Piper Malibu/Mirage From The Cockpit

Unfortunately this research, after having been initiated at the height of the GA sales boom, bore fruit to be put into industry practice at a time when sales were sliding fast. At Kerrville, LoPresti of Mooney did indeed put it into practice with the configuration of the 301 by applying cruise-optimised wing sizing (ie making the wing as small as possible whilst maintaining stall speed no higher than 61 knots, in order to bring the design cruise speed as close as possible to the most aerodynamically efficient airspeed).

At Vero Beach, Jim Grimswold led the Malibu design team with a different approach. As recounted to me two years later by Trevor Linton-Smith, Piper’s chief aerodynamicist at the time, the more classical wing size of the Malibu provided internal volume for fuel tankage sufficient to give the aeroplane ·legs which matched its high flying capability; Piper determined to employ CADCAM as much as possible on the draughting and most significantly perhaps appointed a project weights engineer with the power of veto over the draughted details. The last point was crucial in keeping the basic weight of the aircraft down. I recall noting the brochure’s empty weight in 1983, 30kg less than that of the P210 – 1,032kg compared to 1,063kg – for an airframe lifting comparable maximum weights – 1,75411,820kg – with a hull of 20% more volume, greater aspect ratio wings, bigger cabin pressure differential – 5. 5psi compared to 3. 35psi – and wondering whether service would show up fatigue soft spots; not so generally, the fatigue characteristics so far have been good, one exception being the ailerons which have been cracking from torsion induced fatigue due to the actuating rods engaging at the inboard ends of a very long aileron span.

Details of the Malibu’s aerodynamic design are classical – wing section choice being the well established NACA23012, low aircraft drag through employment of a high aspect ratio for type (10. 6 compared to 7. 7 on the P210) rather than by reduction in wing area (as already discussed above). Consequently, the Malibu has a large wingspan at 43 feet but for Piper’s chief aerodynamicist, large aspect ratio was an integral element of success. “If Jim had given me 45 feet, I would have taken it”, is how Linton-Smith put it to me. The wing trailing edge sported a wide span single slot flap, initially hydraulically actuated. Flying controls are conventional, ailerons are cable operated.

Compared to that of the P210, the Malibu’s internal dimensions provide for true cabin class accommodation for up to five passengers (cabin width 49. 5 inches and height 47 inches); the squat double oval fuselage cross-sectional shape affectionately gave rise to the nickname of Fat Albert for the aircraft amongst Piper’s workforce.

Cabin (and cockpit) entry is via an airstair door on the left side near the rear of the cabin. The cabin itself, at 16 feet, is long and some care needs to be taken to ensure correct CG when loading. Up front pilot accommodation is spacious; panel size likewise is ample for whatever comprehensive avionics fitment the owner wishes to install.

The heart of the Malibu is cowled under elegant lines. Part of the NASA GA fuel efficiency research was of course concerning engine technology. To compete against the P210, with a bigger and more substantial aircraft, Piper nevertheless needed to impress upon the market a better specific air range fuel consumption than on the Centurion: the market of the day remained sensitive to the fuel prices which had spawned the aforementioned NASA funded research. Engine technology of the daycamein the form of the Teledyne Continental TSIO-510-BE, rated 310bhp at 2,600rpm and carrying dual turbochargers and intercoolers (which aid fuel efficiency by cooling the charge), and nevertheless being required to be operated 50°F lean of peak tor design point fuel consumption. The brochure fuel consumption was 60. 6 litres/hr at 75% power, an 8% reduction over that of the TSIO-520-AF on the P210. The Dash BE was an integral part of the Malibu design and yet represented a palatable enough choice; as a modified well developed engine, the Dash BE was a downrating of the 375-425bhp TSIO-520-K and M series.

The Dash BE and better aerodynamic efficiency gave the Malibu a clear competitive edge in specific air range over the P210, 3. 43 compared with 2. 9nm/litre at 75% power and maximum operating altitude.

Redundancy was a key element in the systems design of the Malibu, the engine driving dual alternators and vac pumps. However the primary systems – landing gear and flaps – were driven in a relatively complex manner by a combined hydraulic system, indigenous in design. The pressurisation system was standard type for light aircraft, with dump valve differential controlling. The maximum differential of 5. 5psi allowed cruise at FL250 (compared to the P21O’s 3. 35psi and maximum cruising altitude of FL230).

Thus did the Malibu enter service. Its 75% cruise speed of 208 knots prompted Cessna to react by re-engining the P210 with the TSIO-520-CE of 325bhp, upping the MTOW to 4,10Olb and increasing fuel tankage. However, at 190 knots in 65% cruise, the Centurion still could not catch the Malibu (200 knots), but Piper matched the MTOW in order to give the Malibu the same loading versatility as the Centurion.

In service, the hydraulic system showed itself to be the soft spot of the aircraft. Rigorously bench tested, the elements of the system when combined and exposed to the service environment in the aircraft showed flaws- primarily erratic flap control valve and system relief valve operation which resulted failure of the hydraulic pump to cut out and subsequent burning out of the motor. A number of interim fixes were mandated, in the form of annunciator lights, thermal overload protection and inclusion of a pressure accumulator. The breakthrough in dependability came however when the flap drive system was made electric, making the hydraulic system a one service type.

With the hydraulic problems licked, the Malibu’s engine suffered a spate of mechanical failures, attributable to problems associated with wrist pins and starter drive shaft torque. Repetitive inspections were not a sufficient enough palliative and the fleet was grounded until Teledyne instituted satisfactory improvements and changes in maintenance procedures. This was an expensive time for Piper; following the LSI takeover, Piper was put on the market to be bought for a reputed song by Californian businessman Stuart Millar. With an enthusiast’s love for aviation, Millar was determined to build and sell light aircraft. The Malibu grounding necessitated an enhancement of goodwill for the Piper name- the Company paid First Class airfares to Malibu owners for business trips for which they required their grounded Malibus.

With the fleet back in the air Piper embarked upon a reengining of the Malibu with the Lycoming TIO-540-AE2A of 350bhp, an engine based upon the TIO-540 that Piper had countless flying hours experience on the PA31 range. Piper’s rationale for the re-engining was a questionnaire to Malibu operators seeking improvements they saw as desirable- 1 0 knots additional cruise speed and 10otb additional payload was the answer. However Piper’s support for its existing customers in not blaming the Continental engine for the redesign effort must have undoubtedly hidden discontent at Vero Beachforthe Continental’s performance. Certificated in 1988, the PA-46-350P Malibu Mirage offered an enhanced cruise performance-recommended at 215 knots, and high speed at 225; MTOW to 4,3001b.

The Mirage incurs a significant reduction in specific air range, reflecting the stabilisation of fuel prices and attendant easing of market forces which in 1983 tended to make the customer to consider fuel efficiency of paramount importance. The engine was mated somewhat surprisingly to a two bladed prop; in spite of this, aircraft noise lev . els are moderate, the certificated overflying noise level being 74. 5dBA. Range suffered considerably- tanks full it went down from 1,600nm at 192 knots to 1,090nm at 207 knots.

If the Malibu, throughout its to date brief history, has been designed above all else for performance, handling has not suffered. In spite of the long wingspan the ailerons do the job adequately; pitch and yaw handling is also pleasant. You will not buy the Malibu for field performance however – a short range mission (say 200nm) with four passengers requires a field length of 3,000ft.

$US400,000 will get you a Malibu Mirage, but if happy with the service maturity of the 310P, head Stateside, where used models on the average list between $US335 and $345,000.