Southwest B737 Overrun @ Chcago MDW
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Rather be flying:
I think your point about aft yoke working as long at the nose wheel stays down is important. You must assume that the nose wheel strut is compressed and that it doesn't change for aft yoke to work. If the nose strut compression changes at all, the AOA will change, thus working against you.
regards,
flybubba
I think your point about aft yoke working as long at the nose wheel stays down is important. You must assume that the nose wheel strut is compressed and that it doesn't change for aft yoke to work. If the nose strut compression changes at all, the AOA will change, thus working against you.
regards,
flybubba
fb
I suspect that during heavy braking and reverse there is a surplus of force to keep the nosewheel strut fully compressed and the AOA constant.
Until back stick reduces that force below the force to keep it fully compressed, it ain't gonna come up and the AOA will stay put.
Certainly the downforce on the nosewheel strut varies with a/c type, weight, cg, speed, trim/elevator position, spoilers, braking couple, reverser couple.... those with the data might be able to work out the moments and couples and put it into tables. This data may or may not be in the simulator software -- it would be interesting to know.
The institutional question is what does / can a line pilot do with this technique until the manufacturer, authorities and airlines work it into the SOPs and distances.
I don't really think this is a technique that should be used by dispatch to shave margins further. I'd rather keep it in the back pocket for when something extra is needed to stop before going off the end because the runway ain't what I was expecting.
regards,
rbf
I suspect that during heavy braking and reverse there is a surplus of force to keep the nosewheel strut fully compressed and the AOA constant.
Until back stick reduces that force below the force to keep it fully compressed, it ain't gonna come up and the AOA will stay put.
Certainly the downforce on the nosewheel strut varies with a/c type, weight, cg, speed, trim/elevator position, spoilers, braking couple, reverser couple.... those with the data might be able to work out the moments and couples and put it into tables. This data may or may not be in the simulator software -- it would be interesting to know.
The institutional question is what does / can a line pilot do with this technique until the manufacturer, authorities and airlines work it into the SOPs and distances.
I don't really think this is a technique that should be used by dispatch to shave margins further. I'd rather keep it in the back pocket for when something extra is needed to stop before going off the end because the runway ain't what I was expecting.
regards,
rbf
I don't know if this has anything to do with the price of butter but I do remember an overrun accident at LAX involving a DC-10 which abandoned take-off at a fairly high speed.
The SOP in such an event was for the PNF to apply stick pressure "forward of neutral" to ensure good nosewheel contact.
On this occasion, the PNF stuffed the control column fully forward into the instrument panel (a matter of interpretation)?
The horizontal stabiliser on the DC-10 had the same wing span as a DC-3. This had the result of raising the tail to the extent that the main gear trucks were lifted off the ground initially and so the braking action was considerably less than the performance engineers had imagined.
You will be astonished to learn that the aircraft ended up in the overrun and an emergency evacuation was the result. Fortunately I believe there was only one casualty.
I therefore have found it valuable to brief my F/Os exactly where I want them to put the control column vis a vis fore and aft as well as into wind etc for every take-off or on landing when they take the control column on a rejected take-off or at 80 knots on landing.
The SOP in such an event was for the PNF to apply stick pressure "forward of neutral" to ensure good nosewheel contact.
On this occasion, the PNF stuffed the control column fully forward into the instrument panel (a matter of interpretation)?
The horizontal stabiliser on the DC-10 had the same wing span as a DC-3. This had the result of raising the tail to the extent that the main gear trucks were lifted off the ground initially and so the braking action was considerably less than the performance engineers had imagined.
You will be astonished to learn that the aircraft ended up in the overrun and an emergency evacuation was the result. Fortunately I believe there was only one casualty.
I therefore have found it valuable to brief my F/Os exactly where I want them to put the control column vis a vis fore and aft as well as into wind etc for every take-off or on landing when they take the control column on a rejected take-off or at 80 knots on landing.
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ysatis sez:
I think this discussion is more along the lines of observing differences in mfgr's recommendations, and reconciling these with Newtonian physics.
Of course - if you merely want to fly "by the book" and ignore the physics, my best to you...
That you start wondering about physic laws rather than simply applying manufacturer recommendations, humm questionnable.
Of course - if you merely want to fly "by the book" and ignore the physics, my best to you...
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Backstick for Braking on Contaminated Runways
I don't really think this is a technique that should be used by dispatch to shave margins further. I'd rather keep it in the back pocket for when something extra is needed to stop before going off the end because the runway ain't what I was expecting.
a. Haven't been able to reconcile the aerodynamics
b. Slavishly adhere to manufacturer recommendations only
c. Can't believe that (if it's a fact) somebody would've been recommending it already
OR
d. prefer a free-floating control column under braking as a safer form of non-commital (with concessions for some aileron into any crosswind)
...............then we have some believers.
But I personally wouldn't leave it until the end was looming fast BEFORE deciding to adopt this braking technique (i.e. suck the stick back into my gut and expect a miracle turnaround in my stopping power). I'm instead guessing that it's best used early and throughout - to avoid those "looming situations"
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Airbubba,
quote..."Uh, this is pretty much boilerplate everywhere I've ever worked. What do you propose? Ducking under a couple of dots to hit brick one?"
Err...don't you mean "shingle one?".
Cheers, dd.
quote..."Uh, this is pretty much boilerplate everywhere I've ever worked. What do you propose? Ducking under a couple of dots to hit brick one?"
Err...don't you mean "shingle one?".
Cheers, dd.
What about the fact that the Midway Controllers only allowed approaches with a tailwind to a snow-covered runway?
If this was true, then it made no sense, that the airport could not be "turned around", so to speak.
Would an aircraft need to declare an emergency in order to land at MDW (on snow) with a headwind?
It makes no sense that the only option was to divert to nearby O'Hare Airport-but it was a good option, as long as they had decent (jet), new braking action reports.
How will the NTSB factor the MDW tailwind only operation into the cause of the accident?
If this was true, then it made no sense, that the airport could not be "turned around", so to speak.
Would an aircraft need to declare an emergency in order to land at MDW (on snow) with a headwind?
It makes no sense that the only option was to divert to nearby O'Hare Airport-but it was a good option, as long as they had decent (jet), new braking action reports.
How will the NTSB factor the MDW tailwind only operation into the cause of the accident?
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If this was true, then it made no sense, that the airport could not be "turned around", so to speak.
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Various news media in the states are reporting that the approach and landing were accomplished under an FAA Waiver (published mins 3/4 - weather was at 1/2).
Does anyone know specifically which waiver authorized this?
Thanks in advance (no, I'm not a journo).
Does anyone know specifically which waiver authorized this?
Thanks in advance (no, I'm not a journo).
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>>Various news media in the states are reporting that the approach and landing were accomplished under an FAA Waiver (published mins 3/4 - weather was at 1/2).
I think they had at least RVR 4000 according to the wx sequences earlier in this thread, that would give them published mins on a RW 31C ILS without a waiver I believe.
I think they had at least RVR 4000 according to the wx sequences earlier in this thread, that would give them published mins on a RW 31C ILS without a waiver I believe.
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Various news media in the states are reporting that the approach and landing were accomplished under an FAA Waiver (published mins 3/4 - weather was at 1/2).
Does anyone know specifically which waiver authorized this?
Does anyone know specifically which waiver authorized this?
If I recall correctly, the guy at ATA who led the charge on developing the new procedure for ATA had been recently been hired away from FAA. I'm sure that Googling various terms would probably result in a press release...
Paper Tiger-yeah, that looks familiar. But with those weather conditions, could they not vector planes with different intercept angles, or give a go-around from ORD 14R with an immediate right turn etc?
Last edited by Ignition Override; 26th Dec 2005 at 05:51.
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The landing performance penalty is only in the AIII mode. You can do the ILS-Z at MDW in the IMC mode with no landing penalty. That is because the AIII mode is the only mode that has a flare command.
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Stick position on braking
As one of the "holdouts", may I just point out that the recommended procedure on many of my company's products is to apply some (not full) forward stick force to ensure that the nosewheel does not lift when braking and applying reverse thrust. Those people convinced that they can apply back force without raising the nose at all can perhaps ponder this piece of advice - which has been validated during several flight test programmes and is not in the recommended procedures because we were bored and wanted to fill some white space in the books.
Explaining post-accident why you decided to do something different to, or contrary to, the manufacturer's recommendations would be, I suspect, an unpleasant experience. Especially if it were shown that your inventiveness had contributed to the event. (For example, you're probably postulating this technique for contam runways; what about with a xwind component? Won't be fun if you start to unload the nosewheel and lose steering. Going off the side of the runway is no better than off the end)
Explaining post-accident why you decided to do something different to, or contrary to, the manufacturer's recommendations would be, I suspect, an unpleasant experience. Especially if it were shown that your inventiveness had contributed to the event. (For example, you're probably postulating this technique for contam runways; what about with a xwind component? Won't be fun if you start to unload the nosewheel and lose steering. Going off the side of the runway is no better than off the end)
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>>As one of the "holdouts", may I just point out that the recommended procedure on many of my company's products is to apply some (not full) forward stick force to ensure that the nosewheel does not lift when braking and applying reverse thrust.
I have to agree, this is what most of us do in the real world...
I have to agree, this is what most of us do in the real world...
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I had the great pleasure of knowing a very fine pilot named Bill Giannotti. He used to teach pilots how to fly B17's and B24's during ww2.
He was giving me my checkride for CFI way back when and the subject of pulling back or pushing forward came up to get best braking.
its as simple as this. if you are flying a big modern jet, get on the ground, get your spoilers out and push forward a bit, reverse and brakes. having flown a jet that when selecting reverse the nose would come up ,this is good advice.
if you are flying a light single or twin (think piper arrow or seneca) get down, retract flaps and pull back a bit.
I have also flown the 737 (into midway too) I would plant it, make sure spoilers deployed, keep the nose down and get on brakes and reversers pronto especially that snowy night. IF YOU ARE NOT STOPPING firewall reverse (risking some damage to engines, compressor stalls, even kicking up sooooo much snow you might not see) and hold brakes until the anti skid cycles and keep on them to a complete stop.
Normal stopping has reverse out and not on the brakes till about 100 knots, increase brakes as you bring the engines to idle, be sure you are at idle before cancelling reverse.
sadly, there are visual illusions that might make a pilot think he is slowing down, when this happens a pilot MIGHT, repeat MIGHT cancell reverse too early.
sometimes you have to keep reverse till you are going backwards ;-)
jon
He was giving me my checkride for CFI way back when and the subject of pulling back or pushing forward came up to get best braking.
its as simple as this. if you are flying a big modern jet, get on the ground, get your spoilers out and push forward a bit, reverse and brakes. having flown a jet that when selecting reverse the nose would come up ,this is good advice.
if you are flying a light single or twin (think piper arrow or seneca) get down, retract flaps and pull back a bit.
I have also flown the 737 (into midway too) I would plant it, make sure spoilers deployed, keep the nose down and get on brakes and reversers pronto especially that snowy night. IF YOU ARE NOT STOPPING firewall reverse (risking some damage to engines, compressor stalls, even kicking up sooooo much snow you might not see) and hold brakes until the anti skid cycles and keep on them to a complete stop.
Normal stopping has reverse out and not on the brakes till about 100 knots, increase brakes as you bring the engines to idle, be sure you are at idle before cancelling reverse.
sadly, there are visual illusions that might make a pilot think he is slowing down, when this happens a pilot MIGHT, repeat MIGHT cancell reverse too early.
sometimes you have to keep reverse till you are going backwards ;-)
jon