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Let's say my vacuum gauge is not working on my C172S and I want to go day VFR flying. There is no MEL. 14 CFR 91.213 details procedures for inoperative instruments, and I think the following paragraph applies to my operation, so let me go through these one by one:

(d) Except for operations conducted in accordance with paragraph (a) or (c) of this section, a person may takeoff an aircraft in operations conducted under this part with inoperative instruments and equipment without an approved Minimum Equipment List provided -

...

(2) The inoperative instruments and equipment are not -

(i) Part of the VFR-day type certification instruments and equipment prescribed in the applicable airworthiness regulations under which the aircraft was type certificated; (N/A, vacuum gauge not part of TOMATO FLAMES)

(ii) Indicated as required on the aircraft's equipment list, or on the Kinds of Operations Equipment List for the kind of flight operation being conducted; (not sure here*)

(iii) Required by § 91.205 or any other rule of this part for the specific kind of flight operation being conducted; (N/A, not conducting flight at night or IFR)

(iv) Required to be operational by an airworthiness directive; (N/A, let's assume no applibale ADs)

*This is interesting language: "Indicated as required on the aircraft's equipment list". AFAIK, to determine if the vacuum gauge fits this description, I should consult the equipment list in the POH, which reads:

C172S POH

Ok, so I now assume any instrument with a number ending in "-R" is "required" for the purposes of complying with the above regulation. Locating the vacuum gauge in the equipment list, I see it indeed has a suffix "-R", indicating it is a "required item for FAA certification":

enter image description here

Thus I am led to conclude that the vacuum gauge is "indicated as required on the aircraft's equipment list", and hence continuing my flight would be in violation of 14 CFR 91.213.

Is my reading of the regulation and my interpretation of "required item" accurate here?

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  • $\begingroup$ Closely related, perhaps a dupe? $\endgroup$ – Pondlife Dec 3 '19 at 4:10
  • $\begingroup$ I don't have time to write it up now, but my initial answer would be that the vac/amp gauge is required, for day VFR flight, and accordingly one is needed. A question is what is the process to be able to fly without the vac gauge operative, and just the ampmeter. However, I would like to point out that in most C172 the vac pump is driven off the accessory drive, and failure of the pump could put the accessory drive at risk, and accordingly there is value in detection of a vac failure, therefore it would be imprudent to operate without the gauge. The determination could vary between FSDOs. $\endgroup$ – mongo Dec 4 '19 at 18:29
  • $\begingroup$ Which 172S? G1000? $\endgroup$ – wbeard52 Dec 7 '19 at 4:29

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