Brake temps hot on downwind side.
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
Theory 1 would presuppose the upwind wing is producing effective lift. On landing the spoilers are delayed pretty damn quickly = PDQ. The lift is dumped. The brakes are ON. IMHO neither wing will be producing any significant lift. Then the TR's are deployed and the brakes reduce. All this happens in seconds.
Hence my scepticism about this theory.
To confirm, yes/no you'd need lift sensors on the wings. Perhaps AB, or Boeing, has some wind tunnel data to share with us. I'm sure they researched the lift dump phenomena during the design of spoilers and brakes and the stopping calculations including that of RTO. Remember TR's are not included in that. Hence they would want to design a very effective lift dump system to maximise the braking and reduce their size & weight.
Hence my scepticism about this theory.
To confirm, yes/no you'd need lift sensors on the wings. Perhaps AB, or Boeing, has some wind tunnel data to share with us. I'm sure they researched the lift dump phenomena during the design of spoilers and brakes and the stopping calculations including that of RTO. Remember TR's are not included in that. Hence they would want to design a very effective lift dump system to maximise the braking and reduce their size & weight.
Apart form any lift effects, the wind pressure on the fuselage and vertical stabilizer (acting at a center some distance above the runway) would create a torque and a weight shift onto the downwind gear. But I doubt this is very significant, and rudder input to prevent weather-cocking would also also offset some of the torque about the longitudinal axis. And unless there was an anti-lock brake release on the upwind gear (unlikely on a dry runway?) it's not clear how it could affect brake temps at all.
Join Date: Jan 2014
Location: N5109.2W10.5
Posts: 720
Likes: 0
Received 0 Likes
on
0 Posts
On landing the spoilers are delayed pretty damn quickly = PDQ. The lift is dumped. The brakes are ON. IMHO neither wing will be producing any significant lift.
from 5:24 and note the oleo extension visible on both main gears.
At 5:33 the ground spoilers are fully deployed. Note the oleo extension visible on the LHS but RHS seems to be fully compressed.
MED autobrake is attempting to achieve the selected deceleration rate 2 secs after spoiler deployment.
On which side do you think the wheels are carrying more weight?
I'm sure they researched the lift dump phenomena during the design of spoilers and brakes and the stopping calculations including that of RTO.
And unless there was an anti-lock brake release on the upwind gear (unlikely on a dry runway?)
Last edited by Goldenrivett; 23rd Oct 2016 at 16:22. Reason: typo
9 points.
Never flown an Airbus but I'm not seeing your point, are you stating this is AB procedure, to always have your feet up on the pedals even during take off, thus steering with your heels and quite possibly applying brake pressure ?
Anyone else do this, on any type ?
And what does having an engine failure at low speed have to do with it, there will be an initial swing which you correct with rudder and nosewheel steering then moving your feet up to the brakes to stop.
But since you will immediately close the throttles the swing will be brief.
Heels on the floor for take off.
Never flown an Airbus but I'm not seeing your point, are you stating this is AB procedure, to always have your feet up on the pedals even during take off, thus steering with your heels and quite possibly applying brake pressure ?
Anyone else do this, on any type ?
And what does having an engine failure at low speed have to do with it, there will be an initial swing which you correct with rudder and nosewheel steering then moving your feet up to the brakes to stop.
But since you will immediately close the throttles the swing will be brief.
Heels on the floor for take off.
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
Heels on the floor for take off.
Remember he Air Crash Investigation into the Russian B727 look alike crash with the national hockey team onboard. One contributory factor was the unfamiliar PNF having feet on brakes during takeoff.
Is this not basic Cessna/Cherokee stuff in flight school?
Remember he Air Crash Investigation into the Russian B727 look alike crash with the national hockey team onboard. One contributory factor was the unfamiliar PNF having feet on brakes during takeoff.
Is this not basic Cessna/Cherokee stuff in flight school?
Thread Starter
Join Date: Jun 2007
Location: Doha
Posts: 64
Likes: 0
Received 0 Likes
on
0 Posts
Rat 5 – Indeed. I am just guessing. Would love to hear from Airbus or Boeing on this.
Chu chu – agreed.
Goldenrivett – interesting.
TangoAlphad – sorry I was rushing and literature is not my strong point. No sarcasm intended. Genuinely grateful for your insight.
THE OTHER THREAD – HEELS UP OR DOWN:
Stilton – Perhaps this should be a new thread. Briefly, there will be significant swing because it takes time for the pilot to recognise and react. At low speed the aerodynamic rudder response is minimal. It’s all down to nose wheel and differential braking, basically. The nose wheel won’t save you so it comes down to differential braking. The Airbus FCTM now says:
“The flight crew must have their feet in a position so that full rudder deflection combined with full
braking, even differential, can be applied instinctively and without delay.”
You can’t do that with your heels on the floor my friend. Have a look at the Airbus rudder pedals next time you fly it.
If you want to follow this up further, PLEASE start a new thread on it.
Rat 5 – Again, please start a new thread. Briefly, some (perhaps most) aircraft are designed to be flown heels down, some are designed so that you can do it either way. It is not a law of physics that designers must comply with the heels down philosophy no more than it is a law of physics that you must use a control wheel instead of a stick. PLEASE, start a new thread. I won’t comment on this point again on this thread.
Back to the subject of this thread.
Thanks to all for your input. I’m still left unsure of what is happening. Are there any Airbus or Boeing people out there who would like to comment?
Chu chu – agreed.
Goldenrivett – interesting.
TangoAlphad – sorry I was rushing and literature is not my strong point. No sarcasm intended. Genuinely grateful for your insight.
THE OTHER THREAD – HEELS UP OR DOWN:
Stilton – Perhaps this should be a new thread. Briefly, there will be significant swing because it takes time for the pilot to recognise and react. At low speed the aerodynamic rudder response is minimal. It’s all down to nose wheel and differential braking, basically. The nose wheel won’t save you so it comes down to differential braking. The Airbus FCTM now says:
“The flight crew must have their feet in a position so that full rudder deflection combined with full
braking, even differential, can be applied instinctively and without delay.”
You can’t do that with your heels on the floor my friend. Have a look at the Airbus rudder pedals next time you fly it.
If you want to follow this up further, PLEASE start a new thread on it.
Rat 5 – Again, please start a new thread. Briefly, some (perhaps most) aircraft are designed to be flown heels down, some are designed so that you can do it either way. It is not a law of physics that designers must comply with the heels down philosophy no more than it is a law of physics that you must use a control wheel instead of a stick. PLEASE, start a new thread. I won’t comment on this point again on this thread.
Back to the subject of this thread.
Thanks to all for your input. I’m still left unsure of what is happening. Are there any Airbus or Boeing people out there who would like to comment?
Well you might not want to comment further 9 points but I will.
I've done low speed aborts with engine failure in the sim and never was a problem, NEVER had any instructor or fellow Pilot advocate your 'technique'
Never flown an Airbus that's true but I'd like to hear from any other AB Pilot that advocates this, in fact I don't think that's their intention from the excerpt you've included.
After all they don't actually state 'place your feet up on the rudder pedals for take off'
I think it's just your interpretation and It doesn't seem right to me, it sure isn't on any Boeing.
I've done low speed aborts with engine failure in the sim and never was a problem, NEVER had any instructor or fellow Pilot advocate your 'technique'
Never flown an Airbus that's true but I'd like to hear from any other AB Pilot that advocates this, in fact I don't think that's their intention from the excerpt you've included.
After all they don't actually state 'place your feet up on the rudder pedals for take off'
I think it's just your interpretation and It doesn't seem right to me, it sure isn't on any Boeing.
Thread Starter
Join Date: Jun 2007
Location: Doha
Posts: 64
Likes: 0
Received 0 Likes
on
0 Posts
Stilton. I don't appreciate being called a liar and note that you have never flown an Airbus. It seems to me that you are too keen to generate this topic, perhaps you lack a social life? Why don't you go bother your ex wife.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,407
Likes: 0
Received 0 Likes
on
0 Posts
9 points, RAT5
Both of you are saying half truth. Nothing is forbidden or recommended. If there is any diktat about feet position on take off it is only from some airline. I have read a discussion on this at an airbus TRTO where both techniques were used and taught. SO feet up is as much valid as feet down. I have used feet up while flying B747 classic where the rudders were not connected with the nose wheel and with it's size, inertia and wet run way it can be a handful. I did execute a low speed reject in B747 and with my feet up I didn't have to give it a second thought. But there is a technique while using rudder on take off if you keep the feet up. In the A320 with rudder connection feet in any position is not a problem. I didn't see in the FCTM anything about feet I position. Perhaps you can give the page No. But what it does say is "To select both reversers irrespective of which engine has failed" obviously more for the effect akin to differential braking than stopping. And to use steering hand wheels when taxi is used and not before because nose wheel will skid and aggravate the problem. There has been a thread on this before and no point wasting time starting again promoting personal preferences. .
Both of you are saying half truth. Nothing is forbidden or recommended. If there is any diktat about feet position on take off it is only from some airline. I have read a discussion on this at an airbus TRTO where both techniques were used and taught. SO feet up is as much valid as feet down. I have used feet up while flying B747 classic where the rudders were not connected with the nose wheel and with it's size, inertia and wet run way it can be a handful. I did execute a low speed reject in B747 and with my feet up I didn't have to give it a second thought. But there is a technique while using rudder on take off if you keep the feet up. In the A320 with rudder connection feet in any position is not a problem. I didn't see in the FCTM anything about feet I position. Perhaps you can give the page No. But what it does say is "To select both reversers irrespective of which engine has failed" obviously more for the effect akin to differential braking than stopping. And to use steering hand wheels when taxi is used and not before because nose wheel will skid and aggravate the problem. There has been a thread on this before and no point wasting time starting again promoting personal preferences. .
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
Regarding feet position. I'm assuming that >90% of current jet a/c have an RTO function on autobrakes. Thus, in an RTO, should they work as advertised, your feet are for steering and not stopping. Should, OMG, the RTO function not work, it is sensed PDQ by the alert pilot, and in the flash of a big toe nail your feet should be able to transition from heels down to heels up.
There will always be the argument in the case of a Stop limiting runway that any delay could be critical: but then you'd have to have a multiple failure of the system that caused you to RTO and an autobrake failure. Statistically unlikely.
The same argument can go for landing. Where do you put your feet then?
In my sim experience I see too many crews disarm RTO autobrake function during an RTO. That is less likely to happen heels down. In a strong x-wind slippery runway I would rather have my feet concentrating on steering that stopping. If you inadvertently disarm the autobrakes you now have a greater problem with pedal steering & stopping.
There will always be the argument in the case of a Stop limiting runway that any delay could be critical: but then you'd have to have a multiple failure of the system that caused you to RTO and an autobrake failure. Statistically unlikely.
The same argument can go for landing. Where do you put your feet then?
In my sim experience I see too many crews disarm RTO autobrake function during an RTO. That is less likely to happen heels down. In a strong x-wind slippery runway I would rather have my feet concentrating on steering that stopping. If you inadvertently disarm the autobrakes you now have a greater problem with pedal steering & stopping.
Guest
Posts: n/a
I think the idea that the downwind brake is hotter because of weight being reduced on the upwind leading to brakes being released to stop locking is unlikely. The wheels are nowhere near skidding on a low or medium brake, even with reduced weight.
It is indeed taught to have your wheels up on the brakes in an A320. I certainly was. I ignored it.
It is indeed taught to have your wheels up on the brakes in an A320. I certainly was. I ignored it.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,407
Likes: 0
Received 0 Likes
on
0 Posts
I agree that with Auto brake working there is no need to keep the feet up. In 747 classic without RTO and free rudders was tricky. In airbus you won't have AB working below 72kts but stopping is not an issue at that speed. Slippery runway crosswind engine fail feet up differential braking helps in keeping it straight as well stopping. Feet up you have to use rudders with heel or lower half of the foot for directional control otherwise inadvertent brake application will send brake temperatures up or disconnect AB. Landing is different because AB is not a necessity and limiting landing distance you are in a position to quickly apply both or differential braking as required. Airbus rudder pedals are flat perhaps made to keep your feet up.
9 points , I thought you 'weren't going to respond' anymore ?!
You might want to go back and re-read my reply, no one called you a liar, I just questioned your interpretation of recommended feet placement.
You might want to look at your social skills a little yourself.
You might want to go back and re-read my reply, no one called you a liar, I just questioned your interpretation of recommended feet placement.
You might want to look at your social skills a little yourself.
Thread Starter
Join Date: Jun 2007
Location: Doha
Posts: 64
Likes: 0
Received 0 Likes
on
0 Posts
Canute – yes I agree, I don’t think the upwind brakes release. However, they may do less work without releasing simply because of having less weight on them. I’m talking about auto brake LO, not MED. So even without releasing they may still work harder > get hotter.
Feet up or down >
1. The current FCOM and FCTM use a more digital referencing system and page numbers can be a bit complex but if you look in the FCTM under normal ops, pre-start, miscellaneous you will find it. It is a relatively new addition to the FCTM, was put in within the last year or so I think.
2. If you have not had or do not have the opportunity to try an engine failure in the A320 at 40 kts on a wet narrow runway with a tailwind and TOGA then you should consider refraining from condemning the foot up option until you do have the opportunity or until you can get an official ruling from Airbus.
Feet up or down >
1. The current FCOM and FCTM use a more digital referencing system and page numbers can be a bit complex but if you look in the FCTM under normal ops, pre-start, miscellaneous you will find it. It is a relatively new addition to the FCTM, was put in within the last year or so I think.
2. If you have not had or do not have the opportunity to try an engine failure in the A320 at 40 kts on a wet narrow runway with a tailwind and TOGA then you should consider refraining from condemning the foot up option until you do have the opportunity or until you can get an official ruling from Airbus.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,407
Likes: 0
Received 0 Likes
on
0 Posts
9 points
All I find in FCOM is
The rudder pedals must then be adjusted to ensure the pilot can achieve both full rudder pedal displacement and full braking simultaneously on the same side.
Although I have been a protagonist of feet up I cannot say it means that. All it means is you should be capable of applying full rudder and differential braking. Why differential braking is added I can tell you that. There was one runway excursion because of sitting too far back the pilot ran out of leg length to apply differential braking. So it is as I said nothing is forbidden or recommended. In A320 I didn't have to particularly teach to keep feet up. Although it is quicker to use differential braking feet up most manage it either way. In a low speed reject right seat take off creates more problems than feet down.
All I find in FCOM is
The rudder pedals must then be adjusted to ensure the pilot can achieve both full rudder pedal displacement and full braking simultaneously on the same side.
Although I have been a protagonist of feet up I cannot say it means that. All it means is you should be capable of applying full rudder and differential braking. Why differential braking is added I can tell you that. There was one runway excursion because of sitting too far back the pilot ran out of leg length to apply differential braking. So it is as I said nothing is forbidden or recommended. In A320 I didn't have to particularly teach to keep feet up. Although it is quicker to use differential braking feet up most manage it either way. In a low speed reject right seat take off creates more problems than feet down.
Last edited by vilas; 26th Oct 2016 at 10:40.
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
What I am curious about, unless there is some intrinsic design item, is why some discussions on Tech Log relate to type. Often, IMHO, the topic is a general aviation one and I was not aware that one manufacturer had a greater claim to an inside knowledge of aviation techniques, physics, aerodynamics etc., than another.
Does this not fit the general category, or is there someone at AB who knows better than all the other manufacturers and has designed their a/c accordingly?
It was like when a new CP arrived and suddenly some of the old tried & tested SOP's changed with no explanation nor apparent good reason. Usually a personal preference.
Does this not fit the general category, or is there someone at AB who knows better than all the other manufacturers and has designed their a/c accordingly?
It was like when a new CP arrived and suddenly some of the old tried & tested SOP's changed with no explanation nor apparent good reason. Usually a personal preference.
Join Date: Jan 2006
Location: US
Posts: 2,205
Likes: 0
Received 0 Likes
on
0 Posts
Below 80-85 kts, depending upon manufacturer, the auto brakes don't work.
If you lose an engine at low speed, or one engine is slow accelerating, the rudder pedal isn't the way to prevent going off the runway. Idle power to stop the asymmetrical thrust is the answer. LHR 27R has two long skid marks left by departing a/c that had asymmetrical thrust. The nose wheel tires, depending upon speed, asymmetrical thrust level, runway friction, can't handle the side load.
Feet up for 34 years after flying the SDS3-30 in crosswind landings, but thrust reduction is the primary method to control a thrust asymmetry event on takeoff.
If you lose an engine at low speed, or one engine is slow accelerating, the rudder pedal isn't the way to prevent going off the runway. Idle power to stop the asymmetrical thrust is the answer. LHR 27R has two long skid marks left by departing a/c that had asymmetrical thrust. The nose wheel tires, depending upon speed, asymmetrical thrust level, runway friction, can't handle the side load.
Feet up for 34 years after flying the SDS3-30 in crosswind landings, but thrust reduction is the primary method to control a thrust asymmetry event on takeoff.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,407
Likes: 0
Received 0 Likes
on
0 Posts
It is actually off topic but low speed reject there are simultaneous actions. Feet applying as much rudder including differential braking to keep it straight(I have seen people going off to other side). Hands pulling thrust levers back all the way to reverse. Stopping is not an issue.
Just been revising for my next SIM and found this: FCOM PER-LDG-GEN 'Use of the autobrake system'
So, as I suspected, the autobrake does keep the aircraft straight on the runway, and therefore, with a crosswind, the downwind brake will do more work to prevent weather cocking, and hence get hotter.
Thinking about it, during landing I never have to do much to keep straight in a crosswind after the autobrake cuts in, but I do have to work the rudder/NWS to keep straight during a crosswind take-off.
.
..........furthermore, it ensures a straight roll-out............
Thinking about it, during landing I never have to do much to keep straight in a crosswind after the autobrake cuts in, but I do have to work the rudder/NWS to keep straight during a crosswind take-off.
.