Pilot report - Piper Seneca series

[Reprinted from Fliteguide / Imperial Aviation]

Piper's Seneca is the archetypal light twin. This lofty achievement is shared by one other - Beechcraft's long-enduring Baron - and whilst between them they account for nearly one hundred percent of the current new twin market, they have occupied diametrically opposite ends of the price spectrum.

The Seneca is about as conventional as twins get which is odd given the model's whacky beginnings. It was during the early sixties that light-twin safety aspects were the focus of unwelcome FAA attention. Too many twins had been killing their students and instructors during assymetric training. Piper's PA-30 Twin Comanche had attracted a particularly bad reputation. So much so that Piper eventually fitted counter-rotating propellors, re-naming the aeroplane the PA-39 C/R. Cessna had already launched their 337 push-pull in an effort to solve the problem.

In 1965, Piper decided to lace two 115hp Lycomings onto the wings of their original prototype Cherokee Six. This may seem to have been an anathema to Piper given their low-rent position in the market place and many wondered about the rationale behind such a layout. The 'Cherokee' retained its 250hp engine in the nose. Flight testing proved the obvious - the three-engine layout had little merit, especially as the wing engines couldn't be feathered. It was back to the drawing board and Piper then had the brilliant idea of removing the centre engine and calling it the 'twin-Six' using two 180hp O-360 Lycomings. A second prototype was built with retractable gear and a lengthened tail and the production version, launched in 1972, was given 200 horses a side and counter-rotating props like the C/R Twin Comanche.

Early Seneca's, whilst fulfilling Pug Piper's edict of keep 'em cheap, keep 'em selling, were short on payload, and had an unimpressive single-engine performance. The adaption of the basic Cherokee Six structure only served to keep costs low - handling, was compromised by a rudder/aileron interconnect which served to keep the 'dead-engine' wing high using only rudder input. The controls were thus extremely heavy for a light twin and steering on the ground was also ponderous. In 1973, Piper upped the max gross weight by 200lbs which had the predictable effect of dramatically reducing its engine-out ceiling even further, which at 3,650ft is the lowest of any post-sixties production light-twin ever made.

The arrival of the Seneca II in 1975 was a mighty breath of fresh air. At the II's heart were a pair of turbocharged Continental TSIO-360s, each rated at 200hp. The engines benefitted from from fixed-wastegate Rajay turbos and later 'EB' versions would go to a TBO of 1,800 hours. The effect was dramatic. Payload went up by a further 200lbs, single engine ceiling rose to a heady 13,800 feet and cruise speed leapt from the low one-sixty's to 177 knots at regular altitudes and 191 at 25,000 feet. Fuel capacity was also increased from 95 gallons useable to an optional 123. Bombarded by handling complaints, Piper also included balanced ailerons, a larger horizontal tail and a new rudder anti-servo tab to help if an engine quit. The Seneca II was also smoother to ride in.

In 1981 Piper gave the II a facelift and a added three-blade props and 20hp extra per side, calling their new, improved model the Seneca III. Again there was a payload and speed increase. The III remained in production through the company's bankruptcy years during the early nineties. Production, from 276 aeroplanes in 1981 dropped steadily to 39 in 1987 and to a mere 10 airframes in 1993. The New Piper Company bravely continued and launched the Seneca IV in 1994.

At this point it worth remembering a major if subtle change of Piper marketing dogma that has taken place following the company's emergence from chapter 21 bankruptcy. With the gold-rush era of light aircraft production well and truly over, Piper decided it needed to change its el-cheapo image. The few light-twin buyers around today are less concerned with apron-one-upmanship satisfied by the number of engines attached to their airframe. With the advance of technology, particularly in navigation and the demands of an ever more sophisticated airspace, buyers want greater weather capability, safer cockpits and a more comfortable cabin environment. Throughout the 28 years of Seneca production the gap between Piper's crimpolene-era interiors and today's leather and veneer fittings is huge. The Seneca V is a vastly different aeroplane to the Seneca I and it's here that's found the logic between improving the IV and launching the V. Light twins are no longer an essential upgrade from a single, but are sold as all-weather business Fliteguide, much like a Learjet, Citation or Challenger.

By definition, it's the details that count and it's here that the V is a significant advance. Piper has made a silk purse out of a sow's ear - it has gone significantly upmarket.

In the cockpit Piper has retained the aluminium-finish one-piece panel beloved of airliner makers. The most immediately noticeable changes are the reduction in windscreen depth allowing placement of the engine start switches, magnetos and booster pump rockers to the cabin roof. There's little practical value in this, but it does separate an important switching function. Piper reckon it'll make you feel like you've climbed inside a luxury automobile... I think not... rather It'll make you feel you've climbed into a business jet - a far more attractive proposition. This juggling with switches has a downside which is a reduction in forward visibility. Nevertheless as a subjective improvement it's fine. Indeed Seneca's have never been great aeroplanes from which to see the world go by, the engines dominate the pilots peripheral vision, severly hampering any view to the side and downwards. The only mistake Piper has made is to then raise the central portion of the panel to accommodate a row of annunciator lights, thus further reducing an already restricted view outwards. It's not as if the panel itself is short of room - there's acres of it and the raised glare panel leads to one eye directed forwards over the nose and the other struggling to focus between the two. As an IF platform, its superb, but it doesn't encourage keeping a VFR watch.

The large-face engine gauges have been thrown out at long last, replaced by minaturised business-jet type dials. These may be more difficult to get used to, but tidily seperate the primary instruments from secondary gauges. Piper has installed a grandly named Self Check In-line Flight Instrument and Monitoring System. This piece of micro-electronic wizzardry seems at first to be another pseudo-big aeroplane gadget designed to convince pilots that light aircraft are approaching the required skill levels of company jets. However, it has some convenient features. The system enables the pilot to adjust rpm and manifold pressure to accurate numerical settings. The value of this facility in a light
twin is doubtful, for no other reason than current piston-engine technology isn't sufficiently sensitive to require such accurate power settings. Moreover, the Seneca V's throttle levers, even with the friction off, are too stiff and clumsy to match even using the rpm gauge. For those that enjoy fiddling and achieving absoulte precision, this facility will keep them amused for several minutes once established in the cruise.

Of greater value is the fuel computer, and Turbine Inlet Temperature monitor all combined in the same unit. This will give a fuel and time remaining solution and will signal a warning if the TIT exceeds its preset value. The system will also give you an OAT reading and will measure the temperature in the cabin too. A glaring omission, and one that would be a real asset to any safety and cost conscious owner, is an electronic engine monitoring facility. At an installed cost of around US$2,000 it should be fitted as standard in any brand new twin. Nevertheless, the Seneca V has a high level of standard equipment including a number of other useful gadgets and switchgear. A remote VHF radio rocker switch has been included so that pilots can light up a single com to ask for start clearance and communicate with others without having to punch the master avionics switch. There's also a Flitecom digital recorder to 'tape' the last 30 seconds of a radio transmission, this prevents asking ATC to repeat their instruction if part of a clearance has been missed.

Continental IO-360 engines are usually easy to start and the Seneca V's Turbocharged RB versions are no exception. Reaching up, pumping some fuel into the manifold, then leaving the pumps in the 'low boost' position and thumbing the starter has the engines rumbling into life in no time. Punching the electronic monitoring system's self test button allows it to run through most of the electronic circuits and flash an annunciator warning if anything hasn't come on line.

The throttle levers are stiff and so is the nosewheel steering - a legacy of past Seneca models. The run-up is done at a high 2,300 rpm so the propellors cycle very quickly and snarl down to 1500rpm to check the feathering function. We line up. Seneca pilots are familiar with carefully monitoring manifold pressure on takeoff. Earlier turbo Seneca's used a simple bypass valve and an overboost relief valve, eliminating the need for a complicated automatic wastegate. This demanded more attention from pilots on takeoff in order to avoid an overboost. There's no such tiresome chores on the Seneca V. Now fitted with an auto wastegate, the throttles can be firewalled without risk of blowing the turbos, removing a major distraction from the takeoff phase. Piper has also included intercoolers and at long last pressurised magnetos.

There's no requirement for flap on takeoff and as on the earlier IV, the V continues with the electronic flap actuators. The Seneca needs positive back pressure to unstick and at 65 knots, the nose comes up smartly in reponse to firm control input. Aiming for an initial 88 knots blue line speed, we put the gear away and accelerate towards a best cruise climb combination of 110.

Seneca's have always required considerable trim input when altering speed or changing the airframe configuration and the V is no exception. Pilots won't be stepping out of their Seneca V's flush with a feeling of returning from a fighter interception sortie. the controls are firm, both in pitch and roll, encouraging as quick a transition to cruise levels as possible and then flicking on the KFC 150 autopilot. The Seneca is an A to B aeroplane and this it does very nicely. Piper are aware of the aeroplane's popularity amongst charter operators and know that many customers will use their aircraft in an IFR environment. Consequently Seneca's arrive fat with a useful Bendix/King package including dual Nav/comms with glideslopes and a KLN 90B GPS.

Whilst the Seneca doesn't exhibit fighter-like control response, its handling with an engine out is extremely friendly with a fairly light pedal force required to keep the ball in the middle and this can trimmed out very quickly. The extra 20hp per side has given the single-engine ceiling a boost from 13,800 feet to 16,500 feet. Whilst Piper has experimented with its taper wing, the company has elected to stay with the traditional thick-chord wing so beloved of early Cherokee's - this further gives the aircraft benign stalling characteristics. Any twin is likely to bite hard when entering VMCA - the speed at which directional control is lost on one engine. The Seneca is a great deal kinder in this condition than
a Baron or Cessna 310. Firstly, its counter-rotating propellors mean there is no critical engine and secondly its stall speed of 60 knots is close to its VMCA of 66 knots. However, few pilots will be exploring this regime outside of a training environment, but its good to know that the Seneca, in terms of light-twin single-engine surprises, needs to be 'in-extremis' before going feet-up after an engine failure. Blue line speed - best single engine climb speed - is 88 knots to which the aircraft accelerates quickly after lift off.

Piper's book figures for cruise speed are pretty accurate. The aircraft needs to fly at 18,500 feet to reach its maximum cruise of 190 knots. It's doubtful many operators will go this high however as its occupants will need oxygen - never a favourite for both pilots and passengers. Setting the manifold pressure to 30 inches and 2,400 rpm at 7,500 feet will produce a repectable 175 knots. With 122 gallons of useable fuel, the Seneca V will go Johannesburg-Cape Town with relative ease and arrive with a good 45-minute reserve. To do this will need some compromise between fuel and passengers. With maximum fuel there's 655 lbs available for occupants and baggage - that translates to three 170-pounders and overnight baggage. Filling the cabin reduces the fuel allowance to 50 gallons - enough for a tanks dry, 18 gallons per hour, long-range cruise endurance of two and three quarter hours - enough to do Durban from Johannesburg with an IFR reserve. It would be good to bear in mind that fuel flow changes considerably with power setting, so a high speed cruise of 180-plus knots will dramatically increase consumption from 18 gph to 28gph and in this case a passenger may have to be offloaded to stay within the weight and balance and fuel reserve requirements for this sector.

These figures are flexible enough for a private owner, but spring some limitations on charter operators in Africa. Typical charter flights for light twins often route across border to Victoria Falls, Harare and the Okovango delta - many flights departing with four or more passengers and luggage. If you see a Lanseria - Maun Seneca taxying out with six adult occupants, you'll know it's about 150 lbs overweight.

Seneca's need a little getting used to in the landing
configuration. Piper moved away from the low-tech but no-nonsense 'hand-brake' flap lever when they launched the IV, replacing it with a well-positioned electric system. Electric trim comes as standard and thumbing the switch on top of the control column easily compensates for approach trim changes. Those who know Seneca's will be familiar with the last rearwards and upwards travel of the column during the flare.

At the correct threshold speed this curious control input will tidily arrest the sink rate. Those unfamiliar with this minor quirk might be surprised as the aircraft settles down firmly onto the runway having seemingly run out of rearwards column movement. A good instructor and plenty of circuits will sort this out for new Seneca pilots, but it's not unfamiliar to see this type of aircraft sitting in the airframe repair shop having new gear mounting brackets fitted and in some cases spar-damage rectification. Nevertheless, turbocharged Seneca's have well earned reputations for getting into and out of very short strips and if this isn't enough, There's a Robertson STOL kit available.

From an early point in the aeroplane's career, Piper installed a club seating arrangement and the aircraft has always benefitted from a large rear passenger door. These features have made the aircraft especially popular. The interior of the V is a dramatic improvement over earlier models. Leather and soft fabrics have been used extensively in pushing the aeroplane's appeal upmarket. Concertina window blinds have been crafted to slide up and down within their own moulded fittings and Piper has even offered the choice of removing one of the central row seats and replacing it with a wood-finish console and pull-out table. Indeed, knowing that many Seneca customers are private buyers, the option list for the rear even includes a sound system and video installation. A 45,000 BTU combustion heater can be controlled from a panel in the passenger cabin to throw heat out of six floor-mounted vents.

The Seneca design has played a key role in Piper's continued if sometimes precarious struggle to survive. Whilst basic handling has remained pretty much unchanged, performance has steadily improved in response to customer design. The latest Seneca V is above all an indication that the company's marketing thrust has moved smoothly from charter operator to personal owner and it's, here the aircraft has demonstrated its greatest improvements - cabin and cockpit environment. Whilst the numbers are down from the heady seventies, the aircraft is bound to remain the world's best selling light twin.


Note: PlaneCheck often has some nice Piper Senecas for sale