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SR 3-5400024037

2022年8月，55*8飞机机组反映再现时马赫配平失效灯亮。DFCS核实为B通道有22-11212 故障信息，判断为B通道马赫配平系统故障，因停场时间不足且无运力调整，依据MEL保留B通道马赫配平系统和自动着陆系统，完成M项，办理SG DD保留。后此次起飞时收襟翼加速过程中 （大约是5度往0度收），VNAV方式下，目标空速应该为230，但是在收的过程中就直接到了250。CDU便签栏显示BUFFET ALERT信息。后DFCS测试，A通道自检通过，B通道有22-11212 FLAP POS INV信息，可疑部件为FLAP POSN-2。执行库测试60.33,A,B通道都通过。执行60.34库测试，60.34页面显示有22-11212 FLAP POS INV信息，可疑部件为FLAP POSN-2。执行襟翼校装测试，A通道在范围中，B通道均不在范围内。量线D229 PIN9和PIN10为断路状态，判断T428襟翼传感器故障。北京航后量线检查T428襟翼传感器故障，更换T428襟翼传感器。完成 BITE Library Test库测试60.33和60.34，测试正常。完成襟翼校准装测试，结果符合要求。依据FIM量线，检查正常。检查相关插头无腐蚀、脏污、损坏及内部销钉损伤等不正常现象。马赫配平系统B通道不工作故障也一并消失。就此与波音做了沟通。

Q1: Which computer provides the function to produce BUFFET ALERT” message. DEU or FMC ? Whether the flap system will affect its function. How does it affect ?
R1: The BUFFET ALERT message is displayed by the FMC when the current aircraft condition has a buffet margin less than that selected on PERF FACTORS page.
The following provides the logic for FMC display of the Buffet Alert message:
(Current speed is greater than high speed buffet with a pad or current speed is lower than low speed buffet with a pad or the current altitude is greater than the buffet limited max altitude with a pad) and (Airplane is in Air and G/S is greater the 60 knots and Flaps are up).
Therefore the message is inhibited when flaps are down and the message does annunciate both high and low speed buffet conditions when flaps are up.
The FMC Buffet limit is only for Flaps up.  Below approximately 20,000, feet FMC flaps up buffet limits begin to be washed out so as not to conflict with the SMYD provided limits at lower altitudes.
High speed buffet is displayed as noted in the logic and is based upon the current speed approaching the high speed buffet limit.

Q2: Which system is the target airspeed derived from? FCC or FMC?
R2: With VNAV mode engaged the target airspeed is calculated by the FMC. The FMC performance management function uses airplane and engine models and optimization algorithms to provide flight regime control of the airplane through speed and thrust consistent with the performance mode selected or with constraints imposed by Air Traffic Control. Inputs to the performance management function include total fuel, mode selections and engine bleed information, altitude, airspeed, Mach and temperature, progress along the flight plan and pilot inputs from the CDU. The outputs are advisory data to the crew and target values of Mach, CAS and target thrust settings for optimum control of the airplane.

Q3: Is the fault Flaps are up signal from which component?
R3: Flap position signals are provided to the FMC from the DFCS.

SR 3-5395669548

2022年8月，机队出现收放襟缝翼时后缘襟翼PDU有异响，襟翼收和放的刚开始声音特别大。如下附件所示。使用备用方式和正常方式收放均有异响，检查PDU油液面与勤务口平齐 满足手册要求。参考Trailing Edge Flap Torque Tube and Torque Tube Support Lubrication, TASK 12-22-51-640-801.完成润滑，故障依旧。

与波音做了沟通，波音表示此类异常噪音在未明确前不得放行。并给出如下建议方案：

• verify the adjustment of the flap PDU and the flap control unit per AMM TASK 27-51-00-820-801, step I.(5) and step I. (6) respectively;
• check the adjustment of the trailing edge control valve per AMM TASK 27-51-00-820-801, step I.(16);
• check if the bypass valve (AMM 27-51-02) causes the noise.
• perform AMM TASK 27-51-65-360-801 “Trailing Edge Flap Control Valve Internal Leakage Repair”.

打压状态下检查发现发现与FCV相连的两个液压管子，分别在放襟翼和收襟翼时发生强烈振动，且液压管路有发热现象。最终经过多个液压部件的隔离，最终确认是优先活门渗漏导致。

SR 3-5396507207

2022年8月，机队运行中连续两架飞机反应在尾撬余水口发现螺钉。

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打开狗洞和尾撬的盖板，并未发现丢失，且该规范号并为在该区域找到适用。

波音表示非常少用到，可能与结构修理相关。

The screw found in B-17X5 looks similar to BACS12CK type screw.  This screw has few installations in section 48.  Boeing notes that BACS12CK screws are installed at the STA 1016 cable seal installation.  See AIPC 27-41-00-11.

The bolt found on B-57X5 looks to be a typical structural permanent fastener, but the head marking does not reveal any possible source.

Boeing appreciates HNA completed inspection of tail skid zone and tail compartment.  Boeing recommends reviewing recent maintenance or repairs in section 48 that would include part and fastener removals.  Boeing recommends another inspection verification of systems installations for missing screws and structure installations, including brackets, for missing permanent fasteners.