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Aviation History
1958
1958-1- - 0071.PDF
FLIGHT, 18 July 1958 73 Fully Aerobatic Four-seater THE PIAGGIO P.149-D IN FLIGHT By JAMES HAY STEVENS THE Piaggio P.149-D is a dream aeroplane—cruising at agenuine economical 145 m.p.h. with four passengers andbaggage, or even five passengers, and as lively in every aero- batic as the most exacting virtuoso could desire. Add to this,delightful controls plus a need for co-ordination but a forgiving- ness which preserves the undeserving pilot from the consequencesof error, and one has an ideal combination trainer and tourer. The P. 149 was originally adapted about three years ago fromthe tailwheel P. 148 primary trainer—itself an aeroplane with exquisite handling qualities—as a four-seater tricycle tourer.Then it was re-engined with the 260 h.p. GO-480 in place of the 180 h.p. O-435 and offered to the Aeronautica Militare andthe Luftwaffe as a communications aircraft—only to be accepted as a basic trainer by the Germans. Structure. Structurally it is a simple aeroplane of classic sheet-metal design, manifestly from the same stable as the P. 136 and P.166. In the Piaggio tradition the wing has two spars, the frontone taking bending loads and the rear forming the fourth wall of a torsion-box with the skin, as well as carrying the aileron andflap hinge brackets. The ribs are flanged pressed blanks. Welded- steel brackets are used for the control and undercarriage hinges,and the spar-root fittings are machined steel forgings. The metal flaps and ailerons have minimum internal structure, the skin beingstiffened by impressed chordwise beads. Fuselage construction employs channel-section ring frames,notched for the stringers. There are no longerons, but the U-sec- tion frames at the large cockpit opening are joined by sturdy"longitudinal members. There are bulkheads at the front and rear of the cockpit and two at the tail, as well as substantial under-floorcross-beams for fittings to which the wing spars are bolted. Tail-unit fixed surfaces are miniature replicas of the wing,while the control surfaces are similar in construction to the ailerons, with bead-stiffened skin. The undercarriage has three piston-type compression legs withwelded-steel fabricated half-forks and scissor torque links. The main legs are fully cantilever, but the nosewheel has a crossheadwith side-load bracing tubes. Retraction is by a centrally placed electric motor which, via push-pull tubes connected to levers atthe legs, retracts the main wheels outboard and the nosewheel aft. Emergency lowering is by a hand crank between the pilot's seats. The flat-six Piaggio-built Lycoming GO-480-B1A6 is installedon a steel-tube engine mounting in a characteristic cowling with exhaust-induced cooling airflow. The Piaggio P.1033/G4/D/Ametal-bladed hydraulically operated constant-speed airscrew has a diameter of 7.21ft and a pitch range of 10 deg to 30 deg.The cockpit is spacious, the bench-type rear seat comfortably accommodating two plump people or three less well-fed ones.There is a fine all-round view from each seat, and the pilots' forward view is perfect at all angles. Controls are well positioned:pull-up flap lever between the seats; pitch, throttle, fuel cut-off, undercarriage and trim centrally (pitch and throttle duplicated onthe port side); flying panel in front of the port seat, engine instru- ments centrally; starting controls at the port edge of the dash;electrical and radio switches overhead on the windscreen frame. Canopy latch and jettison lever are in the roof. The noise levelis fairly high in the military aircraft, but speech, as opposed to yelling, is practical without headsets. Flying. My personal introduction to the P.149-D was atrip along the coast from Nice to Villanova d'Albenga with Commandante Aldo Gasperi, Piaggio's chief test pilot, an ex-fighter pilot who has ensured the refined control characteristics of all the post-war types. This 25-minute flight, with a wonderful145 m.p.h. unfolding Cinerama of the Riviera's toy-like coastline, emphasized what an attractive tourer the P.149-D would make. Our next meeting was during a partial lifting of the all-pervading low cloud, for an hour's circuits and bumps sandwiched between 600ft hills (see photograph) and a 900ft cloud-base.Starting is by direct-cranking electric starter (tank booster pump ON) after haying primed by hand—the fuel cut-off is usedto "catch" the engine if it is reluctant. Starting is on No. 1 mag only. Direct mechanical connection of the rudder pedals to thenosewheel gives precision steering at all speeds without recourse to the toe-pedal hydraulic brakes—a safety feature which, I feel,should be on all light aeroplanes. The forward taxying view is better than the road view on most cars. For take-off one sets elevator trim neutral, fuel booster pumpON (mixture is automatic), max. r.p.m., flaps two notches (18 deg). Acceleration on opening the throttle (30in Hg, 3,400 r.p.m.) is a genuine kick in the pants, and some right rudder is required asthe torque and slipstream take effect. There is a rudder trim, but it is only necessary for precision trimming to cruise handsand feet off; the full-throttle rudder bias is jar less tiring than that on, say, a Tiger Moth. The P.149-D can be lifted off at 45 ktI.A.S. and accelerated safely—with full lateral control—in an amazingly taildown attitude, which can be an advantage on roughgrass, since it eases nosewheel loading. The runway technique is to ease the stick back to lift the nosewheel (so that it slows downbefore retraction), then at 60 kt I.A.S. to fly off. Then: brakes to stop the wheels; u/c UP (three-position toggleswitch); reduce to 25in Hg manifold pressure; 3,000 r.p.m.; booster pump OFF; raise flaps gently. Climb seemed to be ratherbetter than l,500ft/rnin at 100 kt s.l. I.A.S. Reduce to 2,800 r.p.m. and 23in Hg for cruising—rather less to keep circuit speed down.The controls are light and sensitive; and, although well har- monized, the elevator is noticeably the least light—a gearing modi-fication introduced in the military trainer to inhibit overloading. The rudder is practically unnecessary, save at take-off, in verysteep turns, and for aerobatics. On a later occasion, the only morning in a whole week whenthe sky cleared, we climbed to 10,000ft for aerobatics—and still obtained 750ft/min at 80 kt I.A.S. This time we were in aLuftwaffe aeroplane, where one was greeted, amid a sea of alien notices, by the familiar dials of a Smiths A.S.I, calibrated in knotsand a Kelvin Hughes altimeter marked in feet—albeit labelled HOHE—-and a manifold pressure in decimals of one Ata.Commandante Gasperi produced the whole gamut of aerobatics, including a full roll inserted on the top of a complete loop andhis own particularly smooth over-the-vertical Immelmann turn. The stall is very innocuous indeed. It requires a whiff of throttle(to keep the Lycoming from spitting) and plenty of backward stick to get the nose up and the speed down. At about 40 kt I.A.S.there is some buffeting, although lateral control remains effective. The stall occurs "off the clock," when the nose drops. If the stickis kept back, the aeroplane nods its way down and the slightest easing of the stick puts it into a glide. If a wing goes down, it canbe picked up at once with rudder. Spinning requires the P. 149 to be thrown in with full elevator,rudder and some aileron at 60 kt (its predecessor, the P.148, never would spin for me, although Gasperi could do it every time).The A.S.I, read 80 kt, but nevertheless it appeared to be a true spin and not a spiral. After a couple of turns rotation becomesvery fast, but recovery is normal after giving full rudder, then full elevator, control forces being quite light and the ensuing divebarely exceeding cruising speed and perhaps 2g. Five turns and the pull-out take about 2,000ft. The good stalling and spinning characteristics would appearto be due to the wing aerofoil washout from a bi-convex root to a cambered tip, to the long tail arm, and to careful blending ofthe fuselage lines. Returning to the circuit, the undercarriage is lowered at100-110 kt and speed is then reduced to 70 kt to make flap lower- ing easy. The pull-up lever is released by pressing a button inthe tip and easing in the opposite sense and only the last notch (43 deg) is a little awkward. The elevator becomes very heavywith flap and requires full trim for comfort and safety in the glide, although the stick force is always within one's physicalcapabilities. The best approach speed thereafter is 80 kt, reducing to 70 kt over the hedge on cutting the throttle.The rudder is unnecessary on the approach, all steering being done on the ailerons right to the touchdown—in fact, introduc-tion of yaw through the rudder tends to over-controlling. Rather deceptively, there is no fade-out in elevator feel as the stall isapproached and the P.149 is flared out to a tail-low touchdown on the main wheels alone. Once on the ground it runs true and,even without brakes, decelerates quickly. PIAGGIO P.149-D. (Piaggio-built Lycoming GO-480-B1A6, rated at 260 h.p. and driving a geared, variable-pitch propeller) Dimensions: span, 36ft 6in; length, 28ft 9J-in: height, 9ft 6in. Weights: equipped, 2,557 Ib; fuel and oil, 397 Ib.; pilot, 170 Ib: payload limit 580 Ib; gross, 3,704 Ib (aerobatic, 3,197 Ib). Performance (normal category): level speed at sea level, 189 m.p.h.; typical cruise, 160 m.p.h. at 7,000ft; take-off (18 deg flap), 835ft run, 1,330ft to 50ft; climb, 3 min 28 sec to 3,280ft and 13 min 49 sec to 9,840ft; practical ceiling 16,400ft; max. range at 10,800ft at 145 m.p.h. (146 h.p.), 675 miles; landing (43 deg flap), 670ft run, 950ft from 50ft; stall with full flap, 63 m.p.h. NOTE: VNE is 230 m.p.h. (252 in aerobatic category).
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