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Aviation History
1958
1958 - 0693.PDF
ITALIAN EXECUTIVE The Piaggio P.166 By JAMES HAY STEVENS, A,F.R.Ae.S. A DIRECT adaptation of the well-tried P.136 amphibian,the Piaggio P.166 is aimed directly at the executive market,the structural weight saved by deletion of the planing bottom and wing-tip floats having been applied as much to improving range as to increasing payload. Considerable effort has also been devoted to interchangeability between the P.136 and the P.166, so that wings, engines and main undercarriage are identical. Control runs and systems, for the most part, have common components although, with the redistribution of side areas, an entirely new tail unit had to be designed. However, any user of the P.136 requiring a landplane of greater capacity, range and speed would still have the advantage of a considerable number of common spares. Use of a shoulder wing brings the e.g. low, so that the fuselage- mounted undercarriage is sufficiently stable, while the cabin floor sits comfortably close to the ground for entry without steps. Advantage has been taken of the aerodynamic requirements inherited from the amphibian to make a deep cabin with ample headroom—no less than 69in on the centreline. A fully adapt- able cabin of approximately 300 cu ft volume allows several alternative layouts, but the basic scheme is for two pilots, six/eight passengers, toilet and galley. Pilots sit side by side, with full dual flying controls and with engine /hydraulic console between, on a slightly raised flight deck. Behind are the four main passenger seats in two rows, either facing one another or all facing forward. The inboard arms of the seats have quick releases which allow them to be folded down and a central squab and back unit to be clipped in. The backs of the central seats are hinged to allow passage through the cabin. The spar bulkhead has a central opening, 59in high and 19.5in wide, giving access to a small bay just ahead of the undercarriage bay. On the starboard side is a full toilet, with a door, and to port there is provision for a galley. The large windscreen and raised seats give the pilots a good view, while the passenger's windows are of ample size. The pas- senger door on the port side allows ineress by most people without stooping—it is 54in high by 26in wide. There is a separate pilot's door (43in by 27in), with a rather high step, to starboard, for the cabin can be separated from the cockpit by a plastic "bulkhead." As in the P.136, there is a freight floor aft of the wing with a hatch (35.5in wide by 21in high) in the port side, while there is a large baggage volume available on top of the undercarriage bay —all being accessible from the cabin. Fuselage lines are deceptively reminiscent of those of the P.136 hull; in fact the fuselage is deeper and the roof rises above the juncture of the gull wings, which have in consequence been separated farther to increase the span slightly. The tailplane is now set slightly above, instead of below, the thrust line and is bolted to two frames which extend above the top line of the fuselage, which is actually level, although the large dorsal fin tends to give it the appearance of being swept up. Tailplane and elevators are of larger area than the P.136, as also are the fin and rudder. The reason for the backward rake on the latter is partly to increase the rudder moment arm without extending the fuselage, and partly aesthetic, in that it brings the outline in sympathy with the new P. 155 flying-boat being built for the Aeronautica MUitare. The landing gear is now a tricycle, although it may be recalled that the tailwheel undercarriage of the P.136 produces an almost level ground attitude. The new nose wheel retracts backward into a recess under the flight deck. Another important modification is that the fuel tanks are now entirely in the wing: a 47 Imp. gal bag tank outboard of each nacelle and a similar bag, of 49.5 Imp. gal capacity, in each wing- tip pod-fairing. The latter are of clean aerodynamic form and have been made deep and narrow, so as to obtain maximum end-plate effect. Transferring the fuel weight to four separate locations has relieved bending stresses in the wing and has enabled the same structure to carry a higher gross weight. The wing is, of course, unusually robust because it was designed to absorb considerable shock loads from the floats. The wing fuel cells will in future be offered as an optional alternative to the fuselage tanks on the P.136. •• [Continued overleaf MANUFACTURER'S DATA Dimantionl: Span 46Jt9.4in Length 38ft 7.1 in Height 16ft 4.8in Mean aerodynamic chord 6ft 5.1 in Wing area, gross ... ... ... ... ... ••• ... 285.89 sq ft Aspect ratio 7.28 Aerofoil NACA 230 root NACA 4412 tip Fuel capacity: Wing 47 Imp.galeach Tips ... ... ... ... ... ... ... ••• ..- 49.5 Imp. gat each Total 193 Imp. gal Weight and Loading*: Empty 5,0201b Disposable load 2.5801b Gross 7,6001b Wing loading 26.6 Ib/sq ft Power loading 11.2 lb/h.p. Performance: * " Max. speed, sea level 202 m.p.h. 10000ft ... 225 m.p.h Cruise, 70 per cent METO, 11,000ft 205 m.p.h. 65 per cent METO, 11.000ft 197 m.p.h. 55 per cent METO. 14,500ft ... 191 m.p.h. Rate of climb, s.l., two engines 1,410ft/min one engine feathered ... ... ... ... ... ... 235ft'min Service ceiling (100ft/min) 25,600ft single engine (50ftimin) 11,500ft Range, 65 per cent METO. 11.000ft 1,300 miles 55 per cent METO, 14,500ft 1.450 miles Take-off to 50ft 1,550ft Landing from 50ft 1.250ft Stalling speed, s.l. flaps 45 deg, gear down, power off 69 m.p.h. flaps and gear retracted ... . . ... ... ... 76 m.p.h.
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