This month’s panel for planning is in a 1970s-vintage Piper Warrior with an avionics package straight out of the King Radio heyday. It’s how we used to fly IFR— sporting radio stacks full of analog equipment, including dual KX170B navcomms, a KMA20 audio panel and KR86 ADF.
While it was upgraded once, perhaps in the early 1990s, with a King KLN90 GPS and PS Engineering PM1000 intercom, the KLN90’s CRT (cathode ray tube) is failing and the GPS receiver is slow to acquire. Clearly, the avionics in the airplane don’t owe the new owner a dime. But the busy flight school where the airplane does hard duty as a primary trainer is demanding a modern upgrade. The radios are acting up, with intermittent transmissions that point to a failing KMA20 audio panel. Plus, the school wants to use the airplane as a light IFR trainer.
The primary KX170B has (or had) glideslope capability through the KI214 nav indicator. This relic is unique with a built-in glideslope receiver that now only works on some channels. It would make a good conversation piece on someone’s bar shelf. The second KX170B is VOR/LOC only with the KI208 indicator.
Quick and dirty upgrade
Since budget is a huge consideration, this Piper won’t be getting a big-screen glass makeover with big Garmin or Avidyne navigators. It already has ADS-B Out via the uAvionics skyBeacon wingtip unit. Unfortunately, it still sports the original King KT78 transponder that was determined to have low power output, no thanks to a failing cavity tube. One worthy option is Garmin’s $2610 GTX 325 Mode C digital transponder. It’s solid state, so there’s no worry of a cavity failure. The plane needs a new L-Band transponder antenna, new coax cable and a new altitude encoder. Call it $4500 installed. Let’s get rid of the KMA20 and PM1000 audio components and install a $1500 PS Engineering PM6000B—the world’s lowest-priced combination audio panel/intercom. With new wiring, it should run $3000 installed and offers reliable, good-sounding audio with sizable utility.
Out with both KX170B systems, and since the flight school has Garmin navigators in the rest of the fleet, a good option is the $7900 GNC 355 touchscreen GPS/comm. It doesn’t have a VHF nav receiver, but connected to a $3400 Garmin GI 275 electronic CDI, students can learn how to fly WAAS GPS approaches.
For a secondary backup radio, the flight school had a non-glideslope King KX155 radio that a local shop reworked. The good thing about it is the radio works with the existing KI208 indicator. Pull out the KR86 ADF and its antennas.
Speaking of antennas, both VHF comm antennas are shot. They have cracks in the fiberglass and the skin under the bases is starting to corrode. Might as we’ll replace the old coaxial cable, too. Since there’s lots of disassembly required, it’s a $2800 job, but long overdue.
How much for that?
Compared to a flagship glass upgrade this isn’t huge work, but it isn’t slap and go, either. A good shop should be in and out of it in a week or maybe less. What drives the bottom line up in a hurry is the antenna work, since some of the interior has to come out to access the cabling.
With audio panel, transponder and encoder, Garmin GPS, second navcomm installation, some new circuit breakers, FAR 91.411 and 91.413 IFR inspections and some cleaning up of the old wiring, a $26,000 invoice isn’t out of line. For another $8000 or so, two Garmin G5 electronic flight instruments would be a decent complement to this utilitarian IFR upgrade.
Got a panel that needs some planning? Drop us a line with decent photos and we’ll help noodle it.
