79-26-02 BOEING: Amendment 39-3638. Applies to all Model 737-200 (advanced) airplanes with GPWS flap position switches sensing less than 30 degrees as landing flaps, certificated in all categories. Compliance required as indicated. Accomplish the following: \n\tWithin the next 1,200 hours time-in-service or six (6) months, whichever comes first, after the effective date of this AD, change the ground proximity warning system flap position switch to sense flaps 30 degrees and 40 degrees as the landing flap positions, and provide a flap override switch for landings that must proceed with flap position of 25 degrees or less. This modification may be accomplished in accordance with modifications approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region, 9010 East Marginal Way South, Seattle, Washington 98108. \n\n\tThis amendment becomes effective December 31, 1979.