FM question ...

[Kula66]

In FSG for VMAT-203, it says that one of the dangers with the AV-8B landing is when the flaps fully deploy:

 

'At the 180 position the pilot starts the approach turn descent and as the aircraft finally decelerates through the 165 KCAS the flaps program from 25° to 62° near instantly causing a strong nose down pitching moment.

(Page 62).'

 

I get the opposite when the flaps transition, ie. a large pitch up ... anyone any thoughts on this?

[jacobs]

Yes, I noticed a big pitch up when flaps fully deploy.

[DaveRindner]

I think that depends on your grossweight, a/c configuration, stores. If the center of pressure is aft of center of gravity, pitch up occurs. If COP is fwd of CG the pitchdown. Or is it vice-versa. The nozzle angle may be the critical factor. If nozzles are fully back flaps have small droop. As nozzle angle is increased the flaps follow. At maximum flaps are drooped so much that they act as airbrake, lift device, and ground effect generators. Last few feet prior to touchdown Harrier feels like a hovercraft. Even without H20 VSTOL , Harrier may be reluctant to settle. Especcially when it is light, all stores expended, and fuel is 750 TOT , and remaining H20 is 300 or less. The trick is to develop a feel for smooth slow throttle retard to touchdown. Practice practice practice.

For VSTOL recoveries at less then 50kn KIAS or KIAS , nose into wind, I turn AWL ON, and Master Mode to VSTOL.The HUDSON symbology makes it easier to level and alight a/couple for two point toychdown.Harrier gear is strong, but if you touchdown on main first, the a/c will rotate down and bounce the front gear. By cycle gear likes nice two point touchdowns.

[Ramsay]

'At the 180 position the pilot starts the approach turn descent and as the aircraft finally decelerates through the 165 KCAS the flaps program from 25° to 62° near instantly causing a strong nose down pitching moment.

(Page 62).'

 

I get the opposite when the flaps transition, ie. a large pitch up ... anyone any thoughts on this?

 

I see something similar to the description in the FSG but at a lower airspeed ~125 KCAS (clean, 3000 lb fuel, GWT 17865 lb).

 

A big detail missing from your description is aircraft configuration i.e.

 

This effect is most pronounced in the TAV-8 due to the heavier nose.

...

A typical scenario that induces this is a weak pull in the break that does not decelerate the aircraft quickly so on the downwind the pilot is

 

• fast

• throttle at idle

• gear down,

• nozzles at 60°

• flaps at STOL

 

When the flaps move from 25° -> 62° @ ~165 KCAS, I see the vv climb and witch's hat drop (pitch down), then as speed bleeds off - the vv and Witch's Hat drop unless corrective action is taken (increase power and then pitch for 8° AoA i.e. Witch's Hat and vv together).

 

Note: I've a 'feeling' optimum cruise (@ 8° AoA) is also a little lower than suggested (190 KCAS / 220 KCAS) but am happy the main FM features seem already modelled and would need to check I'm not mixing up CAS/TAS before I'd file a bug report - there's still so much to do on the AV-8B, lol.

 

Tested in DCS Open Beta Steam 2.5.2.19682

Edited July 24, 2018 by Ramsay
typo

[Kula66]

Thanks all ... I think the Razbam have done a great job with the AV-8B, it's so much fun to fly!