Posts about: "Tailwheel" [Posts: 6 Pages: 1]

EXWOK , more than happy to take a hint........PLEASE! and welcome to this gem of a thread.

With the FBW, was there any feedback built into the yoke? The Airbus with it's "joystick" has, I believe, no feel unlike a Flight Sim force feedback one.
If there was a yoke movement on one side did the other side mirror the movement or like the Airbus did the sidestick play dead?

M2 , it appears the tailwheel was, so far, the only "fault" in an otherwise extreme machine. Were there any other items like the tailwheel that were unworthy to be in her?

Does anyone have a tech drawing of the "sliding seals" used in the hydraulics. I have trouble visualising something that could withstand the 4,000psi pressure. Why was such a high pressure used? After all the control surfaces couldn't have required that much input to effect an authority movement. I understand it was also a special fluid that was used. Was this because of the pressure it was under or the temperature extremes?

Biggles78
The tailwheel design really was the one exception in poor design terms, but I'm sure that if the aircraft was doing what she should be doing right now, (you know routinely flying across the Atlantic and beyond, instead of languishing in museums), modifications would have finally put this particular malady to bed). In design terms, the rest of the aircraft was nothing short of a flying work of art, a masterpiece. Having said that though, personally I would rather that four rather than three hydraulic systems had been used. Originally there were four systems in the design, but the RED system was deleted, as it was felt to be superfluous. My own view is that this particular decision was total poppycock. Oh, and Green, Blue and Yellow hydraulic systems was something else that Airbus copied from Concorde.... although we ourselves pinched that idea off of the Comet ).
As far as the hydraulic expansion joints go, I will scour around and see if I can find a diagram for you. Try and picture two titanium (or stainless) tubes, on inside the other, with a sealed chamber being formed at the join. Inside this chamber were multiple lands fitted with special viton GLT seals. They did work incredibly well, although occasionally one of the seals gave out, and things got wet, VERY WET.
As far as the 4000 PSI hydraulic system, as EXWOK quite rightly pointed out, the loading on the flying control surfaces were immense throughout the whole flight envelope. (Picture alone just the T/O from JFK RWY 31L, where the aircraft is tightly turning and the gear retracting, all at the same time). As well as the flying controls and landing gear, you also had the droop nose to consider, four variable engine intakes as well as a couple of hydraulically operated fuel pumps. Oh, and in emergencies, a hydraulically driven 40 KVA generator too. The reason that 4000 PSI was chosen was that if a large amount of hydraulic 'work' was to be done, the only way to keep the size of jacks and actuators to a reasonable size/weight was to increase the system pressure by 25% from the normal 3000 PSI. (On the A380 they've gone a step further and gone for 5000 PSI, saving them over a tonne on the weight of the aircraft).
Concorde used a special hydraulic fluid, Chevron M2V. This is a mineral based fluid, as opposed to the ester based Skydrol, used by the subsonics. The reason that we went for a different fluid was a simple one; Skydrol is rubbish at the high temperatures that Concorde operated at, no good at all in fact, so we needed something better and in M2V we found the PERFECT fluid. As an aside, unlike Skydrol, that attacks paintwork, certain rubber seals, skin, EYES etc., M2V is completely harmless, wash your hair in it. (I did, several times when we had leaks. Thinking about it, maybe THAT is why my hair is such a diminished asset

EXWOK
It's so great having another of my pilot friends diving in to this post, welcome welcome
I remember the Mech' Signalling part of the air tests, my lunch has just finished coming back up thank you. (for interest chaps and chapesses, with mechanical signalling, using just the conventional control runs under the floor, there was no auto-stabilisation).

The artificialfeel system worked incredibly well I thought, I always found it curious that the peak load law in the computer was at the transonic rather that the supersonic speed range. It was explained to me long ago that this was because the controls really are at their most sensitive here, but at high Mach numbers are partially 'stalled out', due to shockwave movements along the surfaces, and were therefore less effective. (For this reason I was told, the inner elevons were so critical for supersonic control, being the most effective of all elevons at high speed).

To all , I forgot to mention in my previous post regarding the engine failure in G-BOAF in 1980; I remember an FAA surveyor, who was taking a look at the carnage within the engine bay, saying that in his opinion, no other aircraft in the world could have survived the intensity of the titanium fire that ensued. Analysis showed that the fire was successfully extinguished, possibly at the first shot of the fire bottle. This was a testament to the way that the Concorde engine bay could be completely 'locked down' when the fire handle was pulled, as well as to the way that the whole engine installation was technically encased in armour plate. To put all this in context, acording to Rolls Royce a titanium fire, once it takes hold, can destroy the compressor of a jet engine in four seconds.


Dude

Christiaan,


Since you were discussing the scenario of a nosewheel not lowering and that the CG was over the main wheels may I suggest a rather (amusing at least)
possibility ?!!



With a nose gear jammed up but all other gear lowered normally could the Flight Engineer pump fuel rearward adjusting the CG aft sufficiently to allow the Concorde to settle back on her 'Tailwheel'



I realise there would be some damage, especially in light of what has been said about the occasional tailwheel contacts but I imagine it would be less than lowering the unprotected forward fuselage onto the runway.





Of course some pax might have to move to the back of the cabin too !



If the CG was adjusted this far aft would there be controllability issues ?




There could finally be a use for the 'full down position of the visor' landing in this attitude !

Why not?
Let's admit that being faced with that nasty situation in reality would not have been amusing....
But kicking the idea around a moment, why not? It's what I did seeing the question at first.

Obviously depends a bit on the fuel remaining, but yes, I think one could have move the CG sufficiently rearward.

LOL, don't you think they'd all would have moved as far back as possible anyway?

Possibly, but not enough that an experienced pilot couldn't handle it, I would think.

I don't quite follow you there...

One thing that promptly occurred to me for this 'no nose wheel' scenario is braking, since both engine reverse and main gear wheel braking act below the CG, so they'd both act to pull the nose down.
At some point, stick fully back, hence elevons fully up, will no longer be enough to fully counteract that, so you'll have to cancel reverse and braking, and probably commit to an overrun.
Your scenario of doing it as a 'three-pointer' on the tail might wel be the better one !


And while we're at it, what about ditching a Concorde?
It's hinted at in the Safety Cards.
It's been tried lots of times, with models in water tanks.
It wasn't really feasible.......

CJ

Finally, after 3 nights reading this thread in my spare time i've come to the end of it (for now - it's an organic thing!) and i'd just like to echo the thanks from a wide-eyed SLF who always ran outside of my house every time she went overhead twice a day - and what a noise

Anyway, I have 2 questions to put to the assembled experts:

1) Earlier it was mentioned that the tailwheel was the only piece of bad design on the Concorde. Does this mean that the rudder failures were as a result of corrosion/fatigue of a sound original design and that it was just a bit of bad luck that nobody could have foreseen? also, how easy was it to remedy?

2) Were the rudder separation and the in-flight "hole in the wing" issue (reported on the Concorde TV programme) the most serious issues experienced during service? or were there any other issues which manifested themselves such that the passengers were oblivious but the crew were more than a little concerned?

Thanks!
Mike.
(p.s. - my wife's still chuckling at the Prince Philip story)

If I may be permitted to tread drift a bit re engine rotation effects: prop-driven aircraft suffer a range of unpleasant effects that jets don't. Not least is the prop slipstream effect; the propwash spirals around the aeroplane and pushes on the fin inducing a turn. This is at its worst at take off, with no slipstream and high power; even our Chipmunk needs a bootful of left rudder to keep straight when full power is applied at the start of the take-off roll. A really powerful aeroplane like a Spitfire cannot use full power until there is sufficient airspeed to make the rudder effective enough to keep straight; one reason why later Spits had contra-rotating props.

Then, for a taildragger like the Chippy, there's the 'assymetric blade effect' or 'p' factor, where with the tail down the down-going prop blade produces more thrust than the up-going one. And the engine torque effect particularly noticable on soft runways with powerful aeroplane where one mainwheel tyre is pushed into the ground with more force than the other, and finally the gyroscopic swing induced in a taildragger as the tail comes up and the prop disc is tilted to the vertical.

All of these effects are cumulative, and it's one reason why tail-wheel prop pilots learn to use their feet! All are obviated by contra-rotating props or, for twins, 'handed' engines which rotate in opoosite directions to each other.

When I had a share in a Yak52 I used to use the 'engine torque effect' to steer the aeroplane on Barton's muddy winter surface; using the conventional method (braking the appropriate mainwheel; the nosewheel was free-castoring) didn't work as the (quite thin) wheel would just lock and slide along, not inducing a change of direction at all. But whack on a fistful of Vendeneyef and 360hp would dig the right main into the ground and she'd turn right. Pull the power off suddenly and the left main would dig in, turning her left. Worked a treat!