multi-engine starup...propeller rotation direction...

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dtvonly

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dtvonly
Hi. just curious about propeller direction of rotation in multi-engine planes.
I saw on youtube that some planes (twin) such as piper seminole with one propeller CW and the other CCW while others (piper cheyenne for example) are both clockwise (viewing from inside the cockpit). Are there standards?
 
There is no real standard. Some light twins do have counter rotating engines to eliminate concerns about the critical engine. But the vast majority of twins do not have CR props.
 
Ultra-simplified version: At high angle of attack, the downward-moving blade of a propeller creates more thrust than the upward-moving blade ("P-Factor"). If the prop turns clockwise, then, the downward-moving blade is on the right.

If you lose an engine, you want thrust from the remaining engine as close to the airplane's centerline as possible. Counter-rotating props (both turning inward) means that the downward-moving blade is on the inner side of both engines - a good thing. But there are relatively few engines that are built in both CW and CCW versions, so most light twins have CW engines on both sides. Thus handling is somewhat more difficult with the right engine alone operating, so the left engine is referred to as the "critical engine".

Trivia - The WW2 P-38 fighter had contra-rotating engines -- both turning "outward". The reason was to rectify airflow problems over parts of the airframe, unique to the P-38's configuration.
 
Nope the P-38 has COUNTER-rotating propellers. They just turn the opposite way they do for most twins. The V-35 rotors do the same as did a handful of German WWII planes.

CONTRA-rotating refers to them being on the same axis. Used in things like the Avro Shackleton or the Fairey Gannet.
 
flyingron said:
Nope the P-38 has COUNTER-rotating propellers. They just turn the opposite way they do for most twins. The V-35 rotors do the same as did a handful of German WWII planes.

CONTRA-rotating refers to them being on the same axis. Used in things like the Avro Shackleton or the Fairey Gannet.
Click to expand...

This is the Fairey Gannet, which has contra-rotating props.

 
Or you can fly an Aerostar 700 (not the 601/602/702), which has two critical engines. Piper spun both engines the wrong way. Don't ask. . . .
 
The wing on the Fairey Gannet illustrates the power of positive desperation.
Not sure I would want to pull any G's while flying that.
Not sure I would want to fly it.
 
Commie Bear intercepted by a Navy Hornet.

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