I Cannot Stop Mr Ito's XB-35 Flying Wing On touch Down At Beale.

C

casey jones

Charter Member
I Cannot Stop Mr Ito's XB-35 Flying Wing On touch Down At Beale.

Is there a way to modify the air file for Mr Ito's XB-35? My landing speed is 100mph, when I touch down I begin to bounce a little, then I pull back on the thottle applying the brakes and speed brake but I keep moving down the runway at 100mph...no stopping.


Cheers

Casey
 
Go to the .cfg file and make sure that there is not a minus sign in front of the brake scalar.

T
 
Hello-
I saw this thread and it occurred to me that I have this plane as well. My brakes worked fine- but I encountered something that seemed like a lack of brakes. I'll bet that you had full flaps on as you landed... what I realized after a few touch-and-go passes was that with full flaps, the aircraft pitches forward enough that your main wheels don't quite touch down as you roll down the runway on your nose wheel- the aircraft just floats along, and you run out of runway before she slows down enough to set the wheels down.
To see if you were fighting the same thing, try this- on your approach, use full flaps to slow her down. But just before touchdown, retract your flaps fully (F5 key). What I found was that she then set right down on all wheels, and I braked to a stop using less than half of the runway.
Ito-San has never been known to have the most accurate .air and .cfg files, and this bird is no exception. I suppose one could try to use the .air and .cfg files from the AlphaSim XB-35- they behave better.
Maybe someone knows which parameter controls the way the aircraft pitches forward when the flaps are extended- this isn't the first plane that I've encountered this with... I never quite found the magic bullet for it...
-Mike Z.
 
Look in the aircraft.cfg for the Flaps section.

This parameter affects pitch as a multiplier:


[flaps.0]

pitch_scalar= 1.0

Be advised that if you decrease this (.1 = 10% change effect) that you may have less runway to see on approach.

You can also reduce this parameter to decrease lift from flaps.
lift_scalar = 1.0

EDIT: You can also consider lowering your landing speed.
 
You're quite right Casey, and Milton too. When I was approaching to land, adding in flaps, the nose-down pitch was severe enough to keep the main gear off the surface so the brakes wouldn't work. Hitting F5 on touch down allowed the aircraft to settle to engage the brakes.
But there is more going on here. The cfg is missing the Flight tuning section which limits lots of options for adjusting flight performance. There was no pitch line in the flap section to adjust. The aircraft, from a full stop and idle power setting, began to roll and pick up speed, and on final (dirty and minimum power) the aircraft will barely bleed off airspeed to about 100. Everything seems oriented to the Energizer Bunny mode. For starters you can try these for some fixes:

In the cfg Flaps section, type in the additional line "pitch_scalar=0.28" This seems to alleviate the nose down issue. It will pitch up very slightly until it stablizes but this will help the main gear touch the ground on landing.

Go to the Weight and Balance section and change the values of the empty_weight_CG_position sec to -0.800000,0.000000,0.000000, again to help push the mains down a bit.

I couldn't fix all the forward drift when on the ground in idle. I don't know of a ground roll friction adjustment. In other aircraft it can sometimes be fixed by reducing the static thrust value, but that also can cause new problems elsewhere. However, in the TurbineEngineData section reducing the static_thrust to 3500, and in the Propellor section, changing the value for minimum_on_ground_beta to 0.000 helped a good deal. It also changed the power curve enough so air speed could effectively be dropped to land. I found that I had to get down to about 80-85kts on touch down to keep from ballooning. That seems pretty slow for this aircraft.

Adding a FlightTuning section would need to lots more time to experiment with and could be used to improve many other areas. Until then hope these offerings help out some
 
Hello again-
I also added the entries for flight tuning and lift and pitch scalars for the flaps. Using Milton's advice, I wound up dropping those scalars to .100 before it would let itself sit on the main gears enough for the brakes to work, and land with full flaps...
Aeromed is right, too, about the way this plane seems to hang in the air and not come down unless your airspeed is way down... something I wouldn't expect from a plane of this size. I think I got it off the ground once at 72 kts on my takeoff roll. I haven't worked on the thrust at idle issue because Ito-San has used a turboprop configuration (I believe this aircraft was piston-powered?) for a piston-engined plane- not the first time he's done this- so I'll probably copy the engine data from the AlphaSim XB-35 and go from there...

-Mike Z.
 
Having downloaded and had a quick look at it the problem is in the contact points, way to much static_cg_height=, no brake effect because the full weight is not on the tyres.

To prove it in sim sellect another aircraft go to spot view, press P to pause leave pause on, resellect the flying wing watch the model and press P again while watching the plane, it will sink onto the runway because static_cg_height is to much, another test is centralize your stick or yoke and press Y to go into slew and it will rise for the same reason.

I would fix the contact points first, to busy in FSX to want to take it on sorry
 
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