P-Hudson
Member
Hi all,
I'd like some opinions on the following:
A Light Sport Aircraft has a maximum speed of "138 MPH at max continuous rated HP". Does that preclude using a prop design that requires a reduced throttle setting to not exceed redline at 138 MPH; That is, a "climb prop"?
A part 23 aircraft can use a climb prop as long as it meets the following criteria: The prop must limit the engine RPM to below redline during climb speed defined as 1.2 x Vs1; and it must not overspeed the engine (110% redline) at idle in a dive at Vd. That prop would require reduced throttle to prevent overspeed in level flight.
If I design a prop for best climb with a fairly powerful engine and clean airframe, it too will need a reduced throttle setting at 138 MPH in level flight to prevent overspeed, but then the engine is not at max power, though that would be as fast as it could go.
Ideally, I'd design for my desired cruise condition and reduced throttle setting in order to reduce fuel consumption; that too may require reduced throttle at 138 MPH.
It seems odd to have to design a prop for max speed on an LSA just to show that the speed is slow enough to comply with the rule. Or worse, to have to use a lower powered engine optimized for top speed, all at the expense of climb rate.
B.T.W.
This is my first post but I've been lurking for a while. It's nice to see a forum that thinks one-off designs by individuals is reasonable just because we want to. Even more so when most of the regulars appear to have the talent!
-Peter-
I'd like some opinions on the following:
A Light Sport Aircraft has a maximum speed of "138 MPH at max continuous rated HP". Does that preclude using a prop design that requires a reduced throttle setting to not exceed redline at 138 MPH; That is, a "climb prop"?
A part 23 aircraft can use a climb prop as long as it meets the following criteria: The prop must limit the engine RPM to below redline during climb speed defined as 1.2 x Vs1; and it must not overspeed the engine (110% redline) at idle in a dive at Vd. That prop would require reduced throttle to prevent overspeed in level flight.
If I design a prop for best climb with a fairly powerful engine and clean airframe, it too will need a reduced throttle setting at 138 MPH in level flight to prevent overspeed, but then the engine is not at max power, though that would be as fast as it could go.
Ideally, I'd design for my desired cruise condition and reduced throttle setting in order to reduce fuel consumption; that too may require reduced throttle at 138 MPH.
It seems odd to have to design a prop for max speed on an LSA just to show that the speed is slow enough to comply with the rule. Or worse, to have to use a lower powered engine optimized for top speed, all at the expense of climb rate.
B.T.W.
This is my first post but I've been lurking for a while. It's nice to see a forum that thinks one-off designs by individuals is reasonable just because we want to. Even more so when most of the regulars appear to have the talent!
-Peter-
