Is there a particular altitude for airliners to extend the landing gear?
The important point is that lowering the landing gear doesn’t just provide wheels for the plane to land on. It’s also a major shift in the configuration of the aircraft which has tremendous aerodynamic effects. That’s the reason the landing gear can be retracted and extended. In order to lower the landing gear, the plane has to be at a low enough speed. Attempting to lower the landing gear at full cruise speed will damage the gear on most aircraft. On some, they would literally get ripped off the aircraft. And once the gear is down, the aircraft will have much more drag. In a large plane, lowering the landing gear early may make it easier to maintain an appropriate approach speed. Planes are designed to be aerodynamically efficient, so it’s not so easy to slow them down. Lowering the gear “fixes” that. Lowering the gear early also gives more time to stabilize the approach. You don’t want to make any dramatic changes late in the approach. And, of course, if the landing gear fails to ext
The point at which the gear is lowered depends a great deal on pilot discretion, although the manufacturer, the government, and the operator (in the case of airliners) may impose some restrictions. For example, the manufacturer of the aircraft usually specifies maximum speeds beyond which the gear must not be extended or must be retracted (often the two maximums are different). Airlines may impose procedures on their pilots that require or prohibit extending the gear under certain conditions. Extending the landing gear dramatically increases the drag on the airplane, causing it to slow down significantly. Pilots sometimes extend the gear a bit earlier or a bit later with this fact in mind. On many aircraft, the gear must be extended once full flaps are selected, otherwise a warning is annunciated in the aircraft. Overall, choosing the right moment to extend the gear is largely a function of a pilot’s experience with a given aircraft. The more time he has spent flying it, the better he’
There is actually no rule at all, no altitude or position to extend the landing gear. As every approach is different. If a pilot wants to establish the approach up early, then he will probably tidy the plane’s configuration early as well by extending the landing gear. There are no rules for particular airlines. For example, if a Boeing 747 was coming in too high, then he would extend the flaps earlier then usually. It is the same with the landing gear, you don’t have to have it extended at a certain point or altitude.
I’ve had the thrilling opportunity to ride along on many test flights sitting in the jump seat. From what I’ve seen the pilots like to use the landing gear as speed brakes when slowing for the approach….within their speed limitations. They aren’t shy about throwing that gear handle at all. Speed is a little high?….bam!…down with the gear. This is test pilots however…who may not be under the same procedures as line pilots. I think there might be one official regulation that might indirectly affect when they extend landing gear on revenue flights…and that would be establishing a stabilized approach by a certain point….like the outer marker or something like that. In that case I would think a pilot would want to have the gear out at least by the time they want to descend on the glide-slope. That’s my personal checklist when I’ve had the opportunity to fly the full motion A320 simulator. At glide-slope intercept, I lower the gear. Let speed stabilize…and then final extension
