问题 1：滑油压力警告触发条件
为什么 LOW OIL PRESSURE（滑油压力低）警告仅在滑油压力降至零时触发？是否应在零以上设定警告阈值，以便提供更早的提示？
回复 1：
参见参考文献 /B/ 与 /C/ 中《滑油压力指示系统》SDS（系统说明书）。根据 FCOM（飞行机组操作手册）《滑油压力指示》（参考 /D/ 和 /E/），滑油压力降低时会显示琥珀色区域（Amber Band）或红线（Redline）。琥珀色区域是早期提示，红线为最低限制。有关 LOW OIL PRESSURE 的说明，参见 QRH（快速参考手册）非正常检查单（参考 /F/ 和 /G/）。
737NG：
当滑油压力低于红线限制时，电子发动机控制（EEC）会向显示电子组件（DEUs）发送信号，导致显示组件（DU）出现琥珀色"LOW OIL PRESSURE" （低滑油压力）信息。每台发动机对应一条独立显示的低滑油压力信息，该信息在主发动机显示器上呈现。
当滑油压力低于红线限制时，琥珀色"LOW OIL PRESSURE"信息将闪烁10秒后转为持续显示。显示电子组件（DEUs）在起飞和着陆阶段会抑制该信息的闪烁功能。
所有三个机组告警框将同步闪烁10秒，随后相关告警信息转为持续显示。发动机启动期间，电子发动机控制（EEC）会阻止指示器及指针变为琥珀色或红色。
737MAX：
滑油压力（低）琥珀色限制定义了发动机润滑系统的警戒工作压力范围。滑油压力（低）琥珀色限制以琥珀色（黄色）刻度线形式显示在柱状刻度上。
若滑油压力低于琥珀色限制但高于红线限制，主显示系统（MDS）会将滑油压力数字读数及外框颜色变为琥珀色。当压力值恢复正常范围后，MDS将滑油压力数字读数及外框恢复为正常颜色显示。
滑油压力（低）红线定义了发动机润滑系统的非正常工作压力范围。滑油压力（低）红线限制以红色刻度线形式显示在柱状刻度上。
若发动机滑油压力降至红线限制以下，MDS会将滑油压力数字读数及外框变为红色。当压力值恢复正常范围后，MDS将滑油压力数字读数及外框恢复为正常颜色显示。
当滑油压力低于红线限制时，"LOW OIL PRESSURE"（低滑油压力）琥珀色信息将闪烁10秒后持续显示。起飞和着陆阶段，DPCs将禁止该信息的闪烁模式。发动机启动期间，电子发动机控制（EEC）会禁止指示器和指针变为琥珀色或红色。
问题 2：记忆项目分类
鉴于滑油压力低可能导致严重发动机损坏，为何该项目在 QRH 中未被列为记忆项目？
回复 2：
根据 FAA 8900.1 第3卷第32章第5节：
3-3240 立即动作（Immediate Actions）
立即动作是指必须在极短时间内完成，以避免或稳定危急状态的操作，此类情况下机组成员无暇查阅手册或检查单。机组必须熟悉并能够正确、可靠地从记忆中执行这些动作。POI 必须确保立即动作情景被包含在运营人的 AFM 或 CFM 中。此类情景包括但不限于：
机组成员丧失操作能力的迫切威胁
飞机操纵能力丧失的迫切威胁
系统或部件毁损且继续飞行及后续着陆的安全性极不可能的迫切威胁
此外，AC 120-71B指出：
4.2.5 记忆项目
应尽可能避免使用记忆项目。如必须包含，应在训练中予以强调、数量不超过三项，且不得包含条件性决策步骤。
对于 ENGINE LOW OIL PRESSURE（发动机滑油压力低）NNC，当滑油压力处于或低于红线时，指引机组执行 Engine Failure or Shutdown（发动机失效或关车）检查单。在此情景下，及时执行该检查单可在滑油损失情况下减少发动机损坏风险。根据 AFM（飞行手册）限制，当滑油压力处于或低于红线时，必须尽快关闭发动机。
AFM 中并未规定滑油压力低时关车的时间限制。但当出现 ENGINE LOW OIL PRESSURE 指示时，按程序执行发动机失效或关车 NNC 即可在恰当时间内完成关车，减少发动机损坏风险。
FCTM（飞行机组训练手册）关于空中发动机关车的推荐技术强调：在完全控制飞行航迹并通过有条理、系统化的程序识别受影响发动机且确保不关闭正常发动机之前，不应关车。因此，FCTM 明确指出：“即使出现火警，也不要仓促完成关车检查单。”
波音预期机组应保持对滑油压力琥珀色提示的关注。当滑油压力达到或低于红线时，机组能及时执行发动机失效或关车 NNC，从而减少发动机损坏。
问题 3：滑油温度过高的危害
在 737 发动机上，滑油温度过高的具体风险有哪些？是否可能导致不可逆的发动机损坏？
回复 3：
参见 QRH《ENGINE OIL HIGH TEMPERATURE》（发动机滑油温度高）NNC。飞机发动机的滑油温度过高可能导致润滑性能下降、潜在的发动机损坏，并在严重情况下造成发动机失效。有关《滑油温度指示系统》的 SDS，请参见参考 /K/ 与 /L/。
737NG:
737MAX:
参考LFROM: THE BOEING COMPANY
TO: Shandong Airlines (SHG)
SUBJECT: Engine Oil System
REFERENCES:
/A/ SHG-SHG-25-0530-01C
/B/ 737MAX_SHG_SDS_PAGESET-G79-30-00-004_ENGINE OIL - INDICATING - OIL PRESSURE INDICATING SYSTEM
/C/ 737NG_SHG_SDS_PAGESET-F79-30-00-040_ENGINE OIL - INDICATING - OIL PRESSURE INDICATING SYSTEM
/D/ 737MAX_SHG_FCOM_V1V2_Oil Pressure-Temperature Indications
/E/ 737NG_SHG_FCOM_V1V2_Oil Pressure-Temperature Indications
/F/ 737MAX_SHG_QRH2_NNC_ENGINE LOW OIL PRESSURE
/G/ 737NG_SHG_QRH2_NNC_ENGINE LOW OIL PRESSURE
/H/ FAA Order 8900.1_Volume 3_Chapter 32_Section 5
/I/ 737MAX_SHG_QRH2_NNC_ENGINE HIGH OIL TEMPERATURE
/J/ 737NG_SHG_QRH2_NNC_ENGINE HIGH OIL TEMPERATURE
/K/ 737MAX_SHG_SDS_PAGESET-G79-30-00-005_ENGINE OIL - INDICATING - OIL TEMPERATURE INDICATING SYSTEM
/L/ 737NG_SHG_SDS_PAGESET-F79-30-00-050_ENGINE OIL - INDICATING - OIL TEMPERATURE INDICATING SYSTEM
/M/ FAA AC_120-71B
DESCRIPTION:
There is a file attached to this message that has not been sent as it has been flagged with enhanced control. You must login to view this file attachment.
This message is in regards to the 737 FCOM
SHG requests the following clarifications for this item:
I am writing to seek clarification regarding the 737 engine oil system, specifically in relation to the alert logic and operational considerations for oil pressure and temperature. During our internal training and operational review, several technical questions arose, and we would greatly appreciate Boeing’s insight.
Q1. Oil Pressure Warning Trigger
Why does the LOW OIL PRESSURE alert only activate when oil pressure drops to zero? Shouldn’t there be a warning threshold above zero to provide an earlier indication?
Q2. Memory Item Classification
Considering that low oil pressure can lead to severe engine damage, why isn’t it classified as a memory item in the QRH?
Q3. High Oil Temperature Hazards
What are the specific risks associated with high oil temperature on the 737 engines? Can it lead to irreversible engine damage?
RESPONSE:
Q1. Oil Pressure Warning Trigger
Why does the LOW OIL PRESSURE alert only activate when oil pressure drops to zero? Shouldn’t there be a warning threshold above zero to provide an earlier indication?
R1. See Ref /B/ and Ref /C/ for SDS on the Oil Pressure Indication System. From the FCOM Oil Pressure Indications (Ref /D/ and Ref /E/) will display "Amber Band" or "Redline" for Lower Oil Pressure. The "Amber Band" is the earlier indication before the "Redline". For "LOW OIL PRESSURE," see QRH NNC Ref /F/ and Ref /G/.
Q2. Memory Item Classification
Considering that low oil pressure can lead to severe engine damage, why isn’t it classified as a memory item in the QRH?
R2. Per FAA Order 8900.1, Volume 3, Chapter 32, Section 5 (Ref /H/):
3-3240 IMMEDIATE ACTIONS. An immediate action is an action that must be accomplished so expeditiously (in order to avoid or stabilize a hazardous situation) that time is not available for a crewmember to refer to a manual or checklist. Crewmembers must be so familiar with these actions that they can perform them correctly and reliably from memory. POIs must ensure that immediate action situations are included in an operator’s AFM or CFM, as appropriate. Situations that require immediate action include, but are not limited to, the following:
Imminent threat of crewmember incapacitation.
Imminent threat of loss of aircraft control.
Imminent threat of destruction of a system or component, which makes continued safety of the flight and subsequent landing improbable.
In addition, AC 120-71B states (Ref /M/):
4.2.5 Memory Items: Memory items should be avoided whenever possible. If the procedure must include memory items, they should be clearly identified, emphasized in training, less than three items, and should not contain conditional decision steps.
The ENGINE LOW OIL PRESSURE NNC, directs the flight crew to do the Engine Failure or Shutdown checklist if the engine oil pressure is at or below redline. In this scenario, prompt execution of the Engine Failure or Shutdown NNC limits damage to the engine due to oil loss. Per the AFM limitation, the engine needs to be shutdown as soon as possible if the oil pressure is at or below the Redline.
There are no published time limits for engine shutdown when the oil pressure is low. The AFM engine oil limitations and AFM Engine Low Oil Pressure Non-Normal Procedures do not specify a time limit. But, performing the Engine Failure or Shutdown NNC when prompted by the ENGINE LOW OIL PRESSURE Indication, results in a timely engine shutdown in response to an engine oil pressure at or below redline.
The FCTM Recommended Technique for an In-Flight Engine Shutdown emphasizes not shutting the engine until the flight path is under complete control and a deliberate, systematic process is used to identify the affected engine and ensure that the operating engine is not shut down. This is necessary for safety of flight and for this reason, the FCTM states "Do not rush through the shutdown checklist, even for a fire indication.”
Boeing expects flight crews to maintain awareness of the engine oil pressure amber condition. So, if the engine oil pressure reaches or dips below the redline, the flight crew performs the Engine Failure or Shutdown NNC in a timely manner and limits damage to the engine
Q3. High Oil Temperature Hazards
What are the specific risks associated with high oil temperature on the 737 engines? Can it lead to irreversible engine damage?
R3. See QRH “ENGINE OIL HIGH TEMPERATURE” NNC (Ref /I/ and Ref /J/). High oil temperature in aircraft engines can lead to reduced lubrication, potential engine damage, and, in severe cases, engine failure. For more SDS of the Oil Temperature Indication System, see Ref /K/ and Ref /L/.
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Hung Lam, Flight Operations Engineering (FLOE)
Reginald Guinto, Manager
Customer Support
The Boeing Company
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