Letters from Readers: December 2016

LED Lighting Approval

I want to replace the taxi lights on my Piper Malibu with LED equivalents. This seems to be quite the grey area. My airplane came from the factory with the Whelen A775 series recognition/taxi lights. There is no TSO or PMA for these units because Piper approves the installation under the original type design. Whelen recently introduced the 71888 series, which are fit, form and functional equivalents to the original A775. It would be a simple installation because I could literally just drop them in place of the old lights. The problem is that these aren’t TSO’d and Whelen apparently has no intention of getting a TSO for them because there is no TSO for recognition/taxi lights. So how do you go about legally installing them? Getting a one-time field approval would be the only way, but how do you do that with so little technical data to justify it to the FSDO?

aircraft LED lights

Greg Wroclawski
via email

You’re doing the right thing by trying to install these lights legally. The outcome is really in the hands of the installer. If it determines that dropping these lights in place of the existing ones is a minor modification, a signed logbook entry will suffice. If not, it’s time to solicit a field approval. This might not be as difficult as you think if the installer follows the FAA’s field approval checklist. The inspector will likely want to see proof that the new light draws equal or less current than the old one and that there are no structural considerations. If you can find previously approved data, like a Form 337 signed by the FAA, it should be easy.

Slide-In ADS-B

I have a Garmin GTX327 transponder in my Van’s RV-7A. In the ADS-B transponder article in the November 2016 issue of Aviation Consumer, you wished that Avidyne’s AXP340 ADS-B Out transponder was compatible with Garmin’s GTX327 transponder wiring because it would be convenient to slide the AXP340 in its place. I have a broader question.

Why hasn’t any other manufacturer come out with a compliant ADS-B Out transponder that is a slide-in replacement for the popular GTX327? Ideally, there would be an option to wire in a GPS signal from an appropriate unit, including a GNS430W, to name one approved position source.

For those with the popular Garmin GTX330 Mode S transponder, the now discontinued GTX330ES provided an easy path to ADS-B compliance, but that’s not the case with a GTX327. Garmin could have done this with the current GTX345 series ADS-B transponder, despite it being the same height and width as the GTX327, but it didn’t. That creates additional expense and effort for owners like me.

I’m convinced there’s a significant market waiting for someone to fill this large niche. Am I missing something?

John Goldsmith
Livermore, California

The Garmin GTX345 wouldn’t fit in the GTX327 mounting tray because it has a deeper chassis, which was also the case with the older GTX330.

Shops we spoke with noted that repinning the new connector to accommodate the GTX345 (or any other current rack-mounted ADS-B transponder) can generally be accomplished in a couple of hours or less, if the wiring is in good condition.

Weighing In on the Beech Sierra

I’m writing to tell you how much I enjoyed the Beech Sierra article in your recent (November 2016) Used Aircraft Guide. It presented the Sierra in a good light.

However, there were some inaccuracies. The gross takeoff weight never increased, but the empty weight did increase during model progression. My airplane is probably typical for a B24C and has an empty weight of around 1820 pounds and has a full fuel payload of around 605 pounds.

The early Sierra models (A24-R) were really the fastest. The POH quotes 140 knots true at altitude, albeit at over 12 GPH. It was typically the lightest Sierra and has the longest propeller. As you noted, the C24R is the end of the line and was really the best to own. As a Sierra owner and A&P, I have done a few minor aerodynamic cleanups. I typically see 140 knots true on roughly 9 GPH.

At the Beech Aero Club, we really try to help our membership. I will probably sell my Sierra in the near future, but will probably always be a club member.

Marty Vanover
Technical Director, Beech Aero Club

More Maintenance Articles

I was saddened when I heard that your sister publication Light Plane Maintenance is being suspended. Aviation Consumer is my other favorite magazine and hope that more maintenance articles will appear in it.

Carl Carlson
via email

We plan to do just that, Carl. If there are specific topics that LPM readers want us to cover, tell us and we’ll do our best.