Early reverse?
Thread Starter
Early reverse?
Hi,
as it is the first time I notice this situation I wonder how often it happens:
Photos: Airbus A330-343 Aircraft Pictures | Airliners.net
Reverse deployed at touchdown (or even earlier given the deploy time)
as it is the first time I notice this situation I wonder how often it happens:
Photos: Airbus A330-343 Aircraft Pictures | Airliners.net
Reverse deployed at touchdown (or even earlier given the deploy time)
As I recall, most large commercial (& probably military as well) aircraft have an automation pilot aid that the spoilers and/or thrust reversers can be armed to deploy automatically as load comes onto the main landing gear. I believe this is to cut down on pilot workload in gusty conditions to cut the lift and/or thrust to make sure that the plane remains stuck to the runway when it lands rather than have it balloon up or bounce on landing.
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Actually, quite common.
Many, if not most, commuter and transport category aircraft will approach with power but slowly reduce to idle during the flare, the intent being to touchdown as you reach idle, assuming the conditions allow for it. The automation that Donkey497 speaks of is spoilers and other lift dump devices. I've also never heard of auto-reverse, but who knows - way too many types to say it doesn't exist somewhere.
But, once the wheels touch down its a simple matter of engaging the thrust reverse - be it jets or propellers. If the aircraft was landed at idle this is relatively quick (no more than a second or so to get the process started).
If the aircraft was not landed at idle there will be a delay. Considering a little bit of power is often used to "cushion" the landing, this is probably why you've not seen it a lot.
Now, depending on engine and aircraft configuration, there can be a bit of a pitch change when reverse is engaged prior to nose wheel touchdown, so it does need to be managed properly; but, it's actually easy to do once you get the hang of it for your specific type.
Many, if not most, commuter and transport category aircraft will approach with power but slowly reduce to idle during the flare, the intent being to touchdown as you reach idle, assuming the conditions allow for it. The automation that Donkey497 speaks of is spoilers and other lift dump devices. I've also never heard of auto-reverse, but who knows - way too many types to say it doesn't exist somewhere.
But, once the wheels touch down its a simple matter of engaging the thrust reverse - be it jets or propellers. If the aircraft was landed at idle this is relatively quick (no more than a second or so to get the process started).
If the aircraft was not landed at idle there will be a delay. Considering a little bit of power is often used to "cushion" the landing, this is probably why you've not seen it a lot.
Now, depending on engine and aircraft configuration, there can be a bit of a pitch change when reverse is engaged prior to nose wheel touchdown, so it does need to be managed properly; but, it's actually easy to do once you get the hang of it for your specific type.
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If the A340 is anything like the 744, the tilt switches in the main gear will unlock the reversers. Not even all the main gear have to touch down before reversers can be opened.
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There may be weight-on-wheels and thrust lever idle logic (as a minimum) to enable the thrust reversers to be deployed but there is no auto-reverse. It is a purely manual selection, unlike auto spoilers or auto brakes.
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Not quite in the same league, size-wise, the Pilatus Turbo Porter could be put into beta mode (not exactly reverse, but similar effect) while in flight; the Sultan of Oman's Air Force, back in the '70s/'80s at least, employed this technique to achieve unbelievably steep approaches with a a "landing run" of 10m or less. (I think it was beta rather than reverse, but memory fades, as usual.)
I can vouch for the fact that for a right-hand seat ex-pongo passenger it was a truly terrifying experience, which greatly amused the monosyllabic and hungover Polish pilot doing it, one morning at daybreak at an abandoned and very sandy strip about 100 miles SW of Nizwa.
I can vouch for the fact that for a right-hand seat ex-pongo passenger it was a truly terrifying experience, which greatly amused the monosyllabic and hungover Polish pilot doing it, one morning at daybreak at an abandoned and very sandy strip about 100 miles SW of Nizwa.
Last edited by Capot; 14th Feb 2016 at 10:16.
I also remember the Turbo Porters in Oman.
One National Day Parade, two Porters flying with three helicopters did a spot landing in front of the Sultan. There was about 20 kts of wind to help but I dont think the wheels even revolved once.
Actually nothing to do with beta or reverse, just very slow flying.
One National Day Parade, two Porters flying with three helicopters did a spot landing in front of the Sultan. There was about 20 kts of wind to help but I dont think the wheels even revolved once.
Actually nothing to do with beta or reverse, just very slow flying.
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From the photo it seems the T/R's might have been activated before touchdown. There is the puff of wheel smoke, the nose wheel is off the ground and it takes time for T/R's to open. I hope this was an automatic deployment.
The reason I say that is that I used to see many F/O's start the flare closing the thrust levers and then complete the flare, a/c still off the ground, with their hands on the T/R's.
I use to discuss this along the lines of 'conditioning the brain'. IMHO if you have your hands on the T/R's, in the flare, you are in a slightly nervous/aroused state of mind. There is a pre-conceived idea that you have to stop ASAP. This was not a relaxed state and usually led to hard landings as well. Quite unnecessary. If the calculations have been made and correct technique employed then all is cool.
I used to ask "when is the latest time you can make a GA?" Correctly, "after TR's are deployed." OK, "so you are floating and eating up runway and your hands are on TR's with brain in must land mode. Is that safe & healthy?" "Er, no." "So you select TR's when you have decided you want to stay on the ground."
Pulling TR's (B737) releases the auto brakes and gives same acceleration, so what's the rush?
Can an AB pilot confirm if there is an auto function for TR's?
The reason I say that is that I used to see many F/O's start the flare closing the thrust levers and then complete the flare, a/c still off the ground, with their hands on the T/R's.
I use to discuss this along the lines of 'conditioning the brain'. IMHO if you have your hands on the T/R's, in the flare, you are in a slightly nervous/aroused state of mind. There is a pre-conceived idea that you have to stop ASAP. This was not a relaxed state and usually led to hard landings as well. Quite unnecessary. If the calculations have been made and correct technique employed then all is cool.
I used to ask "when is the latest time you can make a GA?" Correctly, "after TR's are deployed." OK, "so you are floating and eating up runway and your hands are on TR's with brain in must land mode. Is that safe & healthy?" "Er, no." "So you select TR's when you have decided you want to stay on the ground."
Pulling TR's (B737) releases the auto brakes and gives same acceleration, so what's the rush?
Can an AB pilot confirm if there is an auto function for TR's?
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From the photo it seems the T/R's might have been activated before touchdown.
Can an AB pilot confirm if there is an auto function for TR's?
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It's a trick of the photograph.
The A330 has a twin axle bogie which is tilted on the approach with the rear axle lowest. See photo of the same aircraft here.
The sequence of events is rear axle touches down, spoilers deploy automatically and the reverse can be deployed. This can all happen before the front axle touches down. If you look at the photo, the tyre smoke is coming from the forward axle, not the rear and there is no tyre smoke visible from the first touchdown, so it must have happened further back down the runway, which is when the reversers were deployed.
FF
The A330 has a twin axle bogie which is tilted on the approach with the rear axle lowest. See photo of the same aircraft here.
The sequence of events is rear axle touches down, spoilers deploy automatically and the reverse can be deployed. This can all happen before the front axle touches down. If you look at the photo, the tyre smoke is coming from the forward axle, not the rear and there is no tyre smoke visible from the first touchdown, so it must have happened further back down the runway, which is when the reversers were deployed.
FF
Some pilots will lift the reverse levers after they move the throttles to idle as they flare - so the reversers will deploy as soon as 'on-ground' is true. We've shown DFDR data to pilots who denied they were doing this until we showed them the data
The regulators hate this since an air/ground fault could cause a low altitude reverser deployment that could easily result in an unhappy ending (on most big fan engines, a deployed reverser pretty much destroys the lift on that wing, so that wing drops like a rock). Latest EASA regulations call for something we call the 'hand slapper' - if the thrust lever is moved into the reverse quadrant before air/ground says ground, we have to pop an (EICAS) message (Boeing world obviously).
The regulators hate this since an air/ground fault could cause a low altitude reverser deployment that could easily result in an unhappy ending (on most big fan engines, a deployed reverser pretty much destroys the lift on that wing, so that wing drops like a rock). Latest EASA regulations call for something we call the 'hand slapper' - if the thrust lever is moved into the reverse quadrant before air/ground says ground, we have to pop an (EICAS) message (Boeing world obviously).
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Dunno 'bout the rest of the "Boeing world", but the 747 air/ground systems (-100 through -8) PREVENT moving the reverse levers until ground sensing (main/body gear tilt), so the 'hand slapper' is unnecessary.
Oh, I worked the 747 thrust levers - I do know what I'm talking about.
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I was always under the impression that on the 727 you could place the thrust levers into reverse anytime you wanted, there was no lock-out logic on the throttles.
Now I admit I never tried to get reverse thrust in flight in the actual aircraft. Did on a bet* in a sim and got reverse thrust.
* The bet was 10,000ft AGL five miles from the end of the runway at LAX, clean and 250 kts indicated. Land in the touchdown zone, on speed. Did it the first time. Spoilers out, reverse all three engines at the same time you call for gear down, flaps down schedule.
And I'll admit that the two other guys in the sim were liberal with what constituted the 'touch down zone'.
Now I admit I never tried to get reverse thrust in flight in the actual aircraft. Did on a bet* in a sim and got reverse thrust.
* The bet was 10,000ft AGL five miles from the end of the runway at LAX, clean and 250 kts indicated. Land in the touchdown zone, on speed. Did it the first time. Spoilers out, reverse all three engines at the same time you call for gear down, flaps down schedule.
And I'll admit that the two other guys in the sim were liberal with what constituted the 'touch down zone'.
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