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Stuck Impulse Coupler? Stranded (Sorta

Ironflight

Ironflight

VAF Moderator / Line Boy
Mentor
OK, here's a quick one for the experienced mechanics reading this morning because it's too cold to go outside....

We had to leave the RV-6 up on the ramp in College Station yesterday evening - wouldn't start. They have no pre-heat or hangars available, so we ran the battery down trying to get it to fire. I then went to hand propping, and had similar luck. We did manage to flood it, as evidenced by dripping gas at one point, so I know there is fuel.

I woke up in the middle of the night while mentally making a "tool list" for today's rescue mission, and realized that i was getting no impulse coupler "clicks" as I was hand propping - so I suspect the IC is stuck/broken...not working.

So...I anticipate pulling the mag to check this - any advice on how to check it, what to look for - or how to pull it in the field? I have two other mags with good impulse couplers but bad coils - I can't recall having pulled an IC before - do I need any special tools?

Headed up there when it gets warm this afternoon if anyone has any good words. It's good to have multiple airplanes at times like this....

Paul
 
Paul,

Just be sure that if the impulse coupler broke, that no parts fell into the accessory case.....
 
Sometimes the impulse couplings won't snap if the oil is cold and the springs are weak. I would make an effort to give it a good preheat and not try to fix that on the ramp. You've likely not endured the pain of rewinding an impulse coupling spring...trust me you won't want to do it away from home. Bring a can of starting fluid (ether).
 
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Cant pull the impulse without a special puller or you can damage the mag. Would be better to pull the coil and change but that too requires a special tool if it is a Slick mag. The coil is held in with wedges that can be quite tight. If Bendix the coil comes out very easy. To check impluse just make sure the palls can swing free and catch on their stops on the mag case with the mag in the position it would be in on the airplane. If they are tight or gummed up they sometimes will not work free and not catch ....especially when it is cold. Also check for broken spring...although I have never seen one break. Uou can feel the impluse wind up as you turn over the mag. It is best not to snap the mag as it can cause carbon tracks in the mag distributor block unless you put wires in each hole and ground them to the mag case.

Dave (Swift Driver)
 
Paul,
I have a slick mag with impulse coupler in my tool box, I'll fly it down to you on my way to Hicks if you need it, I can also bring some tools with me.
I also have a PC680 charged and ready to go.
 
I have had success by pulling the mag and washing the impulse while it is still on the mag in avgas and relubing it with light oil , they get gummed up since they are on top of the accessory case and all the evaporations from the lower case end up there.
 
Great inputs from everyone - thanks! I knew that there were some tricks to workign with the IC (thanks for the videos Russ!), and having dealt with more than a few lawn mower recoil starter springs, I wasn't looking forward to exploring this in the field.

Walt - I might give you a call up at Jay's - we are not going to get up to KCLL until early/mid afternoon (it's gotta warm up before we do anything) regardless. If you had that with you today, it woudl be great!

So another question - if it's just hung up because it's cold and the grease is sticky, has anyone just pulled the mag and (carefully) shot the IC with LPS to free it up? {ed - Ahh...I see Jim answered this one while I was typing - thanks!}

Yeah, we're going to have to look at long term solutions, but just want to get it home first...

Paul
 
Just make sure the pawls will drop out easily before you put it back in...
this fix usually works for a long time if you fly it often and keep the gunk cooked out of the crankcase.
 
Ron Lee said:
What do you mean by "warm up?"

You are in southern Texas.
Click to expand...

Hey, I grew up in Minnesota where we drained the oil at the end of the day, and warmed it up on the stove the next morning to pour it back in the Cub that sat outside.... Down here, they've never seen a pre-heater, and don't know anything about the "pre-heat below 40 degrees" because it almost never gets there.....almost!

And Walt, if you're still tracking, we got a Mag from a neighbor, so we're good - thanks so much for everyone's words and offers of help.
 
Our Cub has a brand new set of Slicks on it with less than 200 hours on them. If its cold a lot of the time they won't snap. It just takes a bit more muscle to start when that happens. You don't need impulse couplings to start an engine but it does make them start easier. So don't go create work for yourself, warm the engine up, charge the battery, no prime, 1-2 pumps on the throttle after the 2nd blade and it should fire up.
 
Yeah - good point Bob - I just finished loading the val with everyting we need to swap the Mags, but it sure won't hurt if we get up there and the temps are 60 degrees to give it the old college try first.... :)
 
Mikey's home - and RocketBob was right - Louise got in and he started right up - 60 degrees. We'll probably pull the mag and clean up the IC in case the winter decides to get cold again, and she has to be up there. Of course, now she can always take Junior or the Val on those kind of days....

Paul
 
Man I wish my Wife could fly.

1) Because it seems way less dangerous than having her drive (even thoug GA statistics show otherwise)

2) She wouldn't be relying on me to take her/go get her.

..:)

Frank
 
Not so

Ron Lee said:
What do you mean by "warm up?"

You are in southern Texas.
Click to expand...

Here is a picture of us picking up our -6A in Texas...February 2004:

TexasRVinback.jpg


Check out the white stuff to the left of the U-Haul:)

We were near Houston:

TexasRV.jpg


It was Valentine's weekend:)

Best,
 
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