Autorotation in the Mi-8

I was trying to learn autorotation for the Mi-8 but I did not find a good video that explained how to do it. There were some good ones for the Huey who told what instruments to check and all that. However, for the Mi-8...no idea.

So I don't know how to handle the collective and all that. What I noticed is that the Mi-8 start to swing forward and backward when the engine fails and it seems very difficult to get it under control.

Maybe somebody can give me the needed hints to start practicing it?

My understanding...

Initially practise AR's from trimmed stable flight at around 150 KPH and a decent high altitude..

Either reduce throttle to ground idle or cut the fuel :) - your choice as long as you are not paying for the aircrafts...

Using cylic and pedals keep the aircraft in trim...

The main rotor rpm should not be allowed to fall below 80% at any time during the descent, nor rise above 100%.

Optimally, the main rotor RPM should be kept between 93 and 95%, as this gives some cushion to prevent over speeding the rotor, while also providing a lot of potential energy in the rotor system when it comes time to land.

Best speed for lowest sink rate is around 110-115kph, depending on the weight of the aircraft

Best speed for best glide angle is around 180-190kph, depending on the weight of the aircraft

The flight manual talks of 100-130kph as a standard number to use in auto-rotation.

For a rolling landing, at 30-40m AGL, decelerate the aircraft by adding about 15 to 20 degrees nose up pitch to arrive at around 9m to 12m AGL and 50 kph. Put the aircraft into a landing attitude, 5 to 10 degrees nose high prior to touchdown.

More details in Mi-17 ATM

Hope this helps..

not that different from doing auto in the huey. the weird pitching is your autopilot kicking off. drop collective to just above where you have control authority to keep rotor rpm up and keep control, establish forward glide speed if possible/needed, flare to slow down near ground effect and bring up collective to cushion landing.

not a by the book procedure but general autorotation rules that work in basically any heli. exact process varies by person but do what you do for the huey and should be fine

Thank you both, I'll give it a try :-)

So here's my attempt - rpm was sometimes too high. IMO it's a bit more difficult in the Mi-8 because the generator will fail if rpm goes below 80%. This is especially crucial right at the moment of power loss.

Furthermore, I did not keep an eye on the speed which may have been bad. I most probably focused too much on the rpm gauge.

Anyway, here's my first successful attempt:

I probably failed 5-6 times before, mainly because I didn't make it to the airport and dropped into the water.

IMO It's more interesting during night because the generator failure will also turn off the light in the cockpit. So you also notice when power is back again.

So here's my attempt - rpm was sometimes too high. IMO it's a bit more difficult in the Mi-8 because the generator will fail if rpm goes below 80%. This is especially crucial right at the moment of power loss.

Furthermore, I did not keep an eye on the speed which may have been bad. I most probably focused too much on the rpm gauge.

 

Anyway, here's my first successful attempt:

 

 

I probably failed 5-6 times before, mainly because I didn't make it to the airport and dropped into the water.

 

IMO It's more interesting during night because the generator failure will also turn off the light in the cockpit. So you also notice when power is back again.

Not bad. You're right you need to keep an eye on your speed; you touched down at over 100kph with low rotor RPM. As you noted, loading the rotor builds RPM, so flare more to slow down and keep the rotor spinning. This will leave you in a nose high attitude so you have to level off at the right moment. I've attached a track to show what I mean.

mi8.trk

Use the collective to control the RPM during the decent and in the flare. You might need to flare aggressively to make a landing zone. Thus leveling out your flare might not be the answer. Just use your collective to maintain rotor RPM.

Thank you for your replies. I'll keep on practice and I'll also have a look at the trk file :-)

In an autorotation your balancing three energy reserves rotor RPM, altitude, and airspeed. Aft cyclic will increase rotor rpm but decrease speed, forward cyclic will increase speed and decrease rotor rpm. Most helicopters have there best glide distance somewhere around knots and lowest rate of decent somewhere about 55 knots. So if you need more time to set up slow down, if you need to make it further to a good landing spot speed up a little. I wouldn't go below 60 knots though except for special circumstances because you end up short on energy in the flare. Also the more collective you have pulled in you know your rpm will be lower but it will also extend your glide. While flaring you can add a little collective to help slow your forward speed. This is more important in the real world but if your touching down on an unpaved surface you want as little forward motion as possible to prevent a skid/wheel from catching and rolling you over. Also I wouldn't worry about an over speed in the flare. The mechanic can change some bearings if it means I have more energy to do the maneuver with ;)

P.S. Just noticed Gizzy had put the Mi-8 specific airspeeds in his post. I'd do a thumbs up emjoi if I knew how.