I have been watching a few aircraft landing videos in crosswind situations and I noticed that if the airliner missed the runway the landing gear would go back into the aircraft. So I'm wondering if this system is automatic after a takeoff or if it's controlled by the pilot manually?
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$\begingroup$ @mins When would the landing gear go up automatically? $\endgroup$– EthanCommented Apr 6, 2016 at 19:01
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5 Answers
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The landing gear system is operated by the pilots. The extension and retraction, depend on the action from the pilot monitoring, on 2 pilots operation. The pilot has a lever on their panel, on which they select the extension (down) and/or retraction (up). Some aircraft has a system to avoid extending them on high speed, to avoid some damage, and on the ground, avoiding retracting, for obvious reasons. There are lights, green and red, indicating their position.
answered Apr 6, 2016 at 12:28
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2$\begingroup$ To make this really good, you might want to edit in the need for positive rate of climb and link this to the flap retraction schedule. $\endgroup$– SimonCommented Apr 6, 2016 at 16:22
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3$\begingroup$ Fun safety design fact: notice how in this diagram the end of the lever for the flaps looks and feels like a little wheel, reminding the pilot that they are manipulating the landing gear and not some other control. $\endgroup$ Commented Apr 6, 2016 at 18:32
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$\begingroup$ @EricLippert
the end of the lever for the flapseuhm, did you meanthe end of the lever for the gear? $\endgroup$– FedericoCommented Apr 7, 2016 at 7:29 -
$\begingroup$ @EricLippert True! And that's why (in a Cessna at least) the lever for the flaps looks like a flap. $\endgroup$– janCommented Apr 7, 2016 at 13:41
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2$\begingroup$ Hah I totally misedited that to say the opposite of what I intended. Brains are weird. $\endgroup$ Commented Apr 7, 2016 at 13:46
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It's manual. Once there is positive climb the pilot will retract the gear and flaps to minimize drag.
answered Apr 6, 2016 at 12:49
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All landing gear that I know of are all controlled by the pilots. I have never heard of an "automatic landing gear" as you describe it.
As some comments below say, there is one airplane that has/had an automatic gear (Piper Arrow) but it was not really the brightest idea because it could cause in-flight problems if not handled properly.
answered Apr 6, 2016 at 12:25
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4$\begingroup$ Early Piper Arrows (and a few other models) had an automatic gear extension feature. It turned out to be more trouble than it was worth and has been disabled on most aircraft. I haven't found an authorative link describing it, but google 'piper automatic gear extension' and you'll see what I mean $\endgroup$ Commented Apr 6, 2016 at 13:04
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$\begingroup$ @DanPichelman Never knew that, another thing to add to my aerospace knowledge! $\endgroup$ Commented Apr 6, 2016 at 13:05
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2$\begingroup$ @Adam that sounds dangerous in an unintentional stall - extra drag right when you really want some airspeed! Although I suppose it could help with the pitch down angle $\endgroup$ Commented Apr 6, 2016 at 14:46
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1$\begingroup$ @Adam You also had to engage the override as part of the engine failure checklist. Otherwise, the auto gear extension could ruin a perfectly good dead stick landing. $\endgroup$ Commented Apr 6, 2016 at 15:04
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1$\begingroup$ You also had to be aware of it for a short field takeoff over an obstacle. The gear could not be raised until you had enough airspeed unless you override the auto-gear. $\endgroup$– AdamCommented Apr 6, 2016 at 20:41
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As the other answers point out, it generally is operated by the pilots.
In the last project I have participated in, though, flap and gear control was performed by an automated system (see slide 17). The control system was automatically deploying the flaps and gear at a specified location during the final approach, without any pilot intervention.
In the future there might be more aircraft that will use such automation, but not before the appropriate amendments will be done to the regulations and not before one such system will be succesfully certified.
answered Apr 6, 2016 at 12:45
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As soon as there is a positive rate of climb, the gear is retracted because it is a large contributor to drag on the aircraft, effectively reducing its climb performance.
As a passenger you can feel this on some aircraft when the gear is deployed as you can feel the drag on the aircraft (and depending on where you are sitting, you may be able to hear the gear deploying).
Due to its large effect on the performance of the aircraft, in some aircraft the gear is also used as an impromptu air brake to reduce the speed of the aircraft - although in most modern aircraft, this function is taken care of by the air brake/spoilers.
Gear is retracted manually, usually by the pilot observing, and not by the pilot flying (PF). Usually the pilot observing will say "positive rate, gear up" and then move the lever to retract the gear - this is what you are observing in those videos.
answered Apr 7, 2016 at 8:38
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3$\begingroup$ "As soon as there is a positive rate of climb, the gear is retracted " Not always the case, some pilots leave the gear down until there is no more runway left. $\endgroup$ Commented Apr 7, 2016 at 13:44