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DCS Huey Autorotations

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DCS Huey Autorotations

Post by (A/229) Huckleberry on Sat 17 Feb 2018 - 15:55

Can anyone weigh in on the accuracy of the autorotation physics in the huey module? It seems to be the case in the other rotorcrafts too but I don't fly them nearly as much so it doesn't bug me.

Of course I have no real flight experience, but I seem to get way too much lift at the final stages of autorotation, as long as I don't keep the collective maxed out. To put it another way, it seems too easy to cowboy a really sketchy landing with no power, for instance flaring too soon and coming down vertically with near 0 airspeed; or wrenching the collective all the way up early on, when coming in too fast, and still being able to drop the collective back to a reasonable pitch while retaining bunch of potential lift for landing.

I feel like any rotor speed lost IGE is permanent, and sort of milking the collective for lift is a very bad practice, even though I've been getting away with it in the simulator.

Does that sound right? Comments & critiques appreciated, esp. if you've performed autorotations IRL.
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Re: DCS Huey Autorotations

Post by (D/229) Xtra on Sun 18 Feb 2018 - 10:03

The huey rotor systems is able to maintain a lot of momentum. Heard some people say that after a landing you could still pick it up and almost make a 360.
Losing rotor rpm with no airspeeds to trade would mean you wont be able to increase it anymore. But you would milk the collective as much as possible to make for a smooth landing. Coming in with a bit of foward air/groundspeed isnt such a big deal on a runway but a whole different story when landing outside

Not sure what you mean with too much lift in the final stage?
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Re: DCS Huey Autorotations

Post by (A/229) Huckleberry on Sun 18 Feb 2018 - 11:55

Thanks for the reply Xtra.  I didn't think a 360° turn after landing w/o power would be feasible.  Sounds like my ideas of those flight dynamics are wrong.

(D/229) Xtra wrote:Not sure what you mean with too much lift in the final stage?

I was thinking that the graph of collective input over time in the final stages of autorotation, which represents the best/most efficient use of lift, would resemble a positively-sloped line.  That is, collective pitch is gently and steadily increased in order to maintain smooth and constant lift.  Maybe this "line" would be slightly curved to resemble a gentle exponential graph, but the takeaway is, the collective is not milked: it's is only ever increased, and the graph does not look "wavy".

My rude understanding of physics concludes that any "waviness" in the graph, which translates to "milking" of the collective, would only serve to decrease the efficiency of the autorotation, meaning more milk = less lift to use later.

Note that this is in the final stages of landing, so there's really no generating any *more* rotor speed at this point, we've just got to leverage what we have remaining.  If we take too big a bite out of the pitch early on, we get a bunch of lift for that brief moment, but in doing so we lose a bunch of rotor speed we can't get back, even if we bottom the pitch again.

This, doubled with the idea that there is a steep dropoff at a certain point in the rotor speed, below which the helicopter becomes brick-like and unrecoverable, I found it suspicious how hard it was to actually get to that point.

I'd like to scrap my notion that more milk = less efficiency if you think that's not the case.  Actually the more I think about it, it makes more sense to draw lift only when you need it, and conserve all the rotor speed you can when you don't.  Now I'm leaning towards the idea that a strategic perturbation in pitch control isn't nearly as inefficient as maintaining increasing amounts of pitch.

Sorry to ramble... Thanks again for your input!

EDIT: Once I think about it in terms of conserving angular momentum, it becomes embarrassingly obvious. Of course it makes sense to always be conserving as much angular momentum as you can, even if that potentially means rocking the collective.


Last edited by (A/229) Huckleberry on Wed 7 Mar 2018 - 9:54; edited 2 times in total (Reason for editing : Eureka moment, felt obligated to update)
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Re: DCS Huey Autorotations

Post by (D/229) Xtra on Sun 18 Feb 2018 - 21:00

In the th67 the IP initiated the auto by going to idle. You had to counter by dumping the collective and get the rotor rpm under control within normal operating limits and keep foward airspeed. You maybe needed a touch of collective to keep the rpm under its max allowed rpm but basically its was all the way down. When needed to do turns you may needed to increase the collective a bit to counter the increase in rotor rpm in the turn and once rolled out you wpuld lower it again. Cant remember at which altitude you started the flare. Once in the flare you increased collective by using peripheral vison, bleed foward speed and you just pulled  collective until she started to settle on the ground. I dont think it was maxed out but i believe at least 3/4 of full deflectiin. Also never looked at rotor rpm once in the final stage of the flare so cant really say at what rpm you would let the aircraft to settle but can imagine it is pretty close to its normal min and max operating limit.
With the 64 we would only do power on autos (power levers in fly position) and terminate to a hover. The rotor system does not like low rpm with a lot of load on it since the blades would cone and flex a lot at that point if being bleeded too much. It would bleed rotor rpm quicker then a 67 but also respond quicker to cyclic and collective inputs in the auto.
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Re: DCS Huey Autorotations

Post by (A/229) Huckleberry on Sun 18 Feb 2018 - 21:40

I see. Then maybe it's not either/or regarding the 2 collective control strategies I mentioned earlier, but rather, it's about finding the happy medium between the two, which is best suited for your particular airframe.

Is a pattern with increasingly large airframes having a steeper rpm dropoff? Or is it the other way around, the larger airframes have more weight and momentum twirling around up there, making them more resilient to rpm loss?
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Re: DCS Huey Autorotations

Post by (D/229) Xtra on Sun 18 Feb 2018 - 23:20

Depends on the rotor system. You can have a high or low inertia rotor system. The 64 is considerd high. Still every airframe will have some differences ofcourse eventhough both are considerd high. Dont know how the 64E is autorotating compared to the D since it now has composite blades.
Basically you can say high interia: maintain rpm longer but harder to regain once low and vice versa for low systems
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Re: DCS Huey Autorotations

Post by (A/229) Huckleberry on Mon 19 Feb 2018 - 5:32

Awesome. Thanks again Xtra
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Re: DCS Huey Autorotations

Post by (A/229) Comanchero86 on Mon 19 Feb 2018 - 8:16

The infamous 360 is a myth. Even the wonderful Huey can't do a 360.  But you can actually roll the throttle off from 6600 and lift to a two foot hover make a 180 Pedal turn and set down again. Had a crazy Company IP try it when I was at Campbell. I think we got to about 150 degrees of turn before we had to settle. Made a damn mess of the rotor head as the oil in the blade grips leaked out of the seals. Oops,  sorry for the war story. Anyway,  I'm probably explaining what you know already, but when you think of autos in the Huey after you flare to slow the aircraft, you should consider that when raising collective, you are " spending" rotor RPM you will not get back. Any rpm you spend is gone and depending on your altitude above the ground could result in a bad day. If the DCS model does not reflect this, it's wrong. Basically after flare,  it's pull collective as needed to ride the cushion, settle to the ground. Hope you find this reply helpful.
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Re: DCS Huey Autorotations

Post by (C/229)Samri on Mon 19 Feb 2018 - 10:26

Having done countless touch down auto's in the Huey....albeit many moons ago,
from a cognitive perspective, I find it is close enough....to satisfy me that is.
Fly the correct technique for huey and it works fine.

ie - Flare - pause - Initial - pause - Cushion........

If anyone is interested, I can make a demo video with the usual IP Quack,
and also try to point out any differences with the real huey - what I can recall that is. drunken

And as Comanchero says - I've done it - do a 180 turn from the ground and resettle.
This was usually demo'd to students to show the inertia of the blades.
Good luck with a 360 - but with infinity dcs hueys and no shortage of spare transmissions you can always have a crack at it. High risk of touching down while still turning - and with a low rpm, which will definitely cause a "Spike Knock"** - at the least", but hey - I Haven't heard of a dcs crew chief or CO complain yet.

** Spike Knock:

At the bottom centre of the tranny is a metalic spike which protudes in to a metal cup in the roof.
If the tranny rocks laterally too much - the spike will contact the side of the cup (you will hear a definitive "Knock" or bang.  It's then time to shut down - you're done for the day.
I have spike knocked several times usually after a (student) mishandled auto touchdown, that I incompetently didn't rectify in time  Embarassed

Did it once at Rucker as well out in the area where the student was doing a slope landing in a confined area and dropped the downslope skid on too quickly - I couldn't catch it time.  Though I would have classified it as "spike Tap", ie from experience I knew it was OK, but....the book's the book so had to shut it down and wait for a rescue Huey to come pick us up...You guys remember "Ironside - didn't you fly it there for a while Flyer??

It was embarrassing walking back in after being dropped back at Lowe Field by Ironside - a White Medivac Huey.
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Re: DCS Huey Autorotations

Post by (A/229) Comanchero86 on Mon 19 Feb 2018 - 11:06

Ah yes, memories. That would be "Flatiron" Samri.
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Re: DCS Huey Autorotations

Post by (A/229) Huckleberry on Mon 19 Feb 2018 - 11:13

Neat stories, & useful info.

(A/229) Comanchero86 wrote:...think of autos in the Huey after you flare to slow the aircraft, you should consider that when raising collective, you are "spending" rotor RPM you will not get back.

Yeah, that part I understand; I was unsure about how much more/less efficient it would be [after you flare to slow the aircraft] to lower the collective again when you don't have a great need for it.  I'm understanding now that it's more efficient than the alternative (keeping the collective at the point it has been raised to), because with the latter, you're still spending RPM you could be conserving by lowering the collective again.

Additionally, I'm understanding it very much depends on airframe/rotor inertia/collective response, and especially quality and smoothness of the autorotation.

(C/229)Samri wrote:If anyone is interested, I can make a demo video with the usual IP Quack,
and also try to point out any differences with the real huey - what I can recall that is. drunken
Personally I'd be stoked to see a video like that Samri, I think a bunch of people, not just 229th would find that particularly interesting.  But only if that sounds like something you'd enjoy doing.
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Re: DCS Huey Autorotations

Post by (A/229) Comanchero86 on Mon 19 Feb 2018 - 11:56

(A/229) Huckleberry wrote:Neat stories, & useful info.

(A/229) Comanchero86 wrote:...think of autos in the Huey after you flare to slow the aircraft, you should consider that when raising collective, you are "spending" rotor RPM you will not get back.

Yeah, that part I understand; I was unsure about how much more/less efficient it would be [after you flare to slow the aircraft] to lower the collective again when you don't have a great need for it.  I'm understanding now that it's more efficient than the alternative (keeping the collective at the point it has been raised to), because with the latter, you're still spending RPM you could be conserving by lowering the collective again.


Additionally, I'm understanding it very much depends on airframe/rotor inertia/collective response, and especially quality and smoothness of the autorotation.

(C/229)Samri wrote:If anyone is interested, I can make a demo video with the usual IP Quack,
and also try to point out any differences with the real huey - what I can recall that is. drunken
Personally I'd be stoked to see a video like that Samri, I think a bunch of people, not just 229th would find that particularly interesting.  But only if that sounds like something you'd enjoy doing.

Maybe I'm misunderstanding you but if the engine quits you bottom the collective. You would only raise it slightly if you have a M/ R overspeed as you descend. In the decent from altitude as long as the M/R rpm is in the green arc of the tach you are in good shape.  After  you flare for decel you level and then pull collective to abate your rate of decent until you settle to the ground. If you you have a bit of pull left after you touch down without slamming into the ground, good for you. If you pull it all and bleed off lift before you are on the ground,  then you did it wrong. I think we are in accord on this though.
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Re: DCS Huey Autorotations

Post by (C/229)Samri on Mon 19 Feb 2018 - 17:33

In AUTOrotation, it is the upflow of air through the rotor disc that provides the rotation - like on those pinwheels you get from a fair.
If you notice in autorotation, the vertical speed is a good 2000 fpm - ish. That is what is required to maintain RPM at a constant speed when the collective is fully down.
Once you pull on the collective in the flare or the cushion, you increase the drag on the blades and your rpm bleeds - quickly.
All you do by reducing the collective after that, is increase your rate of descent which will require even more cushion pitch pull, that you now may not have.
There simply is not enough rate of descent at this point to maintain the RPM left.
As long as you don't overdo the initial pitch pull, there is always sufficient rpm for the cushion - if you've done it right.
I have had the collective up to the stop recovering from a student's ambitious cushion which hung us up a lot longer than what is comfortable.
Thank heavens for those high inertia blades.  the same thing happened to me in an OH-58........ That broke the tailboom because there was nothing left at 3 foot.
That 3 foot took the longest time to fall too! I felt like Wile E Coyote - just before he drops into a canyon  affraid
I knew it was gonna be bad. - I was unstrapped and out the door before the dust settled to confirm the worst!!
Another embarrassing walk back to the lines with helmet in hands. Embarassed
That was the 5th Autorotation accident that year - The CO was not a happy fellow.
Price of training though - You must learn to do autos to the ground - it's the last few inches that kill ya - not how well you flew the profile.
Not to mention the negative training of doing power terminations - by rolling throttle back on prior to a proper developed flare and actual pitch pull amounts - with zero power.

Just to emphasise the technique:

After the initial pitch - hold the collective in the initial pitch position and allow it to take affect (pause) - do not reduce it.
(You are trying to reduce the rate of descent - not increase it.) Then level the attitude  -pause - then cushion as and when required.

Just a quick note on RRPM maintenance in Autorotation:

If you turn during steady autorotation, the increase of "G" causes the blades to "cone" upwards, which effectively reduces the rotor diameter.
This will increase the RPM much in the same way an ice skater increases their spin rate by bringing their arms into their body.

Also a heavier Gross Weight will cause a higher RPM due to an increased rate of descent - ie more uplow of air through the disc.  In these cases, collective is increased enough to keep RPM within limits.

Also if you increase your airspeed, the RPM will increase as well.  This is because you have to lower the nose to increase the speed, this in turn increases your rate of descent,
thus increasing your RRPM because of an increased upflow.
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Re: DCS Huey Autorotations

Post by (C/229) Frenchy on Tue 20 Feb 2018 - 21:57

Hey Samri, very helpful. I second the request for an Autorotation, maybe even with a TACview profile of the descent/flair afterwards. From reading above I think people are getting confused about regaining rpm in the initial decent and in the final flair/settle (which seems unlikely to impossible compared to the decent given my very limited knowledge)

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Re: DCS Huey Autorotations

Post by (C/229)Samri on Wed 21 Feb 2018 - 7:30

No worries, I'll start putting something together.
I'll do my best to produce a good quality video/s - might take a few weeks in between trips.

Also Having "teething" problems with 2.5 atm!!
I think I might have solved that late last night.......after spending all day trying to fix it!!

It just kept on freezing within about 5 mins of play.
Looks like an issue with triple screens and FOV which the new engine can't deal with - from what I've read.
Appears reducing FOV to 120 may fix it, but the Instrument panel is in my face!

Anyone else having this problem??
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Re: DCS Huey Autorotations

Post by (A/229) Huckleberry on Wed 21 Feb 2018 - 10:58

A final thanks to everyone involved for your input. Being able to ask a bunch of pilots about technical stuff is pretty invaluable for someone like me. I don't think it'll ever lose its novelty Cool

o7
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Re: DCS Huey Autorotations

Post by (C/229)Samri on Fri 2 Mar 2018 - 17:08

Here’s a demo video.

I’ll eventually put together a series of videos covering everything from the Basic auto to advanced autos and Forced Landings.


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Re: DCS Huey Autorotations

Post by (D/229) Gizzy on Fri 2 Mar 2018 - 22:51

A truly excellent lesson video Samri, great teaching style, thanks a lot for taking the time to do this... really appreciated.
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Re: DCS Huey Autorotations

Post by (A/229) Chic on Sat 3 Mar 2018 - 7:50

Awesome.

How do we archive the youtube to the 229th training site?

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Re: DCS Huey Autorotations

Post by (H/229) Skeeter on Sat 3 Mar 2018 - 9:58

In the real world the auto would be your last ditch effort to save the crew and as much of the AC as possible correct?
Given you have a failure or damage to something VERY important and/or needed to fly. lol
I mean to me seems like the idea is to make the actions become muscle memory and fly the AC to the ground based more on what needs to be done.
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Re: DCS Huey Autorotations

Post by (D/229) Gizzy on Sat 3 Mar 2018 - 10:39

(A/229) Chic wrote:...How do we archive the youtube to the 229th training site?

Done.  Additionally SIX may add it to 'Check Ride Criteria - Senior Wings' post similar to the BW post.
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Re: DCS Huey Autorotations

Post by (A/229) Huckleberry on Sat 3 Mar 2018 - 14:39

Great video Samri! Taught like a seasoned IP.
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Re: DCS Huey Autorotations

Post by (C/229)Samri on Sat 3 Mar 2018 - 16:28

Thanks guys,

The idea is that approved training videos will be uploaded to the dedicated 229thIP youtube channel by the IP’s as they are produced, and also linked to the Instructor’s Tent video thread. Member’s should also subscribe to the channel.

Now that my youngin’ is off to “Skool”, I’m getting a little more time to get back to DCS and the Bn.

I hope to try and produce as many “Quick-ish” Basic (and Advanced) video lessons as I can to assist in learning the techniques & standards needed for check rides.

I hope they will be of some benefit.

I’ll work on “Part 2 - Practice Auto’s” during the coming week.
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Re: DCS Huey Autorotations

Post by (A/229) Comanchero86 on Sun 4 Mar 2018 - 3:54

Any Rucker IP would have been proud to make that video Samri. Nice work.
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Re: DCS Huey Autorotations

Post by (HHC/229) Skullz on Wed 7 Mar 2018 - 1:05

Samri that was a great video, very well done! I'm looking forward to more...
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Re: DCS Huey Autorotations

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