When it becomes necessary to examine the altitude performance of an aircraft engine, three types of facilities may be used-altitude wind tunnels, altitude test beds and flying test beds.

当需要考察一台航空发动机的高空性能时，可以利用三种型式的设备，即高空风洞、高空试验台和飞行试验台。

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When it becomes necessary to examine the altitude performance of an aircraft engine, three types of facilities may be used-altitude wind tunnels, altitude test beds and flying test beds.

当需要考察一台航空发动机的高空性能时，可以利用三种型式的设备，即高空风洞、高空试验台和飞行试验台。

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