Faulty seals are to blame for the leaky fuel system on the US Air Force (USAF) Boeing KC-46A Pegasus aerial refuelling tanker, according to a company executive.
Jamie Burgess, Boeing KC-46A tanker vice-president and programme manager, told reporters on 2 April that the ‘U Cup’ seals are particularly difficult to install and more sensitive to the company’s installation technique than it was initially thought. The KC-46A’s fuel system is designed to flex and move as the aircraft flies, so there are many flexible valves from which fuel will slowly leak if they are not properly installed.
A KC-46A Pegasus arrives at McConnell Air Force Base, Kansas, on 10 January 2020. Leaky ‘U Cup’ seals are causing the KC-46A’s fuel system to leak between its protection barriers. (US Air Force)
The USAF announced on 31 March that the KC-46A’s fuel system was leaking excessively in 16 aircraft and that the issue was being upgraded to the most serious deficiency: Category 1. The fuel system is equipped with redundant protection for fuel containment and aircraft maintenance crews were finding fuel between the primary and secondary fuel protection barriers.
Burgess said that maintainers found ounces of fuel present between the two protection barriers and that they are required to check this space for fuel frequently. The KC-46A’s fuel system, he said, is designed to carry just over 90,718 kg of fuel for an aerial-refuelling mission, which is 30% more than carried in a standard 767 commercial aircraft.
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