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Still having gear problem. (Read 207 times)
Jun 19
th
, 2006 at 6:44pm
Greg Ebnit EApilot
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EA Aeronuatics The Home
of Chrome!
Michigan U.S.A.
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I followed Miltons excelent advice on setting up my landing gear and it worked well. Problem is that when my aircraft gets low on fuel and when I land the gear become unstable again because of the lack of the fuel weight. I added the cargo weight to the aircraft weight to comppensate because for some reason when I put station load points in to try to balance the aircraft it becomes more unstable. I've tried to change the compression in the airfile that does'nt seem to help. So it is nearly impossible to taxi without having a gear crash when the fuel is low. Can anyone provide some insight? Thanks Greg.
(AN ODE TO GMAX) OOOOOOOOOOOHHHHHHHHH GMAX! How I sometimes want to hug and kiss it. And other times want to smash, berate, and delete it. Gmax how I love and loathe thee. The crashes the errors the reinstalls. Gmax you are the whomb of my aircraft design. Oh Gmax my designing creating temptress. It must be love for you have taken my heartdrive. By Greg Ebnit
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Reply #1 -
Jun 19
th
, 2006 at 9:10pm
Milton
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Can you post your contact points, you gross weight, your empty weight and where your CoG is right now?
Milton&&Dash 7, Aero Commanders, Howard 500, D18S, Spartan, XP47J, Beechcraft A28 (Grizzly)
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Reply #2 -
Jun 19
th
, 2006 at 9:25pm
Katahu
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Did you perform the needed calculations for the compression ratio? First, you measure the distance the gear compresses on normal parking to get the "Static Compression distance". Then measure the distance the gear compresses the most to get the "Maximum compression distance". I think you take the Static compression and divide it by the maximum compression to get the actual "Compression Ratio". Or is it the other way around?
This is as far as I can remember from the top of my head. I'm not that good at math.
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Reply #3 -
Jun 19
th
, 2006 at 9:55pm
Greg Ebnit EApilot
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EA Aeronuatics The Home
of Chrome!
Michigan U.S.A.
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Thanks guys. Following is the info requested. reference_datum_position = 0.0, 0.0, 0.0 // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline)
empty_weight_CG_position = 0.0, 0.0, 0.0 // (feet) longitudinal, lateral, vertical distance from specified datum
[WEIGHT_AND_BALANCE]
max_gross_weight = 2323880 // (pounds)
empty_weight = 1292200 // (pounds)
;Moments of Inertia
empty_weight_roll_MOI = 30000000.0000
empty_weight_pitch_MOI = 50000000.0000
empty_weight_yaw_MOI = 50000000.0000
empty_weight_coupled_MOI = 0
reference_datum_position=0.000000,0.000000,0.000000
empty_weight_CG_position=0.000000,0.000000,0.000000
max_number_of_stations=50
station_load.0=0.000000,0.000000,0.000000,0.000000
[contact_points]
//0 Class <0=none,1=wheel, 2=scrape, 3=float>
//1 Longitudinal Position (feet)
//2 Lateral Position (feet)
//3 Vertical Position (feet)
//4 Impact Damage Threshold (Feet Per Minute)
//5 Brake Map (0=None, 1=Left, 2=Right)
//6 Wheel Radius (feet)
//7 Steer Angle (degrees)
//8 Static Compression (feet) (0 if rigid)
//9 Max/Static Compression Ratio
//10 Damping Ratio / Water Rudder Effectiveness (0=Undamped, 1=Critically Damped) / 1.0 = normal
//11 Extension Time (seconds)
//12 Retraction Time (seconds)
//13 Sound Type
//14 Airspeed limit for retraction (KIAS)
//15 Airspeed that gear gets damage at (KIAS)
point.0 = 1, 120.5, 20.0, -19.0, 2000.0, 0, 3.0, 70.0, 1.4, 2.5, 0.7, 10.0, 11.0, 1, 220, 300
point.1 = 1, 120.5, -20.0, -18.0, 2000.0, 0, 3.0, 70.0, 1.4, 2.5, 0.7, 10.0, 11.0, 1, 220, 300
point.2 = 1, -16.5, -11.0, -18.5, 2000.0, 1, 3.0, 20.0, 1.4, 2.5, 1.00, 10.0, 11.0, 1, 220, 300
point.3 = 1, -62.0, 23.0, -18.5, 2000.0, 1, 3.0, 0.0, 1.25, 2.0, 1.00, 10.0, 11.0, 1, 220, 300
point.4 = 1, -62.0, -23.0, -18.5, 2000.0, 2, 3.0, 0.0, 1.25, 2.0, 1.00, 10.0, 11.0, 1, 220, 300
point.5 = 4, 44.5, 149.5, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 0, 0, 0
point.6 = 4, 44.5, -149.5, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 1, 0, 0
point.7 = 4, 147.0, -25.0, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 2, 0, 0
point.8 = 4, 147.0, 25.0, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 2, 0, 0
point.9 = 4, -23.5, -25.0, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 5, 0, 0
point.10 = 4, -23.5, 25.0, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 5, 0, 0
point.11 = 5, -79.5, 5.5, -1.5, 2000.0, 0, 0.0, 50.0, 0.0, 0.0, 0.1, 10.0, 11.0, 0, 0, 0
point.12 = 5, -79.5, -5.5, -1.5, 2000.0, 0, 0.0, 50.0, 0.0, 0.0, 0.1, 10.0, 11.0, 0, 0, 0
max_number_of_points = 21
static_pitch = 0.0
static_cg_height = 18.7
The pink box in the gmax scene is where the current flightsim reference point is located. Its not at the recomended position because of the length of the aircraft 450 ft. approx. Sliding it forward created an unaturel flight charecteristic when pitching the aircraft. (Tail movement)The grid is -18.7 ft. to the bottom of frame 100 close approx. Thanks for the reply. Greg
(AN ODE TO GMAX) OOOOOOOOOOOHHHHHHHHH GMAX! How I sometimes want to hug and kiss it. And other times want to smash, berate, and delete it. Gmax how I love and loathe thee. The crashes the errors the reinstalls. Gmax you are the whomb of my aircraft design. Oh Gmax my designing creating temptress. It must be love for you have taken my heartdrive. By Greg Ebnit
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Reply #4 -
Jun 19
th
, 2006 at 10:04pm
Greg Ebnit EApilot
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EA Aeronuatics The Home
of Chrome!
Michigan U.S.A.
Gender:
Posts: 483
Here is a shot of the gear config. on the ground.
(AN ODE TO GMAX) OOOOOOOOOOOHHHHHHHHH GMAX! How I sometimes want to hug and kiss it. And other times want to smash, berate, and delete it. Gmax how I love and loathe thee. The crashes the errors the reinstalls. Gmax you are the whomb of my aircraft design. Oh Gmax my designing creating temptress. It must be love for you have taken my heartdrive. By Greg Ebnit
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Reply #5 -
Jun 19
th
, 2006 at 11:23pm
Milton
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Props forever!
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Posts: 301
[quote author=Cosmottic link=board=airc;num=1150757080;start=0#3 date=06/19/06 at 21:55:05]Thanks guys. Following is the info requested. reference_datum_position = 0.0, 0.0, 0.0 // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline)
empty_weight_CG_position = 0.0, 0.0, 0.0 // (feet) longitudinal, lateral, vertical distance from specified datum
[WEIGHT_AND_BALANCE]
max_gross_weight = 2323880 // (pounds)
empty_weight = 1292200 // (pounds)
;Moments of Inertia
empty_weight_roll_MOI = 30000000.0000
empty_weight_pitch_MOI = 50000000.0000
empty_weight_yaw_MOI = 50000000.0000
empty_weight_coupled_MOI = 0
reference_datum_position=0.000000,0.000000,0.000000
empty_weight_CG_position=0.000000,0.000000,0.000000
max_number_of_stations=50
station_load.0=0.000000,0.000000,0.000000,0.000000
[contact_points]
//0 Class <0=none,1=wheel, 2=scrape, 3=float>
//1 Longitudinal Position (feet)
//2 Lateral Position (feet)
//3 Vertical Position (feet)
//4 Impact Damage Threshold (Feet Per Minute)
//5 Brake Map (0=None, 1=Left, 2=Right)
//6 Wheel Radius (feet)
//7 Steer Angle (degrees)
//8 Static Compression (feet) (0 if rigid)
//9 Max/Static Compression Ratio
//10 Damping Ratio / Water Rudder Effectiveness (0=Undamped, 1=Critically Damped) / 1.0 = normal
//11 Extension Time (seconds)
//12 Retraction Time (seconds)
//13 Sound Type
//14 Airspeed limit for retraction (KIAS)
//15 Airspeed that gear gets damage at (KIAS)
point.0 = 1, 120.5, 20.0, -19.0, 2000.0, 0, 3.0, 70.0, 1.4, 2.5, 0.7, 10.0, 11.0, 1, 220, 300
point.1 = 1, 120.5, -20.0, -18.0, 2000.0, 0, 3.0, 70.0, 1.4, 2.5, 0.7, 10.0, 11.0, 1, 220, 300
point.2 = 1, -16.5, -11.0, -18.5, 2000.0, 1, 3.0, 20.0, 1.4, 2.5, 1.00, 10.0, 11.0, 1, 220, 300
point.3 = 1, -62.0, 23.0, -18.5, 2000.0, 1, 3.0, 0.0, 1.25, 2.0, 1.00, 10.0, 11.0, 1, 220, 300
point.4 = 1, -62.0, -23.0, -18.5, 2000.0, 2, 3.0, 0.0, 1.25, 2.0, 1.00, 10.0, 11.0, 1, 220, 300
point.5 = 4, 44.5, 149.5, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 0, 0, 0
point.6 = 4, 44.5, -149.5, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 1, 0, 0
point.7 = 4, 147.0, -25.0, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 2, 0, 0
point.8 = 4, 147.0, 25.0, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 2, 0, 0
point.9 = 4, -23.5, -25.0, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 5, 0, 0
point.10 = 4, -23.5, 25.0, 1.0, 2000.0, 0, 0.0, 0.0, 0.85, 2.5, 0.30, 0.0, 0.0, 5, 0, 0
point.11 = 5, -79.5, 5.5, -1.5, 2000.0, 0, 0.0, 50.0, 0.0, 0.0, 0.1, 10.0, 11.0, 0, 0, 0
point.12 = 5, -79.5, -5.5, -1.5, 2000.0, 0, 0.0, 50.0, 0.0, 0.0, 0.1, 10.0, 11.0, 0, 0, 0
max_number_of_points = 21
static_pitch = 0.0
static_cg_height = 18.7
The pink box in the gmax scene is where the current flightsim reference point is located. Its not at the recomended position because of the length of the aircraft 450 ft. approx. Sliding it forward created an unaturel flight charecteristic when pitching the aircraft. (Tail movement)The grid is -18.7 ft. to the bottom of frame 100 close approx. Thanks for the reply. Greg quote]
Greg,
I see several issues:
1. Front gear distance to ground where one is a foot different than the other.
2. Contact point.2 which I thing is the center main gear is 11 feet off center
3. Contact point.2 also shows a steering angle of 20 degrees but shows also as a main, not steering gear. May be ignored.
4. The suspension animation is actually quite short for an aircraft that size and weight. I have that much+ on the Dash 7. I would recommend suspension at least equal to the height of the tires, but would prefer more. Secondly, given the longitudinal diffence between the outside mains and the center mains, it is possible you are crushing the suspension of the center gear main. I recommend making all the suspension animations equal in length and equidistant from the reference to the ground. i.e. all -18.5'
5. It is preferable to set the reference at the thrustline and near vertical CoG to minimize strong pitch moments due to thrust.
6. The longitudinal CoG/CoL should be at 1/4 root chord with the wing sweep properly denoted. This effectively moves the CoLift rearward more closely to where the mains are. Otherwise, rotation becomes a problem.
I'll stop now as it all is beginning to run together.
Milton&&Dash 7, Aero Commanders, Howard 500, D18S, Spartan, XP47J, Beechcraft A28 (Grizzly)
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Reply #6 -
Jun 20
th
, 2006 at 12:21am
Greg Ebnit EApilot
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EA Aeronuatics The Home
of Chrome!
Michigan U.S.A.
Gender:
Posts: 483
Thanks once again for the bail out Milton.
I'll try all that you suggest. Is there anything you do'nt know about Sim design? I ca'nt say thanks enough for all that you do here at the forum. Greg
(AN ODE TO GMAX) OOOOOOOOOOOHHHHHHHHH GMAX! How I sometimes want to hug and kiss it. And other times want to smash, berate, and delete it. Gmax how I love and loathe thee. The crashes the errors the reinstalls. Gmax you are the whomb of my aircraft design. Oh Gmax my designing creating temptress. It must be love for you have taken my heartdrive. By Greg Ebnit
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