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Plane spins horizontally in a clockwise direction (Read 3850 times)
2nd Jun, 2011 at 3:04pm

Boeing227   Offline
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..after updating the engine parameters in the air file and aircraft.cfg.

Hey guys, I downloaded a Transall C-160 for FS2004 that was made by Vladimir Zhyhulskiy, and I was disappointed with the FDE. I found that the engines were jumpy and the parameters are based off that of the default King Air 350. (ie: rated_N2_rpm=29992 [<-the rating that most turbines in FS for some reason have], min_govnerned_rpm=22550, etc)

I have been developing an interest in doing flight models for various aircrafts, and I decided to do this as my first project.
So what I went ahead and did was back up the original aircraft.cfg and air file, and used AirEd and AAM V2.2 to edit some of the parameters in the air file. I borrowed the turbine engine parameters from Rick Piper's Vickers Vanguard (same RR Tyne turboprop engines as C-160) because I found that the engines in the Vanguard handled very realistically smooth. I also borrowed the propeller, and "turboprop engine" parameters from the Vanguard cfg and entered them into my C-160 cfg.
After doing that, I studied the Vanguard's air file in AirEd, and opened the C-160's air file and entered in the same engine/prop parameters.
So basically what I did was rip the engines off Rick Piper's Vanguard and stick them onto my C-160 Transall. Tongue

Now I went to test this bird with the new engines in FS, and when I went to taxi, I noticed that the plane only wanted to pull to the right. I mean the engines handle great now, but the plane was spinning to the right no matter how hard I pull to the left with the joystick. I will never go straight forward!

SOOO finally the question: What has caused this to happen? All I did was like I said; rip the engines off Piper's Vanguard and stick them onto this C-160, I never changed any of the flight tuning parameters or anything, just the engines. What should I do?

I love the C-160 Transall, and I have always wanted to realistically fly one in FS.
 
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Reply #1 - 4th Jun, 2011 at 6:29pm

garryrussell   Offline
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Have you got two left hand engines instead of a left and right???
 
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Reply #2 - 9th Jun, 2011 at 2:29pm

jimslost   Offline
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For what it's worth, I've never seen - or heard of - a turbo prop twin that had counter-rotating engines.  In fact, I can only think of three twins so built, the Lockheed P-38, the late model Piper Twin Commanche, and the Piper Seminole.  I don't think that's your problem, at least not in and of itself.

My first thought is that you might have inadvertently placed both engines on the left wing in your aircraft.cfg file.  It's an easy thing to check (always check the easy stuff first!):

[GeneralEngineData]
engine_type =0
Engine.0 =6.340,
-5.000
, 2.90
Engine.1 =6.340,
5.000
, 2.90
fuel_flow_scalar =1.00000
min_throttle_limit=-0.25000
master_ignition_switch = 1

If both engines have the minus (-) before the value defining their lateral positioning, the sim will place both engines on the same (left) wing, giving you the yaw you describe.

If this isn't the problem, you may want to make certain your torque and precession values at the bottom of your .cfg file's [flight tuning] section are reasonable:
   hi_alpha_on_roll=1.0
   hi_alpha_on_yaw=1.00
   p_factor_on_yaw=1.00
   torque_on_roll=1.0
   gyro_precession_on_roll=1.0
   gyro_precession_on_yaw=1.0

If those are all in line, your next step will probably involved digging into the specifics of torque curves and prop effectiveness in your .air file to see if they're appropriate for your airplane.  That will take a bit of work and probably more tools.

Good luck.
j
 
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Reply #3 - 11th Jun, 2011 at 4:03pm

Boeing227   Offline
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*Homer Simpson voice* "D'oh!!" *facepalm*

That's exactly where I went wrong! I entered it in that the C-160 has 4 engines from the Vanguard, and the 2 I started were the left two engines and that caused the plane to pull to the right!
Quick and easy fix, I copied the engine position parameters under [generalenginedata] from the old C-160 aircraft config and plugged them into this new file. Now the plane has 2 engines, goes straight, and turns when I want it to! Smiley

Alright so I tested the plane and it taxis beautifully, when I want it to taxi at 10kts, it will hold that speed with the throttles say about 3% cocked. I took off on the runway and it lifted up off the ground no problem, maintained a speed of around 135-150kts after takeoff (when it reached about 100kts is when it started to lift off). Flaps were set at 10 degrees.

So basically all is pretty much good, I took her for a test flight and she performed great. There are still a few minor bugs to fix and a few tweaks and adjustments to do here and there, but I am about say 80% happy with it.

When I have any further questions I will let you guys know!

Plus once I am done and 100% happy with this project I will be posting it online to download for sure! Smiley

Thanks for your help and support!
 
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Reply #4 - 14th Jun, 2011 at 7:42am

garryrussell   Offline
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So sften a simple solution but a trap we all fall into at times

Glad you're sorted Smiley

The C-160 Tynes were a little more powerful than the Vanguard

Also, I've not got a size but the props look more like the 16 foot as fitted to the CL-44 rather than the Vanguards 14.5 foot...might be worth checking out. Undecided

Garry




 
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Reply #5 - 14th Jun, 2011 at 2:12pm

Boeing227   Offline
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You are right, the C-160 does have a larger propeller diameter! I looked it up and it's 18 feet. I don't know if changing the diameter of the props affects flying performance though... does it?
 
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Reply #6 - 15th Jun, 2011 at 12:37am

jimslost   Offline
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On a recip, changing the prop diameter will definitely impact aircraft performance.  I've never done the flight dynamics on a turboprop, but I would expect to find similar results.  You can always try it and report back to us! Smiley
 
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Reply #7 - 18th Jun, 2011 at 4:17pm

Boeing227   Offline
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Hey, I entered in 18 feet for the prop diameter and tried it. I noticed that the props were a little bit more powerful however nothing overly significant.

I have a question, what does increasing the prop MOI do?
 
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Reply #8 - 19th Jun, 2011 at 11:54pm

jimslost   Offline
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Posts: 337
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Good question.  What I've noticed on recips is that with higher prop MOI values, they turn a bit more slowly as the starter winds them up (reducing the starter torque will have the same effect) and they come to a stop more slowly when the engines are shutdown (more inertia at work).  When my old harddrive crashed at the end of May I lost a lot of my notes on things like this; hopefully someone else can add to my answer.
j
 
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Reply #9 - 23rd Jun, 2011 at 8:44pm

Boeing227   Offline
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I have read something somewhere that stated exactly what you said that when you increase prop MOI that the props become "heavier" and take longer to wind up and slow down.
 
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