Is it possible to increase Engine RPM or rotor RPM to 100%?

[Simicro]

Hi all,

 

I have been flying the Mi-8 for 2 months now and have never encountered a situation that requires more power or speed otherwise than operating the collective to its maximum.

 

Now I am stuck at mission 17 of the campaign (click here) because the helicopter is very loaded I don't have enough power/speed to follow a formation of Mi-8.

 

So my question is: in straight flight, is it possible to increase Engine RPM or rotor RPM to 100% in order to get additional power/speeed.

 

If it is possible, how can I do? The screenshot below shows my purpose. Even if the screenshot was taken during a hover, I could not get higher RMP during straight flight.

 

Edited October 9, 2015 by Simicro

[gospadin]

do you have those 2 metal handles to the left of the pilot's seat all the way up?

[AlphaOneSix]

Faster rotor RPM won't help. The nominal rotor RPM is 95%, and the aircraft works best at that rotor RPM. when you put a lot of load on the rotor, it's fine to droop the RPM down as low as 91%.

 

Note that the only way to get faster rotor RPM is to have faster engine RPM, and your engines are designed to maintain an RPM that keeps the main rotor at around 95% RPM. So basically if your rotor RPM exceeds 95% then your engines are not going to increase power.

 

Your engine RPM is limited by the engine electronic governor. It will not let you exceed 101.15% engine RPM nor will it let you exceed 995 degrees PTIT (EGT). If you want to exceed those limits, you will need to turn off the engine governors, but your engines will fail rather quickly if you exceed the temperature or RPM thresholds.

[1.JaVA_Platypus]

In one of the campaign missions, You have to ferry an old Mi-8 to a depot for inspection and repair. Halfway through the flight, one of the engines is dying. For some weird reason, the other engine goes way over the 100% RPM if you lower the pitch of your blades. Only by raising the pitch, it lowers RPM's. It is weird and a bit difficult to decend because of that.

[Simicro]

Thank you all for your help.

 

AlphaOneSix,

 

So I understant that it is useless to try to get more than 95% rotor RPM.

 

As to the engine RPM, it is possible to reach 101.15% maybe for a short time. But does it help to go faster or climb faster?

 

gospadin,

 

No the metal handle at the left of the collective is all the way down. I will read the manual to discover what is this handle and give it a try.

 

[gospadin]

Those act as the engine governors I believe, and limit the applicable engine RPM. I always fly with them 1 notch up from the lowest position.

 

Whether that's correct or not, I am not sure. As soon as I got the Mi-8 to startup once, I stopped reading the manual =P

[Simicro]

Thanks.

 

I tried: there are 3 positions, and 1 notch up from the lowest position is the default setting.

 

2 notches up the lowest position and I can achieve 100% Engine RPM with a rotor pitch of 13 degrees!

 

I'll try that in the mission and see if that helps.

[AlphaOneSix]

Regarding the engine control levers (not governors) on the left side of the collective...

 

They are normally set in the center position. All the way down is idle, and is generally only used for testing. If one engine fails, you should pull the ECL (engine control lever) for the working engine to the full up position. Pulling up on the collective does the exact same thing as pulling up on the ECLs, it just does it for both engines simultaneously, the ECLs are used to adjust engine power separately. Pulling them all the way up won't help in this case.

 

With regard to the issue of the engine not reaching 100% RPM...

 

This is because the engine are reaching their temperature limit first, and that causes the electronic governors to limit fuel flow so that the engines cannot produce more power. Whether you hit the temperature limit or the RPM limit first depends on atmospheric factors. Typically at higher altitudes and hotter temperatures, you will hit the RPM limit first. Lower down and colder, you will likely hit the temperature limit first. The only way around that is to turn off the governors, but that would be a bad idea.

[Simicro]

Thanks AlphaOneSix for the detailed explanations. I think I got it.