November 2005- Our charter company operated a 1970 model PA-31-310 Navajo for several years. We purchased it out in California, took the insurance-required flight training and flew it home to Florida, making a stop in Vegas for the night, and another at the Grand Canyon, just to sightsee.
After the 15-hour ride home we thought we knew her pretty well. Six months later we had put about 75 hours on the old girl and had grown to know her even better.
Our airplane was basically stock with the exception of some better radios, and a JB electric air conditioning unit. When we reweighed the aircraft (required by Part 135) we were pleased to see the aircraft had lost a few pounds, pushing the useful load up to 2,098 pounds.
With four fuel tanks—two mains and two aux tanks—the aircraft carries a total of 190 gallons. This combination of high fuel capacity and high useful load yielded tremendous flexibility in loading the aircraft.
With full main tanks, which will yield two hours of flying plus reserves, we could carry five 250-pound passengers plus myself. With full fuel tanks, which represents nearly 1,400 miles of range, I can still carry more than 900 pounds of people and stuff. By General Aviation standards, that is huge!
I will mention that you need to watch the weight and balance carefully because you can go out of the front of the envelope when loading the Navajo, and this becomes more critical at higher weights as the CG range gets smaller.
The Navajo does an honest 185 knots true below 10,000 feet at 68 percent power. Go higher and you will go faster. At 14,000 you will see 196 knots true. I ran the plane at 32 inches manifold pressure and 2,200 rpm all the time. At that power setting, I am burning 36 to 38 gph.
The big Lycoming TSIO-540s that power the Navajo feature a really nice, user-friendly (as far as turbocharged piston engines go) turbo installation. The wastegates are automatic, which in theory means you shouldn’t be able to overboost the engine, but the large single turbo does bootstrap, so smooth is the order of the day when it comes to the manipulation of the throttle.
The same holds true for power reductions. I pull off two inches of manifold pressure at a time, wait about 60 seconds, pull off another two inches, and so on. This technique does require some decent planning, if you intend to get down into the pattern with a power setting somewhere around 20 inches of manifold and 2,200 rpm.
Our Navajo didn’t have a propeller syncophaser on the props and quite honestly, really didn’t need one. The three-blade Hartzells are smooth running, with no caution or yellow arcs throughout its operating range, and they made for a fairly quite cabin. Our passengers would routinely ride without headsets, even though they were available.
For an aircraft of its vintage and class (late 1960s technology, General Aviation) it has a lot of nice features. A heated electric pilot side window, electrically heated props (as opposed to alcohol), and full de-ice boots give it known ice capability. Though I like to point out that known ice operations in any piston airplane is a bad idea, the basic anti-ice system on the Navajo is as good as it gets.
The air stair door gives the Navajo that big airplane feel, and the large, double pane windows let the light in and keep some of the noise out. Our ship featured complete copilot side instruments, and a rather vintage but functional AVQ-47 radar, which worked well, once you learned the black art of how to use it.
It also featured an original Piper Auto-Flight IIIC autopilot. Essentially a Century IIIC, this electromechanical dinosaur is no match for a King KFC 150 but again, once you learn how to use it, it really worked pretty well. It fully coupled to the localizer and glideslope, and our IFR approved GPS as well.
The flight characteristics of the aircraft are typical Piper. Stable as a table in pitch and roll, with the slightest hint of yaw in turbulence. This combination makes for a really nice instrument platform and the Navajo is an easy ship in which to fly instruments.
Maintenance, for the most part, was pretty easy as well. The plane uses Piper engineering to solve complex problems so it is fairly simple to understand, and we experienced no parts availability problems. At 27 hours after the annual, we did an oil change and some preventive maintenance and the only squawk we could muster was a broken alternate air door spring on one engine.
So while you may have heard the Navajo is a maintenance hog (hence the nickname “Never-Go”), that had not been our experience. That is not to say that all maintenance on the plane is a joy.
Bleeding the brakes, for example, is a multi-man, multi-day task that will trash your hangar floor and try your patience. The turbo wastegates require lubrication (we use Mouse Milk), on a regular basis.
The oil coolers are lower than the oil sump drain plugs so to do an oil change right, you need to loosen the B-nut at the oil cooler outlet line and drain the quart or so of old oil out of the oil cooler. Our airplane had a 12 volt electrical system with the battery buried up in the nose, just aft of the radar dish. Servicing that battery was a treat.
There are several expensive ADs out on the PA-31 series. Most importantly is a series of ADs on the tail. These are major deals, with compliance costs around $10,000. With its “almost all-weather” capability, relatively easy handling, cabin-class ride, good speed, large cabin and high useful load, it is not a surprise that the Navajo is the piston air charter business darling.
The early models, like the one we had, in really nice shape, can be bought for well under $200,000. The later models of the 310 hp version and the Chieftain, which has larger engines and another seat, plus a double-wide cargo door, wing lockers and in some cases an auxiliary pilot door, can run $350,000 for a nice airplane up to $600,000 for a pristine, super low-time, new paint, interior and avionics example.
When you look at what the pricing on some high-end singles are running, you can put the purchase cost into better perspective. We were very happy with our airplane and feel it is a tremendous value for the money.
A few years ago, a pop star and her entourage perished in a fiery crash in the Bahamas. They weren’t flying in a Navajo, but the insurance companies raised the price of commercial insurance (read: for Part 135 operations) on all piston twins to the point that it became cheaper to insure a turboprop aircraft at the same thresholds of liability.
Rather than continue to operate the Navajo in an underinsured state, we opted to get out of the piston charter business and focus on turboprops, so we sold the Navajo. For a personal use twin, the PA-31 Navajo is as close to a personal airliner as the average pilot could afford to buy and fly.
Michael Leighton is a 3,600-plus CFII MEI-ATP, as well as an A&P mechanic and former FAA Accident Prevention Counselor. He operates an on-demand aircraft charter company located in South Florida. Send questions or comments to editor@www.piperflyer.com.
