Accumulator braking
Thread Starter
Joined: Mar 2007
Posts: 2,766
Likes: 4
From: Here and there
Accumulator braking
If you only have the accumulators for braking,no anti-skid,how long do you apply brake pressure for before releasing?
Last edited by tubby linton; 20th April 2013 at 21:40.
Thread Starter
Joined: Mar 2007
Posts: 2,766
Likes: 4
From: Here and there
Cars generally do not operate on limited lengths of road.I was just interested in the technique of braking a heavy aircraft with no anti-skid and limited brake pressure. Can you lock a wheel at 1000psi ? Has anybody on here tried it for real rather than the sim?
Joined: Apr 2004
Aviation Qualifications: LAME
Posts: 2,281
Likes: 189
From: Dorset UK
I only know about the A300.
Recommendation is to not exceed 1000 psi brake pressure without anti skid. A fully charged accumulator will be at 3000 psi. This will give about 6 brake applications before the stored pressure is dissipated. Best practice is to apply brakes gently and have another crew member call the indicated pressure so you can adjust foot pressure accordingly.
Yes you can lock a wheel with 1000 psi if the surface is slippery.
Yes I have been part of a crew that did this for real with a dual hydraulic failure, and we did not flat or burst any tyres.
Me in middle seat.
Recommendation is to not exceed 1000 psi brake pressure without anti skid. A fully charged accumulator will be at 3000 psi. This will give about 6 brake applications before the stored pressure is dissipated. Best practice is to apply brakes gently and have another crew member call the indicated pressure so you can adjust foot pressure accordingly.
Yes you can lock a wheel with 1000 psi if the surface is slippery.
Yes I have been part of a crew that did this for real with a dual hydraulic failure, and we did not flat or burst any tyres.
Me in middle seat.
Joined: Nov 2000
Posts: 562
Likes: 0
From: Grobelling through the murk to the sunshine above.
If you have such a failure, you are probably not going to head for a limiting runway, so why not just brake at a normal rate?
(I think I crossed posting with Autoflight - same answer really)
(I think I crossed posting with Autoflight - same answer really)
Last edited by Pub User; 20th April 2013 at 22:38.
Joined: Apr 2004
Aviation Qualifications: LAME
Posts: 2,281
Likes: 189
From: Dorset UK
Tubby,
Technique is to apply the brakes once only if possible and hold the 1000 psi until low speed and then reduce pressure gently until stopped. Then set the parking brake, shut down and get towed off the runway.
I heard a story of a Canberra that landed at Akrotiri with hydraulic failure. The one shot emergency brake was used with success. The tower then asked if he could taxi off the runway as there were some Victors waiting to take off. The pilot released the brake and then rolled off the end of the runway having neither brakes or steering. Result: runway closed.
Technique is to apply the brakes once only if possible and hold the 1000 psi until low speed and then reduce pressure gently until stopped. Then set the parking brake, shut down and get towed off the runway.
I heard a story of a Canberra that landed at Akrotiri with hydraulic failure. The one shot emergency brake was used with success. The tower then asked if he could taxi off the runway as there were some Victors waiting to take off. The pilot released the brake and then rolled off the end of the runway having neither brakes or steering. Result: runway closed.
Joined: Apr 2010
Posts: 0
Likes: 0
From: Home soon
Recommendation is to not exceed 1000 psi brake pressure without anti skid
The pilot released the brake and then rolled off the end of the runway having neither brakes or steering. Result: runway closed
Last edited by de facto; 21st April 2013 at 10:29.
Joined: Jan 2008
Posts: 1,191
Likes: 0
From: lancs.UK
Somewhat off topic but related:- Citroens with hydro-pneumatic brakes, including the magnificent DS and CX designs, had just such .a system (Also licensed to RR for the Shadow and Spirit .
For the tech . minded, Citroen used a belt-driven multi-cylinder Swash-plate pump which charged an accumulator , being a sphere with a diaphragm dividing it. the back of the diaphragm was nitrogen-pressurised. A priority- valve sequentially isolated the Suspension, Steering assistance and finally the brakes.
With a good accumulator , a half-dozen applications could be performed.
This presupposes you ignored the christmas-tree of red panel "STOP" lights.
It was possible to "ease" the brakes and thus extend the cycles, but frightening in 2 tons of Rolls, the parking-brake of which was somewhat marginal!
A steady pressure to standstill is the technique of choice and i guess the aircraft system is the same.
For the tech . minded, Citroen used a belt-driven multi-cylinder Swash-plate pump which charged an accumulator , being a sphere with a diaphragm dividing it. the back of the diaphragm was nitrogen-pressurised. A priority- valve sequentially isolated the Suspension, Steering assistance and finally the brakes.
With a good accumulator , a half-dozen applications could be performed.
This presupposes you ignored the christmas-tree of red panel "STOP" lights.
It was possible to "ease" the brakes and thus extend the cycles, but frightening in 2 tons of Rolls, the parking-brake of which was somewhat marginal!
A steady pressure to standstill is the technique of choice and i guess the aircraft system is the same.
Joined: Sep 2011
Posts: 352
Likes: 148
From: FL390
Technique is to apply the brakes once only if possible and hold the 1000 psi until low speed and then reduce pressure gently until stopped. Then set the parking brake, shut down and get towed off the runway.
