SR 3-5484124776
2022年11月，运行中有飞机反应发生燃油不平衡警告，经确认为在左右油箱泵均打开的情况下，交输活门未关闭。在交输活门未关闭是否为导致燃油不平衡的问题上存在争议，一种认为每个泵出口压力都一致，那么就该各供各发的燃油，即使开着交输活门也不应该发生这一问题。就此与波音做了沟通。相关答复如下：
R1: Boeing confirms that the opened Crossfeed valve could potentially lead to the Fuel Imbalance condition described in the Ref /F/. Boeing notes that there is no Boeing procedure that requires the fuel Crossfeed valve to be open for an extended period of time in normal two-engine operations with all fuel pumps operating. The Crossfeed valve is verified being closed before departure (refer to the Ref /H/ attached FCOM extract) and stays closed during the whole flight unless a Fuel Balancing Procedure (refer to the Ref /I/) needs to be performed or if directed by the Non-Normal Checklist.
R2: Boeing highly recommends Hainan Airlines (HNA) follow the FCOM procedure and switch the Crossfeed valve to the Closed position during regular flights.
就从系统工作角度理解如下：
结合译码的情况，还原整个事件的过程如下：地面左右油箱加油后，使用APU，如果不开泵会消耗左主油箱的油量。但从发动机启动阶段的油量可知，右主油箱（8290LB）是少于左主油箱（8420LB）的。表明有打右主油箱泵并开了交输活门，才会让APU消耗的是右主油箱的油量。随后在打开左主油箱前后泵启动发动机时，交输活门仍然在开位，相当于总管中同时有4个泵提供燃油。由于每个泵的输出流量是会存在差异的（只要满足最低流量要求），同时供给总管也会存差异。厂家在FIM手册中28-41 TASK 820对于燃油构型问题的可能性中，就包括交输活门未完全关闭。表明交输活门的不完全关闭尚且会产生不平衡的状态，何况完全打开的情况。