Brian Kilburn of the Boeing B-2 System Program Office presented insights into the true cost of a stealth operation at the Stealth Conference conducted recently in London by military/defense conference organizer Defence IQ. Kilburn noted that the 20-strong fleet of B-2s requires 70,000 maintenance hours annually, and that 40 low-observable (LO) technicians work on them full-time. The U.S. Air Force currently spends $17 million per year on repair materials for the aircraft’s radar absorbent material.

Although the flying-wing shape of the B-2 is inherently stealthy, imperfections in the aircraft’s skin can significantly increase its radar cross section, Kilburn said. Surfaces are heavily coated with radar absorbent material, sometimes six layers deep. All gaps must be sealed, including access panels every time they are opened, he said, but they tend to open up again because of aerodynamic stress and fluid spillage.

After each repair, the area’s radar cross section must be checked by probe or zonal measurement, Kilburn reported. Therefore, about half of the 48 maintenance man-hours per B-2 flying hour are related to the aircraft’s LO features.

Some of the coatings take 13 hours to dry, and some must be mixed very accurately, he said. Some must be stored at minus 40 degrees C. Some have a shelf life of only six months. These strict requirements have limited the ability to deploy the B-2 away from its home at Whiteman Air Force Base in Missouri, he said.

Kilburn said that the company began to make serious efforts to reduce LO support costs in 1999. It has made significant improvements in the last four years, as better materials have been developed, including spray-on coatings that take only 30 minutes to cure.

Some parts of the aircraft, such as the tail pipe arrowhead panel, have been redesigned to reduce gaps, Kilburn said. The company also has made advances in “RF diagnostics” which allow a greater understanding of the aircraft’s component-level signature on the ground.

Most of the improvements are being introduced as each B-2 goes in for depot-level maintenance. Since this is a 14-month process, it will take seven years to retrofit the entire fleet, Kilburn said. However, the end result will apparently be an even stealthier Stealth Bomber.