BBJ/737 speedbrake emergency AD issued

Boeing Business Jets are included in an emergency AD issued last month that prohibits using the speedbrakes on 737-600s and -700s at airspeeds in excess of 300 kias. The FAA said it issued the directive (AD 2002-08-52) after receiving a report that on April 5, a 737-700 with its speedbrakes deployed at 19,500 ft msl and 315 kias experienced “a severe high-frequency vibration” of the horizontal stabilizer. The speedbrakes were then retracted, but the vibration continued until the airspeed was reduced to 285 kias. The FAA and Boeing have determined that the vibration was due to a “limit-cycle oscillation” of the elevator and elevator tab assembly. Component modifications are being developed.