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 lateral misalignment (refer to A Study of Structural Failures in the
Hush-Houses at NAS Miramar, J.L. Grunnet and G. Getter [6]). The maximum
augmenter wall temperatures were indeed sensitive to misalignment. Suggested
ways of reducing the structural damage included:
a)
better F-14A alignment
b)
fiberglass pillows more tightly packed
c)
better placement of the unperforated Inconel augmenter face
sheets
d)
application of stress relief slots in certain augmenter section
aft bulkheads.
Methods of reducing the maximum augmenter wall temperature through
application of an augmenter inlet forcing cone or flare were checked at
model-scale during 1983 (refer to 1/15 Scale Model Tests of a Forcing Cone
Augmenter Pickup for Hush-Houses and Test Cells and Holt Flow Model Tests of a
1/15 Scale Hush-House with Augmenter Flare and Forcing Cone Flow Pickups, both
by T.F. Buckley and T.J. McDonald [14, 15]). An augmenter flare, such as
incorporated in the Patuxent River augmenter, resulted in significantly lower
wall temperatures. During the Patuxent River hush-house checkout, both
engines of the F-14 were run up to maximum afterburning thrust without damage
to the exhaust system.
2.7
MCAS Cherry Point Pegasus Demountable Cell Tests. In 1982,
diagnostic tests of the F402 Pegasus engine in the A/E 32T-15 engine test
enclosure (demountable test cell) were performed at MCAS Cherry Point, North
Carolina (refer to Aerodynamic Measurements Mode in the Marine A/E 32T-15
Engine Test Enclosure at Cherry Point (F-402-2), Relative to Pegasus
Acceleration Lay and Subsequent Conclusions and Recommendations, J.L. Grunnet
[7]). An apparent engine acceleration lag was being encountered such that
acceleration time specs could not always be met. Checks were made of the fuel
system, cell enclosure flow field etc, and it was concluded that the fan inlet
distortion was larger than desirable. It was finally discovered that a
tachometer circuitry problem was responsible for the indicated lag, but
changes to improve the cell flow were recommended anyway.
2.8
AV-8 Harrier Hush-House Model Tests. In 1982, a 1/15 scale model of
a Harrier hush-house was tested to verify adequate flow pickup and to
determine augmenter pumping (refer to 1/15-Scale Cold-Flow Model Tests of a
Hush-House with Simulated AV-8 Aircraft Exhaust, J.H. Berger and J.L. Leuck
[13]). Reasonably good flow pickup was demonstrated over the whole range of
nozzle vector angles from 0deg. F to 98 deg. F (-18 deg. C to 37 deg. C).
Augmentation ratio remained relatively constant at 3.5 over the entire range
of nozzle vector angles. Since the date of the model tests a full-scale
Harrier hush-house design has been completed.
2.9
NAS Dallas Test Cell. In 1979, a jet engine test cell was designed
for N.A.S. Dallas incorporating the dry-cooled sound absorptive augmenter
exhaust system concept. This was checked out in 1983 (refer to Aero-Thermo
Checkout of NAS Dallas Dry-Cooled Jet Engine Test Cell, J.L. Grunnet and N.C.
Helm [8]). External noise limits were exceeded and this has resulted in
consideration of alternative augmenter inlet designs which avoid noise
generation.
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