DAYTON, Ohio—More than six years after the Air Force identified the first serious deficiency on the KC-46 tanker, six Category 1 deficiencies still remain and a seventh was downgraded to Category 2 in April, said Col. Leigh Ottati, chief of the KC-46 program office—the first public announcement of that development
Ottati detailed the deficiencies still plaguing the Pegasus during the Life Cycle Industry Days conference last week and shared updated timelines for resolving some of them.
The Air Force defines a Category 1 deficiency as one which “may cause death, severe injury, or severe occupational illness; may cause loss or major damage to a weapon system; critically restricts the combat readiness capabilities of the using organization; or result in a production line stoppage.” Category 2 defects, meanwhile, “impede or constrain successful mission accomplishment.”
The Government Accountability Office noted seven Category 1 deficiencies on the KC-46 in January 2022, and 19 months later none have been fully resolved. The Air Force worked with subcontractor GE Aerospace to develop a software fix for issues with the KC-46’s flight management system, Ottati said, but while the fix appears to be working it remains under observation.
“We’re going to do that for a period of time to make sure that all the software fixes that are out there are working, which they have been, and then we’ll close that deficiency completely,” he said.
RVS 2.0
The most prominent problem for the KC-46 is its troubled Remote Vision System, the camera and video system boom operators use to refuel other aircraft. The Air Force claims two Category 1 deficiencies related to the RVS, one of which causes the other. In certain lighting conditions, the boom operator is unable to see the receptacle clearly, and that can result in damage to the receiving plane if the boom scrapes against that aircraft. Aircraft like the B-2 and F-22 that have special stealth coatings are particularly susceptible to damage. The planned fix, a brand-new system RVS 2.0 solution, isn’t expected to be ready until 2025, Ottati confirmed. Contractor Boeing offered its first look at RVS 2.0 to Air & Space Forces Magazine late last year, saying it hoped to field them by October 2025.
“We still have challenges and schedule risks with RVS 2.0, but right now, we’re working closely with Boeing and their main subcontractor, Collins, on continuing to progress well with that, and intending to complete the development in late ’25 as previously reported, and then go straight into retrofits,” Ottati said.
Once RVS 2.0 is ready, Boeing will retrofit the Air Force’s KC-46s at Cecil Airport in Jacksonville, Fla., with the process taking about two months, Ottati said.
In the meantime, Boeing and the Air Force are still trying to close out the last “critical action item” from RVS 2.0’s critical design review, which has been ongoing since June 2022.
“The last critical action item had to do with the FAA certification plan for the commercial off-the-shelf cameras that are in the RVS 2.0 solution,” Ottati said. We’ve been working very closely with Boeing and the FAA on that and we have a good path forward and expect to close out that last critical action from CDR this quarter, so by the end of September.”
Stiff Boom
Another deficiency identified more than half a decade ago is “stiffness” in the refueling boom—certain aircraft that can’t produce as much thrust, such as the A-10, cannot provide enough force to keep the boom in place during refueling.
The problem is the boom’s actuator, which “drives the boom out in the telescope direction, and then when a receiver connects with it, the receiver drives the boom back into sort of a nominal refueling position,” Boeing KC-46 Program Manager James Burgess previously told Air & Space Forces Magazine.
Rather than redesign the entire boom, Boeing and the Air Force have opted to redesign the actuator, but developing a compliant actuator has proven difficult, Ottati said.
“We just recently had a Test Readiness Review meeting with Boeing and [subctontractor] Moog, and there’s still some challenges with [the boom telescope actuator redesign],” Ottati said. “Right now, we’re still expecting an early fiscal 2025 completion of the development for BATR [the telescoping boom actuator replacement]. And we have some margin until we can start retrofit, because of the long lead items for the retrofit portion. But we’re still struggling a little bit with the BTAR schedule and working closely with Boeing and Moog to make sure that we don’t eat up that margin that we have between the finishing of development and the start of retrofit, based on again, those long lead items.”
Quality Deficiencies
The remaining Category 1 deficiencies are all related to KC-46 product quality, Ottati said.
One is related to the tanker’s auxiliary power unit’s drain mast on the outside of the tail, which could potentially crack or break loose. The Air Force previously downgraded that deficiency to a Category 2, believing it had an interim fix, but backtracked after cracks continued to appear, Ottati said. Boeing is developing a long-term fix—“a newer, more robust drain mast, beefed-up APU doors,” Ottati said, but USAF is being cautious before declaring the problem solved.
“[We want to] make sure we have the right data, the appropriate data to ensure that we’re not seeing the same excessive vibrations and cracking in APU drain masts,” Ottati said. “And I say appropriate data because it’s primarily at high speeds with the boom lowered that we were seeing those kind of vortices in the back of the aircraft that were causing that vibration. So I want to make sure we have a significant amount of flight hours showing that those drain masts are not an issue any longer. Maybe six months or longer before we will look at potentially downgrading those and downgrading that one as well.”
Another deficiency is bad seals, that lead to fuel system leaks. Boeing officials say they’ve redesigned the valve seals to make them easier to install, and both Boeing and Air Force officials say they’re seeing far fewer leaks as a result.
But Ottati said he’s not ready to declare that deficiency resolved either.
“We’ll analyze in the next six months if that’s one we could downgrade and close at some point,” he said. “I don’t want to close … prematurely. I want to make sure that we have the right fix and plan for the retrofit for the entire fleet that’s affected.”
The final product quality deficiency relates to cracks in a drain line. “It’s a drain line that comes from the receptacle of the KC-46, through the flight deck, and then exits out the bottom of the aircraft—primarily for any excess fuel or water or anything like that to make sure that it doesn’t stay within the receptacle and drains,” Ottati said. “And what we’re seeing is because of the design, in cold temperatures with remaining water or fuel in the line, that drain line was cracking, creating the potential that there could be fuel on the flight deck.”
Progress on that fix has been slowed by the need for FAA certifications, but Boeing is hoping to begin flight testing a solution in the next month or so. After that, Ottati said, the Air Force will finalize the design and retrofits will begin.