AEROSPACETESTINGINTERNATIONAL.COMAPRIL 2015 |^87
Harrier engine upgrade z
W
hen the US Marine Corps
asked Rolls-Royce to
improve the performance
of fan blades for its Pegasus engine
for the USMC Harrier (see figure above),
it set a test challenge that involved some
sophisticated vibration modeling and
trials, even including the reactivation of
a mothballed test facility.
The Rolls-Royce Pegasus engine
powers the Harrier aircraft operated
by the USMC as well as the Italian,
Indian and Spanish navies. In 2012,
the USMC awarded Rolls-Royce a
contract under the Component
Improvement Program (CIP) to develop
a modified fan blade to improve the
robustness of the engine.
PROBLEM CONTROL
Rolls-Royce created a number of finite
element (FE) stress models to
understand the dynamic behavior of
the blade and establish the root cause
of some of the problems that had been
experienced in initial operations. The
fan blade, as shown in the figure on the
right, is manufactured from titanium
alloy and rotates at in excess of
8,000rpm. It is retained within the
engine by a feature commonly referred
to as a dovetail.
The blade features a ‘snubber’ at
around two-thirds height, which is
intended to control the flap and
torsional response of the blade. After
the analysis was completed, it was
established that issues could be caused
by high stresses within the blade,
Supporting the development of a new Pegasus LPC1 fan blade for the US
Marine Corps Harrier upgrade led to the revival of a mothballed testbed
BY TIM WILLIAMS
LEFT: The Pegasus
engineLEFT: Pegasus
LPC1 fan blade