Do you think the word "some" better describes a significant amount of drag or an insignificant amount? I think it's used to mean "not much" in the pilot notes.
Since the point of the dive flaps is delaying compression, not air braking, I think it's a good simulation. If I called it a complete model you could disagree.
There is a lot more going on than the writers of that manual knew at the time. They reference a high speed stall and loss of lift as the cause of the nose heaviness.
This has been subsequently discovered to be incorrect. You really can't rely on period aerodynamic explanations when it comes to transonic aero.
Critical mach number for an airfoil is the speed at which local flow becomes supersonic. When local flow exceeds the speed of sound a shock wave forms and as speed INCREASES ABOVE CRITICAL MACH the shock wave pushes the center of lift of the airfoil backward. This movement of the center of lift backward is what actually causes the pitch down moment of the aircraft.
This local supersonic flow happens on the curved surface of the airfoil (The top on a wing).
A dive recovery flap located on the opposite side well forward (33% of the chord in the case of the P38) is effective because it creates LIFT which effectively moves the center of pressure forward. This extra lift well forward effectively moves the critical Mach Number UP because it is countering the undesirable pitch down known as Mach Tuck, but it does this through aerodynamic forces that SHOULD be represented in the flight model.
LIFT produces INDUCED DRAG. Sticking something into the relative wind produces PARASITIC DRAG.
Something producing lift at Mach .67 creates a large amount of drag as well.
Producing lift at the 33% chord point also creates a pitch up moment (the ENTIRE POINT of the Dive Flap) This pitch moment should be present in all flight regimes and dramatically so at high Mach numbers.
So let's list the errors in the current P38 flight model that we can easily spot from this discussion.
1. The Dive Recovery Flap should produce Lift, Drag and have a SUBSTANTIAL pitch moment associated with its use. The report Dobs posted gives very specific numbers. 45 degree deployed 1.5 inch flaps at Mach 0.725 at 25,000 feet will produce a 3.5 G pullout. AHIII certainly does not model any of this.
2. The critical Mach Number is the ONSET of of the effects of "compressibility" or Mach Tuck. The critical MACH number of the P-38 is .67 in some sources and .69 in others. This is the Mach number where the effects BEGIN. The effects worsen with higher Mach numbers, resulting in the nose heavy dive. They should not be in full effect at .67 Mach as they are now in AHIII.
Here is a good intro on the gap between Critical Mach Number and the onset of compressibility and other effects.
http://www.flightlearnings.com/2009/08/28/high-speed-flight-speed-ranges/So, no, it isn't a good simulation of the Dive Recovery Flap on the P-38. It appears to be a very simple code fix with no real attempt to accurately model the aerodynamics of the Dive Recovery Flap properly.
