What should you do if an altimeter has not been inspected within the preceding 24 calendar months during an annual inspection?

When an altimeter has not been inspected within the preceding 24 calendar months, the appropriate action is to approve the aircraft for return to service while advising against IFR (Instrument Flight Rules) usage. This is based on regulations that require altimeters to be calibrated and inspected at specified intervals to ensure their accuracy and reliability, especially when operating under IFR conditions, where precision is critical for safe flight operations.

If the altimeter is past due for its inspection, it indicates that it has not met the regulatory requirements for maintaining IFR operations. By approving the aircraft for return to service yet advising against IFR usage, the flight operation is being guided to stay within safe parameters, acknowledging that the altimeter does not meet the necessary standards for instrument flight. The pilot or operator can still use the aircraft for VFR (Visual Flight Rules) flights, where altimeter accuracy is less critical compared to IFR flights.

This approach helps to ensure safety while still allowing flexibility in the aircraft's use until the altimeter can be properly inspected and recertified.