Boeing delivered three more KC-46A Pegasus in-flight refuelling tankers to the US Air Force (USAF) on 8 and 9 August, a week after winning a $55 million contract to redesign the aircraft’s boom telescope actuator.

Boeing is redesigning the actuator to address hardware specification flaws coming from the service’s initial design requirements. Designing and retrofitting the aircraft will likely cost more than $300 million, according to a Government Accountability Office (GAO) report released in June 2019. Programme officials told GAO that developing a solution, and receiving Federal Aviation Administration certification, would likely take three to four years.

The boom's issues became apparent during developmental flight testing, when pilots of lighter receiver aircraft – such as Fairchild Republic A-10s and Lockheed Martin F-16s – reported they needed more force to connect and disconnect their aircraft from the boom, as compared to older tankers, like the KC-135 and KC-10, says GAO.

The additional force required can cause the receiving aircraft to suddenly lunge and collide with the boom, damaging the aircraft’s glass cockpit canopy or tail. It can also damage the boom.

Boeing KC-46A Pegasus at factory

Boeing KC-46A Pegasus at factory


Testing also uncovered a problem with the KC-46’s remote vision system, a set of cameras used to guide the refuelling boom into an aircraft's fuel receptacle. Specifically, sun glare on the cameras at certain angles can cause washout or blackout on the refeulling operator's display screen. That makes it difficult to safely guide the boom into the fuel receptacle of an aircraft that needs refuelling. A wayward refuelling boom could damage an aircraft's nearby antennae or the radar-absorbent paint coating of stealth aircraft, such as the Lockheed Martin F-22, says GAO.

Boeing is expected to pay for fixing the remote vision system issue.

The USAF is using the remote vision system on tankers it has received, though it cannot use the cameras in some circumstances. Boeing says it is still in discussions with the USAF for a final fix for the system.

Deliveries of three more tankers in early August brings to 16 the number of KC-46s delivered to the USAF. Boeing had aimed to deliver 36 tankers in 2019. However, the service is expected to accept no more than three aircraft monthly, bringing the likely total number of tankers delivered by year-end to no greater than 28.

Boeing’s KC-46 deliveries to the USAF have been slowed, and at times halted, by issues with Foreign Object Debris (FOD) found inside the airframes. Boeing says it has implemented new FOD-awareness days and clean-as-you-go practices to eliminate the problem, but declines to say if FOD has been discovered in the aircraft in recent months.