R-22 massive overspeed

[Mikemv]

 

Again keep in mind we're talking about something that happened in just a couple of seconds. It was over before I had time to finish saying, "What the Fu...!"

 

In retrospect (this did happen a couple of years ago) my hand may have been pulling up the carb heat when it started?...don't remember everything exactly? So that would answer any governor overpowering hand idea? Perhaps I could blame this on the "card-heat assist" which lowers the the heat (often into the yellow) when you pull into a hover, causing the pilot to re-set it once in a hover? In other words if this had been a Beta (no carb-heat assist) my hand definitely would have been on the throttle to catch the surge before the rpm went too high?

 

The ship didn't balloon up, it just started to rise, so when I chopped it I wasn't really that high. (yeah, they don't like us hovering very high in these things to begin with, if you're at 5 feet an instructor will generally tell you to go lower!) So a normal hover is around 2 feet.

 

As for the needles, the only thing I can be 100% sure of is that they both looked like they went way up and the swords were no longer crossed. If I had more than a couple of seconds to stare at the gage perhaps I could be more precise? When I told the owner he said it just may have looked that way because of my perspective (looking down at the gage, since its below eye level) and that they possibly didn't go as high as I thought? I think we settled on 130% for the overspeed estimation,...if I remember correctly?

 

The throttle is still covered with that cushy foam crap, and as someone who has flown helicopters without a governor and/or correlator, yes the robbie throttle does suck in comparison when the governor is off!

 

I wish I had more to add, but it just happened way too quick. However since the governor did surge again when the mechanic took it up, something must have happened? Unfortunately I never found out what!

 

Power on over speed to estimated 130% and the mechanic took it up again????????????????

 

What does the MM say for both the Airframe and Engine tell us to address/do? This was previously answered and that helo should not have flown again without a lot of work to rotor system and engine.

 

Maybe it flew after the required maintenance was performed? If not, what kind of mechanic/pilot would not refer to the MM and strap himself into it and fly it?

 

Crazy, just crazy!

 

P47, not intended to question you, but the process in general.

Edited January 15, 2014 by Mikemv

[aeroscout]

All good info, pilot, thank you!

 

What this demonstrates is that bad sh*t happens FAST in a helicopter. You might think that two seconds is an awful lot of time...but it's not. And...Murphy's Law being what it is, that sh*t will happen when you have your hands off the controls (tuning a radio or some such) or are otherwise concentrating on something else.

 

The takeaway for me is to understand that such governor failure modes are possible, and to be on the lookout for them.

Aka bolo.

[pilot#476398]

 

Power on over speed to estimated 130% and the mechanic took it up again????????????????

 

What does the MM say for both the Airframe and Engine tell us to address/do? This was previously answered and that helo should not have flown again without a lot of work to rotor system and engine.

 

Maybe it flew after the required maintenance was performed? If not, what kind of mechanic/pilot would not refer to the MM and strap himself into it and fly it?

 

Crazy, just crazy!

 

P47, not intended to question you, but the process in general.

 

I don't know what the mechanic did first, but when he did take it up, it was my understanding that he just hovered it.

 

I suspect they had to find out if there actually was something wrong with the governor, or if I had just forgotten to turn it on?,...'cause you know, when you have an overspeed by yourself, no one on the planet (including your dog) will believe you when you say, "Yes the governor was on!"

[troll.detector]

 

When I looked down the needles were split...

Not being funny, but do you mean the engine tach raced up and split above the rotor? I thought mechanically that was impossible?

[troll.detector]

Not being funny, but do you mean the engine tach raced up and split above the rotor? I thought mechanically that was impossible?

Disregard- just seen the question already asked.

 

And yes things do move fast in an R22- there is no turbine lag it is a low inertia rotor, so I do believe it can engine overspeed faster than most helicopters.

[troll.detector]

Also in R22 tachs, top end in 110% - you might estimate another 10% maybe, but 130% - i think you would have bent needles (it has happened - google it)

[Azhigher]

Jumping in: I had a minor gov failure in a 22 way back when. Doing slopes with gov on the engine/rotor magically jumped to ~110%. Heard it throttling up, caught it, rolled it down. Hover taxi'd back to parking with the student off the controls and it tried to jump again. I think the mechanic said it was the magnetos...

 

Happens I guess.

[Goldy]

I just wanted to jump into a few things here...

 

First, that is why you ALWAYS maintain contact between the collective/throttle and your left hand! Things can and do happen quickly and there is not time for any pilot to get their hand "into position" when flying an R22!

 

3 bad things happen with an overspeed. Overspeeding the engine with the clutch engaged usually means a rotor overspeed as well.

 

So, spindle bearings wear heavily. The blades have to be pulled and inspected per the manual, plan on replacing the bearings, especially if they are not the latest generation with the extra spindle bearing.

 

Two, the engine needs an inspection. You can probably look at the cooling fan and see that the main nut no longer lines up with the inspection paint...

 

Three- the tail rotor driveshaft can't handle high rpm loading. The mount near the tail will fracture and the driveshaft starts a wobbling....

 

High RF energy has been known to affect the governor drastically....which is why there is an SB telling you not to fly near communication sites that broadcast a lot of RF....

 

nuff said...

 

Fly safe,

 

Goldy

[aeroscout]

It sounds like you need to be fast on frequency changes in that helo.

[Nearly Retired]

Me, I'd just leave the damn thing off. Real men don't need no sissy-a** governors. Isn't that why God gave us ears?

[Mikemv]

Also in R22 tachs, top end in 110% - you might estimate another 10% maybe, but 130% - i think you would have bent needles (it has happened - google it)

Tach goes to 116% for both engine and rotor. There is no calibration above that to estimate from other that mm or inches!

[WolftalonID]

Not all of ours but most of our robbies have a favorites list of freqs preprogramned for what we use around our area. They are controlled by selectors in the cyclic. I believe only two ships have clean cyclics, and yes those require a hand off of a control to change freqs.

 

If I was busy flying, I would ask my instructor to change the freq if I couldnt and needed to. I wish the radio controls were also on the left seat, would make it nice for instructors to make faster changes.

 

Worst case, left hand cyclic, and right hand working the radio can quickly take over the center collective.

I can attest to how fast the robbies spool up..it is fast. When training for govenor failures, we turn it off and fly "old school" throttle style if you will. The correlator can be really tricky if you also attempt an auto in gov off flying. I had to do that a few times during my cfi on an advanced auto training day, and it was work! I dont think I would ever have a lower time or newer student try that without first knowing they can be smooth on the roll up first.

Edited January 15, 2014 by WolftalonID

[Mikemv]

Me, I'd just leave the damn thing off. Real men don't need no sissy-a** governors. Isn't that why God gave us ears?

 

NR, it is restricted via the POH to not fly with the gov. off other than for gov. off/failure training.

[Guest pokey]

I know nothing about Robinsons, flew one once back in 1986. I have flow the th-55's with the military installed propeller governor, leave it to the innovation of the us army. It was nothing more than a modified airplane propeller governor hooked up to a small hydraulic cylinder that upon overspeed? it "hammered" on an aluminum round block that was mounted on the fuel servo, you could feel the hammering in the throttle but it really didn't 'control' the rpm,, was just a reminder to the pilot that this hammering is soon going to get really bad and ruin your day if you don't mind your rpm. Its really to bad that in order to 'civilianize' a th-55, that had to be removed. same thing with the army chopping 2 inches off the horiz stab and installing a stall strip,, that old stab did NOT cause the nose to dive drastically when entering an auto.

Edited January 15, 2014 by pokey

[pilot#476398]

I just wanted to jump into a few things here...

 

First, that is why you ALWAYS maintain contact between the collective/throttle and your left hand! Things can and do happen quickly and there is not time for any pilot to get their hand "into position" when flying an R22!

 

 

 

To adjust the radio, gps, or even scratch an itch, you can always set it down, but...

 

In order for the carb-heat assist to work properly in flight the pilot will, more often than not, have to set it while in a hover. This has been my experience, as well as what was told to me by the guy who teaches the safety course at the Robbie factory.

 

I guess I just haven't been able to figure out yet how to set the carb-heat assist while still holding on to the throttle with my left hand?

 

Not all of ours but most of our robbies have a favorites list of freqs preprogramned for what we use around our area. They are controlled by selectors in the cyclic. I believe only two ships have clean cyclics, and yes those require a hand off of a control to change freqs.

 

If I was busy flying, I would ask my instructor to change the freq if I couldnt and needed to. I wish the radio controls were also on the left seat, would make it nice for instructors to make faster changes.

 

Worst case, left hand cyclic, and right hand working the radio can quickly take over the center collective.

I can attest to how fast the robbies spool up..it is fast. When training for govenor failures, we turn it off and fly "old school" throttle style if you will. The correlator can be really tricky if you also attempt an auto in gov off flying. I had to do that a few times during my cfi on an advanced auto training day, and it was work! I dont think I would ever have a lower time or newer student try that without first knowing they can be smooth on the roll up first.

 

Remember, not all flights in the 22 involve two people!

[iChris]

Thanks for the information guys. I don't have much to add, I wasn't there, but I do know that it was both the engine and rotor and it went real high. Above the marks on the gauge, maybe all the way up. They were basically hovering when it happened.

 

 

Jumping in: I had a minor gov failure in a 22 way back when. Doing slopes with gov on the engine/rotor magically jumped to ~110%. Heard it throttling up, caught it, rolled it down. Hover taxi'd back to parking with the student off the controls and it tried to jump again. I think the mechanic said it was the magnetos...

 

Happens I guess.

 

No doubt, occurrences of erratic governor behavior are possible and have occurred.

 

For those new to these governor/magneto issues, the governor system senses engine RPM and applies corrective mechanical inputs to the throttle, increasing and decreasing throttle to maintain rotor RPM. Nevertheless, the pilot can still override throttle inputs made by the governor.

 

The governor assembly is basically an electrical motor and worm gear assembly that drives a clutch connected to the throttle linkage.

 

An electronic control unit electrically controls the governor (that moves the throttle linkage). The main thing to remember is the control unit bases its control over the governor, and the movement of the throttle linkage, based on electrical inputs the control unit receives from a magneto, located on the right side of the engine.

 

Therefore, an erratic output signal from the magneto, results in an erratic input at the control unit, thereafter, causing an erratic command to the governor and erratic movement of the throttle linkage.

 

However, the operational drive motion of the governor works at a rate and within a range of movement that normally will not allow it to cause the so-called “massive over-speed”, if the pilot reacts timely to any over-speed or under-speed situation.

 

Remember, the collective correlator makes the coarse throttle adjustments and the governor is designed to follow-up with the minor throttle adjustments required to maintain RPM. Abrupt movements of the collective and throttle by the pilot will override the range of the governor and may appear as governor surges.

 

The instructor has to guard the throttle and the collective. Being especially careful about letting the student get too far behind the helicopter during the last 100 feet of an auto were abrupt corrective action maybe required, remember the note from the maintenance manual:

 

“The governor system is designed to assist the pilot in controlling the RPM in the normal operating range. It may not prevent over- or under-speed conditions generated by aggressive flight maneuvers.”

 

 

Edited January 15, 2014 by iChris

[aeroscout]

Me, I'd just leave the damn thing off. Real men don't need no sissy-a** governors. Isn't that why God gave us ears?

After awhile around helicopters, I forget I've got them.

[Nearly Retired]

Here's one thing I've never, ever, ever understood about Frank Robinson: I get that he didn't want to go with an old-fashioned dual tachometer display. (Well, I don't really get it - that design has worked for ever, so why change it?) Why-oh-why didn't he design a tachometer in which the "normal" rpm range occurred with the two needles pointing right at each other? Why the stupid "crossed-swords" indication? It's goofy. And why are the needles exactly the same size? Which is which?

 

I mean, with the current tach, suppose you droop the rpm a little. The swords are still crossed, but you have to look at the indicator to see how much. If the needles were "normally" both at the 90 degree position and parallel to (i.e. pointing at) each other, and the rotor needle was fatter than the engine needle, then ANY deviation would be clearly noticeable. To me, this would be a much better design. Nah, check that, to me a "standard" dual tach would be a better design, just like has been used since the VS-300.

[500F]

It took me a bit to get used to the dual tach after my first 300 hours in robinsons. It is certainly different, but it did work well.

[pilot#476398]

Here's one thing I've never, ever, ever understood about Frank Robinson: I get that he didn't want to go with an old-fashioned dual tachometer display. (Well, I don't really get it - that design has worked for ever, so why change it?)

 

So that if a Robbie pilot were to ever fly a 300 he would instinctively move the collective in the wrong direction during an auto when he sees the needle move up, making rotor stall more tantilizing!

[adam32]

Here's one thing I've never, ever, ever understood about Frank Robinson: I get that he didn't want to go with an old-fashioned dual tachometer display. (Well, I don't really get it - that design has worked for ever, so why change it?) Why-oh-why didn't he design a tachometer in which the "normal" rpm range occurred with the two needles pointing right at each other? Why the stupid "crossed-swords" indication? It's goofy. And why are the needles exactly the same size? Which is which?

 

I mean, with the current tach, suppose you droop the rpm a little. The swords are still crossed, but you have to look at the indicator to see how much. If the needles were "normally" both at the 90 degree position and parallel to (i.e. pointing at) each other, and the rotor needle was fatter than the engine needle, then ANY deviation would be clearly noticeable. To me, this would be a much better design. Nah, check that, to me a "standard" dual tach would be a better design, just like has been used since the VS-300.

 

Reason #763 not to fly Robbies.

[Nearly Retired]

Pilot476398 says:

So that if a Robbie pilot were to ever fly a 300 he would instinctively move the collective in the wrong direction during an auto when he sees the needle move up, making rotor stall more tantilizing!

 

Not sure where you're going with this. Is there some correlation between the tach needle in the R-22 and the way you're supposed to move the collective? Is that what Frank's goofy display is all about?

 

Okay, I'll bite. But...tell me, which way would you "instinctively" move the collective if you saw this presentation?

 

 

[WolftalonID]

Hmmm chase the rabbit?

[pilot#476398]

Pilot476398 says:

 

Not sure where you're going with this. Is there some correlation between the tach needle in the R-22 and the way you're supposed to move the collective? Is that what Frank's goofy display is all about?

 

Okay, I'll bite. But...tell me, which way would you "instinctively" move the collective if you saw this presentation?

 

 

 

In the 22 when the needle goes up so does the rpm. So we're taught to follow the needle with the collective in an auto. When I flew the 300 it was the opposite (when the needle moved up the rpm went down) so you have to do the opposite with the collective.

 

Doing autos in the 300 looking outside primarily, from the corner of my eye I would see the needle move up (rpm getting lower) , but I would instictively move the collective up (from years of Robbie autos) so the rpm would go down. Eventually the horn would come on, triggering another instinct to lower the collective. I went back and forth like that for many an auto in the 300 until I got used to the opposite tach.

 

The tach in the picture however would yield the same action as the 22 since the higher rpm is above the needle. With circular tachs it just depends on where the zero is and/or which side the green arc is. The needle has moved down in the picture and since the lower rpm is also down I would move the collective down (just like in the 22).

 

However one reason I am not a CFI is that I am lousy at explaining things, so if you get what I'm trying to say,...then you deserve a prize!

[Nearly Retired]

No, I get it, Pilot. I'm just always interested in the human factors of helicopter flying, and how many times the manufacturers get it wrong.

 

For instance, take the tach in the Bell 206 (and most others with similar presentations). As you say, the movement of the needles with respect to the required collective movement are not intuitive. Trouble is, helicopter dual-tachs were just modified from airplane tachs which had your typical clockwise-to-increase display.

 

I've flown with "conventional" tach displays for so long that interpreting them is automatic if not instinctive or intuitive.

 

I admire Frankie for trying something different - *and* - I admit that his way, um, works. But in the long run I think it would have been easier to just design an analog tach display like the one (from FSX) I posted above instead of trying to re-invent the wheel.