If the equipment is not required, the item should be disabled and placarded as inoperative.
In order to determine if an item is required, there are a few steps to consider.
1. Is the item required by the aircraft type certificate?
2. Is the item required by a minimum equipment list?*
3. Is the item required by regulation for the type of flight, such as VFR day or VFR night?
4. Is the item required by company policy or operation specifications?
5. Is the item required by the pilot in command for safe flight?
* Minimum equipment lists are not common for part 91 operations. A minimum equipment list is a formally approved document for a specific aircraft that identifies which items or equipment may be inoperative and under what conditions. For example, an MEL may allow a pop-out float to be inoperative if the flight does not occur over water.
14 CFR 91.213 Inoperative Instruments and Equipment