The FAA is adopting an airworthiness directive (AD) for certain Learjet 60s. The AD was prompted by a report of a high-speed rejected takeoff caused by all four main landing gear (MLG) tires blowing out during the takeoff roll.

This AD requires extensive parts replacement, including installing new rigid hydraulic tube assemblies to the MLG struts; installing a new MLG squat switch bracket; modifying the MLG squat switch wire harness; modifying the MLG anti-skid wheel transducer electrical wire harnesses; and routing and securing the anti-skid wheel and squat switch electrical wire harnesses to the MLG strut assembly.

According to the AD, the purpose is to prevent failure of the braking system or adverse operation of the spoiler and thrust reverser system due to external damage, particularly from tire failure, which could result in loss of control of the airplane.

The FAA estimates the cost of compliance for each of the 275 U.S.-registered aircraft it affects could run as high as $38,000. Some of the costs may be covered under warranty. The AD is effective August 6.