[DJR]

I experience what appeared to be a canopy buffet while performing some aerobatics. The buffet occurred during the bottom of a standard loop.
It was very startling and a complete surprise as I thought the tail was coming off. However, a very experienced pilot in the back seat quickly let me know that he saw the canopy shutter or buffet very rapidly abeam the rear seat.
I pulled thru and ended the maneuver with apx. 3.5 g's which is when the buffet occurred. My theory is that high negative pressure was the cause, but I did the same maneuver several times without getting the buffet.

Anyone else experience such a thing and any thoughts what caused this.

DJR

 

[panhandler1956]

I bet it is your canopy skirt, it flutters against the fuselage side at higher speeds. I put felt along the inside of the skirt starting about the rear seat and going all the way around the back - problem solved.

 

[DJR]

thanks for the reply Brent. Yes, I believe you are correct regarding the skirt. I do have some felt between the skirt and skin, but perhaps I need to look for some gaps here.

Dana

 

[Low Pass]

Clarify for us. This happen instantaeously or over some time?

Only instance where I've experienced anything close to what I'd call a canopy buffet is when I snap or spin the plane. It occurs as the inner wing is stalled. I only do this at low speeds, but I do get a flow separation or some other force that sounds like what you might call a "canopy buffet".

Actually, I think I just figured out what you did. If the event was an instantaneous thump, you flew though your own wake. If it is a buzzing, you have a skirt leakage/sealing issue.

Std disclaimer - if this is new to you, you might want to work though this stuff alone. The -8 is a sweet airplane, but not a robust dual acro machine.

Have fun!

 

[DJR]

Well, it may have been my own wake, but not sure if that would have caused the buffet. The rear canopy skirt actually buffeted slightly on the pullout of a loop. It happened very quickly.

Thanks for the reply.