适用于安装Collins MCP板的737NG飞机:
飞机在地面切换电源时,出现模式控制面板(MCP)显示窗口黑屏无显示,按钮信号灯不亮,但所有的开关和旋钮功能都是正常的。复位跳开关或整机断电后,恢复正常。
事件背景
某737-800飞机,上客后机组反映MCP板显示窗口黑屏无显示,按钮信号灯不亮,但所有的开关和旋钮功能都是正常的:
整机断电后恢复正常,后续航段使用正常。
问题分析
Collins Mode Control Panel (MCP-730) Display Blanking and Inoperative Push Button Annunciator Lighting During Airplane Power Transfers
厂家对此进行研究后发现:
The condition is the result of the MCP internal power supply going into an under voltage/over current condition and is caused by abnormal airplane power transfers. More specifically, when an airplane power transfer event occurs on-ground, airplane power transients may occur. These transients momentarily cause a decrease in 28V DC power applied to the MCP, which may cause the MCP internal power supply circuitry to draw excessive current, tripping the MCP over-current circuitry hardware monitors and resulting in blank display windows and/ or inoperative push button annunciator lights.
Should this condition occur, the MCP can likely be recovered when a power cycle is performed through the AFCS MCP DC 1 (C1044) and AFCS MCP DC 2 (C1047) circuit breakers.
故障发生原因是由于飞机非正常电源转换导致MCP内部电源出现了欠压/过流。更具体的说,当飞机在地面切换电源时,飞机电源瞬时功率可能会发生变化。
这些瞬时变化导致提供给MCP的28V直流电源减少,这可能导致MCP内部电源电路电流消耗过大,使MCP过流电路硬件监视器跳开,并导致显示窗口空白和/或按钮信号灯不工作。
如果出现这种情况,通过AFCS MCP DC 1(C1044)和AFCS MCP DC 2(C1047)跳开关,执行电源循环后,MCP可能会恢复正常工作。
厂家推出了Collins SB MCP-730-22-6 Rev. 1 ,进行MCP内部硬件修改,以帮助减少这种情况的发生。受影响的MCP件序号:
航线上如果碰到MCP窗口指示黑屏,且符合这些条件时:
4、MCP所有旋钮和开关工作正常(在PFD和ND上确认)
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