Autorotation’s!

[b101_uk]

Anyone else having difficulties with autorotation’s?

It seems as if the skids have too much grip to slide resulting in nosing over if almost any forward speed is carried into the landing on flat ground (airfields)

But more importantly at a >60Kts IAS <130Kts IAS attitude (correct for an MD500E) it is very hard to maintain or gain any rotor RPM on the decent prior to flare, also the transition into flare also doesn’t seem to put in or take out a high enough energy/RPM into/out of the rotor dependent on condition of transition method.

It’s almost if its related to the excess of down thrust at 0% collective that is working agenised maintaining or gaining rotor RPM during autorotation i.e. as if excess blade pitch at 0% collective is conspiring to slow the rotor witch you would normally do by applying collective in conjunction with maintaining forward speed & rate of descent to keep the rotor within the >410RPM to <523RPM limits.

Myself in game even with 3 additional passenger for extra weight 0% collective and optimum speeds rotor RPMs always fall to ~80% (~375RPM) even at >3000ft/min descent with no means to recover or stop losing that RPM, even at an aggressive flare it only just reaches ~88% (~410RPM), with just the pilot in the number are ~75% (350RPM) and ~80% (~375RPM) just as the transition loads up. (Being done in the throttle closed position)

MD500E (taken from the MD500E ROTORCRAFT FLIGHT MANUAL - Emergency Procedures)
410RPM to 523RPM (~88% to ~108% - green zone) rotor speed,
Below 468rpm (~98%) rotor speed warning takes place,

Adjust collective pitch according to altitude and airspeed to maintain rotor speed between 410 and 523 RPM.

Autorotation specs (ENGINE FAILURE >500ft AGL):
Maximum glide distance @ 80Kts IAS / 410rpm #1
Minimum rate of descent @ 60Kts IAS / 410rpm #1
Maximum speed for autorotation = 130Kts IAS

#1 = If operating at reduced rotor RPM to extend glide or reduce rate of descent, restore rotor RPM by lowering collective prior to flare out.

The implication of the above official MD500E data is with just a pilot in and less than a full tank of fuel Maximum glide distance (80Kts IAS) or Minimum rate of descent 60Kts IAS both at 410rpm should relatively easily be maintained with some collective applied in order to maintain 410RPM and that RPM should be able to be regained well above 410rpm in the region of >470RPM or more as noted by “If operating at reduced rotor RPM to extend glide or reduce rate of descent, restore rotor RPM by lowering collective prior to flare out.”

Any thoughts?

[nightsta1ker]

I have determined that realistic autorotations in the preview are not possible.

Hopefully this is ironed out before the final release.

[b101_uk]

Some autorotation attempts.



4 people + full fuel.

[.kju [PvPscene]]

While I have no idea about realism here, you look way too fast here.

In ArmA to make it work, you need to reduce your speed.
You can do so by immediately pressing the 'decrease thrust' key action after you loose
the engine and by pitch backwards already during the decent, like you do shortly before the landing.

[b101_uk]

The speed was 60kts to 80kts IAS which is correct, what maybe makes it look fast is the >3000ft/min descent rate without rotor RPM gain, if you go slower than <60kts IAS then you will have a steeper descent which requires more stored rotor RPM to pull out which is made harder because the game is not allowing sufficient rotor RPM to be gained.

e.g. of real life autorotation:
MD500E 180deg full down autorotation


full down autorotation in a Robinson R22


360deg full down autorotation


full down autorotation


S-92 full down autorotation


MD500E full down autorotation


EC-120 full down autorotation


Huey 180deg full down autorotation

[.kju [PvPscene]]

Good videos. Thanks.

Don't get me wrong. I am NOT saying you are wrong.
I just explained my experience with arma.

Now while it seems a real helicopter can take a higher speed on ground impact/landing,
it seems in most videos they decelerate more just before landing compared to your ToH samples.

In any case it seems like a valid issue to me.
To put it also down in the CIT might make it more likely for the developers to spot it.
http://dev-heaven.net/projects/toh-cit

[EagleEye[GER]]

Yeah, would be great to have these features in the CP soon. I guess, they focus on content now and flight model tweaking later. Though, we should not expect a flight model like in X-Plane or Black Shark.

How detailed will the flight model be? (Will it model details such as retreating blade stall, vortex ring state or realistic auto rotation procedures?)
* Yes, yes and yes.

[WarriorM4]

I haven't been able to auto-rotate either.I would like to know why the helicopter has that sporadic shake every once in a while to.Its also evident in the video above that was posted by b101_uk.

[b101_uk]

Now while it seems a real helicopter can take a higher speed on ground impact/landing,
it seems in most videos they decelerate more just before landing compared to your ToH samples.

I quite agree in “real life” they do slow to a slower speed in the flare before levelling out for touchdown, but that would be indicative of them being able to maintain more rotor rpm on the decent and in essence being able to apply some collective to effectively slow the rotor from going over-speed and thus reducing the rate of descent or to reduce collective to regain RPM, they also get more energy from the flare so can naturally slow more and can have slightly longer to level out/land at a lower speed because of the extra RPM and that’s besides the extra cyclic control authority they would have to level out from the flare.

With the exception of the S-92 clip all the other clips I posted show lightly loaded helicopters, the S-92 was at maximum take-off weight, if you look at the abundance of clips on youtube both from inside and outside it becomes clear from looking at the rotor RPM gauges (inside) it’s no bother to maintain ~100% RPM up to just before transition to flare and that during flare they will get maximum RPM >100% while applying some collective as they trade the rate of descent energy for the forward speed energy in the ground effect zone, or from the outside you hear the rotor RPM climb on entry into the flare.

---------- Post added at 10:58 AM ---------- Previous post was at 09:29 AM ----------

Anyway, some official factual rotor RPM during autorotation from the “ROTORCRAFT FLIGHT MANUAL MD 500D - Model 369D” (30 Sep 2010 revision, MD Helicopters Inc.)

Taken from section IV Normal Procedures - Autorotation RPM:
485rpm @ 2250lb gross weight @ 60kts IAS (sea level to 1000ft) with the collective fully down.
With gross weights above 2250lb increase collective control as required to maintain approximately 485 RPM.
Rotor speed will decrease approximately 10 RPM for each 100 pound reduction in gross weight and increase approximately 6.5 RPM for each 1000 foot increase in density altitude.

Implications derived from other statements in the “ROTORCRAFT FLIGHT MANUAL MD 500D - Model 369D”
The Empty Weight/minimum flying weight is 1538lb so is +fuel +passengers +cargo weight etc, which logically gives a minimum ~414RPM @ 60kts IAS (sea level to 1000ft) excluding fuel, pilot/passenger & cargo weight which only server to increase RPM.
The MTOW is 3000lb so the rotor RPM could increase by ~75RPM to 560RPM unless it was checked by collective being applied to hold >485RPM <523RPM @ 60kts IAS (sea level to 1000ft).
Maximum fuel weight is 402lb (234L) with optional self-sealing tanks to 416lb (242L) with standard tanks.

Thus if you are in a MD500D flying and you have to autorotate after you have run out of fuel and you weigh 170lb and you are intend to land at just above sea level from 1000ft you would reasonably expect to see at the very least ~17RPM to account for your weight and a further ~414RPM for the helicopters weigh giving a total of ~> 431RPM @ 60kts IAS which would also mean if you wanted to achieve maximum glide or minimum rate of descent you could apply collective to maintain 410RPM at either 60kts or 80kts or regain some RPM afterwards.

[b101_uk]

dev-heaven.net issue 23276 - Light helicopter AKA: MD500D - autorotation rotor RPM.