Blade twist
Blade twist
(OP)
thread6-175834: twisting rotorblades
In Ray W. Prouty', VOL 1 Aeordynamics book Pg 248, he talks about blade twist. He says that there is a nonlinear "ideal twist" which in theory will even up induced velocity distribution. This type of twist to a blade is to difficult to produce. So it is common to have a linear twist. You can get the most efficiency from a negative 20 degree twist. But the first 10 to 12 degrees is the greatest gain in efficiency. Blade twist can give you a five percent increase in figure of merit. This is an increase of about 20 percent payload capability. On the UH-60, we have a negative 18 degree twist. You can also gain another 2 to 4 percent inrease in figure of merit by adding anhedral tips.
In Ray W. Prouty', VOL 1 Aeordynamics book Pg 248, he talks about blade twist. He says that there is a nonlinear "ideal twist" which in theory will even up induced velocity distribution. This type of twist to a blade is to difficult to produce. So it is common to have a linear twist. You can get the most efficiency from a negative 20 degree twist. But the first 10 to 12 degrees is the greatest gain in efficiency. Blade twist can give you a five percent increase in figure of merit. This is an increase of about 20 percent payload capability. On the UH-60, we have a negative 18 degree twist. You can also gain another 2 to 4 percent inrease in figure of merit by adding anhedral tips.





RE: Blade twist
See Leishman Principles of... 1st Ed. Figure 3.8.
RE: Blade twist
Some heli manufacturers do pretty crude things to adjust the twist and/or airfoil profile of the blades from root to tip. Perfect is sometimes not as good as "good enough".
- from another SAIT AET grad. (are there too many or not enough of us in the world?)
Steven Fahey, CET