[ARC5] copies

[Kenneth G. Gordon]

On 17 Aug 2012 at 19:52, Alan Morriss wrote:

> Incidentally , everyone I know who heard zeros says the same
> thing about the engine note. i would imagine it was due to the design
> of the exhaust system .alan G4GEN

The Zero had very short exhaust stacks surrounding the cowl. They were 
designed specifically to provide some "thrust". 

Later in WWII, some Allied radial-engined planes were also designed the 
same way.

This is what gives the Zero its distinctive sound.

BTW, there is a youtube video of one of the very few restored Zeros which 
still has an original Sakae engine. The videos shows the engine being 
started, run up, and the plane taxiing and flying. It does most definitely have 
a very distinctive sound.

On a slightly different note, the P-51's cooling system was also designed to 
provide some positive thrust. This compensated for the air-drag loss caused 
by the radiator system of almost all other water-cooled aircraft of the time 
which didn't have such compensation. The P-51's cooling system design and 
implementation resulted in essentially zero effect on airspeed, rather than a 
loss. At some power-settings, it actually reduced fuel-usage and increased 
engine efficiency.

Ken W7EKB