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The Piper Navajo: The Last of the Lock Haven Planes

The Piper Navajo: The Last of the Lock Haven Planes

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After initially feeling intimidated by the size of the Navajo, contributing editor Kristin Winter found that it really one of the easiest and most gentle aircraft she had flown.

Navajo series sprang from the same fertile period of Lock Haven engineering that delivered the Twin Comanche and the Aztec. By this time, Piper’s Vero Beach facility had been established to develop the Cherokee line and its numerous spin-offs. When the last of the Navajo series rolled out the door at Lock Haven in 1984, it was the sad ending of an era.

One can see immediately that some of the same engineers working on the Navajo also worked on the Twin Comanche and the Aztec C. They have in common the shark-nose cowlings and the wing structure. The Twin Comanche and the Navajo have a very similar airfoil. Sitting side by side on the ramp, these two almost look like momma plane and baby plane.

Apart from size, the most striking feature for Piper owners was that the Navajo was the first Piper with an airstair door. No more climbing over the wing to get in. The passengers loved it. Combined with a large aft baggage area and a fairly roomy nose baggage compartment, the Navajo proved a most useful aircraft for family, business, and air carrier operations.

PA-31 Navajo

The original Navajo had 310 hp turbocharged Lycoming engines. Piper also made a few normally aspirated Navajos with 300 hp engines. The dozen or so normally aspirated aircraft that were produced found some popularity with Canadian cargo haulers, but otherwise the market embraced the turbocharged version.

The original Navajo was just called the Navajo. It was designated the PA-31 for the turbocharged model, while PA-31-300 was reserved for the normally aspirated version. It is fairly common to see the turbo model designated as the PA-31-310.

The aircraft was introduced in 1967. It could seat six in a comfortable club layout or in a six-seat commuter configuration, plus two in the cockpit. The panel featured a standard six-pack configuration with full copilot instruments.

The Navajo used the basic hydraulic system of the Aztec with one exception: the flaps in the Navajo series were electric.

The fuel system had main and auxiliary tanks in each wing holding 192 gallons. At 65 percent cruise speed of about 180 ktas, this gave the aircraft a five-hour endurance with VFR reserves.

The early Navajos, and the later “short body” Navajos, had a gross weight of 6,500 pounds and typically had useful loads of approximately 2,200 pounds, which meant you could load five or six people and baggage and still carry full fuel.

Navajo B

With minor improvements—such as an optional three-bladed prop and a ninth seat installation—the Navajo continued production until 1971, when Piper came out with the “B” model.

The Navajo B’s most visible change was the addition of nacelle lockers long enough to store skis and golf clubs. A three-blade prop was now standard for the Navajo B, and there were some excellent options available.

A cargo door was now an option for hauling very bulky items. It also came with an optional crew door so that the pilot did not have to climb up the aisle after securing the main cabin door.

Air conditioning was now standard, as was a new flight director system dubbed the Altimatic V. This was Piper’s designation for the Bendix FCS-810 system. One downside of the new equipment was a reduction in useful load of more than 100 pounds.

Navajo C and C/R

For the 1975 model year,1 Piper turned the Navajo into two models, having designed the Chieftain two years before, which we will discuss later. Perhaps as a result of the loss of useful load with the B model, Piper introduced the C model which harkened back to the original Navajo without the wing lockers and the fancy cabinetry of the B model.

The C/R maintained the accoutrements of the B model, but engineers increased the horsepower to 325 and made the props counter-rotating as they had done with the Twin Comanche and the Chieftain. (The latter feature seemed to be more marketing-driven than engineering-driven.)

These two models continued to be produced with refinements until the end of production in 1983. The 1976 model was unchanged from 1975.

With the 1977 model, the “C” designator was dropped so now there was just the Navajo, the Navajo C/R and the Chieftain. That year also saw improvements in the internal furnishings.

In 1978, the aircraft got increased gear and flap extension speeds to help slow the aircraft down.

For 1979, the Navajo and the Navajo C/R got the overhead switch panel that had been standard on the Chieftain.

In 1980, the Navajo and Navajo C/R could be equipped with icing protection equipment that Piper demonstrated could meet the then new testing requirements which came to be known as flight into known icing certification (FIKI). Prior to this, PA-31 aircraft were approved for flight into light to moderate icing conditions, but the systems had not been tested to the new standard.

The last significant change came with the 1981 model year in the form of optional wing locker fuel tanks.

Chieftain

The development of a larger and more powerful Navajo began early in the Navajo’s production run. Piper pursued a design that would be more suitable as a commuter and more luxurious for the corporate market.

Three different models grew out of this early effort. The Navajo C/R and the Chieftain are two; the third was the pressurized Navajo, or P Navajo. The P Navajo and the later Mojave are more related to the Cheyenne and were listed on a different Type Certificate from the Navajos (and hence, outside the scope of this article).

The Chieftain was the first result of the effort to create a bigger and better Navajo. Piper experimented with 325 hp engines and 350 hp engines. The desire for more cabin space and passenger-carrying capacity led to a 24-inch plug added to the fuselage forward of the main spar.

The aircraft also received beefed-up flooring to give it an increased ability to handle cargo and passengers. Piper engineers first tried this configuration with a 7,000-pound gross weight and 325 hp engines but the single-engine performance was too anemic, so they went to the 350 hp engines.

The Chieftain also received the wing lockers, air conditioning, and other upgrades that went into the Navajo B. It can be said that visually, the Chieftain is a Navajo B with a 24-inch extension in the fuselage. The Chieftain can be distinguished by the smaller square window just aft of the pilot’s side window.

The Chieftain was a hit. It sold well in both the nine-plus-two commuter configuration and the eight-passenger executive configuration. To this day, the Chieftain is used as a commuter and corporate aircraft the world around. There are working Chieftains in Alaska with 40,000 hours on the airframe.

The Chieftain received the enhanced de-icing system in 1980 that Piper demonstrated would actually cope with prescribed amounts of aircraft icing. Like the Navajos, the only significant change was the addition of boots inboard of the engine nacelles and a heated stall warning vane.

Toward the end of its production life in the early 1980s, Piper optimized the commuter version and marketed it as the T-1020.Only a few dozen true T-1020s were sold, as the market was generally in decline.

During its production run, the Chieftain received most of the upgrades that the Navajo received, but still had a useful load of between 2,375 and 2,400 pounds in the executive configuration.

Flying the Navajo series

I have a significant amount of time in the original Navajo, the Navajo C and the Chieftain.

My introduction came as a bit of a surprise. I had just survived my first Part 135 checkride in a C-310 and was told by the chief pilot that he would be giving me a checkride in a Navajo and that I would be returning to the remote base in said Navajo.

I stifled the urge to freak out, as I had never been in a Navajo and could barely identify one on the ramp. But there sat a 1969 Navajo. I was seriously intimidated by this, the first airplane I ever looked up to when getting in.

I busily memorized the numbers and where the switches and levers were and managed to survive the checkride. (No training, mind you; only the checkride.)

As the late afternoon shadows were advancing and the clouds were getting thicker and lower, I pointed the Navajo west on an IFR flight in an aircraft that I had about 1.3 hours flying. I marvel to this day at my employer’s rather cavalier attitude about training.

Fortunately, as the intimidation factor receded, I discovered that it was really one of the easiest and most gentle aircraft I had flown.

Center of gravity

The short-body “Joes” only diverge in handling characteristics from the Chieftain with the longer fuselage when it comes to handling with an aft CG. The Navajo and the Navajo C/R have a four-inch CG range at gross from 134 to 138 inches aft the datum. With the CG further aft than 136 inches, the pitch stability at slower speeds can become a bit neutral.

Pilots coming into land with full flaps and starting to roll in some aft trim beginning the round out for landing have had difficulty controlling the aircraft if they make a quick, full power application to initiate a go-around. It was in response to this characteristic that the Chieftain got its fuselage stretch up front and not in the aft.

Fortunately, it is not hard to keep the CG at the forward end of the envelope in the short Navajos. Unless you have passengers in the seventh and eighth seat, it almost doesn’t matter how you load the plane. With seven passengers, you need to fill the nose baggage compartment first with whatever baggage is being carried.Fuel burn

In my experience, Chieftains burn a little more fuel and tend to be three to five knots slower than the 310 hp Navajos, or “Baby Joes.”

The Baby Joe would deliver 180 ktas when heavy at 8,000 to 10,000 MSL and burn less than 32 gph. As fuel burned off, the speed would creep closer to 185 ktas. I would flight plan 200 pounds an hour, and it was generally very close on legs of an hour or so.

Takeoff and landing

The Navajo has good short-field performance, and I have been in and out of 2,500-foot grass strips—though not at gross weight.

Some Navajos have their flaps limited to 25 degrees instead of 40 degrees. The additional 15 degrees adds a substantial amount of drag which is helpful for steeper approaches and ground roll, but doesn’t change stall speed appreciably.

The landing gear is robust with dual hydraulic pumps. It has inner gear doors, though there is an STC to remove them and install a fairing instead. With the inner gear doors, drag increases at the beginning of a retraction cycle so it is important to make sure that you have adequate ground and obstacle clearance before grabbing the big gear handle and pulling it out and up.

Otherwise, the whole series are quite stable and comfortable.

Icing and turbo cooling

Navajos handle turbulence and ice well. When properly equipped, all Navajos are capable of flight in icing conditions. I can say from experience that even with non-FIKI equipment, a couple of inches of mixed ice on the unprotected surfaces caused me little concern as long as the boots were in good condition and were shedding the vast majority of the ice.

The turbocharging system is automatic which reduces the workload on the pilot. As long as the pilot operates the throttles smoothly at a measured pace, takeoff is at full throttle travel and the system will set the appropriate power based on the density altitude.

The big, electrically-driven cowl flaps are normally closed in cruise, but are highly effective in cooling the engine if the ambient temperatures so require.

It will take a whole separate article to do justice to the maintenance on the Navajos, but maintenance is generally straightforward with no more significant issues than one would find in any of the Piper products—and likely somewhat less than the big Cessna twins. (Look for an article by Winter that explains Navajo maintenance and ADs in an upcoming issue of Piper Flyer. —Ed.)

The Navajo stacks up well

The Baby Navajo has the lowest operating costs of the series and compares favorably to a 58 Baron, with much more capability. If one has the budget for a C-310 or B58, the Baby Navajo is a viable alternative. While some argue that a Navajo is not as sexy to fly, you can’t get a potty in either of those two competitors, and family will love the Navajo’s airstair entrance and club seating with tables.

The only significant downside is finding a hangar that can hold the Navajo’s nearly 41-foot wingspan and 13-foot-tall tail. Once you get over the size, the Navajo series are great flying utility aircraft that are likely to be around for a long time.

1 Piper followed the tradition of generally starting production of one model year in the last few months of the previous year.So even though an aircraft has a production date in 1974, it may still be a 1975 model, for example. Through most of the 1970s and early ‘80s, Piper’s serial number told you what the model year was. The first two digits after the dash told the year. “31-7512004,” for example was produced in October 1974.

Kristin Winter has been an airport rat for almost four decades. She holds an ATP-SE/ME rating and is a CFIAIM, AGI, IGI. In addition, Winter is an A&P/IA. She has over 8,000 hours, of which about 1,000 are in the Twin Comanche and another 1,000 in the Navajo series. She owns and operates a 1969 C model Twinkie affectionately known as Maggie. She uses Maggie in furtherance of her aviation legal and consulting practice; she also assists would-be Comanche, Twin Comanche, and other Piper owners with training and pre-purchase consulting. Send questions or comments to .

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