American Airlines jet goes off runway in Jackson Hole, Wyoming
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The discussion went this way because a well-known poster on here decided to have a bash at AAL over the training programme which emphasised rudder use in upsets, predictably raking over some well-trodden coals in the process - as I'm sure they intended.
So, presumably that could leave the impression that agressive use of the 707 rudder would be okay below 250 kias or even above 250 if the pressured reduced.
It was somewhat academic at my airline since we were never taught to use the rudder for anything other than takeoff or landing or engine failures.
It was somewhat academic at my airline since we were never taught to use the rudder for anything other than takeoff or landing or engine failures.
no airplane is designed to take rapid aggressive oscillating inputs on the rudder [or other flight controls...even below Va...it's a structural issue..in fact from a maximum sideslip condition just centering the rudder imparts massive loads
this conversation is too hot for me so I'll go back to lurking and enjoying...
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What tells us at what time this aircraft finally accepted it was on the ground and released all its airborne lockouts.?
It appears to have reacted for a considerable period of time as though weight was "not" on the main gear and the landing gear bogie's had not passed their tilt on touch down signals....is this a case of a ("the aircraft still thought it was airborne") lack of communication signals due a soft touch contaminated landing aircraft?
It appears to have reacted for a considerable period of time as though weight was "not" on the main gear and the landing gear bogie's had not passed their tilt on touch down signals....is this a case of a ("the aircraft still thought it was airborne") lack of communication signals due a soft touch contaminated landing aircraft?
this conversation is too hot for me so I'll go back to lurking and enjoying...
Think I'll stick with the thread topic myself...
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bearfoil
The touchdown was slightly prior to the PAPI lights -- how much shorter would you recommend?
And how would a "plant" vice "greaser" affect truck tilt sensors?
I still think the F/O was looking for a greaser when he should have been wanting a plant.
The touchdown was slightly prior to the PAPI lights -- how much shorter would you recommend?
And how would a "plant" vice "greaser" affect truck tilt sensors?
Last edited by Zeffy; 7th Jan 2011 at 00:01. Reason: added truck tilt sensor link
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Touchdown. Touch Down Point. Two separate though related aspects of flight.
Tilt sensors. Squat switch. Two separate though related devices.
Plant. Float. Two variations of an aircraft's arrival
Thrust Reverser. Braking. Two separate but related aspects of slowing
Tilt sensors. Squat switch. Two separate though related devices.
Plant. Float. Two variations of an aircraft's arrival
Thrust Reverser. Braking. Two separate but related aspects of slowing
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Yes I agree with Zeffy, how would the touchdown have affected the truck tilt? These are not squat (compression) sensors, they are tilt sensors as I pointed out in post #53.
Provided the speedbrakes are armed, they will deploy as soon as the truck untilts, and this will happen once the gear touches the ground. If the speedbrake is not armed, or if it fails to deploy, then manual speedbrake would be necessary.
For a planned landing with automatic speedbrake inoperative and that is on on a dry runway at ISA, you would be looking at another 850 feet landing distance or a performance degradation equivalent to a mass increment of around 16,000kg. That still assumes that speedbrakes will be deployed manually after touchdown.
The reversers on the 757 can occaisionally be awkward to get through the lever interlock position, and the reverse levers may well be re-cycled in order to achieve the desired result. If one or both reversers are selected through to reverse idle, the speedbrakes (all 12 spoiler panels) will drive up irrespective of the lever position being armed or down.
In the normal course of events, the only time you wouldn't get spoilers after touchdown assuming no indication of "spoilers" or "auto speedbrake" on the EICAS / Discreet warning system prior to touchdown, would be if you selected or left the speedbrake lever in the "Down" position, didn't then deploy them manually after touchdown, and couldn't achieve reverse thrust.
That is not to imply that any of that happened in this incident, but simply to provide some information.
Provided the speedbrakes are armed, they will deploy as soon as the truck untilts, and this will happen once the gear touches the ground. If the speedbrake is not armed, or if it fails to deploy, then manual speedbrake would be necessary.
For a planned landing with automatic speedbrake inoperative and that is on on a dry runway at ISA, you would be looking at another 850 feet landing distance or a performance degradation equivalent to a mass increment of around 16,000kg. That still assumes that speedbrakes will be deployed manually after touchdown.
The reversers on the 757 can occaisionally be awkward to get through the lever interlock position, and the reverse levers may well be re-cycled in order to achieve the desired result. If one or both reversers are selected through to reverse idle, the speedbrakes (all 12 spoiler panels) will drive up irrespective of the lever position being armed or down.
In the normal course of events, the only time you wouldn't get spoilers after touchdown assuming no indication of "spoilers" or "auto speedbrake" on the EICAS / Discreet warning system prior to touchdown, would be if you selected or left the speedbrake lever in the "Down" position, didn't then deploy them manually after touchdown, and couldn't achieve reverse thrust.
That is not to imply that any of that happened in this incident, but simply to provide some information.
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After the Little Rock crash all 757 crews verifiy spoiler deployment on touchdown or manually deployed them. The video showed a solid touchdown before the thousand ft. point. Landing long was not the problem on the overrun. Something didn't allow the reversers to work. Also braking action should have worked by itself if the reversers were inop. Something happened to the brakes or braking action was nil.
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Beazlebub, I take it that you've got some experience with the 757; I do not. Can you confirm or deny that reversers, groundspoilers and brakes need the throttles in the idle position to operate correctly? I read it was so on another forum but haven't confirmed it here. Thanks in advance.
Best,
GC
Best,
GC
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Physically the thrust levers must be in idle for the reverser levers to be moved through the interlock position. This is in addition to the aircraft being on the ground with the main trucks untilted.
The spoilers will operate once the main gear trucks untilt. This assumes they are armed. If the thrust levers are advanced on the ground the lever and spoiler panels will move to the down position (retract.) Of course they can be manually activated at any time, and irrespective of any other condition. In other words "you want them, you've got them!" Thrust levers idle or full, they can be manually deployed.
The brakes will operate whenever you press them. Autobrake will disarm if the throttles are advanced on the ground.
As has been mentioned above, the two main items for the PNF (NHP) to monitor on the ground are: That the spoilers deploy (speedbrake lever moves to the up position,) and that the the Autobrakes (if used) don't disarm. In either case manual input would be required from the PF (HP.)
The spoilers will operate once the main gear trucks untilt. This assumes they are armed. If the thrust levers are advanced on the ground the lever and spoiler panels will move to the down position (retract.) Of course they can be manually activated at any time, and irrespective of any other condition. In other words "you want them, you've got them!" Thrust levers idle or full, they can be manually deployed.
The brakes will operate whenever you press them. Autobrake will disarm if the throttles are advanced on the ground.
As has been mentioned above, the two main items for the PNF (NHP) to monitor on the ground are: That the spoilers deploy (speedbrake lever moves to the up position,) and that the the Autobrakes (if used) don't disarm. In either case manual input would be required from the PF (HP.)
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unexpected nil braking action would of course explain quite a bit...if so, if there was no warning, then we should credit the crew with keeping the plane on centerline through the adventure..
I recall one landing at KBUF where the runway was fine, but the captain ( I was f/o at the time...many years ago) took the highspeed and we were skating on ice...max reverse on the taxiway got us under control again...but PHYSICS IS PHYSICS.
I recall one landing at KBUF where the runway was fine, but the captain ( I was f/o at the time...many years ago) took the highspeed and we were skating on ice...max reverse on the taxiway got us under control again...but PHYSICS IS PHYSICS.
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The spoilers will operate once the main gear trucks untilt. This assumes they are armed.
Boeing 757 Flight Controls :: Spoilers & Speedbrakes
Speedbrakes AUTO Operation
On the ground, the speedbrake lever is driven aft to the UP position and the spoiler panels are fully extended, when either:
•there is hydraulic pressure to both Landing Gear truck tilt actuators and
•the landing gear is fully on the ground (both Truck Tilt Sensors not tilted) and
•both Thrust Levers are at idle or
•either reverse thrust lever is moved to the reverse idle detent.
The speedbrake lever does not need to be in the ARMED position for automatic operation to occur.
On the ground, the speedbrake lever is driven aft to the UP position and the spoiler panels are fully extended, when either:
•there is hydraulic pressure to both Landing Gear truck tilt actuators and
•the landing gear is fully on the ground (both Truck Tilt Sensors not tilted) and
•both Thrust Levers are at idle or
•either reverse thrust lever is moved to the reverse idle detent.
The speedbrake lever does not need to be in the ARMED position for automatic operation to occur.
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The speedbrake lever does not need to be in the ARMED position for automatic operation to occur.
For training purposes etc. touch and go landings are normally performed with the speedbrake lever down (disarmed) so that the speedbrakes do not deploy on touchdown.
"It (nil braking action) wouldn't explain of itself the failure of spoiler deployment,..."
However, failure of spoiler deployment might explain nil (or reduced) braking action: No spoilers = more residual wing lift = less weight/force holding the wheels tight to the ground for friction.
Seems to me that thus far, what we may know, from the "proxy FDR" (the video), is that the supplementary deceleration devices - TR and maybe spoilers - did not function as expected, at least in terms of timeliness.
What we don't know is: whether that abnormal function was due to mechanical problems, including perhaps a sticky TR lever. Or crew errors in the operation of the devices. Or anything at all about the actual braking (auto? armed?, setting?, surface condition?)
Or both - I can imagine a scenario (out of many) where in the midst of a challenging approach to a challenging runway, the spoilers didn't get armed. Which might have been easily noted and corrected during the roll-out except for the distraction of recalcitrant thrust levers at the same time.
I find the bashing and defense of American to both be premature at this point - except for the fustercluck surrounding the handling of the FDR data.
However, failure of spoiler deployment might explain nil (or reduced) braking action: No spoilers = more residual wing lift = less weight/force holding the wheels tight to the ground for friction.
Seems to me that thus far, what we may know, from the "proxy FDR" (the video), is that the supplementary deceleration devices - TR and maybe spoilers - did not function as expected, at least in terms of timeliness.
What we don't know is: whether that abnormal function was due to mechanical problems, including perhaps a sticky TR lever. Or crew errors in the operation of the devices. Or anything at all about the actual braking (auto? armed?, setting?, surface condition?)
Or both - I can imagine a scenario (out of many) where in the midst of a challenging approach to a challenging runway, the spoilers didn't get armed. Which might have been easily noted and corrected during the roll-out except for the distraction of recalcitrant thrust levers at the same time.
I find the bashing and defense of American to both be premature at this point - except for the fustercluck surrounding the handling of the FDR data.