The US Air Force (USAF) has banned the Boeing KC-46A Pegasus in-flight refueling tanker from carrying passengers and cargo after it discovered cargo floor restraint devices unlocking during a recent operational test and evaluation flight.

“During several KC-46 test flights in which cargo was being transported, multiple cargo floor restraint locks malfunctioned and came unlocked. Prior to departing for each of these missions, aircrew fully installed, locked and thoroughly inspected each restraint, and performed routine inspections of the restraints in flight,” says the USAF. “Despite these safety measures, the unlocking of cargo floor restraints occurred during flight, although no cargo or equipment moved and there was no specific risk to the aircraft or crew.”

The flight restriction was first reported by Defense News and confirmed by FlightGlobal.

Though primarily an in-flight refueling tanker, the KC-46A is often used to carry passengers and cargo on its main deck. Depending on its configuration, it is FAA certificated for 58 passengers or 18 463L pallets. Cargo and passengers sit on different types of rolling pallets that lock into the aircraft’s floor.

Boeing KC-46A Pegasus

Boeing KC-46A Pegasus


The floor restraints are designed to prevent those pallets from shifting during flight, an event which might endanger the aircrew and aircraft, says the USAF. After discovering the restraint failure, the service has labeled the issue a category 1 deficiency. It says it is working with Boeing to figure out a solution.

The USAF points out that “category 1 deficiencies are those which may cause death or severe injury; may cause loss or major damage to a weapon system; critically restricts the combat readiness capabilities of the using organization; or results in a production line stoppage.”

For its part, Boeing says it is aware of the issue.

“The company and the Air Force are cooperatively addressing the issue and analyzing the locks to determine root cause,” the airframe manufacturer says in a statement. “The safety of the KC-46 aircraft and crew is our top priority. Once a cause is identified, the tanker team will implement any required actions as quickly as possible.”

Regarding responsibility for the expense of fixing the faulty restraints, Boeing says “it’s too early to talk about costs.”

Faulty restraints bring the KC-46’s number of category 1 deficiencies to four. Two of the tanker’s category 1 deficiencies are with its Remote Vision System, a set of cameras used to guide the refueling boom. The system’s video screen washes out or blacks out due to sun glare at certain angles and it has clarity issues which in testing has caused operators to accidentally touch the boom to the skin of aircraft receiving fuel. The last issue is with the stiffness of the boom, which makes it difficult for lighter aircraft to properly connect to the tanker.

The boom stiffness problem stem from the USAF not specifying in its contract the amount of force needed to compress its boom to lighter aircraft. Boeing is faulted for the two Remote Vision System problems. The source of the floor restraint problem is not yet known.

In addition to category 1 deficiencies, Boeing has struggled repeatedly with leaving behind foreign object debris (FOD) inside KC-46A tankers delivered to the USAF. The service has found tools, rubbish and left-over parts such as loose nuts during inspections.

The FOD-related “lapse in quality assurance [and] attention in detail” comes from “cultural” problems at Boeing, said Will Roper, USAF assistant secretary of the air force for acquisition, technology and logistics, at the Paris air show in June. Boeing had aimed to deliver 36 tankers in 2019, but Roper said that receipt of tankers would be slowed to deal with quality problems, so the company will likely miss that target.

Boeing did not respond to a question about how it would change its processes or management to resolve the programme’s mounting list of problems.