reported CH-47 flies mighty fine ... with the engines powered down!?

[shadowborn]

Bought the CH-47 today. Flew around a bit. Landed. Cut the engine levers to "stop", cut all generators, battery. The rotors would go down to idle, but still spin at idle for several minutes. I even started pulling a bunch of circuit breakers. While I was doing that, the helicopter took flight (with everything still powered down), which is when I started recording the video. It rose to 7.500 feet when FINALLY the idle noise and the rotor blades stopped. Even then, during free fall, it ganied RPM and very briefly even gained a few feet of altitude (at 4630 ft in the video).

Guys? This is ... wrong, no? I'm not going crazy, am I? 

 

Edited February 7 by shadowborn

[Lord Vader]

Hello @shadowborn

Can you please supply a track replay of this event?

Thanks for you cooperation. 

[shadowborn]

Hey @Lord Vader,

wish I had one. I will fully agree that this was a stupid thing to do, but I didn't save a replay that night and started the next flight. So unless there is anything else but the last replay in %userprofile%\AppsData\Local\Temp\DCS, it's gone. Sorry .

Edited February 10 by shadowborn

[shadowborn]

Hey @Lord Vader

Okay, it's not the replay of that flight, but I managed to replicate the issue in air. See "ch47_gain_alt_with_engine_off.trk". Short flight where I tried to loop the ch-47. This led to a power cut-out (generator overload? no idea). I then cut the fuel pumps and engine levers to "off". Notice how I can keep flying for some minutes and gain altitude (from roughly 7080ft to 7740ft) at some point, minutes into the engine shut-down and could keep flying indefinetly. The helicoper only starts to fall as I eventually reduce my throttle/collective from full to idle, but even then behaving very strange for my gut feel.

I also notice that after shutting down the engine after other flights, on the ground, the rotors take wildly different amounts of time to spin down. Sometimes it goes fast, sometimes it takes way longer (as also reported here). They seem to be affected by wind in general, but wind does not serve as an explaination why sometimes it takes minutes for them to stop, and in one instance, they never did (sorry, don't have a track file of that one). As for wind effect on the rotor blades in general, I have seen one instance of them spinning the "wrong way round" at a setting of 30kts wind in the mission editor; not sure if the gearbox on the real thing would even allow for that.

I have a feeling that the modeling of air through a falling helicopter makes the rotors spin, and they spin so fast that the heli gains altitude and can fly seeming indefinetly with engine powered down. This is just a gut feeling of what may be happening in the replay. Which just can't be realistic, as that would be a perpetual motion machine 

I also attach "ch47_20kft_engine_cutout_weird.trk", if you want to take a look at that. Maybe you can explain to me what's happening here. It's just another flight that seems odd to me. I took the ch-47 to 20k feet (service ceiling according to google). Shortly beyond 20k feet, I lost engines (altitude cut-out? I don't think I ran out of fuel ...). Initially, all displays cut out except one without master caution lamp. Then they came back, cut out again, this time with master caution lamp. The co-pilot's display stayed on all the time. Then, the helicopter falls almost gentle like a leaf, I was able to do a soft landing from a fall from 20k feet despite the rotors being near standstill at various times. Helicopters with engine out (as per the display) and nearly no energy in the rotor system, tumbling over at some point, should not recover to falling soft and gently at only a few feet per second in my mind. Plus, again, the rotors behave weird. It spun up when I reduced throttle, and down (i.e. braked) when I increased throttle, almost as if the rotors are wind milling, but giving it thrust reduces that windmilling effect.

Cheers!

ch47_20kft_engine_cutout_weird.trk ch47_gain_alt_with_engine_off.trk

Edited February 10 by shadowborn

[Lord Vader]

@shadowborn

Please keep one topic per thread. 20K is the service ceiling for the DCS: CH-47F. The flight model is still undergoing some refinement, please operate it within reasonable limits at the moment.

I'll look into your other track regarding engines operation while in cut-off.

 

[Lord Vader]

I've reported the item about the engine continuing to run with cut-off levers to off.

As for the other item, I've addressed above.