Well, now there's a thought.

The overspeed will occur if:-

1. Throttle open (rolled left) at startup.

2. Sprag clutch test done the wrong way (open not closed)

3. Lift to hover with the Gov off.

4. Switch off Gov and fly with it off incl. major collective movements in flight

5. In autorotation where the collective is not lifted slightly (more 44 than 22).

The Lycoming engine will roar a bit if the engine is hot/ warm but the tacho should not rise above 65% - 70% at most with the throttle closed. If it is open a bit it may rise a bit further, but the way the engine works is based on the throttle being open to let fuel into the cylinders. Could the butterfly value have stuck open a bit? Could it even have been carb ice that cause it to be a bit stuck (could not close fully) as you ran the engine down at closedown and then started up again with the power off? Ice in a hot engine? Ist possibule.

The tacho could be a bit faulty? May overread in a start up when warm but not cold (check the sensors to see if there is a defect here).

An engine overspeed will come through in about 10 - 30hrs with metal in the oil (specific type of metal, but I cannot recall which). If it was a full open throttle then one may find that the crankshaft bolt in the air cooler fan at the back has been spun, so the wire lock will not line up with the marks. Check this now.

An engine overspeed on startup can generally be identified by the scream of the engine (in pain). If it did you may have done, so monitor the situation with an oil screen test at 10hr intervals. If metal appears, check the tacho brushes and also you may have to have the engine stripped for a full check and some bits replaced.

(NB pilots view, not engineers...)

h-r:)

It sounds like you started up with the throttle wide open, Big lesson learned.

When the engines warm and you start up you will always have a higher RPM then when the engines cold normally the ERPM will go to about 70% at the stage.

If the RPM goes above 80% and the governor is on, The governor should bring the RPM to the top of the green ark on the RPM gauge and hold it there.

One thing you should know about the governor is it has a lower RPM limit of 80% i.e. below 80% it won't work and it has an upper limit of 115% i.e. above 115% the governor will not roll the throttle down.

Don't forget it's not only the engine which can get damaged in an overspeed it's also the drive system including the tail rotor drive. As you increase the RPM the drive to the tail rotor reacts like a skiping rope and will curve into a slightly different shape (This is because of the hanger bearing. If you hit about 135% RPM you could rip the tail cone off. Did the engineer inspect the drive system? If so trust what he say's, Just remember lesson learned don't do it again, Next time you might not be so lucky.

Surely this is only when the clutch is engaged?...or am I missing something? Can you explain this?

It sounds like you are mixing this up with a rotor overspeed, where most people only think about the main rotor.

cl12pv2s

I suppose there could be massive abrasion of the belts though.

cl12pv2s - thanks for the info. I do indeed fly the Schweizer.

RotorSwede:

Check out the R22 corner thread, especially starting at page 8, third from bottom

Rotor swede

Certainly not going to say its normal for it to idle high without load but it is certainly very common, hop straight in after a shut down and it will do this,
engineering cant explane it but i put it down to the heat making the fuel more prone to vapourizing causing a leaner burn than normal.
next time you shut down let the belts fully off load to see and you will get the same thing.
The Gov will work from 80% so if this happens then its going to jump to 104. Do your CXs, the gov should be off at start for this reason.
Remody - expect it to happen, dont delay in engaging the belts and minumize the time at high idle, GOV should be off to avoid it taking it up to flight speed with no load (not a nice sound)
It will idle high when warm - it aint broken. your only problem was the gov was on.
:O

Quick Release:

Correct me if I'm wrong, but the latest version of the checks say that the governor remains on all the time - even at start.

Nr is right, QR is verging on the irresponsible, and IMHO the owner and engineer are in denial. The man's post says that he saw MAP of 25 inches with the clutch disengaged and even with manual throttle he couldn't get the engine revs down to the yellow. In anyone's book that's an off the gauge overspeed, so if it went down as he says and he told that same story to the engineer, then I'm with kissmysquirrel. Practise your autos or fly something else. Either that or be prepared to kissyourass goodbye.

Hi KMS & cl12pv2s

Sorry your quite right about the clutch, Must use brain before I post. I had been a long day though.

Just to confirm from the last few post's the governor should be on at start up (Robinson changed the check list and decided to have the governor on to avoid overspeeds)

Thanks for the swift respons on my question.

I've talked to the technician myself now, after the incident I just told the owner and my former instructor. Now I personally explained to the technician what happened. But he had heard it from the instructor already.

The machine has had som previous trouble with the exhaustvaults getting stuck. So in respons to that problem he has examined the engine. Says everything looks good. The guy has a good rep so ... But I got the impression that some guys here meant parts had to be replaced?

Not meaning to distrust the certified technician, but since I'm gonna pilot the machine it's good to get other pilots / technicians opionions.

What does the RHC manual recommened should be done? Say that the worst happened, both engine rpm and manifold preasure gauges hit maximum for 1 sec before I got the situation under controll.

RotorSwede
 

25 in. is maximum take off power you used to just turn the engine. however this is only true at 100% rpm. but it does mean there was no real restriction in the inlet manifold,so the throttle was probly open wide.
also its usual somtimes when there hot to idle in the yello till the clutch is engaged.

the overspeed is a hard one, yes its probly been overspead, yes it should be reported, yes it should probly be overhauld. these things are in place so that the helicopters safety is not effected. but getting the engine out, sending it away for testing, then getting it back because there was nothing wrong with it and then putting it back in all costs time and money when it might not need it.
being warm the engines parts are at their operating size so everything has the right tolerances and there would be remaining oil around bearings so as far as that goes it would have not much effect, its the stretching of reciprocating and spinning parts that is the problem which relates to the rpm x time it was over reving.
you did report it and under the circumstances the enginear said its ok. he probly knows.
surely streched big end bolts would make big end noise and stretched conecting rods higher compresion, easy to check.

:confused:

I'm definately no expert on the R22.....

But, I am under the impression that the 'guvna' would be able to keep the engine at 104% without too much trouble. One of the good design freatures of the R22 is the governor. It takes it's information from the magnetos so has an instant response to an overspeed regardless of whether the rotor is engaged or not... it dosn't care.

I understand that there will be inertia withing the counterweights etc tucked away inside the casings causing a short rpm spike above 104, but these engines normally run at 2700 rpm at 104% so any small increase above that due to inertia will still be within lycoming's exceptable rpm limits.

You have to remember that there is 'no load' so the stretching etc from a fast accelerating engine is not a problem as 'there is no load'...... Having said that, it may be argued that the squirrel cage blower is producing a small consistant load.

An overspeed (as apposed to high accelaration) due to full throttle and NO governor is certainly a problem if encountered.

Cheers

I dont think the gov' will save the engine from an overspeed at start up if the throttle is fully open. It would be beyond the gov' operating range, and it's not that quick on the draw ...


h-r:)

Thread hijack...sort of!
 

Just to 'hijack' the thread slightly...

re. Something I brought up when Robinson made the August 2004 changes which requires the governor to be on before start, and before shut down...

Using this new revised checklist, it is possible that an aircraft can go a number of flights with nobody seeing the 'Governor Off' light illuminated!

(Granted in a training aircraft, this is less likely as 'govenor off' ops are practiced)...

...but with normal operations, the govenor will be on from the moment you get in, to the moment you get out. How then do you know the 'Govenor Off' bulb is still working or the connection to the switch is still working?

So I propose a suggestion for anyone who may have overlooked this.

During the preflight check, when you do the warning lights (in the engine cowl), you write into your checklist:

Govenor Switch Off.............Check Light On
Govenor Switch On.............Check Light Off

While I'm sure most pilots will already be doing something like this, maybe I have helped one or two!

cl12pv2s

Sorry NR fairy, been away too long, not looked at an R22 check list for quite a while. Stand corrected.

Hey Ponto" you calling me irresponsible? you F*** idiot!!
go ahead mate, leave your GOV on and rev its ass off when when the above mentioned problem occures.
Ask your self why robinson changed the check list??
it was to prevent idiots from starting with the throttle open, at least it stops it from going through the roof preventing at least a massive over speed.
you dont even know me and you call me irresponsible, what a joke.

I always switch off and then on again before winding up during start. To be sure, to be sure.

h-r:)

QR maybe the issue is that your post starts with the premise that this engine just 'idled high'. What Rotorswede actually said was that he saw 25 inches power with the clutch out, unable to wind the throttle down below the (TOP!) yellow arc with a single handful, engine screaming.

Are you seriously saying that if someone reported this sequence to you, on a helicopter you had responsibility for, then you'd say no worries mate, it'll be OK ? If no, then I'm happy to retract 'verging on the irresponsible' but if yes, then it has to stand.

I believe Dick Sanford in the UK did an experiment on a gash engine that had already been oversped and showed that the governor could not stop an overspeed when started on full throttle. Me - I can't afford the experiment, but we're paranoid generally about starting with the throttle closed even under this new "governor on" regime.

Under the Robinson R22 Daily or Pre-flight Checks

1 COWL DOOR

Master Switch...............................................On
Strobe & Navigation Lights...........................Check
Oil pressure, alternator,Gov. Lights..............On


Then Before Starting Engine checks about half way down is

Governor.................................................... ...On

H.

seen quite a few changes on the robbo checklist over the years. Flying one now born june 2004 and the checklist says gov off prior to start.

teach my students to start gov off, throttle shut off course.

On warm up 70 75% rpm (used to be 75 - 80%) gov kicks in at eighty and races up.

You need to be ready for the split needles when they wind it right open!!!!!!!

punto..... so i didnt read or try interpret the original post as well as i should, but offering, if nothing else, another problem that presents its self, my end statment "this was your problem" yea a bit of presumtion on my part without thinking, so if Swede' reads he would know im not talking about his situation anyway so he can disregard what i said.

but it aint for to come on here slandering folk for posting regardless.

I am the first at work if suspect even an engineer not following up things like this, would pull the maint: manuals, and get them to show me every thing was done as prescribed,
so irresponsible im not.