看个长难句

Since the Lion Air crash, pilots certified to fly the Max have complained that they were not briefed on the new system or on how to counter it should incorrect data force the nose down.

自狮航失事后，经认证可驾驶该Max机型的飞行员已抱怨过，他们从未听取过这一新系统的介绍，或被告知如何应对一旦错误数据迫使机头下压的情况。

阅读解析前，试着自己先分析看看。

Since the Lion Air crash, Pilots certified to fly the Max have complained that [they were not briefed on the new system or on how to counter it should incorrect data force the nose down].

· 首先看整个句子结构，主语：pilots，飞行员，谓语：complain，抱怨，宾语：that []，抱怨的内容也就是that后面整个从句。

· pilots飞行员，什么样的飞行员，(who were) certified to fly the Max，用来修饰飞行员，经认证可驾驶该Max机型的飞行员。

· 具体来看抱怨的内容[they were not briefed on the new system or on how to counter it should incorrect data force the nose down]；飞行员抱怨了两件事情，由or分成两点：

其一，they were not briefed on the new system 他们没有听取过这一新系统的介绍、没有被介绍过这一新系统；这里的brief sb on sth表示“向某人介绍，提供信息”（to give someone all the information about a situation that they will need）；

其二，抱怨了什么呢？也就是or后面的句子，注意or后面还有一个on，结合前面抱怨的内容，可以推出，抱怨的第二件事还是没有被介绍过/没有被告知某事，也就是they were not briefed on how to counter it. 没有被告知如何应对它。

而这里的它指的是什么呢？how to counter it should incorrect data force the nose down，后面还跟了个虚拟语气的倒装句，可还原为：if incorrect data should force the nose down, 所以it指的就是虚拟语气所描述的情况——如果出现错误数据迫使机头下压，要如何解决？而飞行员抱怨的就是没有被告知解决办法。

所以我们可以把飞行员抱怨的第二点还原为：they were not briefed on how to counter it, if incorrect data should force the nose down. 他们没有被告知如何应对一旦错误数据迫使机头下压的情况。

最后，再体会下这个句子吧：

Since the Lion Air crash, Pilots certified to fly the Max have complained that [they were not briefed on the new system or on how to counter it should incorrect data force the nose down].

自狮航失事后，经认证可驾驶该Max机型的飞行员已抱怨过，他们从未听取过这一新系统的介绍，或被告知如何应对一旦错误数据迫使机头下压的情况。

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