From The Cockpit – Piper Twin Comanche

For many owner-pilots, engine redundancy is a necessary requirement for any aircraft that they may operate for business or pleasure. Near the bottom end in size of the GA multi-engined market is Piper’s PA30/39 Twin Comanche, a versatile and efficient aircraft.

The PA30 evolved from the single-engined Comanche, a classic aeroplane in its own right as a high performance retractable LG competitor to Beechcraft’s Bonanza, with lines similar to those on the Cherokee and a subtle sleekness about its fuselage and tapered wing. The first Comanche flew in May 1956; production aircraft commenced coming off the tM line in October 1957 and sold well, becoming a popular touring aircraft. At the time the Comanche was in production, twin-engined aircraft being produced at Piper included the Apache, nearing the end of its run. The decision to modify the Comanche to fly with two engines was taken to provide a replacement for the Apache H. Such a design path was also taken by Beechcraft with the Twin Bonanza, which did not take off in the marketplace, though may be seen again by Piper in the near future, should a development decision be taken on the two-engine Malibu programme.

The prototype Twin Comanche flew on 7th November 1962. FAA Type Approval was attained in February 1963 and the first production aircraft flew in May of that year. The PA30 was a vast modification of the Comanche. The engine was off the nose, the wing was strengthened and the 3-spar light alloy structure was fitted with nacelles and mounting frames for a pair of Lycoming fuel-injected 10-320-B engines, rated at 160hp at 2700rpm. The engines use the Bendix RSA-5 type fuel injection system – measuring airflow and metering fuel via a special servo valve. With all engine accessories, including air intake ducting and fuel injector pump mounted off the rear of the downdraught-cooled engines, nacelle depth was minimised to that sufficient to enclose the cylinder and crankcase depth. Consequently they are probably the sleekest engine nacelles on any light twin. The two Hartzell HC-E2UL-2 constant speed/fully feathering twobladed props use 300 psi oil pressure from the CSU booster pump in order to unfeather.

The Twin Comanche’s fuel system affords extra flexibility when it comes to operational planning. Fuel is normally carried in four leading edge bladder cells. The main cells each carry 114 litres of which 102 is usable; the aux cells of 57 litre capacity each (all usable) are located outboard of the MAIN cells. In addition wingtip tanks are installed; and have an all-usable capacity of 57 litres each. Tip tank selection is accomplished with the engine fuel selectors on aux and the tiptanks selected. In addition, for fuel balancing, the selectors can be operated in cross-feed.

Fully fuelled the PA30 carries 432 litres of usable fuel, providing at a consumption rate of 64 litres/hr (14 lmpGal/Hr) a no reserves endurance ·o{ 405 minutes. Over a 57 hour period commencing Christma1, Day 1964, Max Conrad set a Class Cle distance record of the day, flying over 12,600km from Cape Town to St Petersburg in Florida. To accomplish the feat Conrad took off with 2720 litres of AVGAS at a takeoff weight of 6,6141b. The 1,000th Twin Comanche was delivered in March 1966.

Meanwhile Piper superseded the first models by introducing the 4/6 seat Twin Comanche B. The PA30-B expanded the aircraft’s accommodation versatility by introducing fifth and sixth family seats at the rear of the baggage compartment. The electrical system was expanded to two 50A generators and the vacuum system to dual (dry type) vacuum pumps. The PA30-B was offered in four versions, differing in equipment fit: Standard, Custom, Sportsman and Turbo (for which Rajay turbochargers were fitted to the engines).

The MTOW of the PA30-B is 1,689kg, reducing to 1,615kg for IFR operations under the Australian ANOs. There is a weight proviso that any in excess of 1,633kg must consist of symmetrically loaded fuel in the wingtip tanks. The aircraft basic weight for an’IFR-equipped PA30 with 6 seats installed is typically about 1,163kg, providing a maximum useful load of 526kg, or 216kg payload (enough for a young family of four) with full fuel.

With further equipment changes the Twin Comanche C was introduced in August 1968; it had a new instrument panel, together with new interior trim and exterior paintwork and improvements in heating and ventilation.

In February 1970 Piper marketed new versions of the Twin Comanche, with the new Type designation PA39. They superseded the PA30 – although basically the same aircraft, but having as the principal difference a pair of contra-rotating (CR) propellers. The description of handling quality changes for the aircraft is indicative of an attempt by Piper at market rejuvenation – but the drop in Vmca from 80 to 68kts would probably be enough of a benefit in itself. CR action was obtained through the efforts of Lycoming engineers by reversing the rotation direction of the starboard engine by changing the cylinder firing order and reversing some engine components.

However the market for the class was on the wane by this time.

The PA30 was taken out of production in 1970 after a run of 1998 aircraft; shortly thereafter PA39 production ended (in 1972) after 144 of the Type had been delivered.

In Flight

Entry to the Twin Comanche is via the single overwing door on the right. The interior is a four-adult-seat cabin, but a comfortable one at that. The inclusion of the fifth and sixth seats against the cabin rear bulkhead unquestionably makes the most use of cabin length available. Seated, one becomes aware of the nose-up stance of the plane on the ground. As a result of the short main gear length. The landing gear is electrically retracted/ extended and uses oleo-pneumatic cylinders for shock absorption. Taxiing is straightforward. Nosewheel steering through an arc of 40 degrees is actuated by use of the rudder pedals, while the mechanism is disconnected automatically upon gear retraction in order to reduce rudder loads in-flight.

Flight controls are conventional. For pitch control and stability an all-moving horizontal stabilizer is employed, with a combined trim and anti-servo tab – standard Piper at the time. Trims are two-axis, there being no adjustable tabs on the ailerons:

The PA30/39 is an efficient twin. The cleanliness of the nacelles is a reflection of the aerodynamic lines of the aircraft overall. For the private/business pilot whose cabin size require ments are met by the PA30, the aircraft provides engine redundancy at a fuel consumption not much more than a high performance single having the same cruise speed – 64 litres/hr for a TAS rounded of 150kts. The cleanness of the aircraft is evidenced upon speeding up from the holding configuration, approximately 15in MAP for an airspeed of 95kts; opening the throttles to cruise power results in a surge of acceleration towards 150kts.

The PA30’s handling qualities suffer to some extent from a relatively high Vmca of 80kts. Also, at minimum control speed the aircraft can depart with a brisk roll acceleration. (Tested at altitude the Vmca shows itself to be substantially lower, nearing 70kts. ) The PA30 could have well benefitted from an enlarging of the fin, or the addition of a dorsal as part of the original changeover. On takeoff, because of its relatively low wing loading (stall speed 60kts in the takeoff configuration) the airplane becomes skittish on the ground at much above 65kts. Acceleration is brisk but there is the short interval from liftoff until 80kts where in the event of engine failure throttles must by closed and the airplane landed ahead. Blueline speed at 91 provides a relatively small margin over the minimum control speed. With the gear coming up the flap must then be retracted promptly before its extension limit speed of 107kts is reached. The single flaps are electronically operated.

Fuel should be drawn from the aux and wingtip tanks only in the cruise (level flight). Fuel feed from the wingtip tanks is quite sensitive to interruption through sloshing when rolling the aircraft, as I found when executing shallow (12 to 15 degrees of bank) en route turns with the tiptanks about half-full.

Stalling qualities are straightforward: there are two separation assisting breaker strips on each wing leading edge, and which are built into the leading edge rubber boots for the icing-equipped aircraft. Stall speeds at 1,689kg range from 63kts flap-up to 59kts in the landing configuration – a moderate 27 degrees.

Normal en route descents are accomplished at an indicated airspeed of 140kts using 15in MAP and 2,300rpm for a rate of descent of 500ft/min; this speed is also the recommended turbulence penetration speed. Arrival procedures call for a downwind power setting of 18in/2,300rpm to keep the speed below 120, then reducing to 15in turning base in order to decelerate to 1OOkts before taking flap and descending. On final, a bluelines speed 91 as a standard procedure should be maintained until decision height and full flap then taken. Due to the low ground clearance, following the flare a tendency to float must be controlled to the subsequent touchdown.

As with most light twins, asymmetric work, including final approach overshoots above a decision height of 400ft AGL is straightforward if the speed is kept up at blueline until below landing DH. Single engine landings are accomplished from an initial approach speed of 95, reducing to a threshold speed of 85kts.

A limited number of Twin Comanches are on the Australian register – a total slightly less than fifty. Market prices on used aircraft reflect the type’s vintage and also assure that a PA30 purchased will maintain its value. List prices typically cover the range mid $40,000s to mid $50,000s.