Over the years, few light aircraft manufacturers have managed to get as much mileage out of existing airframes as Piper. Vero Beach produced seemingly endless variants of the basic PA-28 Cherokee-everything from simple trainers to T-tailed turbocharged retractables to light twins, all of which were recognizably based on the same airframe. Pipers larger single, the PA-32 Cherokee Six, was also transformed into several different airplanes over the years.
History
The PA-34 Seneca is, basically, what you get when you turn a Cherokee Six into a twin, sharing the trademark Hershey-bar wing, stabilator empennage and fuselage of the Cherokee Six. The Seneca had counter-rotating Lycoming IO-360C1E6 engines producing 200 HP each.
It was introduced in 1971 at the height of the general aviation boom to serve as a less-expensive companion to Pipers successful but aging Aztec (it was about a third less costly), replacing the Twin Comanche in the lineup. The Seneca was about the same price as the Twin Comanche C/R, while sporting larger engines, a higher gross weight and a roomier cabin. Both the Seneca and the Twin Comanche were built in 1972, but the latter was discontinued afterwards, albeit in part due to the flooding of Pipers Lock Haven, Penn., factory that year. (The Seneca was built in Vero Beach, Fla.)
That first year showed that Pipers move to replace the Twin Comanche was the right one. Piper built 360 Senecas that year, more than doubling the combined production of the PA-39 Comanche for 1970, 71 and 72. The only twin of similar power on the market at the time, the Cessna Skymaster, sold only 63 units in 1972. The first three years of Seneca production totaled a healthy 933.
To Pipers credit, a lot of effort went into making the Seneca user-friendly for both pilots and mechanics. It had counter-rotating props, thereby eliminating the critical engine-a bonus for training and overall safety. Maintenance access was considerably improved over the Twin Comanche, which had been designed in the 1950s. The fuel system was simplified, with only on, off and crossfeed to deal with.
The Seneca benefited from some of the better features of the PA-32 on which it was based. The cabin was long and wide, with real seating for six, a big aft door on the left and a cockpit door on the right, making for ease of loading. That appealed to charter outfits; passengers tend to dislike climbing over wings and seatbacks to get on board. Loading, too, was easy thanks to baggage compartments fore and aft.
Piper even managed to make the airplane fairly attractive, despite the hard-edged fuselage and fat, rectangular wing.
The original Seneca was less than stellar when it came to handling in flight. The controls were decidedly 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. Pitch stability wasnt very good, either.
The result of all this, in addition to heavy handling, was a pronounced Dutch roll tendency especially in turbulence and when configured for approach.
To make it worse, the engines vibrated badly (enough so that some airplanes lost spinners in flight due to cracks), the noise level was high, and to add insult to injury there were six ADs on the airframe in the first two years of production, three of which were repetitive.
Its a tribute to Pipers marketing expertise and the airplanes good points that it was so successful in spite of the problems.
Piper acted quickly to correct 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 more soundproofing was added. The changes helped, though the airplane was still fairly heavy.
The company also changed some of the weights to give pilots the option of carrying some 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 became marginal at best. Single-engine ROC sank from 230 FPM to 190 FPM and single-engine ceiling from 5200 feet to 3650 feet. It also introduced a new limitation: a zero fuel weight of 4000 pounds.
The airplane still wasnt as good as it could be, though, and so in 1975 Piper made some 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. The rudder gained an anti-servo tab. The stabilator was changed, and a bobweight added. The ailerons were increased in span and balanced for lighter effort. This time, the changes worked, and no major alterations were made after that.
The big change for the Seneca II, though, was the switch to turbocharged engines. The four-cylinder normally aspirated Lycomings were replaced with 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 12000 feet.
While the new engines were good for better mission profiles due to the ability to fly higher, the biggest benefit came in engine-out performance. Single-engine ROC 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.
The weights were upped again by altering the landing gear and wing center section. Gross weight increased by 370 pounds to 4570; however, the zero fuel weight stayed at 4000 pounds. Another limiting weight was introduced: a maximum landing weight of 4342 pounds. So, once again, pilots were given more flexibility…and more ways to get into trouble if the loading limits were not obeyed.
Several noteworthy options were introduced with the Seneca II. Extended-range fuel tanks were offered that increased usable fuel from 93 to 123 gallons. This increased range with reserves from 575 to 820 NM (at 65 percent power at 10,000 feet).
A further attack on noise and vibration came in the form of a three-bladed prop option, which weighed 46 pounds. The popular club seating option was introduced. So was a Janitrol heater and optional fan to move heated or ambient air faster in 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.
In the late 1970s and early 1980s Piper began going through its model line and making substantial changes and updates. Starting with the Warrior in 1975, Piper airplanes began sporting tapered wings and other changes. The company also went through a period when T-tails were thought to be a good idea (a debatable point): The results were the Turbo Arrow IV and T-tailed Lance.
The 1981 Seneca III was originally 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 basically 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). 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. 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 and max landing weight 4513 pounds.
The pneumatic system (for air-driven instruments and optional deice system power) was changed from a pressure to a vacuum system. According to Piper, this improved MTBF (mean time between overhaul) from an average of 400 hours to more than 700. Owners say that in the field the pressure pumps last about the same as vacuum pumps, though.
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: simple, positive and hard to break. The move to electric flaps was necessitated, however, because of a change to larger flaps, which resulted in high actuation forces.
As part of Pipers transformation into the New Piper, the Seneca was revamped yet again, being redubbed the Seneca IV. Relatively few changes were made, the most notable being new cowlings that result in higher cruise speeds. In 1997 a different engine variant was fitted and the airplane was redubbed Seneca V.
Performance
All of the Senecas offer fairly good short-field performance, and sea-level fields of 3000 feet or so are no problem (at least as long as both engines are turning). As noted above, however, later versions are much better once airborne.
The Seneca is not terribly fast, though it will get you there. Cruise speeds are in the 160-175 knot range at 65 percent and 10000 feet, with later versions being faster. Limiting speeds are low, though: 129-130 KIAS for gear extension; 138, 121 and 107 KIAS for 10, 25 and 40 degrees flaps, respectively.
On the plus side, single-engine minimum control speed, recommended single-engine and stall speeds are low, which provides useful margins for normal operations.
Loading
The weight increases in later versions of the Seneca dramatically increased the loading options for the pilot. The weight penalty associated with them is only 270 pounds, while the gross weight increases were nearly three times that. Of course, the imposition of maximum zero-fuel and landing weights imposes new limits and could potentially result in no-win situations for the pilot.
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 good CG range permits a lot of flexibility in seat selection.
Accommodations
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 a lot of other piston-powered airplanes. The comfort goes beyond inches and cubic feet; even people sitting in the last row-thanks to roominess and generous windows-have the illusion of space, too.
Another characteristic of the Seneca is its visibility limitations. The big windows are nice for the passengers, but up front the large engine nacelles extend well 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.
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.
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.
Wastegates
Senecas starting with the II came with fixed wastegate turbochargers. These devices are relatively simple and inexpensive to manufacture, but at the cost of efficiency and longevity. There are some ways to deal with the problem. First and foremost is careful temperature management.
A better choice is to fit the relatively new Merlyn automatic wastegates. We have some reports that they do the job and are well worth the investment. Intercoolers can also help.
Safety
The Seneca was designed to be less demanding than the airplane it replaced, the Twin Comanche, and it is. The latter airplane had a poor accident record when flown by low-time pilots. Given the Senecas heavy handling in earlier versions and low speed limits, we wouldnt have been surprised if the Seneca racked up a heavy accident toll. But it never did.
Clearly, for all its faults, the Seneca is a pretty forgiving airplane. Pilots have lost control in low-speed operations and crashed, but not to any alarming degree. Perhaps in that respect Piper did overcome the performance and reputation of the Twin Comanche in training and in the hands of low-time multiengine pilots.
Mods
Apart from the Merlyn waste gates already mentioned, there are several noteworthy mods available.
Due to the low speed restrictions, pilots tell us that speed brakes are a good investment, particularly in heavy traffic areas. Precise Flight makes a set.
For Seneca I owners who want turbocharging and can pay for it, a kit is made by Rajay. Seneca II and III owners can improve their turbos with Turboplus intercoolers.
Though the takeoff and landing numbers on the Seneca are already pretty good, those who want better performance can invest in Sierra Industries R/STOL kit.
Prime choice
The Seneca is not the fastest twin, nor does it have the longest range or largest load lifting capacity. But it has a good mix of these traits. One of its major strengths is that passengers like it. Another is that it is economical compared to other twins with its capabilities. Pilots wishing to opt for two engines would do well to take a look at it.
Owner Comments
I am a judge in the Yukon Territory in Canada. I have owned a 1977 Seneca II for over 12 years. The aircraft is used by me to fly to court circuits in outlying settlements, and by my partner, who is a doctor, to fly to medical clinics in some of the same settlements. Both of us previously owned single-engine aircraft, but too many weather cancellations and a big pucker factor flying IFR in a single in mountainous terrain, led us to the Seneca. Although not cheap to buy or to operate, a de-iced Seneca with weather avoidance equipment is, I believe, the least expensive aircraft that is really useful for on-time transportation.
The Seneca is not fast and the handling is hardly fighter-like. However, it has a good safety record and has always brought me home through all kinds of weather. In our neck of the woods, one can encounter icing twelve months of the year and the Seneca handles it very well. It is able to get in and our of short strips, although gravel rash on the props is a problem if youre not careful.
We always fly at 65 percent power at altitudes of 10-15000 feet. TAS is 165 knots burning 22 GPH. Costs of operation (converted to US dollars) include $4500 for insurance (liability and $100,000 hull), and annuals at $3500. Prop overhauls every five years for de-iced props are $3500-$4000 each. Turbos last 500-700 hours at $2000 a throw. Pressure pumps have about the same life at $900 for rebuilts. ADs on the landing gear have been the biggest unscheduled expense.
The TSIO-360 engines have a reputation for hot running and top-end distress due to the fixed wastegate turbos. We exceeded TBO on both engines with no problem. Our experience may (or may not) be due to the following:
1) Both engines were factory remans
2) Engines run at 65 percent power and TIT never above 1575 degrees
3) Regular use
4) Gradual power changes
5) Aircraft operated by only two pilots who understand how touchy the throttles are and are responsible for the repair bills
6) Fairly low OATs here keep cylinder head temperatures down.
Problem areas in the Senecas include the aforementioned landing gear and repeated fiddling with the voltage regulators to keep the alternators balanced. The Janitrol heater requires yearly inspection. Ours lasted 4000 hours, probably a world record, then required replacement with a rebuilt for $3000. Biggest constant problem is high altitude misfiring due to the unpressurized magnetos. Fine-wire spark plugs (cleaned and gapped religiously every 50 hours) and impeccable mags and harness help. One cannot predict when the problem will occur since the engines run fine on the ground and below 10,000 feet. The only in-flight solution is to descend, or if that is not possible, to go to maximum RPM and decrease manifold pressure until smooth running is obtained. This may mean reducing power to 20 inches or less, but at least youll keep the pistons and con rods inside the cowls where they belong.
In summary, I have been pleased with the Seneca in over 2500 hours of operation. Like most airplanes it would be perfect if it carried another 300 pounds and cruised 30 knots faster.
-John Faulkner
Whitehorse, Yukon, Canada
I have a 1979 Seneca II, purchased in 1994. I moved into this from a 1977 turbo Arrow due to its similarity and ease of transition. In a twin, I wanted known icing, weather detection and a second engine, in that order. I also wanted a twin that was relatively forgiving, i.e., counter rotating props, simple fuel system, turbocharged, small enough to fit in my hangar, relatively inexpensive to acquire and similar to what I was flying. The Seneca fit the bill. Although I wished for pressurization, that was a jump I was not willing to make financially.
We purchased the aircraft with factory reman (Chevron) engines, new intercoolers, paint=8, interior=8.5, deice boots=9, excellent condition mechanically, but a horrible and dysfunctional instrument panel.
We installed Merlyn automatic waste gates, Shadin fuel flow, GEM 1200 multiprobe EGT, CHT, TIT, speed brakes, wingtip taxi/recognition lights, and a new instrument panel replacing everything except the IFR KN88 Loran. The new panel included King radios (navcoms, DME, ADF, HSI, transponder) , Argus 7000, Strikefinder, and digital manifold pressure and RPM gauges located high on the instrument panel above the attitude indicator. We overhauled and internally lit the flight instruments placing them in a metal panel. This all cost us approximately two-thirds the acquisition cost of the airplane. But other than radar and a radome and GPS in the future, Ive modified the plane about as much as I need.
The plane is great compared to the Arrow-plenty of room, great short field take-off performance, excellent weight carrying ability (with both engines running), and good climb performance. I wish it was faster, but I plan for 165 knots at 10,000 feet.
We fly the plane approximately 150 hours a year. Costs are the following based on that 150 hours a year, living in California, with a husband and wife pilot with 1000 hours each of turbo retract time, 20 hours each of Seneca time, at the time of acquisition of the Seneca.
Hangar: $3900 per year (at an expensive California airport)
Engine & prop reserve: $28/hour
Insurance: $3000 per year initially, now $2400 per year with little likelihood that it will decrease significantly from that point
Gas: 25 gallons per hour: 75% power with approximately 1 gallon per hour each side enriched over a more frugal fuel setting (dont count on flying this on less unless you want serious maintenance bills in the future). If you buy the balanced fuel injectors, I do believe you can get the fuel flow down a few gallons per hour, but they are expensive and Im not sure how balanced they will be after a few hundred hours despite ultrasonic cleaning. If anyone has experience with this, I would love to hear about it.
Aircraft tax: $850 per year
Maintenance: a very difficult number. I have a CFI/IA mechanic work on the plane in my own hangar which I equipped for that purpose. To completely set up a hangar to do virtually everything you want to do to the plane short of major sheet metal work is relatively inexpensive , probably less than $5000. There are many good aviation mechanics out there who would love to moonlight for you if you treat them well. Pay them very well and youll still save $20-$25 per hour in labor costs, plus parts for cost and an accurate hour labor count. If you equip your hangar as I did, the money you save will pay for it within one year guaranteed.
Once you bring the aircraft up to specs, the costs are quite minimal working on it in this setting. Annuals approximately $850 and additional yearly routine and surprise maintenance less than $2000 annually. God help you if you need to do this through an FBO. Using my Arrow experience initially with FBOs and adding an additional engine, known icing, and the Janitrol heater, figure $4000 annuals minimum, and $7500 per year additional maintenance. This is assuming you really maintain the aircraft per book. Again these are California numbers. I frankly wouldnt own one if I had to maintain it in an FBO environment. Some comments on the aircraft and its mods:
1. The auto waste gates are worth the reasonable $1200 apiece with quite simple installation. It decreases significantly the sensitivity of the power settings and seriously increases the critical altitude of the engines. It keeps the temperatures way down.
2. Speed brakes are a must. This plane is no speed demon, but when you put the nose down, it picks up speed real fast and the 129 knot landing gear extension speed doesnt cut it with your dear approach controller. So unless you want to shock cool these engines, you need a way to slow down. I initially told myself that careful flight planning and descent/power management would do it-but a few flights IFR into Class B told me otherwise. The kit is cheap ($4000) for what you get, but the installation is a nightmare. The factory wont install them anymore, they just sell the kits. I believe its because it costs too much to install them. My mechanic took 80 hours, but this was his first time and hes an artist/fanatic. So figure your friendly FBO will charge you at least $5000 for the installation.
3. Pressurized magnetos are very important. The little kit to run pressure from the upper deck to the mags is nice, but make sure you have the real pressurized mags in the plane. These have multiple gaskets including harness gaskets. Many of the Senecas have the kit, but the mags arent sealed and they leak like sieves. Also superb ignition system maintenance is critical if you expect to fly this plane above 16000 feet. The plugs must be clean, gapped to .016, with good harnesses. That means you need to clean and regap these plugs approximately every 75 hours at the latest, otherwise the high altitude misfiring is real annoying regardless of how good your pressurized mag system is.
4. In my opinion a good multiprobe CHT, EGT, TIT and digital fuel flow is really essential to fly these turbocharged engines to TBO. My turbo Arrow got there, but only with very careful mixture control and care to avoid shock cooling. I dont know how you would reasonably lean these engines with the two EGT (really TIT) probes that Piper supplies.
5. The plane is equipped for known icing but the boots are no panacea. Ive been in moderate icing with them and dont like it. The equipment allows you to get out of the icing, fly legally and shed some ice, but dont count on staying in it for long. I only go when I know I have an out, i.e., higher altitude, layers, a non-icing floor, or at the most a light icing forecast. I dont want to be in this plane with severe icing, freezing rain, or even real moderate icing.
6. The alternators are a pain to keep balanced. Also the 60-amp output is barely enough once you start flipping significant switches. You need to keep an eye on the output especially if you have your hot props on.
7. The recurrent trunnion inspections are a pain but I dont feel like paying the $2000 to replace them yet.
8. If the plane doesnt have built-in oxygen, its okay because Piper sells a 50 cubic foot sky ox bottle you mount between the pilot and copilot seats, by removing the relatively useless entertainment center. It has a great mount, is very easy to remove from the airplane to refill and saves you tremendously on oxygen compared to having the built in system recharged. You can put a 2- or 4-place regulator on it and Nelson oxygen systems have adapters to convert it easily to a 6-place system.
9. The door seals need upkeep and an inflatable door seal doesnt cure all the problems. You still need to fool with the seals.
10. The heating vents are unbalanced in the aircraft. If you dont want to melt up front, the passengers will freeze. I believe the solution is to cut another set of vents into the system under the back seats. This way, you can close the two most forward sets of vents, and everyone will be comfortable. I am just about to do this, and actually got the idea from a previous responder in aviation consumer. All in all it is a very good light twin for serious cross-country traveling with reasonable performance. It is relatively economical and we (and our mechanic) are very happy with it.
-Gary Cecchi
Concord, Calif.
Also With This Article
Click here to view charts for Resale Values, Payload Compared and Prices Compared.
Click here to view the Piper PA-34 Seneca features guide.
