Like most owners, youve probably upgraded your airplane a little at time. Maybe the interior of your 1978 Skylane isn’t leather but youve at least traded that faded leisure-suit green for a smart looking shade of gray. A couple of years ago, you had that weathered paint bead blasted off and replaced with an almost new Cessna color scheme.
But what about the avionics? Still nursing those circa 1970s radios and that old single-axis autopilot that works most of the time but has a quirky habit of rolling the airplane into a 20-degree bank with little warning? Your shop has chased the bug, replaced a few components but still, the problem persists.
Many owners hang onto old radios for years, putting off replacements and upgrades through several engine overhaul cycles and even a couple of paint jobs and interiors. There’s a good argument to be made for that. After all, some of the mid-1970s avionics-even though soldiering into their third decade of service-work remarkably well. The phrase bulletproof comes to mind.
But nothing is forever and three factors have swayed the equation in favor of upgrade/replacement instead of perpetual repair. For one, its getting harder to find the 20-year-old components some of these radios need and, second, the range of choice in new avionics is far greater than it has ever been.
As a result, prices are intensely competitive for equipment that has more capability than that old Cessna 300 navcom that was state-of-the-art when Jimmy Carter was President.
Last, there’s a major technological shift underway that wasnt present during the last upgrade cycle. The switch to GPS has significant economic implications related to aircraft value. As GPS rapidly becomes the navigation standard, aircraft that don’t have it will be seen as less desirable in the resale market. Were not at the point that an upgrade to GPS will return its full value at resale, but weve long since passed the point that loran and/or rho-theta navigators are considered desirable.
As an avionics shop, were happy to repair most of the old junk that comes our way. But sometimes, you just gotta say enough is enough. Here are some thoughts on the subject:
How Old Is Old?
By todays standards, you can call any radio that doesnt have some kind of digital (LED or LCD) display old. (If you still fly behind a radio that has tubes, send it to the Smithsonian). If you have a comm radio, count the number of channels. Anything having fewer than 720 channels is old and probably unfit for transmitting due to FCC frequency tolerance specifications.
All current-production comm transceivers are equipped with 760 channels. If flight into congested airspace is planned, you’ll need channeling beyond your 720-channel recent vintage navcom. Sure, the radio might work fine but when a controller says contact Center on 133.97, the phrase unable wont wash.
The same holds true for nav radios. Many older navcomms, especially those made by Narco and a few by Bendix/King, have a remotely mounted glideslope receiver. Some of these glideslopes have only 20-channel receive capability. Again, if you find yourself shooting an ILS into busy airports, you’ll need 40-channel glideslope capability.
Even then, 40 channels may come up short. Take for instance the King KI 214 nav indicator, which is usually mated to a King KX 170B navcom, of which thousands are still in service. This indicator has a self-contained 40-channel glideslope receiver as we’ll as VOR/LOC capabilities. But hand it to any seasoned bench tech for troubleshoot/repair and expect a sigh of frustration, or worse.
In the avionics field, this unit is thought of as five pounds of you-know-what in a three-pound bag. Parts for it are obsolete or soon will be and shops don’t like to repair it because they know the fix will be time consuming, expensive and probably short lived. Thats not the stuff of customer satisfaction.
I use this unit as an example only because of its commonality, since it pops up paired to the KX 170 series so often. State-of-the-art 20 years ago, its no longer worth fixing. How about the venerable KX 170B itself? Is it worth fixing and keeping? Five years ago, it was common practice to upgrade to a KX 155 and move a good 170B into the number 2 slot. There must be thousands of such set-ups in the GA fleet.
If you have a 170B that works well, keep it until it dies, then replace it with something new. Repairs on a 170B, while still doable, are getting expensive and time consuming, due to lack of parts. A $400 repair is not at all unusual and when you stop to consider that you can buy a GPS mapcom for $3500 and leap several generations forward at once, nursing an old 170B begins to make very little sense. How about moving it to the number 2 slot? See above. Have your radio shop go through the unit you removed, put it in a box and use it as a spare. If someone offers you $100 for it, take the cash.
The MAC 1700VTX, a $1300 mod that replaces the KX 170Bs mechanical tuning with a digital front end, is still available. Five years ago, it was a reasonable value. But AlliedSignal is clear that parts support for the KX 170 series will end in the not-too-distant future. In the context of relatively inexpensive GPS mapcoms, the MAC conversion makes little sense today, since you’ll spend at least $1300 for the conversion without solving the underlying parts problem. Think about that, too, if youre buying an airplane equipped with MAC-converted 170Bs.
In the navcom field, our short list of not-worth-fixing items include: Narcos Nav 11 and Nav 12 for which needle movements are no longer available. In comms, we wouldnt advise putting more than a pittance into the Narco 11 series comms. The Nav 122 is still supported.
In the Collins Microline line, there are plenty of VHF 251/ VIR 351s perking along. These are excellent radios with digital displays. But these things have been subject to dozens of mods and unless yours has a high mod status, think carefully before paying for expensive repairs.
If youre buying an airplane with Collins gear aboard, check the mod status of these radio. S-Tec still supports the Collins line and, in fact, still makes them. But if the units havent been modded up to date, you could easily spend $1000 getting current. Worth it? Marginal.
The Cessna 300 series navcoms are a tougher call. When they work, theyre not bad radios but many owners seem to have chronic problems. Parts support is still available from Sigma-Tek but even so, the labor to pay for chronic repairs may make it a better idea to replace them with something state-of-the-art. Side-by-side on the ramp, a Cessna with newer radios will have more market appeal than one with Cessna radios.
The definite keepers-for now-are the KX 155 series, the KT 196/197A models and Narcos Mark 12D, which are all current production hardware.
ADF and DME
In the IFR operational arena, ADF is rapidly fading and DME isn’t far behind. The FAA has already approved en route GPS as a substitute for ADF and DME in most circumstances, so the legal requirement for either is all but non-existent.
That doesnt necessarily argue for ripping them out of the panel but it should be cause for pause when repairing these units. Owners of older ADF systems-heck, theyre all old- can easily spend $600 to $800 for routine repairs. And a lot more if the band switches and other major components have to be replaced. This type of repair is common on the very popular Bendix/King KR85/KR86 ADFs. Most owners see this as a waste of money and a good time to make the switch to GPS. Yank the unit like a bad tooth and junk it. Exception: You want ADF and the KR86s self-contained indicator saves you some space.
More modern ADF systems, such as the digital Bendix/King KR 87, might be worth fixing, since theyre still current production-for now-and the small size and built-in timer have definite utility.
The throw away ADFs? The KR 85, Narcos ADF 31A and ADF 140 and the Collins 650. (The 650A is a newer mod and possibly worth repairing.) The old Bendix T12As, Bs and C are scrap. The T12D may be worth keeping but only if the repairs are truly dirt cheap.
DME is more problematical since its more useful than ADF and vintages run across the map. Again, the first measure is digital display; very few mechanical models out there. But if you have one-such as Bendix/Kings 65 series-don’t fix it. Ditto Narcos DME 190 and 195. don’t bother. However, the Narco 890 is current production and worth repairing if you want to keep DME aboard. (Were not sure its necessary, but you may feel differently.) Bendix/Kings KN 64 is also relatively recent vintage and thus worth keeping. Rho-theta RNAVs fit loosely with DME. Sometimes, these are worth keeping if only to provide legal area navigation so that a VFR-only GPS can do the real navigation. Most rho-theta is worth repairing-say the Bendix/King KNS 80/81 or the Collins ANS 351. Narcos NS 801 is rarer and will require factory repairs. A marginal keeper.
The Anti-GPSers
When the government announced the extension of loran-C ground stations until at least 2007, loran owners cheered and GPS makers groaned. Thats because these companies have put loran behind them and want to move forward with GPS. Extending loran doesnt help that cause, although it may help yours. At least for a while.
If you have a working loran that you use for VFR navigation and your navcomms are in good shape, there may be no crying need to replace the loran. On the other hand, if it breaks, there may be no sensible reason to fix it. Fortunately, lorans seem to be more reliable than navcoms or ADF, so keeping one to the bitter end may be advisable. (The bitter end occurred about two years ago…)
The truth is, some owners spend more money in database updates than the loran is worth. The average revision costs almost $200. Thats not so bad for the relatively recent lorans with a replaceable cartridge (KLN 88) or front loading cards.
But some of this technology is so old as to require changing internal EROM chips instead of cards. Since the market is so saturated with used loran systems, you can haggle one for about the cost of one database update. In the event that your box breaks, its probably cheaper to go that route than to try and fix it.
Many loran failures are related to faulty antenna systems. Since these require a pre-amplifier, you can easily spend $200 or more on a used antenna, not counting the labor to troubleshoot and install the new equipment. Somewhere, there’s a point of diminishing returns and my guess is it occurs at about the second $500 repair.
Before fixing a loran, have the shop price out a GPS mapcom, such as the aforementioned Garmin and IIMorrow units. Its quite conceivable that a new mapcom will allow you to yank both the old loran and a navcom and give you more capability with fewer boxes, thus opening up the panel. This is at least worth considering. Used lorans? Theyre out there in the thousands. Good picks are Northstars M1, Bendix/King KLN 88 and IIMorrows Flybuddy. Avoid the older ARNAV units and IIMorrows 600 series. BF Goodrich still supports the old Foster line but Id never consider buying and installing one used and be very cautious about expensive factory repairs.
Transponders
In most areas of the country, the transponder and its related systems are crucial pieces of avionics. In other words, you gotta have one and its gotta work. Transponders, being high-power, high-heat devices, are failure prone. But theyre also not that expensive to replace. Its reasonable to spend up to $500 to repair to a transponder. Once. If the thing needs another few hundred dollars later, consider a replacement. The Garmin GTX 320, for example, costs $1495 new and is solid state.
To most pilots, a transponder is a transponder. However, with the advent of surface mount technology, modern designs eliminate the expensive-to-replace, heat-producing cavity tube. Some new transponders even help to reduce pilot workload with features such as automatic VFR squawk (usually found on units with LED displays). When replacing the transponder, seriously consider replacing the blind encoder if its five or more years old.
Most newer encoders have instant on operation, eliminating the average five to 10-minute warm up period. (Ask your shop for a recommendation.) Its also advisable to have your shop evaluate the encoder while installing IFR GPS, since this installation will require encoder interface. Consider replacing the transponder antenna, too, since old ones are similarly failure prone.
Autopilot Woes
In high-performance airplanes flown in serious IFR, autopilots are critical systems. Most owners wont consider flying without them. Autopilot systems are complex and so is troubleshooting them. Most shops charge a higher hourly rate for autopilot work due to costs of test equipment and specialized training.
Because of the expense, replacing an autopilot is not something most owners will consider except in some cases, such as a major upgrade of an airplane the owner plans to keep. Another case might be a cranky Cessna 300 series Navomatic autopilot, which can get into big bucks if major or chronic work is required.
Similarly, an older wing leveler with nav tracking might not be worth repairing, especially if you consider that a new S-Tec system can be installed for under $10,000.
The Autocontrol systems found in Pipers are essentially Century systems and are generally worth repairing, since parts are widely available. The same applies to Bendix/King autopilots, which tend to dominate the high performance market. Even if expensive servos have to be replaced, repairs are economical.
Be leery of a shop that suggests complete replacement of an autopilot system, unless the system is ancient and it will be obvious when it is. Although there are new systems designed to reduce panel space and provide advanced features, replacement is not necessary very often. If you have a basic wing leveler (single axis), S-Tec makes add ons to provide altitude hold.
Many autopilot problems are the result of gyro failures and proper troubleshooting techniques will verify this. Aside from replacement of gyros, there isn’t much required routine maintenance, other than proper use of the system.
Instruments
Flight instruments are usually ignored during an avionics retrofit. As mentioned above, proper operation of the attitude, heading or rate gyros are the key to autopilot function. Pro-active gyro replacement should be considered. As for repairing older flight instruments of any kind, caution is advised. Weve found that spot repairs on instruments with lots of time on them is rarely cost effective.
If the repair will be $250 and an overhauled unit $400, go with the overhaul and enjoy the protection of at least a short warranty. At the least, get a good hack on both repair and replacement costs before deciding.
Be wary of the aerosol overhaul where the gyro comes out of overhaul looking new after fresh paint on the case and clean glass but the crucial components inside werent replaced. Unless youre dealing with a known reputable overhaul facility, ask your shop to follow up and get a teardown report on the overhaul. Theyll know what to look for.
Most of the popular instrument repair facilities have a healthy supply of zero-time overhauled units available for exchange. This eliminates down time while awaiting overhaul.
Conclusion
Were not implying that all older equipment should be scrapped for new. Its natural to be suspicious of a shop that seems to automatically recommend replacement instead of repair.
But given the aging of the fleet and the dizzying choice in new gear, watch for an escalating trend favoring replacement over repair. Just because it was economical to repair 10 years ago, doesnt mean the same equation still applies today.
If youre uncomfortable trusting your shops recommendations, there’s nothing wrong with getting a second opinion or even a third. Most reputable shops are happy to fax proposals.
You can sense if a units age and the practicality of repair raise the alarm at your shop. If you at least have a good sense of the price of replacement equipment, you can assess the cost-value relationship in your own terms and order the repair or not.
Also With This Article
Click here to view the Repair Checklist.
Click here to view “Good Deals on Used Gear; Better on the Way.”
-by Larry Anglisano
Larry Anglisano works at Exxel Avionics in Hartford, Connecticut.
