Quote:
Originally Posted by john70t
Simple answer (or probably WAG) from another layman:
Is that "stall" is the lack of airflow....due to low speed or turbulence....over both the airplane wings or props.
The blades can't grab air in a complete vacuum or very high altitudes.
When this happens everything becomes a rock.
With counter-rotating props the front blades act as sort of a turbo for the rear blades.
Instead of being enveloped in nothingness, they now work in a pre-pressurized envelope.
|
I'm calling BS on that one.
If the fronts are sucking vacuum the rears would get prepressurized vacuum just the same, 2x0 is still 0.
But they are something like 10-15% more efficient, but that has nothing to do with vacuum, or high altitudes, it's just inherent efficiency across the performance envelope compared to single prop of similar size and blade design.
And it's offset again by higher weight and maintenance needs due to complexity..
I think the main advantage on that plane shown, cargo, is smaller diameter prop, so better clearance from the ground, safer, and better for dirt strip landings where stuff might be in the bushes, i don't know.
+ VSTOL performance and ability to feather the second prop once airborne and cruising, so better fuel efficiency.
