Airspeed indication error fixed

[dickoreilly]

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.

[rileywinglowe]

Thanks for the report, Richard. The static ports you made look good, but an easier method is to install an extra-long 3/16ths pop rivet, punch out the mandrel, and push the plastic tube over it on the inside. Standard method on Van's RV's.

Do all the 2-place Gulls have those brackets attaching the leading edge to the fuselage? My J model does not have them.

Riley

[blaswichk]

How close is your airspeed now? I am going to redo my static ports, as I still have an error of about 9-10 mph according to the 4 sided ground track. I still can feel a little air coming in around the nose wheel fork area, and at least mine has got some kind of pan around it that turns with the fork and keeps most of the blast out. My friend Sal's 'J' has got a huge gap around the fork, and no closure at the window to fuselage that should at least have a rubber gasket like garage door seal. His airspeed is unported also, and who knows what his error is, although it doesn't bother him flying the plane.

kb

[rileywinglowe]

Kess, does your 2000 or your friend's J have those brackets attaching the wing leading edge to the fuselage like Richard's?

Riley

[dickoreilly]

Airspeed looks very close compared with GPS, but I need to do better testing and
record the values. I'll post my results.

My nose gear opening has no cover, but covering the roof of the fuselage
really minimized airflow.
 Dick O'Reilly

[blaswichk]

The only brackets that I know of on my 2000 are the 4 main tabs that bold to the top of the fuselage frame. There may be a couple of tabs connecting the eyebrow to the wing leading edge (at the top of the front windsheild), but I don't know of any others.

[rileywinglowe]

Thanks, Kess. I was referring to the photos that Dick O'Reilly posted Dec 22nd, one of which I attached below. I guess they are more like tabs, like you said. Mine doesn't have them, and I was unaware of them on any Gulls. I was just wondering which models had them, or if they had been discontinued.

Merry Christmas to all.

[mike_cummings2003]

Hi guys, yes the G2K do have the "D" cell brackets

--
Fly to live
Live to fly

[rileywinglowe]

Thanks, Mike.

Riley

[mike_cummings2003]

welcome and Merry Christmas

--
Fly to live
Live to fly