The U.S. Air Force has resolved two of the six Category I deficiencies for the Boeing [BA] KC-46 tanker, the commander of Air Mobility Command (AMC), Air Force Gen. Jacqueline Van Ovost, said on Feb. 1.

“We just released as of Friday night, we went from six Cat I deficiencies down to four Category I deficiencies,” she told reporters during a Defense Writers Group virtual session. “We eliminated the Auxiliary Power Unit [APU] deficencies. Those two deficiencies that we eliminated were really associated with the maintenance of the APU and some component pieces. We have a fix in place, and we’re confident that we’re moving forward. That does not change the operational concerns, which are really relevant in the first three Category I deficiencies–two with the Remote Vision System and one with the telescopic boom. Those are the ones that really stop us from full operational capability and that will be fixed with the release of RVS 2.0 and the new boom telescope actuator device.”

Last year, the Air Force identified six Category I–critical–deficiencies with the KC-46A: two Category I performance deficiencies with the Remote Vision System (RVS); a performance deficiency with the boom telescope actuator for connecting the refueling boom with slower aircraft, such as the A-10; a product quality deficiency report (PQDR) related to fuel manifold leaks; a PQDR related to the APU drain mast; and a PQDR related to Auxiliary Power Unit (APU) duct clamp cracks (Defense Daily, Oct. 27). The Air Force has said that it has worked with Boeing to plan out fixes, including a new RVS 2.0 and a more pliant standard for the boom.

RVS 2.0 is to allow air refueling operator station (AROS) personnel in the front of KC-46A aircraft to steer refueling booms using Collins Aerospace [RTX] cameras on the fuselage.

In June, the Air Force said it had pushed back KC-46’s timeline for Initial Operational Test & Evaluation, as well as delaying a full-rate production for the program until at least fiscal year 2024 (Defense Daily, June 10). Van Ovost said on Feb. 1 that RVS 2.0 and a fix for the boom telescope actuator will be in place by fiscal year 2024 and that AMC still plans to have 179 KC-46s in the inventory by 2029 to supplement the 300 platinum anniversary Boeing KC-135s that will still be in operation.

Boeing has delivered 42 KC-46s to four Air Force bases thus far: McConnell AFB, Kan., which is to be a “super tanker base”; Altus AFB, Okla., the tanker training base; Pease Air National Guard Base, N.H.; and Seymour Johnson AFB, N.C.

The Air Force said that it first noticed the cracks on the APU duct clamps during KC-46A ground maintenance at Altus AFB on June 7, 2019.

“This discovery resulted in a June 11, 2019 product quality deficiency report (PQDR),” per the Air Force. “Boeing is using a more robust APU duct clamp design, utilized on the Boeing 777 [airliner], to resolve this deficiency. The improved clamps are being installed at no additional cost to the government. Retrofits are expected to be complete in early to mid-calendar year 2021.”

Van Ovost said on Feb. 1 that Boeing and the Air Force have installed the APU duct clamp fix on 70 percent of the KC-46 fleet so far and will have the entire fleet retrofitted “very shortly.”

The APU duct clamp in the tail of the KC-46 “was moving and causing some problems,” Van Ovost said on Feb. 1. “We’re confident that the clamp fix is the final fix based on their [Boeing’s] experience with the commercial [777] aircraft and how they did the redesign on that.”

On the resolution of the PQDR Category I deficiency related to the APU fuel drain mast–a small metal piece on the back of the airplane, Van Ovost said, “There were some quality issues with a spot weld that would cause a piece to potentially break loose off of the aircraft.”

Boeing “re-designed it into a single cast, and they are working through the retrofit option right now,” she said. “All of the airplanes that are flying right now and doing our testing all have that modification. Everything seems to be going well. Our engineering team has authorized to take that one [Category I deficiency] off the list. That doesn’t mean we’re not tracking it. If something happens, we’re going to watch, as it ages out. Those are moved down. We still have Category I and Category II deficiencies that Boeing is getting after, closing out all the time. But if we find another deficiency where we have an issue with safety of flight, we will absolutely flag that up into the Category I status. This is pretty normal in the development of airplanes and capabilities that we bring on, that we have different deficiencies that get elevated and then get fixed.”

While the Air Force and Boeing have said that the APU duct clamp cracking did not pose a safety risk, an APU duct clamp detachment can have safety consequences. On May 14, 2017, the cabin of a Boeing 737 flying from Prague to Djerba Zarzis International Airport in Tunisia depressurized at 32,000 feet, likely due to an APU bleed duct leak created by the detachment of a loose clamp on the APU duct valve seal, according to the Flight Safety Foundation. Passenger oxygen masks deployed automatically, as the flight crew donned their masks, conducted an emergency descent to 10,0000 feet and landed at Munich Airport in Germany without incident.

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.

In one celebrated APU incident, Chesley “Sully” Sullenberger, a retired Air Force fighter pilot, was able to ditch U.S. Airways Flight 1549 on the Hudson River on Jan. 15, 2009 after a flock of Canada geese hit the plane and caused engine failure. The Airbus A320-214 had an Integrated Drive Generator on each engine. Sullenberger started up the Honeywell 131-9A APU to ensure flight controls, avionics and other systems kept running, as the aircraft skidded onto the Hudson River around midtown Manhattan. All 155 people aboard were rescued.

On Feb 1, Van Ovost also said that AMC is looking to make its aircraft, such as the KC-46, the KC-135, and the Lockheed Martin [LMT] C-130, nodes in the network for the Advanced Battle Management System (ABMS). For instance, AMC is to experiment with the antenna on the Boeing C-17 to process data “at the edge” and transfer that data to fifth and fourth generation fighter aircraft. That experimentation is to kick off this month during the annual Cope North exercise among the Air Force, the Japan Air Self Defense Force and Royal Australian Air Force, Van Ovost said.

Acting as cell towers to relay data between the cloud and front-line forces in future conflicts, refueling tankers are to play a significant role in the service’s fielding of ABMS.

A number of boom operators and former boom operators have praised the eyes-on, manual steering employed on KC-135s and KC-10s and are skeptical of RVS and the remote steering technology on the KC-46.

Mike Runyan, a retired KC-135 boom operator, recalled telling Boeing engineers not to pursue a remote refueling approach at the 2009 annual boom symposium held at the Air Force boom operator schoolhouse at Altus AFB, Okla.

“We told them not to do it,” Runyan said in a telephone interview last year with Defense Daily. “The retired boom operators and even the active duty ones said don’t do it because of the experience we had in the back of the airplane. You could see what was going on for peripheral vision, eyes on the target. Now, instead of a boom operator, you have a panel operator [with the KC-46A]. The idea to ‘fly, fight, and win’ is really compromised. When your computers go down, you can’t see the receiver in the back. It’s a poor airplane really. I wouldn’t fly in one.”

Van Ovost said on Feb. 1 that “the challenges we’ve been having right now with the current Remote Vision System have caused the angst within the fleet partners, within the KC-135 and KC-10 fleet boom operators.”

But Van Ovost said that KC-46 pilots and boom operators at the four KC-46 bases thus far are becoming more confident in their abilities to operate RVS once the latter meets all the requirements. “I think that this is just a transition to a new way of doing things, looking through a screen, versus looking through a window out of the airplane,” she said. “Frankly, no matter how we did it, it was very uncomfortable [for boom operators] in the back of the airplane. This is a much more capable airplane for both agility because we can do drogue and probe–two different types of refueling–but also for the comfort of the boom operator, once we get the issues fixed with the Remote Vision System.”

The Air Force is looking into a non-developmental “bridge tanker” to supplement the KC-46s and the remaining KC-135s, as the service develops the next-generation KC-Z, which could have a number of attributes, including autonomy and stealth.

Lockheed Martin [LMT], for its part, has broached the idea of a stealthy, autonomous tanker.