minds_warped
New Member
Can someone explain why there is a minimum gear retraction speed, such as gear must be retracted below 105 knots? For cryin out loud I cannot find this anywhere! Thanks for the input.
Min Gear retract speed ?
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USMCmech
Well-Known Member
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Can someone explain why there is a minimum gear retraction speed, such as gear must be retracted below 105 knots?
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Are you sure that isn't suposed to be maximum gear retraction?
Most light twins have nose gear that folds back into the nose. If the airspeed is too high the gear will slam back into the wheel well. This is useually called Vlo.
I can't think of any reason there would be a minimum airspeed.
The hydraulic system dosen't require any help for retraction.
Can someone explain why there is a minimum gear retraction speed, such as gear must be retracted below 105 knots?
[/ QUOTE ]
Are you sure that isn't suposed to be maximum gear retraction?
Most light twins have nose gear that folds back into the nose. If the airspeed is too high the gear will slam back into the wheel well. This is useually called Vlo.
I can't think of any reason there would be a minimum airspeed.
The hydraulic system dosen't require any help for retraction.
USMCmech
Well-Known Member
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I'm pretty sure that "Vle" is the maximum speed at which the gear can remain extended without damage to gear doors. I also think It has a lot to do with aircrafts stability and controllability.
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The main limiting factor for Vle is the landing gear doors and hardware. They are a bunch of small bolts holding a big door out into Cat 5 hurricane force winds.
I'm pretty sure that "Vle" is the maximum speed at which the gear can remain extended without damage to gear doors. I also think It has a lot to do with aircrafts stability and controllability.
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The main limiting factor for Vle is the landing gear doors and hardware. They are a bunch of small bolts holding a big door out into Cat 5 hurricane force winds.
C650CPT
Well-Known Member
I believe a big reason for having speeds is to limit the size of the hydraulic pump. For example on the BE-200 Max Gear Retract Speed is 163, Max Gear Extend Speed is 181 Which is also the Max Speed for Operating with the Gear Extended. The difference in Retract and Extend speeds is the loads put on the Hydraulic pump NOT the Gear Doors. I would venture to guess the same holds true for lighter airplanes with electric gear motors.
Jim
Jim
kellwolf
Piece of Trash
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Most light twins have nose gear that folds back into the nose. If the airspeed is too high the gear will slam back into the wheel well.
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Seneca's nose gear goes forward (against the wind) on retract. I always assumed you had to be below a certain AS so the hydraulics would still be able to retract the gear.
Most light twins have nose gear that folds back into the nose. If the airspeed is too high the gear will slam back into the wheel well.
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Seneca's nose gear goes forward (against the wind) on retract. I always assumed you had to be below a certain AS so the hydraulics would still be able to retract the gear.
JDE
Well-Known Member
I'm glad I'm not the only one having trouble with this concept completely. I've always understood that Vlo was gear operating speed...the speed at which you needed to bring the gear up (or the speed you were 'operating' the gear). And Vle was gear extend speed...the speed at which you could bring the gear down (or the speed you were 'extending' the gear). If you look in the manual for a Piper Arrow it says,"...bring the gear up before 125 mph, and do not extend the gear above 150 mph." So with that statement, my original thinking would be correct. And for that aircraft it would make sense. If you get above a certain airspeed (125 mph in this case) the system has a hard time retracting the gear because of the airloads placed on the gear doors. But, if you're extending the gear, the higher airspeed would actually help bring the gear down and lock it in place.
Now, get into a Beechcraft Bonanza or Baron. Vlo & Vle are the same. You can't retract, extend, or operate above the same speed, so who really cares.
Next step, a Falcon 10. Vlo 190, Vle 220. Our instructor said, "...don't move the handle above 190, don't fly with the gear down above 220."
Here's my question...what would be the point of being able to fly 220 kts with the gear down if you are not able to 'move the handle' above 190 kts? Would there ever be a situation where you would need to slow to 190, extend the gear and then speed back up to 220? (Note: the Falcon 10 does not have inside gear doors. It's similar to the Piper Arrow...so to speak).
Now with all that being said, I looked in the Dictionary of Aeronautical Terms and I found this:
Vle - landing gear extended speed - "The maximum speed at which an aircraft can be safely flown with the landing gear extended."
Vlo - landing gear operating speed - "The maximum speed at which the landing gear can be safely extended or retracted."
So, it sounds like to me the best thing to do would be to look in the aircraft manual and do as it describes.
One more thing. I was speaking with a seasoned airline pilot (23,000 hours) and he said the difference in speeds was (depending on the aircraft) because of the gear doors...or at least that was the reasoning on the planes he had flown.
Maybe some of this will shed some light on the subject.
Now, get into a Beechcraft Bonanza or Baron. Vlo & Vle are the same. You can't retract, extend, or operate above the same speed, so who really cares.
Next step, a Falcon 10. Vlo 190, Vle 220. Our instructor said, "...don't move the handle above 190, don't fly with the gear down above 220."
Here's my question...what would be the point of being able to fly 220 kts with the gear down if you are not able to 'move the handle' above 190 kts? Would there ever be a situation where you would need to slow to 190, extend the gear and then speed back up to 220? (Note: the Falcon 10 does not have inside gear doors. It's similar to the Piper Arrow...so to speak).
Now with all that being said, I looked in the Dictionary of Aeronautical Terms and I found this:
Vle - landing gear extended speed - "The maximum speed at which an aircraft can be safely flown with the landing gear extended."
Vlo - landing gear operating speed - "The maximum speed at which the landing gear can be safely extended or retracted."
So, it sounds like to me the best thing to do would be to look in the aircraft manual and do as it describes.
One more thing. I was speaking with a seasoned airline pilot (23,000 hours) and he said the difference in speeds was (depending on the aircraft) because of the gear doors...or at least that was the reasoning on the planes he had flown.
Maybe some of this will shed some light on the subject.
seagull
Well-Known Member
Vle is the max for flying with it already extended.
You can have two different Vlo's.
Vlo is operating, usually the max speed for extension
Vlo is also used for max gear retract speed, usually due to the nosegear moving forward to retract against the airstream.
We can extend the gear at 260 kts but then can accelerate to 300 kts with it down. Max retraction speed is 230.
You can have two different Vlo's.
Vlo is operating, usually the max speed for extension
Vlo is also used for max gear retract speed, usually due to the nosegear moving forward to retract against the airstream.
We can extend the gear at 260 kts but then can accelerate to 300 kts with it down. Max retraction speed is 230.
USMCmech
Well-Known Member
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One more thing. I was speaking with a seasoned airline pilot (23,000 hours) and he said the difference in speeds was (depending on the aircraft) because of the gear doors...or at least that was the reasoning on the planes he had flown.
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On most fully enclosed gear designs the sequence goes like this. DC-8, DC-9, 707, 747, ect.
Slow to Vlo
wheelwell doors - open
landing gear - extend
wheelwell doors - close
The weelwell doors are huge, and can't handel too much airspeed (that they can survive at all is pretty amazing).
After the doors are closed back up, you can accelerate back up to Vle without hurting anything.
We are always finding fatigue cracks on landing gear doors. They are subjected to huge amounts of vibration and stress durring the short time they are open.
The load on the hydraulic pump is the least of your worries. Most systems run PSIs in the thousands, and usually the pumps can produce much more. The actuator or the hardware it is bolted to will bend or break long before most hydraulic pumps meet their limit.
(light aircraft like pipers may be an exception)
Example a while back a mechanic left a ladder in the way of the gear when it was being retracted. The ladder was crusshed like a paper clip and the gear didn't even pause.
One more thing. I was speaking with a seasoned airline pilot (23,000 hours) and he said the difference in speeds was (depending on the aircraft) because of the gear doors...or at least that was the reasoning on the planes he had flown.
[/ QUOTE ]
On most fully enclosed gear designs the sequence goes like this. DC-8, DC-9, 707, 747, ect.
Slow to Vlo
wheelwell doors - open
landing gear - extend
wheelwell doors - close
The weelwell doors are huge, and can't handel too much airspeed (that they can survive at all is pretty amazing).
After the doors are closed back up, you can accelerate back up to Vle without hurting anything.
We are always finding fatigue cracks on landing gear doors. They are subjected to huge amounts of vibration and stress durring the short time they are open.
The load on the hydraulic pump is the least of your worries. Most systems run PSIs in the thousands, and usually the pumps can produce much more. The actuator or the hardware it is bolted to will bend or break long before most hydraulic pumps meet their limit.
(light aircraft like pipers may be an exception)
Example a while back a mechanic left a ladder in the way of the gear when it was being retracted. The ladder was crusshed like a paper clip and the gear didn't even pause.