P40 yaw trim

[Muff_Huggar]

I've been working with voiceattack since I fly in VR and noticed something tonight. The P40E seems to have a default yaw trim of -62%. I don't have yaw assist on, and whether I start on the ground or in the air, it's the same. If I press the Reset Trim button, I can see the yaw trim count down from -62% to 0. The pitch and roll trims start at 0. Is this expected?

[Barnacles]

Yes, aircraft are trimmed for cruise by default. Trimmers start at a particular value for each aircraft eg. for a 109 its stabilizer is set to -84% by default or something like that. The -62% is the default yaw trim for the p40

[Muff_Huggar]

Those numbers seem pretty significant. Am I correct to assume that once in combat (or before dive bombing, for example) that an experienced pilot would set all the trims to zero?

[HandyNasty]

5 hours ago, Muff_Huggar said:

Those numbers seem pretty significant. Am I correct to assume that once in combat (or before dive bombing, for example) that an experienced pilot would set all the trims to zero?

The simplest option (not the best) is to leave them as they are when you're in combat. Most plane don't necessarily benefit much from changing yaw trim in combat (pitch trim is more useful in my opinion), and it adds workload. 

Also, when you set yaw trim at 0% fo the P40, you set yaw for a "low speed high throttle & pitch" settings if I recall right. This is not always the case in combat. If you'd happen to dive away and reach high speeds, you'd not be coordinated

 

If you really want to go into yaw trimmers, I'd suggest you to remember what yaw trimmer settings make your plane fly coordinated (ball in the center) under specific flight conditions. I say 'remember' because that's easier than to look at ball in combat situations. : 

"P-40 needs ...% yaw trim when climbing at 150mph; 3000rpm; 42 inches boost. Then ball is in center". 

"P-40 needs ...% yaw trim when diving at 400mph; 3000rpm; 50 inches boost. Then ball is in center". 

"P-40 needs ...% yaw trim when diving at 400mph; 2600rpm; 0 inches boost. Then ball is in center". 

 and so on and so forth. 

 

 

[Herne]

I just trim ball to center in cruise, and once combat starts use coordinated rudder and stick, pushing a bit of right rudder when climbing, and a bit of left when diving. I try to have a quick glance at the ball now and again to make sure I'm not too far off,  bleeding energy

 

Edited November 26, 2018 by =11=Herne

[69th_chuter]

Of course, the two major factors at play here are spinning propeller slipstream which varies considerably and pushes the nose generally left and the fin's offset 1.5° to the left* to, generally, counter this and its effect will vary with conditions.  It's all rather imprecise but worked rather well in the overall scheme of things.

 

 

*Throttle off in a bombing dive (for instance) the nose will swing way to the right because of the offset fin requiring considerable left rudder input to keep the nose straight.  This led to the joke that one could ID a P-40 pilot by his overdeveloped left leg.  Other American aircraft had offset fins as well.