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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, 2019 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, 2019 at 18:29
  • $\begingroup$ Which 172S? G1000? $\endgroup$
    – wbeard52
    Dec 7, 2019 at 4:29
  • $\begingroup$ What does "TOMATO FLAMES" mean? I'm assuming it doesn't refer to a pilot burning tomatoes in flight? $\endgroup$
    – Someone
    Feb 8 at 21:23
  • $\begingroup$ No, you're mistaking the equipment list required for certification of the airplane with the Minimum Equipment List, which is a list of equipment that can be inoperative when a flight is begun. Small GA airplanes often don't have a MEL, but larger airplanes that have multiple instances of equipment for redundancy, may have the equipment listed on the MEL, indicating for how long the item can be inop, and any limitations, especially if some other equip has also failed, which may reduce the safety margin too much. $\endgroup$
    – Pete P.
    Jul 10 at 9:28

1 Answer 1

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Your reading is correct: a Cessna 172 with an inoperative vacuum gauge is not airworthy.

Type Certificate Data Sheet No. 3A12, Revision 85 shows how Cessna 172 models meet FAA airworthiness requirements. Section XII, “Model 172S, Skyhawk SP, 4 PCLM (Normal Category), 2 PCLM (Utility Category), Approved May 1, 1998,” contains

Equipment
The basic required equipment as prescribed in the applicable airworthiness regulations (see Certification Basis) must be installed in the airplane for certification …

NOTE 2: Pilot’s Operating Handbook and FAA Approved Airplane Flight Manual (POH/AFM): part number 172SPHUS-00 (or later approved revision) is applicable to the Model 172S. The airplane must be operated according to the appropriate POH/AFM …

The Comprehensive Equipment List in Section 6 of the POH/AFM gives the Combination Vacuum Ga[u]ge/Ammeter the R suffix, meaning required.

FAR 91.213(d)(2)(ii) reads

(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 -

    (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;

But the equipment list does indicate the gauge as required, so this exception does not apply.

To fly the airplane to a repair station to fix the vacuum gauge, apply for a Special Flight Permit (or “Ferry Permit”) with your geographic region’s Flight Standards Office, as provided in FAR 21.197.

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