They kept the same function until the MAX.Īfter 20 years Boeing added a second memory item: “If runaway trim continues: Stabilizer Trim Wheel _ Grasp and hold” and some helpful notes.Ībove: Classic stab trim cut-out switchesīy the year 2000, the procedure had expanded to 4 memory items: One Non-memory item: “Stabilizer _ Trim manually”Īnd one note: Move control column smoothly as required to maintain desired airplane attitude.Ībove left: QRH from 1975 Above right Stab trim cutout switches in a 737-200. One memory item: “Stab Trim Cutout Switches_CUTOUT” The whole procedure is just 3 lines long!
#Airspeed switchies manual
Manual stabilizer trim should then be used for the remainder of the flight." The evolution of the QRH Procedure 1967-1987 If uncommanded stabilizer trim movement continues, place both STAB TRIM cutout switches to the CUTOUT position. It is important to note that even though the steps in the Runaway Stabilizer checklist are sequential, these steps can be accomplished simultaneously. Sustained use of main electric stabilizer trim may be needed. Use main electric stabilizer trim to reverse any stabilizer trim movement and to reduce control column forces. If uncommanded trim motion continues, it may stop when the control column is displaced in the opposite direction and the control column cutout is activated.
After the autopilot and autothrottle are disengaged, use the control column and thrust levers to establish appropriate pitch attitude and airspeed. The control column must be held firmly before the autopilot (if engaged) is disengaged to maintain airplane pitch control and retain any elevator commands from the autopilot. "During a runaway stabilizer condition the crew should maintain airplane pitch control through the use of the control column, main electric stabilizer trim, and thrust levers.
For example, some stabilizer trim movement can be expected to occur during speed, altitude, or configuration changes." Since commanded stabilizer trim can occur automatically, the pilot needs to consider the existing flight conditions to determine if a runaway stabilizer condition exists. During manual flight or flight with the autopilot engaged, automatic stabilizer trim can be commanded by the Speed Trim System or autopilot trim. "A runaway stabilizer condition can be recognized by continuous uncommanded movement of stabilizer trim, or if stabilizer trim is occurring in a manner that is not appropriate for current flight conditions. The FCTM has been updated since the MAX return to service review in 2020 as follows: You can also learn more about DAZIC Zero Speed Switches by checking out our case studies.The three marks on the fuselage indicate the upper, neutral and lower limit of travel of the horizontal stabilizer. Once submitted, one of our Sales Engineers will contact you with their recommendations. To know more about DAZIC Zero Speed Switches and which ones will fit your company’s needs all you need to do is to fill out our Application Data Sheet. The DAZIC zero speed switch models differ in terms of: Choose the best zero speed switch for your process and factory conditions If the switch detects that the RPM does not match the speed trip-points you’ve set, a corresponding relay de-energizes and triggers an alarm. This simple set-up helps detect any speed changes. These pulses are proportional to the shaft’s rotations per minute. These shafts are found in many types of material handling systems including plant machinery, from conveyor belts to rock crushers.ĭAZIC Zero Speed Switches contain small metal flags or magnets mounted on a disc or pulsar wrap, which generates pulses as it passes through the probe’s electromagnetic field.
Speed switches are attached to rotating shafts to detect any abnormal change in rotation speed.
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