Loss of airspeed

[330drvr]

Lost my airspeed today inflight. Was IMC with Tampa Approach. Asked for a vector out towards the Gulf where I knew I could get VMC quickly. Landed safely back at home base. Not real happy however. Postflight inspection reveals that the Gretz heated pitot tube apparently melted, even though it was not turned on! Can this happen? Searching the forum makes be understand that this is possible. I don't know whether or not to start over with a fresh Gretz (ease of install) or switch to Falcon or Dynon. Anyone else experience this?

[noelf]

...even though it was not turned on???

What Mach number were you flying??

[Vern]

I have one each Gretz and Dynon. Both have worked great. The Dynon heated has a control box that supplies moderated heat as needed.

Please describe the damage you suffered.

[330drvr]

Vern:

The pitot looked like a narrow pencil eraser sticking out of the front tube. I pulled the "plug" out and it looks like it broke off other material inside the tube. The pitot heat was NOT turned on during the inital airspeed failure. I did turn the heat on after the initial failure hoping that might restore the airspeed indication. I suppose I could be having a problem with the AHRS, but think it unlikely to suffer two mechanical failures at the same time. I am surmising that the power to the pitot heat control card is always on and the pitot on/off switch functions more as a control relay. Otherwise I can't explain the failure mode.

Bruce Brock
RV-7A
Gretz heated pitot
GRT EFIS

[Wayne Gillispie]

from Spruce. After researching Gretz in April, I found out that there were a couple of others that melted also. I did not want a control board deciding when to send power to a plastic pitot. I occasionally have thermistor/board failures on hvac equipment but not nearly as critical. Falcon pitot heats up in about 30 seconds and draws 7.7 amps(14 ga). I am glad you made it down safely.

[Bavafa]

I have the Dynon pitot heated tube and for whatever it is worth, I have used it a half a dozen time so far last winter with no issues.

Glad you made it down to saftly with no issues.

[rleffler]

Bruce,

I'm curious as to the vintage of your Gretz pitot? Is it pre or post Angus Aviation buying the business?

bob

[330drvr]

Bob:
The aircraft was finished in Nov 07 (not by me). The pitot I believe was purchased from the original source. Mike had a problem with the unit in early 09 and dealt successfully with Angus. For those of you following this thread, I have determined that no power was out to the unit during my first loss of airspeed. After I turned the pitot heat on was when power is applied to the tube and melted the interior. In fact testing this morning in 90 degree heat, the pitot heat was in fact being applied. The sensor is not withholding the power as it was designed.

I still don't know what caused the original airspeed failure. More testing on the adjenda tomorrow.

[LifeofReiley]

After installing a heated pitot tube (Piper Blade Type) and flying for 1 1/2 years, I kick myself for installing a heated pitot in the first place...