Trust but Verify

terrykohler · #1 04-03-2017, 08:01 AM

Tried to fly on Saturday, after installing my replacement SD card in the GTN650. Turns out I had downloaded the Nav data, but not the base map or safe taxi database to the new card. Seems these reside on the card and are not downloaded into the resident memory of the 650. Need to get with Garmin to get updates to allow me to use my second/replacement card.

In the run-up area, while swapping cards and turning on/ shutting down my electrical system, I happened to switch my EI voltage gage over to Ammeter readout (most times, I leave it switched to read voltage). Suddenly, I?m seeing current draw drop as I?m adding appliances to the load. Back to the hangar, shut down, and run another check just off the battery. Now I?m showing draw decreasing as I start flipping switches to the ?on? position. Blood pressure rising, I decided to head home.

Sunday, back at the airport and with a clearer mind, I switch on the master (negative 5.4 amps), start working my way thru the switches (increasing draw), until I get to pitot heat. When I switch this on, I get a drop in current draw. Switch everything off, start again, same result. Now go to all switches off, then master only on ? again minus 5.4 amps. This seems high to me without anything else on. A check under the panel shows no wires crossed or grounding out. Aha. Climb out of the airplane, reach under the wing and grab the pitot tube. It?s on full boil. WTH?

At that point, I remember that the shop manager had told me that the tech who installed my 650 had broken the pitot switch while sliding underneath the panel, but had replaced it. Flipped the switch up (I haven?t used pitot heat since the radio install), got out my flashlight, and looked at the small numbers embossed on the end. Upside down! Disconnect the pitot terminal, recheck switches, everything now working as supposed to. Turns out all my flights since radio install have been with pitot heat on. Fortunately, I didn?t do the trip last month to Lejeune ? flying over the mountains in weather, I would have turned the switch to the on position and possibly have created some real problems for myself.

Sometime this week, I?ll head out to the airport to flip the pitot breaker switch 180 degrees. Another 20 minute job that?ll probably take 1-2 hours.
After that, I need to make a couple of revisions to my preflight/run-up checklists.

Terry, CFI
RV9A N323TP

airguy · #2 04-03-2017, 08:43 AM

That's a potentially deadly problem, and a good catch. It warrants a "discussion" with the tech at a very minimum to enlighten him.

vic syracuse · #3 04-04-2017, 05:15 AM

I like the dynon and farming pitot tubes with the controller. They have an output signal line denoting that power is applied to the tube. You can either wire it to a light in the cockpit or to one of the discrete signal inputs on most of the manufacturers EFIS's and label it pitot heat.

Vic

terrykohler · #4 04-04-2017, 03:38 PM

Greg:
I sent an email yesterday to the avionic shop that did my radio install. Tech called me today and was concerned and apologetic. Good lesson for all of us.

Vic:
The pitot is out of a Cessna (I think). Going forward, I'll be sticking with the "burn the hand" test on preflight and will be paying more attention to the current draw during preflight and in the air (I've re-acquainted myself with the current needs of each appliance). A warning thru the EFIS sure would be nice though.

Terry, CFI
RV9A N323TP

lr172 · #5 04-04-2017, 10:45 PM

Quote:

Originally Posted by vic syracuse

I like the dynon and farming pitot tubes with the controller. They have an output signal line denoting that power is applied to the tube. You can either wire it to a light in the cockpit or to one of the discrete signal inputs on most of the manufacturers EFIS's and label it pitot heat.

Vic

I believe that the contact is closed when the Pitot heat is off, not on.

Larry