References:参考 Other Quick Reference Handbook(QRH) - NNC12
Issue Status: Closed 问题状态：关闭
Revision Description 修订描述
This article has been revised to bring awareness to a recent increase in diversions caused by fuel FILTER BYPASS indications. The information about the diversions has been added to the Description section.
近日因燃油滤旁通（FILTER BYPASS）的备降有所增加，为引起重视，本文件已修订。关于此类备降的信息已经加入描述章节。
Description 描述
In recent years, there has been an increase in the number of diversions caused by fuel FILTER BYPASS indications. There were 49 diversions reported between Jan2014 and Aug2017, making up 20 percent of all engine-related diversions on the737NG fleet. Boeing is republishing this Fleet Team Digest article to remind operators of the recommended actions following a fuel FILTER BYPASS indication, in an effort to reduce the number of unnecessary diversions.
近几年，因燃油滤旁通（FILTER BYPASS）备降的数量上有所增加，在2014.01-2017.08期间，有49份相关备降报告，占737NG机队所有发动机相关备降报告的20%。波音公司在《机队文摘》（Fleet Team Digest）中发表该篇文章，目的在于提醒运营人遇到燃油滤旁通（FILTER BYPASS）警告时的推荐措施，从而减少不必要的备降次数。
If a single FILTER BYPASS light illuminates(engine number1 or engine number2) and there are N1 and/or N2 fluctuations, this may be an indication of contaminated fuel. If a single FILTER BYPASS light illuminates and N1 and N2 are stable(i.e. there is no erratic engine behavior), per the QRH non-normal checklist, a diversion is not necessarily required. For example, a diversion most likely would not be
required if there are suitable diversion alternates along the planned flight route.
-如果单个（一号或二号发动机的）（FILTER BYPASS）灯亮起同时N1/N2指示波动起伏，则这可能是燃油污染引起。
-如果单个（一号或二号发动机的）（FILTER BYPASS）灯亮起而N1/N2指示稳定（即发动机没有突然的变化），则按照QRH非正常检查单所示，不需要备降。例如，如果在计划航路上有合适备降场，那么备降很可能也不是必须的。
However, if an aircraft is about to enter an ETOPS segment when a single FILTER BYPASS illuminates, it may be appropriate to divert to an alternate airport rather than continue an over-water flight, even if
the other engine indications remain stable. In all cases, the pilot in command must assess the situation and take appropriate action.
然而，如果飞机即将进入ETOPS阶段时出现了单个的燃油滤旁通（FILTER BYPASS）警告，那么这时候可能就需要改航到备降机场而不是继续跨水飞行了，即便另一台发动机指示保持正常稳定。
在所有情况下，机长必须评估当时状况并采取合适的行动。
If both FILTER BYPASS lights illuminate for engine number1 and engine number2 during the same flight(either separately or at the same time), plan to land at the nearest suitable airport per the QRH non-normal checklist.
如果在同一航班上一号和二号发动机的两个滤旁通（FILTER BYPASS）警告灯都亮了（无论分别亮还是同时亮），则依据QRH非正常检查单，计划在就近合适机场着陆。
Background 背景
The fuel filter bypass warning system provides an indication of an impending fuel filter bypass when the differential pressure switch in the engine fuel filter is actuated. This actuation occurs when the
difference between filter inlet pressure and outlet pressure rises above 11.5 psid. The FILTER BYPASS light on the P5-2 panel and MASTER CAUTION indicator illuminate when the differential pressure switch is actuated.
当发动机燃油滤中的压差开关被触发，燃油滤旁通警告系统将提供一个即将旁通燃油滤的指示。其触发条件是：当燃油滤进口与出口的压力差达到11.5psid时压差开关被触发。当压差开关触发，P5-2面板的滤旁通（FILTER BYPASS）灯和主注意灯（MASTER CAUTION）亮起。
Fuel filter bypass indications are required by the Federal Aviation Administration(FAA). In its publication "Airplane Turbofan Engine Operation and Malfunctions- Basic Familiarization for Flight Crews," the FAA explains, "If the fuel filter at the fuel inlet becomes clogged, an impending bypass indication will alert the crew for a short while before the filter actually goes into bypass"
FAA要求安装燃油滤旁通指示，在其《飞机涡扇发动机运行和故障-基本机组熟悉》中FAA写到：“如果进油口的燃油滤被堵塞，那么‘即将旁通的指示’会在燃油滤确实旁通前给机组一个短时的预警。”
Status 状态
There are no changes to the current status of the fuel FILTER BYPASS instructions in the FCOM.
目前，在FCOM中关于燃油滤旁通（FILTER BYPASS）说明的状态没有改变。
编译：南航新疆分公司 机长 杨坤
校对：南航广州分公司 机长 马徐东 南航珠海分公司 机长 李永联
