Emergency Descent: Lowering landing gear
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Emergency Descent: Lowering landing gear
Hi
Not mentioned in the manias but would you ever lower the landing gear.
Maybe structural integrity in doubt, hold speed, increase descent rate?
Thank you
Not mentioned in the manias but would you ever lower the landing gear.
Maybe structural integrity in doubt, hold speed, increase descent rate?
Thank you
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In the old days one turboprop I flew had a slow speed descent option,
Flight Idle. hold level and let speed come back and take gear and full flap at the appropriate speeds then hold the flap limit speed. You spend longer at altitude but have a much steeper descent angle. Really it was only likely if you were on fire and the airport was right underneath you, or you were in really high mountains and knew you were over the valley floor. The preferred descent for things like depressurisation was still VMo/MMo or current speed if damage suspected.
All the jets I've been on are clean descent (speed brake excepting)
Flight Idle. hold level and let speed come back and take gear and full flap at the appropriate speeds then hold the flap limit speed. You spend longer at altitude but have a much steeper descent angle. Really it was only likely if you were on fire and the airport was right underneath you, or you were in really high mountains and knew you were over the valley floor. The preferred descent for things like depressurisation was still VMo/MMo or current speed if damage suspected.
All the jets I've been on are clean descent (speed brake excepting)
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The most important thing with any emergency descent (Real or practice), is to get the face mask on ASAP. In a bad case you may need to sort out your reading glasses next if they got blown off!
After sorting out the O2 and vis situation, just follow the AFM which does vary from type to type.
Flight idle, speed brakes if fitted and 30 to 45 degrees of bank are common actions, BUT most jet AFM's say leave the gear up.
Part of the reason for that is the risk of an overspeed jamming it down, cos it would not be good to finish up at 10K with the gear down halfway across an ocean trying to figure out if you have enough fuel left to make an alternate.
After sorting out the O2 and vis situation, just follow the AFM which does vary from type to type.
Flight idle, speed brakes if fitted and 30 to 45 degrees of bank are common actions, BUT most jet AFM's say leave the gear up.
Part of the reason for that is the risk of an overspeed jamming it down, cos it would not be good to finish up at 10K with the gear down halfway across an ocean trying to figure out if you have enough fuel left to make an alternate.
on the A330 the maximum FL for Gear extension is FL210.
I've been told that the gear won't extend above that even if you try although I've just looked in the FCOM DSC and cannot find any reference saying that?
I'm not going to try above FL210 and let you know
I've been told that the gear won't extend above that even if you try although I've just looked in the FCOM DSC and cannot find any reference saying that?
I'm not going to try above FL210 and let you know
wIzofuz and Meikleour,
Same for the VC10 too.
Same for the VC10 too.
As I recall it, Boeing procedure was to fly level waiting to reach gear limit speed, then select gear down and descend at gear limit speed with full speed brakes. This was on B707 and B747 classic for many years.
The big down side here is what if there is some airframe damage and you lose hydraulics during the descent? The Pacific is a big ocean and you're screwed if you cannot raise the gear when you level off.
The times to F140 are close to the same with gear down/gear limit speed or gear up/Vmo as I recall it. The thing which persuades me that gear up/Vmo is a better option is that you start to lose altitude almost at once rather than wait for the speed to wash off. This means that you are getting your pax into a more benign environment quicker.
The big down side here is what if there is some airframe damage and you lose hydraulics during the descent? The Pacific is a big ocean and you're screwed if you cannot raise the gear when you level off.
The times to F140 are close to the same with gear down/gear limit speed or gear up/Vmo as I recall it. The thing which persuades me that gear up/Vmo is a better option is that you start to lose altitude almost at once rather than wait for the speed to wash off. This means that you are getting your pax into a more benign environment quicker.
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At usual cruise altitudes on the 737 (I know it wasn't a 737 specific question) you are already below the gear limiting speed so there shouldn't be much of a delay, if any at all, to the initiation of the descent.
On the OG and the NG there is a significant increase in RoD with the gear down, especially at higher speeds.
On the OG and the NG there is a significant increase in RoD with the gear down, especially at higher speeds.
If you can get hold of a copy of 'Handling the Big Jets' by D. P. Davies, there is a very good discussion on just these points. On pages 156 - 159 he discusses emergency descents in general and the relative advantages of gear up vv gear down, and, then on pages 283 - 286, he discusses the 747 Classic.
There are a number of considerations to be taken into account. First, if you use the gear down method, you will probably need to stay at altitude for around 20 to 30 seconds while you decelerate to the gear lowering limiting speed whereas, as others have mentioned on this thread, it is probably better to start going down immediately. Second, you will need to consider the possibility of reduced structural integrity therefore descending at a slower speed may be a good idea. Third, as has been mentioned by mustafagander, if you have any doubts about the hydraulic system and the ability to raise the gear again, and you are way out over the ocean, you wouldn't want to have the range compromised by the drag of the gear remaining down.
All these are command decisions that can only be made at the time!
There are a number of considerations to be taken into account. First, if you use the gear down method, you will probably need to stay at altitude for around 20 to 30 seconds while you decelerate to the gear lowering limiting speed whereas, as others have mentioned on this thread, it is probably better to start going down immediately. Second, you will need to consider the possibility of reduced structural integrity therefore descending at a slower speed may be a good idea. Third, as has been mentioned by mustafagander, if you have any doubts about the hydraulic system and the ability to raise the gear again, and you are way out over the ocean, you wouldn't want to have the range compromised by the drag of the gear remaining down.
All these are command decisions that can only be made at the time!
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The 777/787 FCTM Manoeuvres section has this to say:
The rapid descent is normally made with the landing gear up. However, when structural integrity is in doubt and airspeed must be limited, extension of the landing gear may provide a more satisfactory rate of descent.
If the landing gear is to be used during the descent, comply with the landing gear placard speeds.
The rapid descent is normally made with the landing gear up. However, when structural integrity is in doubt and airspeed must be limited, extension of the landing gear may provide a more satisfactory rate of descent.
If the landing gear is to be used during the descent, comply with the landing gear placard speeds.
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Normally this (gear down) is not required, however:
If you have for instance an "older" 737 NG (-600/-700) wing aircraft, one which has subsequently been retrofitted with winglets but did not have a pre-modified wing to facilitate these, speed brake travel was reduced significantly after wing reinforcements were installed for winglet installation. This then reduced the effectiveness of the speed brake (in an emergency descent). Combined with a lower weight it could then be impossible to reach 10,000' in the specified certification time to reach it.
Thus, a BBJ-1 flown years ago had it IMPOSED that at the onset of the emergency descent the gear MUST be selected down as one of the first memory items (as soon as extension was within limits prior to initiating descent). A simulator exercise enforced this policy for the operator's crews.
It may have been invariably required for similar aircraft (-600/-700, with an older unmodified wing, thus requiring wing reinforcements, restricted speed brake travel as a result and retrofitted winglets) when operating at low weights.
If you have for instance an "older" 737 NG (-600/-700) wing aircraft, one which has subsequently been retrofitted with winglets but did not have a pre-modified wing to facilitate these, speed brake travel was reduced significantly after wing reinforcements were installed for winglet installation. This then reduced the effectiveness of the speed brake (in an emergency descent). Combined with a lower weight it could then be impossible to reach 10,000' in the specified certification time to reach it.
Thus, a BBJ-1 flown years ago had it IMPOSED that at the onset of the emergency descent the gear MUST be selected down as one of the first memory items (as soon as extension was within limits prior to initiating descent). A simulator exercise enforced this policy for the operator's crews.
It may have been invariably required for similar aircraft (-600/-700, with an older unmodified wing, thus requiring wing reinforcements, restricted speed brake travel as a result and retrofitted winglets) when operating at low weights.
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IMHO there ain't no rush in modern a/c (jets). There is enough onboard O2 for pax and crew to complete a rapid (emergency descent) into oxygen rich air just by using speed and speed brake to descend. Using gear, which you will need later in full working order, should not be necessary.
There was a debate on here a couple of years ago, about emergency descents; perhaps more a crew/ATC coordination ICAO procedure discussion. After having read some reports following emergency descents due to total loss of pressurisation, and also having had a pax on a biz jet with ear problems, I caution against the standard SOP of very high ROD below FL 150-180. There is plenty of O2 outside for people to survive and below FL150 no problem. I've been skiing at FL130, as have many. The problem with high ROD below FL150 is clearing your ears, even the healthy. Severe ear problem, burst drums etc., is an incapacitation, and not just for a few days. In one case >20 pax were effected. What if it were crew members? I still reckon at FL180 2000fpm is enough & FL130 1000fpm is enough. There is enough O2.
So the idea that this is a panic meteorite re-entry manoeuvre IMHO needs to be rethought. I wait to be shot down, but note I comment only about the ROD when in an sufficient O2 environment. Remember, in B's QRH it suggests maintaining crz speed in descent if structural damage is in doubt. If it's OK for the people then it's OK all the time. Thus ROD will be less than max even at high levels.
There was a debate on here a couple of years ago, about emergency descents; perhaps more a crew/ATC coordination ICAO procedure discussion. After having read some reports following emergency descents due to total loss of pressurisation, and also having had a pax on a biz jet with ear problems, I caution against the standard SOP of very high ROD below FL 150-180. There is plenty of O2 outside for people to survive and below FL150 no problem. I've been skiing at FL130, as have many. The problem with high ROD below FL150 is clearing your ears, even the healthy. Severe ear problem, burst drums etc., is an incapacitation, and not just for a few days. In one case >20 pax were effected. What if it were crew members? I still reckon at FL180 2000fpm is enough & FL130 1000fpm is enough. There is enough O2.
So the idea that this is a panic meteorite re-entry manoeuvre IMHO needs to be rethought. I wait to be shot down, but note I comment only about the ROD when in an sufficient O2 environment. Remember, in B's QRH it suggests maintaining crz speed in descent if structural damage is in doubt. If it's OK for the people then it's OK all the time. Thus ROD will be less than max even at high levels.
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We were taught it as an option in the 744. Tradeoff is that you have to decelerate to 270/.82 if at high altitude cruise, where you can start down immediately without gear down. Also, descending at limit speed with speedbrakes extended will get you down just about as fast.
I've tried it both ways in the sim, and it's easier to leave the gear up. I think the only reason to bring the gear down is for a "land ASAP" emergency with excess fuel on board.
I've tried it both ways in the sim, and it's easier to leave the gear up. I think the only reason to bring the gear down is for a "land ASAP" emergency with excess fuel on board.
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The text in the 777/787 FCTM, mentioned by sleeve wizard:
is identical in the B756 and B737 Flight Crew Training Manuals.
The rapid descent is normally made with the landing gear up. However, when structural integrity is in doubt and airspeed must be limited, extension of the landing gear may provide a more satisfactory rate of descent.
If the landing gear is to be used during the descent, comply with the landing gear placard speeds.
If the landing gear is to be used during the descent, comply with the landing gear placard speeds.
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Originally Posted by RAT 5
IMHO there ain't no rush in modern a/c (jets). There is enough onboard O2 for pax and crew to complete a rapid (emergency descent) into oxygen rich air just by using speed and speed brake to descend. Using gear, which you will need later in full working order, should not be necessary.
As said by others, rate of descent in a modern jet with speedbrakes at Mmo/Vmo is more than sufficient to reach FL100 in couple of minutes. Some operators are now teaching even to initially maintan the current speed during emergency descent, perform a quick damage assessment (vibration, system parameters, etc.) and only then go for Vmo/Mmo if no damage and higher rate of descent is required.
Lowering the landing gear for emergency descent in a modern jet is only asking for trouble, especially if you can't get it up after finish with the manuever. Imagine crusing at FL100 after depressurization with gear down in ETOPS segment...