aerodynamic braking
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aerodynamic braking
I watched recently a wide body aircraft perform the above maneuver to the extreme and I enjoyed the hell out of the sight. Previously I have not seen it for over a decade (741/742) and even then it was taboo. Understandably the risk of dragging a tail is the factor.
I feel like it may be the last time I will see a hands on aviator in action in commercial aviation. Am I wrong? I would like to hear feedback on the matter and a current view on the procedure.
From my perspective there is no more efficent landing procedure than this.
I feel like it may be the last time I will see a hands on aviator in action in commercial aviation. Am I wrong? I would like to hear feedback on the matter and a current view on the procedure.
From my perspective there is no more efficent landing procedure than this.
Poor idea in a wide body--easy to tail strike, better braking with weight on wheels, vastly superior directional control on all gear. Looks fancy, was important in high speed fighters, no place in transport category airplanes.
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grounded27
About a decade ago when I was flying 747 classic some of my collegues were doing it and highly recommending it. Somehow I never agreed with this practice. It was not company procedure. No Boeing document supported it. On the contrary the documents stated any delay in putting the nose down increases landing distance. Also it raises the nose very high and is not comfortable for passengers especially in first class. Aerodynamically speaking it defeats the purpose of ground spoilers because while spoilers spoil the lift you keep adding to it by increasing the angle of attack. Maximum braking results when full weight of the aircraft is on wheels. Also the risk of tail strike. If the runway length is plenty to spare or you have no other means of breaking including the accumulator only then may be justified.
About a decade ago when I was flying 747 classic some of my collegues were doing it and highly recommending it. Somehow I never agreed with this practice. It was not company procedure. No Boeing document supported it. On the contrary the documents stated any delay in putting the nose down increases landing distance. Also it raises the nose very high and is not comfortable for passengers especially in first class. Aerodynamically speaking it defeats the purpose of ground spoilers because while spoilers spoil the lift you keep adding to it by increasing the angle of attack. Maximum braking results when full weight of the aircraft is on wheels. Also the risk of tail strike. If the runway length is plenty to spare or you have no other means of breaking including the accumulator only then may be justified.
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Aerodynamic braking will never be approved by FAA or any airline so don't promote it. We all know it would work in an emergency if wheel braking was inop but not for normal ops.
Last edited by bubbers44; 27th May 2013 at 01:51. Reason: spelling
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vilas
Aerodynamically speaking it defeats the purpose of ground spoilers because while spoilers spoil the lift you keep adding to it by increasing the angle of attack
Brakes, aided by spoilers, stop airplanes. Thrust reversers help at high speeds. Having the plane on all gear with the nose wheel steering available makes for directional control. No manufacturer recommends aero-braking for a reason.
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grounded27
If drag alone is going to stop the aeroplane it will need a very long RW.AOA also prduces lift which reduces the friction also the aircraft is skimming with minimal contact with the RW. If aerodynamic breaking worked then why would no Airline recommend it? It will save brake wear,save thrust reverser mentainenece. Actually it is recommended to put nosewheel on ground as soon as possible and apply breaking. Aerodynamic breaking is the least efficient procedure.
If drag alone is going to stop the aeroplane it will need a very long RW.AOA also prduces lift which reduces the friction also the aircraft is skimming with minimal contact with the RW. If aerodynamic breaking worked then why would no Airline recommend it? It will save brake wear,save thrust reverser mentainenece. Actually it is recommended to put nosewheel on ground as soon as possible and apply breaking. Aerodynamic breaking is the least efficient procedure.
Last edited by vilas; 27th May 2013 at 03:26.
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GF
No manufacturer recommends aero-braking for a reason.
So I ask in theory, what do you all think?
Thank you vilas for your 74c input.
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From a theoretical point of view, if you have brakes that work it is a complete waste of time.
As GF says, it was used on high speed fighters that had token brakes, so drag chutes and aerodynamic braking on very long runways brought them down to a speed where the brakes could stop them without overheating.
Idle reverse will give you very similar deceleration rates, so you stop just as quickly with no issues of tailstrike/directional control/pax comfort; and if you have carbon brakes then applying them moderately just after touchdown will stop you quicker for no greater cost than if you use them to make the turnoff at 20 knots.
So all in all, it is just as appropriate to transport aircraft as holding it in ground effect after liftoff to accelerate, and "run and break" joins - great fun for the pilot but of no benefit other than to his ego.
As GF says, it was used on high speed fighters that had token brakes, so drag chutes and aerodynamic braking on very long runways brought them down to a speed where the brakes could stop them without overheating.
Idle reverse will give you very similar deceleration rates, so you stop just as quickly with no issues of tailstrike/directional control/pax comfort; and if you have carbon brakes then applying them moderately just after touchdown will stop you quicker for no greater cost than if you use them to make the turnoff at 20 knots.
So all in all, it is just as appropriate to transport aircraft as holding it in ground effect after liftoff to accelerate, and "run and break" joins - great fun for the pilot but of no benefit other than to his ego.
Last edited by BizJetJock; 27th May 2013 at 04:43. Reason: Spelling
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Come on! It's just for little fun and comfort
Keep the touchdown pitch, apply idle reverse and gently lower the nose before you lost control over it. On long RW you will slow down naturally and with cool brakes. Everybody happy.
Of course you know when to play these games... And, of course, it's nowhere as affective as other braking means.
Keep the touchdown pitch, apply idle reverse and gently lower the nose before you lost control over it. On long RW you will slow down naturally and with cool brakes. Everybody happy.
Of course you know when to play these games... And, of course, it's nowhere as affective as other braking means.
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aerodynamic brake and tail cone
One of or Captain used to land wit very high pitch,much more than the 12° limit in our books. Once after grounding we had alarm "TAIL CONE".
Memory item was to verify if we lost the tail cone. The Captain answerd :"No matter, it is a false alarm".
I said him again "TAIL CONE" and "we have to verify the tail cone who perhaps is on the RWY". He still was sure it was a false alarm , but as I insisted he called the Chief of the Cabin Crew to verify we still had the tail cone, sure it would be a false alarm. He called the TWR to inform them we were staying on the Runway to verify the false alarm. When the stewardess came back she was laughing and said "we are in a decapotable ".
At low speed and high pitch our MD-82 conic shaped tail-cone failed. The new beaver shaped tail-cone of our MD-83s staid connected by a forward depression/lift in the same situation. A truck searched the tail-cone (big and heavy !) in the gras beside the runway where the tail-cone had been rolling. The Tower did not see the tail-cone going away hiden by the fuselage...
Our plane manual said a tail strike risk exist on landing with more than 12° pitch In fact it was the emergency escape removable tail cone (pulling a handle pulling a connection wire) who was going away.
Memory item was to verify if we lost the tail cone. The Captain answerd :"No matter, it is a false alarm". I said him again "TAIL CONE" and "we have to verify the tail cone who perhaps is on the RWY". He still was sure it was a false alarm , but as I insisted he called the Chief of the Cabin Crew to verify we still had the tail cone, sure it would be a false alarm. He called the TWR to inform them we were staying on the Runway to verify the false alarm. When the stewardess came back she was laughing and said "we are in a decapotable ".At low speed and high pitch our MD-82 conic shaped tail-cone failed. The new beaver shaped tail-cone of our MD-83s staid connected by a forward depression/lift in the same situation. A truck searched the tail-cone (big and heavy !) in the gras beside the runway where the tail-cone had been rolling. The Tower did not see the tail-cone going away hiden by the fuselage...
Our plane manual said a tail strike risk exist on landing with more than 12° pitch In fact it was the emergency escape removable tail cone (pulling a handle pulling a connection wire) who was going away.
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Sure it's pretty to watch and fun to do
... but uses a lot more runway, resulting in possible greater brake energy
, than the lowering the nose to the runway technique rather than letting the nose drop to the runway.
By the way, on a light 727-100 less than 80 kts. was my best.
... but uses a lot more runway, resulting in possible greater brake energy, than the lowering the nose to the runway technique rather than letting the nose drop to the runway.By the way, on a light 727-100 less than 80 kts.
was my best.
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Well...if you do choose to keep the nose high and aerodynamically "brake" the plane, you must know that plane well. From memories of the A300 (beautiful plane which I loved) there was a "flight idle" still giving good thrust on our General Electric CF6s and a "ground idle" with much lower N1. And that ground idle was obtained...when the nosewheels were on the ground...(I am going to check, but I am pretty sure of it). Nose wheel high...aerodynamic braking...with a lot of thrust on both engines...not ideal certainly?
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It seems unfortunate that some manage to confuse braking the aeroplane on landing with breaking the aeroplane on landing. You'd think the difference was so extreme it would be noticed!
Lets hope they restrict this potentially career-ending error to their writing and not to their flying...
Lets hope they restrict this potentially career-ending error to their writing and not to their flying...
NARVAL.
Yes. A300 with CF6-50 will stay in flight idle until the nose wheels are on the ground.
Had a case some years ago when both thrust reversers were locked out and the captain said he would use aerodynamic braking to save wear on the brakes.
I advised that since FI was about 5000 lbs of thrust against less than 2000 lbs thrust at GI it might be better to put the nose wheels on the ground. Common sense prevailed.
Yes. A300 with CF6-50 will stay in flight idle until the nose wheels are on the ground.
Had a case some years ago when both thrust reversers were locked out and the captain said he would use aerodynamic braking to save wear on the brakes.
I advised that since FI was about 5000 lbs of thrust against less than 2000 lbs thrust at GI it might be better to put the nose wheels on the ground. Common sense prevailed.
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Just to be clear, this aircraft landed, WOW allowed wing engines to deploy (not sure how much reverse thrust was applied but eng's were in reverse) and rolled out a great length with full flaps at a high AOA. Wish my phone was configed to take a quick video. I am no spring chicken, about 20 years in around the flightline or in flight as a back seat driver, doubt they went 1000ft after the nose met the ground. Thank you all for sharing.
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Isn't there some sort of concern with regards the elevators running out of sufficient authority to smoothly lower the nose, or a horizontal stabiliser stall, leading to slapping the nose down?