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Landing Gear Backup?
The Lot Event yesterday got me thinking...
- How often to Landing Gears fail (very rarely apparently) - Are there any Planes with Backup Devices? I always considered a failing Landing Gear a major Risk, particularly on the big Boeings (like above) that have the engines considerably lower than the rest of the frame (considering they could break and subsequently turn the aircraft). Then, in my mind - it was all rather simple. Never looking for proof, I assumed they would have some kind of crank lever they could use in order to manually wind down and lock the landing gear (even if it would probably take half an hour or an hour of cranking) in case of a hydraulic / landing gear failure. Apparently this is not the case on a 767... Are there other aircraft that have this (or another) backup, or are pilots just meant to be able to land aircraft w/o landing gear? Is such a failure even considered in an aircraft's design phase (to make sure the engines and wings are stable enough), or is that a "unforeseen - well good luck!" moment? |
Planes undergo extensive testing, including putting the landing gears under all kinds of stress. In some planes, if the gear can't be lowered in the normal fashion, pilots can try a gravity drop where the doors are open and the gear drops into place via gravity.
Pilots are trained to handle emergencies such as a gear failure. The exact procedures vary by airline and plane type. They can include doing fly bys so crews on the ground can assess the problem; lowering the gear by other means; burning off/dumping fuel to minimize the fire hazard; have emergency equipment on standby; and landing in such a way as to stay off the broken gear as long as possible. A plane with broken landing gear is obviously an emergency, but the recent incidents that I can recall were all non-fatal. The good thing is that pilots and ATC usually have time to examine the situation and do everything possible to minimize damage before the landing is attempted. |
I'm no airplane expert, but it looked like none of the landing gear came out. If only one of the three trucks failed to deploy I would suspect a mechanical problem; but all three I would think would have to be a computer or electrical issue. Perhaps part of the training is if one truck fails to deploy they retract all and land like that? It will be interesting to see what the final determination is.
We have to give credit to the pilot. That was a beautifully executed emergency landing! |
They should have gotten some pickup trucks underneath the plane as it was landing, like in the TV commercial for, I think, Dodge Ram trucks.
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Originally Posted by rubesl
(Post 17376969)
They should have gotten some pickup trucks underneath the plane as it was landing, like in the TV commercial for, I think, Dodge Ram trucks.
As to the hows and why's, there are lots of people guessing, but it will probably be months before an answer comes out, if ever. Patrick Smith, an airline pilot who writes for Salon.com gives his assessment of what might have happened and why the accident points to a potentially troubling scenario. The million-dollar question, obviously, is how in the world did all three landing gear units of a modern commercial airliner fail to come down? I wish I could tell you. I fly 767s for a living and I’m as mystified as anybody else. The plane has both a normal and alternate gear extension system. The normal system uses hydraulics, the alternate relies mostly on gravity, allowing the huge assemblies to more or less free-fall into place if need be. Neither of these, for reasons we’ll learn soon enough, did the trick. Whatever the problem was, it seems to have been something pretty far up the chain of the systems’ architecture, such that neither of two independent systems was sufficient. The 767 has been in service for nearly 30 years, together with its little brother, the 757. The 767 is the much larger of the two, but otherwise these aircraft are extremely similar, sharing a so-called common type certification that allows pilots like me to be simultaneously qualified on both. In all the millions of landings these planes have made over the past three decades, nothing like this has happened before. LOT, for its part, is a small but well-respected carrier with an excellent safety record. A freak malfunction? A maintenance mistake of some kind? We’ll find out eventually. |
Originally Posted by raph
(Post 17376451)
- Are there any Planes with Backup Devices?
Originally Posted by Pete838
(Post 17376949)
I'm no airplane expert, but it looked like none of the landing gear came out. If only one of the three trucks failed to deploy I would suspect a mechanical problem
The biggest risk to the passengers in a situation like this is being injured on the escape slides. The chance of injury from the landing itself is very low. |
As noted by the 767 driver posting above, the normal hydraulic gear extension system has a backup, "gravity", which occasionally experienced pilots may attempt to assist with maneuvers increasing "G" forces 9especially in smaller, lighter birds used in General Aviation, shaking the gear out of the wells, as it were...
The interesting (and little noted) dramatic visual graphic of the videos is that the a/c essentially "landed' on its engines and pylons with little contact between the fuselage and the runway, demonstrating both purposeful design and extremely strong structural components. To those of us around/in a/c for many decades, the entire incident demonstrates the technical "know how" of the folks who designed and built the a/c, and the steady hand and skills of the guy (or maybe woman) in the left seat, which "says a lot for LOT". There was a time when pilots were quick to say that any landing after which all the SOBs ("Souls on Board") could walk away was a good one. |
On some aircraft the issue with manual gear extension is that you have only one shot to do it. If you deploy the alternate system with the gear up, it will not go down. This can make a situation go from requiring a simple fix of the landing gear system to a very expensive gear-up landing.
Originally Posted by TMOliver
(Post 17377624)
There was a time when pilots were quick to say that any landing after which all the SOBs ("Souls on Board") could walk away was a good one.
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Originally Posted by LarryJ
(Post 17377480)
Every airplane with retractable landing gear has an alternate method of extension.
It was likely only one of the three that failed to extend--most likely one of the main gear. The Captain choose to land with them all up instead of the unstable situation of having only one main gear. The biggest risk to the passengers in a situation like this is being injured on the escape slides. The chance of injury from the landing itself is very low. |
Originally Posted by emma69
(Post 17377763)
With the landing gear on those aircraft, it is housed inside with a 'door' (for want of a better term). Could it be that the doors didn't open rather than the gear not extending down?
The manual extension should release the door and let the gear "fall down". Some aircraft do not have gear doors at all. In the 767's case, if there was some sort of electrical issues it is definitely possible the door didn't open. |
there are airplanes w/parachutes.....cirrus is one iirc....recent news story about it not working iirc.....
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It seems like when I was a kid I remember hearing people talk about airports spreading "foam" all over the runway when a plane had landing gear problems. Am I imagining this, or is this rooted in reality? I didn't see any mention of "foam" on the runway in the LOT incident. (Presumably the foam worked as a fire suppressant, not as a cushion)
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Originally Posted by rubesl
(Post 17376969)
They should have gotten some pickup trucks underneath the plane as it was landing, like in the TV commercial for, I think, Dodge Ram trucks.
Anyone who knows the landing speed of most larger jets would call mythbuster knowing that there is a big gap between the landing/wheels down speed and the maximum spped of many pickup trucks. |
Originally Posted by Santander
(Post 17377970)
The actual term is gear door, so you're correct. :p
The manual extension should release the door and let the gear "fall down". Some aircraft do not have gear doors at all. In the 767's case, if there was some sort of electrical issues it is definitely possible the door didn't open. |
Originally Posted by rubesl
(Post 17376969)
They should have gotten some pickup trucks underneath the plane as it was landing
http://www.youtube.com/watch?v=2961-Ck0EIk#t=6m "Roger control, starting approach now... and however it turns out... thanks." |
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