Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This proposed AD was prompted by reports of flight crew failure to activate air data probe heat. This proposed AD would require modifying the anti-icing system for the angle of attack sensor, the total air temperature, and the pitot probes. We are proposing this AD to prevent ice from forming on air data system sensors and consequent loss of or misleading airspeed indication on all airspeed indicating systems, which could lead to loss of control of the airplane.