Governor caused a strange overspeed today

[cherminator]

A couple of weeks ago I started noticing a "tick" in my engine rpm gauge on the first start-up of the day in my 2007 R44 (180 hours on it). The needle would "tick" upwards quickly a few times then settle back down, like a nervous twitch. Rotor rpm stayed the same. We figured it was probably just a faulty gauge as nothing else was affected.

 

Today things took a turn for the worse. After running the engine up to normal operating rpm, while I was adjusting the radio, I heard the engine rpm spool up to a level I'd never heard before. I quickly looked at the engine rpm gauge as I reached for the collective and saw that it was at about 110%. I quickly rolled the throttle back to the green on the gauge and could feel the governor fighting me the whole way back. When I had it stabilized, I relaxed my grip on the collective to see what would happen and it immediately tried to overspeed again. I then rolled it down to 70 % to let it cool down a bit, then shut her down. As I rolled it down to 70 % I saw that strange "tick" in the engine rpm needle again.

 

My engineer figures it is bad points in the mag(s). He's coming to take a look at it in the morning.

 

Have any of you experienced anything like this yourselves? Any other ideas what it might be? I'm also looking for recommendations on what should be done about the overspeed situation.

[Little Red 22]

Day 3 of my Robinson Safety Course was taught by their mechanic, Efrain Vargas. On page 3 of his handout is this statement, "Magneto problems are source of almost all governor problems." Haven't experienced the "ticking" and overspeed, but the governor in our R22 had slightly "sluggish" behavior just before it was determined that our alternator had 2 burned out diodes.

[Pohi]

You could also check the wiring. We had a faulty connection in that wire bundle that is located on the forward bulkhead of the engine compartment, copilot side. One of the wires worked itself somewhat loose and caused all sorts of chaos.

 

As far as the overspeed, I think one of your maintenance manuals or service manuals will address this.

[cherminator]

Thanks for the tips guys.

 

I had the points in the right mag replaced yesterday. When they came out they looked fine, but we replaced them anyway. Started it up, everything seemed fine. Went out to practice sloped landing today and the same thing happened again. My instructor was with me this time so he was able to experiment with it a little bit and even took a video of the engine RPM needle dancing around.

 

We're going to replace the whole mag tomorrow.

[Goldy]

Thanks for the tips guys.

 

I had the points in the right mag replaced yesterday. When they came out they looked fine, but we replaced them anyway. Started it up, everything seemed fine. Went out to practice sloped landing today and the same thing happened again. My instructor was with me this time so he was able to experiment with it a little bit and even took a video of the engine RPM needle dancing around.

 

We're going to replace the whole mag tomorrow.

 

Governor issues are frustrating because they can be caused from several sources. Hit and miss and changing parts seems to be the only way mechanics troubleshooot anymore. It's an expensive way to go.

 

Spindle bearings is what wears out first in an overspeed. Even if the mechanic says all is well, be sensitive in another 10-50 hours if you start to feel an increased vibration in the cyclic, loss of forward airspeed or excessive stirring. That seems to be the best symptoms when your bearings are shot.

[Trans Lift]

I had the exact same thing happen the last day (luckily I caught it before it oversped) and it was the small wires at the mag, not the mag itself. There is a little white plug at the mag just above the oil filler and we sprayed in some brake fluid cleaner and checked the connections. Our mechanic said it could have been some oil on the wire causing a bad connection. Seemed to work fine after. Check those wires and give them a good spray and make sure they're clean.

Edited June 18, 2011 by Trans Lift

[Pohi]

You could try turning the governor off, spinning it up and watching the tach needle while messing with the wires. Not exactly a technical approach, but that's how we found the faulty connection on ours.

 

Takes two people, of course, but it may greatly minimize troubleshooting time.

[Brian Wallis]

If the aircraft is fuel injected, I have seen this. Only on first start of the day would 7H run up and go over the 100% RPM mark. The pilot would have to catch it. It would only happen on first start of the day. We tried everything. There is a little diaphragm in the fuel servo that was broken. It would cause it to go over RPM only of first start of day. My email is brianpwallis that the common email server that begins with the word hot.

Best

Brian

[cherminator]

Thanks for everyone's help with this. We replaced both the mag and the governor module.

 

Put about 5 hours on the machine since and all seems well.

[Pohi]

So, what was the actual problem, if you don't mind me asking?

[cherminator]

So, what was the actual problem, if you don't mind me asking?

 

I haven't heard what the actual problem was. I don't know if the engineer took the magneto apart or not. All I know is that replacing it with a new one seems to have fixed the problem. We changed the governor module as well just in case, as he lives in another town and I didn't want him to have to come back a third time.

[Pohi]

I see.

 

Thanks for the reply,

Fly safe

[Goldy]

I haven't heard what the actual problem was. I don't know if the engineer took the magneto apart or not. All I know is that replacing it with a new one seems to have fixed the problem. We changed the governor module as well just in case, as he lives in another town and I didn't want him to have to come back a third time.

 

Glad the problem was fixed...unfortunately it was using that expensive shotgun approach I was speaking of!

 

You would think there would be some sort of tester you could install between the mag and gov module to help troubleshoot.........hmmmm......me have an idea now.

[nightsta1ker]

Another way to check for bad bearings after an overspeed (or suspected overspeed) is to climb up right after the flight and put your hand on the bearing housing. If it is warm to the touch, your bearings are about done!

[BigBird7]

On a R44 Raven II, during the first start of the day, the engine attempted an overspeed with governor on. During shut down, engine off, battery on, I noticed the engine RPM gauge "Ticking" multiple times. Interesting.