Tupolev Tu-154 - Design

Design

The Tu-154 is powered by three rear-mounted low-bypass turbofan engines arranged similarly to those of the Boeing 727, but it is slightly larger than its American counterpart. Both the 727 and the Tu-154 use an S-duct for the middle (number 2) engine. The original model was equipped with Kuznetsov NK-8-2 engines, which were replaced with Soloviev D-30KU-154 in the Tu-154M. All Tu-154 aircraft models have a relatively high thrust-to-weight-ratio which gave excellent performance, although at the expense of poorer fuel efficiency, which became an important factor in later decades as fuel costs grew.

The flight deck is fitted with conventional dual yoke control columns.

The cabin of the Tu-154, although of the same six-abreast seating layout, gives the impression of an oval interior, with a lower ceiling than is common on Boeing and Airbus airliners. The passenger cabin accommodates 128 passengers in a two-class layout and 164 passengers in single-class layout, and up to 180 passengers in high-density layout. The layout can be modified to what is called a winter version where some seats are taken out and a wardrobe is installed for passenger coats. The passenger doors are also smaller than on its Boeing and Airbus counterparts. Furthermore, luggage space in the overhead compartments is very limited.

Like the Tupolev Tu-134, the Tu-154 has a wing swept back at 35° at the quarter-chord line. The British Hawker Siddeley Trident has the same sweepback angle, while the Boeing 727 has a slightly smaller sweepback angle of 32°. The wing also has anhedral (downward sweep) which is a distinguishing feature of Russian low-wing airliners designed during this era. Most Western low-wing airliners such as the contemporary Boeing 727 have Dihedral (upward sweep). The anhedral means that Russian airliners have poor lateral stability compared to their Western counterparts, but also have weaker dutch roll tendencies, eliminating the need for a yaw damper.

Like many other Soviet-built airliners, the Tu-154 has an oversized landing gear enabling it to land on unpaved runways, once common in rural areas of the Soviet Union. The aircraft has two six-wheel main bogies fitted with large low-pressure tires that retract into pods extending from the trailing edges of the wings (a common Tupolev feature), plus a two-wheel nose gear unit. Soft oleo struts (shock absorbers) provide a much smoother ride on bumpy airfields than most airliners, which only very rarely operate on such poor surfaces.

The original requirement was to have a three-person flight crew – captain, first officer and flight engineer – as opposed to 4/5-person crew on other Soviet airliners. A fourth crew member, a navigator, is usually also present in the former Soviet Union, due to union rules. Navigators are no longer trained and this profession will become obsolete with the retirement of older Soviet-era planes.

The plane's avionics suite, for the first time in the Soviet Union, is built to American airworthiness standards. The latest variant (Tu-154M-100, introduced 1998) includes an NVU-B3 Doppler navigation system, a triple autopilot, which provides an automatic ILS approach according to ICAO category II weather minima, an autothrottle, a Doppler drift and speed measure system (DISS), "Kurs-MP" radio navigation suite and others. Modern upgrades normally include a TCAS, GPS and other modern systems, mostly American or EU-made.

Early versions of the Tu-154 cannot be modified to meet the current Stage III noise regulations and are banned from flying where those regulations are in force, such as Europe. The Tu-154M may use hush kits to meet Stage III and theoretically Stage IV. However, current European Union regulations forbid the use of hush kits to meet Stage IV. The Tu-154M would need to be re-engined to meet Stage IV within the EU, an extensive and potentially expensive upgrade.