Gretz Static Port on Pitot vs. Vans Static Port Location

[Noah]

My heated Gretz AN-814 pitot tube includes static ports and a static line, in addition to the pitot line. Wondering if anybody else is using this Gretz pitot / static tube, and whether there is any advantage to using the Gretz static output vs. the Vans standard location.

[Kevin Horton]

Aft fuselage static ports are not prone to icing, so there is no technical need to take advantage of the heated static port on the pitot tube. Static ports would ideally be placed in a location where the pressure was the same as the free stream static pressure - i.e. the pressure that existed before the aircraft came along. Wings, by design, cause the pressure to increase below the wing, and decrease above the wing. Thus it is difficult to find a location near the wing that will have the same pressure as the free stream static pressure over the whole flight envelope. The manufacturers that use under-wing pitot-static probes would have conducted a lot of flight testing, with probes in different locations before they found a good location.

I recommend you stick with Van's recommended static port design and location.

[L.Adamson]

Originally Posted by Kevin Horton

Aft fuselage static ports are not prone to icing, so there is no technical need to take advantage of the heated static port on the pitot tube. Static ports would ideally be placed in a location where the pressure was the same as the free stream static pressure - i.e. the pressure that existed before the aircraft came along. Wings, by design, cause the pressure to increase below the wing, and decrease above the wing. Thus it is difficult to find a location near the wing that will have the same pressure as the free stream static pressure over the whole flight envelope. The manufacturers that use under-wing pitot-static probes would have conducted a lot of flight testing, with probes in different locations before they found a good location.

I recommend you stick with Van's recommended static port design and location.

I have, what's now a very expensive heated pitot/static tube along with the Gretz mount. It's about 6" below the wing. It appears that the accuracy is very good. I also have the standard Van's static ports connected to the auto-pilot. They were easier to put in, than running a new static line back through the fuse.

And BTW, at today's prices, I wouldn't even have considered this pitot/static system. But..............it looks kind of cool!

L.Adamson --- RV6A

[Noah]

Thanks guys, with the warmer weather, I'm able to get started on the wing finishing tasks. I never realized that the previous owner of my project had paid all that money for the pitot / static tube until today. The static port in the tube adds like $1100 to the price.
http://www.aircraftspruce.com/pdf/20...l/Cat09401.pdf
I also have the Gretz mount. Larry, did these prices used to be less? Seems exorbitant. Maybe I'll just keep it and use the Vans ports (already plumbed) as an alternate static source. Or do what Larry did and have one drive the autopilot and the other drive the EFIS. One thing's for sure Kevin, with both ports, I will be able to tell if there is a difference!

Or I suppose I could sell this unit & replace it with a pitot (only) tube, but who would buy such an expensive setup? The previous owner had been planning completely redundant pitot / static systems - each wing was set up for a pitot tube. I'll have to chew on this some more.

[L.Adamson]

Originally Posted by Noah

Larry, did these prices used to be less? Seems exorbitant.

That $1900+ model (which I have), was around $300 including the Gretz mount.

Just found my 1996 Aircraft Spruce catalog. AN5814-2 (12V) $179.85

L.Adamson