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Flap motor circuit breaker "pops" intermittently

cleve_thompson

cleve_thompson

Well Known Member
I have a RV9A with approximately 175 hours on the air frame and I have found on a few occasions lately that the 5 amp circuit breaker has opened after the flaps a fully lowered down into full flaps positioned. The flaps will go up when the breaker is reset.
I have a "flap positioning switch" as ordered from Van's. The breaker has never popped when lowering to 10 degrees or 20 degrees nor on raising the flaps up.
The flaps work fine on the ground with the flaps positions being raised or lowered as expected. The clutch also works when the switch is held down. Any ideas?
Cleve
 
7.5 Amps ?

I've read that others have upped the CB/fuse rating to 7.5 Amps. That's what I intend using.

When airborne and dropping the flaps, the motor has to counter the airflow drag on the flaps.
As the flap angle increases the drag increases so the motor has to work increasingly harder, pulling more current. Drag will vary with airspeed so motor workload/current will also vary with airspeed. The higher your airspeed the higher the likelyhood of the 5 Amp CB popping.

When raising the flaps the drag is assisting the motor so less electrical energy needed and thus no CB pop.
 
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Flap motor

I have the same problem with popping fuses, so I started using 7.5 amps. This did help but not enough. Mine seems to pop around 80 kts. Do you think that some motors are jest weaker than others and with the 9 large flaps pushes them over the line?

G.P.
RV-9
 
I don't know about 'weaker' motors. I'm sure the manufacturer's QA process means they're all pretty much the same when new. But flap motor performance will no doubt slowly deteriorate with age, storage environment, use and maintenance/service regime.

Not that familiar with the -9 wing/flaps but if the flap bottom surface area presented to the airflow is bigger than the -6, -7, -8 then, at the same airspeed, air density and flap angle of incidence then the drag will be greater and hence the strain on the flap motor when driving the flaps down will also be greater.
 
Funny but for some reason I used 18 AWG wire and a 10 amp breaker and haven't had a single problem.

In checking the sample in the front of my builder's manual, they used 18 AWG wire and a 10 amp breaker.
 
Our testing shows that on a -7, the flap motor draws just under an amp on the ground, but almost 5 amps in the air when extending under load.

On my first flight, the 5A flap breaker popped but has not done so since (or with the VP system).
 
MCA said:
Our testing shows that on a -7, the flap motor draws just under an amp on the ground, but almost 5 amps in the air when extending under load.

On my first flight, the 5A flap breaker popped but has not done so since (or with the VP system).
Click to expand...
And I suspect that with the longer flaps on the -9, it draws even more power.
 
I control my flaps with a TCW Technologies Intelligent Flap Controller. It and the flap motor are protected by a 3 amp breaker. I have never had the circuit breaker pop, and I routinely dump half flaps or full flaps at the top of the white arc, and will put in 10 degrees when operating below Va. Based on a lot of reading on flap motor circuits prior to this installation I was worried the 3 amp breaker might be too small, but Bob Newman at TCW Tech assured me it would be fine. After 50 hours of trouble free flying I'd say he was right!
 
Have ordered a 7.5 amp circuit breaker..thanks

I appreciate the very informative information! I have ordered a 7.5 amp circuit breaker from Spruce and will change it out for the 5 amp one. I think that I already have 18 gauge wiring. I hope this will alleviate the problem!
I do think that the size of the flaps on the 9 make a difference in the strain on the motor.
Joe Blank at Van's said that I should also check the resistance on the circuit to r/o bad connectors etc.
I hope that I will not burn out the motor; although I seem to remember that the breaker only protects the wiring not the motor.
 
I control my flaps with a TCW Technologies Intelligent Flap Controller. It and the flap motor are protected by a 3 amp breaker.
Click to expand...

Jim,

I visited the TCW Web site regarding their Flap Controller and there appears to be an ambiguity between their product description wiring diagram and their installation wiring diagram. The description diagram shows a 3 amp fuse or CB but their installation diagram and document clearly shows a 5 amp fuse or CB. I would really be surprised if a 3 amp fuse or CB would handle the current draw of MOST RV installations, especially an RV9 with the very large flaps.
 
Changing 5amp to 10 amp breaker for flap motor

I got my circuit breaker in from Spruce yesterday and rushed out to the airport to install it on my RV9, BUT I had had Aerotronics do my panel and I forgot that the breakers were on a main and avionics bus :(. I should have looked. Thank goodness though that they had left one 10 amp breaker as a spare on the main bus. Wouldn't you know the main bus was above the avionics bus and was really difficult to get to. After several hours and dropped screws I finally got it done. Oh! Why didn't I built a tip up canopy! It is too cold now to hang my elbow out when taxiing anyway ;)
I found that the flap controller and the flap motor were on the same breaker so that added a little to the current draw thus maybe explaining why intermittently the 5 amp breaker was opening on lowering full flaps.
 
647jc said:
Jim,

I visited the TCW Web site regarding their Flap Controller and there appears to be an ambiguity between their product description wiring diagram and their installation wiring diagram. The description diagram shows a 3 amp fuse or CB but their installation diagram and document clearly shows a 5 amp fuse or CB. I would really be surprised if a 3 amp fuse or CB would handle the current draw of MOST RV installations, especially an RV9 with the very large flaps.
Click to expand...

Well........I might have a 5 amp breaker. I wired it per the wiring diagram so perhaps it has a 5. When I wrote the post I looked at their wiring diagram because I couldn't look in the plane....my plane is 1,000 miles away being painted so I can't check. I'll repost when I get it back in January. In any event, what's in there has worked fine for 50 hours, installed in an -8.
 
Flight test with 10 amp circuit breaker -OK

I flew my 9A yesterday for the first time after changing the flap actuator motor circuit breaker from 5amp to 10 amp and the flaps extended fully (full flaps down) without a problem.
I surely am glad that Aerotronics left me a spare 10 amp breaker on the main bus!:)
By the way, I know that the max speed for full flaps on the RV9 is 90mph but what about 10 degrees. I would like to use partial flaps for an IFR approach but the approach speed is 100 mph.
 
Cleve,

In Vans construction manual for the 9 on page 15-22 they state "On the RV-9/9A, it [Flap speed] is 100 smph (statute mph) for 15 degrees and 90 smph for 32 degrees." My construction manual is about 7 years old, so this may have changed.

I always try to use 90 for any flap deployment, occaisionaly I'm a bit fast for the initial notch but with the 100 mph maximum I'm always within limits.
 
Flap motor still a problem after 10 amp circuit breaker

After my short test flight mentioned in my last post, I thought my troubles were over. I had changed from a 5 to 10 amp breaker and the flaps extended and retracted normally whereas before the 5 amp breaker would open on occasion when lowering to full flap position.
SO. I took off for a 150 mile cross country yesterday and lowered the flaps on landing at a field some hour from home. To my horror, I couldn't raise the flaps. The 10 amp. circuit breaker had not opened though. I parked thinking about trying to fly home at 80-90 MPH. After recycling the flaps several times, the flaps did retract and I took off for home. On landing back at home with full flaps, the flaps would not retract again.
I am in the process of removing the motor now and cleaning it. The instructions from Van's FAQ's make this task look daunting!
I noticed in an older post concerning this subject Paul said he could do it in 10 minutes. I surely would like to know how!
 
cleve_thompson said:
After my short test flight mentioned in my last post, I thought my troubles were over. I had changed from a 5 to 10 amp breaker and the flaps extended and retracted normally whereas before the 5 amp breaker would open on occasion when lowering to full flap position.
SO. I took off for a 150 mile cross country yesterday and lowered the flaps on landing at a field some hour from home. To my horror, I couldn't raise the flaps. The 10 amp. circuit breaker had not opened though. I parked thinking about trying to fly home at 80-90 MPH. After recycling the flaps several times, the flaps did retract and I took off for home. On landing back at home with full flaps, the flaps would not retract again.
I am in the process of removing the motor now and cleaning it. The instructions from Van's FAQ's make this task look daunting!
I noticed in an older post concerning this subject Paul said he could do it in 10 minutes. I surely would like to know how!
Click to expand...

Cleve,
Hundreds of RV-9's are flying with a 5 amp circuit breaker protecting the flap circuit. Raising the amperage rating of the protection is never the way to solve a problem when the design has proven it self to work properly with the lower value. I would suggest you keep searching until you find the issue so that you can switch back to the 5 amp breaker.
 
cleve_thompson said:
After my short test flight mentioned in my last post, I thought my troubles were over. I had changed from a 5 to 10 amp breaker and the flaps extended and retracted normally whereas before the 5 amp breaker would open on occasion when lowering to full flap position.
SO. I took off for a 150 mile cross country yesterday and lowered the flaps on landing at a field some hour from home. To my horror, I couldn't raise the flaps. The 10 amp. circuit breaker had not opened though. I parked thinking about trying to fly home at 80-90 MPH. After recycling the flaps several times, the flaps did retract and I took off for home. On landing back at home with full flaps, the flaps would not retract again.
I am in the process of removing the motor now and cleaning it. The instructions from Van's FAQ's make this task look daunting!
I noticed in an older post concerning this subject Paul said he could do it in 10 minutes. I surely would like to know how!
Click to expand...

I have a slight problem with my 6A's flap motor, but it's from the late 90's and could be different. Where the two wires come out of the motor, against a piece of rubber or plastic for insulation from the metal housing, they were bent on a sharp 90 degree angle and frayed from being streched.

I found this by pulling the side panel between the seats off, after the flaps would not operate, and the switch was getting power. By just wiggling the wires, the flap motor functioned. As a temporary fix, I put elec. tape around each wire & anchored them with a wire tie. I will also have to take the motor apart to repair these wires.

In my case, the breaker or fuses never tripped as in a short circuit. But of course wiggling wires is not a permanent fix, even though it works in it's secured state. At 16 degrees outside, I've just lost motivation to rip the airplane apart. :)

L.Adamson ---- RV6A
 
Jammed brush in Pittman flap motor

In my continuing search for an answer to my flap motor problem on my RV9, I decided it was time to check the flap motor since the 10 amp circuit breaker didn't solve the problem.
I found that the motor was the newer design motor made specifically for Vans by Pittman. I began by removing the actuator mechanism as described on the Vans site and the removed and opened the motor. I found that 1 of the 2 brushes was jammed in the "horseshoe" and didn't "pop out" as described in the service bulletin. On closer inspection I found it deformed and probably cracked . I think that this was the problem and the only solution was a new motor.
On Vans web site a flap motor is listed for $380! A call to Vans great support however revealed this was for the complete actuator assembly. They gave me a number, 503-992-0015, to Usher Enterprises, the supplier of the Pittman motor and worm gear. They have shipped me one for $110 plus shipping.
There is one thing I learned about the process of changing a flap motor that differs from the instructions on Van's web site. The instructions say to remove the Phillips head screws first. If you do this the motor will come apart before the motor comes off of the worm gear, a less controlled situation.
I hope to have the new motor installed this weekend and I will let you know if my problem is solved.
 
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Good work, Cleve. Sounds like you've hit on the cause of the problem.

I've had 2 flap motor failures but since getting the unit rebuilt last February by the original supply, Motion Industries in NJ, it has worked without a problem. Motion was the supplier early on and their units did fail regularly because, as a Motion tech rep commented, we did not know they were going into an airplane. My unit came back looking completely different with good seals and he said it would not fail again.

http://www.motionsystem.com/

BUT, having had a couple failures in the past, the worst being after take off with the flaps extended, I don't trust the system. On a cross country away from home, if the runway is long enough, I do not use flaps.
 
I stand corrected

I said in the post above that I thought I could change the flap motor without removing the entire actuator unit. Alas, I am wrong! When I went out to the plane and looked again, it does need to come out as Van suggests.
I have edited my earlier post.:eek:
 
part numbers available for motion systems and Usher?

can you point me to the right part(s)?

had my breaker pop the other day,.. so this may be some timely info
 
rvbuilder2002 said:
Cleve,
Hundreds of RV-9's are flying with a 5 amp circuit breaker protecting the flap circuit. Raising the amperage rating of the protection is never the way to solve a problem when the design has proven it self to work properly with the lower value. I would suggest you keep searching until you find the issue so that you can switch back to the 5 amp breaker.
Click to expand...
Scott,

In my builder's manual, the sample schematic lists a 10 amp CB for the flap circuit. Granted, in that sample there are other items on that circuit. When I designed my electrical system, I elected to put one item on each circuit but retained the 18 AWG wire and 10 amp CB. Do you see a problem with that?
 
Replacing flap motor

Wallace,
A new Pittman Flap Motor (this is the one now recommended by Van's) can be ordered from Usher Enterprises at 503-992-0015. They sell the motor and its shaft. If you order it from Van's you get AND pay for the entire flap actuator assembly.

BTW, as I was replacing the flap motor, I found that my ground for the motor was not good (high resistance). This was in addition to the burned brushes. The ground may have been part of my problem.

I also found that the safety wire on the lower rod end bearing of the actuator had broken. I think that checking the safety wire will now be an item that I will check annually. I wish that I had used 2 jam nuts on the rod end instead of the just one. I watched the actuator as the flaps were cycled and the safety wire is stressed some at the start of the cycle.

I have left the 10 amp circuit breaker although I maybe would be OK, with a new motor and better ground, if I went back to the 5 amp.

I have now been flying about 4 hours and numerous flap cycles without problem so I think I will leave well enough alone!
 
Same problem...now resolved

Hello Cleve,

I had the same problem two weeks ago when the outside temps were below 0?F. The plane has two years and more than 500 hours on the hobbs. I switched to a 7.5 amp fuse...no help...then went to a 10 amp. The flap moved much slower with the cold temps and stands to reason that current draw would be greater. Then, I noticed the screws on the relays for the flap wiring were slightly loose, possibly increasing the contact resistance. I tightened the screws and went back to the 5 amp fuse. No further issues, but it is also 30? warmer as well.

Best regards,

Bill
RV-7 N151WP
Barrett IO-390
Lee's Summit, MO
 
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