By Marina Malenic
Northrop Grumman [NOC] said yesterday that it is working with the Air Force to resolve, “once and for all,” a technical issue that has been plaguing the B-2 Spirit stealth bomber fleet for more than 20 years–cracking in the aircraft’s aft deck, a metallic panel on the upper surface that shields its composite airframe from the heat of engine exhaust.
Engineers from the government and the company just completed a paper “fly-off” between two alternate approaches for redesigning the aft deck, according to a company statement. They hope to produce a new aft deck that can span normal maintenance cycles without needing intermediate repairs.
Located behind the aircraft’s exhaust outlets, the aft deck is exposed to extreme temperatures and acoustic-induced vibrations, making it vulnerable to fatigue and cracking.
“The key to producing a reliable, high performance aft deck is creating a balance between stiffness and flexibility,” said Chuck Osberg, Northrop Grumman’s aft deck program manager. “If the deck is too flexible, high cycle fatigue will cause premature failure; if it’s too stiff, it can put undue stress on adjacent structures.”
According to Osberg, the winning aft deck design was selected on the basis of cost and performance. It reflects many years of thermal and structural analysis of the component. It also includes new stiffening elements designed to significantly reduce the vibration and metal fatigue.
The aft deck upgrade program is the latest in a series of modernizations that the Air Force has made to ensure that the B-2 remains flight worthy for decades to come.
Last year, the Air Force implemented an interim solution to the cracking in both the aft deck and behind the exhaust nozzles on the upper surface of the aircraft. Officials are concerned that the tiny cracks will affect the B-2’s low observable signature.