Aircraft Profile: Bombardier Learjet 31A

Singapore Airlines pilots will be familiar with this aircraft as it is used as the training aircraft for the company pilots. But in its traditional role it is still seen all over the world.

More than 250 of the type were delivered by Bombardier before production ended in 2003 to make way for the Learjet 40 series.

With full seating and maximum fuel capacity, the aircraft can take off from runways shorter than 1,067m (3,500ft) and can climb to its maximum operating altitude of 15,545m (51,000ftand with a crew of two and four passengers, the aircraft's maximum range is 2,680km or 1,447nm.

Now on the used aircraft market some models are receiving benefit from reengineering. Raisbeck Engineering has achieved a drag reduction of up to 12% with its ZR Lite performance enhancement programme for the Bombardier Learjet 31/31A/31ER series. The tests were run on a modified Learjet 31A-136 at cruise speeds up to Mach 0.81.

Key to reducing drag on the aircraft was minimising the transonic shock build-up between the engine nacelle, wing, pylon and fuselage, where local Mach numbers can reach M1.6 during normal cruise. Raisbeck addressed this by installing new trailing-edge flaps with span-wise twist that ranges from -6є at the root to +2є at the tip.

Heritage:

The Lear 31 is a final derivative of the Lear 23 first created in 1963. The first flight of the LearJet 31 took place on 11 May 1987. The Learjet 31A variant was introduced in October 1990. This version featured increased cruising speed, a digital avionics system with AlliedSignal (today Honeywell) EFIS and an instrument panel layout change. The first 31A serial number 31A-035 entered service 15 August 1991. The last 31A delivered, serial number 31A-242 was delivered 1st of October 2003. The Learjet 40XR is seen as the replacement for the 31A as the entry level jet for the Bombardier range.

Spotters' Guide:

The Lear 31A has a low straight "Longhorn" wing with a tapered leading edge and large blended winglets. It has two rear mounted engines and a swept T-tail and tailplane. Notable is the delta fin (offering increased stability) each side below the tail. There are five cabin windows on the left behind the large entry door and six windows on the right.