S
sensor that interfaces with
the anti-skid brake system.
The dark circles of the tires
are clearly visible when a
737 takes off, or is at low
altitude.
737s are not equipped with fuel dump
systems. The original aircraft were too small
to require them, and adding a fuel dump
system to the later, larger variants would
have incurred a large weight penalty.
Boeing instead demonstrated an
"equivalent level of safety".
737-800 engine with non-circular "hamster pouch" inlet
Depending upon the nature of the emergency, 737s either circle to burn off fuel or land
overweight. If the latter is the case, the aircraft is inspected by maintenance personnel
for damage and then returned to service if none is found.
Engines
Engines on the 737 Classic series (300, 400, 500) and Next-Generation series (600, 700,
800, 900) do not have circular inlets like most aircraft. The 737 Classic series featured
CFM56 turbofan engines, which yielded significant gains in fuel economy and a
reduction in noise over the JT8D engines used on the -100 and -200, but also posed an
engineering challenge given the low ground clearance of the 737. Boeing and engine
supplier CFMI solved the problem by placing the engine ahead of (rather than below)
the wing, and by moving engine accessories to the sides (rather than the bottom) of the
engine pod, giving the 737 a distinctive non-circular air intake.
The wing also incorporated changes for improved aerodynamics. The engines'
accessory gearbox was moved from the 6 o'clock position under the engine to the 4
o'clock position (from a front/forward looking aft perspective). This side-mounted
gearbox gives the engine a somewhat triangular rounded shape. Because the engine is
close to the ground, 737-300s and later models are more prone to engine foreign
object damage (FOD). The improved CFM56-7 turbofan engine on the 737 Next
Generation is 7% more fuel-efficient than the previous CFM56-3 in the 737 classics
Boeing B737
June 2017
www.alliance-airways.net
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