Final answer:
A dial indicator or dial test indicator is used to measure the runout of an aircraft engine crankshaft to ensure proper alignment.
Step-by-step explanation:
The type of measuring instrument used to measure the runout of an aircraft engine crankshaft is a dial indicator or a dial test indicator. This precision instrument can accurately measure small distances and rotational deviations to ensure the crankshaft is well-aligned and does not wobble as it rotates. Proper runout measurement is crucial for the performance and safety of the engine, as excessive runout can lead to vibrations, wear and tear on bearings, and eventual engine failure.