The U.S. Air Force has grounded its fleet of 20 Northrop Grumman [NOC] B-2 Spirit stealth bombers after a Dec. 10 emergency landing of one of the aircraft at Whiteman AFB, Mo., the base for the 509th Bomb Wing.

The plane “experienced an in-flight malfunction during routine operations and was damaged on the runway at Whiteman Air Force Base after it successfully completed an emergency landing,” the wing said. “There were no personnel injuries. There was a fire associated with the aircraft after landing, and the base fire department extinguished the fire.”

On Dec. 16, the wing said that Boeing [BA] B-1B Lancers from Ellsworth AFB, S.D., would take the place of the B-2 at the 2023 Rose Parade and Rose Bowl Game flyovers and that Whiteman would have a “safety pause of B-2 flights in order to inspect the fleet” following the Dec. 10 emergency landing.

“Our number one concern is the safety and security of our personnel and fleet,” Air Force Col. Daniel Diehl, 509th Bomb Wing commander,” said in a statement.

The B-2 is one of just four out of 49 DoD aircraft that met mission capable rates–measuring number of aircraft able to perform one mission–in at least six years between fiscal 2011 and fiscal 2021 (Defense Daily, Dec. 15). Nevertheless, the B-2 did not meet another metric–the number of mission capable aircraft available for flight operations–in any of those years. Some mission capable aicraft are not on the flight line, but instead are undergoing depot-level maintenance or in storage.

“The B-2 program has been experiencing delays in scheduled maintenance and increased unscheduled maintenance, according to program officials,” according to a Government Accountability Office (GAO) report last month, Weapon System Sustainment Aircraft Mission Capable Goals Were Generally Not Met and Sustainment Costs Varied by Aircraft (GAO-23-106217).

“The officials stated that the aircraft-level programmed depot maintenance process for the two most recent aircraft experienced delays of 40-plus days due to parts availability, the addition of non-standard work, and an increase in the number of aircraft in-progress at the depot,” the report said. “Further, they said some commodity depot-level repairs of support equipment were experiencing delays of over 1 year. Program officials also stated that many of the B-2 line replaceable units, including radar system components, are beyond their life expectancy and have been experiencing decreased mean time between repairs, leading to increased unscheduled repair requirements.”

GAO also said that the B-2 program has had problems gaining access to technical data for depot-level repairs at Air Force Air Logistics Complexes, as such data is proprietary to Northrop Grumman.

The B-2 program office said that it “has found it necessary to take administrative actions to shift the organic depot workload to the commercial sector in order to provide adequate support to the weapon system,” per the report. “There are also shortages of trained maintenance personnel. For example, according to program officials, many of the B-2 commercial and organic depot repair facilities have only one person available who is trained to perform a specific type of B-2 maintenance.”

In addition, B-2 program officials told GAO that “because of the age and low number of aircraft in the B-2 fleet, there are numerous diminishing manufacturing sources, parts obsolescence, and parts shortage issues.”

“The flex cable on the fuel vent control valve is an example of a part with diminishing manufacturing sources; microcircuits and circuit card assemblies are examples of parts with obsolescence issues,” the report said. “The fuel vent control valve is a part with shortages. These issues routinely lead to the practice of cannibalization—taking a working component from one aircraft to install it on another aircraft. While this process mitigates an immediate need, it is inefficient. The B-2 program office has been working to improve the availability of parts. Supply chain improvement efforts include redesigning obsolete hardware to ensure that aging parts are procurable and reparable for the future.”