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Ultra low RRPM

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Ultra low RRPM

Old 12th Mar 2020, 20:53
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Ultra low RRPM

Do you think the low RPM warning was a bit annoying by the end or muted?

https://www.dailymail.co.uk/news/art...29118588336668
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Old 12th Mar 2020, 22:35
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Slow news day was it?
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Old 13th Mar 2020, 07:12
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it is possible to take an R44 governor off, let the RRPM decay to about 40% and go to max manifold pressure while keeping the same RRPM, it will fly of the ground and hover (if you are not too heavy).
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Old 13th Mar 2020, 08:07
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Originally Posted by Agile View Post
it is possible to take an R44 governor off, let the RRPM decay to about 40% and go to max manifold pressure while keeping the same RRPM, it will fly of the ground and hover (if you are not too heavy).
And why on earth would you want to do that!?
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Old 13th Mar 2020, 11:12
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It would be interesting to see the coning angle and the stresses on the hinges. A fair bet that Frank would have a conniption.
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Old 13th Mar 2020, 13:17
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Originally Posted by Agile View Post
it is possible to take an R44 governor off, let the RRPM decay to about 40% and go to max manifold pressure while keeping the same RRPM, it will fly of the ground and hover (if you are not too heavy).
Next time you do that can you take a photo and share it with the class please?
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Old 13th Mar 2020, 14:19
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Hmmmmm.
I would be surprised if the TR worked at that RRPM.

BTW. Check the RFM for MIN RRPM Power On.

Underspeed probably just as bad as an overspeed.

Get back to us with the Reg No. and Serial No. of the airframe so we can get the barge poles out.

You did this “intentionally” right? And just what was the point?

Better still as it was an exceedance of the limitations let us know what the AMM has to say and if there is no procedure for inspection, send the details to the manufacturer and let us all know what they have to say!

Looks like “there is one born every day” still rings true.
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Old 13th Mar 2020, 16:11
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Urgh, how would Captain Agile know the RRPM was at 40%???
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Old 13th Mar 2020, 19:39
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Flight Loads

Originally Posted by Agile View Post
it is possible to take an R44 governor off, let the RRPM decay to about 40% and go to max manifold pressure while keeping the same RRPM, it will fly of the ground and hover (if you are not too heavy).
It is also probable that this maneuver was not part of the flight loads survey,and thus probable that the associated flight loads are unknown, but absent the centrifugal forces associated with the normal NR power on range, it is probable that they are quite high. Aside from Frank’s caniption,there is also some probability of receiving some troubling opinion from the Robinson mothership.
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Old 13th Mar 2020, 21:36
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Angry Low RRPM

Originally Posted by Agile View Post
it is possible to take an R44 governor off, let the RRPM decay to about 40% and go to max manifold pressure while keeping the same RRPM, it will fly of the ground and hover (if you are not too heavy).
With the main RRPM low both advancing and more importantly the retreating AOA will be very close to stall. When that takes place ALL control will be lost and normally not recoverable. This maybe possible to demonstrate very close to the ground and may be survivable, but above a couple of feet loss would be catastrophic. People forget that all cyclic control comes from directing the rotor thrust and with stall thrust falls rapidly and gravity wins. In addition directional control will be lost because the tail rotor power will be vastly reduced with reduced main rotor speed. The whole point of minimum rpm inflight is to retain thrust control with sufficient control response.
Flying deliberately outside that parameter is completely irresponsible and should result in forfeiture of you license.
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Old 14th Mar 2020, 06:48
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Pity Agile hasn't bothered to read Safety Notice 37 Frank has taken the bother to include at the back of the POH.
let the RRPM decay to about 40% and go to max manifold pressure while keeping the same RRPM
Ever heard of detonation Agile? That's exactly the territory in which you have the engine operating, high boost low RPM. Heaven help any pilot, or passenger, that flies in an aircraft after you've had your hands on it. I'm surprised it would fly with the engine producing so little horsepower, it's off the Lycoming manufacturers 540 chart so can't be estimated.
how would Captain Agile know the RRPM was at 40%?
Pertinent question, not familiar with Robinsons but see the tacho bottoms out at 46% in the photo I looked at.
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Old 14th Mar 2020, 07:36
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I'm not sure agile is actually a pilot, he's more likely little boy with posters on the wall and reads a lot, pity that reading doesn't seem to have led to any understanding
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Old 14th Mar 2020, 09:47
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I'd be concerned about the amount of torque being transmitted through the MGB at such low RPM and high power.
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Old 14th Mar 2020, 12:30
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Don't worry; Chopjock will be along in a minute to tell us how he does this all the time and that it's normal practise, can't damage the airframe or power train and that the rest of us know nothing.

While I await the fount of rotary knowledge I'll keep checking the news for Agile's entry into the Darwin awards.

SND
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Old 14th Mar 2020, 15:22
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Boy I really struck a nerve with all of you.

let me offer a couple of precisions to maybe calm dowm the opnion.
1/ you would NEVER do that in flight, this was done in ground effect.
3/ as an aerospace engineer and a pilot I found it quite educative that the rotor can get any working aerodynamic efficiency at that speed AND that the engine has suficient torque at that regime.
4/ I understand well the negative mechanical implicatiion on the airframe, rotor head coning, engine, transmission and the AC was never to be flown again.

I would say with the nominal envelop and the maximum envelop possibly closer to each other in robinson products I always value out of the box data. The next low RRPM mighr be unexpected, believed to be unrecoverable or needed to reach the only autorotation spot so far out of reach.

with all that said: Good pilots know and respect the nominal envelop
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Old 14th Mar 2020, 16:10
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What happened to precision #2?
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Old 14th Mar 2020, 19:04
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Originally Posted by nomorehelosforme View Post
What happened to precision #2?
Perhaps he changed his opnion (sic)

And it's great to know from an aerospace engineer and pilot that in ground effect isn't in flight!!!
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Old 14th Mar 2020, 20:52
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For Crab
And it's great to know from an aerospace engineer and pilot that in ground effect isn't in flight!!!
And that we can envelop the flight envelope with such precision and with such Agile analysis.

For Agile, not sure what version of English that you grew up with (there are many variations of the mother tongue) but usually... envelop is a verb that means to wrap up, cover, or surround completely. And a flight envelope is what we all understand it to be. I checked your posts and you consistently drop the e, which makes me wonder if that is one of those terms that has attracted the "any old spelling will do" disease in modern usage.

Which leads me to the smart alec observation (an attempt at humor) that when one drops the e one also drops ground effect. I mean, what the hell is a ffect, anyway?

Preserved for posterity:
Originally Posted by Agile View Post
Boy I really struck a nerve with all of you.

let me offer a couple of precisions to maybe calm dowm the opnion.
1/ you would NEVER do that in flight, this was done in ground effect.
3/ as an aerospace engineer and a pilot I found it quite educative that the rotor can get any working aerodynamic efficiency at that speed AND that the engine has suficient torque at that regime.
4/ I understand well the negative mechanical implicatiion on the airframe, rotor head coning, engine, transmission and the AC was never to be flown again.

I would say with the nominal envelop and the maximum envelop possibly closer to each other in robinson products I always value out of the box data. The next low RRPM mighr be unexpected, believed to be unrecoverable or needed to reach the only autorotation spot so far out of reach.

with all that said: Good pilots know and respect the nominal envelop
FWIW: were I to attempt what you suggest when I began to fly rotary wing aircraft, I am pretty sure that my instructor would have beaten me severely about my head and shoulders.

Last edited by Lonewolf_50; 14th Mar 2020 at 21:06.
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Old 14th Mar 2020, 23:50
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“3/ as an aerospace engineer “

That,and the other remarks reminded of a famous tidbit of Sikorsky historical lore, which goes as follows,with my apologies:

During the preliminary testing of the S-56,Sikorsky ran into a number of problems adopting the P&W R-2800 engnes in pods. Doing a ground run one day at the South Avenue plant an engine fire enveloped one of the pods.It was extinguished without losing the test aircraft. The Ch Pilot at the time was Dimitri ( Jimmy ) Viner, who had started out cleaning the hangar etc over in the Long Island fixed wing days. Jimmy was known for his “direct” communication. He had been running the ship when this happened. After things quieted down,Jimmy asked that the design engineer get down there ASAP and when he showed up,Jimmy said “ Son, do you have an engineering degree ? “ The engineer replied “ Yes Sir,I do.I have a BS in Mechanical Engineering from XXX University”. Jimmy said to him “Son, I advise you to get your F........g money back”. Jimmy later made the first flight on the S-56 with Jim Chudars,who was the Asst Ch.Pilot when I signed on in 1966.
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Old 15th Mar 2020, 00:24
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Thinking out loud here:
The rotor is at idle or below.
The engine starts out at idle.
Agile pulls up on lever, the correlator will try to add throttle
Must hold throttle closed against the spring to keep correlator out of it, and engine stays at idle.
Agile then pulls pitch to get off ground. Supposedly gets to the hover.
How the fork can an idling engine, with 40% rotor RPM, lift the machine off the ground? It has enough trouble doing it at 100% engine and rotor RPM.
If engine is at idle, how can he get max MAP?
If he has max MAP, then he sure isn't at idle, which is around 13" by memory.
If the engine isn't at idle, then the RRPM aren't either.
I think this whole story smells of bovine excreta.
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