Beechcraft Duchess

Among light-light twins, the Duchess is one of the better performers, with good slow speed traits and decent cruise speed.

0

In the history of general aviation manufacturing, some airplanes were instant hits and destined to endure. The Beechcraft Bonanza is a classic example.Others seemed like good ideas at the time, but either the market timing was wrong or the models just didnt have the sales appeal the factory had hoped for. The Mooney PFM qualifies for that label and so does another airplane, Beechcrafts entry-level Duchess twin.

The Duchess sprang from the idea that if you got a customer in the door to buy an entry-level product, the same customer would graduate up the line and eventually buy more sophisticated and higher profit margin airplanes. The legacy of this market-think was a series of entry-level twins that still do service as modest family airplanes or trainers for flight schools.

Demand for such airplanes is somewhat fickle and tied to the price of gas, but the used market satisfies most of the demand. Piper, with its Seminole, and Diamond, with its emerging Twin Star, are the only two manufacturers still making twins in this class. The design brief of entry-level or light-light twin was to offer what was essentially a single-engine size airframe, but with two engines instead of one. The concept had been around for quite some time when the Duchess emerged in 1978.

Piper had the first of these airplanes in the Apache, its woefully underpowered small twin of the early 1950s, and 160- to 180-HP class twins included the Travel Air and Twin Comanche.

But those airplanes had really been designed with owner/buyers in mind, while the Duchess and the Seminole were primarily intended for the training market. The Seminole lasted in the market but the Duchess did not. In fact, it was gone by 1982. The Duchess has a fairly short model history, with only a five-year production run beginning in 1978 and few model changes. Despite the fact that the Duchess looks somewhat like a Seminole clone at first glance, looks can be deceiving. In reality and following the Beechcraft tradition, Beech produced an elegant airframe in the Duchess thats a cut above other light-light twins. Conscious of cost, Beech took steps to minimize both design and construction expense, while at the same time keeping an eye out for future maintenance costs.

To keep design expense down, Beech did in the Duchess what Piper practically built its entire business on: It reached into the parts bin, using off-the-shelf components liberally from other models. The nose-gear, for example, comes from the A36 Bonanza. The fuselage is a somewhat modified Sierra fuselage, a bit of departure from the Seminole example, which is built on a fuselage little changed from the Arrow. In the Duchess, the Sierras wing spar was redesigned to carry the weight of the engines, which also yields a necessarily more robust cabin structure. And with two doors in the cabin, that beef-up was necessary.

To keep construction expense down, bonded structures were used extensively, with the ailerons being one example. And to keep maintenance expenses low, Beech chose rock-solid carbureted Lycomings, a decision that yet pays off for owners in reasonable maintenance and overhaul costs. Beech generally did the job right. The engines have proven reliable and the airplane, as twins go, is not at all expensive to maintain.

Despite the commonality of components with the Sierra, the Duchess most distinctive feature is its eye-catching T-tail, which was a design feature much in vogue at the time of the airplanes introduction, particularly at Piper, whose infatuation with them extended to several models.

T-tails do offer certain advantages, but the design has to be carried off correctly. In Pipers case, the T-tail was more of a fashion statement, or should we say a marketing mirage. To this day, owners continue to debate whether Pipers version of the T-tail introduced handling quirks. Some say its no different than a conventional tail, but its worth noting that there was an STC available to put a conventional tail in place of the Tomahawks T-tail, indicating not only how poorly the T-tail was regarded, but what lengths some thought to go to in order to get rid of it.

Beech didnt have much experience with T-tails in small airframes and actually went with that design after unsatisfactory tests with a conventional tail. Flight tests showed that the stabilizer was buffeted by propwash, increasing airframe vibration levels. At the same time, the disturbed airflow demanded that the stab be made larger. The most efficient solution was to put the tail up high, out of the wash and into undisturbed airflow, which eliminated the prop-induced buffet. It also made the surfaces more effective so there was no need to enlarge them, saving cost and weight.

For a twin, the length of the CG envelope and the position of the tail surfaces are critical because much of a twins design is biased toward the worst-case scenario: an engine out at gross weight, with a rearward CG. The T-tail actually helped this. Because its mounted atop a swept fin, it has an effectively longer moment arm, which enhances its power and so enhances pitch stability.

Trim changes with landing gear or flap extensions are thus minimized. This configuration also makes for a much longer CG envelope-a total of 10.9 inches. And, because the stab acts as an end-plate for the fin-rudder combination and prevents airflow spillage over the top, yaw authority is enhanced. On the whole, the T-tail worked out quite well for the mere 15-pound weight penalty the additional structure exacted.

Another bugaboo in twins is the critical engine. With both turning in the same direction, loss of the left engine means that the thrust vector of the right engine is effectively located further from the aircraft centerline, which makes for a sporting Vmc reaction. The Duchess has counter-rotating engines to address this, a feature found on a handful of twins. The counter-rotating right engine is no more expensive to overhaul than the left engine, but getting parts and accessories for it can occasionally be difficult. Some owners, for example, have told us they carry spare starters because finding a replacement can sometimes require a determined search.

End of the Line
As admirable a design as the Duchess is, it lasted only five model years, with a total of 437 built with about 270 remaining on the U.S. registry. The Duchess demise wasnt really the fault of the airplane but just plain bad market timing. It appeared just as the great GA downslide was beginning, dropping from nearly 17,000 airplanes made in 1978 to just a few thousand by the early 1980s. And despite the Duchess reasonable fuel burn, it also arrived a year before the second great U.S. gasoline crisis. Potential owners were worried about getting gas for their cars, much less a twin-engine airplane.

Production numbers for the years for both the Duchess and the Seminole were nearly identical: Piper built 468 Seminoles before shelving it in 1982.Piper resurrected the Seminole in 1989 and 1990, building an even dozen of the airplanes. Since then, it has continued to build a handful of Seminoles each year. Current new price is about $450,000.

Although there arent a lot of either airframe on the used market, the Beech carries a slight premium over the Seminole. A 1979 Seminole retails for $106,000 versus $118,000 for the Duchess. But because so few sales are recorded in this small market, these values are based on few sales and may be subject to considerable variation. When new, by the way, the 1979 Duchess retailed for $125,000. Unlike some popular singles of the day-say the Mooney 201-it has not exceeded its new value.

Performance
As light-light twins go, the Duchess can be considered better than average.Its best thought of as performing like a high-performance single. But no one would mistake it for a Baron. Cruise numbers are thus: At max cruise power at 5000 feet (24 inches and 2700 RPM), the book says 164 knots true. Pull the props to 2500 RPM and clip four knots off that. Pull it back to economy cruise-20 inches and 2300 RPM-and airspeed falls off to 137 knots, little faster, if at all, than an Arrow on a little less than twice the fuel.

Still, the Duchess is economical as twins go. With the throttles full forward, it burns about 11.3 GPH per side or 22.6 GPH total. At recommended cruise power, fuel flow drops to 21 GPH, while at gas-save cruise, the Duchess needs 14.6 GPH total. Not too bad as gas creeps toward $4 a gallon.

With 180-HP per side and a gross weight of 3900 pounds, the Duchess displays decent takeoff performance for its class. According to the book figures, at max gross on a standard day at sea level, it can get off the ground in 1017 feet and clear a 50-foot obstacle 800 feet after liftoff. Not too shabby for a light-light twin, or any airplane for that matter.

However good that is, a potential owner shouldnt get the idea that the Duchess is a super short field performer or that it can be loaded to the gunwales and stuffed into 2000-foot runways. For the conditions cited above, the accelerate-stop distance is about 2600 feet. If an engine lunches during the takeoff roll, figure youll need at least 3000 feet to get the airplane stopped, hence the good advice from multi-engine veterans to consider 3000 feet as a safe minimum-length runway for other than high density altitude conditions.

The same considerations apply to how the airplane is loaded. The lighter it is, the better. At gross weight, the Duchess is an OK climber on both engines, but with one engine caged, its not so hot. From above 5000 feet, expect barely 100 FPM with one shutdown. Again, this isnt spectacular performance, but its not as abysmal as some other designs (the early Apache comes to mind).

The Duchess carries 100 gallons of fuel which, as twins go, isnt a lot, but the engines are so economical that it gives the airplane plenty of range.In economy cruise, you can fly about 760 miles at 11,500 feet cruising at about 150 knots or so. At the end of your trip, youll be able to clear the standard 50-foot obstacle and bring your Duchess to a halt in about 1881 feet at a sea-level airport with no wind. These numbers are those listed in the Aircraft Bluebook Price Digest, not those in the manual, which are quite a bit shorter.

Cabin, Loading
Beech airplanes have a well-deserved reputation for being comfortable, even at the low end of the line, such as the Musketeer, the Sierra and the Duchess. The cabins tend to be wide and the seating is upright, with seats constructed to bear up well to use. Despite the fuselages noticeable taper at about the instrument panel, the front seats have 44 inches of cabin width.Thats outright huge compared to most other aircraft below the cabin-class rank. Owners tell us in addition to being comfortable to sit in, the Duchess is also relatively quiet for a twin. Beech has always paid attention to reducing noise and vibration, something pilots and passengers appreciate over the course of a long day of flying.

Cockpit layout is a point of departure from previous Beech designs. The power controls are arranged conventionally-throttle, prop, mixture-rather than Beechs traditional props-throttles-mixtures arrangement. Gone, too, is the throwover yoke idea and the engine instruments are arranged in a column right of the flight instruments, a more modern approach picked up for later model Bonanzas. For avionics upgrades, the panel is spacious enough, although owners will have to plan carefully. (The aforementioned instrument clusters cant really be easily moved to accommodate large displays, so the center stack is considerably more to the right than it is in other airplanes.)

Ground handling of the Duchess, particularly with full fuel tanks, has been described as ponderous. The soft main gear oleos allow the airplane to lean to one side or the other when making corners. Injudicious stabs at the brakes can make the nose bob. These traits have probably contributed to the Duchess record of taxi incidents. Our previous review of the model revealed numerous instances of pilots running over taxiway depressions and catching the prop tips and in a surprising number of cases, Duchesses incurred ramp rash by dragging their wingtips across parked aircraft rudders. Our more recent examination of the accident record, including accidents that occurred right through 2005, revealed no such instances. Perhaps owners have learned to accommodate the airplanes foibles.

On the runway, the Duchess has no real vices, although the powerful control forces of the T-tail-mounted elevator invite a tail strike through over-rotation. However, we dont see reports of this and owners tell us adapting to the T-tail is not difficult. While owner reports on the Piper T-tails are mixed, the Duchess doesnt seem to suffer such a reputation.

In-flight handling is one of the Duchess strong points. Owners seem universal in their praise of the airplanes docile handling characteristics.Its far more benign than other twins with either one or both engines running. The controls are well harmonized and light in feel. The aircraft is stable in pitch and roll, although some complain of a bit of tail wagging in turbulence, perhaps a consequence of the tail design itself. Single-engine handling is excellent, even if single-engine climb rates are not. And Beech provided enough trim for all three axes to trim away all or most of the control forces. Because the Duchess has counter-rotating engines, theres no critical engine to worry about, which we see as a positive safety trait. Shut down either the left or right engine and the airplane handles just the same.Blue-line is a reasonable 85 knots, one of the slower numbers for twins in general.

Slow speed handling is also good. Stalls are straightforward and controllability is good right down to the break. With power on and gear and flaps down, you can get the Duchess below the 50-knot mark and still maintain reasonable control authority with both engines turning. The same cant be said of most twins.

Configuration changes hold no particular worries. The gear goes out at speeds up to 140 knots and owners say theres no noticeable pitch change with either gear extension or flap extension. Worth noting is that theres a big spread between maximum gear extension speed and maximum retraction speed, 140 knots and 113 knots, respectively. The forward-retracting nose gear is the culprit, since it has to fight the wind on the way up.

Maintenance, ADs
The Duchess record on ADs isnt exactly spotless, but theres nothing thats horribly overbearing, either. Indeed, consider that the Duchess has managed to accumulate only a handful of ADs since its introduction; almost all of those after the early 1980s were shotgun ADs on the engines.

The most recent significant Duchess-specific AD (originally released in 1991) is 97-6-10 and also the only repetitive one with no terminating action.This AD calls for dye-penetrant inspections of the main landing gear A-frames every 100 hours. The inspection itself is not terribly difficult, but preparation and cleanup are time consuming. If cracks are found, the parts must be scrapped and new ones installed-and the 100-hour inspections continue even with the new parts.

As twins go, maintaining a Duchess is not as burdensome as, say, a Baron or a Cessna 310. Its altogether a simpler airplane. The Lycomings have a good service reputation and the weak-link parts on the airplane that tend to break arent expensive. But be warned: Beech parts prices are among the highest in the industry, although Raytheon recently announced rollbacks.

Owners tell us to check gear actuators for leaks and wear. As with any retractable, the gear system demands inspection and maintenance. Checks of everything from landing gear actuator seals to rod ends to support channels should be taken seriously at every annual and definitely before purchase. We dont hear a lot of complaints about gear problems in the Duchess. The most common gear problem was pilots forgetting to put the wheels down, followed by pilots forgetting they had retracted them, with pilots retracting the gear prematurely on takeoff bringing up the rear.

Several owners said starters can hang up, damaging the starter motor and ring gear. A starter-engaged light addresses this. There are also complaints about failed alternators but, increasingly, better quality starters and alternators are available for Lycomings. Also, check for chafing of hydraulic lines against heater ducts under the copilots seat.

For support and technical questions, in addition to Raytheon/Beechcraft (www.raytheonaircraft.com), try the Beech Aero Club at www.beechaeroclub.org. Although it doesnt specifically support the Duchess, another valuable resource is the American Bonanza Society. (See www.bonanza.org.)

Reader Feedback
I own a 1980 Duchess with 6100 hours (half of its 12,000-hour life limit). I have owned it from 1982 when it had about 700 hours. I have been through 2 1/2 engine overhauls. The half engine overhaul was due to the need to tear it down mid-time because of a broken intake valve that was going to cost more than half the price of the overhaul. The engines are normally overhauled at 2200 hours, but have been in good working condition at the time I chose to overhaul them. The aircraft has been used as a trainer all of its life. I believe that this contributes to worse-than-desired tire and brake wear.

I have budgeted $3500 per 100 hours for maintenance, not including engine and propeller allowance. Fuel consumption is about 18 gallons per hour but I plan on 20 GPH for safetys sake and for ease of estimation. With full tanks, it will hold 653 pounds of people and stuff. The large rear door and easily removable rear seats are nice features.

There have been several renovations of the avionics over the years, with the airplane currently having a Garmin GNS430 with WSI weather, an S-TEC System 60 autopilot with GPSS and altitude pre-select, a Sandel 3308 EHSI and the NSD360 HSI demoted to be the second CDI. It also has a FMS5000 loran/GPS and a KNS81 along with an ADF and dual transponders. No excuse to get lost and the customers love to rent it for cross-country trips. When I fly it personally, I have a CT1000 EFB as well.

Last summer, it got repainted at Keyson in Nashua, New Hampshire with the design done by Scheme Designers. The interior seats have been redone a couple of times. The last time it was totally redone, I requested enough extra material to redo the front seats because nobody wears out the rear seats, so I saved half when I redid it recently. The plane has been hangared since about 1990 and that has helped a lot.

Over the years, I have figured out what parts wear out regularly and I keep spares on hand. One of the main ones that you need right away are the flush drains on the wing. Also, the electric boost pumps have been a recurring problem, although Beech has recently changed the part number and hopefully improved them.

The main door handles have some wire springs that eventually rust and break and are very expensive to replace, but not nearly as expensive as the rear baggage door plastic one. For the most part, Beech has been very good at providing parts and support for an airplane that has not been manufactured since 1982.

The plane flies great and is a very stable instrument platform. I typically file for 155 knots. It is very easy to land and engine failures are very tame.

Thomas Hirsch
Bedford, Massachusetts


Also With This Article
“Beechcraft Duchess Charts and Specs”
“Accident Scan”