Mil-8 MTV/MTV-1 info

[noooby]

Hi all,
Hopefully an easy one for you Mil-8 drivers out there. I need the Rotor RPM at 100%, and, if different, in cruise flight. Thanks for your help
noooby

[jab]

Hi

192RRPM at 95% so about 200 at 100%. You normally cruise at 93 to 95%NR.

Jab

[MightyGem]

That seems rather slow?

[wlynx]

I agree with mightygem, I don't know the actuall RPM in question for Mil-8 but 192 RPM does seem rather slow, I would expect an RPM for NR to be some where in the range of 380 - 500 rpm

[mongoose237]

I would say its about right, based on nothing other than observations of tip speeds around 400-450kts

Fag packet calculations:
Mil 8 must have a rotor diameter of 70 ft (?)
So 3.14 x 70ft x 200rpm x 60 / 6080 = 430kts ish tipspeed

Any faster and you'll be having problems I'd imagine with LSS

[Geoffersincornwall]

From memory the Nr on the S61 at 100% is 203 so 200 for the Mil doesn't sound too far out.

G

:ok:

[MightyGem]

Hmmm...that's what comes of only flying aircraft with small rotor diameters I suppose.

[jab]

After 1200 hours in the Mi8 I can confirm it is 192 RRPM at 95% NR, it has a 21m rotor diameter. Yes, the S-61 is 203 RRPM at 100%NR.
Jab

[NotHomeMuch]

RRPM is 192 at 95% and why would you need 100% RRPM as that is out of limits. If you beep the engines up you could get max 97% RRPM but that would be all. Great machines but as with all gear fly it outside of the limits it will fall apart, so why even try to go there?

[noooby]

Thanks Jab and Not Home Much.
Wasn't aware that Mil-8's didn't operate at 100%. Just needed the RPM range to see if they generate the right frequency to bring on Flicker Vertigo.
Cheers

noooby

[NotHomeMuch]

As the Mil has a 5 blade rotor system and low RRPM the frequency is out of that which brings on flicker vertigo. Worst machines I know for this are the S-76 and S330J Puma.

[NickLappos]

Russian gage marking norms rate the RPMR at 100% for the max autorotation condition, and cruise at the lower number, like 93% ish.

The tip speed of the Mi-8/17 is 700 feet per second at 95% rotor speed, quite normal.
The S-61 is 660 FPS at 100% (but is often flown at 103% for 680 FPS)

Most helos are between 675 FPS and 760 FPS, depending on how fast their cruise speed is. The higher speed helos (more modern) have the faster tips (to prevent stall).

[Te_Kahu]

Pray tell why you such a query?

[bayou06]

I flew my first 1.0 in an Mi-8 this week. Interesting flight. I found I had to put a lot of right pedal in at hover, I mean a lot of leg just to maintain heading at hover. We only had a 10 kt quartering headwind. What was your overall experience with the Mi-8. Thanks.:)

[noooby]

Te_Kahu, part of Uni Studies. Looking at Mil crash at Hokitika years back. Part of assignment is to look for two other plausible explanations.

NotHomeMuch, the actual frequency of the Mil-8 works out at 16Hz, which is in the range where flicker vertigo is extremely likely (16-20Hz). So it is quite possible on the Mil-8.

[NotHomeMuch]

OK, noooby, stand corrected. However, have some time on these machines and have never had even a hint of the dreaded flicker vertigo coming on. As I said earlier though, the S76 and S330 Puma were the ones that had the worst RRPM that brought on vertigo.