Boeing, the US Air Force and US Navy completed electromagnetic effects (EME) testing on the KC-46A tanker during July, checking off another step before the manufacturer can deliver its first of the 767-based aircraft to the USAF at the end of this year.

The EME test process evaluated the tanker’s ability to fly through electromagnetic fields produced by radars and radio towers. Boeing tested its second low-rate initial production aircraft in the full tanker configuration, including the type's Cobham wing aerial refuelling pods. During simulation, the aircraft received pulses from a large transformer positioned above it, which tested the KC-46A’s electromagnetic pulse protection in flight.

“The KC-46 tanker is protected by various hardening and shielding technologies designed in to the aircraft to negate any effects,” says Boeing programme manager Mike Gibbons. “This successful effort retires one of the key risks on the programme.”

EME testing had been slated for completion in May, according to a US Government Accountability Office (GAO) report issued earlier this year. The same report stated that if test points were not completed at the planned rate, the already revised delivery schedule for the KC-46A would be "optimistic at best".

Boeing counters that the GAO’s report is based on information gathered a year ago, and that the pace of EME testing has not affected its delivery schedule. The company plans to deliver the first aircraft before the end of 2017, and meet the USAF's "required assets available" milestone as scheduled during October 2018.

The EME tests may tick off a significant risk, but the milestone does not mark the final phase of certification. Boeing still requires an amended type certification from the US Federal Aviation Administration for the baseline 767 with tanker provisions, and a supplemental type certification for the militarised variant. The company says it is currently wrapping up its work in support of the first of these tasks, and ramping up testing for the latter.

The air force has previously said it will have greater confidence in the programme’s schedule once Boeing secures the final design approvals from the FAA, which will allow it to conduct a final set of certification flights necessary for delivery. Boeing says it expects to receive the approval as early as August.