Pilotage

Mark R. Twombly co-owns a Piper Twin Comanche based in Naples, Florida.

"You know, we really need to replace our Trimble GPS," my airplane partner remarked. And why not? Our space-based navigator is at least five years old, which makes it a very senior citizen in the young and restless world of general aviation avionics. Never mind that it's approved for IFR nonprecision approaches — the best a GPS can be today. Or that we do the thoroughly modern thing to keep its extensive IFR database current by downloading updates from Jeppesen's Web site. Or that the aging Trimble has enough features and functions to keep us puzzling over them for the duration of a long cross-country flight. It's what it doesn't have — a color graphic display — that matters. Yes, indeed, we need a new GPS-based flight management system, or better yet, a big-screen multifunction situational awareness display.

The truth is, we don't really need either one. We just think we do, and therefore we do.

Need is an overexposed word in aviation. It's often used in place of the more accurate want because it sounds far more compelling. Need is a tough, no-nonsense term that implies necessary, must have. Want, on the other hand, is soft and self-centered; it implies covet or desire. Our trusty Trimble will get us to our destination and through the approach just as well as the latest big-screen box. We covet the latest and greatest because it simplifies complicated procedures and routings by depicting them graphically, in living color. Plus, a big-screen box looks great, and everyone else is getting one.

The conflict between need and want also is present in every airplane-buying decision, and in most cases want wins. When I sold my Cessna 172, I went looking for a Mooney, the one airplane that I figured best fit my needs. For the same money I ended up in a partnership in a light twin that I really wanted.

The owner of a Cessna 340 has the airplane up for sale. He discovered soon after buying it that the airplane doesn't meet his needs — it doesn't have the legs to fly nonstop to his business destinations. He's looking to replace the 340 with a single-engine turboprop because it has the necessary range, and because he is a student pilot. He wants to sit up front with the pilot in command and fly. In his case, the line between need and want has blurred.

Along with need and want, a third major factor comes into play in aviation buying decisions: Price. Call it the cost-benefit ratio — how much does it cost, and do I need it or want it enough to pay the price?

Last April, my airplane partner and I went to Sun 'n Fun to shop. We started with the premise that we would replace our Trimble GPS and our standby nav/com, a crotchety but functional KX170B, with a new-generation flight management system. It didn't take long to realize that, with avionics, there is no such thing as one-to-one replacement.

Our airplane has a 12-volt electrical system powered by two engine-driven generators. The generators come on line at about 1,300 rpm. When the engines are idling, the battery supplies the electrical juice. It's not ideal for powering a suite of advanced avionics, especially on the ground at night when power-hungry exterior and interior lights are burning. So, we added alternator conversion kits, plus installation costs, to our shopping list.

The wonderful thing about some of the state-of-the-art flight management systems and displays is their all-in-one architecture. In addition to the information database and moving-map functions, they can incorporate communications transceivers; GPS, VOR, and ILS receivers; lightning detection; traffic and terrain advisories; and the latest enhancement, uplinked ground-based weather radar graphics. We need those features, and with the clarity of vision that comes from conviction, we cruise the vendor booths at Sun 'n Fun in search of information and prices.

We learn that our horizontal situation indicator does not have the bootstrap option to drive the heading stabilization on a lightning detector. That means we will have to clear the display every time we change heading when storms are depicted — decidedly low-tech for such an advanced system. The sensible alternative is to buy a new HSI with the bootstrap. Ouch!

We price various terrain and collision avoidance devices, and weather uplink hardware and subscription services. Yeow!

My brother captains a DC-10 configured for cargo, and his flight-plan routes are based on high-altitude airways rather than direct-to navigation. His heavy jet is equipped with VORs only — no GPS, no multifunction display, no collision avoidance device. The FAA has not mandated such equipment for cargo carriers and, apparently, those are luxuries my brother and his fellow pilots can do without. In other words, the cost of buying and installing the equipment doesn't justify the benefits, although I doubt that's the pilots' take on the issue.

We departed Sun 'n Fun with reams of literature and a sea of new knowledge, but no new full-capability flight management system. The grand total for our shopping spree easily equaled half the value of the airplane, throwing the cost-benefit ratio — and our good moods — all out of whack. We returned our rental car to Plant City Municipal Airport, climbed in the airplane, set up the Trimble GPS for direct routing to our destination, and somehow found our way home.