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Landing Gear Speeds

Old 08-27-2009, 05:25 PM
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Default Landing Gear Speeds

I was wondering why the maximum landing gear extended speed and the retraction speeds would be any different on a single recip. Let's say, for example, a max retraction speed of 107 and a max extension speed of 129 (so an operating range of 107-129) . . . why can't they be the same? Why is retraction lower? Does it have anything to do with the movement of the gear as it relates to the relative wind?

Thanks in advance.
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Old 08-27-2009, 05:34 PM
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Originally Posted by Planespotta View Post
Does it have anything to do with the movement of the gear as it relates to the relative wind?
You are on the right train of thought. Imagine taking any hinged device and moving it in the direction the hinge is intended to be moved, moves freely right? Well now take that same hinge and apply some side force (wind) and notice the increased difficulty in moving that hinged caused by stress of this side force.

In this case the wind applies a force to the main landing gear, increasing stress on the hinge. The faster you go the more this pressure and the more difficult it is for the gear to retract putting strain on the system. Extension tends to be a higher speed because the pumps are limited less as they are assisted by gravity and in some cases springs.
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Old 08-27-2009, 05:34 PM
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Originally Posted by Planespotta View Post
I was wondering why the maximum landing gear extended speed and the retraction speeds would be any different on a single recip. Let's say, for example, a max retraction speed of 107 and a max extension speed of 129 (so an operating range of 107-129) . . . why can't they be the same? Why is retraction lower? Does it have anything to do with the movement of the gear as it relates to the relative wind?

Thanks in advance.

Think doors. and the connecting brackets.
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Old 08-27-2009, 10:41 PM
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Originally Posted by unemployedagain View Post
Think doors. and the connecting brackets.
Pretty sure I have my ideas screwed up, after reading this I think what he is talking about is right for the reasons I gave. Don't know what I was thinking bout with the mains, thats what you get being up 28 hours. Anyone with confirmation? Sorry again, back to bed now.
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Old 08-28-2009, 06:44 AM
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Probably for the same reasons they are different on a Boeing. Gear retraction has the nose gear fighting a head wind. Gear extension has doors moving in the breeze. Once it's extended we just couldn't go any faster.
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Old 08-31-2009, 05:27 AM
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There's multiple reasons. Gear doors tend to be the greatest influence on most speeds. You actually have an area of high pressure inside the cowling(if not, you wouldn't have good cooling), so with nose-gear doors trying to fight that during retraction is another factor.

Plus looking at how the leverage is applied to the gear to raise them, typically it'll be easier to move the gear to the down position, than the up, for many reasons.

Vlo is mainly the speed at which you can hang things out, but you won't damage those items such as gear doors to excessive wind force. They aren't held on by much, and if you have any turbulance or side-slip, you could wreak havoc on them!
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Old 08-31-2009, 06:04 AM
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Many aircraft have seperate gear extension and retraction speeds, for reasons actually known only to the manufacturer and FAA. Some aircraft, especially those with seperately operated gear doors, have a third (higher) speed for gear extended and doors closed. Some also have a fourth gear speed, only published in the MEL/CDL, for intentional gear down flight with one or more gear doors inop in the down position.

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