The US Air Force (USAF) and Lockheed Martin have found a potential fix for the longeron cracks that were discovered in some of the service’s F-16 fighter aircraft.

In August, the USAF grounded 82 of its F-16D aircraft after an immediate time action compliance technical order (TCTO) found structural cracks in the canopy sill longerons between the front and rear pilot seats, as reported by Flightglobal.

US Air Force Materiel Command spokeswoman Sue Murphy said the proposed permanent repair would involve installing a strap over the cracked longeron, instead of replacing it.

In an e-mail to the publication: Murphy said: "The scope of work will involve removal of cockpit equipment to facilitate repairs, installation of the repairs, and reinstallation of the cockpit equipment.

"The longerons will not be replaced unless needed for other reasons (which at this point it not anticipated to apply to most jets)."

The cracked longerons are original to the aircraft, and were not upgraded under the Falcon Star programme, according to Murphy, who also noted that a temporary fix would have enabled quick resumption of flights, but was deemed risky and hence abandoned.

"Lockheed Martin is actively working with the US Air Force on a permanent repair solution for the canopy sill longeron cracks."

The cracks were discovered in two US F-16D groups, with the first including 39 aircraft with an average age of 27 years old with 6,455 actual flight hours (AFH) and 7,016 equivalent flight hours (EFH); the second group comprised of 43 F-16s averaged 21 years old with 5,934 AFH and 4,867 EFH.

In addition to this, the cracks were found in some F-16s flown by foreign countries.

A Lockheed spokesman said: "Lockheed Martin is actively working with the US Air Force on a permanent repair solution for the canopy sill longeron cracks.

"The repair drawing, as it is known, is now available and we will continue to support the air force as it works to implement, manufacture and verify the repair installation."

Commenting on return-to-flight timeframe, Murphy said the USAF is still trying to determine whether the repairs can be done in the field and the scope of testing required for return-to-flight will remain known until the repair process is complete.

Image: A USAF F-16D fighter aircraft in flight. Photo: courtesy of US Air Force Staff Sgt. Benjamin Wilson.

Defence Technology