The Griffon engine caused a number of accidental deaths for Spit pilots. 
There are three factors which induce significant "unconventional" forces 
on a propeller-driven plane that few 'civilians' know about. P-Factor, 
Spiral Propwash, and Torque unwind....

Torque unwind is familiar to most of us, and is why a helicopter 
requires a tail rotor.... but in prop planes it means that, for a 
clockwise turning prop (from the pilot's perspective), the plane will 
want to unwind in an anti-clockwise direction, making the plane want to 
roll to the left. This requires right-aileron to counteract.

P-Factor (pitch factor) is significant when the plane has an attitude 
that is not in line with it's direction of travel. like a plane on the 
ground and during take-off where it's angle of attack is large. (i.e. 
the nose is pointing up while the plane is traveling horizontally). This 
causes the angle-of-attack of the propellor to be different on the 
upward and downward sides of it's turn. A clockwise propeller will be 
going down on the right, and up on the left. Because the right-hand side 
bites in to more air (it's blade pitch is greater) the airspeed and 
forces on the right side of the prop will be greater, the plane will 
tend to turn (yaw) to the left, and will require right-rudder to counteract.

Spiral Propwash is best described with a diagram, but in essence the 
prop imparts a spinning motion to the air. A clockwise turning prop will 
cause the air behind it to have a clockwise twist (in proportion to the 
torque applied to the air by the prop). The twisting air will have an 
equal effect on both wings, and on the stabilizer (because the air 
twists around the fuselage of the plane), and will cause a "rolling 
effect" on those surfaces (pushing up on the left, and down on the right 
surfaces...) (this effect partially negates the torque-unwind). The more 
significant effect is on the tail fin. This is un-balanced because the 
tail extends only upward from the fuse (there is no tail below the 
plane). The effect of the twist is to push the tail to the right, (yaw 
the plane to the left), and this needs to be corrected by applying right 
rudder (like the P-factor).

All of these effects are most pronounced when the plane is at high 
power, and low air-speed ... i.e. at take-off. But, just before the 
wheels leave the ground, the rolling forces are not very effective 
because the wheels *are on the ground*, and pilots have to immediately 
counter the rolling motions when the wheels leave terra-firma. This has 
to be an instinctive correction. The yawing forces will have to be 
corrected on the runway though, to keep straight.

Still, a pilot who has spent many hours flying a spit with a 
counter-clockwise prop (on the merlin engine), will have to un-learn a 
lot of instincts to safely fly the Griffon engine....

A number of pilots learned the hard way.

Rolf

Russell McMahon wrote:
> Supermarine Spitfire pages.
> Superb
>
>
>         http://freespace.virgin.net/john.dell/spithome.htm
>
> All the variants
>
>         http://freespace.virgin.net/john.dell/spits.htm
>
> Located while checking that the MkXIV did indeed have the RR Griffon 
> engine which rotated in the opposite direction to the Merlin.
> It did.
>
> The Griffon engine ultimately developed more than twice the power 
> attained by the Spitfires used in "The Battle of Britain".
>
>
>
>         Russell
>
>
>
>
>
>   


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