(See also B737 Technical Site)

TYPE : 300

NUMBER / ORIGIN / DATE : 001 / E-mail / 200594


Normal take off with acceleration altitude 1200ft QNH. At about 950ft both thrust levers started reducing and were manually overridden after about 30 degrees of travel and returned to TO thrust posn. No failures, or warnings given during event. Aircraft normal for rest of sectors.

TYPE : 400

NUMBER / ORIGIN / DATE : 002 / E-mail / 020296


Both EFIS screens can occasionally go blank without any pilot input for several seconds before returning. This event is sometimes associated with an amber "Flight Controls" warning. The longest time seemed about 10 seconds (we were both checking CBs when it returned). No fault found on ground.

TYPE : 300/400/500

NUMBER / ORIGIN / DATE : 003 / E-mail / 261196


Recent tests of the main rudder power control unit, conducted at Boeing, demonstrated a potential failure scenario that was previously unknown. The tests revealed that rudder pedal input can cause deformation in the linkage leading to the primary and secondary slides of the servo valve of the main rudder PCU. This is possible if the secondary slide gets jammed for whatever reason, possibly resulting in the rudder moving in the opposite direction of the rudder command. The intent of the original design of the dual servo system, in compliance with certification requirements, is to have the effect of a jam of either the primary or the secondary slide neutralized by the opposite slide. Testing has now revealed that if the secondary slide of the servo valve jams and the primary slide does not neutralize the effects of the jam, the result may even have the opposite effect - the rudder moves in the opposite direction of the command.

Interim actions
On 2 November instructions were issued in response to these findings, ordering a test of the system. This test required to first fully push the left rudder pedal to the stop followed by the right pedal as fast as possible, with the same procedure repeated on the right hand pedal. Under normal circumstances the fast pedal movement will cause an increase in rudder pedal force compared to slow pedal movement, while the rudder will continue to travel until the forward stop is reached. An unusual result of the test would be a continuous pedal and rudder movement in the opposite direction of the applied force, requiring immediate replacement of the PCU. This test, that must for the time being be repeated every 250 hours, is regarded by Boeing to be an interim solution. At this time a design change is being developed, eliminating the need for the repetitive test requirements

TYPE : 300/400/500

NUMBER / ORIGIN / DATE : 004 / E-mail / 250697


(also Letters 15 -Ed)
In my experience the first sign of EMI aboard a B737 is a Symbol Generator failure of either pilots' EFI. Fortunately I haven't had BOTH go tits up at the same time. In the 3 SG failures I've had in flight (usually at night while up to my armpits in thunderies), its because some clod has been listening to a CD player. After swapping over to the useable SG,ding for the girls and ask them to look for who's operating an electronic device. Follow this up with a rather aggressive PA after they get back to you. This will hopefully stop other undetected devices.Should the SG failure be of EMI cause, you can bet you'll get your SG back after you reverse the drill. On the last SG failure I had, 3 Hong Kongers were yacking on their 'ha-rrones', another was trying to connect his laptop to the internet using a radio-modem, and 2 others were hoppin' and boppin' to a CD of Jackie Chan songs! I suppose even a SG gives up when it hears Jackie Chan singing!

TYPE : ?

NUMBER / ORIGIN / DATE : 005 / E-mail / 050897


We have had 3 cases this year of a red main gear unsafe light remaining on after takeoff on various aircraft in our fleet (5). It has on all occasions been a faulty uplock detector. Our engineers feel this item is not very reliable. The gear system functions normally, you just get a fright

TYPE : All

NUMBER / ORIGIN / DATE : 006 / E-mail / 280698


B737 AD 98-11-52

Jump Back To Main Menu