Landing the ALphasim Jaguar....failure after failure!

O

OBIO

Retired SOH Admin
HELP! I'm flying and I can't get down!

I have tired time and time again to land the Alpha Jags...and end up with a crash every freaking time. Either the plane goes bouncing like crazy and ends up in a crash or the drag from the drag chute (linked to the speed brakes) deploys as soon as the back wheels touch down, and with so much drag, the the front gear breaks.

I adjusted the contact points to get them to line up with tires...they were about 2 feet forward of all the wheels. I will paste the new contact points so someone else can give them a try as see if they need additional tweaking or if it's just my horrible handing skills that are causing the problems.

[contact_points]
static_pitch = 1.6
static_cg_height = 8.2
tailwheel_lock = 0
gear_system_type = 1
max_number_of_points = 9

point.0 = 1, 11.5026, 0, -8.55, 2500, 0, 1, 25, 0.11, 3, 0.8, 6, 4, 0, 260, 300 //front gear
point.1 = 1, -7.42, -4.5998, -8.1166, 2500, 1, 1.2, 0, 0.5, 2.5, 0.85, 5, 7, 2, 260, 300 //left out tire
point.2 = 1, -7.42, -3.3, -8.1166, 2500, 1, 1.2, 0, 0.5, 2.5, 0.85, 5, 7, 2, 260, 300 //left inner tire
point.3 = 1, -7.42, 4.5998, -8.1166, 2500, 2, 1.2, 0, 0.5, 2.5, 0.85, 7, 5, 3, 260, 300 //right out tire
point.4 = 1, -7.42, 3.3, -8.1166, 2500, 2, 1.2, 0, 0.5, 2.5, 0.85, 7, 5, 3, 260, 300 //right inner tire
point.5 = 2, -12.128, -14.158, -0.728, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0 //left wing scrape
point.6 = 2, -12.128, 14.306, -0.728, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0 //right wing scrape
point.7 = 2, -18.275, 0, -3.298, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0 //tail scrape
point.8 = 2, 23.092, 0, -3.465, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0 //nose scrape

OBIO
 
OBIO, I tried your settings (in FSX) and it works fine for me. With 50% fuel left, full flaps, airbrakes out, I touched down at approx 125 kts, no bouncing.
 
50% fuel...maybe that's the problem. I take off with a full load of go juice, fly out a bit, turn around and come in for a landing...so I am carrying 95% or more fuel....landing weights are a lot lower than take off weights for a reason. Need to drop my take off fuel load when testing landing behavior. Duh! Sometimes it's the little things that get ya time and time again.

OBIO
 
If you're just going out for some circuits, knock the fuel back to about 35-40% before you start. Most of my new plane tests consist of taking off at max weight, then adjusting the fuel to 20% before I try to land.
 
Panther,

I've hit the deck at everything from 100knots all the way up to 400knots...and it always comes out the same: firetrucks, screaming women, crying babies and sheep who will grow up not knowing the joy of playing Pong while drinking ice cold glasses of Tang.

OBIO
 
Jaguar

Odd. She seems fairly docile on approach and touchdown. I'm not sure what the manual says for touchdown speed, but full flaps at 160 knots seems spot on for me and the stock FM that comes with the Jaguar.
 
I just did a landing....20% fuel left, 145knots, gentle glide in to the runway, easy peasy touch down....then BOUNCE BOUNCE BOUNCE CRASH! Maybe my tires are over inflated? Or I need new shocks? Or the crew chief on my Jag is one on those wise cracking East LA car guys and he put some hydraulics on my bird. That's it...I'll blame it on Chico!

OBIO

I commented out (the //) thing contact points 2 and 4 (the inner main wheels) hoping that would reduce the bounce. Nope...a nice gentle 145knot touch down, very long shallow approach, gently touch down...and she started bouncing and just went down hill from there. I'm heading over to the flight dynamics forum and hope that some one there can shine a light on a solution.
 
I got it fixed. I tweaked some of the compression and dampening ratios and now the bird handles like a dream on landings. Even on a 195 knot hard landing, the plane only bounces twice then settles down for a nice roll down the runway. At 150 knots, landings are wonderful.

Here are the revised contact points if anyone wants to give them a try.

[contact_points]
static_pitch = 1.6
static_cg_height = 8.2
tailwheel_lock = 0
gear_system_type = 1
max_number_of_points = 9

point.0 = 1, 11.5026, 0, -8.55, 2500, 0, 1, 25, 0.35, 3, 0.8, 6, 4, 0, 260, 300
point.1 = 1, -7.42, -4.5998, -8.1166, 2500, 1, 1.2, 0, 0.75, 2.5, 0.85, 5, 7, 2, 260, 300
point.2 = 1, -7.42, -3.3, -8.1166, 2500, 1, 1.2, 0, 0.75, 2.5, 0.85, 5, 7, 2, 260, 300
point.3 = 1, -7.42, 4.5998, -8.1166, 2500, 2, 1.2, 0, 0.75, 2.5, 0.85, 7, 5, 3, 260, 300
point.4 = 1, -7.42, 3.3, -8.1166, 2500, 2, 1.2, 0, 0.75, 2.5, 0.85, 7, 5, 3, 260, 300
point.5 = 2, -12.128, -14.158, -0.728, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0
point.6 = 2, -12.128, 14.306, -0.728, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0
point.7 = 2, -18.275, 0, -3.298, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0
point.8 = 2, 23.092, 0, -3.465, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0

OBIO
 
Panther_99FS said:
Probably need to do a long, flat approach......I had to do this in a F-104..,
Click to expand...

The approaches I was making were long long flat flat approaches over the desert to Edwards AFB. No obstacles, just long leisurely approaches. And the bird still bounced herself to death....but it's fixed now!

OBIO
 
OBIO said:
The approaches I was making were long long flat flat approaches over the desert to Edwards AFB. No obstacles, just long leisurely approaches. And the bird still bounced herself to death....but it's fixed now!

OBIO
Click to expand...


I wonder in reality if Edwards ever saw a Jaguar at allÉ
eeekkk my question marks seem to have gone weirdÉÉÉÉÉÉ`
 
Don't know if Edwards ever hosted a Jag. I use Edwards as my testing ground for jets and large planes and Orcas Island for GA sized planes. At some point, I need to create my very own scenery for to serve as my virtual aircraft restoration center. KOBO will be the identifier I use for it. A couple nice long paved runways, a few grass strips, lots of hangars and work shops and machine shops and such. Toss some statics around the place...would be nice to have some derelict statics...some planes with the wings off, stripped down fuselages, maybe a few tail sections standing up on end. Oh and a nice large lake nearby for amphibs and floats.

OBIO
 
point.0 = 1, 11.5026, 0, -8.55, 2500, 0, 1, 25, 0.11, 3, 0.8, 6, 4, 0, 260, 300 //front gear

OBIO, good job in recognizing the culprit.

This red highlite represents static compression and max-static ratio. If you do the math, the suspension has a little over 1" compression, and the 3 makes the suspension as hard as concrete. Easing the static compression to +3" helped you and you might reduce the ratio of 3 to a 1 for less stiffness.
 
Now that the plane lands great, it's ground handling is way off. It tips over like a drunked hippo in turns. Will have to find a balance that give acceptable ground handling and acceptable landing behavior.

OBIO
 
Ah yes, much gnashing of teeth and additions for websters dictionary of vitriolic slang. Don't forget theses are just points in a stream of electrons flitting across a monitor. I'm glad someone brought up true flight specs for the real thing as a comparison. I don't know them either but I'll find them and see what gives. That drunken wobbling on the ground is an effect of too much gear compression, roll MoI and narrow wheel separation. I've found it on many jets as they need the MoI to fly with stability at Mach 1+, but then on the ground, well... My fixes have had to incorporate some cheating to protect air performance. Like moving the main gear points a bit further outboard while reducing the compression distance, then messing with the damping ratio to eliminate bouncing. Lots of time just with these variables.

I just sprung for a new joystick that crapped about 2 months ago so it's fun to able to fly again.
 
OBIO said:
Now that the plane lands great, it's ground handling is way off. It tips over like a drunked hippo in turns. Will have to find a balance that give acceptable ground handling and acceptable landing behavior.
OBIO
Click to expand...

Try widening the main gear (yes I know that's cheating LOL) and get rid of the double wheels, you do not need them:

point.0 = 1, 11.5, 0.0, -8.5500, 2500, 0, 1, 25, 0.35, 3, 0.8, 6, 4, 0, 260, 300
point.1 = 1, -7.4, -6.0, -8.1166, 2500, 1, 1.2, 0, 0.75, 2.5, 0.85, 5, 7, 2, 260, 300
point.2 = 1, -7.4, 6.0, -8.1166, 2500, 2, 1.2, 0, 0.75, 2.5, 0.85, 7, 5, 3, 260, 300
point.3 = 2, -12.128, -14.158, -0.728, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0
point.4 = 2, -12.128, 14.306, -0.728, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0
point.5 = 2, -18.275, 0, -3.298, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0
point.6 = 2, 23.092, 0, -3.465, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0

This trick has also helped to solve problems with planes tipping over after carrier deck landings.

BTW: Have you tried the UKMIL mods - I like their flight model better, plane handles nicer imho.
 
hschuit

I was just logging in to report that the ground handling was vastly improved by moving the gear out to +/-6.0. It takes a real effort to tip the bird over now. And landing is sweet still.

I haven't tried the UKMIL mods. Where can I find them? Well, on the UKMIL site most likely...so I will have to register over yonder.

OBIO
 
These were the related parts I altered, yes some are blasphemous. I didn't get far with the power stuff but as it is an STOL type effort I'd guess the dirty landing speed to be between 130 and 136 depending on loadout but it tops out at about M1.6 so I've got some fiddling ahead. Arrows show specific line values within a group that were changed.

[weight_and_balance]
// ACM V2.2
max_gross_weight = 34612
empty_weight = 16975
reference_datum_position = 0, 0, 0
empty_weight_CG_position = 0.2, 0, -2.0
empty_weight_pitch_MOI = 145430
empty_weight_roll_MOI = 14412
empty_weight_yaw_MOI = 35277
empty_weight_coupled_MOI = 0
max_number_of_stations = 0
[flight_tuning]
cruise_lift_scalar=0.9
pitch_stability=1.7
roll_stability=1.08
yaw_stability=1.3
parasite_drag_scalar=1.2
induced_drag_scalar=1.300
elevator_effectiveness=1.5
aileron_effectiveness=2.0
rudder_effectiveness=0.6
elevator_trim_effectiveness=1.2
aileron_trim_effectiveness=1.000
rudder_trim_effectiveness=1.000

point.0 = 1, 12.00, 0.00, -8.60, 2000, 0, 1.0, 40.0, 0.2, 2.5, 0.6, 6, 4, 0, 260, 300
point.1 = 1, -5.00, -5.20, -8.32, 2500, 1, 1.2, 6.0, 0.6, 2.5, 0.7, 7, 7, 2, 260, 300
point.2 = 1, -5.00, 5.20, -8.32, 2500, 2, 1.2, 6.0, 0.6, 2.5, 0.7, 7, 7, 3, 260, 300

[brakes]
toe_brakes_scale=1.23
parking_brake=1
[TurbineEngineData]
fuel_flow_gain=0.006
inlet_area=5.000
rated_N2_rpm=29920.000
static_thrust=6000.000
afterburner_available=1
reverser_available=0


PS: Now I know what SEPECAT is-- Société Européenne de Production de l'Avion d'École de Combat et d'Appui Tactique
 
aeromed202 said:


Société Européenne de Production de l'Avion d'École de Combat et d'Appui Tactique
Click to expand...

If I had to say that, the closest I could come to it is Septic Tank. So, from now on I will refer to this plane as the Septic Tank Jaguar.

OBIO
 
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