現(xiàn)象及歷史

　　近期737NG飛機多次反映發(fā)動機關車后，在尾噴管內(nèi)部下方聚集一灘滑油，尤其短尾噴構型的飛機，會從TRF（后渦輪框架）的6點鐘位置余油口不斷往外滴油，處理導致航班延誤。

原理分析

　　CFM56-7B發(fā)動機滑油系統(tǒng)有前后兩個集油槽（見圖一），前集油槽位于風扇框架的腔體內(nèi)，后集油槽位于后渦輪框架腔體內(nèi)。前后集油槽都是通過蓖齒氣動封嚴（見圖二）保證滑油不外漏。而蓖齒氣動封嚴原理是發(fā)動機引氣壓力大于滑油壓力從而保證滑油在油路內(nèi)部流通不外漏；當發(fā)動機引氣壓力不足時（關車時），油壓大于氣壓，蓖齒氣動封嚴失效，滑油將會從封嚴的排放口流入后渦輪框架腔體內(nèi)，并通過后渦輪框架與尾噴的法蘭盤縫隙中流出，會在尾噴處留下一灘滑油（新短尾噴構型在后渦輪框架6點鐘位置加裝了一個排放口，余油也會從此排出，見圖三）。

　　新舊尾噴構型在關車后都會從尾噴處漏滑油，此為正?，F(xiàn)象，只是新短尾噴構型讓余油更容易被看見（見圖四）。

　　具體余油軌跡請見圖五，其滑油分油機分油溫度多少最好他詳細描述見附件737NG-FTD-79-14001。

排故提示

　　1、如過站機組反映尾噴內(nèi)漏滑油，現(xiàn)場確認漏油情況，如符合以上描述，計算滑油消耗率，如在以下標準范圍內(nèi)，無需處理，與機組做好原理解釋。

　　參考AMM71-00-00-800-806-F00 ENGINE OPERATION LIMITS滑油分油機分油溫度多少最好：

　　1） 正?；拖穆实陀?.4US quart/hour或者0.1US gallon/hour(0.38 liters/hour)；（機務有滑耗監(jiān)控機制，如高于0.4，會有相應的分析核實或進一步的排故檢查糾正措施）

　　2） 出現(xiàn)以下情況之一時，必須參考FIM找出原因（監(jiān)控分析核實，主要航后排故使用，不是放行標準）。

　　a. 滑油消耗率平穩(wěn)增加

　　b. 滑油消耗率徒增

　　c. 滑油消耗率大于0.8US quart/hour或者大于0.2US gallon/hour(0.76 liters/hour)

　　3） 圖表：最大允許滑油消耗率（放行標準，第2段落答本的依據(jù)）：

　　Model 737-

　　Winglet installed

　　Oil consumption guideline US gal/hr(liter/hr)

700

No

Yes

0.29(1.1098)

0.25 (0.946)

800

No

Yes

0.33(1.249)

0.31(1.173)

900

No

Yes

0.34(1.287)

0.33(1.249)

　　注：1USgallon=4USquart

　　注：A、計算滑油消耗率時，時間最好用發(fā)動機實際的運行時間，盡量不要用飛行小時。（發(fā)動機運行時間可電話咨詢技術支援）

　　B、因發(fā)動機滑油量在駕駛艙指示是1進制，指示精度較低，如加滑油后駕駛艙指示19，但可能實際油量并未到19，而只是18點幾。所以在實際運行中，如飛行一兩個小時左右，關車穩(wěn)定后，駕駛艙指示可能只有18甚至17，為正常指示現(xiàn)象，計算時可將大概誤差減掉。

　　2、如機組寫FLB，可參考以下格式統(tǒng)一答本,并放行：

　　參考737NG-FTD-79-14001該處關車后漏滑油為正?，F(xiàn)象，該發(fā)的滑油消耗率為滑油分油機分油溫度多少最好？US quart/hour，參考AMM71-00-00-800-806-F00在手冊標準滑油分油機分油溫度多少最好？US quart/hour范圍內(nèi)。

　　IT IS NORMAL THAT THE OIL LEAKING IN THE EXHAUST NOZZLE REF 737NG-FTD-79-14001.

　　THE CONSUMPTION OF OIL IS ? quart/hour. WITHIN THE LIMITS OF ？US quart/hour REF AMM71-00-00-800-806-F00.

故障原因

結論（MCC）

　　CFM56-7B關車后，尾噴內(nèi)集聚一灘滑油或從TRF6點鐘余油口處漏滑油屬于正?，F(xiàn)象

　　備注：只希望對故障的處理思路和方法有所啟發(fā)，目的在于交流，只作為參考，不作為故障處理的標準。

737NG-FTD-79-14001

　　ATA:

　　7900C00

　　Last Revised:

　　03-DEC-2014

　　Issue Title:

　　Oil Puddles in CMF56-7B Exhaust Nozzle

　　Originated:

　　03-DEC-2014

　　Airplane Model:

　　737NG

　　Minor Model(s):

　　Other Models:

　　no other models applied to issue

　　ECD:

　　Illustrations:

　　Oil Pooling in Exhaust Nozzle

　　References:

　　Issue Status:

　　Closed

　　Deion

　　Some 737NG operators have reported finding oil puddles in the exhaust nozzle during routine visual inspections. The purpose of this FTD article is to explain why the CFM56-7B engine exhibits oil in the exhaust system and inform that maintenance action is generally not required for oil in the exhaust system. A presentation on this subject, from the June 2014 CFM56-7B WTT Meeting, is attached to this FTD Article.

　　Background

　　Oil leakage from the rear turbine bearing compartment through the center vent tube and aft sump drain is normal for all CFM56-7B engines. The center vent tube evacuates air from the engine sumps and this air carries a small amount of oil. The aft sump drain can drain oil into the exhaust plug during engine motoring and during engine shutdown. During engine motoring, oil supply pressure increases faster than the aft sump air pressure. This causes in a momentary differential pressure that results a small amount of oil to pass over the aft sump rotating seal. The differential pressure can also occur during engine shutdown.

　　Oil from the center vent tube and aft sump drain can settle at the bottom of the exhaust plug. From there, the oil can seep through the flange, where the exhaust plug attaches to the turbine rear frame, and onto the exhaust nozzle.

　　Status

　　AMM 71-71-00 (Engine Vents and Drains) contains the following note:

　　An oil puddle in the exhaust system is usual. After engine dry or wet motoring, a large oil puddle in the exhaust system is usual. Oil leaks are possible at the turbine rear frame (TRF) and primary exhaust system flange. It is permitted to see oil drops at the TRF drain port at the 6:00 o’clock location.

　　There is no maintenance action required for oil puddles in the exhaust nozzle as long as oil consumption is within normal limits.

　　Interim Action

　　None

　　Final Action

　　There is no maintenance action required for oil puddles in the exhaust nozzle as long as oil consumption is within normal limits. If an operator suspects that the oil puddles may be more than normal, then we recommend looking at the oil consumption data from the operator normal oil consumption monitoring program. If the oil consumption is beyond normal limits per Section 9 of the Maintenance Planning Data (MPD) or AMM 71-00-00/201, Boeing recommends troubleshooting per FIM 79-05 Task 801, engine Oil Consumption is High (Oil Quantity Decreases at a Quick Rate).

　　Parts List:

　　No Parts Applied

　　Related Categories:

　　In Service Occurrences

　　Technical Focus Item

　　;font-size:12.0000pt;" >S quart/hour REF AMM71-00-00-800-806-F00.

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