Landing gear on aircraft....?

Question

Why and what is the cause of landing gears failing to retract on some planes when it appraoches a runway for landing?

Thanks guys for the correction. Was a slip of mind.

Answer 1

it has to do with electrical switches. there are six switches that all have to be in the proper position to put the landing gear handle in the up position. when the handle is in the up position it is then up to hydraulics to lift the landing gear up. to put the landing gear handle down you also need different switches to lower the landing gear handle to the down position just like before it is then up to the hydraulics to lower the landing gear. these switches are actually safety devises to make sure that the landing gear doesn't go up or down in the case that either the doors are not open or the gear isn't in the right position causing damage to the aircraft. of coarse there is always the chance that the did lose hydraulic pressure but that is very slim it is always more likely that you would have a mechanical switch that just messed up. i hope this answered you question because i have to work on this system every single day.

Answer 2

There could be many reasons. Usually it is just a part of the hydraulic system of the gear or a sensor that is failing. Any aircraft with retractable gear requires a system other than the primary to lower the gear if the primary fails. Generally it is a system of cables and pulleys or other mechanical means that runs to all the gear and attaches to the "uplocks". The uplocks hold the gear up when it is retracted. By the pilot pulling the handle in the cockpit the weight of the gear/ force of wind, will lower the gear. Take a CRJ for example. The gear is all hydraulic, and if something is not right in the system as monitored by the computer the crew gets a "gear disagree" message on the display. It could be a sensor that is out of adjustment or sometimes even the hydraulic valves that control the gear. Either way, when it comes to the hangar, we troubleshoot it using system schematics and logic diagrams to help find the cause. Then it is put on jacks and the gear is swung several times to make sure it works. At any rate, there is a backup system.

Answer 3

Aircraft landing gears are very complex mechanisms. They have a complicated geometry of parts to ensure the gear stays where it is put. Most landing gear is retracted of extended by a hydraulic system that has to do a lot of things in the proper order for that to happen. For example when the gear goes up, the geometric lock has to be broken by hydraulic pressure through a series of linkages. The gear then starts to move, but before it gets too far, the gear doors have to open to allow it to be retracted into the airframe. Once the gear is retracted, then the doors have to close in the right sequential order so they will all fit together. As you can see, this is an extremely complicated system, failure of any one of the many linkages or hydraulic valves would cause a landing gear malfunction. the most obvious suspect cause of this problem though is lack of hydraulic pressure because of a loss of hydraulic fluid. There is amost always a back up emergenct system to get the gear down and locked so a safe landing can be made. Hope this helps

Answer 4

You've had some decent answers here, so I'll just add this: Even when the normal gear extension system fails, we have back-up systems for extending it. Some use a back-up hydraulic system, some simply free fall, some use compressed nitrogen to "blow" the gear down, and some have cranks that connect to gears and cables that extend the gear. My 421 gear is electric, and if it fails, there is a little crank under the right side of the command pilot's seat. Unfold it and turn it about 40 turns and the gear lights go green (usually). This is tested during annual inspection, assuming there is no reason to test it sooner.

Answer 5

Usually poor maintenance. The gears work by hydraulics and sometimes a line will just break, and then no one's fault really. But then sometimes the airplane owners do not get the inspections they need. Just like car owners, sometimes too lazy or indifferent to inspections or do not want to pay. Why do people delay oil changes. Too cheap to pay. Same reason, that things fail in a small airplane. Now the larger planes, gears that fail are usually mechanical defects that just happen. But this does not happen that often as leaks and cracks in lines are usually caught early.

Answer 6

landing gear retracts on take off

and is put down for landing

it's a mechanical-hydrauilic part of the airplane, which like brakes, can fail - that is why planes go through an inspection
every so often to look over thousands of points of interest

Answer 7

Not sure of the question. You dont really want the gear to retract when your landing.

Answer 8

This phenomenon on the airplane I fly is caused by the fact the gear is down and welded and does not retract at any time.

Answer 9

Landing gear are mechanical, and sometimes mechanical things break. Fortunately, it doesn't happen often because of the regulations in place requiring frequent inspections, and retirement of parts well in advance of their expected life-limits.