Boeing’s long-troubled KC-46 tanker has hit been hit with a new setback, the company has confirmed, after the US Air Force (USAF) reported a new Category 1 fault with the aircraft.

According to a press release from the USAF, some KC-46 aircraft suffer from ‘excessive fuel leaks’. The USAF statement adds that the USAF and Boeing are ‘working together to determine the root cause and implement corrective actions’ to address the fault.

The KC-46 uses redundant fuel protection to prevent spills. However, aircrews have discovered fuel between the primary and secondary fuel barriers on some of the aircraft.

In a statement sent to Air Force Technology Boeing said that the USAF had found 16 KC-46 tankers needed fuel system repairs. Of that 16 Boeing has already completed repairs on seven of the tankers.

According to the USAF, the fault was initially detected in the summer of 2019, but added it had recently been raised to a Category 1 fault. Air Force Technology understands that the fault is being fixed at no cost to the US Government.

In a statement, Boeing said: “The US Air Force discovered 16 KC-46 aircraft requiring fuel system repairs. Boeing has already completed repairs on seven of the 16. The KC-46 fuel system is equipped with redundant protection for fuel containment. In some cases, with this issue, aircraft maintenance crews are finding fuel between the primary and secondary fuel protection barriers within the system.

“We are disappointed to learn of this development and are already implementing assembly and installation improvements to correct the issue. We will continue to implement repairs as needed. Boeing is working with the utmost urgency to address this issue.”

The fix is being installed on in-production airframes, however, The Boeing facility that manufactures the KC-46 has temporarily paused work until April due to the spread of the Covid-19 Coronavirus pandemic.

The KC-46 has been hit with a number of setbacks during development and production, with Boeing currently working on other Category 1 problems related to the aircraft’s Remote Vision System and issues with connecting the refuelling boom to some aircraft.

Despite the temporary halt to KC-46 production work, Boeing previously told Air Force Technology that works to correct the Remote Vision System were continuing.

The aircraft had previously been temporarily blocked from cargo-carrying duties owing to a now-fixed fault with cargo locks.

The USAF’s KC-46 programme office is implementing enhanced acceptance testing of the fuel system to identify any future faults with the system prior to delivery.