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FSXA Engine Start Issues

JoeKumanchik

JoeKumanchik

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10
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unitedstates
Can someone give me a brief discription on what parameters are used when starting an engine using CTRL+E. I am working on the aircraft.cfg file of a high powered single prop plane and discovered a problem using a modeled starter switch vs CTRL+E to start the engin. Also the difference is only apparent when using FSX Accelerator. This is the procedure I used, Mags on, A bit of throttle, Full rich mixture, and Hit the starter, the plane moves forward lifts off and flips over in a very very short amount of time. All with the parking brake on. This is not the case when using FSX without accelerator no matter how you try to start it or with FSX & Accelerator using CTRL+E. Im thinking some parameter is in play that needs to be adjusted and /or nulled out.

Thanks
 
OK here is an update on my start up issue.

It seems to only be a factor when the Air Fuel Mixture lever is in the CUT position. If the mixture lever is above say 10% the model will attempt to start and will not flip over. It looks like when a CTRL+E is pressed to start a model the mixture control is automaticly adjusted so the model will not flip when used.
So now the real question is, why does it flip over when the mixture lever is in the cut position. I have tried adjusting the Prop MOI with very little effect. Lowering the power ratio is the only adjustment that has made a difference.

Thanks
 
Hi
post your engine and prop sections of the aircraft.cfg
it may also be a balance or contact point issue but we will start with the easy stuff first :)
Wozza
 
This is a racing version of a Hawker Sea fury. The engine and prop specs came from the builder and some of the scaling values were to achive max speed of 450 kias as well as a cruse speed of 290 Kias @ 27" mp and 1700 rpms.


[piston_engine]
power_scalar=1.25
cylinder_displacement= 186.11
compression_ratio= 6.70
number_of_cylinders= 18
max_rated_rpm= 2900.00
max_rated_hp= 3100.000
fuel_metering_type= 2
cooling_type= 0
normalized_starter_torque= 0.045
turbocharged= 1
max_design_mp= 62
min_design_mp= 0
critical_altitude= 0
emergency_boost_type= 0
emergency_boost_mp_offset= 0.000
emergency_boost_gain_offset= 0.000
emergency_boost_duration=0
fuel_air_auto_mixture= 0
auto_ignition= 1
max_rpm_mechanical_efficiency_scalar=1.000
idle_rpm_mechanical_efficiency_scalar=0.500
max_rpm_friction_scalar=.8
idle_rpm_friction_scalar=1



[propeller]
thrust_scalar=1.2
propeller_type= 0
propeller_diameter= 13.50
propeller_blades= 4
propeller_moi= 56.000
beta_max= 75.000
beta_min= 10.000
min_gov_rpm= 1700.000
prop_tc= 0.010
gear_reduction_ratio= 2.096
fixed_pitch_beta= 20.000
low_speed_theory_limit= 80.000
prop_sync_available= 0
prop_deice_available= 0
prop_feathering_available= 0
prop_auto_feathering_available= 0
min_rpm_for_feather= 0.000
beta_feather= 0.000
power_absorbed_cf= 0.900
defeathering_accumulators_available= 0
prop_reverse_available= 0.000
minimum_on_ground_beta= 0.000
minimum_reverse_beta= 0.000
 
Hi
Hmm that all looks fine ...so it must be in the airframe somewhere
a balance issue with either the distribution of weight or a contact point issue
I normally 0,0,0 all the fuel tanks loadout stations if no luck then start on checking for scrap points that might be hitting the deck or gear that maybe to soft or damage prone
Wozza
 
Thanks for taking a look. I will dig through the weights and scrape points and will update on what ends up fixing the issue..
I had been playing with the MOI's but did not think about the scrape points
 
OK I tried the suggestions but no luck. I did however sacrifice some top end speed by reducing the power_scale value in flight_tuning from 1.25 to 1.125. This stopped the flipping issue.

Although this airplane has 5 fuel tanks, I modeled and set the weights of three. 1 bulkhead and two wing tanks. I tried zeroing out the wing tanks and removed all but the pilot weight station (The later of the two is going to be done anyway because this a racing plane) this changed how the plane flipped but did not stop it. I tried changing and zeroing all the contact points with no luck.
Thanks for the input and I am willing to try anything else anybody may come up with.

:)
 
JoeKumanchik said:
OK I tried the suggestions but no luck. I did however sacrifice some top end speed by reducing the power_scale value in flight_tuning from 1.25 to 1.125. This stopped the flipping issue.

Although this airplane has 5 fuel tanks, I modeled and set the weights of three. 1 bulkhead and two wing tanks. I tried zeroing out the wing tanks and removed all but the pilot weight station (The later of the two is going to be done anyway because this a racing plane) this changed how the plane flipped but did not stop it. I tried changing and zeroing all the contact points with no luck.
Thanks for the input and I am willing to try anything else anybody may come up with.

:)
Click to expand...
Hi
Im no FDE guru but I try very very hard not to alter the tuning sections from 1 if I have to then something wrong somewhere and may effect the model somewhere else :)
you say you altered the power_scaler and it stop flipping ? ok set that to
1 and fix the max airspeed else where ;)
My quick and dirty method of fixing max airspeed in level flight is to
A:set fuel level to 1/2 when test pilots did speed runs they never do it with full tanks ;)
B: get the aircraft up to it preferred max speed height set the autopilot up so it maintains heading and height.
C: make sure weather is dead calm no winds aloft no wind period
D: let the aircraft fly along for a few min on auto pilot and check airspeed
E: pause the sim and open the airfile in Airedit and alter the section 1101
drag section Cdo drag co zero lift..reduce the number by 10, then save reload aircraft and repeat.Reducing the number speeds up the aircraft max speed raising the number slows her down.

If you need to drop the zero lift as low as 20 or below to get the speed near the desired speed then you have issues else where (I tend to try for around 50 to 80)
90% of the time its the prop tables the rest of the time its engine or wing tables
hope this helps
Wozza
 
Last edited:
Thanks for the information. I am new to this so I am still learning what data changes result in what changes in handling. And the .air file still holds many mysteries for me. It has not been a problem with slower more common general aviation aircraft but this one has been a bear to make fly by the numbers. I have spent an enormous amount of time searching articles, tutorials, and forums for information to learn as much as I can only to find out there is so much more, so I do appreciate you taking the time to share your knowledge.

I too believe keeping the tuning numbers at 1 yields better flight stability so I am going to give your method a try tonight. I have also been determined to keep the engine, prop, and geometry data as real as I can and still have the proper results. So I expected to have to tweak more in the .air file.

If anybody can recommend good reading material in learning the in's and out's of the .air file I would love to know about it.

Thanks again
 
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