Today's Message Index:
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1. 09:22 AM - Flap Fuse (Ian)
2. 10:55 AM - Re: Flap Fuse (Denis Walsh)
Message 1
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How about disconnecting the pushrods and checking for resistance to
movement by moving each flap manually? Excessive current draw suggests
that the motor is struggling. You could divide the movement in two -
the motor to the push rods and the push rods to the flaps. If you feel
no resistance to movement on the flap side then maybe there's some
interference or tightness on the motor side. Could anything be
misaligned, interfering or overtightened in motor to pushrod chain?
Ian Brown
"I have an RV-7a with 700 hours on her and a month ago the flap fuse
( 7.5amps )
blew on two consecutive landings. The fuse has
never blown before in those 700 hours. I know I was well below the
white arc,
10 to 15 knots below, on both of the landings.
After I changed the fuse on those two, it went almost a month without
ever happening
again, then the fuse below twice more over the
course of a few landings.
It always blows on the downward movement, but the point at which it's
blown varies
anywhere between just barely having moved and
being as much as 20 degrees when it happens."
Message 2
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The flap motor has a clutch and slips when the resistance gets too
high, so it is unlikely that this is the problem, given the
intermediate position of the flap when it occurs.
I would look for an area of high resistance in the circuit. Check the
switch for all connections. Check all crimps, and check the
connections at the fuse. Check the connections at the actuator, and at
the power bus. Lastly don't forget the ground side of the circuit.
If all those check out, I would do a current measurement, and make
sure the fuse is big enough. Remember the fuse is sized according to
the wire size and length.
Good luck and let us know how it comes out.
Denis
On May 16, 2010, at 5:20 , Ian wrote:
> How about disconnecting the pushrods and checking for resistance to
> movement by moving each flap manually? Excessive current draw
> suggests that the motor is struggling. You could divide the
> movement in two - the motor to the push rods and the push rods to
> the flaps. If you feel no resistance to movement on the flap side
> then maybe there's some interference or tightness on the motor
> side. Could anything be misaligned, interfering or overtightened
> in motor to pushrod chain?
> Ian Brown
> "I have an RV-7a with 700 hours on her and a month ago the flap fuse
> ( 7.5amps )
> blew on two consecutive landings. The fuse has
> never blown before in those 700 hours. I know I was well below the
> white arc,
> 10 to 15 knots below, on both of the landings.
>
> After I changed the fuse on those two, it went almost a month
> without ever happening
> again, then the fuse below twice more over the
> course of a few landings.
>
> It always blows on the downward movement, but the point at which
> it's blown varies
> anywhere between just barely having moved and
> being as much as 20 degrees when it happens."
>
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