CORRECT!

5). You check the flight instruments while taxiing and find that the vertical speed indicator (VSI) indicates a descent of 100 feet per minute. In this case, you

a). may take off and use 100 feet descent as the zero indication.
b). may not take off until the instrument is corrected by either the pilot or a mechanic.
c). must return to the parking area and have the instrument corrected by an authorized instrument repairman.
The answer is:
a). may take off and use 100 feet descent as the zero indication.

'Heresy', you scream, outraged that an inaccurate VSI doesn't require the pilot to land immediately to have the problem fixed. But, take a look at FAR Part 91.205 (d) first. After you digest what the regs are saying, consider this: the words 'vertical speed indicator' or the acronym 'VSI' don't appear anywhere in this reg. That's beacause IFR flight can be legally conducted without one.

That said, you can usually take a small screwdriver and find the adjustment screw on the case of the VSI and zero it out yourself. Otherwise, you have to factor in the error when using the instrument. Or, better yet, just placard it 'inop' so you don't get confused in the middle of a tight approach.

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