Technical

Fuselage

The fuselage is circular in section with a diameter across the parallel-sided section of 11ft 8in, which is wide for an aircraft of this type, allowing for very comfortable 5 abreast seating.  The original mock-up was actually displayed in this configuration with standard Boeing 747 seats.  With narrower seats, 6 abreast is easily achievable and this is a common layout for UK and European operators.  Construction of the 146 is fairly conventional, being a semi-monocoque design in aluminium-copper alloy, with redux bonded stringers and dual-ring frames.  Great simplicity and a corresponding reduction in the number of fasteners has been achieved by using redux bonding and integrally machined parts.  The nose and tail sections lack stringers

Wings & control surfaces

Originally manufactured by Textron Aerostructures, the wings are constructed from integrally-machined components in aluminium-copper and aluminium-zinc alloys.  The aerofoil was designed by Hawker Siddeley, using knowledge gained from previous wings  designed at Hatfield, including the Trident and the Airbus A300.  T/C ratio at the root is 15.3%, reducing to 12.2% at the tip.  Sweep at the quarter-chord is 15 backwards and anhedral at the trailing edge is 3.

High lift devices are comprised of single section, tabbed Fowler flaps, spanning 78% of each trailing edge, there being no leading edge flaps or slats.    The flap actuators are located in three rails under each wing.  The two most inboard rails are integrated into the engine pylons, making an additional drag saving.  There are six lift dumpers, which are all identical and therefore inter-changeable and a pair of roll-spoilers, also interchangeable, which are hydraulically operated and assist the ailerons in providing roll control.  The tailcone also opens providing additional drag for deceleration.  This has allowed both the omission of reverse thrust on the engines for deceleration and the ability to make the steep approach into difficult airports such as London City.  The tailcone brakes can be used in flight and permit a decent rate of upto 7,000fpm without altering the pitch-incidence and lift producing characteristics of the wing in the way that wing-mounted airbrakes do.

Tailplane

The aircraft has a high mounted tail on a moderately swept fin of large area.  The high mounting position provides both the best moment arm (and thus reduces the necessary tailplane area) and keeps it clear of the engine efflux.  As there are no leading edge high lift devices and the range of pitch angles to be balanced is small, the tailplane is fixed-incidence, further reducing complexity.  The tailplane uses a standard NACA aerofoil profile inverted.

Engines

Avco Lycoming ALF 502R

The original BAe146 series was powered by the Avco Lycoming ALF 502 series engine, a twin spool high bypass ratio turbofan of modular construction.  Based around the core T55 turboshaft engine, the ALF 502 is composed of a fan and two axial flow low pressure compressor stages, driven by a 2 stage axial uncooled turbine and an inner high pressure compressor of 7 axial stages and one centrifugal stage driven by a 2 stage air cooled axial flow turbine.  The combustion chamber is of annular, reverse-flow type. Avco Lycoming was later acquired by Textron Lycoming and the FADEC (Full Authority Digital Engine Control) equipped LF507 development was used on the Avro RJ series aircraft.  The Avro RJX was to have used the new Honeywell (Honeywell acquired Allied Signal who themselves had bought the Lycoming gas turbine division from Textron in 1995) AS977 engine.

ALF 502 engine:

Length 1.06m
Diameter

1.49m

Weight 595kg
Thrust 33.36kN
TSFC 12.1mg/Ns
Bypass ratio 5.0
Compressor pressure ratio 13.8

Undercarriage

The hydraulically-retractable undercarriage was designed by Dowty-Rotol.  It is a particularly robust design, for operation on low grade airfield surfaces including gravel.  The nosewheel is steerable, retracting forwards, whilst the main gear retracts inward.  The brakes are hydraulically operated carbon-discs.  The wheels are supplied by Dunlop.

Systems

The aircraft has two 3000psi hydraulic systems for flaps, air brakes and undercarriage.  Two AC generators located on the outer engines supply the 28V DC electrical system or alternately, this can be supplied by the APU located at the rear of the fuselage, which is either a Garrett AiResearch model on early 146s or a Hamilton Sunstrand model on Avro RJs.

Avionics

The original BAe 146 had a conventional analogue flightdeck for operation by two pilots with a Smiths SEP 10 autopilot.  During the late 1980s, an EFIS (glass cockpit) version was developed.  The idea was to introduce it on the -300 series but to avoid problems with pilots being certified for only one type of 146, full standard introduction of this layout was not introduced until the Avro RJ series.