A small model hidden away on Goodrich's stand (Hall 4, E9) illustrates the advanced technologies being used to extend the F-15 Eagle's service life, pending the introduction of the F-22 Raptor. On show is Goodrich's Grid-Lock technology, being used to replace the aluminium honeycomb components used in the F-15.
The older F-15s now in service are already reaching the end of their planned service lives and are exhibiting signs of ageing. Most seriously, the lightweight honeycomb structures used in parts of the F-15 have raised concerns. Over the years, water ingress can cause difficult to detect corrosion. This was starkly demonstrated in the of spring 2002, when an F-15 from Eglin AFB, Florida, suffered a catastrophic failure and broke up over the Gulf of Mexico, killing its pilot.
Inspections carried out every 200 hours had not revealed any indication of any structural flaw or defect, but when the wreckage was recovered, it became clear that honeycomb components in the left vertical tail had suffered a structural failure, leading to a catastrophic loss of control.
In 2002 the USAF launched a six-year programme to replace the aluminium honeycomb components used in the F-15 with components using Grid-Lock technology. The major components affected included the leading edge and trailing edge of the tailplanes, the fin leading edge, wingtips, ailerons and flaps.
Grid-Lock uses state-of-the-art CAD/CAM and CNC manufacturing systems to produce complex structures that are robust and low cost. They have better strength-to-weight characteristics than current metallic, composite, and bonded sandwich structures, and do not have water retention and corrosion problems.
JON LAKE
Source: Flight Daily News
