We often receive email asking for advice on avionics upgrades as they relate to the value of a plane, so we thought we'd address the issue here.

More often that you think, an owner will install a $10,000 GPS in his Wombat WingFury, and assume it adds $10,000 to the value. This is definitely NOT the case, as you'll see.

The value that any one avionics item adds to a plane is dependent on a number of factors, including:

1. Added utility. If the aircraft was previously lacking any IFR approach capability, adding an approach certified GPS certainly increases the utility of the aircraft dramatically. On the other hand, if it was previously equipped with an RNAV, LORAN, dual glideslopes, moving map and radar altimeter, the GPS does not make a huge contribution to the overall utility, and will add slightly less value to the plane.

2. The age of the aircraft is an often overlooked, but significant factor. Adding our $10K GPS to a 1964 Cherokee 140 is (economically) foolish- (it's like building a $400K house in a $100K neighborhood.) It is NOT going to add as much overall value to the plane as if it were installed in a 1993 A-36.

3. The presence of other, similar units also has an effect on the added value, the classic example here being a glideslope. While the first G/S adds much utility, the second is basically just a back up. While the installed cost is virtually identical, the second adds less value. (OK, it's 200 & 1/2, with a crosswind. How much are you willing to pay for the FIRST glideslope? and the second?).

4. Cost/Value. There is a simple, but often forgotten maxim: As soon as you install a NEW Nav/com, GPS, DME, etc. in your panel, you now own a USED Nav/com, GPS, DME, etc.. (It's just like driving that new car off the lot!) While your new one has two distinct advantages over the yellow-tagged item (Age and warranties), it's value is now closer to the used one than new cost.

Several avionics items fall into a different category: Transponders and ELT's. Like mags or vacuum pumps, they are viewed as required equipment that needs replacing when they break. The only thing a potential buyer usually asks about a transponder is "Does it work?". No one really cares about the age, the model, or the cost, and in many years of selling aircraft we never met a buyer who would pay $1 more for a plane with a new transponder. (Of course, they'd pay less for a plane with one that was broken!)

Avionics packages are an important and valuable part of any aircraft value, but the premium does NOT reflect the cost of new units. More realistically, it reflects the average additional premium a buyer is willing to pay for these items previously installed in this year and model aircraft.

Your best bet is to buy the plane with the avionics you like, then do the engine, paint and/or interior if necessary- at least you'll see a much higher return on your investment!