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Flap Motor Question

bhester

bhester

Well Known Member
Patron
Ok my flap motor quit again for about the fifth time. I've always cleaned the brushes and put it back together. Last time I ordered a new one and put it on the shelf. It is always because of a little grease on the brushes. This time I took the actuator arm (screw) out of the aircraft and cleaned the little threaded area that the motor gear turns. I sprayed it out real good with contact cleaner and got all the grease out. After cleaning the factory grease off the motors little gear I put the new motor on the arm and reinstalled it. During the test run I noticed that when it goes down and reaches the bottom the motor runs and the arm free wheels, when I take it up it and it reaches full up then the motor bogs down and quits while I'm still holding the switch up. I thought it was suppose to free wheel at the end of both directions.
I'm am loosing it? What's up guys?

Added info: I've got between 350 - 400 hrs on the plane
No the UHMW blocks are not tight on the rod.
 
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My solution?

Bobby,

It sounds like you're doing all the right things. It's no secret that these flap motors can be tempermental. I read many threads on here while building and rigging the flaps on my 7. When looking at the setup from Vans (OEM) I never really liked the idea of the "free wheeling" motor taking care of itself when reaching the ends of its travel. Consequently, I installed limit switches on the top and bottom of my system. The motor stops completely in the same place every time with no need for free wheeling. I'm at almost 300 hrs. and no problems so far.. (knock on wood). I have the schematic for the flap system if interested. It's very simple. Just a thought...

C....
 
ccarter said:
Bobby,

It sounds like you're doing all the right things. It's no secret that these flap motors can be tempermental. I read many threads on here while building and rigging the flaps on my 7. When looking at the setup from Vans (OEM) I never really liked the idea of the "free wheeling" motor taking care of itself when reaching the ends of its travel. Consequently, I installed limit switches on the top and bottom of my system. The motor stops completely in the same place every time with no need for free wheeling. I'm at almost 300 hrs. and no problems so far.. (knock on wood). I have the schematic for the flap system if interested. It's very simple. Just a thought...

C....
Click to expand...

I would be interested in viewing your schematic. Is it posted online somewhere? How about photos of the installation? If not posted, could I impose and get an email copy? :eek:
 
Wow, that's crazy. How many hours do you have on the airplane?

I have about 350 now and haven't had any flap motor problems at all.

One thing I've noticed is that a *LOT* of builders insist on torquing down the AN3 bolts that hold the various UHMW blocks in place with "standard" torque. This is absolutely not the correct thing to do as it will compress the UHMW blocks and put considerable drag on the flap system. When you disconnect the flap motor (which is sounds like you've been doing a lot of) how easily can you actuate the flaps by hand?
 
It's probably the vintage of the motor more than anything... I know some folks who got their kits before I got mine (whenever you get the motor?) and they had to do this whole ritual several times.. Mine never quit in 300+ hrs and I never had to clean it etc.. I guess there was some change at some point and we just lucked out?
 
Might need to

ccarter said:
Bobby,

It sounds like you're doing all the right things. It's no secret that these flap motors can be tempermental. I read many threads on here while building and rigging the flaps on my 7. When looking at the setup from Vans (OEM) I never really liked the idea of the "free wheeling" motor taking care of itself when reaching the ends of its travel. Consequently, I installed limit switches on the top and bottom of my system. The motor stops completely in the same place every time with no need for free wheeling. I'm at almost 300 hrs. and no problems so far.. (knock on wood). I have the schematic for the flap system if interested. It's very simple. Just a thought...

C....
Click to expand...

ccarter I might need to do that, I was hoping that I would not. If you have something that you could send electronically, I'll take a look. My direct email is on my web site. Thanks!
 
Adjustment? Maybe the flaps are binding motor up before reaching top. Unhook from flap mechanism and see if it freewheels at the top.
 
I think if you add limit switches you're adding more complexity where you really don't need it. The RV-7 flap motor free wheels at both ends and if yours is not doing that there is an issue somwehere that needs to be fixed. Installing limit switches simply covers up the core problem, IMO.
 
My experience

I've had trouble with my flap motor several times. Each time taking it apart and removing some black residue that looked like grease with alcohol and a Q-Tip from the motor and brushes as recommended. I had already cleaned out the excess grease from the gear housing previously, leaving just a minute amount on the gears (as per the manufacturer's recommendations).

This time I made sure to gently brush clean the motor internals with rubbing alcohol. I found that the Q-tip method is not thorough enough. The motor internals need to be soaked with a gentle solvent and paint brush. In particular I found grease residue in the brush holder... obviously when the brushes are seated back into their holders, what little remaining grease that remains in there will migrate down to the rotor contacts and mess things up. Time and heat will soften the grease and allow it to flow past the brushes onto the rotor contacts.

In my case I had already ordered a new set of brushes, so I just replaced that assembly. I cleaned out my old brush set too, so now I have a spare set should I need it again, however I am hopeful that this is the last time.

In summary, my recommendation is to do a thorough cleaning with alcohol and a small paint brush, especially with regards to the brush housing. That whole housing should be dunked in alcohol and gently brushed clean.
 
Flap system with limit switches

Bobby,

Here is the schematic I used. There are a variety of limit switches available out there. I think I ordered mine from Mouser electronics. They're on the web. I used a 5A switch for each position and created mounts to capture the flap weldement travel in both directions. It was really not that hard and its worry free when deploying and retracting the flaps. I thought this setup gave me a function very similar to a flap position system without the high cost. My field tests of the flap motor while building made me uneasy about the free wheeling of the motor coupled with the frequent reports of motor failures. I think the motor failures were mostly due to contaminents building up on the contacts etc. The idea to help reduce this is less rotation over time means less wear over time. One of my build goals was to lower cost of ownership by reducing maintenance as much as possible. This is certainly not the only good way to do it but it worked for me.

I sent you a pers. email with all the info.

flaps_scheme1.jpg
 
Jamie said:
One thing I've noticed is that a *LOT* of builders insist on torquing down the AN3 bolts that hold the various UHMW blocks in place with "standard" torque. This is absolutely not the correct thing to do as it will compress the UHMW blocks and put considerable drag on the flap system.
Click to expand...

Instead of leaving the nuts loose, you should use a combination of AN960-10 and AN960-10L washers between the two blocks as a shim. This makes up for the kerf and restores the hole to it's symmetrical shape.

Then you can torque the nuts to the proper value and you're good to go. Everything is torqued correctly and still moves freely.
 
Phil said:
Instead of leaving the nuts loose, you should use a combination of AN960-10 and AN960-10L washers between the two blocks as a shim. This makes up for the kerf and restores the hole to it's symmetrical shape.

Then you can torque the nuts to the proper value and you're good to go. Everything is torqued correctly and still moves freely.
Click to expand...

Not exactly true, although the kerf is something to consider. If you torque them down to 20-25 inch-pounds the UHMW will still *visibly* compress and distort the blocks.

I have seen people drill those holes large and put rigid aluminum spacers in the holes to prevent distortion of the blocks.
 
Phil said:
Instead of leaving the nuts loose, you should use a combination of AN960-10 and AN960-10L washers between the two blocks as a shim. This makes up for the kerf and restores the hole to it's symmetrical shape.

Then you can torque the nuts to the proper value and you're good to go. Everything is torqued correctly and still moves freely.
Click to expand...

Instead of using washers, after you cut the block in half, clamp the block back together in a drill press vise and rebore the hole with a 1" spade bit.

Now use a nylock nut and tighten down just enough to hold in place
 
Jamie said:
Not exactly true, although the kerf is something to consider. If you torque them down to 20-25 inch-pounds the UHMW will still *visibly* compress and distort the blocks.

I have seen people drill those holes large and put rigid aluminum spacers in the holes to prevent distortion of the blocks.
Click to expand...

Give it a shot. You won't be disappointed.
 
Block is not the problem

Phil said:
Give it a shot. You won't be disappointed.
Click to expand...

The block and it's torque is a ok. It appears that I had the lollipop adjusted out too far and the shaft was not extending completely. I screwed it all the way in and it now free wheels but it wouldn't hurt for it to extend a little more. I need to work on it a little more this weekend.
 
Flap limit switches

A quick note about the flap limit switch circuit above: this arrangement has a hidden benefit of providing dynamic braking when a limit switch is closed. In practice, this simply means that the flap motor stops quickly at the limit, without excessive coasting. The result is very consistent and repeatable flap position at the travel limits. Not too big a deal, but handy, since it eliminates the need for a hard travel stop.
 
bhester said:
The block and it's torque is a ok. It appears that I had the lollipop adjusted out too far and the shaft was not extending completely. I screwed it all the way in and it now free wheels but it wouldn't hurt for it to extend a little more. I need to work on it a little more this weekend.
Click to expand...

Did some more adjusting and I've got full travel now and the flap arm free wheels at both full up and full down.

Thanks for the help guys.
 
Check easy stuff first

Hey guys,

Funny story for you, now that it's almost over. Seems obvious now, but maybe this will save someone some grief. I'm at about 120 hours, and started having intermittant flap ops a week or so ago. I searched the forums and found all this great info about excess grease inside the motor, so I figured I go out and clean my motor. Took me an hour or so to access the motor and get it apart, where I found.... nothing. Clean as a whistle. So took me a little while longer to put it all back together (how do all those 6 little washers go back?), and THEN decided to check the voltage at the motor. Getting voltage in the down direction, but not the up. So, ran out of time at the hangar, but narrowed it down to the button on the stick, or more likely, my crimp on the wire at the stick. I've got a VP electrical system, so it was easy to reconfigure the power control to the flaps from the stick buttons to one of the built in switches I used for wig wag. So I got the flaps working, and tomorrow I'll try and find the problem and get my flap control back on my stick. Point of my story is CHECK THE EASY STUFF FIRST. I fell into that trap of just because everyone else's flap problem was excess grease in the motor, that was my problem too... had to be. Nope.

Seriously, can anyone tell me how those washers are supposed to go? Three little silver ones, two little black ones, and one bigger black one.

Safe flyin,
 
flap motor

hey guys..im new to the site. im a student pilot..but i have a hard question. if my flap motor is burned out
where do i look to see if its even required?
am i allowed to fly with it inoperative (airworthy)?
what we have to do with this to make it operative?

thanks guys...these r questions my flight instructor asked me...ive searched everywhere and cant find the answers...if you could help i would greatly appreciate it
 
BTW, the Vertical Power flap system includes dynamic braking (stops the motor instantly) and motor run-on protection.
 
ufahmad said:
hey guys..im new to the site. im a student pilot..but i have a hard question. if my flap motor is burned out
where do i look to see if its even required?
am i allowed to fly with it inoperative (airworthy)?
what we have to do with this to make it operative?

thanks guys...these r questions my flight instructor asked me...ive searched everywhere and cant find the answers...if you could help i would greatly appreciate it
Click to expand...

Welcome to VAF.
 
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Is your CFI testing your knowledge? What it allowable inoperative equipment? And whether or not you can fly without electric flaps? In that case, it's time to head to CFAR part 91!. You'll find your answer there.

I will give you a hint however (sorry I am a CFI so I have to play the same silly head game). Flight with inoperative equipment is allowed provided that it does not violate three factors:

1. Certification requirements (did the manufacturer receive certification with the equipment deemed required "R" or optional "O" or additional "A"). The "R's, "O"'s and "A"'s are found in the equipment list of certified aircraft. RV's have none.
2. Regulatory requirements (good ol Part 91) - Is the equipment listed as day VFR required, night, IFR, etc.
3. Operational requirements (how you're flying the plane) - Are you flying VFR, IFR, Short field etc

Additionally, a PIC must make the decision that the aircraft is safe for flight, not withstanding any of the above factors.
 
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apkp777 said:
Is your CFI testing your knowledge? What it allowable inoperative equipment? And whether or not you can fly without electric flaps? In that case, it's time to head to CFAR part 91!. You'll find your answer there.

I will give you a hint however (sorry I am a CFI so I have to play the same silly head game). Flight with inoperative equipment is allowed provided that it does not violate three factors:

1. Certification requirements (did the manufacturer receive certification with the equipment deemed required "R" or optional "O" or additional "A"). The "R's, "O"'s and "A"'s are found in the equipment list of certified aircraft. RV's have none.
2. Regulatory requirements (good ol Part 91) - Is the equipment listed as day VFR required, night, IFR, etc.
3. Operational requirements (how you're flying the plane) - Are you flying VFR, IFR, Short field etc

Additionally, a PIC must make the decision that the aircraft is safe for flight, not withstanding any of the above factors.
Click to expand...

Tony can correct my misstatements, but I think it is a little more complicated than he suggests. A quick look at a C172SP POH shows that flaps are not on the required equipment list, but neither are ailerons or elevators --- and they're not optional or additional either! But they do exist. So how should they be treated?

Of course, ailerons and elevator are required for safe flight, so the question is whether flaps are. The use of flaps is almost certainly called out in the emergency procedures, so whether or not you intend to use flaps, I think the FAA would deem that flaps are required for the aircraft to be airworthy, unless there are alternate procedures to use if they are inoperative.

Indeed, all Master Minimum Equipment Lists contain a standard preamble with the statement, "The FAA approved MMEL includes those items of equipment related to airworthiness and operating regulations and other items of equipment which the Administrator finds may be inoperative and yet maintain an acceptable level of safety by appropriate conditions and limitations; it does not contain obviously required items such as wings, flaps, and rudders."

I appreciate Tony not trying to give anything away here, but the FARs regarding minimum required equipment are notoriously confusing, and I think it's worth answering directly.

There is a good web page on the topic of operating with failed equipment here.

As an aside, if the flap motor failed in flight, you would be required to report the incident to the NTSB "by the most expeditious means available", since flaps are part of the flight control system. (49 CFR 830.5)
 
It's true that the subject of inoperative equipment and MEL's is a confusing part of the FAR's. However, generally speaking MEL's don't apply to most light GA aircraft and certainly not RV's. Still, your instructor is wanting you do do some research and come to some understanding of the subject. I doubt most pilots could tell you why or why not it would be legal to take off without flaps. Probably some FAA inspectors couldn't either. But what you need to know is that there is a matrix (not the movie) that you need to flow through to determine if a item is required.

For example a Vaccum Pump fails on a small plane used for day vfr.

1. is it required by type certificate? No, it's an additional piece of equipment in most cases.
2. Is it required by regulation? No, FAR 91.205 doesn't mention it.
3. Is it required by operation? No, flying VFR.

So, is it safe to fly without it? Well here's the problem. First, do you know WHY it failed. Was there a leak in the line, a vane failure or a gear failure that is in the process of destroying your engine.

Here's where the PIC must make a PIC decision. Do you really want to fly with ?'s about the mechanical soundness of your plane? Did I mention were flying day vfr or should I say, for fun.
 
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