Airspeed indication error fixed
Posted: Thu Dec 22, 2011 10:51 pm
I have solved the airspeed indicator error on my Thunder Gull JT2 following Mark's advice to install static ports through each side of the fuselage. I made simple, minimal-weight ports from 1/4-inch brass tubing with a brass cover soldered onto the outboard end and drilled for a 1/16-inch opening. Clear tubing slipped onto the inboard portion secures the ports in place. Photos are in my photo gallery.
I think the over-speed indication I was seeing with the original in-cabin static port resulted from a new windshield-wing fairing that I fabricated recently, while the plane was undergoing a series of improvements. It features a larger gap between fairing and wing and probably created a venturi effect that lowered the relative air pressure in the cabin. Photos of old and new fairings, plus wing damage and repair caused by the old fairing also are posted.
Owners of old Gulls might want to take a peek behind their fairings to make sure they don't have an interference problem like I did. The reason I discovered it nearly a year after purchasing the plane was because I removed the wing after an off-airport landing to be able to trailer the plane home.
Dick
That episode also revealed that the left fuselage-wing alignment bracket was broken just above the bolt to the fuselage. It wasn't apparent until the bolt was removed during wing removal and the bracket tab fell into the cockpit. It was an easy welding repair.
My latest work also involved adding a gap cover to the top of the fuselage that covers the open area between the wing and the windshield. It made the plane a little more quiet, and definitely reduced air flow through the cabin.
By the way, I had not flown in four months because of out-of-state work and then airplane modifications when I made my first test flight and discovered how much "faster" my plane was flying. Fortunately, I decided to land it somewhat "faster" than the numbers call for. With that big hole above my head sucking wind out of the cockpit, it sure seemed a lot faster, too. However, the Thunder Gull has got to be the easiest plane ever in which to make a good landing.
I think the over-speed indication I was seeing with the original in-cabin static port resulted from a new windshield-wing fairing that I fabricated recently, while the plane was undergoing a series of improvements. It features a larger gap between fairing and wing and probably created a venturi effect that lowered the relative air pressure in the cabin. Photos of old and new fairings, plus wing damage and repair caused by the old fairing also are posted.
Owners of old Gulls might want to take a peek behind their fairings to make sure they don't have an interference problem like I did. The reason I discovered it nearly a year after purchasing the plane was because I removed the wing after an off-airport landing to be able to trailer the plane home.
Dick
That episode also revealed that the left fuselage-wing alignment bracket was broken just above the bolt to the fuselage. It wasn't apparent until the bolt was removed during wing removal and the bracket tab fell into the cockpit. It was an easy welding repair.
My latest work also involved adding a gap cover to the top of the fuselage that covers the open area between the wing and the windshield. It made the plane a little more quiet, and definitely reduced air flow through the cabin.
By the way, I had not flown in four months because of out-of-state work and then airplane modifications when I made my first test flight and discovered how much "faster" my plane was flying. Fortunately, I decided to land it somewhat "faster" than the numbers call for. With that big hole above my head sucking wind out of the cockpit, it sure seemed a lot faster, too. However, the Thunder Gull has got to be the easiest plane ever in which to make a good landing.