The UK Air Accidents Investigation Branch (AAIB) has issued four safety recommendations in response to an incident in which a burst tire on a Bombardier Global Express caused “extensive damage” to the flight control system. The recommendations urge the manufacturer to provide more protection for flight-critical systems near the main landing-gear tires and to make modifications to reduce the amount of water pouring onto tires and brakes when the aircraft is parked in heavy rain.
The jet landed at London Luton Airport on Jan. 29, 2008, after a flight from Van Nuys, Calif., where it had stood in heavy rain for a prolonged period before departure (although the weather was actually dry at the time of takeoff). During the landing roll, the left inboard main landing-gear tire burst after a wheel locked as a result of ice formation on the brake surfaces. Flying tire debris caused the flap drive shaft and two hydraulic lines to fracture and damaged a wiring loom and a section of the wing. No one on board was injured.
AAIB investigators are concerned that the damage to the flight control systems could have yielded much more serious problems if the incident had occurred on a touch and go.
The agency recommended that the FAA, the European Aviation Safety Agency and Transport Canada raise awareness of the vulnerability of carbon brakes to freezing in flight following exposure to moisture on the ground, emphasizing the significance of the slow drying rate of saturated brakes even in warm, low-humidity conditions; and review the certification requirements for automatically stopping flight recorders within 10 seconds of a crash impact.
Bombardier is implementing two modifications for its in-service Globals. The first is the introduction of a new drain plug above the landing gear to redirect water away from the wheels and brakes. The second involves the relocation of two hydraulic lines on the wing trailing edge to prevent damage in the event of a tireburst.
The company has taken four measures to address potential problems for in-service Globals. It immediately issued an advisory wire to all operators reminding them of the potential for carbon brakes to absorb water that can then freeze. It modified the operating manual to provide precautionary information on how to prevent brakes from freezing. Finally, it was set to issue two service bulletins before the end of last month to cover the installation of the same two modifications that are now being made to aircraft in production.