Runway excursion by DL MD-80
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Most landings runway length is not critical so brakes are not used until around 80 knots to save on brake wear on my airline. I used the same technique prior to the airlines also.
From reverser deployment to 80 knots small rudder inputs are used to maintain centerline tracking. Crosswinds and assymetrical thrust application would be the main reasons for correction to remain on centerline. This is the time to see the results of a bit of assymetrical thrust to maintain centerline using rudders if necessary to maintain centerline tracking. It will soon become easy and instrinctive so one day when things go south you have that extra tool to bail you out of a situation.
You haven't broken any rules because no pilot can keep perfectly balanced reverse power anyway when most of your attention is directed out the front window.
Obviously it wasn't in this crash causing it from the start.
From reverser deployment to 80 knots small rudder inputs are used to maintain centerline tracking. Crosswinds and assymetrical thrust application would be the main reasons for correction to remain on centerline. This is the time to see the results of a bit of assymetrical thrust to maintain centerline using rudders if necessary to maintain centerline tracking. It will soon become easy and instrinctive so one day when things go south you have that extra tool to bail you out of a situation.
You haven't broken any rules because no pilot can keep perfectly balanced reverse power anyway when most of your attention is directed out the front window.
Obviously it wasn't in this crash causing it from the start.
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ancient mariner
I think you are being sincere and I say , you are welcome.
It may seem odd, but straight and level flying, like in cruise flight, is actually many, very tiny turns, just like when you are driving your car and trying to stay in the lane. Between the lane lines.
One regulation, by way of example, says we are never to get below the glideslope when coming in to land. The regulation goes on to expressly say : except for normal bracketing maneuvers. (that means sort of hunting for the glideslope by searching up and down for the exact center)
We sort of hunt for the exact reverse thrust if it comes in unevenly, and by doing that we gain the "TOUCH" I've been trying to convey.
Feel free to ask any flying questions you like.
I think you are being sincere and I say , you are welcome.
It may seem odd, but straight and level flying, like in cruise flight, is actually many, very tiny turns, just like when you are driving your car and trying to stay in the lane. Between the lane lines.
One regulation, by way of example, says we are never to get below the glideslope when coming in to land. The regulation goes on to expressly say : except for normal bracketing maneuvers. (that means sort of hunting for the glideslope by searching up and down for the exact center)
We sort of hunt for the exact reverse thrust if it comes in unevenly, and by doing that we gain the "TOUCH" I've been trying to convey.
Feel free to ask any flying questions you like.
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Thankyou all who contributed here. Very interesting discussion regarding reverse thrust as directional control in landing phase.
Blanketing of the rudder in DC-9 or MD-80 would that be because of bucket reversers? Question mostly directed to Mr Skyfall, who wanted to answer more questions... ;-D
Blanketing of the rudder in DC-9 or MD-80 would that be because of bucket reversers? Question mostly directed to Mr Skyfall, who wanted to answer more questions... ;-D
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IF the plane's nose is going left, you pull back a little more on the right reverse lever, IF YOU can't maintain aerodynamic or nosewheel control.
What you just said was a setup for loss of control on a slippery runway in a MD 80. If the nose is going left, there is a fair chance your tail is going right.
Go ahead, pull more on the right reverser in direct contradiction with MD and now, Boeings recommendation.
MD drivers know what will happen, you don't.
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Mr Snuggles
It is partly the type of reverser (bucket/clamshell)but also how the airflow comes off the bucket and interrupts the airflow from the forward motion of the plane over the vertical stabilizer and the rudder.
oversimplification: relative wind (from motion of airplane ) moving over vertical fin at 100 knots. Jet Exhaust from bucket reversers moving from opposite direction at 60 knots , so resultant air flow over rudder is 40, not enough to do much. These numbers are for illustration only.
MANAADASYSTEM: fine, tell us what you would do in the situation you indicate. maybe you don't see what is happening? In the delta crack up, there was more reverse thrust on the left engine wasn't there? And the plane left the runway going to the left. Seems that reverse thrust can move the plane, just not used properly in this case.
And I've been to many slippery runways. I flew what EK Gann use to call AM21. Those funny airports on the top side of the US
It is partly the type of reverser (bucket/clamshell)but also how the airflow comes off the bucket and interrupts the airflow from the forward motion of the plane over the vertical stabilizer and the rudder.
oversimplification: relative wind (from motion of airplane ) moving over vertical fin at 100 knots. Jet Exhaust from bucket reversers moving from opposite direction at 60 knots , so resultant air flow over rudder is 40, not enough to do much. These numbers are for illustration only.
MANAADASYSTEM: fine, tell us what you would do in the situation you indicate. maybe you don't see what is happening? In the delta crack up, there was more reverse thrust on the left engine wasn't there? And the plane left the runway going to the left. Seems that reverse thrust can move the plane, just not used properly in this case.
And I've been to many slippery runways. I flew what EK Gann use to call AM21. Those funny airports on the top side of the US
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The trouble with slippery runways is if you're yawing into wind and also drifting downwind reverse, asymmetric, or otherwise is exactly the wrong thing to do as it will exacerbate the downwind drift.
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Reported braking action was good with a strong left crosswind. This appears to be more in line with loss of directional control due to rudder blanking. The slippery runway scenario would have seen them depart off the downwind side of the runway.
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KLGA 051524Z 04007KT 1/4SM R04/2600V2800FT SN FZFG VV009 M03/M04 A3013 RMK AO2 P0004
KLGA 051451Z 03010KT 1/4SM R04/3000V4500FT SN FZFG VV012 M03/M04 A3014 RMK AO2 TWR VIS 3/4 SLP207 P0003 60013 T10281044 53040
An 8 knot crosswind at 130 knots would not cause this accident by itself. A combination of the crosswind and .16 EPR more L reverse and nosewheel not yet on the runway probably will be the cause.
I think everybody agrees using reverse thrust will increase the downwind drift on an icy runway if the plane is angled into the wind but being blown to the downwind side. In this case this didn't happen. The plane left the runway on the upwind side so the plane just had to be straightened out to stay on the runway.
KLGA 051451Z 03010KT 1/4SM R04/3000V4500FT SN FZFG VV012 M03/M04 A3014 RMK AO2 TWR VIS 3/4 SLP207 P0003 60013 T10281044 53040
An 8 knot crosswind at 130 knots would not cause this accident by itself. A combination of the crosswind and .16 EPR more L reverse and nosewheel not yet on the runway probably will be the cause.
I think everybody agrees using reverse thrust will increase the downwind drift on an icy runway if the plane is angled into the wind but being blown to the downwind side. In this case this didn't happen. The plane left the runway on the upwind side so the plane just had to be straightened out to stay on the runway.
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A better way would be to start with l.6 reverse as recomended, not going to full reverse. Now if the rudders can't maintain centerline reduce reverse until the rudder can. If you feel this isn't enough to stay on the runway you have two choices. Continue off the side or at least try opposite reverse because that is all you have left at this point.
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great spooky
have him comment, be sure to read our posts carefully and point out that assymetric reverse thrust was applied at touchdown. we are offering a thought on how to handle things when other methods don't work.
have him comment, be sure to read our posts carefully and point out that assymetric reverse thrust was applied at touchdown. we are offering a thought on how to handle things when other methods don't work.
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I doubt that he will comment outside the borders of officialdom and not being a DC9/MD80 guy myself it's all a mystery to me. I don't recall ever hearing of this regarding the 727? Different design I guess.
I've flown the MD80 and the B727.
Rudder blanking simply wasn't an issue on the 727, it had a huge vertical fin and very effective rudder, much, much bigger than the MD80 and was not affected by any amount of reverse, its handling qualities were simply superb.
The -80 was entirely different, the tail was not much bigger than the DC9 with far bigger engines and the wing wasn't that much bigger either, it was really pushing the aircraft's capability.
It was really just a hodge podge of ideas with the minimal investment by MD, just like the DC10 with all its problems.
Rudder blanking was a serious issue and the test pilots knew it, their recommendations were and are to be taken very seriously and complied with.
They KNEW what they were talking about, unlike a few on this thread.
Rudder blanking simply wasn't an issue on the 727, it had a huge vertical fin and very effective rudder, much, much bigger than the MD80 and was not affected by any amount of reverse, its handling qualities were simply superb.
The -80 was entirely different, the tail was not much bigger than the DC9 with far bigger engines and the wing wasn't that much bigger either, it was really pushing the aircraft's capability.
It was really just a hodge podge of ideas with the minimal investment by MD, just like the DC10 with all its problems.
Rudder blanking was a serious issue and the test pilots knew it, their recommendations were and are to be taken very seriously and complied with.
They KNEW what they were talking about, unlike a few on this thread.
Last edited by stilton; 13th Apr 2015 at 08:27.
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I was very happy to leave the MD80 and fly the B727. I agree, the md80 had a lot of problems as stated. Boeing aircraft, to me, could always be trusted so I stayed with Boeing the rest of my career. I know others feel differently so call it personal preference.
The rudder blanking problem on the MD80 isn't that hard to handle with proper reverse usage. This all or nothing answer using reverse with onset of rudder blanking reminds me of using an axe to trim the hedges when a trimmer would suffice.
The rudder blanking problem on the MD80 isn't that hard to handle with proper reverse usage. This all or nothing answer using reverse with onset of rudder blanking reminds me of using an axe to trim the hedges when a trimmer would suffice.
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reference post number 36,symmetric application of reverse thrust (NOT).
The discussion got off track by misunderstanding what I was getting at. IF you use assymetric thrust you will turn, and if you use it incorrectly you will turn in the wrong direction.
The discussion got off track by misunderstanding what I was getting at. IF you use assymetric thrust you will turn, and if you use it incorrectly you will turn in the wrong direction.
