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I've been trying to do autorotation as per this manual and it's simply impossible.

 

In short, the manual states that you should descend at 80-90 km/h, at 50-60 meters AGL pull up to decelerate so that at 10-15m you're at around 50-60 km/h and then pull the collective fully up to cushion the landing.

 

My problem is, I've tried all combinations: from slow flare and slow collective pull to intense flare with sharp collective pull and everything in between and my vertical speed never drops below safe values. 

 

The only way I've been able to perform a successful autorotation was when I maintained at least 150 km/h during descent and used the flare to maintain rotor rpm while pulling the collective. That way I can achieve touchdown at around 50 km/h and use cyclic and brakes to stop.

 

There's only 3 possible explanations for this: either I'm doing something wrong, or the manual is inaccurate (provided the manual is authentic this option is quite unlikely since the Mi-35P's and Mi-24P's flight characteristics should be very similar) or there is something wrong with the flight model.

 

I can try to record the track/vid next time I do this but even without it it's easily reproductible. 

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Gear down or up? I just dropped collective, nosed up a bit, then pulled up on collective about 40% very close to the ground and I landed gear UP (corrected)with only a damaged wing.

 

Gear down seemed really really dofficult to me. So since my goal is to survive I figured I’d stick with gear up for now


Edited by S. Low

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Lowering gear won't affect your chances to achieve an autorotation landing.

 

It's certainly not mentioned in the manual point 5.2.2 to enable your autorotation, rather to improve your chances of a safe landing.

We can assume that in cases of flight heights below 100 meters, lowering gear might be omitted to leave the pilot more capacity to concentrate on surviving. You wouldn't want to autorotate from 100 meters. You would have merely seconds to achieve the correct attitude and shouldn't bother with landig gear anymore.

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4 minutes ago, Rongor said:

Lowering gear won't affect your chances to achieve an autorotation landing.

That's my thoughts too.

4 minutes ago, Rongor said:

It's certainly not mentioned in the manual point 5.2.2 to enable your autorotation, rather to improve your chances of a safe landing.

We can assume that in cases of flight heights below 100 meters, lowering gear might be omitted to leave the pilot more capacity to concentrate on surviving. You wouldn't want to autorotate from 100 meters. You would have merely seconds to achieve the correct attitude and shouldn't bother with landig gear anymore.

Nevertheless it's impossible (at least to me) to follow these instructions without crashing.

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In a version of Mi35 manual I have, speed is 120-140. I have heard that rotor system is based on that from Mi28, but couldn't confirm this, but I have found several places mentioning "new" rotor system. So, not sure how much of that is applicable to DCS Mi24.

Anyway, if light, auto can be done at 120. 150 gives more margin for error. If loaded, I wouldn't go bellow 170. At 170, even full fuel, 4 rocket pods and 4 ATGM can be handled.

Keep the speed up, flare low and flare hard, push over and really pull that collective up.

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Well I can go back to practicing but my initial impressions were the gear have too much bounce to auto rotate. Every single time it’s like landing on a trampoline and then flipping over. Meanwhile gear up I can do just looking out the cockpit and not even paying attention to instruments 

Not to mention the WIP damage model seems to never give you the opportunity to autorotate

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59 minutes ago, S. Low said:

Well I can go back to practicing but my initial impressions were the gear have too much bounce to auto rotate. Every single time it’s like landing on a trampoline and then flipping over.

It's not the fault of the gear. It's only evidence that your final touchdown descend speed is too high. Just practice the final flare until it works.

 

Even when bouncing, IRL the gear is actually protecting you by absorbing energy before you end up sitting on the grass. The fuselage alone isn't that helpful to absorb the crash. When the fuselage starts to deform, chances are high you might absorb some of the energy too and end up injured or worse.

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1 hour ago, admiki said:

In a version of Mi35 manual I have, speed is 120-140. I have heard that rotor system is based on that from Mi28, but couldn't confirm this, but I have found several places mentioning "new" rotor system. So, not sure how much of that is applicable to DCS Mi24.

Anyway, if light, auto can be done at 120. 150 gives more margin for error. If loaded, I wouldn't go bellow 170. At 170, even full fuel, 4 rocket pods and 4 ATGM can be handled.

Keep the speed up, flare low and flare hard, push over and really pull that collective up.

Theoretically you don't need high speeds and could autorotate almost vertically. It's just more difficult to time everything right. Only thing necessary is keeping the rpm high enough to prevent blade stall. The forward speed you are keeping is your energy storage. Whenever your rpm gets too low, you can trade in speed for an increase of rpm by pulling the stick back gently (flaring). Keep the rpm near its upper limit, then you trade of rpm for decreasing descend speed when near the ground. Done. It's only about timing and keeping one eye on the rpm. May take a lot of practice...


Edited by Rongor
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Posted (edited)
23 minutes ago, Rongor said:

Theoretically you don't need high speeds and could autorotate almost vertically. It's just more difficult to time everything right. Only thing necessary is keeping the rpm high enough to prevent blade stall. The forward speed you are keeping is your energy storage. Whenever your rpm gets too low, you can trade in speed for an increase of rpm by pulling the stick back gently (flaring). Keep the rpm near its upper limit, then you trade of rpm for decreasing descend speed when near the ground. Done. It's only about timing and keeping one eye on the rpm. May take a lot of practice...

 

Actually, from my experience in DCS it's quite the opposite. 

During autorotation the descent rate easily falls below 10m/s. At that speed it's impossible get it to safe values by just collective alone, even if you start pulling at 100% RPM. 

 

In my experience it works like this:

flaring actually increases rotor rpm, so by a combination of flaring and pulling collective you can maintain rotor rpm for long enough to create just enough lift to cushion your landing. 

Without flaring rotor rpm drops too quickly and it doesn't generate enough lift.

Without enough speed the effect of the flare wears off too quickly (and you slow down too much and leave effective translational lift which makes the whole thing even worse).


Edited by PL_Harpoon
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Isn't it what Rongor said? "Whenever your rpm gets too low, you can trade in speed for an increase of rpm by pulling the stick back gently (flaring)."

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21 minutes ago, PL_Harpoon said:

Actually, from my experience in DCS it's quite the opposite. 

During autorotation the descent rate easily falls below 10m/s. At that speed it's impossible get it to safe values by just collective alone, even if you start pulling at 100% RPM. 

 

In my experience it works like this:

flaring actually increases rotor rpm, so by a combination of flaring and pulling collective you can maintain rotor rpm for long enough to create just enough lift to cushion your landing. 

Without flaring rotor rpm drops too quickly and it doesn't generate enough lift.

Without enough speed the effect of the flare wears off too quickly (and you slow down too much and leave effective translational lift which makes the whole thing even worse).

 

I agree that the slower you are, the fewer maximum descend rate is allowed.

 

Don't wanna brag but I just did 6 successful autorotations in a row. Only the first one was performed with gear up. In 3 landings I suffered only minor damage. In the other 3 I managed to land undamaged.

Preconditions: level flight at 350 meters, 170 kph...

 

Felt even a bit too easy if you ask me. In my opinion the rpm should drop much faster than in DCS. IRL you have to concentrate keeping the rpm within autorotation limits, here it was pretty forgiving...


Edited by Rongor
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Posted (edited)
4 minutes ago, Rongor said:

Preconditions: level flight at 350 meters, 170 kph...

That's what bothers me.

I too can perform successful autorotations with speed of 170kph.

The problems starts when I try to do it according to the instructions from the manual I attached above.

Try to do autorotations while maintaining 80-90 kph and you'll see that I mean.


Edited by PL_Harpoon
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The 170 kph were the start condition, when I shut down both fuel levers behind my left shoulder. 

I will pay more attention to the actual autorotation speeds at later test runs, when the kid is in the bed😉

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BTW, it is interesting that within the same manual, there is another section referring to autorotations.

This time there are no specific speed values to maintain and in fact states that:

Quote

Vertical rate of descent depends on flight speed and shall be within 12...25 m/s. The minimum vertical rate of descent corresponds to a flight speed of 120... 140 km/h.
Flight speed corresponding to the maximum range of gliding is 170. . . 190 km/h; at that the vertical rate of descent is 16 m/s.

autorotation page.png

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1 hour ago, Rongor said:

Theoretically you don't need high speeds and could autorotate almost vertically. It's just more difficult to time everything right. Only thing necessary is keeping the rpm high enough to prevent blade stall. The forward speed you are keeping is your energy storage. Whenever your rpm gets too low, you can trade in speed for an increase of rpm by pulling the stick back gently (flaring). Keep the rpm near its upper limit, then you trade of rpm for decreasing descend speed when near the ground. Done. It's only about timing and keeping one eye on the rpm. May take a lot of practice...

 

Yeah. I don't know if it's like that IRL, but in a Huey, I can get into hover, shut the engine down and keep zero speed all the way to the ground. Close, pull a lot of collective to decrease ROD, drop it a bit and use last RPM to cushion the landing. Not even close to that in even light Mi8. In Mi24, I use flare not to recover RPM, but to brake ROD. If done at right height, collective alone is enough to get you home before helicopter gains downwards momentum. Of course, that RPM gained in flare does help too

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Just did a few tests.

 

The result is no surprise: it's a matter of mass.

At 20% fuel I was able to perform a safe autorotation with glide speed of 90km/h by a sharp pull of the collective at the right moment and only a slight flare.

 

At 80% the same technique didn't work. The helicopter would just falls like a rock. After 3 attempts I did a simple test at altitude: I started a regular autorotation but pulled the collective at 300m to see how much altitude it takes to achieve the slowest descent rate and what descent rate you can achieve. As I suspected, the rate of descent went from >15 m/s to 5 m/s and it took about 100m to do so. Still, not enough for a safe landing.

 

Then I performed a safe autorotation with glide speed of 150 km/h and with flare at the end managed a safe landing.

 

I have tracks for all attempts, here are some of them. 

I'll try to record them to a video tomorrow. I've had enough for today 🙂

 

Here's a successful attempt at a 90kph autorotation with 20% fuel,

Hind - Autorotation 1 - low speed - low mass.trk

here's one of the attempt of doing the same with 80% fuel,

Hind - Autorotation 2 - low speed - high mass attempt 3.trk

here's the test at 300m

Hind - Autorotation 2 - low speed - high mass test.trk

...and here's a successful landing with glide speed of about 150kph and 80% fuel

Hind - Autorotation 2 - high speed - high mass.trk

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vor einer Stunde schrieb PL_Harpoon:

As promised, the video of my yesterday's tests:

 

Nice demonstration. That aligns perfectly with my autorotation attempts yesterday. With full fuel tanks the recommended 80kmh always lead to a crash (at least if I am the pilot). With around 150kmh and flaring it is manageable. Gave you an upvote on youtube 😉

 

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I found that with fuel only, auto could be done at 120-140. If keeping weapons on pylons, 170 will get me home. Hard flare will bring TD speed to about 100 km/h.

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On 6/30/2021 at 11:14 AM, admiki said:

Yeah. I don't know if it's like that IRL, but in a Huey, I can get into hover, shut the engine down and keep zero speed all the way to the ground. Close, pull a lot of collective to decrease ROD, drop it a bit and use last RPM to cushion the landing. Not even close to that in even light Mi8. In Mi24, I use flare not to recover RPM, but to brake ROD. If done at right height, collective alone is enough to get you home before helicopter gains downwards momentum. Of course, that RPM gained in flare does help too

 

I can vouch for the technique he's describing here. I've seen him do it successfully many, many times in a row. I hope I get the hang of it soon! 😜

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