08-07-2025, 11:50 PM
On December 10, 2022 B-2A 90-0041 "Spirit of Hawaii" departed Whiteman AFB as part of a two ship formation, flying as DEATH12. The mission was to be a spare aircraft for another B-2 that was to fly to Joint Base Pearl Harbor-Hickam. To ensure that at least one aircraft arrived, two were launched from Whiteman. Upon reaching the decision point, with the primary aircraft being healthy, DEATH12 was ordered to return to Whiteman. The crew had an uneventful flight until final approach to Whiteman AFB.
They were cleared for a standard ILS approach, and at about 200 knots the Pilot Monitoring, who was a B-2 Instructor Pilot, lowered the landing gear. The Left Main, and nose gear deployed normally and showed locked, but the Right Main failed to extend. The crew received a primary and secondary hydraulic system caution indicating a hydraulic leak. The B-2 hydraulic system has several parts, including monitoring system, pumps, reservoir, accumulators, and high pressure subsystems. The primary and back up systems normally don't exchange fluid, but when switching between systems some fluid may be exchanged between the two systems.
The plumbing of the hydraulic systems uses titanium tubing, and CryoFit fittings are used to join two lines together. A CryoFit coupling is a sleeve that goes over both lines, with internal knurling to add tensile strength to the joint. When the CryoFit coupling is prepared to be used, it's dipped in liquid nitrogen, and a tapered mandrel is pulled through the coupling expanding its size.
![[Image: CryoFit%20expanded.jpg]](https://denyignorance.com/uploader/images/CryoFit%20expanded.jpg)
The two lines are passed into the coupling, and it's allowed to return to room temperature. As it returns to room temperature, the coupling shrinks back to its normal size, and the knurling bites into the lines, creating a fluid tight seal, and creating a "pooch", which resists tension pull out loads.
![[Image: CryoFit%20relaxed.jpg]](https://denyignorance.com/uploader/images/CryoFit%20relaxed.jpg)
The B-2 main landing gear consists of the Truck Beam, Shock Strut, Upper and Lower Drag Braces, and the Lock Link Assembly, which consists of the Upper and Lower Lock Links, Lock Link Springs, the MLG Lock Actuator, and Truck Position Actuator. The gear is extended via the landing gear handle, or the Landing Gear Emergency Lowering Switch. The FCCs, PSLUs, and proximity sensors handle the retraction and extension, and are hydraulically actuated.
![[Image: B-2%20MLG.jpg]](https://denyignorance.com/uploader/images/B-2%20MLG.jpg)
The PSLUs issue driver commands to both the Left and Right Main Landing Gear, which have separate drivers independent of each other. Once the gear are down, the MLG Lock Link Assembly rotates to the overcentered position, locking the landing gear in place, and the truck beam rotates the wheels to the toe-down configuration for landing.
![[Image: B-2%20Lock%20Link%20Assembly.jpg]](https://denyignorance.com/uploader/images/B-2%20Lock%20Link%20Assembly.jpg)
During emergency extension, accumulated pressure is used to lower the landing gear, the Lock Link is rotated to overcentered, as normal, but the link is held in place by two springs, that apply about 100 pounds each of force on the Lock Link Assembly. On the Mishap Flight, when the landing gear handle was lowered, the hydraulic system pressurized, and all three landing gear doors unlocked and began to cycle, but the Right Main Landing Gear (RMLG) CryoFit coupler failed, separating the two lines and allowing hydraulic fluid to leak, and pressures to drop low enough to trigger the warnings in the cockpit.
The leak prevented hydraulic fluid from reaching the RMLG sequence valve, keeping the RMLG locked. The door cycled open and closed repeatedly as the system switched between primary and back up systems. The FCCs switched six times, attempting to unlock the right mains, but failed due to lack of hydraulic fluid. The crew almost immediately performed an emergency gear extension, and were able to get three green in the cockpit showing all three landing gear were down and locked.
The crew landed approximately 1,000 feet down the runway at Whiteman, and the left main failed almost immediately. The aircraft dropped onto the landing gear door, and the landing gear folded into the wheel well. The aircraft began sliding down the runway, with the left wingtip dragging along the runway, and eventually the grass beside the runway. At approximately 8700 feet down the runway, the left wing dragged across a taxiway beside the runway, causing the wingtip to erode until the left wing surge tank began leaking fuel as they continued to slide. The aircraft finally stopped, and a fuel fire caught up to the aircraft and started burning.
The Whiteman fire department arrived on scene and began fighting the fire. They correctly identified it as a fuel fire, originating at the left wing. However, the incident commander ordered the firefighters to begin fighting the fire with water, instead of AFFF, as he believed that Air Force Instructions required the use of AFFF as a last resort when fighting fires.
Approximately three and a half minutes after they began fighting the fire, the incident commander ordered the use of AFFF, which allowed them to knock the fire down enough to begin to approach the wing to fight the internal fire. As they prepared to start spraying the wing, the surge tank exploded, forcing them back. They were able to knock that fire down, and were approaching the wing again, when the left outboard fuel tank exploded, sending an approximately six foot section of skin into the air, landing near the firefighters.
![[Image: B-2%202022.jpg]](https://denyignorance.com/uploader/images/B-2%202022.jpg)
The crew was able to shut the engines down, and attempted to egress through the crew entry door. They were able to open the hatch, but weren't able to extend the ladder due to the aircraft sitting on the left main door.
![[Image: B-2%20Left%20Main%20Door.jpg]](https://denyignorance.com/uploader/images/B-2%20Left%20Main%20Door.jpg)
They were able to squeeze out the opening and safely egress the aircraft, and were met by medical personnel.
The investigation found that upon landing, the TPA compresses 1-2 inches, which causes fluid to circulate internally. The fluid is forced out due to different sizes of the actuator. During the compression, a transient hydraulic pulse is created that cycles through the return circuit, and the destow hydraulic line, through the MLG sequence valves, to the Switching Valve, and into the reservoir. It also cycles to the Lock Actuator, causing a slight constriction of the lock springs, which allows the Lock Link Assembly to rotate out of the overcenter position and unlock. This is what caused the failure of the landing gear as soon as the aircraft touched down. The aircraft was deemed a total loss, as repairs were estimated at $300M for the airframe, and another $27,500 in damages to the airfield.
They were cleared for a standard ILS approach, and at about 200 knots the Pilot Monitoring, who was a B-2 Instructor Pilot, lowered the landing gear. The Left Main, and nose gear deployed normally and showed locked, but the Right Main failed to extend. The crew received a primary and secondary hydraulic system caution indicating a hydraulic leak. The B-2 hydraulic system has several parts, including monitoring system, pumps, reservoir, accumulators, and high pressure subsystems. The primary and back up systems normally don't exchange fluid, but when switching between systems some fluid may be exchanged between the two systems.
The plumbing of the hydraulic systems uses titanium tubing, and CryoFit fittings are used to join two lines together. A CryoFit coupling is a sleeve that goes over both lines, with internal knurling to add tensile strength to the joint. When the CryoFit coupling is prepared to be used, it's dipped in liquid nitrogen, and a tapered mandrel is pulled through the coupling expanding its size.
The two lines are passed into the coupling, and it's allowed to return to room temperature. As it returns to room temperature, the coupling shrinks back to its normal size, and the knurling bites into the lines, creating a fluid tight seal, and creating a "pooch", which resists tension pull out loads.
The B-2 main landing gear consists of the Truck Beam, Shock Strut, Upper and Lower Drag Braces, and the Lock Link Assembly, which consists of the Upper and Lower Lock Links, Lock Link Springs, the MLG Lock Actuator, and Truck Position Actuator. The gear is extended via the landing gear handle, or the Landing Gear Emergency Lowering Switch. The FCCs, PSLUs, and proximity sensors handle the retraction and extension, and are hydraulically actuated.
The PSLUs issue driver commands to both the Left and Right Main Landing Gear, which have separate drivers independent of each other. Once the gear are down, the MLG Lock Link Assembly rotates to the overcentered position, locking the landing gear in place, and the truck beam rotates the wheels to the toe-down configuration for landing.
During emergency extension, accumulated pressure is used to lower the landing gear, the Lock Link is rotated to overcentered, as normal, but the link is held in place by two springs, that apply about 100 pounds each of force on the Lock Link Assembly. On the Mishap Flight, when the landing gear handle was lowered, the hydraulic system pressurized, and all three landing gear doors unlocked and began to cycle, but the Right Main Landing Gear (RMLG) CryoFit coupler failed, separating the two lines and allowing hydraulic fluid to leak, and pressures to drop low enough to trigger the warnings in the cockpit.
The leak prevented hydraulic fluid from reaching the RMLG sequence valve, keeping the RMLG locked. The door cycled open and closed repeatedly as the system switched between primary and back up systems. The FCCs switched six times, attempting to unlock the right mains, but failed due to lack of hydraulic fluid. The crew almost immediately performed an emergency gear extension, and were able to get three green in the cockpit showing all three landing gear were down and locked.
The crew landed approximately 1,000 feet down the runway at Whiteman, and the left main failed almost immediately. The aircraft dropped onto the landing gear door, and the landing gear folded into the wheel well. The aircraft began sliding down the runway, with the left wingtip dragging along the runway, and eventually the grass beside the runway. At approximately 8700 feet down the runway, the left wing dragged across a taxiway beside the runway, causing the wingtip to erode until the left wing surge tank began leaking fuel as they continued to slide. The aircraft finally stopped, and a fuel fire caught up to the aircraft and started burning.
The Whiteman fire department arrived on scene and began fighting the fire. They correctly identified it as a fuel fire, originating at the left wing. However, the incident commander ordered the firefighters to begin fighting the fire with water, instead of AFFF, as he believed that Air Force Instructions required the use of AFFF as a last resort when fighting fires.
Approximately three and a half minutes after they began fighting the fire, the incident commander ordered the use of AFFF, which allowed them to knock the fire down enough to begin to approach the wing to fight the internal fire. As they prepared to start spraying the wing, the surge tank exploded, forcing them back. They were able to knock that fire down, and were approaching the wing again, when the left outboard fuel tank exploded, sending an approximately six foot section of skin into the air, landing near the firefighters.
The crew was able to shut the engines down, and attempted to egress through the crew entry door. They were able to open the hatch, but weren't able to extend the ladder due to the aircraft sitting on the left main door.
They were able to squeeze out the opening and safely egress the aircraft, and were met by medical personnel.
The investigation found that upon landing, the TPA compresses 1-2 inches, which causes fluid to circulate internally. The fluid is forced out due to different sizes of the actuator. During the compression, a transient hydraulic pulse is created that cycles through the return circuit, and the destow hydraulic line, through the MLG sequence valves, to the Switching Valve, and into the reservoir. It also cycles to the Lock Actuator, causing a slight constriction of the lock springs, which allows the Lock Link Assembly to rotate out of the overcenter position and unlock. This is what caused the failure of the landing gear as soon as the aircraft touched down. The aircraft was deemed a total loss, as repairs were estimated at $300M for the airframe, and another $27,500 in damages to the airfield.
