A single hydraulic component failure caused a B-2A stealth bomber to crash-land at Whiteman Air Force Base in December 2022, resulting in more than $300 million in aircraft damage, according to a U.S. Air Force investigation report released on Aug. 5.
Photo: USAF
The mishap occurred when a CryoFit hydraulic coupling failed during the aircraft’s landing gear extension on Dec. 10, 2022, causing rapid hydraulic fluid loss in both primary and backup systems. The failure forced the crew to perform an emergency gear extension, but the left main landing gear collapsed upon touchdown, dragging the aircraft’s left wing down the runway and igniting fuel that led to two explosions.
Both crew members escaped without injury from the aircraft, tail number 90-0041, assigned to the 509th Bomb Wing at Whiteman Air Force Base, Missouri. The investigation found no crew error contributed to the mishap.
Colonel Jesse W. Lamarand, who led the 18-month Accident Investigation Board, determined the truck position sequence valve hydraulic coupling failure was the primary cause. The coupling, which requires liquid nitrogen for installation, expelled from its fitting and created an opening that rapidly drained hydraulic fluid from both systems.
The failure prevented the right main landing gear from extending normally, prompting the crew to declare an in-flight emergency and execute emergency procedures. While all three landing gear appeared to indicate “down and locked” on cockpit displays, the left main landing gear had lost structural integrity due to the emergency extension process.
“The hydraulic fluid loss in the primary system, followed by an emergency gear extension, resulted in the hydraulic main landing gear lock actuator having insufficient hydraulic pressure to assist in holding the left main landing gear lock link assembly in place,” the report states.
Upon landing, a hydraulic pressure pulse from the truck position actuator overcame the weakened lock link assembly, causing the left main landing gear to collapse under the aircraft’s weight. The collapse caused the left wing to strike the runway and drag for several thousand feet before the aircraft came to rest 9,062 feet down the runway with its left wingtip on fire.
The investigation identified two substantially contributing factors beyond the coupling failure. First, main landing gear design vulnerabilities allowed the lock link assembly to move out of its required locked position during emergency extension procedures. Second, firefighting response delays allowed the fire to spread and cause additional external damage.
The incident commander initially restricted use of aqueous film forming foam, believing Air Force policy limited its use to last resort situations. This misunderstanding delayed the most effective fire suppressant for approximately three minutes and 28 seconds, allowing flames to spread before the left surge fuel tank exploded at approximately 1500 CST, followed by the left outboard fuel tank explosion 10 minutes later.
The CryoFit coupling failure represents a recurring issue across the B-2 fleet. The investigation found 25 recorded coupling failures fleet-wide, with 10 occurring in main landing gear hydraulic circuits. Five failures specifically involved truck position sequence valve couplings, with two resulting in left main landing gear collapses.
A similar incident in September 2021 led to the discovery that main landing gear lock springs did not meet specifications. The Air Force issued a technical order in March 2022 requiring replacement of lock springs and validation of proximity sensor rigging across the fleet. The mishap aircraft had completed this modification in June 2022 and recorded 33 landings before the December mishap.
Air Force Global Strike Command temporarily suspended B-2 flights following the incident to inspect the fleet while maintaining the ability to deploy aircraft for nuclear deterrence and long-range strike missions if needed. Full flight operations resumed on May 22, 2023.
The investigation could not determine the underlying cause of the coupling failure. Analysis including visual inspection, computed tomography, and scanning electron microscopy revealed no surface flaws, internal defects, or microcracking. However, witness marks on the exterior fitting suggested the coupling expelled during a single event.
Both crew members were qualified and current for the mission. The instructor pilot had more than 350 hours in the B-2A, while the co-pilot undergoing aircraft commander upgrade training had over 180 hours in the platform. Weather conditions were within prescribed limitations with overcast clouds at 1,000 feet and light winds.
The B-2A Spirit, manufactured by Northrop Grumman, is a multi-role stealth bomber capable of delivering both conventional and nuclear munitions. The aircraft is operated and maintained by the 509th Bomb Wing and Missouri Air National Guard’s 131st Bomb Wing at Whiteman Air Force Base under a Total Force Integration structure.
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