DAYTON, Ohio–The U.S. Air Force is working to resolve six Category 1 deficiencies on the Boeing [BA] KC-46A tanker, including Auxiliary Power Unit (APU) drain mast cracking that resurfaced as a critical problem.
“We’re down to six Cat 1 DRs [deficiency reports],” Air Force Col. William Ottati, the system program manager for the KC-46A, told reporters on July 31 during a briefing at the Air Force Life Cycle Management Center’s (AFLCMC) annual industry days conference here. “We downgraded the flight management system instability Cat 1 DR back in April to Category 2. We’re gonna do that [testing] over a period of time to ensure that all the software fixes are working.”
The Air Force said that it has collaborated with
General Electric‘s [GE] aerospace subsidiary on a software fix to resolve instability of the KC-46A flight management system, which provides flight guidance and navigation instability (Defense Daily, Jan. 27, 2022).
The six Category 1 deficiencies include two for the Remote Vision System (RVS) 2.0; a stiff boom, which presents problems in refueling some, lower speed aircraft, like the A-10; receptacle drain line cracking; and two Product Quality Deficiency Reports (PQDRs)–one for fuel manifold leaks and the other for the cracking in the APU drain mast.
Honeywell [HON] in Phoenix supplies the KC-46A APU, located in the tail of the aircraft in front of the exhaust. APUs provide start-up engine power and back-up electrical power for avionics, communications, flight control and other systems on aircraft.
Ottati said that “we still have challenges and risks with RVS 2.0” but that the Air Force is collaborating with Boeing and RTX‘s [RTX] Collins Aerospace to complete RVS 2.0 development in late 2025.
For the stiff boom, the identified fix is Moog‘s boom telescope actuator redesign (BTAR), which recently had a test readiness review. “There are still some challenges with BTAR,” but the Air Force expects a BTAR development solution in early 2025, although long lead items may push back the retrofit of that fix, Ottati said.
For the PQDR fuel manifold leaks, Boeing has installed a fix and “is doing a good job retrofitting those fuel manifolds” at Cecil Field in Jacksonville, Fla., Ottati said, but the Air Force is awaiting additional data to ensure the right fix is in place.
On the APU drain mast Category 1 deficiency, the Air Force downgraded it to Category 2 “too soon,” he said. “We thought we had a fix, downgraded it to a Cat 2. Turns out there was still vibration cracking in the drain mast. That one’s still a Cat 1 DR. We have the fix. It’s a newer, more robust drain mast; beefed up APU doors…Those are all being retrofitted at Boeing at Cecil Field.”
Boeing is developing a fix for the receptacle drain line cracking, which may cause fuel to enter the flight deck. A fix for that Category 1 deficiency is to start flight testing in August or September, Ottati said.
Five of the Category 1 deficiencies–all except the receptacle drain line cracking–have lingered since at least 2020 (Defense Daily, Oct. 27, 2020). In March 2021 the Air Force identified the problem with receptacle drain line cracking at freezing temperatures.
On lessons learned from the KC-46A, Kendall has said that cost-plus, rather than firm fixed price contracts, may be a better course for many programs that incur some level of development risk.
“There’s much more to it [the KC-46A] than slapping a boom on a commercial derivative aircraft,” Ottati said on July 31 in response to a question on KC-46A lessons learned.
“My 30 plus years in this business I see oft times in competitive acquisition that industry and the government both do not fully understand the scope of what is being asked, what is the development that’s really necessary,” Scott Boyd, AFLCMC’s deputy program officer for mobility aircraft, told reporters on July 31. “There’s probably good, rare examples where it goes exactly as you expect because it is so well understood, they quoted the proposal exactly what they really needed to do, and it was done exactly on time, but you know so often that’s not the case.”
Boyd and Ottati also discussed the KC-135 Tanker Recapitalization program under which Air Force leaders have said that the service may buy 75 commercial derivative tankers as a stopgap toward the development and fielding of the Next Generation Air Refueling System (NGAS), formerly known as KC-Z. The KC-135 Tanker Recapitalization program replaces the canceled KC-Y effort under which the Air Force would have bought up to 150 commercial “bridge tankers.”
The Air Force plans to approve a final requirements document under the Joint Capabilities Integration and Development System (JCIDS) process for the KC-135 Tanker Recapitalization program by the end of September. Following on the heels of that JCIDS-generated, formal requirements document, the Air Force plans to release a request for information and a system requirements document on the KC-135 Tanker Recapitalization effort for industry response.
The Air Force also plans to conduct an Analysis of Alternatives (AoA) in fiscal 2024 on NGAS, which is to supplement the KC-46A and the KC-135 Tanker Recapitalization aircraft (Defense Daily, March 7). The AoA is to examine various attributes, including stealth, advanced protection systems, connectivity, and improved range/fuel efficiency that NGAS may need to operate effectively against high-tech adversaries.
Last month, Air Force Gen. Jacqueline Van Ovost, the head of Transportation Command, said that NGAS would likely leverage artificial intelligence to enable autonomous logistics (Defense Daily, June 6).
“It’s that NGAS capability, as the Secretary [Kendall] likes to call it, that scares China, and therefore, I want that in now as soon as we can so the tanker recap has become this accordion to try to adjust for bringing in NGAS,” Boyd said on July 31. “The total number of aircraft that we’re gonna procure under this tanker recap is gonna be dependent on how quickly we can get it on contract and how quickly NGAS delivers, and that’s why we’ve been reluctant to quote some specific number or specific rate because there are still a lot of things to work out.”
The Air Force is examining a buy of 15 KC-135 Tanker Recapitalization aircraft per year to help replace the KC-135s and accelerate NGAS.
While Air Force leaders have mentioned the KC-46A tanker as the favorite for the KC-135 Tanker Recapitalization program, Boyd said that the latter will be an open competition.
The requirements that fed JCIDS “are not revolutionary,” Boyd said. “They’re not, ‘We need a new design aircraft because there’s no way existing aircraft can meet these requirements’….But we still have to do our due diligence.”
“The requirement that went in [to JCIDS] does not call out for a KC-46,” he said. “It doesn’t say, ‘Buy a KC-46.’ It’s a traditional requirements document that talks about performance and supportability; etc. The assumption anytime when those requirements go in is we need something that does that, but we don’t know the market yet. Requirements generation did not assume a KC-46. Now we just have to wait for market research to tell us if there’s competition.”