In which situation is altimeter testing and inspection not required?

Altimeter testing and inspection are typically not required for aircraft that operate under Day VFR (Visual Flight Rules) only. This is because Day VFR operations do not necessitate the same level of precision and reliability in altimeter readings as Instrument Flight Rules (IFR) operations do. Under Day VFR, pilots are allowed to navigate and operate solely by visual reference, meaning that their reliance on the altimeter for altitude determination is not critical for safe operation.

In contrast, aircraft with IFR certification must undergo more stringent altimeter testing and inspection procedures to ensure accuracy in altitude reporting, as they may be flying in conditions where visibility is poor and relying heavily on instruments. Similarly, aircraft with a calibrated altimeter would still need to meet regulatory requirements for accurate operation, which often includes regular checks and maintenance. Additionally, the weight of an aircraft does not inherently exempt it from altimeter testing; rather, regulations are applied based on operational use and certification. Thus, the context of operation under VFR for Day Only is the key reason why altimeter testing and inspection are not mandated in that scenario.