737NG电瓶放电灯闪亮

老兵新传 · 发表于 2016-3-30 16:12:31

一）电瓶放电灯闪亮的故障现象：
2016-3-24，一架737NG飞机在文山机组反映BAT discharge灯闪亮。飞机回基地后，测试现象如下：断开交流，主电瓶、辅助电瓶的电压正常，电流值时而显示放电负值，时而显示充电正值，在-900到+900间跳动，主/辅助电瓶放电灯有时会闪亮。查询该机的P5-13电源指示面板（PN:285A1840-8,SN:F04401)的故障历史，发现此P5-13电源指示面板在其他飞机也同样反映过此故障。判断为P5-13电源指示面板故障导致电瓶释放灯和显示值异常，更换后正常。

二）电瓶放电灯及指示电路工作情况及分析（如图所示）：
NG电瓶放电灯及指示电路是通过检测直流电流通过电瓶负极电阻时，在其两端所产生的电压大小和方向来显示的。因电瓶负极电阻很小，因而所产生的电压模拟信号也很小，还需放大电路将信号放大，再通过A/D转换电路将其转化为数字信号。当电瓶放电电流大于5安培，超过95秒或放电电流大于15安培，超过25秒或放电电流大于100安培，超过1.2秒，会点亮主电瓶/辅助电瓶放电灯，此时显示屏指示为负值。
该故障为P5-13电源指示面板内指示放大器电路损坏而变成谐振故障，导致电瓶释放灯时而亮时而灭，主、辅电瓶电流值在-900到+900之间跳动

三）波音相关P5-13板内部指示电路的改良737-SL-24-210
BACKGROUND:
The P5-13 Electrical Meter, Battery  and Galley Power Panel located in the P5 overhead panel includes the Cirrus CS5012A-BL7Z A/D Converter  which  is  becoming  obsolete. This A/D converter is located on the 285A1848-4 Processor card assembly located inside the P5-13 panel.  The replacement device for the Cirrus A/D is the Analog Device AD7610.  This is not a pin for pin compatible device.  The new A/D also needs different voltage inputs causing the requirement for other devices to be incorporated into the PCB.  The array of devices (19 components and 4
power traces) that need to be added include flip flops, IC gates, capacitors, and resistors.  Due to the smaller size of the new A/D and the need for placement of the added devices, the entire PC
BOEING ACTION:
The availability of the new P5-13 incorporating the new A/D converter  was implemented  by Boeing starting on Line Number 5021 for Single Battery Panel and Line Number 5022 for Dual Battery Panel beginning in 7 July 2014.
SUPPLIER ACTION:
Publish BAE Service Bulletin 285A1840-24-03 for modification of P/N 285A1840-7, -7 MOD A and 285A1840-8, -8 MOD A P5-13 Panel Assembly.