Cabin Class Twins

The Aerostar pulls away speedwise but doesnt carry much. Pipers Navajo may be the best overall compromise.

Okay, so the stock market has taken a dump. But the up side is that suddenly, there are more cabin class airplanes on the used market, cheap.

To sort through the choices, we’ll round out our series on used twins by taking a look at the non-Cessna iron available for those who want luxury and are willing to pay for the maintenance these complex, aging machines demand.

At the risk of sounding preachy, we’ll reemphasize four key points: Get a thorough pre-purchase inspection; don’t short yourself on proper training; plan on EGT/CHT engine analyzers for each engine and, last, if you cant pay the maintenance bills these airplanes incur, don’t buy one in the first place. That said, if you can afford one, there’s good value in this aircraft.

Beechcraft Duke
An owner recently described the Duke as the hidden treasure in the piston-twin market. He may be right. And while the Duke is proof positive that sexy good looks don’t always equate to airspeed-the design has very high drag-there are a number of surprisingly low-time airframes on the market for reasonable prices. For about $350,000, you can buy and refurbish a Duke, and you’ll have a highly capable, pressurized personal chariot.

The Duke was first flown in 1966 as a pressurized step-up from the Baron, whose wing and landing gear it shared. The cabin was entirely new, with esthetics rather than performance as a major driver in the design. Where the Baron is fast for its power, the Duke is frustratingly slow for having 380 horses per side.

In the high 20s, it does about 210 knots. Had the engineers been allowed to clean up the nose and cowlings, the airplane would probably have nudged 240 knots. Cynics wonder whether it was kept slower than the King Air 90 series for marketing purposes.

After the first Duke was delivered in 1968, continuous small upgrades were made with the A and B models, including a 50-pound gross weight increase, until production ended in 1982. The airplane was marketed as luxury transportation for the owner pilot, and appointed to match.

The interior is comfortable with styling ranging from merely luxurious to New Orleans brothel. Payload for the airplane is among the best in its class, giving a good tradeoff between passengers and fuel. Its possible to carry six people, 200 gallons of fuel and some baggage. The good useful load is handy, as the Duke sucks fuel, on the order of 42 GPH in cruise.

Handling and Performance
Pilots describe the Duke as handling like a King Air, with the most common description of the controls as heavy followed immediately by an indication that they like the way it handles. Rudder force at Vmc is 150 pounds, the maximum allowable under the FARs and the heaviest of all GA twins. Yet we heard absolutely no complaints about single-engine handling.

The props turn at 2900 RPM on takeoff but the blades are short to keep the tip speed subsonic, so acceleration on takeoff suffers. No owner we spoke with would base a Duke at a runway shorter than 4000 feet and wouldnt even use a runway shorter than 3000 feet at sea level.

While the Duke has an excellent safety record, tales of them sailing off the ends of runways seem true. Upon leaving the ground on takeoff, the airplane is described as ballistic, with little feel and a poor initial climb rate. Once at speed, the climb rate is satisfactory, over 1500 FPM, which, we were advised, holds steady into the low 20s.

Owners report that if they don’t have magneto problems-some seemed to-theyll cruise in the high 20s at 210 KTAS on 42 GPH. One reported smugly that performance was about the same as the Cessna 421C (, but that his Duke cost $200,000 less.

One sure way to ruin the engines on a Duke is to make a significant power reduction and then descend. Fortunately, leaving them at cruise power and simply tipping the nose down will generate a 1000 FPM descent with the speed still in the green arc. Drag does have its benefits.

Flight Deck and Cabin
This is a classy airplane. The flight deck is thoughtfully and almost sumptuously presented. Power gauges are up high where they can be easily seen on takeoff, visibility is good and the gear and flap levers are positioned as they are for most GA airplanes, rather than the traditional Beech fashion of gear lever on the right and flaps on the left.

The 4.7 PSI pressurization differential gives a 10,000-foot cabin at 24,000 feet. The aisle is narrow, so moving around is not easy, but once pax are seated, the cabin has plenty of room. Elbow room in the aft seats is not as good as in the early models, due to the tapered fuselage and positioning of cabin ductwork. The only negative we heard was that the heater is not adequate for high- altitude flight in the winter.

Owners advised that no one should consider operating a Duke without an engine analyzer for each cylinder. (While preparing this article we came to believe that this is true for any six-cylinder airplane.) The engines are pulling a lot of horsepower from each jug and careful attention to operation is a must.

The early versions of the TIO-541 developed a lousy reputation with their 1200-hour TBO. Later ones, with improved pistons and cylinders, have a 1600-hour TBO, which, owners claimed, can be exceeded by a few hundred hours by a pilot who operates carefully.

As with any airplane, corrosion is the most commonly reported problem, worse on the earlier Dukes, due to shorter engine exhaust stacks. The control surfaces on the tail are magnesium, so they should be checked carefully for corrosion. Its recommended that generators on the airplane be overhauled every 500 hours because doing at 900 hours will be more expensive.

Turbocharger controllers have a reputation as being unreliable on the Duke, so a test flight should include seeing if theyll hold manifold pressure. One owner reported that when he began looking for a Duke, he was pleased to find a number of them on the market with less than 2000 hours on the airframe.

He found one with 1200 hours on it, paid about $185,000 and had the engines overhauled, replaced the fuel bladders, all the radios, put in electronic tachs, painted it, and redid the interior all for under $350,000.

We strongly recommend joining the Duke Flyers Association. Jim Gorman writes the newsletter and provides a good information package for prospective Duke owners if you call 419-529-3822.

Piper Navajo Series
Piper came a bit late to the cabin class game, first delivering the Navajo in 1967. Late did not mean an ill-considered airplane, however, as the series proved popular, with over 4000 being delivered in a myriad of configurations.

Only about 14 of the original 300 HP versions left the factory before engine power was boosted to 310 HP, the first of several steps up in power that topped out at 425 HP in the pressurized version. In the process, the fuselage was stretched some two feet (initially for the Chieftain, probably the best model), fuel capacity was increased from a standard 182 usable gallons for all unpressurized ships to as much as 236 gallons with all the optional tanks.

Most all Navajos were turbocharged, and two tries were made at pressurization, the P-Navajo and the Mojave. The P-Navajo was, frankly, a disappointment. We suggest staying away from that model as it tends to be a collection of maintenance headaches in loose formation.

The Mojave is not a great pressurized airplane, but the value of the marque has held up and there are those who speak we’ll of it. We believe the unpressurized Navajos are good airplanes and suggest that a buyer seeking pressurization first consider a twin from Beech, Cessna or Aero Commander.

Handling and Performance
Many pilots cut their professional teeth as newbies in the air charter world by flying some version of the Navajo. Its a stable instrument platform with pleasant control harmony, but it has some unpleasant traits that have bitten more than one pilot when the airplane was loaded near the aft or forward CG limits.

A good introduction to this airplane is a must, as pitch stability drops off rapidly as the CG nears the aft limit. We were told that the best of the short body Navajos is the standard PA-31-310, even more so than the counter-rotating engine-equipped Navajo C/R, despite the C/R having 15 more horses per side, largely because the C/R starts out 90 pounds heavier and has less range.

The best of the entire line, in our opinion, is the Chieftain. The two-foot stretch and boost to 350 HP per side, plus what proved to be the best engines of the bunch, resulted in the nicest flying and most flexible airplanes of the series. The P-Navajo and Mojave proved to have continual engine problems, were dogs on one engine and generally were airplanes that were as wrong as the Chieftain was right.

All Navajos are decent short field machines if operated correctly. We wouldnt hesitate to use runways as short as 3000 feet in most models of the Navajo series except in hot weather. VGs are available for most all Navajos, however, unlike many other twins. On most, the installation does not result in an increase in allowable gross weight.

Flight Deck and Cabin
The cabin sold a lot of Navajos. Its spacious and the large windows make it seem even bigger. Piper did a nice job with interior appointments as well. However, some of the corporate interiors were heavy, so be sure and check the weight and balance data before you buy, as some are restricted to only about 800 pounds in the cabin with full fuel.

The flight deck is generally adequate. Taller pilots will appreciate the Chieftain more than the short-bodied Navajo. The panel is more thoughtfully designed than earlier Piper twins, with power gauges up high in the center where they can be read at a glance.

A serious shortcoming, from both a crashworthiness and human factors standpoint, is the location of a number of switches and gauges on the overhead. Piper should have been able to locate those switches elsewhere so that they wouldnt pose a hazard to pilots heads in a crash. Plus, pilots with bifocals find it difficult to read the labels on the ceiling switches.

Its good that the Navajo is relatively easy to work on because ADs on the series have been issued by the bushel. Many require repetitive inspections of flight controls, control surfaces and the landing gear.

The most common complaints we received involved the bugaboo of most all twins, the landing gear, as we’ll as corrosion. We heard complaints regarding difficulty in removing and replacing the cowlings and that mag replacement is a five-hour task.

Any pre-purchase inspection of a Navajo requires an involved search of the logbooks to determine compliance with ADs before even opening the first inspection plate. Owners report that as long as they kept on top of routine matters and repetitive inspections, their airplanes were reliable and were either good moneymakers or decent family transportation.

Aero Commander
Many would-be buyers are astonished at how long the Aero Commander line of twins has been around and just how extensive the line is. Shortly after World War II, Ted Smith designed a high-wing twin that went through several iterations before coming to be certified as the Model 520 in 1952.

He and Cessna had extensive discussions reaching the conclusion that his design would not form the basis of a line of Cessna high-wing twins. Smith continually expanded his series of airplanes through the 1950s by installing larger or smaller engines on what was a very large airframe for a general aviation twin.

The wingspan was nearly 50 feet, length over 36 feet and the top of the tail was some 14.5 feet above the ramp. Heaving that kind of bulk through the air meant that the smaller engine versions are not particularly quick.

The 260 HP and smaller engine models cruise at about 155 knots. The 290 HP versions range from 160 to 180 knots while swallowing 30 to 34 GPH. In 1955, the 680 series was christened as a 340 HP geared, supercharged Lycoming-engined speedster.

The fuselage was stretched about the time Aero Commander decided to build what turned out to be a popular turboprop line. The company hung piston engines of 380 and 435 HP on the long-bodied models 680 and 685, respectively, (and a pressurized version of the Model 685), bumping overall performance and load carrying ability nicely. Production ended in 1979, however, Twin Commander, Inc. continues to support the line.

Handling and Performance
While Aero Commanders are not particularly fast for their power, nor especially long-legged, they compensate effectively with the ability to largely fill the seats when the fuel tanks are full, along with a reputation for toughness and excellent handling.

Bob Hoover impressed generations of air show fans doing incredibly smooth aerobatics with one or both engines shut down in the 500S Shrike. He also showcased the ability of the airplane to fly, with fully responsive controls, at an indicated airspeed of zero, which may actually have been a salute to a poorly placed pitot tube.

Pilots are uniformly complimentary of the handling of the entire line, once theyve mastered the oddball nosewheel steering that involves tapping the brake pedals and a few drunken-sailor sessions during the steep part of the learning curve.

A company that does scheduled small package hauling, employing low-time pilots, owns a substantial proportion of the 500 series airplanes. Their safety record is good, at least a partial tribute to the forgiving nature of the line. Stall speed is only 59 knots, so a number of these airplanes are based at what to us seems to be shockingly short fields, some under 3000 feet.

Flight Deck and Cabin
Aero Commanders are passenger-friendly, despite high cabin noise level and baggage that cant be reached in flight. The cabin is roomy and comfortable; most of the airplanes have separate entry doors for passengers and pilot.

Its difficult to load the airplane out of the CG limits, something thats much appreciated among owners. The fuel system is dirt simple. There is one filler for all five tanks (four in the wings and one, to our dismay, in the fuselage, overhead).

Fuel feed to the engines is automatic; the pilot need not do any tank switching. There is but one fuel gauge that shows full until the 156 gallons has burned down to 135 gallons, at which time it starts its descent toward empty.

For some reason, the Aero Commander line of twins see more than its share of line personnel pouring jet fuel into piston pounders. Maybe its because they all look as if they should have turboprop engines. In any case, it behooves pilots to watch refueling operations.

The flight deck is nicely designed, although its age shows and there isn’t enough space for all the avionics many owners would like to have. Some creative installations may be seen in the used fleet.

Taller pilots are cramped, with the side column for the control wheel sometimes making it interesting to figure out where to put ones left leg and still maintain rudder and aileron inputs when landing with a crosswind.

The landing gear and flaps are hydraulically operated. Some of the airplanes only have one hydraulic pump. The wise pilot knows which engine drives that pump and plans engine failure procedures accordingly. Twin Commanders have a relatively high incidence of landing gear events. There’s no squat switch to prevent inadvertent retraction and more than a few pilots have pulled the gear up at the wrong time.

The most significant maintenance aspect of the line is a nasty history of spar corrosion with an attendant need to assure compliance with the ADs that resulted. Mechanics tell us to watch the nosegear trunion carefully and pay attention to the hydraulic system generally as seals, valves and lines have to be replaced on a regular basis. This is a hydraulically actuated airplane thats reliable if the owner is willing to set up a progressive maintenance program but expensive for any owner who gets behind the maintenance demands. Where the hydraulic and fuel lines pass from the wing into the fuselage near the top, they flex and crack over time, leading to leaks.

Main gear strut bearings have no grease fittings and should be replaced every 1000 hours, or the STCd grease fittings installed. We were also advised that entrance door and window seals wear out and need to be replaced to avoid water leaks.

The engines generally get good marks except for the geared, supercharged ones on some of the earliest airplanes, despite some low TBOs on a number of the unpressurized versions. Most mechanics gave us one or two of the above comments and then added that the airplanes were strongly built and tended to be quite reliable, even with age.

Production history was erratic, teething problems were legion, the cabin isn’t terribly comfortable and the accident rate has always been we’ll above other twins, but the Aerostar series ( has that special something that attracts pilots like Packer fans to cold weather.

That something is a combination of sheer speed plus handling qualities that reward a proficient pilot. Most Aerostars will outrun low-end turboprops. The original Model 600 had 290 HP normally aspirated engines while the 601 was turbocharged but had manually controlled wastegates that took a little work to master.

The A models of each had heavier cranks and cases on the engines and higher TBOs, (something that should be retrofitted to any airplane you consider). The 601P (for pressurized) came out in 1974 and proved popular.

When Piper bought the marque, a number of small improvements were made, leading to the 602P, probably the best of the 290 HP series. The last model, the 700P, was produced in 1984. Only 25 of those 350 HP rockets were built. They will hammer along at 250 knots. When one changes hands, it does so for we’ll over $400,000.

Handling and Performance
Ted Smith designed the Aerostar series to go fast by mating the smallest cabin he could get away with to some relatively big engines. The normally aspirated models will cruise above 200 knots at their best altitude of 7500 feet.

The turbocharged versions, 601P and 602P will comfortably run at 230 knots. Fuel burn is correspondingly high at speed, starting at 34 GPH and escalating. But, that doesnt seem to phase those who revel in raw speed.

Handling is crisp and draws raves from pilots; however, the airplane is not tolerant of someone who doesnt take the time to learn its foibles. Wing loading is 35.4 pounds, among the highest in general aviation.

While it makes for a comfortable ride in turbulence, the drag curve at low speed has to be respected, so as not to have the airplane sink out from under you on final. Single-engine handling demands regular practice. Stall behavior lead to restrictions that were cured with Pipers water rudder under the fuselage or Machens vortex generators. The majority of owners seem to prefer the Machen mod to Pipers approach to the problem.

The high wing loading and relatively short props mean that an Aerostar consumes lots of runway on takeoff. Pilots advise that once the airplane is in the air, the first part of the climb is unlike almost any other piston powered airplane. The airplane feels like a projectile rather than a flying machine during the seemingly long time the pilot waits for it to accelerate to Vy, when the climb rate rapidly rises and a sense of feel comes into the controls.

This is a demanding airplane to fly, particularly when something goes wrong, as reflected in a higher accident rate compared to other twins. Good recurrent training is a must. We also suggest contacting the Aerostar Owners Association- – or giving them a call at 912-244-7827. The group has an extensive library of publications and videos not just on maintenance but on operating techniques.

Flight Deck and Cabin
In the process of building a fast airplane, certain compromises were made. The cabin is not terribly comfortable. Its nearly impossible to fill all six seats, load any baggage and carry enough fuel to get out of even a small state.

Many owners remove one of the middle row of seats in homage to a fairly low useful load and the shattering propeller noise level in those seats. It also helps with loading problems because the center of gravity moves forward with fuel burn.

Ted Smith was not known for user-friendly airplanes, so the panels can be a hodge podge of switches and gauges; there simply isn’t enough space for all the gadgets a pilot might want. One owner has had to make a progressively longer console going aft from the throttles to install all the electronic goodies he put in his airplane.

Nosewheel steering is via a rocker switch that frustrates newcomers to the airplane until they suddenly get the hang of it. The fuel system has been the source of some ADs due to uneven feeding and the need to have a gauging system that actually has a separate gauge for each tank.

Part of the reason Aerostars go fast is that the package is relatively small (the cabin is three inches narrower than a Cessna 310), so a lot of stuff is jammed into that small package and its not all that easy to get at to maintain.

Fortunately, this was one of the few airplanes on which we did not consistently hear of any major problems or of any one system that regularly caused trouble. We did get the standard warnings regarding corrosion in older airplanes, most notably in the early, unpressurized models.

Another warning we heard was that prebuys were turning up evidence of illegal or bogus repairs, leading to some expensive rework to make them safe and legal. Overall, we were told that for support, owners should call the owners association and Aerostar Aircraft, Inc. at 800-492-4242. Aerostar Aircraft owns the type certificates, provides customer support and tracks trends in the field.

We were also advised that it now makes many parts that are more robust and generally better than the originals. Aerostar Aircraft also specializes in a factory restoration program.

Which One?
Selecting one of these machines is one of the tougher buying decisions in aviation. The first step, for us, is to boil it down to the desired mission. If we were looking for speed for a personal luxury rocket and werent carrying many passengers, wed pick one of the pressurized Aerostars or a Duke.

If the group going along were bigger and we still wanted luxury and speed, the pressurized Aero Commanders are about perfect. We might consider a Mojave but we wouldnt give a P-Navajo a second look, due to maintenance issues.

Beyond that, we conclude that operating costs among the non-pressurized airplanes are similar, which is to say just plain expensive, so much of the decision is driven by acquisition cost.

For a comfortable hauler for a family or business, we like the Navajo Chieftain and the Aero Commanders, with the Navajo being a little better in efficiency considerations.

Also With This Article
Click here to view the cabin class twin data.
Click here to view “T-Bones and Queen Airs.”

-by Rick Durden

Rick Durden lives in Michigan. Hes an aviation attorney, CFII and contributing editor to Aviation Consumer.