Questair digital OAT gauge

Picture Key:

[ gauge face down w/ fairing ] [gauge face]

[Scott gauge face][Scott gauge stem]

[Questair inside][Questair outside]

The Questair OAT is a digital gauge intended to replace the aging stem-style gauges that have a sensor that sticks out of a hole either in the windshield or pilot's window. I have a Scott gauge and it has clouded over and has also caused cracks in my pilot-side window so I looked into OAT alternatives and decided to go with the Questair. Additionally, the stem sticking out is large and detracts from the smooth lines of my plane. I doubt removal of it will have any effect on my airspeed--heck, my biggest problem is slowing her down!

One of the issues posted on a number of forums is the way Questair operates. One guy opined that:

The older gentleman who sells them is his own worst enemy from a marketing point of view, since he has no website, no email address and I have never successfully had him answer the phone. You have two options for ordering, either leaving a voicemail or sending a fax with your shipping address and credit card information, but he does return calls. He goes on vacation from time to time, and if you order while he's on vacation, it sits until he gets back.

I was visiting with my daughter in Florida when I called Questair to ask about the device and to place my order. I got the voicemail and left my name and number. Later, I discovered that my phone had a voicemail and it was Fred Kantor, owner of Questair Inc. He left a message and that was the last time I ever heard from him. I called back numerous times, left messages, etc., but no response. Fred is apparently an internal medicine physician, so he is probably busy most of the time and does this digital OAT gauge thing on the side.

So, I FAX'd my order in and in less than a week I had my unit--see pictures above. I could immediately see why some guys have had issues (I am an engineer after all). It is somewhat cheap plastic as aerospace equipment normally goes--but remember, if Mooney made this thing it would cost 1.5 AMU's instead of 0.08. The thermistor appears to be protected by a chromed or stainless bubble and the threaded shaft is a continuation of the case plastic. This latter part is the source of most of the problems others have had. If you tighten too much it is pretty clear to me that it will break, that much is obvious. The fairing that goes on the outside is of a tougher plastic, but the threads are very shallow. There is a foam washer the same ovoid shape as the fairing and what you want to do is use that washer to take the compression strain. The unknown is the thickness of the plastic window that you are mounting it to. There are extra washers and the key is to get the number of washers needed correct so that the shaft and fairing are not over tightened.

After installing it, I found it to be about a half degree off from the ATIS/AWOS temperature at the airport--so well within tolerance considering I was in my hangar. I like it because it replaces the problematic, difficult to read stem gauge and it automatically converts from degrees C to F for you with the push of a button. It also has an internal lamp, again accessed by a button. There are two batteries in the unit with a switch to select between the two--just like your fuel tanks in a Mooney. So, if the gauge fails to display, you turn the switch to give it a fresh battery. What's not to love?

Prop check

Yesterday I flew 76Q up to Fort Worth's Meacham Field, AKA Forth Worth Meacham International AKA KFTW from Beaumont (KBPT). I went up there to have my propeller checked in accordance with AD (Airworthiness Directive) 2009-22-03. The AD is an order from the FAA that must be complied with in order for a plane; i.e., one that falls under the AD, to remain airworthy. Not all Mooney's have this kind of propeller and those that don't will use that fact as a selling point.

The AD says that if you have a Hartzell propeller model in the ()HC-()2Y()-() series, then you need to have it's hub inspected by a mechanic who is certified to use an eddy current instrument to see if you have any subsurface cracks--the test is called an Eddy Current Inspection (ECI) and has to be done after every 100 hours of flying. It used to be that or every year, whichever came first. This recent AD relaxed the requirement by dropping the "every year" to accommodate the hangar queens that don't get flown much.

The prop hub is the part that holds the blades. On a fixed blade propeller, it is just the circular center section with the holes in it to mount it to the engine. On a constant speed prop, like 76Q has, the hub is a complicated unit that the two blades, which rotate on an axis perpendicular to the propeller axle, are mounted to. The hub must withstand significant forces and so is a potential failure point.

The image to the left shows the mechanic doing the ECI on my plane. He is holding the instrument probe in his right hand and touching it to various places on the hub. To get at the hub, he had to remove the spinner. His left hand is resting on one of the propeller blades.

The hub was fine and I learned a good deal from the A&P who did the check about hubs and propellers. Apparently, only two of these particular hubs have ever failed, both offshore, I believe he said the UK, and under questionable circumstance; i.e., other factors may have caused the crashes. He said he has never seen a cracked hub in all of the ECI's he has done. His instrument has been well used and I noted that it is just an X-Y o'scope with a signal generator.

Every time an AD is issued on a GA aircraft it is generally accompanied by an uproar, the magnitude of which is proportional to the costs involved in complying with the AD. This inspection is no different and the new change will be viewed with great relief by many owners of airplanes since they will no longer have to have this check done yearly. A plane can go for years without this inspection as long as it isn't flown--but then you have to ask, why own a plane?

As to the flight, it was easy. I flew direct to DARTZ, an enroute fix along VFR flyway V239. I chose DARTZ because it was well clear of the DFW Class B airspace. It was a good thing that I flew there first because ATC was specific in telling me to stay clear of the class bravo. I thought that was a bit rude, but it turns out that the FAA is very cautious about letting VFR flights into Class B airspace. When I left FTW, they cleared me into the bravo immediately and I flew away through it. My guess is that if you are leaving, then you are a lesser threat.

Some pilots avoid a Class B like the plague. I personally think it is sort of neat to be listening to the radio and hearing Continental two-zero-five-one climb to flight level three-two-zero or Southwest one-zero-seven turn left heading zero-two-four. You know you are flying with the big boys (girls too!) when you hear those sorts of things on the frequency you have been assigned. When I hear Mooney five-niner-seven-six-quebec I know that the jet jockeys are hearing it too and wishing they were buzzing around in a sports car instead of steering an (air) bus around full of passengers.

It took me three hours to fly up and one to fly back. I took my time going up, had a bit of turbulence and headwind as well as the indirect route via DARTZ. On the way back, I flew a direct return course with a tail wind and let all the stops out. My Garmin clocked me at 212 MPH max ground speed. This is essentially why guys fly Mooneys. For the amount of money invested, you cannot buy a faster plane, period. In fact, the plane is so slippery that it is hard to slow down.