The US Air Force has fully come to grips with the lessons from a Northrop T-38C crash last year that claimed the lives of two pilots. But the accident again spotlights the risks and fears of operating aircraft fleets far beyond their original design limits.

The USAF safety investigation blames the crash on a 11.4cm (4.5in)-long aileron actuator. It failed when the pilot performed pre-flight functional checks of his control surfaces, and he never knew he was taking off with an aileron stuck in an extended position.

The good news is that USAF officials immediately took action. The fleet was grounded. A Herculean effort by the USAF depot produced 3,000 replacement actuators in three months. The USAF also thoroughly investigated whether any of 4,000 other parts in the T-38's flight control systems was at similar risk of failure.

By any reasonable measure, the USAF has taken the proper precautions and confidence in the T-38's basic safety is back to the level it was before the crash.

But the bad news is that the T-38 is a 50-year-old airframe design, last produced in the early 1970s. The high-time aircraft in the fleet has 16,000 flight hours. The T-38 was designed to be retired after 7,000 flight hours. On average, the T-38 fleet is flying into its third lifetime. Yet the USAF plans to continue operating these perpetual trainers until the last one is retired in 2026.

Operating aging aircraft well past their intended lifetimes is possible, but extremely risky. It's not unlike flying the first few aircraft during a flight test phase. Surprises - like a cracked aileron actuator - can occur.

The USAF has responded correctly to the specific T-38 problem. But the underlying issue remains. As long as the USAF is forced to operate geriatric trainers and combat aircraft well past their intended design lives, basic safety principles cannot be observed.

Source: Flight International