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Frozen
Pigs
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F-111
A8-144 undergoes testing in the Cold Proof Load Test Facility
at Amberley.
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AS Australia
prepares to swelter through another long, hot summer, temperatures
at RAAF Base Amberley have recently plummeted below -40 degrees
Celsius.
The freezing conditions, however, are restricted to inside the base’s
Cold Proof Load Test (CPLT) facility, developed to test the structural
durability of the Air Force’s F-111 fleet.
The facility was used in October for only the second time since
its commissioning last year, with an F-111 aircraft (A8-144) successfully
completing the testing process.
F-111 Support Project Manager Wing Commander Rex Burkhardt said
the CPLT was specifically designed to test F-111s, believed to be
the only aircraft in the world to be subjected to this form of structural
testing.
The facility was engineered to apply a specific load test to the
airframe of the aircraft in a controlled environment.
In October’s testing of A8-144, the aircraft was cooled using
liquid nitrogen to -43C
It took several hours for the aircraft to be brought down to test
temperature and, once stabilised, positive and negative “G”
loads were applied to the wings at two wing-sweep positions –
26 and 56 degrees.
The aircraft was specially instrumented with several hundred strain
gauges, which recorded data at a given load. An Acoustics Monitoring
System, consisting of an array of sensors placed on the airframe,
searched for cracks.
After a successful test, the chamber heating cycle commenced, bringing
the aircraft back to ambient temperature.
WGCDR Burkhardt said said the wing loading system was designed to
remove the load if a structural failure occurred, reducing secondary
damage.
“The aircraft may then be repaired and returned to service,”
he explained.
“If the structure does not fail then the aircraft can be certified
as safe for a given number of hours. A structural failure during
testing is not considered a test failure.”
Cold Proof Load Test facilities were first developed in the United
States in the 1960s, when flaws in the USAF F-111 fleet were discovered.
The Amberley CPLT facility was the fifth to be built and is the
only remaining facility in the world.
Boeing Australia Limited is the prime F-111 maintenance contractor
at Amberley and is responsible for maintaining the facility.
Owing to the size of the F-111 fleet, the CPLT facility will only
be used several times a year.
Amberley is scheduled to test another three F-111 aircraft in the
next six months.
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