Stability and Control characteristics of the Early Mark Spitfires

[Crumpp]

Can we have a analysis of figures 16 17 & 18 pointing to the instability in these test? It would appear tha 15 is an anomaly when compared to the later test.

It is different conditions.

In Figure 15 we see the result of the pilot just pulling the stick back and entering a turn. That is the inherent stability of the aircraft without pilot input. It tells us the workload the pilot needs to exert.

In figure 16, he pushes the stick forward in the measuring equipment.

In figure 17 and 18, he demonstrates the stability thru careful flying.

Figure 15, In other words it is the measured results of what happens if you are new player and you turn the Spitfire and keep the stick pulled back like a stable aircraft to maintain the turn.

In figure 16 we see the proficient but not the expert at controlling the aircraft. He pushes forward and his ability to control the aircraft improves. He still is not getting that steady level of acceleration.

In figure 17 and 18, we see the pilot carefully matches the unstable accelerations to produce a steady level of acceleration.

Klem,

The aircraft in the game acts stable both static and dynamic. It returns to trim and dampens the oscillation. Only in a steady state climb does it begin to act neutral.

I don't know the games code, but it seems like they made it "just statically stable" in level flight without the dynamic instability. When an aircraft enters a climb, the stability margin is reduced so we see the neutral static stability.

The spin modeling is excellent for a game. It took an average of at least two turns to recover when correct input was held. I liked it.

The stall behavior when reached is good too.

The issue is the amount of control required to maintain a turn is not representative of the longitudinal instability.

The inability to exceed the airframe limits. You can pull as hard as you want on the stick without fear of breaking the airplane.

The buffet effects are under modeled. In the game, The turn rate improves IN the buffet without any advantage for correctly flying a maximum turn rate performance turn. The turn performance does not begin to taper off until just before the stall when the slope becomes rather steep. That is not correct. Turn rate should decay in the buffet as a function of the strength of the buffet.

The buffet itself is under modeled. It is like a nibble when we see from the NACA report it imparted noticeable accelerations on the aircraft. Those accelerations are quantified in figures 13 and 14 of the NACA report.

In other words, your turn rate in the game improves in the buffet until just before the stall point and the airplane does not shake as the real thing.

That is part of the stall warning. The idea is to have it so you know to back off and not stall. It is essential to the control of an longitudinally unstable aircraft to have that large and distinct stall warning as well as the ability to maintain control in it. The large accelerations warn of the impending stall and increase the power required to make the turn. This also encourages realism. He rewards the players that fly on the edge to the nibble and back off to smooth air. It has the added benefit of precisely defining that point to an experience player.