Cross controls on a 747 or other big jet/turbo prop
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Cross controls on a 747 or other big jet/turbo prop
Hi,
Recently was doing a checkout ride for my PPL. I was practicing a PFL and with about 600 feet to go to my chosen field was hopelessly too high -so did the cross controls technique and dropped like a brick to simulate making the field...
So my question is: Any professional pilots out there performed cross controls on a jet/turbo prop -and whats the sensation/experience like?
Thanks.
Has.
Recently was doing a checkout ride for my PPL. I was practicing a PFL and with about 600 feet to go to my chosen field was hopelessly too high -so did the cross controls technique and dropped like a brick to simulate making the field...
So my question is: Any professional pilots out there performed cross controls on a jet/turbo prop -and whats the sensation/experience like?
Thanks.
Has.
Re: Cross controls on a 747 or other big jet/turbo prop
A Canadian jet (767 methinks) ran out of fuel 10+ years ago and turned into a heavy metal glider. It landed at a disused airstrip. The captain sideslipped it all the way in as they were way too high. He was a former glider pilot and fortunately had his stick and rudder skills intact.
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Re: Cross controls on a 747 or other big jet/turbo prop
I don't think it would be greatly effective or advisable on a 747, but on a 737 Simulator all engines out glide landing practice, I was very high, with the instructor and copilot very amusedly waiting for the inevitable. Full speedbrake and telling them 'I have one more trick up my sleeve!' and doing a strong cross control brouoght us down onto the threshold a treat. No reason why it shouldn't work, but the 747 with full flap would be draggy enough.
Only half a speed-brake
Re: Cross controls on a 747 or other big jet/turbo prop
For swept wing aircraft it is not an approved manouevre. And, anyhow, it is a life saving manouevre (cannot spell it, sorry) for a single but for twins and more you are not supposed to need it because you use the rudder to compensate for the failed engine and keep flying. If attempted, due to much larger rudder authority (constructed to compensate the yawing moment with failed engine) I can imagine the resulting attitude would be much wierder than with full rudder on the aircraft I flew for my PPL. Draw a diagram of a relative wind over a swept wing A/C under cross controlled conditions, think of the leeward side of the fuselage and high lift devices shielded also by the lowered upwind wing and I really think it may depart controlled flight. So no-no. Even if it wouldn't, if the cricitcal engine for that condition failed you would have the sky on your tail. It is all exactly the same. On SE one has a safe emergency site chosen all the time. On ME, you make sure to steer well clear of all situations that you cannot recover from with a failed engine.
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I've done it in swept- and delta-wing jet fighters, but wouldn't risk it in a 747 unless it was a truly "last ditch" maneuver. I can't imagine a situation where an engineless 747 would have too little rate of descent, and the risk of stalling the downwind wing, combined with lack of control authority, would be VERY risky.
That said, realize that to a slight extent that is what we do every time we apply a "wing down, top rudder" crosswind correction for landing. For that purpose (at least to the limits of dragging a pod), cross controls can be an effective tool, when applied judiciously in the right circumstances.
That said, realize that to a slight extent that is what we do every time we apply a "wing down, top rudder" crosswind correction for landing. For that purpose (at least to the limits of dragging a pod), cross controls can be an effective tool, when applied judiciously in the right circumstances.
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KEEP IN MIND that the low wing will now have less sweepback than "normal" (note the relative wind on the planform); while the other wing will have MORE sweepback than normal, AND (assuming a low-wing aircraft) will have the disturbed wake from the fuselage interfering with its lift.
And that is a setup for a nasty stall of the "contaminated" wing. Keep an extra few knots as insurance.
And that is a setup for a nasty stall of the "contaminated" wing. Keep an extra few knots as insurance.
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A Canadian jet (767 methinks) ran out of fuel 10+ years ago and turned into a heavy metal glider. It landed at a disused airstrip. The captain sideslipped it all the way in as they were way too high. He was a former glider pilot and fortunately had his stick and rudder skills intact.
http://www.wadenelson.com/gimli.html
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Guys,
Intruder -thanks for the explanation.
barit1 -cheers for the advice -duely noted.
vapilot -Yes, read the Gimli glider story in a book some years ago and great feat of airmanship to boot!
Rgds.
Has.
Intruder -thanks for the explanation.
barit1 -cheers for the advice -duely noted.
vapilot -Yes, read the Gimli glider story in a book some years ago and great feat of airmanship to boot!
Rgds.
Has.
Transparency International
The Gimli Glider had one thing going for it - with respect to sidegliding - and that was no engines running. 
Jet engines are rather sensitive to the way the intake airflow hit the fan.To willfully introduce a "skewed" intake airflow carries high risk of resulting in a flame-out or surges (backfires). Most manufacturers require that ignition to be on just for flying thru moderate turbulence !
Meanwhile, you've initiated a high rate of descent, dropping like a brick, and now you want to stop the descent. One, maybe two engines inoperative ... you see the problem ?
The way we ovecome your initial problem is the stabelized approach technique. Try the Prune search function (when it comes online again).
Jet engines are rather sensitive to the way the intake airflow hit the fan.To willfully introduce a "skewed" intake airflow carries high risk of resulting in a flame-out or surges (backfires). Most manufacturers require that ignition to be on just for flying thru moderate turbulence !
Meanwhile, you've initiated a high rate of descent, dropping like a brick, and now you want to stop the descent. One, maybe two engines inoperative ... you see the problem ?
The way we ovecome your initial problem is the stabelized approach technique. Try the Prune search function (when it comes online again).
