When the owner of a single-engine airplane starts thinking about twins, hes liable to begin not in the cheap seats but with something pricey and fast, perhaps a Baron or a cabin-class Cessna. But putting a sharp pencil to the equation usually points the would-be twin driver at something more realistic and often, a Piper Seneca fills the bill.
As we’ll it should. The venerable Seneca is available in several models so there’s wide price stratification, its got decent if not blistering speed and it carries a fair load on a reasonable fuel burn. In short, the Seneca doesnt excel at anything but does everything reasonably we’ll at an affordable price. And therein lies its popularity and the explanation for why its one of only three piston twins still in production. (The Raytheon/Beechcraft Baron and Piper Seminole are the other two.)
The Seneca is suitable for both a twin-engine trainer and step-up two-engine ride for an owner who needs the power and wants the redundancy of a pair of motors.
Model Background
Few manufacturers have gotten as much mileage out of similar airframes as Piper has. The Cherokee line begat the Cherokee Six, the Six the Saratoga and the Saratoga the Seneca. The Seneca is basically what you get when you turn a Cherokee Six into a twin, sharing the trademark Hershey-bar wing, the stabilator empennage and fuselage of the Cherokee Six and the same spacious cabin, with available club seating.
The first Seneca was introduced in 1971 at the height of the general aviation boom to serve as a lower cost and larger companion to Pipers successful but aging Aztec and replacing the even older Twin Comanche in the Piper lineup. The Seneca had counter-rotating Lycoming IO-360C1E6 engines producing 200 HP each.
When it appeared, the Seneca cost about the same as the Twin Comanche C/R but it had larger engines, higher gross weight and a roomier cabin with a rear door that the Twinkie lacked. Both the Seneca and the Twin Comanche were built in 1972 but when Tropical Storm Agnes pushed the Susquehanna River into the Pipers Lockhaven works, the Twin Comanche was no more. (The Seneca was built in Florida.)
Piper built 360 Senecas that year, a good start in the twin market and a total equal to twice as many Twin Comanches built between 1970 and 1972. The competition at the time was the Cessna Skymaster, which sold poorly in 1972, at only 63 units. In three years, Piper churned out 933 Seneca Is. Compared to the Comanche and even the Aztec, the Seneca was a distinctly modern airframe and much effort went into making the airplane pilot friendly. It had counter-rotating props, eliminating the critical engine worry, which made training more safe and general operations less nerve wracking.
Compared to the Comanches Byzantine plumbing, the fuel system was a snap, only three positions to tanks feeding from both sides: on, off and crossfeed.
Like the wildly successful PA-32 series upon which the airframe was based, the Senecas cabin was long and wide, with seating for six, a big aft door on the left and a cockpit door on the right. Since passengers don’t like climbing over wings, this design proved a favorite among charter operators and for owners with big families.
And despite its boxy shape, Piper applied some styling touches to make the aircraft fairly attractive. Early interiors, apart from that unfortunate Velour upholstery, were also a step up from early efforts.
Improvements
The original Seneca wasnt exactly the best handling airplane Piper ever built. The controls were heavy, partly because there were a lot of add-ons in the control system such as an aileron/rudder interconnect and a down-spring for the stabilator. The ailerons werent big enough and pitch stability wasnt great, either.
Taken together, this gave the airplane a pronounced Dutch roll in turbulence and when configured for approach, the tailwagging was bound to give the passengers queasy stomachs.
Also, the cabin noise level was high and the engine vibrated enough to cause spinner to crack and some departed in flight. ADs followed. A lot of ADs. Records indicate that the original Seneca is subject to 47 ADs, counting the shotgun ADs that apply to most airplanes; a dubious record of sorts.
But Piper got busy and quickly corrected the Senecas handling and noise/vibration shortcomings. The ailerons were changed to a modified Frise design and made larger. The engine mounts were changed and soundproofing was added.
Piper also changed some of the weights to give pilots the option of carrying more weight or more fuel. Gross weight was increased from 4000 to 4200 pounds. The increase carried with it a price, of course (there is no free lunch, after all): Single-engine performance at the higher gross weight was marginal, at best. Single-engine rate of climb sank from 230 FPM to 190 FPM and single-engine ceiling from 5200 feet to 3650 feet. Piper also introduced a new limitation: a zero-fuel weight of 4000 pounds. In other words, any weight over 4000 pounds had to be in fuel, not payload.
Still Not There
Although these improvements were welcome, the airplane still wasnt as good as it could be. (Are they ever?) Starting in 1975, Piper made more alterations and produced the PA-34-200T Seneca II.
More changes were made to the control system to improve handling. The aileron/rudder interconnect was removed and with it went some control heaviness. The rudder gained an anti-servo tab and the stabilator was changed with the addition of a bobweight. The ailerons were increased in span and balanced for lighter effort. This time, the changes worked and no major alterations were made after that.
But the big performance change for the Seneca II came in the powerplants, with the four-banger Lycs giving way to six-cylinder turbocharged Continental TSIO-360-E engines with fixed waste gates. Rated at the same 200 HP at sea level, they produced 215 HP at 12,000 feet.
Flying high and fast is nice, of course, but twin drivers worry more about high-altitude engine-out performance. Here, the Seneca II was a different beast entirely.
Single-engine climb rate improved to 235 FPM and single-engine ceiling more than tripled to 13,400 feet. Initial recommended TBO was the same 1400 hours. In 1977 this was increased to 1800 hours and owners report that with careful operation and maintenance, this is realistic.
The airplane got a higher gross weight, too, increasing by 370 pounds to 4570 pounds; however, the zero-fuel weight stayed at 4000 pounds, so the benefit was a mixed blessing. Another limiting weight was introduced: a maximum landing weight of 4342 pounds. Once again pilots were given more flexibility and more ways to get into trouble if the loading limits were not obeyed.
With the improved controls and engines, the Seneca II also got optional extended-range fuel tanks that increased usable fuel from 93 to 123 gallons. This increased range with reserves from 575 to 820 miles at 65 percent power at 10,000 feet.
The campaign against noise and vibration continued with the addition of a three-bladed prop option, which weighed 46 pounds. The popular club seating option was introduced, as was a Janitrol heater and optional fan to move heated or ambient air through the cabin.
In later years, some system changes and options were added, such as a priming system to make engine start easier, optional more powerful brakes, modifications to the instrument panel and air conditioning. In 1980, a built-in oxygen system was offered.
More Upgrades
In the late 1970s and early 1980s, Piper overhauled its entire model line, introduced the tapered wings and had a fling with T-tails. The 1981 Seneca III was supposed to have the same T-tail and tapered wing as the Lance but Piper found that the flying qualities werent as good as the company had hoped. The configuration was left unchanged.
There were significant changes to the Seneca III, though. A different variant of the Continentals was used, with 220 HP each. These engines had a higher RPM limit (2800 vs. 2575 RPM). This, combined with fuel scheduling, resulted in maximum power of 220 HP, albeit time limited to only five minutes.
Continuous rated power was still 200 HP. Single-engine rate of climb improved marginally to 240 FPM and all-engine rate of climb went from 1340 to 1400 FPM. However, most other performance figures, such as runway required, declined somewhat due to a further increase in allowable weights.
The new weight limits were made possible by reinforced structure. This time, the zero-fuel and landing weights were raised as well. Maximum takeoff weight was now 4750 pounds, zero-fuel weight 4470 pounds and max landing weight 4513 pounds.
The pneumatic system (for air-driven instruments and optional de-ice system power) was changed from a pressure to a vacuum system in 1981. According to Piper, this improved mean time between failure from an average of 400 hours to more than 700 hours. Owners say that in the field, the pressure pumps last about the same as vacuum pumps.
Other changes to the Seneca III included a new panel, one-piece windshield and a switch to electric flaps. Weve always been fans of manual flaps: theyre simple, positive and hard to break. The move to electric flaps was required because of a change to larger flaps, which resulted in high actuation forces.
Amazingly, the Seneca never went out of production, even during Pipers troubled times in the late 1980s and early 1990s. Admittedly, production was down to a trickle (four were built in 1992), but it stayed on the price lists. And its still there.
As part of Pipers transformation into New Piper, the Seneca was revamped yet again, being redubbed the Seneca IV and lately, the V. Relatively few changes were made, the most notable being new cowlings that result in higher speeds.
Also, the interiors have been markedly improved in recent models. Along with these improvements come much higher prices: When the Seneca IV was introduced in 1994, it sold for about $425,000. A new Seneca V retails in the $583,000 range.
Performance, Loading
All of the Senecas offer fairly good short-field performance and sea-level fields of 3000 feet or so are no problem as long as both engines are turning. As noted above, however, later versions are much better once airborne. Of all the light twins, the Seneca is among the most benign in the runway environment.
Its not a super-fast airplane, however. The normally aspirated early models cruise in the 160 to 170 knot range at 65 percent and 10,000 feet. Limiting speeds are low, however: 129 to 130 knots for gear extension; 138, 121 and 107 knots for 10-, 25- and 40-degrees flaps, respectively. One owner we spoke to highly recommends that speed brakes be fitted.
The turbocharged models are, of course, quite a bit faster, especially when taken high. Owners report cruise speeds in the 180-knot or faster range in the high teens and low flight levels on typical fuel flows of 24 to 28 GPH.
The later Senecas are decent haulers. Loading the Seneca is about as easy as it gets. The fuselage is low to the ground, allowing rear passengers to climb on board easily and the rear seats are easy to remove. The two baggage compartments have weight limits of 100 pounds apiece. The generous CG range permits flexibility in seat selection and the later models were equipped with a clever slide-rule type CG computer which makes loading a snap.
Owners tells us that early Senecas have useful loads in the 1200- to 1300-pound range while the Seneca II averages closer to 1500 pounds, with its higher gross weight of 4570 pounds. The latest iteration, the Seneca V, has regressed due to higher empty weight, with useful loads in the 1300- to 1400-pound range.
Cabin and Comfort
With its four-foot-wide cabin, adequate seating for all but the biggest of six people, and ample windows, the Seneca is long on comfort in comparison to most other piston-powered airplanes in this class. Although the club seating often yields a tangle of legs in the rear cabin, its much appreciated by passengers. Given its payload, the Seneca is a good five-person airplane with some baggage or a four-person airplane with a lot of baggage.
Flight visibility from the cabin is adequate but not exceptional. The big windows are nice but up front, the large engine nacelles extend forward of the wing leading edge, blocking horizontal and downward visibility. This, coupled with the wide-chord wing, makes spotting traffic below the airplane difficult.
Heating and ventilation are typical Piper, with overhead and floor vents that provide enough air in most circumstances. Seats are also typical Piper, which is to say reasonably comfortable but with a tendency to sag and wear with use.
ADs
The Seneca has had its share of airframe-specific Airworthiness Directives. Many of these were one-offs, but there are some repetitive ones to be aware of:
72-14-7 calls for 100-hour inspections of the stabilator fittings on original Senecas.
72-17-1 is a 100-hour inspection of the induction airbox valve on the PA34-200.
73-14-2 calls for 25-hour inspections of the PA34-200s exhaust system.
82-27-3 for those airplanes fitted with Rajay turbochargers, calling for inspection or replacement of the turbine housing each 200 hours
92-08-4 is a repetitive inspection of the aluminum rudder torque tube fitting. Replacing it with a steel fitting eliminates the inspection.
95-20-7 is a repetitive inspection of the main landing gear side brace strut.
AD 98-21-21 R1 requires modification of Bob Fields inflatable door seals.
AD 98-19-02 addressed Superior piston pins in TSIO-360 engines.
AD 2002-13-04 was an emergency AD to address magneto stop pins.
AD 2002-09-08 requires inspection of Hartzell Y-shank prop blades.
Mods, Owner Groups
Senecas beginning with the II came with fixed wastegate turbochargers. These are relatively simple and inexpensive to manufacture but at the cost of efficiency and longevity and a tendency to overboost due to sensitive throttle response.
Owners say a must-have mod is to fit the engines with Merlyn automatic wastegates. Weve heard good reports about these mods and other owners tell us intercoolers can also help.
Due to the low speed restrictions, speedbrakes are a good investment, particularly in heavy traffic areas. Precise Flight makes a set for $3295. Contact: 800-547-2558.
For Seneca I owners who want turbocharging, the old Rajay is found on used models but no longer installed. TradeWind Turbines (806-335-1400) may have parts.
Seneca II and III owners can improve their turbos with Turboplus intercoolers in kit form. Contact 800-742-4202.
Although the takeoff and landing numbers on the Seneca are decent, those who want better performance can invest in Sierra Industries R/STOL kit Call for pricing and expect a long lead time. Contact: 830-278-4381 for more information.
Hartzell Propeller has two STCs to install three-blade propellers on the Seneca II and III. The STCs can replace either two-blade Hartzell or three-blade McCauley propellers. The propellers can besupplied with electric de-ice boots installed and includes all the necessary hardware to convert from the existing two-blade Hartzell or three-blade McCauleyde-ice system. The three-blades offer better take-off and initial climb and also eliminate the RPM/MP restriction applicable to the two-blade propellers. Contact Hartzell at www.hartzellprop.com.
The Piper Owner Society supports Seneca buying and ownership, contact 866-697-4737 or www.piperowner.org.
Owner Feedback
My partner and I have owned this aircraft for the past 13 years and find that it serves our purposes well. Over the years, beside the standard aircraft, which has de-ice, we have upgraded the radar to a color radar, added a Stormscope, a Garmin 430 package, stand-by electric artificial horizon, inflatable door seal and in recent years we have put factory re-manned engines in the aircraft, overhauled the propellers, painted the aircraft and installed a new interior.
We were able to run both of the engines to almost 2000 hours without ever having cylinder heads off or anything done to these engines. Needless to say, we have been delighted with the aircraft.
Besides our annual inspection, every 50 hours we do anoil change, we have the spark plugs cleaned and gapped and have the timing checked. The reason this is done is that soon after we bought the aircraft, we lost one of the engines and, in talking with Continental, which was not a pleasant experience, they advised us the aircraft had not beenproperly maintained.
When I questioned them about this, they recommended the 50-hour inspection of their magnetos, the gapping of spark plugs in order not to have the magneto short out, which caused the original engine to be destroyed.
One final note: When we put the factory re-mans in the aircraft, the compression in all 12 cylinders was above 65 PSI and most of them were above 70 PSI. As far as operating expenses are concerned,we fly the aircraft at 2300 to 2400 RPM andmanifold pressure between 29 and 31 inches.
At 2400 RPM and 30 inches at 9000 feet, the aircraft trues at 176 knots. At 12,000 feet with the same settings, the aircraft trues at 181 knots. Fuel burnnormally runs between 24 to 25 GPH at either one of these settings in both engines.
About eight years ago, the aircraft was valued at $140,000.I did a survey for two years and found that total operating expenses, including insurance, hangaring, maintenance and training came to about $175 per hour. This includes a return of 6 percent on the value of the aircraft, which was included in the cost.
I am quite certain that if we did it now, it would be up at least $25 to $30 per hour with the increased cost in fuel and other items.
The aircraft is used both for a corporate aircraft and a pleasure aircraft, which normally runs up to 600 miles around the Kansas City area. We have found it to be an excellent all-weather aircraft and the drawing point for our customers is the club seating in the back of the airplane and ease of entry.
The aircraft is flown approximately 150 hours per year. While it may not have the name of a Beech Baron, we find that the vast majority of the time we can fly with the Barons for less money. My partner and I have owned eight airplanes and we find that this airplane is a wonderful compromise between comfort, speed and utility.
-C. H. Nason
Overland Park, Kansas
I own a 1984 Seneca III. I purchased the Seneca after my 1985 Saratoga ran out of power at 13,000 feet climbing in icing over the Rockies. I had been happy with the Saratoga until this flight. But now saw limitations.