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RV-4 flap actuator failure

swjohnsey

Well Known Member
RV-4 that I didn't build, third owner. This is a cool RV-4 built by Keith Livingston, IO-360 CS Hertzell. It is approaching 3,000 hrs. Flaps failed down, flaps wouldn't retract after touchdown. I wasn't at my home field so I decided it would be prudent to take a look on the ground. Check the circuit breaker, it wasn't tripped. Reset it. No luck. Called a friend for advice and to see it there was some hidden trap with flying the 20 miles home with full flaps if I kept it below flap speed. Flew it home and called Van's to order new flap actuator . . . ouch! $600. Sound like it will take a week or 10 days to get here.

Anyway, I'm going to tear into it tomorrow, hopefully to get it working temporarily by beating on it or taking it apart. I read through all the old threads on flap actuators so I have a good idea what it looks like and the problems of the past. I haven't checked the switch or wiring so that is the first order of business. I want to try to get this one working as a backup if I can. Looks like I have to take out the floor to the rear seat for access.

What I noticed in my tinkering around is that I have around 37 degrees of flap travel. I measured several times using a digital device (cube) with the cube zeroed on the upper surface with the flaps retraced and the full flaps. I've put around 300 hrs on it and I haven't noticed a problem.

Advice please!
 
other sources

I have a 7A so not familiar with the 4 but.... Vans isn't the only one that sells these things. Without doing any checking, I still suspect you can save some $$$.
 
There's a common problem where grease migrates in to the motor and fouls the brushes. I know, having had that fail when 1000 miles from home! Disassemble, clean, re-lube (lightly).
 
RV-4 that I didn't build, third owner. This is a cool RV-4 built by Keith Livingston, IO-360 CS Hertzell. It is approaching 3,000 hrs. Flaps failed down, flaps wouldn't retract after touchdown. I wasn't at my home field so I decided it would be prudent to take a look on the ground. Check the circuit breaker, it wasn't tripped. Reset it. No luck. Called a friend for advice and to see it there was some hidden trap with flying the 20 miles home with full flaps if I kept it below flap speed. Flew it home and called Van's to order new flap actuator . . . ouch! $600. Sound like it will take a week or 10 days to get here.

Anyway, I'm going to tear into it tomorrow, hopefully to get it working temporarily by beating on it or taking it apart. I read through all the old threads on flap actuators so I have a good idea what it looks like and the problems of the past. I haven't checked the switch or wiring so that is the first order of business. I want to try to get this one working as a backup if I can. Looks like I have to take out the floor to the rear seat for access.

What I noticed in my tinkering around is that I have around 37 degrees of flap travel. I measured several times using a digital device (cube) with the cube zeroed on the upper surface with the flaps retraced and the full flaps. I've put around 300 hrs on it and I haven't noticed a problem.

Advice please!

If the flap motor is the same as the RV8, then it's just a DC motor. You can replace the motor if you are mechanically inclined. Back in the day, I shop all the robotic stuff from ServoCity. They got linear actuators and all the servo stuff. What surprise me is the replacement part costs as much as the certified stuff.
 
Flap motor

If all you need is the motor, and it's the same as what was in my -9A, you can get just that part from the machine shop that supplies Vans, with the required gizmo already mounted on the drive shaft. I forget the name of the place but I'm sure it's in the archives. There's a very nice woman in the office who handles this small part of their business and will know what you are talking about.
 
After removing about a hundred screws I got access to the flap actuator. Turns out it is out of a Cessna, possibly a 150. I called Van's and they were able to cancel my order. Found a replacement motor off ebay.

Took a couple of whacks at the motor with a ball peen hammer and it started working again!
 
Don't you love the mechanical stuff. You can't do that with the solid state stuff anymore.
 
Turns out the electric flaps on this and a couple of other Rv-4s is a Dave Anders design, very robust. I was able to get a NOS flap motor for $200 off ebay. The old flap motor is working and I have since learned to get access to the flap motor without disassembling half the airplane. I think I will leave it in place 'til it hickups again.
 
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