[24电源] WHAT，IDG滑油渗漏超标还可以这么操作？

摘要：737NG飞机IDG滑油渗漏放行要求比较严，一旦出现渗漏很容易造成航班延误。经咨询波音IDG渗漏可以脱开保留。

IDG滑油系统和发动机滑油系统互相独立，渗漏放行标准不同。IDG输入轴或者IDG冷却系统滑油渗漏标准在AMM 71-71-00-790-008-F00；发动机滑油渗漏标准在AMM71-71-00-010-002-F00。

IDG冷却系统渗漏比较直观，通过外部能检查出来。IDG输入轴渗漏不易判断，IDG结合面余油口有油液渗漏，可能是IDG输入轴渗漏，也可能是AGB上的碳封严渗漏。

判断IDG输入轴渗漏还是AGB封严渗漏，可以按AMM24-11-00-700-801 IDG Oil System Static Leak Check检查。检查需要专用设备，步骤比较简单，往IDG输入一定的气压，监控气压是否连续下降，如果下降说明IDG渗漏。如果IDG没有渗漏，说明AGB封严渗漏。

根据渗漏部件和渗漏量判断是否超标。对于AGB渗漏，维护标准（Threshold limit）: 7 cc/hr (2 滴每分钟），放行标准（Serviceable limit）: 20 cc/hr (7 滴每分钟）。对于IDG滑油渗漏，放行标准: 1 cc/hr（约0.3滴每分钟）。

渗漏量低于维护标准不需要工作；渗漏量大于维护标准，小于放行标准的，找合适停场时间更换渗漏部件；渗漏量超出放行标准的，飞机不能放行，必须换件。

对于IDG滑油渗漏，只有放行标准，而且要求比较严格，我们可以理解为日常维护不允许有渗漏。

如果IDG滑油系统管路、IDG滑油系统子部件（如空气滑油热交换器）、IDG余油口渗漏超标，在航材缺件的情况下，可以脱开IDG按照AMM 71-00-00-700-823-F00 Test3B-Part Power Leak Check试车,试车后无渗漏或者渗漏值在手册标准内，可以按照MEL24-01-02，脱开IDG保留放行飞机。

通常脱开IDG后，由于滑油泵不工作，IDG的滑油量高度低于输入轴，不再有滑油从输入轴渗漏，所以不需要排空滑油。

如果IDG其他子部件渗漏，比如滑油空气交换器渗漏，可以排空IDG滑油,再按MEL24-01-02保留放行。

GUN-GUN-16-0134-02B

SUBJECT: B737NG-71 - Oil Leakage from IDG pad drain dispatch

DESCRIPTION:

China Southern Guilin branch encountered oil leakage from IDG pad drain, the oil leakage might from IDG input shaft seal or AGB pad seal PER REF/A/.

If the leakage is beyond AMM limit, GUN is kind asking Boeing if they can dispatch the AC under the below condition:

1, Disconnect IDG,

2, Ground engine run to check if there is oil leakage from IDG pad drain (GUN believes there should be no oil leakage from IDG pad drain with IDG disconnected if the leakage is from IDG input shaft seal)

3, Dispatch AC per MEL REF/B/ if no oil leakage observed or oil leakage is within AMM limit during engine ground run.

4, Replace the seal within interval as CAT B mentioned in REF/B/.

RESPONSE AND/OR REQUIRED ACTION :

Boeing please advise if the above GUN proposal to dispatch AC under REF/B/ MEL is acceptable, if not, please advise the reason.

RESPONSE:

China Southern's proposed procedure is acceptable. It is acceptable for China Southern to disconnect the IDG and verify no leakage or leakage within AMM limits during the engine ground run. By disconnecting the IDG, the charge/scavenger pump would not operate and the oil level will settle below the input shaft seal level and oil leakage would not be expected with the IDG disconnected.

However, in any case Boeing would not provide approval for dispatch with leakage beyond AMM limits.

GUN-GUN-16-0134-04B

SUBJECT: B737NG-71 - Oil Leakage from IDG pad drain dispatch

DESCRIPTION:

In Ref /A/, China Southern Airlines asked the following questions related to the 737CL/NG DDG/MMEL Item MEL 24-01-02 "Engine Driven Generator Systems -600/-700/-800/-900/-900ER":

China Southern would like to further clarify with Boeing on the Ref /B/ MEL application. Therefore, they raise up the following scenario along with question:

If the leakage was identified at the internal tubing or sub-component within IDG (say, the internal leakage on the IDG Air/Oil Exchanger), without any impact on the engine oil quantity, whether China Southern can apply the Ref /B/ MEL to disconnect the IDG for dispatch relief? 

Note: China Southern may run up the engine at idle power to ensure the IDG disconnection will not impact on the engine oil quantity.

RESPONSE:

As described in the Ref /C/ AMM Systems Description, the IDG has its self-contained dedicated oil system that is independent from the engine oil system.  Therefore, for the condition described by China Southern Airlines, i.e. oil leakage identified at the internal tubing or sub-component within IDG, the Ref /B/ MMEL dispatch is applicable, provided all MMEL provisos are complied with.    

The IDG sustaining oil leakage (including complete oil loss) can be disconnected per AMM 24-00-00-040-801 without prior oil servicing to the unit, because during IDG disconnect procedure engine is at the idle speed or close to the idle speed, and IDG is not under demanding load, and the disconnect procedure takes only few seconds.

When airplane is dispatched in accordance with Ref /B/ DDG/MMEL due to IDG oil leakage, it is not necessary to drain IDG, however operator should ensure that, after IDG is disconnected, oil leakage rate is within AMM 71-71-00-200-801-F00 limit. By disconnecting the IDG, the charge/scavenger pump would not operate and the oil level will settle below the input shaft seal level and oil leakage would not be expected with the IDG disconnected.

IDG can be operated without oil for up to 50 hours in the disconnected mode. It is acceptable to fully drain the leaking IDG, when Ref /B/ DDG MMEL is applied, provided that the airplane operates in this condition for no more than 50 hours.  When IDG is operated without oil, special care should be taken to ensure that the IDG is NOT reconnected on the ground, and that the flight crew disconnects the drive prior to every flight.

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