Winglets

[JGug1]

Regarding an STC for using the Aviation Enterprises winglets on a 336, the test bed for AE's modifications was, in fact, a 336. I saw it in Tennessee when I was there a number of years ago. I would think that if he work for obtaining STC was done on a 336 that the STC would be legal for that airplane.
JGug

[hharney]

In the last issue of Aircraft Owner there is a nice ad from Owen and Aviation Enterprises. I states in the ad that the winglets gain 10-20 mph. Is this true? How can adding these winglets increase the speed that much? I guess I am not really up to speed (no pun) on these winglets anyway. I see them on lots of aircraft but i am not really sure what the real true advantages are, with the winglets. Maybe someone can explain how a skymaster can increase speed that much. I am ready to sign up if I can get 20 mph.

[rhurt]

My '66 has winglets. They are STC'd for 336s also.

The winglets reduce the wingtip vortices, thereby increasing lift and aileron effectiveness. The increased lift translates to better climb (100-200 fpm) and less induced drag (lower angle of attack for the same airspeed). You can feel the effectiveness most at approach and landing. 90 mph approach speeds feel comfortable, and you have to get all the power off on landing or you'll float forever.

They are most effective at Vy indicated airspeed, so they increase cruise speed more at higher altitudes where indicated airspeed is closer to Vy.

They save fuel. And engine wear. Since you go faster or climb faster for the same power setting, your trip is shortened and your engines are running for a shorter period of time.

Owen says they work, but the real proof is that Southwest has added them to all their planes. Southwest would not have paid the money to buy winglets if they didn't pay for themselves.

Randy Hurt

[tropical]

Originally Posted by rhurt

My '66 has winglets. They are STC'd for 336s also.

The winglets reduce the wingtip vortices, thereby increasing lift and aileron effectiveness. The increased lift translates to better climb (100-200 fpm) and less induced drag (lower angle of attack for the same airspeed). You can feel the effectiveness most at approach and landing. 90 mph approach speeds feel comfortable, and you have to get all the power off on landing or you'll float forever.

They are most effective at Vy indicated airspeed, so they increase cruise speed more at higher altitudes where indicated airspeed is closer to Vy.

They save fuel. And engine wear. Since you go faster or climb faster for the same power setting, your trip is shortened and your engines are running for a shorter period of time.

Owen says they work, but the real proof is that Southwest has added them to all their planes. Southwest would not have paid the money to buy winglets if they didn't pay for themselves.

Randy Hurt

I have flown jets with the winglets, and part of what you say is true. The effect of the winglets on a straight wing aircraft will be in the low speed regime.

But in the 337, I highly doubt a speed increase of 10-20 mph. I would say it's negligible.

[rhurt]

My '66 had winglets, a pod, extended front exhaust pipes, and an air condintioning condenser scoop installed before I bought into it, so I cannot give quantitative before/after comparisons.

Compared to my dad's '68 with fresher engines, I get about 5 mph more tas at 8,000', 2500 rpm, and full throttles. Even with the pod, pipes and scoop. Both aircraft have JPI digital tachs.

Randy Hurt