320tech From Turks and Caicos Islands, joined May 2004, 489 posts, RR: 5 Reply 3, posted (8 years 4 months 13 hours ago) and read 3920 times:
Remember too, that an airliner has more than one way to get the gear down. If the regular way doesn't work, the pilots can use the alternate extension. Typically, it's a cable operated system that first opens the gear doors, then drops the gear. There may be a separate hydraulics system to lock down the gear.
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 69 Reply 4, posted (8 years 3 months 4 weeks 1 day 21 hours ago) and read 3772 times:
The last time I remember an airliner having a gear not extend it was because a large, hard rubber chock was left in the wheel well and the gear jammed against it on retraction. They knocked the gear down by bouncing the plane on the other main and the nosewheel a couple of times. Boeing then advised them that, even though the outcome was successful, the nosegear was probably not strong enough for such use and that they might have been safer landing will all retracted.
That is one prevalent school of thought; that all UP is better than any combination of UP and DOWN. Most landing gear problems are just indication failures. The gear is DOWN but the bulb is burned out or something like that.
It does take some extraordinary event to cause a gear not to extend on a modern airliner.
In my career I've had to go back and peek through the periscope at the maingear twice, and send a jumpseater back once. In all three cases we were fine and landed without incident.
Slam - now where is that periscope
[Edited 2005-08-14 17:30:54]
Happiness is not seeing another trite Ste. Maarten photo all week long.
HAWK21M From India, joined Jan 2001, 31457 posts, RR: 57 Reply 5, posted (8 years 3 months 4 weeks 1 day 20 hours ago) and read 3720 times:
All Airliners have a secondary means to extend the Gear either Manually or Hydraulically.
In case that does not function then jerking the Aircraft is an option & flying over tower to confirm Gear down is an option.
Finally its a belly landing.
Quoting SlamClick (Reply 4): The last time I remember an airliner having a gear not extend it was because a large, hard rubber chock was left in the wheel well and the gear jammed against it on retraction. They knocked the gear down by bouncing the plane on the other main and the nosewheel a couple of times.
Remember that Incident too.
Quoting SlamClick (Reply 4): The gear is DOWN but the bulb is burned out or something like that.
Red light out,No green = doubt.
Quoting SlamClick (Reply 4): In my career I've had to go back and peek through the periscope at the maingear twice, and send a jumpseater back once. In all three cases we were fine and landed without incident.
In Cargo since its not possible to access the Main deck in flt,a secondary L/G Indication is installed.
Fergulmcc From Ireland, joined Oct 2004, 1916 posts, RR: 54 Reply 12, posted (8 years 3 months 4 weeks 1 day 2 hours ago) and read 3540 times:
Quoting Air2gxs (Reply 2): A B747 can land with the wing and nose gear extended, it may be able to do it with the body and nose, but I suspect balance is an issue. With the wing gear cg is the issue.
True, Take the body gear out on a 747 and it will fall back. I even remember having to put a good bit of weight in the front cargo hold after a maintenance check as the fuel tanks would be empty, so that it can be pushed out of the hanger to be fueled up outside.
Mrocktor From United States of America, joined Jan 2005, 1661 posts, RR: 50 Reply 13, posted (8 years 3 months 3 weeks 6 days 20 hours ago) and read 3378 times:
Gear up landing is really no big deal. The aircraft is designed for this condition from a structural and systems standpoint. The main concerns are structural integrity and fire protection.
An excerpt from AC 25.994-1:
5 ACCEPTABLE MEANS OF COMPLIANCE.
a. The airplane fuel system should be designed to minimize the spilling or
leaking of fuel from damaged components during and following a wheels-up landing.
The unpreventable release of fuel, such as from severed or punctured fuel lines
downstream from shutoff valves, should be diverted or excluded to the maximum
extent practicable from spreading to likely ignition sources.
b. Fuel lines and fuel system components should be located and routed as
far as practicable from likely impact areas and from areas where structural
deformation may cause crushing, severing, punctures or high tensile loads in the
C. Fuel lines should be constructed to protect their integrity during and
after a wheels-up landing. Flexible and stretchable hoses should be used or the
fuel line should be designed to allow stretching or movement with the deformed
structure up to an amount likely to be required to prevent failure under high
tensile or shear loading. Flexible hoses should also be designed and qualified
to absorb the energy that would likely be imparted to the component or fuel line
from direct impact resulting from structural failure.
d. Fuel lines and fuel system components within the engine nacelle should
be arranged and protected to the maximum extent possible so that spilled fuel
caused by damage to lines or components from a wheels-up landing is not likely
to contact hot engine surfaces (over 400° F.). Fuel lines and components should
be shrouded and drained to accomplish this protection.
e. In areas of the engine nacelles, pylons, and airplane fuselage that are
susceptible to being damaged by a wheels-up landing, fuel lines and electrical
wiring should be isolated, separated and routed to the maximum extent
practicable, to minimize the hazards of spilled fuel flowing into an area
containing a potential ignition source. In addition, electrical components
should be acceptable for operation in flammable leakage zones identified in
accordance with 9 25.863.
f. Shielding and drainage may be used wherever it is considered appropriate
to prevent spilled fuel from spreading to potential ignition sources or
occupied areas. Drip fences and drainage troughs can be used to divert flow of
spilled fuel from potential ignition sources such as hot engine cases,
electrical accessories, and component compartments. Nonconductive material
should be used to shroud electrical wiring that might be damaged by deforming
g. Fuel shutoff valves should not be located within the engine nacelles,
pylon areas or adjacent to engine air intakes and exhausts where they may be
subjected to damage from impact and scraping action during a wheels-up landing.
Fuel shutoff valve mountings should, as a minimum, be designed for the inertial
loads listed in 8 25.561 unless the location and estimated loads in the area
impose a greater strength requirement to maintain the shutoff valve mounting
h. Installation of auxiliary fuel tanks and systems in the fuselage should
be based on the guidance and information in AC 25-8, Auxiliary Fuel System
KhenleyDIA From Sweden, joined Feb 2005, 425 posts, RR: 0 Reply 14, posted (8 years 3 months 3 weeks 6 days 18 hours ago) and read 3335 times:
Quoting Klaus (Reply 10): Weird indeed. By now LEDs should be bright enough to replace any light bulb even under full daylight. That would have been the only possible reason against the change I could think of...
Here is another option. I know that in an accident investigation, don't they check the bulbs to see if they were on during the crash by looking at the filament?? Can they do the same thing with LEDs? Not sure if that would even be reason enough, but just figured that I would mention that option.
Why sit at home and do nothing when you can travel the world.
Air2gxs From , joined Dec 1969, posts, RR: Reply 17, posted (8 years 3 months 3 weeks 6 days 14 hours ago) and read 3288 times:
Quoting Kaddyuk (Reply 15): guess that a blown light doesnt apply to those aircraft with EICAS or ECAM systems as it will just appear on the GEAR status page?
All the aircraft I'm aware of with EICAS and ECAM use the lights as primary indication. The computers let you know only if there is a problem via a gear config message or a gear not down message (both of those are EICAS, don't recall the ECAM message).
OPNLguy From , joined Dec 1969, posts, RR: Reply 18, posted (8 years 3 months 3 weeks 6 days 12 hours ago) and read 3261 times:
Quoting EMBQA (Reply 9): Wasn't that the famous USAir 737-300 in CLT in the late '80's..? They never did get the right leg down and ended up dragging the wing in.
That was the one, and video of the bounce attempt, and second approach to a landing is on the net somewhere.
Southwest landed with the same configuration at ONT in 1996, but the cause was different. No gear bounce on that one... Our QRH specifically prohibits gears bounces and high-G manuevers to get the gear down.
BTW, the 737NG variants don't have the viewer in the cabin floor for the main gear. two seperate sensors now....
Klaus From Germany, joined Jul 2001, 21346 posts, RR: 54 Reply 20, posted (8 years 3 months 3 weeks 4 days ago) and read 2989 times:
Quoting KhenleyDIA (Reply 14): Here is another option. I know that in an accident investigation, don't they check the bulbs to see if they were on during the crash by looking at the filament?? Can they do the same thing with LEDs?
You´re right, I forgot about that. No, you would not be able to find such a difference with LEDs.
But as long as there´s "backup information" available through the information screens it´s probably not a serious problem.
Abbs380 From United States of America, joined Mar 2005, 120 posts, RR: 0 Reply 21, posted (8 years 3 months 2 weeks 6 days 4 hours ago) and read 2854 times:
Many years ago, a relatively new TWA B767 was flown from (I think, SFO) where it had just had a brake change, to STL. When the gear was selected down on approach, the rh. mlg would not extend. The crew tried everything to get the gear down but could not get it to go, so they diverted to Scott AFB in Ill. and landed with the right gear up. Long story- short version- When the mechs. replaced the brake, they reinstalled the torque arm bolt and nut, but forgot to put a cotter pin in the nut, so, in flight the nut backed off and the bolt dropped out. At some point the torque arm rotated out of position so that when the gear tried to extend, the torque arm hung up on structure and the gear could not go down. Only the few minor injuries to crew/pax but lots of damage to the a/c.
Abbs380 From United States of America, joined Mar 2005, 120 posts, RR: 0 Reply 24, posted (8 years 3 months 2 weeks 5 days 6 hours ago) and read 2716 times:
Mel, I think this happened about 1987 so it was a while ago, here is how I remember it. A mechanic I knew said he watched the landing, he said it was very smothe on the left main then the nose. Because the 767 engines hang down so far there was little damage to the sheet metal, and the wing structure was strong enough to support the load. IIRC they jacked the wing up and got the gear under it then changed the engine, removed the rh mlg door (which obviously was very damaged) and flew it about 300 mi. to TWA/s main mx base in Kansas City where it was repaired. It was not a W/O.
25 HAWK21M: Must have been great for Mx to see it fly again.Any Aircraft ID. regds MEL
26 Abbs380: Mel, cant remember, but did find a link. http://ils.unc.edu/~viles/172i/users/big/docs/AP881103-0166
27 Abbs380: Holy cow, I was just rereading this thread. The TWA thing happened in AUG.87. Im not superstitious.
28 Ballpeeen: The CRJ series of aircraft have no separate indication lights. Gear indication is solely on EICAS, and consisits of three boxes that are green when d
29 HAWK21M: Nice link.Was a Retraction test carried out.I presume so & did the post retraction test Inspection show any abnormality. regds MEL