R22 Engine and Rotor RPM Overspeed(past red line) - Help!

[ifresh21]

Hi guys,

I had a helicopter lesson yesterday. My usual instructor was unavailable, so I flew with another who is a new instructor w/ approx. 300hrs. I had flown with him once before. I am near solo so we decided to stay at the airport - our first maneuver of the day was to be a normal closed traffic/approach/landing.

We were on final gradually descending(descending from 300agl) when I started to feel the throttle getting rolled off a little. I was thinking like whats going on- I figured it was the instructor and the throttle only went down a little so I didn't really worry. I then heard the low rpm horn and after a little thought I realized its probably a test. So as per the POH, I lowered the collective and rolled on the throttle. The collective went down by maybe 50% (pretty close to autorotative position, I believe I heard the autorotation sound a bit but I didn't go that far because of what I heard next). The throttle went on quick and hard, I was probably at full throttle. Things sounded really loud (I don't have an active headset so I can hear the engine noises, I consider that to be an important sense during flying) as the RPM increased so I looked down at the RPM gauge(engine side) and it was well above the red area/red line of rotor rpm side. Based on sound and me getting a chance to look at the gauge it felt like the RPM was up there for a period of time. I want to say less than/about 3 seconds. This all happened very quick and I was quite surprised so its hard to say exactly (crazy thing is I always fly w/ a camera and I forgot to charge it that day). The rpm went down (I guess he fixed it, happened quick) and I landed and set it down.


So that is the narrative of what happened. At the end of this post is a pic of where I remember the RPM going to during my glimpse of it (tiny red line I added).

I asked the instructor when we got on the ground hes like we don't want that to happen again. I asked him but what about right now - he said its fine cause he got it down real quick. He opened the door and checked for bearing sounds. (I can give the full narrative if you want) This was the first thing we did and total flight time was 1.6 hours.

So how bad is this, what should I do, and ultimately could someone be killed because of this(in the future due to maybe structural damage), if so - what can I do to prevent that.



http://i51.tinypic.com/21map2s.jpg(not my pic or the incident helicopter)


Thanks a lot in advance for help guys

[Daysleeper]

Ground the aircraft now for maintenance before someone gets hurt or killed.

See this aaib report (http://www.aaib.gov.uk/cms_resources.cfm?file=/Robinson%20R22%20Beta,%20G-BZYE%2002-09.pdf) if you need to know why. Relevant extracts below

After takeoff, during the transition from the hover into forward flight, the engine power varied intermittently and the pilot had difficulty in controlling the helicopter, which was damaged in the subsequent landing. It transpired that the engine had exceeded its rated speed on the previous day but the maintenance organisation had not been informed and the relevant inspection did not take place.

An inspection of the engine found that the plastic gear for the left engine magneto was broken, which could account for the rough running engine and the fluctuating manifold pressure. The maintenance organisation had previous experience of this failure,which was normally associated with an engine overspeed or an inadvertent ‘dead cut’, where both magnetos are turned off whilst the engine is still running. The engineers also found evidence that the engine cooling fan had moved on its shaft, which they also considered to be consistent with an overspeed event. As a result of these findings the engine was sent to an approved Lycoming engine maintenance facility for an overspeed inspection. Clear evidence was found of an engine overspeed, with all cylinders having excessively worn valve guides and stepped valve springs.

[ShyTorque]

Any exceedance of engine, transmission, or rotor limits on a helicopter needs looking at by someone suitably qualified to assess if any damage has been caused.

Not just by a 300 hour instructor who will be worried about his job.

[VeeAny]

If it went there it is definitely a maintenance action.

There is no question you must report this if your instructor does not do so, it should however not be your responsibility to do so, if he does do so find another instructor.

[OvertHawk]

1) Make sure it is reported.
2) Do not fly in the machine until you have verified that the maintenance organisation has been informed and have checked and released the machine.
3) Advise your fellow students not to either
4) Do not fly with this instructor again - There are questions to be asked about what he allowed to happen and there are even bigger questions to be asked about him not then reporting it
5) If you are not 110% happy with the way the school deals with this then find another one.

Have you talked this over with your regular instructor?

This is something not to be messed with - seriously!!

Good luck with the rest of your training - this was not your fault!
OH

[OvertHawk]

ifresh - check your PM's
OH

[Cows getting bigger]

Engineer, probably via the chief instructor's office. Red line is red line.

[S76Heavy]

Yup, it's a red line.
If the manufactirer would have thought it was ok, he would not have given you those limits (red lines) to stay away from.

So, while I appreciate your insecurity (and it should not be your call as the student), you've been in test pilot territory.
Not your call to decide what needs to happen, that is up to an engineer/mechanic.

Well done for asking the question and not hiding behind that instructor. You show character and moral courage wich will serve you well.

[Runway101]

Ground the ship and have maintenance look at it.

At my flight school we had overspeed issues frequently (big school). At all times the helicopters were grounded and went to maintenance for a few days. Sometimes embarrassing for the instructors, especially since it was always the same guys. It is possible that not these instructors were not good keeping the RPM in check, but maybe they were just the ones mature enough to report it.

[lelebebbel]

.... and never think for one second that this was even partially your fault. It was not, and you will not be blamed for it at all.

One of the things that gets drummed into you when doing an instructor course is that the instructor has to guard the throttle and the collective. Especially when the student is manipulating either one.

The other thing that they drum into your head is that the instructor has to report overspeeds. It is a common thing to happen, especially to new-ish instructors who haven't been burned yet...
Any employer worth working for will not fire the instructor for overspeeding it (unless he did it on purpose), but they will fire him/her for trying to hide it.

Maybe you should give him a chance to own up on it and save his career, but do it NOW before someone else flies the thing.

By the way, above 110% RRPM/ERPM, there is also a high risk that the blade spindle bearings might be damaged. This can in theory lead to a catastrophic loss of control in flight.
If the RRPM where off the chart as indicated in your picture, the blades are done and need to be replaced. Robinson has a detailed list of maintenance actions in case of Rotor and Engine overspeeds, maybe someone can post it here.

[ifresh21]

Thanks a ton for all the great responses. I now see that this was extremely serious and maintenance action must be taken. I will refuse to fly until maintenance is performed. Would it be too much to at some point ask to speak directly to a maintenance person responsible for the helicopter? I think I would like to hear directly from maintenance as the final step before I fly this helicopter again.

I called the school and the person who answered said that it is the instructor's responsibility to report it. I told them I want to talk to the owner/chief instructor/maintenance/etc directly with the full story. Ultimately we agreed that they will call me back.

"lelebebbel" made a good point - should I get the instructor's number directly and talk to him so that he has the opportunity to report it. It has been going through my mind that while safety is number #1, I would hate to see a new instructor go because he made a mistake(surprising a non-primary student at 250 agl on final)... Telling him what I am going to do would probably be the right thing. It is highly likely that he had no intention to report it on his own, when I called, the person I spoke to(spoke to at night the day after the day of the overspeed) happened to be one of the main instructors at the school. He said he heard nothing of an overspeed. I believe he actually flew the incident helicopter right after me and the incident instructor had contact with him (they spoke to eachother).

I will do my best to get this worked out quick - I won't be flying for about a week, but I am concerned for the others who will unknowingly be flying this R22.

So next step - get the incident instructor's number and let him know my plans and my concern for his job? Give him a day to report it. Call the school the day after and find out whats up. Monitor maintenance progression. Talk to maintenance people before I fly?

Good plan?


Thank you again to everybody. You guys are extremely helpful.

P.S. - Is there a way to view the R22 maintenance manual online at no charge?

[paco]

"it is the instructor's responsibility to report it."

I would ignore that. He should have spoken up within 5 minutes of ending the flight. Talk to an engineer (they don't bite!) and if the CFI is not interested get another school after a phone call to the CAA.

phil

[herman the crab]

Firstly, I think Ifresh21 is in the USA.

Its getting late and I have partaken of the falling down juice and may have missed something but did the CFI roll the throttle off? Was the governor turned off?

As said above - do you best (even though not your responsibility) to get this machine grounded until the required maintenance has been done.

The CFI's job is less important than the lives of others who might flight it.

HTC

[Vertical Freedom]

OK glad to hear that you are concerned about the potential consequences.

1. Yes the machine needs to be inspected as all the Pilots here have correctly alluded to. Dont be shy of Engineers they are there to keep you alive & the machine making money. So build rapport with them.

2. machine is grounded, so DON'T fly till engineer clears the machine.

3. there should not be any delay in reporting this exceedance to the CFI, AME etc. Don't wait a day or 2, it should have been done same day. Even if it was the last flight of the day & everyone had gone home that Instructor should have called his CFI? If not get another Instructor.

4. Avoiding ANR? My friend that is rubbish. Apart from the fact that ANR will save your hearing so that at age 70 you'll still hear your wife nagging you. More importantly you will hear more things going on with both engine & all rotating bits. ie; few years ago I heard of a CPL doing a check ride wearing ANR, the old timer & superbly qualified senior Instructor scalding him over ANR when the CPL said, 'can you hear that strange graunching noise? The old Instructor said 'NO' everything sounds fine? But he proceeded to do an precautionary landing against advice of the Instructor only to discover that the hydraulic pump was destroying itself on a AS350 dumping hydraulic oil overboard & they were seconds away from losing all hydraulics, but saved by the refined sound inputs heard through the ANR there was no dramas.

ANR will help you greatly hear odd things that should not be there. As for not hearing the engine, that's crap, when you lose the engine the massive yaw will let you know when power is gone before the noise stops (engine failure). So get ANR & save your hearing & be able to hear all the noises, both good & bad. Also reduces fatigue hence you stay sharper longer :cool::ok:VF

[Dick Sanford]

Please note that you Open the throttle before you lower the lever to recover RPM.

[Runway101]

Would it be too much to at some point ask to speak directly to a maintenance person responsible for the helicopter?

Depends which school and where they do the maintenance. I walked into the maintenance department at my flight school a couple of times to speak to them. Once I was in doubt about too much play on the tail rotor bearing, and they pulled out the maintenance manual and showed me the tool to test it with, letting me know they just checked it on that particular machine and it's alright. Once I also found a crack near the oil cooler shroud during the preflight check and they came out with mirrors to see more details and grounded the machine.

Is there a way to view the R22 maintenance manual online at no charge?

No, but it can be ordered from RHC's web site using your credit card, or have a look at it when you speak to the maintenance guys they have it of course. I picked up my MM for the R22 and R44 during the safety course a few years back.

[S76Heavy]

During my pilot training I was in the maintenance shed for hours every week, trying to get a more comprehensive knowledge about the machines I was flying and trying to master. So I would seriously recommend it to you as well.

Besides, it never hurts to hear the point of view from the guys and gals that keep us flying.

As for giving the CFI a fair chance to own up: I agree it is well past that point.
If, as someone has mentioned, the blade spindles have taken a beating (I don't know the R22 but know this problem from other helicopters), it has become a flying deathtrap. No room for egos, do the right thing. NOW.

Furthermore, talk to your regular instructor about this. Get a feel for the safety culture there. Because, if many exceedences go unreported in that flying school, someone will come to grief. Make sure it won't be you.

[reversethrottle]

Sorry Mr Sanford - From the mouth of Frank Robinson himself...in the R22 you MUST roll on throttle and reduce collective SIMULTANEOUSLY to recover from low RRPM.

Great to see a student being proactive.

[Peter-RB]

Ifresh,

The R22 must have a good engineer check all the delicate bits,

a well known operator up here in the north did the same with one of their R22s when a young and inexperienced FI allowed a stude to Auto to the ground, only trouble was said FI didnt watch over things and resultant O/Speed streched a few serious things, I was the next SFH to go up in that A/c, it was almost my last every flight anywhere, for once airborne the thing went totally u/s and would only turn right, and was shaking itself to pieces, with the help of the ATC and my huge upperbody strength I got down, determinded to pull someones nuts through their mouth , but seems every body bailed whilst I was doing a Mad Mitch in the office.

Sad to see this is still happening. all pilots should Fess up and be a man if they fark up, :=

PeterR-B

[cl12pv2s]

A similar thing happend to me - But I was the instructor.

I took on a student from another school for his commercial course. The low RPM horn came on (I think in a RPM recovery drill.) Super fast panick action by my student, a strong throttle hand, a really aggressive flare and the collective dumped to the bottom...Whizzz! That RPM flew up before I could stop it. Redline - Yes. How long - Not sure, but 1-3 seconds.

So what did I do?

I landed back straight away. Told the student it was not his fault - "These things happen". Went straight to the maintenance board and grounded the aircraft. Went straight to the hanger and explained what I saw. Went straight to the boss and explained what happened.

The result...

The aircraft was grounded for 3 weeks while they sent a part away to be inspected. It came back with no damage reported. Maintenance guys, found no evidence of rotor overspeed. The boss thanked me for the honesty. The boss had a 'no-blame' culture in order to encourage this kind of honesty.

The student and I discussed the event and I flew with this student the next day in another aircraft, me, a better instructor more vigilent for such an event in the future and the student less panicky and more controlled when the horn comes on.

(From an instruction point of view, what did I learn? I learnt to treat every student I have not flown with as a new pilot.)

-------------------------------------

As an instructor and PIC the responsibilty was all mine. However, more importantly, I have a responsibility to every pilot who would fly that aircraft afterwards. If I had not reported this, and someone had flown that aircraft 3 days / weeks / months / years later, and had a fatal accident, it would be on my concience forever, whether or not their accident was attributed to my earlier overspeed or not.

To the original poster - Set your personal standards for the rest of your career right now.

There are ways to handle the situation with the instructor. You need to find a fair way. The bottom line is though is that the aircraft gets inspected.

Good luck.

cl12pv2s

[peely]

I had a similar situation with a 30 hour student I took on from another school. I was not in the helicopter as the exercise was a solo one practising basic skills a few miles form the airfield.

Previous school instructors always turned the gov off on the ground and when I was not in the helicopter the student had reverted to type and turned it off whilst running up. You all know where this is going - well he managed to take off with out the gov on and shortly after take off realized his mistake and flicked it on. No problem he thought and off he went - some 5 minutes later he realized the engine and rotor needle was no where to be seen and after doing some trouble shooting he slowly retarded the throttle and then all of a sudden the gov pulled the RPM back to the normal green range. Student believing all was now ok, continued the exercise for a further 35 minutes before returning to the airfield.

Thankfully I have a no blame culture and open approach to all mistakes so he fully explained what happened. Whilst there are many lessons to be learn't here the I grounded the helicopter immediately and had it check - 3 weeks later and $36000 out of my pocket (I also own the heli) found very little wrong and is a testament to how these little machines are made. Worst thing was the helicopter was brand new and had 98 hours on the clock at the time of overspeed.

Lessons learn't - gov stops governing at 116%, never assume that just because a student has over 30 hours with another school that he know the very basics of pre-lift and post lift checks, always brief on the what to do if any unusual situation occurs durning any part of the solo exercise (done before every solo flight until they are responsible for themselves.

Thankfully, no one hurt and a very valuable lesson - student now has 500 hours and owns his own Jet Ranger which we also use for some commercial work.

[topendtorque]

For those who are wishing to learn from these threads it may be a good idea to relate a bit about the whirlmode RPM as well. I don't have the book in front of me so rather than guess maybe someone else who has can look it up.
For the newbies, the onset of whirlmode is very sudden and is where the T/R drive shaft goes out of whack so far that it self destructs, taking half the tail boom with it. It probably is a sort of eye watering, ear wax popping excitement experience, followed by a quick stop from the vertical terminal descent speed approach profile. Your arrival airspeed of course will depend upon the height of entry, but any higher than ten feet is most likely academic

At every hundred hourly inspection, the run out limits on the T/R drive shaft are checked to ensure someone hasn't been doing something that they should have spoken about.

Now tell me, are you still dithering about marching right into the CFI right now, and talking it over.

yessir, the red line is there to be not abused and if done so accidentally, please make a breast of it.
all the best tet

[lelebebbel]

For those who are wishing to learn from these threads it may be a good idea to relate a bit about the whirlmode RPM as well.


60% and 132% RRPM are the relevant numbers in the R22 according to RHC. (The first number is, of course, far less dangerous, although this is the reason for the yellow arc on the tachs).

There are cases where the entire tailboom separated during a severe overspeed.

[chopperchappie]

Is it not common practice for the instructor and the student to discuss the flight either beforehand or at the start of the flight what exercises are to be covered and what if any emergency drills (may) be carried out.
This would seem particularly important if it's not your regular student/instructor relationship.

Yes I get that once you have your license you need to be able to identify problems quickly and go into auto on your own (and quickly in a 22) but it does seem form the initial account that some of the panic (probably the wrong word but you get the idea) was caused by the student's lack of expectation of needing to do an auto or low rotor RPM recovery.

For my non-instructor two-pennyworth initiating an auto/low rotor RPM recovery at 300ft with someone you haven't flown with much does seem to be getting a bit close to the line. Was it also over a built up area? :)

IFRESH21 - Interested to know if that conversation did take place beforehand ??

CC

[MLH]

I don't have the maintenance manual handy but, I believe an overspeed like that requires that the magnetos be inspected.

[VeeAny]

It requires a lot more than magnetos !

[TwinHueyMan]

Having seen first hand a set of spindles from an oversped 44, I would not hesitate reporting an O/S. Very dangerous situation that can hide for a long time after the event with no apparent symptoms.

I bent wrenches for 10 years in the Military before starting to bend helicopters, a world very critical on mistakes, and spent many a late night doing inspections and troubleshooting trivial issues to avoid a pilot having to get in hot water for admitting they exceeded the rather conservative 30deg/sec yaw limit or being called a complainer because they didn't like how the flight controls felt during a travel check. A good mechanic can find out if you have broken something very quickly, and the aircraft will be sorted accordingly, without having to put your neck out for what is right. Good rapport with your mechanic is worth its weight in gold, and all it will cost you is a case of beer. Yeungling is preferable.

Mike

[Dick Sanford]

Dear Sir. (reversethrottle) I have had many many, many chats with Frank reference this subject.
Please refere to R22 POH page 3-10

[anti-talk]

I do believe I may have been that very student, much water has passed under the bridge since then ;)

Even now as an R22 Instructor with many thousands of teaching hours I recount that story to all of my new instructors for 3 reasons;

1) Beware of students you havent trained yourself, they will do things you dont expect when you least expect it.

2) Do the right thing!! If you screw up, someones life can depend upon your integrity as a Flight Instructor. My Instructor's professionalism and subsequent actions / reaction (both to me and the company) to that incident were formative in my flying career.

3)Always fully brief a student prior to flight about low RPM recovery and autoration power recoveries so you are both on the same page and one of you isnt winding on the throttle whilst the other is pulling an armpit full of collective - sure fire power on overspeed. It is the instructor's job to prevent this happening NOT the student.

Geoff

[reversethrottle]

Mr Sanford - I thank you for your comment and whilst I don't doubt that you may have had many discussions with Mr Robinson regarding low RRPM recovery I wasn't quoting the R22 manual but rather the R22 Safety Awareness video in which he specifically states the actions must be simultaneous. If you would like me to quote the manual then I in turn refer you to Safety Notice SN-10 which says, in part:

"No matter what causes the low rotor RPM, the pilot must first roll on
throttle and lower the collective simultaneously to recover RPM before
investigating the problem. It must be a conditioned reflex."

Rgds.

[Dick Sanford]

Last comment ref Low RPM recovery in a Robinson helicopter (R22 & R44)
Why do you need to add throttle before lowering the lever?
You can lead a horse to water but you cannot make it drink. Having conducted the European R22/R44 safety course for 15 + years, perhaps i'm wrong.

[ifresh21]

So I called the school like the day after the "well call you back" call. I talked to my real instructor who is beast and most experienced at the school. He was like I heard you had an overspeed? He is like ok well we grounded the aircraft. He sounded like he knew his shiz he was talking about removing the rotors and checking spindles and stuff.

He didn't even ask what happened - he said wed talk about that later after he talked to instructor... I was away without cell service so i haven't talked to him since. Im hoping they did a full maintenance and everything. I will talk to him today - any questions I should ask?(about the maintenance etc.) Hopefully the instructor explained that it was an engine overspeed also. That does require additional maintenance, right?

Thank you again everyone - I will keep you guys updated


choppperchappie: It wasn't panic at all, I was calm the whole time. I just did what the book says - that is all. I didn't do it perfectly either - there was a big pause. If it was real I prly would have stalled it lol. Thank god he was smart enough not to do a throttle chop.

We were on final parrallel to a runway over grass.

We talked about the flight generally before hand. He was good to take the time to do that. But in no way shape or form did he mention a low rpm warning test lol. We also did 180 autos for my first time and we didn't discuss those before though. So yea we talked but he missed a few things :)

[Nubian]

Being 16 years doing both fixed and rotorwing license at the same time,(impressive) I would recon you must be a smart fellow, therefore I think you should know what to ask your instructor about next you see him.

Your last post reminded me of ''Little Britain'' by the way

[Dantruck]

Dick / reversethrottle

You roll on throttle BEFORE lowering collective because...lowering the lever naturally closes the throttle via the corrollator, ie: the lever and throttle are connected.

Simultaneously lowering and rolling raises the possibility that your amount of throttle rolling will be at least partially cancelled out by your amount of lever lowering, ie: the former will trail the latter.

Thus, to be sure, it is better to at least get the engine power recovery process started by first rolling on throttle that little bit BEFORE. Of course, getting the lever down is also very important, hence the 's' word tends to get used. We are talking milliseconds, here.

Bring back the old days, eh Dick?

[ifresh21]

Isn't it more important to worry about lowering the collective? Cause what if there is engine trouble anyway - full throttle might not do much for you.

I think it should be simultaneous - any hesitation waiting for the throttle to go full could be deadly. I did it and its not that hard to go full throttle while lowering the collective ;) . lol.

You guys know wayy more than me probably though(besides maybe actually doing it), so thats just what it seems to be from my pov.

[Cows getting bigger]

Now i'm not a very sharp helicopter pilot but I'm pretty sure that I can roll and lower at the same time.

Good question about the cause of RRPM decay; not something I'm personally diagnosing when the buzzer kicks in. :)

[ifresh21]

Good post cows

[ifresh21]

So I finally got in touch today. The aircraft was inspected and nothing was wrong. I asked they said it was grounded a few days.

So everything is good to go I guess. He said I can talk direct to the maintenance guy when I come in- that is something I would like to do. It also interests me just so see like a disassembled R22 and how they do things if they let me do that. Maybe I can get some preflight advice and stuff.

Thank you to everyone for all the help and stuff. You guys are beast.

[nightsta1ker]

Oversped an R22 engine yesterday on strartup. I could have sworn the throttle was in the detent, but I don't see how an overspeed would be possible like that on startup without the throttle butterfly open. I must have not had it closed all the way. In any case it was reported immediately and the engine is being pulled for inspection.

Any idea how much this costs to inspect for an engine overspeed? I am feeling really guilty about it and want to help pay for the inspection, but I need to have an idea of cost. Anyone have any insight?

[Sir HC]

If the engine has to be removed, with parts and labour, you're up for at least $15,000 to pull, bulk strip, inspect, reassemble and refit.

As for repayment, these things happen, the school will understand this. Just continue to do your license with them and whatever you do, don't go next door to the competition.

[The Night Owl]

Good call Sir HC, stick with them.

This is what they pay astronomical insurance rates for, it shouldn't cost them too much.

This happens all the time, nice bit of cash flow for the local MO's and more importantly the manufacturer who could so easily fix this defect in their product but choose not to....I wonder why:suspect:

[valais]

Is there a way to view the R22 maintenance manual online at no charge?


Yes. Here you go: Robinson Helicopter Co. (http://www.robinsonheli.com/r22_mm.html)

[Peter-RB]

Ifresh,

Well done for reporting it, I once SFH a R22 that had been used to demo Autos to power recovery , only the rotor went wild and oversped nearly everything it could, the young new FI didnt write it up and I was allocated that R22.. 2 hours later, I covered it well about eight years ago on Rotorheads, but the effects were frightening , No left turn ability my sixteen stone(then) weight could not control the stick and I was unable to land immediate due houses and buildings, wont bore you with the details but I have never flown any Robinson products since, I lost my trust in their ability!

Peter RB
Lancashire

[cockney steve]

For very little additional manufacturing costs, the relevant gauges could be made to incorporate a second, "marker" needle.
In operation,the main needle pushes the marker with it,leaving the marker behind when it falls back.....without an external reset-knob, a clear , "at -a- glance" record is there, of the highest reading given by that instrument.

Same system can be incorporated in the software of "glass" instrumentation.

I think it shows low moral integrity on the part of airframe-manufacturers ,that such fundamental safety-features are omitted.

legislation alone, will not deter the immoral, amoral or dishonest from walking away from a potential deathtrap, or selling it on.

[cattletruck]

The little red mark in the OP's pic is not in the red so there's nothing to worry about :E:} - if the needle can actually go that far off the scale it makes you think was Frank saving weight by reducing the red paint for the overspeed band?

As a very low solo hour pre-govenor R22 stude coming from a H300, I did overspeed the engine once. During the take-off phase I put the engine needle at the top of the green arc when light on the skids. As I lifted off the correlator pushed the engine needle one third into the red arc, I overreacted with the throttle correction and found myself doing a soft auto into the ground. I shut down and reported the incident. I think both instructor and owner were laughing when I told them how far and how long, but hey I was still very wet behind the ears. I got back in the machine and this time paid more attention to the very narrow power band of the R22 unlike the 300.

[Reely340]

regarding throttle control, governor:

Due to being rather fat, training in an R22 was never an option for me. So when my buddy and I signed up with the other school near by, I asked if their 300Cs were equipped with governors, "like them nice R22s".
Owner, master FI, head of you name it, looked at me sporting a very evil grin and said "nope. And if they did, I'd take them out myself, as I'll make sure, you guys will learn to control that bugger manually". :=

Turns out that 300C correlator mechanism only does a mediocre job, and "watch your rpms", "check engine speed", "no, we don't take of doing 2900" were among the most common lines of communication, rounded off by the headmaster's claim he won't need that fancy rpm meter at all as he can tell the engine speed by ear.

Now both me and my buddy are used to keeping the rpms not only in the green but inside specific parts of the green arc at will.

What astonishes me is that initially we'd quite frequently accidentally fly
with 100 rpms past redline for a couple of secs and no one would care, ground it or tear it down. And to me that very FTO is quite meticulous in regard to maintaining their source of revenue.

So why is passing red line in an R22 such an issue?
Is the 320 so much more overrevv sensitive than the 360?

[FSXPilot]

I'm not sure if they are that sensitive but when I've dealt with an oversped R44 and sent the engine away for repair there was obvious signs of damage due to the overspeed. Helicopter engines are never meant to be oversped at all. Lycoming is very clear on that in there maintenance data.

[firebird_uk]

The manufacturers will (obviously) define the tolerances for their engines - but it seems strange to me that in the 22 & 44 you operate an engine within a few percent of it lunching itself and needing a complete examination.

Now an open throttle start from cold I can see causing a lot of potential damage, but a 6% overspeed on an auto re-join?

Given these engines are chosen for their reliability, are then de-rated but (apparently) run within a few percent of imminent destruction seems a bit strange.

But what would I know. I only allowed to change the oil with written instructions...

[lelebebbel]

I'm not sure if they are that sensitive but when I've dealt with an oversped R44 and sent the engine away for repair there was obvious signs of damage due to the overspeed. Helicopter engines are never meant to be oversped at all. Lycoming is very clear on that in there maintenance data.

In my limited experience, the R22 is less likely to receive engine damage in an overspeed, but the spindle bearings on the blades are easily damaged.

On the R44, it's the other way around. The spindle bearings must be stronger, but that 540 engine does not like overspeeds at all.

[Reely340]

Personally I'm right on firebird_uk's side on that topic. But if overspeed is that big a safety issue, especially when not properly logged and treated, why not prevent it by shorting the ignition at 105% rpm?

Every modern offroad racing motorcycle has that, the YZ400 kills ignition at 11.000rpm my wr450 at 10.400 rpms. You can fall off the bike in the woods and rest assured that the stuck throttle won't ruin your engine, BTDT. Going WFO in 3rd will feel as if one hits a wall when the limit is reached. It would be an addon feature, electronically shorting the ignition, kind of "parallel to the main ign switch".

The S-300Cs offers an option to cut ignition at ">1700 + clutch_open" (I bet every FTO has that option in place, it drastically reduces engine-to-pulley shaft repairs :E ) why not add another limit at ~3300?

The thing I don't understand about Frank and his machines is why he skipped some very simple ways to make his machines as bulletproof as the old 300C:
1 decent inertia rotor
2 fuel injection (how about IO-320-B1A? :cool:)
3 rev limiters
4 bladder tanks

Mind you, 2) is the very reason, that the Cabri is not very attractive in my eyes, in 21st century there ought be no place for carburetors in aircrafts, at least in new designs.


yust my 2cts

[FSXPilot]

http://www.lycoming.com/Portals/0/techpublications/servicebulletins/SB%20369C%20%2804-18-2012%29/Engine%20Inspection%20after%20Overspeed.pdf



Lycoming are very clear in this service bulletin and it is highlighted.
"However, for rotary wing aircraft (helicopters), no momentary overspeed is
allowed and inspection and maintenance must be done as per this Service Bulletin."

Unlike planes helicopters do not have a fly wheel so any overspeed can lead to sharp torque increases that would be damped out by a propeller.

[ShyTorque]

Unlike planes helicopters do not have a fly wheel so any overspeed can lead to sharp torque increases that would be damped out by a propeller.

I don't follow that. Helicopters have a very large propellor on top.

I'd have thought that over-speeding the engine would not cause a sharp increase in torque, rather the opposite (Power = Torque x RPM).

The service bulletin refers to the likelihood of broken piston rings and/or valve gear, caused by the the rotational speed and loss of control of inertial forces, rather than an over-torque.

The small rpm margin allowed (none for helicopters!) does suggest that the engine is working at the limit of reliability at the best of times.

[500e]

Reliability \ Helicopter :confused: into the realms of fantasy now ST

[ShyTorque]

That's why I fly turbines - and two at once if three aren't available. ;)

[FSXPilot]

The main rotor blades in nearly every small helicopter are belt driven and there is no direct coupling to the engine and the blades do not act as a fly wheel would or as in fact a propeller that is directly coupled does.
I think one of the air safety magazines caused a bit of a stir last year when they suggested you could check which mag was not working whilst flying by switching to right and then left. If you do this in a small piston engines helicopter with one mag working there is a very good chance the engine will just cut out. In a plane that would be unlikely as the propeller would keep it turning. Feel free to try it out.

[ShyTorque]

FSX, I'm well aware of the differences between fixed wing and rotary wing power plants and transmission systems. I stick by what I wrote. In the case of a piston engine overspeed, it's not excessive torque that would cause the damage to the engine itself. The service bulletin backs this up. Valve gear and piston rings do not get broken by over-torqueing, but by over-speeding. Balance shaft bushes are damaged by excessive inertial forces, not by torque.

If an over-torque occurred, it would result in a transmission or main rotor inspection, and that isn't the problem here.

As far as switching off the good mag of a helicopter piston engine in the case of the other being possibly faulty, no thankyou. I'm not in the habit of trying stuff likely to kill me, especially as this means the left hand was away from the collective to operate the magneto switch. I read that bulletin, too, btw. The difference is that a helicopter transmission has an over-run clutch / freewheel device and of course an aeroplane engine has the prop bolted directly on the crank (at least in most cases, there are some exceptions which are geared/belt driven). Yes, switching off the ignition would probably result in a sudden engine stoppage because nothing external would be driving the crankshaft round.

But that problem is about as far from an engine over-speed as one could get so I don't see the relevance... :confused: