Yakovlev Yak-40 - Design

Design

The Yak-40 is a low-winged cantilever monoplane with unswept wings, a large T-tail and a retractable tricycle landing gear. The passenger cabin is ahead of the wing, with the short rear fuselage carrying the three turbofan engines, with two engines mounted on short pylons on the side of the fuselage and a third engine buried in the rear fuselage, with air fed from a dorsal air-intake ahead of the fin by a "S-duct", as was an auxiliary power unit which was fitted to allow engine start-up without ground support on primitive airfields. The three AI-25 engines were two-shaft engines rated at 14.7 kN (3,300 lbf). The engines had no jetpipes, and initially no thrust reversers.

The pressurized fuselage has a diameter of 2.4 metres (94 in). Pilot and co-pilot sit side-by-side in the aircraft's flight deck, while the passenger cabin has a standard layout seating 24-27 passengers three-abreast, although 32 passengers can be carried by switching to four-abreast seating. Passengers entered and left the aircraft via a set of ventral airstairs in the rear fuselage.

The wing is fitted with large trailing-edge slotted flaps, but had no other high-lift devices, relying on the aircraft's low wing loading to give the required short-field take-off and landing performance. The port and starbord wings join at the aircraft centreline, with the main spar running from wingtip to wingtip, with the wings housing integral fuel tanks with a capacity of 3,800 litres (1,000 US gal; 840 imp gal). The aircraft has a large fin, which is swept back at an angle of 50 degrees to move the tailplane rearwards to compensate for the short rear fuselage. The horizontal tailplane itself is unswept.