Stalling in Landing Configuration...?
Moderator
Scifi,
Models are an excellent way to get to learn about flying. However, it is necessary to understand that though the aircraft can be scaled up or down, air cannot. Consider that the propellers on your powered models probably turned at 8000 to 16,000 RPM, where the prop of a Cessna (for example) would turn no more than 2800 RPM. Similarly, the power to weight ratio of models is very different to full sized aircraft.
You might want to do some reading on "Reynolds number", and scaling. When you factor these together, the differences will become more understandable. If you do some reading about the Ercoupe, you'll find that its design tended toward the stall resistant characteristics you speak of with the models.
Models are an excellent way to get to learn about flying. However, it is necessary to understand that though the aircraft can be scaled up or down, air cannot. Consider that the propellers on your powered models probably turned at 8000 to 16,000 RPM, where the prop of a Cessna (for example) would turn no more than 2800 RPM. Similarly, the power to weight ratio of models is very different to full sized aircraft.
You might want to do some reading on "Reynolds number", and scaling. When you factor these together, the differences will become more understandable. If you do some reading about the Ercoupe, you'll find that its design tended toward the stall resistant characteristics you speak of with the models.
Agreeing with DAR, I'd nonetheless also comment that there have been a few aeroplanes at various scales with a continuous Dutch Roll in some modes of flight also. It is seldom very helpful - how big a problem it is varies with class and role.
You might also read up on the phugoid mode. A stall and self recovery is not the only reason for what you're describing as "porpoising".
G
You might also read up on the phugoid mode. A stall and self recovery is not the only reason for what you're describing as "porpoising".
G
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I once tried to suggest to an instructor that (Relatively) the air that a model flies in is denser than around a full size aircraft. The idea was poo pooed, "don't be stupid it's all the same air".
Another instructor described an event where he and another instructor took a T21 to several thousand ft and set up the phugoid stall/self recovery to see how far it would go.
The stall and recovery got progressively steeper until it suddenly bunted and flipped upside down. At which point they pulled to recover and rolled out right side up.
Not as safe an aircraft as was thought!
Another instructor described an event where he and another instructor took a T21 to several thousand ft and set up the phugoid stall/self recovery to see how far it would go.
The stall and recovery got progressively steeper until it suddenly bunted and flipped upside down. At which point they pulled to recover and rolled out right side up.
Not as safe an aircraft as was thought!
Last edited by Crash one; 24th Apr 2018 at 13:10.
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