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Guest jshyluk

Autorotation and Settling With Power (VRS)

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Guest jshyluk

I am expanding my review horizons to include helicopters. I think that FSX has done a good job of expanding the role of the rotorcraft in sim. However, like turbo-chargers and lighter-than-air vehicles, FSX kind of seems to just approximate rotor flight, and there are limits in flight that seem to be based on what fixed-wing aircraft can do.Two things I am trying to do and failing with are autorotation and settling with power (vortex ring state). In the former, (on the top-secret model I am reviewing), I cut the power, disengage the clutch, yet as the rotors slow down, so to does the forward speed of the 'copter, so that I cannot maintain airspeed for the autorotation, and I plummet to the ground. I am initiating the autorotation from a safe altitude and speed as given by the height-velocity diagram.On the other hand, my attempts to simulate a VRS are also failing. In this case, I am supposed to plummet to the ground, but instead I rise like a balloon. It's like all of the air is clean air regardless of how I handle the chopper. I have to simulate these events with multiple helicopters now to see if the fault lies with FSX or with the particular model I am researching. If anyone has any experience they can share to speed up this process, I up for it. Jeff ShylukAssistant Managing EditorSenior Staff ReviewerAVSIM

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Guest DaveAthay

I'm a real-world helicopter pilot and play with them in FS, too, although I've been disappointed with a few things. Autos are definitely one.A couple of tips on autos that might help: Make sure you enter the auto with the VSI at or below zero. This is very, very important to the sim. Otherwise, you will lose Nr.In the auto itself, Nr should not decrease. At all. I trained on Jet Rangers and I'm currently transitioning to the H-60 type. The 'Ranger autoed at 96% Nr and the Seahawk autos between 100% and 106%. In my one session of attempted practice autos in FS, I noticed that Nr droops and does not recover on entering unless you 1) enter with the VSI below zero and 2) bottom out the collective and then immediately put a little bit back in. The second one is extremely unrealistic.The guys over at Hovercontrol and some of the other helo sim sites probably know all about autorotating in FS helicopters, realistic or not.Good luck!Dave

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Guest jshyluk

Thanks, Dave, this is exactly the kind of answer I was hoping for. I had forgotten about Hovercontrol, thank you very much for reminding me. Looks like I have some more autorotation practise. I will try your hints. Mostly, I would just fly somewhere above the Dead Man's Curve and then cut the fuel and disengage the clutch. I figured that would be a good enough start for autorotation. Still, the blades would stop and I would get a good, close-up view of the ground texture. Bottoming out the collective only seemed to aggravate the problem. FSX doesn't seem to want to simulate VRS, either. My problem is the opposite: I try to make the manouevre as lethal as possible, but the helicopter refuses to sink. EDIT:I just tried out your autorotation technique. It works! The first few tries were rough, but I noticed the difference, at least the Nr stayed at useable levels. I seem to need to add a fair bit of collective after I drop it to the bottom, and then it's like landing a glider! I think I had a better autorotaional landing than some of my powered landings! Jeff ShylukAssistant Managing EditorSemior Staff ReviewerAVSIM

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I don't want to sound too much like an advert but as far as I know, so far our aircraft at Dodosim.com are the only ones to have helicopter behaviours such as VRS, LTE, and handling changes during autos. The list is a lot longer but like I said, this isn't an advert.The default helicopter dynamics are pretty scant and vary between the two main airfile types. The engine management does not really exist in either, the 206 doesn't even have a starter, the R22/Eh101 type has a malfunctioning governor. More advanced stuff like turbine hotstarts took years to create and probably only appeal to the helicopter realism nut but surely we deserve a starter and an engine that doesn't range over 70% rpm when idling (including impossible negative torque).There is a basic rotor droop in the R22 style airfile which is a plus point.Handling problems begin with the basic issues like the tail rotor being linked to power settings and the throttle and collective are blended when they should be seperate.All that is before you get into the dynamics. Flap back, vortex ring state, settling with power, and retreating blade stall are not modelled at all and must be added by "unsupported" means.Some auto functionality is there but they are far from satisfactory. Rotor RPM does not exceed the governor settings, the controls do not respond properly with the power off. None of the control changes associated with autos are present. The Aces have tried to improve things and the Jetranger now has some response to airflow through the rotor disc but only if you maintain forward speed (so no autos from the hover).Ground effect is modelled but you don't really fall off the edge of the air cushion the way that you should, translational lift is better in the Robinson than the Jetranger as it only exists in forward flight for the Jetranger. Torque reaction exists and I think tail rotor drift was added in fsX.With the Acceleration add-on it is now possible to have multi-engined helicopters and winch loads which is very welcome.It would be very nice to see the default helicopters brought up to the standard of the default Fixed wings

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Hi,Blubottle - don't forget to sign your postings, and welcome to the forum. I have to agree that the helicopter sim you mentioned hasgone to great lengths to get rotorcraft flight much better than whatis in FS9. When will there be FSX versions?I also wanted to mention that Moore's H-412 sim (available at hovercontrol.com) is m-u-c-h better than the default Robinson and Jetranger in in FSX. If one is a novice (e.g. me) and moves to Moore's 412, be ready for a shock - it is much more sensitive and less forgiving than those in FSX.dan "lensman" davison


--
Dan "lensman" Davison
PMDG_T7_sig.jpgrs

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Sorry about the delay, I don't check in here too often as there is very little helicopter traffic.I agree that Jordan's work is probably the best freeware heli available.I am working on fsX aircraft at the moment. The advanced 206 for fsX hit a problem when I was badly let down by the main contributer at a critical time. However we are in the late stages of recruiting a new software engineer with experience in pro simulatorsMy sig in my profile does not seem to be working or editable for some reason. I will try to correct that.Mark AdamsDodosim

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Mark,Thanks very much for the info. There are a bunch of us waiting for Dodosim's 206. One of the home health nurses that comes to IV somemeds into me is a blackhawk pilot in the army reserve, and made itback from Iraq. We sit and try (well, I try; he flies) the FSXhelis. His comments are mostly not repeatable but I've learned alot about how not to fly a helicopter. My sig is broken too, arggh.dan davison


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Dan "lensman" Davison
PMDG_T7_sig.jpgrs

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