Thoughts and suggestions please.. Started the 44 today, run up normal governor confirmed on and then up through 80%.. governor took it and engine and rotor rpms ran up normally until the engine was at about 88% then there was an engine only needle spike for about 1 second of about 5% (this was a guage spike as there was no accompanying engine note increase).. then it settled down and ran up as normal to 102% engine rpm. Ran the low rpm check.. light and horn ok and then a normal run back up to a governed 102%. P's and t's green lights out (i.e governor on) and into a stable 4 foot hover. Sitting in the hover checking the greens one more time and wham... the governor grabbed the throttle and snappped it wide open ( i can only describe the force of motion as the same as when the governor takes hold at 80% and runs the engine to 102%)... engine and rotor rpm heading for the moon in a hurry so i snapped the throttle closed for a hover auto.. Following ground runs we cpould not replicate the 88% engine rmp needle spike or the governor run away, but the govvernor is no governing at the 104% red line... Now with the engineers while they check out the governor and the engine and rotor overspeed which luckily was minor as i was staring at the guages when the run happened... Has anyone heard of this or had it happen to them?? Reiterate, the governor was on, the hover was stable, there was no change to the collective pitch nor any pedal movement prior to the event.. it just ran.. I can only describe it as like the governor trying to run the engine up from 102% to god knows where in the same way it does from 80-102%... Sure got my attention
The "governor" (it doesn't govern, it is easily over-ridden) has a sensor in the magnetos which can be dirtied by oil. Had this happen straight after a 100H check whilst doing the ground run - the engine/rotor started to run away, so closed throttle. Shut down. Restarted with engineers watching avidly and it happened again.
Turned out that an engineer had been too liberal with oil in the magnetos.
I have had the same thing happen over the years. It was found to be a hairline crack somewhere in the magnetos, that opened up when it got warm after a few minutes running. It sent the engine rpm haywire
It's most likely a mag problem, your governor gets its "RPM signal" from a second set of points in the R/H mag (if I remember correctly). When you have a governor problem, the mag is the first thing to check and 90% of the time, the mag is the culprit. I have had, on a couple of occasions, the governor control box go out on me (which is rare but does happen).It resulted in a gradual increase in rpm and was easily detected by the pilot. Its located behind the L/H rear seat back and is (except for one screw) quite easily replaced. I'm curious to see what they find, so keep us posted.
Not sure if the governor systems are the same on R22 and R44 but once saw a governor run up very quickly on R22 and the fault was in the governor box itself. Soon as you let go the throttle it would drive straight upwards too quickly for a low time student to catch.
Could be a sticky fuel servo, they seem to stick around 80-90% then lets go and governor struggles to catch it. Only seems to do it on first start and can not be reproduced when engine is warm. Fuel servo has be removed and sent for repair.
if it was a run-away as described, it was possibly a cut or shortened wire from the points in the right mag (actually on the left side in the helo). The rpm signal comes from a set of points in that mag. The signal wire gets occasionally trapped between the rather sharp edge of the condenser (?..) and the mag cover. Vibration takes it to the wire and you get shorts, with a loss of signal, which the governor reads as low-rpm. Sometimes you can't find this one, as you open the mag cover all looks good. You have to really look close. IF you find the pinch a layer of electrical tape will do until you can replace the signal wire. Watch the wire routing! Don't get it pinched again. Oil in the mags is another one. Not always from too much grease in the mag, but from shot mag seals to the engine.
Same thing happened to me with an intermitent "hunting" of the mag - pinched wire.
Despite it seems rather fast the governor is actually slow. You can check this yourself. When ready for take-off raise the collective rather quickly (still smooth, please!!) and you will raise the rpm, as the correlator is acting way faster than the governor. Same goes the other way. Just barely touch the ground and lower the collective quickly (see above!!) and rpm comes down. Governors go out rarely...but you never know. I would chase the signal wire first, then the points....
I have also had the wire to the points in the mag short out, similar results. Main reaction, don't panic and override the Governor, its not the be all and end all of the R44. But same reason, when the points were put in, the wire was poked behind the condenser and slowly rubbed. Was a bit to track down though, becuase as previously stated, its not always obvious on first inspectoin, so we had changed the Govenor box and tried various other things before hunting this one down. Was just erratic though, it didn't run away past 110%, varied between 108 and 96. Did have another erractic govenor problem with which the end result was a friction problem with the govenor motor itself located behind the front pax. There is a friction washer that is a factory preset friction, and not (according to maintenance manual) adjustable in the field. Replaced the whole govenor motor and problem solved. Just as an aside on mags, had two newly overhauled mags put on, and within 45 hours, both went at the same time. Had a rough running engine for approx 8 hours, and was trying all sorts of solutions in discussion with our engineers, wasn't really fouling plugs, timing was good on the ground. Then had one mag fail completely, just on take off roll, and the second go the moment I ran on. Turned out the main set of point in each mag, the wire had been overcrimped, and bent, and a little vibration fractured the wires (Most likely the burping and carrying on that they have a tendancy to do whilst ground running, and then as it go more intermittent, more and more vibration and so on, and evenutally shorted out permanently on the mag casing. Was an interesting afternoon. chop.
You shouldn't be diagnosing your helicopter faults on a rumour forum
On the other hand - it helps to spread the word and, in this case, makes pilots concentrate on start-up. The number of pilots who start an R44 like it is their car - on the phone, chatting to pax, eyes not on instruments.
Whilst you do have a point, I Always read these threads with great interest, as they tend to make others who have had similar problems come out of the woodwork, and usually point out some valid places to look and generally serve as a good starting point for places to go and have the engineers look, if they don't already know.
No I am not engineer, but a pilot with an interest in all things technical.
Helifixer, don't really see "generalspecific" standing there mouse in one hand tools in the other waiting for instructions to fix his problem. These forums are a great wealth of knowledge and by people sharing their experiences can aid and assist others.
watch your MR blades on the R-44. In my backyard (Pacific Ocean ) there where another 2 cases of MR leading edge delamination (leading edge of the upper skin pulls up from the Stainless leading edge/spar, basically a glue failure). Times around 1100 to 1200 hrs. The latest one was only about 4 nm from the boat, but the pilot had to put it in the water - ship survived. He said he never had anything vibrating so bad
You might blame this on the salt and tunaboat environment, but I spent 3800 hrs out there and wore out 2 helis. NEVER any problems with the blades and these where really badly worn.....
Supposedly the blame is with the operator, ....says Frank &Corp.