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Gear up

Old 14th Oct 2009, 20:31
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Gear up

A fellow flight instructor took me aback with a statement that the Cardinal gear should not be retracted during a short field takeoff until well clear of the obstacles because of the drag of the retracting wheels. Even though there are no gear doors, he said the gear legs rotate during retraction and at some point the wheels are at 90 degrees to the airflow, increasing the drag.
I read the POH and it says the gear should be retracted when clear of the obstacles, sure, but the reason given is the possibility that if retracted too soon, the pilot might hit the ground with the retracting wheels since they actually move downward as they start to fold.
Has anyone heard of the theory of the drag increase, and is it true? I always like to get my gear up early, especially on a short field takeoff, and wait only until I am positively clear of the ground and climbing, but rarely look for obstacles as controlling at this point. With the gear up my climb rate is better and the obstacles will be cleared easier.
There might be a case for delaying the retraction in case an immediate landing becomes necessary, but that is another topic.
Pilots are good at talking things to death.
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Old 14th Oct 2009, 21:28
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All the Cessna retractable Cessnas will lose a bit of speed as the wheels turn through the 90 degrees on retraction.

My RG had the gear motor pump give up the ghost on retraction and the performance was interesting, even on a fairly long runway!! Visually the wheels were at the 90 degree point so giving most drag.

Not in the book but it happens. Been there done that etc!!

Not like the female FAA person who criticized a friend for "not" selecting the gear to the "UP" position prior to the roll in a Mooney, while attempting a short field take off!! Yes, there was a witness.

Speedbird 48
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Old 14th Oct 2009, 23:11
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The question is simple. Does the momentary drag rise as the gear translate result in a greater or lesser performance loss over clmbing with the gear out and thus taking the constant drag penalty with the gear down and locked. I have never flown a Cardinal RG but I have lots of time in a late model 210 (no main gear doors). There is virtually no discernable check in the climb as the gear retracts and it definitely climbs better with the gear retracted. I always retracted the gear when clear of the runway with a positive rate of climb and hold Vy untill 500 ft AGL.

Why not try experimenting. Pick a calm day and take a friend to note the time from rotation to 100ft AGL using both methods.
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Old 14th Oct 2009, 23:36
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My point was that although there is only a momentary loss of speed as the gear retracts normally, it is there, but, in the case of a failure the loss of climb performance is significant.

So we can all go to the theory that "it will never break" or be a bit cautious!!

Speedbird 48.
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Old 15th Oct 2009, 01:54
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Speedbird
I guess it boils down to where you asses the risks lie and what priority to assign to sometimes contadictory stategies to minimize them
IMO Having the gear fail to retract should not normally result in an accident. Having the engine fail right after takeoff will always have a higher probability of an accident and can be caused by many possible mechanical failures in ther engine and/or propellor(your scenario requires one specific failure mode of the landing gear system). For that reason I want to get as far away from the ground as fast as possible in any single engine aircraft I am flying in order to have the the widest array of options in the event of an EFATO.
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Old 15th Oct 2009, 07:36
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I've seen this with a Cessna 337, The book figures show about 150fpm less rate of climb with the gear down. In order to retract the gear a few big doors that have the same effect as airbrakes have to open. This will drag you into the trees on one engine!

And yes the path of the u/c during retraction does take it below normal wheel level.
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Old 15th Oct 2009, 15:25
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The 337 is a special case because of the design of the aft fuselage and gear doors, and yes on this airplane there is a significant drag rise when retracting the gear so it is recommended that thegear be left down untill the obstacles are cleared. However in the 337 the retraction drag rise is caused by the gear doors. The original poster on this thread was discussing the Cardinal RG, an airplane which never had main gear doors. Incidentally there is a mod for the 337 which eliminates the main gear doors. A 337 that I used to fly had this mod and in addition to greatly simplifying the retractiion system pretty much eliminated the drop in ROC as the gear retracted.
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