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Engine Quit on Takeoff

J

Jim Thorne

I'm New Here
OK I need some help on where to start looking. Sorry for a long post but don?t know how to say it without leaving important stuff out. About a month ago I lost power on takeoff. It didn?t quit completely so thanks to some throttle blips and altitude I made the ?impossible turn? and got the plane back on the ground and taxied normally to the hangar.
First we checked the fuel system, doing fuel flows every conceivable way we knew how. Even tied the tail down and ran one in a ?climb out attitude?. All flows seemed to be normal.
The next thing was to download the Dynon data log. In looking that over it became apparent at the time of the incident I was producing 62 Amps and 20+ Volts. This would last for a few seconds and drop to a more normal range then spike again it did it several times. It appeared that the spikes were when the engine wasn?t running.
The next was checking the P and E mags. Brad after hearing my story suggested I send them in. They found the circuit board in the P-Mag wasn?t reliable. Both mags had been subjected to very high temps, according to Brad this could have been from the engine oil temp or the high amperage. I learned that I had the blast tubes aimed incorrectly. They have been rebuilt and are now both P-Mags.
The alternator, Van?s Nippon Denso, was bench checked twice by two separate shops. Everything was normal.
The plane was reassembled and test run. Everything seemed normal until I ran high RPM, 2000+. As soon as the RPMs climbed the Dynon showed the amps climbed right up to 60 and voltage up to 20. The engine kept running on the ground but to say the least I am not enthusiastic trying to fly it with these same conditions.
Where do I go from here?
Jim Thorne
RV7A :confused:
 
I'd do another ground run with the alternator (electrically) removed. Assuming the problem doesn't show back up, I'd conclude it was the alternator and just buy a new one (assuming it's the type with the built in regulator). It's possible that it bench tests OK because it's at room temp, but then the regulator goes wobbly at under-cowl temps, or with vibration, or whatever. I'd also carefully check the condition and resistance of all the wiring associated with the alternator and starter (in case there's a short to ground in that somewhere).
 
Engine out on takeoff!

First problem is that you don't appear to have a working over-voltage protection circuit in your overall electrical design.. Van's alternator can't be easily shutdown (see other alternator posts about ways to do this). I strongly suggest any other alternator that can be shutdown (i.e., a Plane Power type alternator with internal regulator, or an alternator with an external regulator).
Next, check the grounds between the engine and the negative side of the battery. If the ground is lost (is is a high ohmage) for any reason, the voltage reference relative to the rest of the electronics is lost, and could result in an over-voltage condition.
Next, check the battery with a load meter. Use an automotive carbon pile battery load tester that can pull hundreds of amps out of the battery. It has a voltmeter and a timer to indicate if the battery meets specifications. The battery must be in resonably good condition so the alternator has something to work against. Worst case is to substitute another battery and re-do your ground based engine test.
Next try another alternator. When they are shop tested, they are not run at the same RPM that you will typically get while on the engine. There may be something mechanically wrong inside that doesn't appear until the RPM's get high.
If the P/EMAGS have seen another over-voltage situation, you may have damaged them again. As you can see from your breif flight, these units don't tolerate over-voltage very well. They require external over-voltage protection devices to make them tolerant. So you might want to get them re-looked at before you fly again....


Jim Thorne said:
OK I need some help on where to start looking. Sorry for a long post but don?t know how to say it without leaving important stuff out. About a month ago I lost power on takeoff. It didn?t quit completely so thanks to some throttle blips and altitude I made the ?impossible turn? and got the plane back on the ground and taxied normally to the hangar.
First we checked the fuel system, doing fuel flows every conceivable way we knew how. Even tied the tail down and ran one in a ?climb out attitude?. All flows seemed to be normal.
The next thing was to download the Dynon data log. In looking that over it became apparent at the time of the incident I was producing 62 Amps and 20+ Volts. This would last for a few seconds and drop to a more normal range then spike again it did it several times. It appeared that the spikes were when the engine wasn?t running.
The next was checking the P and E mags. Brad after hearing my story suggested I send them in. They found the circuit board in the P-Mag wasn?t reliable. Both mags had been subjected to very high temps, according to Brad this could have been from the engine oil temp or the high amperage. I learned that I had the blast tubes aimed incorrectly. They have been rebuilt and are now both P-Mags.
The alternator, Van?s Nippon Denso, was bench checked twice by two separate shops. Everything was normal.
The plane was reassembled and test run. Everything seemed normal until I ran high RPM, 2000+. As soon as the RPMs climbed the Dynon showed the amps climbed right up to 60 and voltage up to 20. The engine kept running on the ground but to say the least I am not enthusiastic trying to fly it with these same conditions.
Where do I go from here?
Jim Thorne
RV7A :confused:
Click to expand...
 
I have a freind with a glass star that had almost the same problem. Same set up as you.A very dangerous situation. I know alot of people wont agree with this but I would suggest for saftey sake until you can identify your exact problem that you install one mag and remove one of the others. If you like I will PM you Scotts Email and he can explain what he went through to correct his problem although im not sure he is exactly sure what fixed it. It was ignition related though.
Ryan
 
Really unhappy!

Hello

Jim, well done your impossible turn!

I'm quite unhappy about the situation that happend to Jim quit the engine. This means if you have a electrical problem, your electronic ignition my quit and so engine power. This is in my opignion not really good and makes me quit unhappy.

I thought that a PMag will able to handle a short and over volatge on the supply lines ... at least it is what I would build in if I have to design it.

Does anybody know more here ... maybe Bill Repucci?

Thanks

Dominik
RV-7A / IO-320 / 2x PMAG / Planepower Alt /
 
Failures / Electrical Grounds

Fred.Stucklen said:
First problem is that you don't appear to have a working over-voltage protection circuit in your overall electrical design.. Van's alternator can't be easily shutdown (see other alternator posts about ways to do this). I strongly suggest any other alternator that can be shutdown (i.e., a Plane Power type alternator with internal regulator, or an alternator with an external regulator).
Next, check the grounds between the engine and the negative side of the battery. If the ground is lost (is is a high ohmage) for any reason, the voltage reference relative to the rest of the electronics is lost, and could result in an over-voltage condition.
Next, check the battery with a load meter. Use an automotive carbon pile battery load tester that can pull hundreds of amps out of the battery. It has a voltmeter and a timer to indicate if the battery meets specifications. The battery must be in resonably good condition so the alternator has something to work against. Worst case is to substitute another battery and re-do your ground based engine test.
Next try another alternator. When they are shop tested, they are not run at the same RPM that you will typically get while on the engine. There may be something mechanically wrong inside that doesn't appear until the RPM's get high.
If the P/EMAGS have seen another over-voltage situation, you may have damaged them again. As you can see from your breif flight, these units don't tolerate over-voltage very well. They require external over-voltage protection devices to make them tolerant. So you might want to get them re-looked at before you fly again....
Click to expand...

I agree with Fred, a poor engine ground to airframe / ground strap can cause all kind of problems on an electrical system. Engine electrical accessories are hunting for a good ground through any device it can find; ignition system P-lead shields are most common path for an alternate ground circuit, which can over tax other internal electronic ignition components. I have seen failures with other after market ignition systems, such as P-…. as well as from my own G3i series EI out-put. (However, G3i systems still have the option to default back to magnetos and continue with ignition operation management). My findings were, no engine ground strap and/or poor ground issues, relating back to alternator over-voltage / amperage, and other electrical component failures.

Thomas Shpakow
 
Last edited:
Yes, I have a blast tube on the alternator. In fact since my incident I have added a scoop to attempt to force more air into the blast tube. I also have blast tubes on the E & P Mags but did learn that I had them aimed incorrectly now changed.
Jim Thorne
N742JT
 
alternator

Make sure your alternator is wired correctly. I once had a miswired alternator that would increase the voltage to the field as the rpm increased.Then the output would increase , Marc
 
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