discovered that any fluid in a confined area (e.g. a pipe) will be forced to slow down when entering a constriction (e.g. a venturi). That slowing down creates an increase in pressure and that increase is directly proportional to the speed reduction. This works for all fluids and by definition, air is a fluid - but unlike other fluids (e.g. oil, water, etc) air is compressible. That's what makes aeroplane aerodynamics so ivery nteresting, especially when dealing with modern swept-wing aeroplanes like airliners.

A wing section is, in effect, just a venturi turned "upside down" (i.e. the top of the venturi becomes the bottom of the wing and the bottom becomes the top of the wing) so it's a "venturi in reverse".

As Steve Maskery said a page or two back, aeroplanes with symmetrical or near symmetrical wings ALWAYS have the centre line of the wing rigged at a positive angle of incidence (i.e. the Leading Edge of the wing is set a couple of degrees nose up).

How the aeroplane maintains level flight in those conditions is a function of the trim setting which has the effect of either increasing or reducing that angle of incidence. On modern aeroplanes this is done by changing the angle of incidence of the tailplane (or in American, the horizontal stabilzer), and/or by means of adjustable tabs on the trailing edge of the tailplane. On modern commercial aircraft the tailplane also has realatively small "flaps" at the back of the tailplane and these are called elevators. These are what makes the aeroplane climb and dive (when "Capt Speaking" or the Autopilot pulls or pushes on the control column).

Ailerons are smallish tabs on the trailing edge of the wings and when one goes up the other goes down. The upgoing aileron reduces the amount of lift being produced on that wing (and the down-going aileron increases the lift) so that there's an imbalance between the lift produced by each wing, resulting in the aeroplane rolling towards the wing with less lift. That continues until the forces are balanced out again - i.e. the pilot/Autopilot removes the roll input and/or the aeroplane becomes stabilised at the required angle of bank. The upgoing aileron is always moved to a lesser angle than the down-going aileron and in addition, the basic angle of incidence ofthe wing is "washed out" as you move along the wing towards the wingtip. This is to prevent/reduce the tendency to tip-stall - i.e. what was laminar flow over the wing becomes broken up because the inner wing is going slower than the outer wing. Think of all those Hollywood musicals with the long lines of high-kicking dancing girls - the one on the uinside of the line virtually prances on the spot while the one on the outside iof the line is going like stink. It's just like on your models Jonzjob.

Many aircraft have their ailerons set to "droop"by a few degrees when landing and this reduces the runway length required (i.e. it increases the amount of lift produced by the wing) although the ailerons do continue their up and down roll role (sorry!) but set around their new drooped datum. Commercial aeroplanes I can think of with such features include the Pilatus Porter, the Airbus A320 (if I remember correctly - I did that Course a long while back!) and definitely the MD-11. There are certainly others.

On some aircraft there are more than one aileron on each wing, located fairly well inboard and a second one right out near the wingtips. And some aircraft don't have any ailerons on the outboard on the wingtip at all - the Airbus A310 springs to mind.

Flaps are of two basic types. Those on the Trailing Edge of the wings normally move outwards first (i.e. along the wing section centre line) and only then do they "droop" to certain pre-set angles. The purpose is to increase the lift from the wing first be increasing its area and then by increasing its camber (curvature).

There are also usually "flaps" on the Leading Edge of the wings (normally called "Slats") and they are almost always coupled to the Flaps control. They also increase the camber of the wing, again to increase the amount of lift produced. The only aircraft I can think of off hand which had separate Slats and Flaps controls was the Hawker Siddeley Trident and that "peculiar" feature led to a well-known fatal accident on Take-off at Heathrow when "Capt Speaking" neglected to lower the LE Slats.

That's a pretty old aeroplane and I can't think of any of the more modern types which have such separate controls. For example the Boeing 737 project which I'm working on now has TE Flaps position 2 degrees (which also lowers the LE Slats by 1 degree); Flaps 5 degrees (Slats 2 degrees); Flaps 15 degrees (no more LE Slat movement); Flaps 25 degrees; and finally, Flaps 40 degrees. To continue with that example, these clever bits give a wing which is capable of flying about 160 pax, their bags and all the fuel needed for say a 1,800 miles journey at probably 500 mph in cruise. But at the same time that wing will lift the same load off the ground (and lower it back down again) at take-off and landing speeds of about 160 mph.

If anyone wants to know more about the basic principles of venturis (which is what we're talking about here) then I recommend a visit to the site of Mathias Wandel at http://woodgears.ca/index.html.

Look up his experiments on various aspects of venturis (inc a video dealing with all sorts of interesting stuff including spray guns, flame-trowers, and sucking up dust). Nothing on wings, but as said, exactly the same principles apply. And the video should help you to visualise some of the stuff I've been spouting here.

Last but not least, anyone want to try this very simple experiment? Take an ordinary piece of paper (A4 will be fine), hold the paper at the 2 corners of the narrow side. Raise your hands (with the paper) up to your lips (the paper will of course be drooping downwards) and then blow gently over the top surface of the paper. The harder you blow the more the paper will raise up until it's almost sticking out from your mouth horizontally (but still with a curvature ("camber"). And NOT a puff of your blown air went underneath the paper!

One last point to the poster talking about Piper Cubs earlier (LOVELY little aeroplane ;-) ). It's a 2 not a 4 seater, and I very much doubt you could get it to fly at the speeds you quoted (and if you did you'd tear the wings off it!). About 90 mph flat out is more like it.

Sorry if I'm just a boring old spoil-sport - IMHO what started off as a fun post just got silly with many just plain wrong "facts", hence the realism injection.

With respect to all

AES


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## Jonzjob (9 Sep 2012)

I could well stand corrected on the wing section of the Lightning, but my friend and neighbour WAS a nav on Lightnings. He was stationed at Farnborough for several years and it was when they were doing the speed trials on them. 

His job was mainly to make sure that while they were doing the supresonic trials over Le Manche, the Channel, that they didn't overrun the coast. But he aslo had to guide the driver to the correct start point for the trials. At the speed they were traveling by the time the driver saw the coast they were going to cross it supersonic and the R.A.F. didn't like all the claims for broken glass. 

Sorry, but I knew someone would bite :twisted: :twisted: :twisted: 

He was also a nav on theShackelton that was used to test the Concord break chutes. They would stagger up to 30,000 feet, dive until the speed reached something around 300 mph plus and then deploy the chute! After a few seconds it ws jettisoned and by the finish of the tests the airframe was about a foot longer than when they started. Not one of his favorite jobs. I worked on Mk2 Phase 2 taildragger Shacks in Changi Singapore for a while. The last taildraggers in the R.A.F. Lovely aircraft!!


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## newt (9 Sep 2012)

AES":36iwn75v said:


> .
> 
> Apart from the above specialist machines there are no aeroplanes that I can think of off hand which have truly symmetrical wing sections - close to it in parts (most airliners and other commercial aircraft) but not truly symmetrical. How do they fly? As someone said a page or two back, it all comes down to Bernouli a physicst (an Italian Swiss I think) who discovered that any fluid in a confined area (e.g. a pipe) will be forced to slow down when entering a constriction (e.g. a venturi). That slowing down creates an increase in pressure and that increase is directly proportional to the speed reduction. This works for all fluids and by definition, air is a fluid - but unlike other fluids (e.g. oil, water, etc) air is compressible. That's what makes aeroplane aerodynamics so ivery nteresting, especially when dealing with modern swept-wing aeroplanes like airliners.
> 
> ...



I think you will find ,and there was a link earlier, that the Bernoulli effect is only part of the lift parameter.


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## Jonzjob (9 Sep 2012)

For us thickies wot didn't know Bernoulli, here's a bit

http://www.youtube.com/watch?v=olVJzVadiFs


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## AES (10 Sep 2012)

@newt

Agreed, Bernouli is only a part (but the main part) of the story. Aerodynamics is a BIG, but fascinating subject, especially if we start to talk about modern aeroplanes which can fly from, typically, about 150 mph up to 500-ish mph (about 0.9 the speed of sound).

As it happens I'm in an aircraft hangar in TRurkey right now and (amongst others) there's an Airbus A310 with various wing bits & pieces deployed and removed right outside my office window. IF anyone is interested I can post a couple of pix illustrating some the stuff I was spouting about yesterday - BUT ONLY anyone isinterested enough to request ;-)

AES


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## Jonzjob (10 Sep 2012)

I'm interested in seeing them A :mrgreen: :mrgreen:


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## AES (10 Sep 2012)

OK Jonzjob, tomorrow.

AES


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## Jonzjob (10 Sep 2012)

Ta very muchly.. I look forward to seeing them. The last aircraft I worked on were VC10s and Belfasts in the early 70s at Brize Norton for 5 years. The 10 is a lovely aircraft, but the Belslug was a real camel, designed by a comitte who knew nowt about aircraft!!


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## newt (10 Sep 2012)

Jonzjob":z03mn89s said:


> Ta very muchly.. I look forward to seeing them. The last aircraft I worked on were VC10s and Belfasts in the early 70s at Brize Norton for 5 years. The 10 is a lovely aircraft, but the Belslug was a real camel, designed by a comitte who knew nowt about aircraft!!



The super VC10 was and still is a brilliant aircraft having been fortunate to have flown many hours in both passenger and tanker variants. At one stage they were going to be re-engined and refurbished, and there was talk that Boeing wanted to buy up all the airframes, if true I can only assume to eliminate competition. The wing main spar did have to have some repairs carried out, but it was a very efficient design, I think the wing may have been super critical, although I am not sure. When they were first introduced it was the only jet that could operate hot / high in Africa.


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## RogerS (10 Sep 2012)

AES":5iji8iiw said:


> @newt
> 
> Agreed, Bernouli is only a part (but the main part) of the story. Aerodynamics is a BIG, but fascinating subject, especially if we start to talk about modern aeroplanes which can fly from, typically, about 150 mph up to 500-ish mph (about 0.9 the speed of sound).
> 
> ...



Most definitely, yes please, and many thanks for your contribution. Always willing to learn.


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## CHJ (10 Sep 2012)

Great contribution AES, been around aircraft all my working life, servicing, modifying them for research and major rebuilds, still can't get my head round the fact that a bit of wind can lift so many tons of assorted metal, nuts and bolts etc. into the air. (until a door slams that is)

All we want now is someone to come along and explain how a jet engine transfers the thousands of pounds of thrust to the airframe via individual components that could hardly stand a good car crash, including in most instances the couple of main support couplings usually no more than 15-20 mm dia.

Bit like the dis-belief when fitting a helicopter rotor head and its attendant operating linkages that are about a twentieth the diam of the tow hook on the back of a Car, does not get any easier to accept either when you try and install a heavy load under the chopper fuselage and have to take into account how much the cabin will distort so that it does not squash against the console you are about to fit inside.


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## AES (10 Sep 2012)

@CHJ:

Thanks for the comment - I wasn't sure whether to write it or not (but being a Sunday and away from home I had the time). I didn't mean to pee anyone off - personally I thought the explanation about bolting the wings on loosely so that they flap as the aeroplane moves along the runway was FAR more amusing than my efforts ;-) And the one about the fan in front stopping so that the pilot starts sweating was a good one too. 

Helicopters, ahhhh. I'm happy to say that I've never had all that much to do with them (IMHO the only machine known to man that needs to screw itself up to 106% of max power just to get off the ground)! Nasty, noisy, vibrating things! And their engines are even worse than fixed-wing aeroengines.

To whoever posted about the VC10, I do believe you're right, I'm pretty sure it was the first commercial aeroplane with a super-critical wing section (i.e. a reflex under-curvature towards the TE). Lovely aeroplane from the pax viewpoint (flown in them several times), and well-powered thrust-wise too, so nice performance (especially the Super VC10). But I've never worked on them myself and from what I've heard from an ex-BOAC colleagues, a PITA to work on, and not very economical either - typical of so many British aeroplanes unfortunately.

Anyway, some A310 etc pix coming tomorrow as promised.

Krgds
AES


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## CHJ (10 Sep 2012)

AES":362942g5 said:


> .VC10.... a PITA to work on, and not very economical either .AES



Ironical that they would have a second life as a tanker support being such a gas guzzler.
Last one I had any involvment with was XX914 at the Royal Aircraft Establishment at Bedford.

Lightning: The T4 and T5 were two-seater trainer versions and were based upon the F.1A variant, think there is a T4 at cranfield. A favourite platform for reasearch projects if you could find a spare one.
Don't think it really needed wings as such, always seemed to be more like a guided engine to me.


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## RogerS (10 Sep 2012)

My favourite factual story about the Lightning (can't remember which book it was in) was regarding a senior ground engineer who was investigating poor thrust. There were all sorts of restrictions regarding taxiing under full thrust for obvious reasons but for some reason (the exact details escape me) but said engineer found himself hurtling down the runway and up to take-off speed....which is exactly what he had to do otherwise the plane would have ploughed into some buildings at the end of the runway. No helmet. Ejector seat disabled. Fortunately at the time ground crew were given very rudimentary flying lessons and so he had the basics and managed to land it after a few attempts!


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## mailee (10 Sep 2012)

Very interesting thread this, I am learning a ton of information. BUT! don't get into jet turbines....those things are alchemy! :shock: I understand the basic principle but how they work???? Oh one question though, why do airliners have two ailerons on each wing? :?


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## AES (10 Sep 2012)

@RogerS:

Yup, it's a true story. If I remember rightly (though I can be correted) it was at Lyneham in Wiltshire which although mainly a Transport Command station at thje time was also an MU (RAF "Maintenence Unit" used for Heavy Maintenence Visits - i.e. "deep" servicing).

If you're interested in the "Frightening", which Jonzjob obviously is, then there is a good website at: http://www.aviation-picture-hangar.co.uk/Lightning.html

That's one of several sites and it includes the "non-pilot" pilotted Frightening story. For Jonzjob: that site (and others linked to it) will also show you what the wing section of that aeroplane really looked like. Also Jonzjob, if you can find a copy of the November 1964 "Aeromodeller" mag it was well drawn there too (Cox was the artist I believe), though I stand to be corrected on that).

Krgds
AES


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## RogerS (10 Sep 2012)

Continuing the aviation theme, there have been a few excellent TV programmes recently. One was from the Engineering Giants series and featured the almost complete strip-down of a BA Jumbo as part of the 5/6 year maintenance cycle. Fascinating programme. And then the two-part series on Jets...part 1 was all about our fighter aircraft etc post-war and part 2 - commercial jets. Featured the author of an excellent book 'Empire of the Skies'. WE really had some talented engineers and designers then (well, we still do) and an amazingly fertile aviation industry. I'll never forgive Wilson cancelling TSR2. And that miserable eejit from Cambridge (now dead) who took it upon himself to go round the world telling countries about how bad the sonic boom of Concorde would be.....turnip...traitor!


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## AES (10 Sep 2012)

@mailee:

Not all aeroplanes (airliners) have two ailerons on each wing - please wait until tomorrow's pix (I do hope they haven't moved the A310 overnight)!

And to add to the "mysteries" of roll control, modern aircraft have both Spoilers and Speed Brakes on the upper surfaces of the wings. And in high speed cruise flight the Spoilers often "float" to assist the ailerons with the roll control. "My" Boeing 737 is a typical example (as are all B737s) and you should see the "Heath Robinson" mechanical mixers on the B737 - hiding in the RH Main Landing Gear Bay, which, with a series of "strings, pulleys and bellcranks", "mix" the amount of Spoiler movement of the "real" ailerons according to the speed of the aeroplane). But still, IMHO, it's better than the "plastic fantastic Scarebus" with it's multiude of invisible electrons wizzing silently along bits of wire - can you tell that I'm a mechanical bloke and not an avionics "fairy" at heart can't you?

Perhaps we'll get to gas turbines at a later date (not this trip from me though), although Bernoullui will stand you in good stead understanding those too.

Try that web link I posted yesterday.

Krgds
AES


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## mailee (10 Sep 2012)

Thanks AES. It is indeed an interesting subject. I am assuming that the larger inboard ailerons are used at slower speeds and the outer ones at high speeds? All of my knowledge of aeronautics comes from flying model aeroplanes so I am no expert but find it an interesting subject. I do agree with you about the fly by wire though as anything mechanical is fine until you computerise it and then the trouble starts. :roll:


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## Jonzjob (10 Sep 2012)

There have been several replies since I started doing this earlier, so I hope that I'm not redoing too much here..

Mailee, there are indeed high and low speed ailerons, but the low speed ones are on the wing tips where they have most leverage and are most effective at low speed with the hugh speed ones almost like barn doors further towards the wing roots. Unless you go to things like the B52 which doesn't have ailerons as such. It has 'spoilers' on the wing tips which are panels in the upper face of the wing tips that lift into the airflow and literally spoil the lift there causing that wing to drop. It will also have the effect of stopping 'adverse yaw', oh hell, what have I started now!! where with normal ailerons the down going one causes more drag as well as pushing the wing up. This causes the tip to be pulled backwards and makes the plane yaw (turn in the horizontal plane) in the opposite way to the way the aircraft is trying to turn. That causes lots of drag on the whole aircraft apart from making the turn very tatty!

33 MU R.A.F. Lyneham used to do the major servicing on Lightnings in the 60s/70s. One of the problems was that if you put the 2 RR Avons into reheat the breaks were not man enough to hold it so after the Major servicing they were taxied out onto runway, normally by a qualified driver/pilot. On the occasion you refer to the aircraft was wanted toot-sweet so a Winco pilot who was qualified on Lightnings, but hadn't flown one for quite a while, volountered to do the test. He took it out onto the runway, no canopy, wooden dining type chair to sit on and opened it up. There was a problem and it wouldn't come out of reheat so he had two choices, either to lift off or to plough through the woods in the valley at the end of the runway. He took of, did a circuit, managed to stop the reheat and landed safely. He was given a sevear repremand and a comendation. He was also said to have gone gray haired in that one flight!!! I can't remember the exact date but it was somewhere around 1965 while I was stationed there..

I have no idea why anyone, especially an electrician, would find a VC10 difficult to work on? They probably never worked on Britannias or Balfasts? :mrgreen: I throughly enjoyed my 5 years on them both with a spanner in hand and flying in them. The original R.A.F. 10s were a cross between the normal and super 10s with normal fuz with an aluminium floor and big freight door, super wings, engines and tail with the fuel tank in the fin. They also had reverse on all 4 engines. We lost one of ours to Boscome Down for the RB211 engine tests. It had the RB211 on the Starboard side and flew quite happily on just that one engine. On one of the tests they opened the 211 up to full power and actually bent the engine mounts slightly. They only did that once.

If the VC10 had been allowed to be developed it probably have had 2 RB211s and been wide bodied. The same goes for Concord Mk2 as shown in the model that's held at the Bristol Aero Museum, Kemble. They were both before the event of bypass engines and were very sucessful and so were killed!

This is the model and not a Concordsky












Sorry about the photo quality, but go and have a look for yourselves..


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## CHJ (10 Sep 2012)

I think the museum is in Bldg 150 (hangar) my old main workshop, the only building I've ever had to manage that had power sources from two different grid supplies to meet the power load should we loose one areas grid whilst in the middle of critical heat treatment or autoclave programs.
Must visit one of the days, it's 18 yrs since I last entered it, could not bring myself to walk over there the couple of times I've nipped over to the steam fair or air days.


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## AES (11 Sep 2012)

Well Ladies & Gents,

If any of you have been waiting all agog for some aeroplane pix this mrning I'm afraid I'm going to have to disappoint you.

NO, they didn't move the aeroplanes overnight; and YES, I've got what I think will be some quite nice pix in the camnera right now. BUT, being a dozy old so-and-so now and then, AES has not got the special USB/mini USB lead here, so he can't download the pix off the camera onto the laptop so that he can upload them here.

Very sorry - I'll get the pix up here within the next few days (as soon as I can get my a**e into gear).

Krgds
AES

P.S. Didn't know about the Museum at Kemble. Must try and go there sometime.

P.S.S. I really don't know about the VC10 myself, and my (2 colleagues actually) who did work on them (and not leccys by trade BTW) did tell me they were a PITA. They were probably comparing them mainly with Mr. Boeing's aeroplanes (B707 and on) which although can be a bit of a pain at times are/were generally much better for servicing and access and economy than British aeroplanes. I can confirm that generalisation from my own experience too (e.g. BAC 1-11, BAe 146/RJ).

Cheers


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## Peter T (11 Sep 2012)

Unfortunately, being a high bypass turbofan, the RB211, or any of it's more modern counterparts, would not work at supersonic speeds.

This was always a problem for Concorde. It had to use noisy, relatively inefficient military engines. Even these engines cannot work with inlet air at supersonic speeds. The air intakes are designed to slow the air to subsonic speeds before it reaches the compressor.

Don't get me wrong, I'm a big Concorde fan and was saddened when it was withdrawn from service, particularly as I never got the chance to fly on one!


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## bugbear (11 Sep 2012)

Peter T":3gndypp9 said:


> Unfortunately, being a high bypass turbofan, the RB211, or any of it's more modern counterparts, would not work at supersonic speeds.
> 
> This was always a problem for Concorde. It had to use noisy, relatively inefficient military engines. Even these engines cannot work with inlet air at supersonic speeds. The air intakes are designed to slow the air to subsonic speeds before it reaches the compressor.
> 
> Don't get me wrong, I'm a big Concorde fan and was saddened when it was withdrawn from service, particularly as I never got the chance to fly on one!



It just proves that all sophisticated engineering is a big exercise in robbing Peter to pay Paul, which involves rather subtle skill and judgement.

BugBear


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## Jonzjob (11 Sep 2012)

I'm not sure about the building number Chas, but I did get a HUGE b00l0king for digging a trench and laying a power line from the far corner of it across to where XM496, Britannia, was parked about 150 yards away. I went across a corner of the old Roman road that runs through the airfield!! The fact that the peri track and the runway cut huge great chunks out of it seem to have gone un-noticed :mrgreen: When I pionted that out to the person yelling at me he went quiet! .!

This was the very last flying Britannia and I finished up as th eleky on it for yet another 4 years. It was one of the R.A.F. fleet at Lyneham http://www.xm496.com . It is still the only 'live' Brit in the world. There are others around, but none have all of their Bristol Protius engines let alone all in running condition.

Sorry if I gave the impression of the RB211 and Concord, but there was an engine on the drawing board for the Concord II . What with Boeing yelling that nobody ever wanted to fly supersonic, that is while they couldn't match it, but now they are using Concordski to try to do just that along with their new attempt with the hypersonic jobbie using ram jets.. They don't mind supersonic air coming at them..


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## CHJ (11 Sep 2012)

Jonzjob":2zd5590r said:


> I'm not sure about the building number Chas, but I did get a HUGE b00l0king for digging a trench and laying a power line from the far corner of it across to where XM496, Britannia, was parked about 150 yards away. I went across a corner of the old Roman road that runs through the airfield!! ...



I don't doubt you got in trouble for that, the Foss Way that does indeed run right alongside bldg 150 is a protected site, being one of only a few sections of the Roman road that still contains the original construction details. For many years it was still designated a public right of way for pedestrians that air traffic had to manage across the runways.


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## Jonzjob (11 Sep 2012)

That's XM496 just off the western corner of the hanger and I had the trench cut almost in a straight lint to the tail of the Brit and believe me I did get a rollocking for it. Not that I was too worried, you can't sack slaves you have to sell 'em.

A bit closer look. 






It's been moved again since I've been over here and it now resides over the other side of the runway, I think, on the ole Red Arrows flight line? There somewhere? Working on that didn't arf bring back some memories


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## Jonzjob (11 Sep 2012)

I've just found this link. Fantastic and well worth the watch. A good demo of elevons too :mrgreen: 

http://www.youtube.com/watch?v=TbaQo6nM ... ure=relmfu


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## RogerS (12 Sep 2012)

What a shame. Kemble is now closed to the public. Wonder what the sponsors think?


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## Jonzjob (12 Sep 2012)

AES":yk49i2xe said:


> @mailee:
> 
> Not all aeroplanes (airliners) have two ailerons on each wing - please wait until tomorrow's pix (I do hope they haven't moved the A310 overnight)!
> 
> ...



A, I have just reread this post and realised that you would have LOVED the Britannia and its controll systems. 

There were NO power controls on the aircraft. All of the control surface were 'free floating'. When it stood at the end of the runway, waiting for clearence for takeoff the ailerons and elevators were drooped, i.e. hanging fully down, and the rudder was blowing free in the wind! The control surfaces only had any authority when, rudder, 90 knots, elevators and ailerons about 110 knots and then they would come into line. They were totally free to move and the only thing that moved them in flight was a 5 or 6" servo tab along the trailing edge of those control surfaces. The tabs were moved with a series of 6 foot or so 'torque tubes' with universal connectors in line and the servo tubes went from the control coloumb to those control surfaces. The elevators were so sensitive that they had to had a 'feel simulator' to give the driver a sense of how much up/down he was putting in (no females in those daze). 

It was a very sucessful system and there were several occasions where our Brits were leaving USAF bases and the tower would send an emergency message to stop the aircraft because the ailerons had failed and were both down! The normal response was "No problem, we have learned to fly with them like that :twisted: :twisted: "

Mailee, if you are worried about jet engines then you will love the `Bristol Proteus" because the air goes in the front, going backwards, then turns through 180º and goes backwards through the 12 stage compressor. Then it turns through another 180º and goes through the cans (the bit where it catches fire!), through the double turbine twin stage turbine and produces about 5,000 lbs thrust. 

The double twin stage turbine? The first 2 rows of turbine blades are connected to the compressor and turn the 'jet' bit of the engine. The second 2 rows of turbine blade are connected through the centre of the main engine shaft to the proplellor gear box and turn the 16 foot prop. You with me so far??

The genral outcome is that you have a jet engine that is about the same length as an 'infernal conbustion engine' that runs on rough parafin (carasine (avtur), normal jet fuel) and is much more efficient at medium/ low altitudes than a pure jet 'cause it's got the big windmills on the front.


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## Jonzjob (12 Sep 2012)

Just found this for any interested parties

http://www.bristolaero.com


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## newt (13 Sep 2012)

Again lucky enough with my work at Boscombe Down to have flown in the Britannia, we used it as communication aircraft for a long time.


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## CHJ (13 Sep 2012)

newt":qw5b7ztw said:


> Again lucky enough with my work at Boscombe Down to have flown in the Britannia, we used it as communication aircraft for a long time.



My main hacking was done in the old Devons between establishments usually on a weekly basis, bit unnerving some of the time at the beginning as I was trying to sort out the mod program to upgrade the engines because they were not one engine capable with a full load on board.

Rest of the time flying in such as Vicounts, Varsitys, BAC 1-11 etc. was just work when something needed tweaking in flight.

Once had the pleasure of flying back from Kinloss in one of BD's Hastings sitting on the floor with a load of gear strapped around us, low level down Loch Ness and over to Belfast to drop a boffin off on route. Our Hastings had too much gear installed in fuselage to act as transports. 
I think the Beverley that came to collect us and kit from southern Germany in the late 60's also was a BD kite. Created quite a stir when it backed up the taxiway between two hangars for us to load up.
Interesting flying over the Rhine with no back doors fitted looking down at the shipping whilst checking the tethering on the landrover and GPU's etc. stowed on the deck.


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## newt (13 Sep 2012)

The Varsity had Dutch Roll and trying to have a pee in the toilet at the back end was quite a challenge, some were taken out of service with corrosion at the rear bulkhead. Spent 42 years at Boscombe one of the highlights being involved with the trans Atlantic air race with the 2 Harriers, interesting story to that. Couple of periods in the US during that time. Happy to talk aircraft all day, but I guess to many it would be boring.


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## CHJ (13 Sep 2012)

Many years ago there was a joke going the rounds about an Aircraft design that kept crashing because the wings broke off.
The answer was apparently supplied by a local building contractor who originated from a little isle off the west coast of England who said they should drill a row of holes across the wing.
When asked what the blazes that would do to improve things he said, “well a bog roll never tears along the dotted line does it”

Ironically within a couple of months we were cutting a 1/8” slot right over the upper wing surface near the root of the wing on the Viscounts to stop the wing flex cracking the pressurised fuselage.

A memory brought back by the flapping wing comment earlier in the thread.


Same problem did not affect the Varsity, although looking an older concept it was actually a newer design than the Viscount and had a more flexible wing/fuselage interface.


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## Jonzjob (13 Sep 2012)

The Beverley had an interesting situation with the toilets. They were in the very rear of the boom and directly in front of them was the para drop hatch. The paras that were in the boom had a crew member who opened the hatch so they could jump from there without having to go down to the main fuslarge, BUT if you were working on the aircraft on the deck and went into the toilet and someone opened that hatch you wouldn't be the first to go A over T through it and onto the pan below. A few blokes were badly injured by just that. So a mod was introduced that when the hatch was opened it put a pin up so the loo doors couldn't be opened! You had to be very trusting of your mates if you used the loo after that and a favourite was to wait till someone went in, open the hatch and walk away :twisted: :twisted: 

I have flown in them but never worked on them..

The nick name for both the Varsity and the Valetta was 'the pig' because that's what they looked like. 

You would never have flown in a Belfast with the rear dors open Chas. They were designed for heavy drops and were supposed to be able to take off with a light fuel load and heavy freight load and in flight refuel. When they did the refueling testing at Boscombe Down they found that unless you got the basket first try it hit the bow wave and flicked upwards. Then came back down and smashed into the cockpit roof. Basically the probe was too short and it was as long as it could be made without breaking! So in flight refueling was scrapped. They then went to air dropping and the first time they dropped the rear doors it almost fell out of the sky. It became too unstable to fly! So that was scrapped too. I did have 6 nice comfortable bunks in a nice cabin under the cockpit though so that 2 crews could be carried.

You got it. They took off and could fly around the world non stop with in flight refueling :mrgreen: :mrgreen: Quiet night shifts and I can assure you they were very good!


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## Benchwayze (13 Sep 2012)

Folks,

Take a sheet of A4 paper by its bottom corners, and let the sheet drape over your hands, away from you. 
Keeping hold of the paper, blow gently over the front edge and you will see how/why an aircraft flies. 
That's how it was demonstrated to me. 


:wink:


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## CHJ (13 Sep 2012)

Benchwayze":3r7gsm32 said:


> Folks,
> 
> Take a sheet of A4 paper by its bottom corners, and let the sheet drape over your hands, away from you.
> Keeping hold of the paper, blow gently over the front edge and you will see how/why an aircraft flies.
> ...





AES":3r7gsm32 said:


> ..............Last but not least, anyone want to try this very simple experiment? Take an ordinary piece of paper (A4 will be fine), hold the paper at the 2 corners of the narrow side. Raise your hands (with the paper) up to your lips (the paper will of course be drooping downwards) and then blow gently over the top surface of the paper. The harder you blow the more the paper will raise up until it's almost sticking out from your mouth horizontally (but still with a curvature ("camber"). And NOT a puff of your blown air went underneath the paper!.....AES


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## mailee (13 Sep 2012)

Thanks John, but you lost me at the air goes in backwards???? I can get my head around a piston engine but a jet turbine just seems to defy logic! :? Surely it's perpetual motion machine? and where is the starter motor? Somehow it starts and draws air in at the front where it goes through a few fan blades and gets compressed, then fuel is injected and it expands and drives another fan that drives the front fans again ad infinitum!? And how does the throttle work? I tell you it's scary stuff and more like alchemy. :shock:


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## CHJ (13 Sep 2012)

It's only a few components built around a primus stove on steroids.

It just manages to better the four stroke engine by doing induction, compression, ignition, exhaust all at the same time in a single cylinder.


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## Jonzjob (13 Sep 2012)

Mailee, it's just a fan assisted blowlamp mate! Nothing complicated, honnest. 

The Proteus just reversed the air flow through the 12 stage compressor and then again so that when it went through the cans, the bit that's the blow lamp, the hot gasses were shot out of the back both driving the turbines for the prop gear box and the compressor and then shoving about 5,000 lbs of jet thrust out of the back..

The Proteus wasn't just used on the Britannia. It is still, as far as I know, used on some of the RNs fast patrol boats and there were 4 powering the big cross Channel car carrying hovercraft. Even some in frigates as well. Very versatile bit of kit!

Still just a blowlamp though :mrgreen: 

Posts crossed Chas..

Edit : - Nearly forgot.. It also powered the Bluebird to be the worlds fastes wheel driven car and I think that it still holds that record. Pure jet 'projectiles' have gone faster but the are just blown along and not driven by the wheels ..


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## Peter T (13 Sep 2012)

mailee":2lonv2z5 said:


> Thanks John, but you lost me at the air goes in backwards???? I can get my head around a piston engine but a jet turbine just seems to defy logic! :? Surely it's perpetual motion machine? and where is the starter motor? Somehow it starts and draws air in at the front where it goes through a few fan blades and gets compressed, then fuel is injected and it expands and drives another fan that drives the front fans again ad infinitum!? And how does the throttle work? I tell you it's scary stuff and more like alchemy. :shock:



If you're having problems with that, you might want to consider something else.

In the hot parts of the engine, the combustor and the first stage turbine, the temperature of the combustion gasses passing through is typically 200 to 300 degrees C higher than the melting temperature of the metals that the engine is made of!

To prevent catastrophic meltdown, the components are peppered with thousands of small cooling holes through which "cool" air is fed to provide a laminar flow of cool air to protect the metals. This, in conjunction with high temperature ceramic coatings, prevent anything nasty happening!!


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## mailee (13 Sep 2012)

I do know about the heat inside one of those and the ceramic coating and drilling due to being an avid watcher of the discovery channel. i was engrossed in the documentary about building the Rolls Royce Trent engine but still find it hard to understand how it actually works! i think a fan assisted blow lamp is understating it a bit though. :lol: I take it that the reverse flow engine is the same design as the Frank Whittle original as that seemed to have 'cans' surrounding the engine? But how is a jet turbine started and why doesn't the starter get melted? I also assume the throttle works by injecting more fuel into the combustion chamber? Also the combustion chamber is open to the elements with only fans separating it from the outside? I assume it can't escape to the front due to the incoming air so escapes to the rear driving the fan. Got to admit it's a damn expensive blow lamp. :lol: Thanks for the info guys it is certainly an interesting thread.


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## CHJ (14 Sep 2012)

The starter motors are outside the main engine system.
Either a powered turbine on the front as in the cartridge powered RR Avons or via a side mounted gearbox via a bevel gear off the main compressor shaft.
Just as you take off power for generators/alternator, hydraulic pumps cabin pressure compressors etc. you can induce power the other way with a starter motor.


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## Benchwayze (14 Sep 2012)

Seems my post was redundant. 
I'll just learn to read the threads more thoroughly I guess! 
So much for speed-reading. That's another book I think I will throw away. 

MAILEE,

I know this is a change of thread, but just to give you something else to think about... 


How does a torpedo internal combustion engine operate underwater? :lol: :lol: :lol:


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## Jonzjob (14 Sep 2012)

Read this M and you'll be as wise as me http://www.leitemlane.com/jetoperation.htm

Mind you, that ain't difficult, but I'm quite cleaver when I get me brain cell wound up :? :? 

You can see why they are called cans too!


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## Jonzjob (14 Sep 2012)

John, your post wasn't redundant at all!! And yes the acceleration is done by throwing more fuel at it and if you really want to make it look like a blow lamp then you can inject even more fuel into the jet pipe, the tube after the turbine blades and immediately before the end of the engine. It then ignites and gives anything up to about 40% more grunt and big butch flames out of the back! That's why Concord was a bit noisy on takeoff..

Torpedoes. Their infernal combustion engines use the same type of fuel as rockets and Avpin. A mono-fuel that makes its own oxygen. Others use electric motors.. One type the Germans used in WW2 was a seeking type and if it missed the target on the way through it would turn and find a target. Sometimes it found the sub that fired it (hammer) (hammer) :mrgreen:


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## Jonzjob (14 Sep 2012)

The 'V' bombers were air started and all 4 donks could be started at once. You also have the Avpin starter too. That uses a mono-fuel, Iso propyl nitrate, It makes it's own oxygen. This is quite an amusing story about it http://rhodesianforces.org/No1sqnavpin.html

Also used on Lightenings and some marks of Canberras :shock: :shock:

Edit : - Avpin was also used on the later marks of the 'Grovellin', or Javilin as it was offically called. Here is an excerpt from a Javilin web site about both the cartridge start and the Avpin jobs. As a matter of interest, the Jav driver and nav didn't strap themselves in untill both engines were started and as there were a Javilin squadron just uo the flight line from 81 Sqdn PR7 Canberrers at Tengah, Singapore when I was on 81, the next time I see a nav legging it down the wing and off the tip when one caught fire will not be the first time :shock: He ran down the wing because if he climbed down the steps he was directly in frond of the eng intake and had to run across the front of the missiles as well !!!

SAC Terry Jones has kindly sent me this description from when he worked as a member of a Javelin ground crew:

"I served with No 1 GWTS at RAF Valley in 59-61. We had six Javelins with Firestreaks doing the missile trials. The cartridges they used were about 1.5" dia 6-7" long. Black Plastic bodies and the breech took three. 'WET' starts, when the thing did not fire up on the first or second shot, were always an exhilarating sight, with many yards of flame from the tail pipe. Incidentally, I have had many a meat pie from the NAAFI wagon re-heated in the tail pipe after a sortie!"

Allen Mawby remembers the AVPIN starter:

"[...] the Mk 7 and 9 used AVPIN start. A small cartridge similar in size to a 12 bore pressurised and ignited the highly volatile Avpin which powered a small turbine which in turn started the engine.

This system was truly bad as the Avpin often either exploded the high pressure pipe lines, which ran through the main electrical and hydraulic bay in the underside or caused the turbine to overspeed, shed all its small blades through the engine intake which normally resulted in an engine change.

If the pipe lines exploded the wings were removed and the remainder was sent to be rebuilt!

I cannot remember a black powder cartridge start system ever causing damage. Avpin starts caused immense damage."

Mike Guy remembers similar problems:

"[...]later marks of Javelins were fitted with 'AVPIN' starters. Avpin was a very volatile fuel and the starter plumbing supplying the Avpin to the starter was prone to leaks.
As I remember fires during start up were not too uncommon & it wasn't unusual to see a ground crew member "legging" it across the tarmac closely followed by the flight crew."


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## Jonzjob (14 Sep 2012)

Just found this youtube. This shows a centrifugal compressor, the early type of engine as used by Meteors, Vampires, Venoms, etc.

http://www.youtube.com/watch?v=MUxP3PCDRTE&feature=fvwp

Not brilliant but this is a more modern engine with a multi stage linear compressor

http://www.youtube.com/watch?feature=en ... o8e6L3JTMQ

And this is a bypass turbine engine

http://www.youtube.com/watch?v=ON0sVe1y ... re=related

Good ere init!!


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## mailee (14 Sep 2012)

Well I am certainly learning some stuff here. I had always assumed a torpedo motor was powered by compressed air! I had no idea they actually used an internal combustion engine. Now i see about the starters on modern jet engines, thanks. I had heard of the cartridge starters before but assumed they were just used on marine Diesel engines and prop powered aeroplanes. Interesting here innit?


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## AES (16 Sep 2012)

Sorry about the delay folks, but AES has now got himself organised and got the promised piccies. I’ve compressed them all for web viewing (hence the “ … -C” in each title). I hope they’ll be clear to see OK here.

A310-1-C






This is the first shot of an Airbus A310 undergoing heavy maintenance. For info this particular aeroplane is/was operated by Air India after having started its life newly built for Swissair. The A310 is the 2nd “Scarebus” that Airbus produced (after the original A300) and this “stretched” model, the -300, seats roughly 220 in 2 or 3 classes over a medium range (e.g. Zurich to the Middle East). I took this pic because it clearly shows the LE Slats that I was talking about before. Here they’re fully deployed (“drooped”). If I remember correctly (it’s quite a few years since I had anything to do with A310s) they go down in 3 steps, ending up with 10 degrees down as shown here. The funny little vaguely triangle-shaped curved surface right up against the fuselage at the wing root is called a Kruger flap, and like the rest of the LE Slats, it increases the curvature (“camber”) of the front of the wing. BTW, I see that in my absence you’ve been discussing various types of gas turbine, so it may interest you to know that the “big hole” below the wing is where the No. 1 engine goes (it’s away in the shop for overhaul). The big outer round bit that’s left hanging from the pylon is the back end of the bypass duct, i.e. the rear of the engine nacelle. The “small hole” in the middle shows where the back end of the core of the engine, including its jet pipe, will fit. Big difference between the diameter of the fan at the front of the engine and the engine core at the centre isn’t there? This aircraft has Pratt & Whitney JT9D high-bypass ratio engines of about 50,000 lbs thrust each. There is of course another engine on the RH wing (otherwise the aeroplane would only go round & round in circles! ;-)

A310-2-C





View of the same aeroplane from above & behind. First, the inboard TE Flap has been removed and is sitting on a pair of cradles on the floor. More on that in a mo. The next “flap” hanging down but still fitted to the aeroplane is the Inboard Aileron. This provides roll control throughout all flight phases. Being a bit of a “barn door” surface it’s “hydraulically geared” so that up & down movements are quite large at low speeds (say up to about 220 mph) but are then much restricted above that speed. Next, on the upper surface of the wings there are 5 oblong “empty spaces”. These are the “Speed Brake/Spoiler” panels. They’re more or less flat panels, each powered by a hydraulic actuator. On landing, once the on-ground sensor says the aeroplane is firmly on the ground and the wheel-spin sensor confirms that they are turning at above about 140 mph, all 5 will be automatically raised to their max, about 60 degrees. This is “Spoiler” (or “lift-dumping”) mode. During high-speed flight (above about 220 mph) the 3 most outboard spoilers become “assistant ailerons” and are raised (by progressively smaller amounts as we move out along the wing towards the tip) to assist the “proper” (Inboard) aileron with roll control. The angle that these are raised to varies with the speed and their individual position along the wing. The outboard 4 of those 5 panels can also be raised to various angles (as signalled by the pilot) to act as Speed Brakes, for example during descent, when it may be necessary to slow down quickly to obey ATC instructions, or to quickly get below the max allowable Flaps lowering speed.
The pic does not show it (the wing tip is hidden under the balcony I was standing on) but believe me, this aeroplane has no Outboard Aileron out near the wing tip. Someone will no doubt ask me why, and being a smart a**e I will answer “ ’cos it makes the wing more efficient”; but when someone then asks “how’s that then?” I’ll have to reply that I’m not an aerodynamicist and don’t really understand it all. But the A310 is not the only aeroplane without Ailerons in the usual place (on/near the wing tip) but it’s one of the few that I know anything at all about.
The other apparently one big surface hanging down at an angle from the TE of the wing is the rest of the TE Flaps. More on those in pic A310-3-C.

A310-3-C

View of the same aeroplane from above & behind. First, the inboard TE Flap has been removed and is sitting on a pair of cradles on the floor. More on that in a mo. The next “flap” hanging down but still fitted to the aeroplane is the Inboard Aileron. This provides roll control throughout all flight phases. Being a bit of a “barn door” surface it’s “hydraulically geared” so that up & down movements are quite large at low speeds (say up to about 220 mph) but are then much restricted above that speed. Next, on the upper surface of the wings there are 5 oblong “empty spaces”. These are the “Speed Brake/Spoiler” panels. They’re more or less flat panels, each powered by a hydraulic actuator. On landing, once the on-ground sensor says the aeroplane is firmly on the ground and the wheel-spin sensor confirms that they are turning at above about 140 mph, all 5 will be automatically raised to their max, about 60 degrees. This is “Spoiler” (or “lift-dumping”) mode. During high-speed flight (above about 220 mph) the 3 most outboard spoilers become “assistant ailerons” and are raised (by progressively smaller amounts as we move out along the wing towards the tip) to assist the “proper” (Inboard) aileron with roll control. The angle that these are raised to varies with the speed and their individual position along the wing. The outboard 4 of those 5 panels can also be raised to various angles (as signalled by the pilot) to act as Speed Brakes, for example during descent, when it may be necessary to slow down quickly to obey ATC instructions, or to quickly get below the max allowable Flaps lowering speed.
The pic does not show it (the wing tip is hidden under the balcony I was standing on) but believe me, this aeroplane has no Outboard Aileron out near the wing tip. Someone will no doubt ask me why, and being a smart a**e I will answer “ ’cos it makes the wing more efficient”; but when someone then asks “how’s that then?” I’ll have to reply that I’m not an aerodynamicist and don’t really understand it all. But the A310 is not the only aeroplane without Ailerons in the usual place (on/near the wing tip) but it’s one of the few that I know anything at all about.
The other apparently one big surface hanging down at an angle from the TE of the wing is the rest of the TE Flaps. More on those in pic A310-3-C.

See "Part 2"


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## AES (16 Sep 2012)

View of the same aeroplane from above & behind. First, the inboard TE Flap has been removed and is sitting on a pair of cradles on the floor. More on that in a mo. The next “flap” hanging down but still fitted to the aeroplane is the Inboard Aileron. This provides roll control throughout all flight phases. Being a bit of a “barn door” surface it’s “hydraulically geared” so that up & down movements are quite large at low speeds (say up to about 220 mph) but are then much restricted above that speed. Next, on the upper surface of the wings there are 5 oblong “empty spaces”. These are the “Speed Brake/Spoiler” panels. They’re more or less flat panels, each powered by a hydraulic actuator. On landing, once the on-ground sensor says the aeroplane is firmly on the ground and the wheel-spin sensor confirms that they are turning at above about 140 mph, all 5 will be automatically raised to their max, about 60 degrees. This is “Spoiler” (or “lift-dumping”) mode. During high-speed flight (above about 220 mph) the 3 most outboard spoilers become “assistant ailerons” and are raised (by progressively smaller amounts as we move out along the wing towards the tip) to assist the “proper” (Inboard) aileron with roll control. The angle that these are raised to varies with the speed and their individual position along the wing. The outboard 4 of those 5 panels can also be raised to various angles (as signalled by the pilot) to act as Speed Brakes, for example during descent, when it may be necessary to slow down quickly to obey ATC instructions, or to quickly get below the max allowable Flaps lowering speed.
The pic does not show it (the wing tip is hidden under the balcony I was standing on) but believe me, this aeroplane has no Outboard Aileron out near the wing tip. Someone will no doubt ask me why, and being a smart a**e I will answer “ ’cos it makes the wing more efficient”; but when someone then asks “how’s that then?” I’ll have to reply that I’m not an aerodynamicist and don’t really understand it all. But the A310 is not the only aeroplane without Ailerons in the usual place (on/near the wing tip) but it’s one of the few that I know anything at all about.
The other apparently one big surface hanging down at an angle from the TE of the wing is the rest of the TE Flaps. More on those in pic A310-3-C.

A310-3-C






Here’s a picture of the removed Inboard TE Flap. Notice that it’s actually 2 separate (but joined) surfaces. There’s the highly cambered “LE Slat” belonging to this Flap segment that you can (hopefully) just see against the forward Main Landing Gear wheel. Notice also the “wavy” TE of this flap segment. This is partly due to the change of Dihedral (upward angling of the wings to aid stability) but is also a function of the fact that as said in my last post, the wing at the root (where it joins the fuselage) is set at a positive angle of incidence (i.e. nose up) but as we move out along the wing to the tip that angle of incidence is progressively “washed out” until at the tip it will be, typically MINUS a degree or so (nose down). As said before, this is to prevent/reduce “tip stalling” (i.e. the wing tip on the inside of a turn will otherwise tend to stall before the rest of the wing does). Not good for stability and control, let alone pax comfort!

A310-4-C





See Part 3


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## AES (16 Sep 2012)

his shows the Port Tailplane (Horizontal Stabiliser in American-speak). It’s one half of the “little wing at the back” that I spouted about in the previous post. There are 3 interesting things about this (and 2 apply to most other high speed aeroplanes):
1st, it is only slightly cambered (but almost flat) along the top surface (I have another photo in a minute showing the underside of a Tailplane). This means that compared to the wing itself, the Tailplane is mounted upside-down – i.e. - the most cambered surface is on the BOTTOM, not the top of the “wing”. This means that if our experiment with blowing on the bit of paper is correct (anybody tried it?) such Tailplanes are actually “sucking downwards” (if you’ll excuse the expression) rather than lifting upwards.
The 2nd thing is that again like most high speed aeroplanes, the angle of incidence of the taiplane can be adjusted by the pilot (or Autopilot). The Tailplane pivots as a complete unit around an “axle” positioned roughly opposite the highest points of those 2 “lozenge-shaped” grey bits you can see on the fuselage above and below the Tailplane. Thus the amount of “down-suck” can be adjusted to suit all phases of flight. Basically at high speeds we want the balance point – Centre of Gravity – of the whole aircraft to be very much rearwards – perhaps 70% of the chord (the front to back measurement of the “big” wing). But at low speeds like landing we want the C of G to be pretty far forward to assist stability. This is because one of the interesting things about high speed flight is that the nearer we get to the speed of sound (supersonic), then the further “naturally forwards” – becomes the C of G – i.e. the aeroplane tends to become more and more nose heavy. It’s not too clear in this picture but you may be able to see the 1 degree graduations marked on the fuselage at the Tailplane’s root to show the Tailplane’s range of movement. I have another photo to show in a minute which shows this rather more clearly (this time on an A319, but it’s pretty similar).
The 3rd interesting thing about this Tailplane (and quite a few others too) is that this is a “wet” Tailplane – i.e. it has a fuel tank within the aerofoil sections, just like the “big” wings. On the same lines as Concorde (which I believe was the first aircraft to have this feature), as speeds increase the fuel in the “Main” (Wing and Centre Section) tanks can be pumped aft to the Tailplane tanks. Otherwise the Tailplane would need to be set at an excessive nose down angle at high speed, increasing drag and therefore fuel burn. The Tailplane tanks also provide a “convenient” place to store more fuel, thus allowing the aeroplane to fly further. This aft and forwards pumping of fuel is reckoned (by Airbus) to reduce cruise speed drag, and therefore fuel burn, by about 1.5%. Unlike Concorde I believe, the movement of fuel is computer-controlled (though may be manually overridden).
Finally, at the very TE of the Tailplane we see the Elevator (just above the aircraft tug). There’s another exactly the same on the other side. As discussed in the last post, these are responsible for making the aeroplane climb or dive according to pilot (or Autopilot) inputs. Note that (like the Britannia others have already mentioned) all the control surfaces on modern aircraft are hydraulically powered, so when the any such aeroplane is at rest the surfaces will take up all sorts of strange angles. Very off-putting to those not knowing about such things.

A319-1-C






As said for the last picture, the under surface of the Tailplane is much more steeply cambered than its upper surface. As noted above, this happens to be an A319 (a somewhat smaller aeroplane than previous A310) but just about all high speed aeroplanes that I’ve ever seen have this same basic feature. This photo also clearly shows the angular graduations on the fuselage much more clearly than the previous photo, and the available range of movement is between +4 (nose up) and -12 (nose down) degrees on this particular type - the last 2 down positions are not normally used. This aeroplane doesn’t have the wet fin feature of the previous A310 but I still think this clearly illustrates what happens to the C of G as we get nearer and nearer to the speed of sound.
The angle of the Tailplane is set before Take-off, either manually by the pilot or more often, by the Flight Guidance Computer. It’s set according to the total weight and C of G position of the aeroplane, plus the wind (speed and direction), temperature and air density. During flight the FGC sends signals to the Autopilot to automatically move the Tailplane angle as speeds increase and decrease.

To be really “technical” we should also be talking about the “C of P” (Centre of Pressure), the “MAC” (Mean Aerodynamic Chord), and probably about “Winglets” too. But I think the above’s enough’s for now.

See Part 4


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## AES (16 Sep 2012)

B737-1-C & -2-C











Just to show I’m not (not reallyè) biased in favour of Airbus I’ve added a couple of pix of a different aeroplane type altogether – the Boeing B737. This is arguably the most successful commercial aeroplane (in terms of numbers produced and on order) since the famous Dakota/DC3 of WWII.
The first pic shows the TE flaps fully deployed (40 degrees) taken from behind the aeroplane. Note that unlike the earlier pic of the A310 Flap segment on the ground, this aeroplane has TWO separate surfaces in front of the “main” (i.e. the most rearward) Flaps. This has the effect of providing the Flaps with 2 separate “L-E Slats” of their own. These LE Slats enable the aerofoil sections of the Flaps themselves to operate at much higher angles of attack without stalling (i.e. the breakup of smooth airflow) over the Flaps. The Flaps would stall at much less than 40 degrees without these extra surfaces at the front - just like the functioning of the “real LE Slats” on the front of the wings.
The second view, from underneath, clearly shows how highly cambered these “high lift” surfaces really are. Nothing like symmetrical.


Well that’s about it from me for a while folks. I hope the above is interesting and not too much detail.

Just in closing, and NOT wanting to take a “jab” any anyone else posting on this thread - the poster early on in this thread who wrote that an aircraft’s wing cannot be compared with a boat’s sail will, I hope, now see that this statement is just not correct. The shape of an airliner’s wing (and of most other aeroplanes too) is “adapted” to optimise its efficiency during the various phases of flight. So just as sailing boat’s crew pull on ropes to change the shape of the sail, so the pilot (or Autopilot) changes the Flap and Slat positions – i.e. the shape of the aeroplane wing. And the EXACT equivalent of the sailing boat’s keel or centre-board is that big thing sticking up at the back of all aeroplanes – i.e. the Fin and Rudder (or ”Vertical Stabilizer” and Rudder in American speak). If any one doubts that Google for the 2 tragic accidents which amply demonstrate what happens if an aeroplane looses its Fin/Rudder. Not only will it not turn but it also becomes so unstable that it cannot stay airborne at all.

Krgds
AES


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## Jonzjob (16 Sep 2012)

Thank you for takinng the time AES! Great write up and photos.

I was always under the impression that as soon as you move a control surface you screw up the aeorfoil section so that could well be one reason for not having wing tip ailerons?

Justa slight correction about the Britannia. It doesn't have any power controls at all. The surfaces are moved by servo tabs on the trailing edge of each of them. The servo tabs are moved by 'torque tubes' each up to about 6 foot long and going through a small universal drive. They are about 1 /4" diameter and are so thin ally that you could actually crush them in your hand. The ailerons and elevators 'droop' until about 80 kts and the rudder flaps around until about 60 kts and has some kind of authority at about 90 kts so nose wheel steering is used till then. The only problem with those controls was that the elevator was so light it had to be fitted with a feel control or the driver could just pull too much movement. The idea is that the driver pulls up, the servo tab on the elevtor moves down, the elevator is pushed up, the tail goes down and the aircraft climbs, hopefully :mrgreen: 

It was also the very first 'fly by wire' commercial passenger aircraft in that it had Ultra Throttle analog computer controls with no mechanical connection at all. If the Ultra failed there was a switch just behind each throttle lever to switxh that throttle to manual and behind that switch was another little center sprung toggle switch which became the throttle. The drivers didn't like that too much. No big butch lever to push/pull. It did mean that if he, there weren't any shes then as far as I know, tried to do something that was likely to do the engine a mischief it didn't happen.

One of the things on the VC10 is that each of the control surfaces are split into sections. Each section being individually controlled by its own hydraulic system. There aren't any mechanical connections from the stick to them. They work by changing the phase position in a 3ø transmitter and the receiver takes up the same position. Much easier to understand than to try to explain :? his does it better than I http://www.allaboutcircuits.com/vol_2/chpt_13/11.html . It made it a extreamly safe aircraft in that you could have dammage to or failure of a control surface and only part of it would fail, the others would still function. They could be pippers to set up though and it was part of my trade to do so!

The other thing about the original R.A.F.VC10s were that they had a 'wet' fin and as one clown found out, if you fuel that one first opr defuel it last it will sit up on its ass! http://www.vc10.net/History/incidents_a ... ber%201997


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