Final answer:
When conducting a case leak test at an indicated altitude of 18,000 feet, the leakage of the altimeter case should not result in a change of the altimeter reading by more than a certain amount.
Step-by-step explanation:
When conducting a case leak test at an indicated altitude of 18,000 feet, the leakage of the altimeter case should not result in a change of the altimeter reading by more than a certain amount.
The specific maximum allowable change in the altimeter reading due to case leakage is typically determined by regulatory authorities, such as the Federal Aviation Administration (FAA) in the United States. The exact value can vary depending on the type of aircraft and altimeter being used.
For example, in the United States, the FAA requires that the altimeter reading should not be affected by more than 75 feet during a leak test at an indicated altitude of 18,000 feet. This means that if there is any case leakage during the test, the altimeter reading should not change by more than 75 feet.