Combat aircraft

Larson. ‘The F/A-18 was used to create

these shockwaves by  ying at a speed of

Mach 1.38 at 32,000ft.’

On the ground the goal was to collect

sound signatures from the sonic booms

created by the F/A-18 after they had gone

through the atmospheric turbulence

layer before reaching the ground. For

this, three microphone arrays were

strategically positioned on the ground at

Edwards. In the air, a TG-14A motorized

glider collected sound signatures of the

shockwaves. For this the TG-14A was

 tted with a specially con gured audio

instrumentation package and a wing-

mounted microphone boom. At the

test point it would shut down its engine

to eliminate unnecessary background

noise. After the SonicBAT  ights NASA

compared the data recorded by the

TG-14A with those of the ground arrays.

This gave researchers a better idea of how

atmospheric turbulence might in uence

sonic booms. The SonicBAT e ort will

develop two di erent models for the

e ects of turbulence on supersonic aircraft

noise, the aim being to make future

supersonic commercial aircraft quieter.

‘Edwards was the ideal location for the

 rst half of the SonicBAT program,’ said

Larson. ‘Here you can test in a dry and hot

environment and see how the turbulence

layer is in uenced by the rising heat

during the day.’ NASA expanded the tests

to the Kennedy Space Center in Florida

last summer.

Other programs are focusing on noise

reduction on take-o and landing or

improving fuel e ciencies and reducing

potentially harmful exhaust emissions.

For many years NASA has worked on

an improved ground and airborne

automatic collision avoidance system.

Larson explained, ‘I was involved in such a

program many years ago  ying the F-16.

I avoided giving too many details of the

test  ights to my wife, thinking she would

worry too much!’

Rising costs amid tight

budgets

NASA Armstrong has a reputation for

providing excellent value for money

NASA

UNMANNED

For mission support the T-34C Turbo

Mentor is used for research  ights,

photography and video. It is primarily

used for chasing unmanned aerial

vehicles (UAVs). NASA Armstrong

Flight Research Center operates

a modi ed MQ-9 Predator B and

two Global Hawks. The Predator

B — named Ikhana — is used for

medium-altitude and long-endurance

science missions. Ikhana also acts as a

testbed to improve the utility of UAVs.

NASA’s two Global Hawks o er a

range of 8,500 nautical miles and 24-

hour endurance that enables them to

operate worldwide. They have been

used intensively for hurricane studies

since 2010.

The skilled engineers

who work at NASA

Armstrong not only

maintain a venerable

and varied fl eet,

but make unique

modifi cations for test

work. Frank Visser

The F/A-18s are the

workhorses of the NASA

fl eet, performing a host

of duties including safety

chase. Frank Visser

UNIT REPORT // NASA ARMSTRONG

92 June 2018 //^ http://www.combataircraft.net

88-93 NASA Armstrong C.indd 92 19/04/2018 15:35