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R22 overspeed on start due to throttle being fully open

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R22 overspeed on start due to throttle being fully open

Old 16th Sep 2016, 16:29
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1) Has anyone else ever had this happen or am I just a complete idiot?
2) What damage likely occurred
3) How many dollars worth of damage did I just do?
You're not the first one, it happens, which is too bad because as many people here pointed out, it's easily preventable.

Dynamic Roller said:

My own starting rule is "thumb down, feel the spring". There is no spring on the other side.
which is what we teach. Roll the throttle all the way into the override, and then let the spring bring it back to the idle position. As D.R. said, there's only an override spring on the idle side of throttle travel, so doing that you've just verified that you have the throttle fully closed, rather than fully open. As an instructor, I also twist gently closed just as the student is about to turn the key, to be sure he didn't crack the throttle open.

Arm out the window said:

The unobtrusive fingers of the examiner's left hand resting lightly on the throttle would have let him or her monitor the candidate and prevent an expensive stuff up too - it surprises me that wasn't done. It's not interfering with the test, just sensible.
During flight I will generally have my hand lightly touching the throttle so that I can feel if the governor or student are making a throttle change. During start, my hand is fully on the throttle (but lightly) so that if I have to override the student I can. Not quite the same thing as we're talking about here, but we have had two cases at our school of the governor trying to take the RPM up past 102% once we increase to 80%. In both cases the instructor was able to immediately stop the overspeed from occurring. Robinson's response: "Yeah, sometimes it does that". (I was the instructor during one of those occurrences). As an instructor you should have your hand on the throttle during all those major events (startup, mag check, governor acceleration, low RPM check).

Cylinder Head said:

Another gotcha to watch for is the habit of some pilots ticking the throttle open slightly to help the start.
Agreed. In my experience neither the R44 RI or RII needs throttle to start - correct priming will get you a start with the throttle closed. I have flown R22s that won't start without cracking the throttle but as you say, this needs to be done judiciously. Very cold weather starts are another case where starting with the throttle cracked may be required (in R22). The worry here is that it's not just "overspeed" i.e. a high engine RPM we are worried about, it's "over-acceleration", i.e. the engine gaining RPM much faster than it ever could with a propeller bolted to it. Lycoming doesn't mention this in the manual, but I'm pretty sure you can spin the fan without exceeding 102% by too much throttle when the belts are loose (or during a power recovery auto before the needles are joined).

Bell ringer mentioned that this is the reason to check that the white line on the fan is aligned - if you find it misaligned I wouldn't fly the machine. It's an indication that someone had a startup overspeed (or, possibly, overspeed/acceleration during a power recovery autorotation). If the school claims they don't bother to paint the white line when they've had the fan off, you should encourage them to do so and do what Bell ringer suggested: take a picture of the fan with your phone so that if there's any question about who spun the fan you can prove it was already spun when you flew it. But I personally would (and have!) refuse to fly a ship that doesn't have he line marked.


This is pretty common in both R44 and R22. Have seen it (from the hangar) once in an R44. Damage was fairly minimal, an inspection and I believe a mag overhaul.
It depends on the amount of overspeed. If the overspeed is less than 5% only an engine logbook entry is required. Between 5% and 10% it's a fairly minor inspection including a magneto overspeed inspection. Above 10% you have to pull the engine, disassemble it (including cracking the case). It may make sense to simply overhaul the engine at that point.

One problem is that lots of schools don't have the cash lying around to do this, so either they encourage the pilot to say it was a smaller overspeed than it really was, or they perform the 5-10% inspection regardless of how high the RPM might have gone. The problem of course is that you're asking for engine problems in the future, possibly while some student pilot is flying alone.

Given that people feel guilty about overspeeds, and that they are worried they might be charged a fee for doing it, it's not that hard for a school to pressure the student/pilot into saying it was a small overspeed. This is why I always recommend you "fly rich people's helicopters" - especially if they fly in them - they're less likely to pressure the maintenance staff to not do the required inspection. As our chief of maintenance told me once "I'm not going to jail just to save <owner's name> some money". Therefore they do it by the book and are reluctant to even trust a student to say what the peak RPM was (because really, the student probably didn't actually see what the RPM reached).

vaqueroaero said:

Seen it done in an R22 before. Sounded like a chainsaw starting up.
That's exactly what I tell people. I was in the hangar one day when a student did this and I always tell people it sounded just like a chainsaw. Terrible sound!
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