Minimum f16 upstick speed

[peter12213]

hi guys trying to perfect a display here but i keep stalling as i need to know the minimum aerosft f16 stall speed for a display here are some pics i need help on this so looking for f16 jockeys....

Not in control rudder ineffective after certain point..

looks great but i'm going at too high an alpha angle even if i'm at real world speed and angle any idea's???

result unrecoverable stall!! I need the actual stall speeds, plus angle of attack of the real manouveras done in real dispays!! please help!!

 

[bob1009vf101]

Minimum unstick speed has to do with getting the nose off the ground on takeoff roll...not flight. A little confused there... And stall speed doesnt matter for high alpha maneuvers. The wing on an F-16 has a very small thickness to chord ratio and the airfoil is camberless and not intended as a high lift device. During high alpha passes, the wing is stalled. There is little or no lift being created from a pressure differential. There is some lift being created from newtonian impact physics on the lower surface, but the majority of the 'lift' is thrust acting in place of the vertical component of lift. In real life a loss of thrust would be unrecoverable during this maneuver. Depending on how aggressive the maneuver is flown, AOA values between 40 and 60 degrees are possible...but again, AOA doesnt matter. The Blue Angles fly a flight attitude (pitch) of 45 degrees and use thrust to control altitude. There is no magic speed. The speed this maneuver is performed at varies greatly with gross aircraft weight, and therefore so does thrust required. Also, any airflow blanketed flight control surfaces (rudder) would be entirely ineffective during the maneuver. Yaw control on a single engine aircraft is therefore indirectly influenced by roll moments alone.

Its a very complicated process, sadly, not one that FSX can simulate properly with most models.

 

[JohnC]

Bob is accurate in the base aerodynamic principles he listed, however, the F-16 is quite remarkable (in my humble opinion) in it's aerodynamic properties. Most notably, once flow reversal has occurred in the boundary layer and separation occurs...the F-16's lift coefficient continues to increase well past the initial onset of the stall. Detailed information listed below.

Assuming a clean aircraft: Stall onset on the outer wing panel occurs at 20.4 Deg AoA and all lifting surfaces have stalled by 25 Deg. Maximum lift Coefficient is achieved at 35 Deg AoA. However, above 30 Deg AoA, the F-16 becomes prone to roll departure, Dutch Roll, and even experiences aileron reversal. As a consequence, the Fly-by-wire system kills lateral (yaw and roll) input from the pilot and assumes full responsibility for the respective control surfaces, although, it wasn't possible to model this behavior in it's entirety within FSX. For level flight high Alpha pass, try a speed of roughly 90 KIAS with a pitch attitude of 30-35 deg. You'll have to play around to find the right throttle setting, but it is definitely possible to achieve. Post 40 Deg AoA, the destabilizing moments can exceed the the stabilizing moments, which can lead to an uncontrollable departure and 60 Deg AoA is a neutral trim Deep Stall position. In reality, the latter requires a rocking pitch input from the pilot for a successful recovery.

 

[TAFKAM]

the speed accually is too low in the sim John....originally the speed would be around 110kts with a nose up position of 25/30 degrees.......that would do the slow alpha....

 

[JohnC]

Ray, yes and no on the response. Drag divergence is handled internally within FSX, and stall is automatically defined as the point of maximum lift. This can produce a moderate error on the real life speed vs sim speed. However, the AoA limit is accurate. We discussed this as seen below on 2008.07.13:

Ray, The data I came across states the F-16 produces a maximum lift at 35 Deg AoA. It's quite interesting (and frankly amazing), considering both the wing and the horizontal stabilizer are stalled at that point. The Outer Wing panels begin to stall at 20 Deg, and all suraces are stalled just past 25 Deg, which makes the pitching surfaces far less responsive, especially for nose down moments. I place a huge amount of credibility in this data because not only does it follow aerodynamic theory, but it comes directly from NASA. See the attached photos for an in flight verification. Compare one to the last outside photograph I sent you. I am not claiming the aircraft's AoA is 46 Deg in the picture, only that it is notably higher than 25 Deg.

 

[peter12213]

thanks for all the input guys it is just a limitation of the sim and you must have a higher speed than is done in real life but all the discussions have been a great help and interest to read!!