Articles, Maintenance, Safety

Minimum Equipment: What Has to be Working?

Posted on Jan 11, 2021 by SCOTT WILLIAMS, ESQ.

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CIRRUS PILOTS ARE FORTUNATE to fly one of the most technologically advanced piston singles ever built. Unfortunately, the more advanced the equipment, the more there is that can go wrong. This simply isn’t your father’s C172.

FAR §91.213 says “no person may take off in an aircraft with inoperative instruments or equipment installed.” If we stop reading there, an inoperative air conditioning system would ground a Cirrus in the dead of winter. The exception that most of us rely upon is found in subpart (d)(1), which excludes small (under 12,500 pounds), non-turbine-powered airplanes for which a “master minimum equipment list has not been developed.” Does a Cirrus have an MMEL (Master Minimum Equipment List)? No, which means we can use the (d)(1) exception provided that:
(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;
(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;
(iii) Required by §91.205 or any other rule of this part for the specific kind of flight operation being conducted; or
(iv) Required to be operational by an airworthiness directive.

The subpart (d)(2)(iii) limitations are statutory in nature and not Cirrus-specific. As examples, under FAR §91.205, all aircraft must have an altimeter even for day-VFR operations, and any IFR flight requires an artificial horizon.

Kind of Operations Equipment List

What about (d)(2)(iii)’s Kind of Operations Equipment List (KOEL)? For the Cirrus pilot, that can be found in Section 2 (Limitations) of our Pilot Operating Handbook (POH). This chart, which will vary slightly between avionics systems and SR models, lists in detail what equipment must be working in order for a pilot to initiate a particular type of flight. The keyword here is “initiate.” A mere failure of equipment en route does not automatically require the declaration of an emergency or an immediate landing. Commonsense must prevail. However, just in case you thought that means that the pilot has sole discretion to define commonsense, please reference FAR §91.13 (the “careless and reckless” regulation).

Also, not all equipment or components are listed in the KOEL. As an extreme example, the Cirrus KOEL does not require the aircraft to have tires on the wheels or even wings. FAR §91.7 says no person may operate an aircraft unless it is in airworthy condition. Without tires, how can you accelerate to takeoff speed? How will you land safely?

Certain equipment is required for all flight operations in every Cirrus, such as a non-expired Cirrus Airframe Parachute System (CAPS). No, you can’t fly with an expired CAPS and call it “Experimental” since our aircraft are certified and not amateurbuilt. However, you can get a Special Flight (aka, ferry) Permit from your local FSDO to fly it to a service center for a repack. Figure 1 (on next page) lists fuel flow, oil temperature and oil pressure indications are always required, but CHT and EGT indications are not. As an example:

Batteries and alternators? It depends. The main bus (both ALT1 and BAT1) must be operational for all flights, but to fly IFR, the emergency bus (both ALT2 and BAT2) must also be working. Can you make a very short VFR flight with a fully charged BAT1 but an inoperative ALT1? Nope, because the KOEL mandates ALT1 for all types of flight (see Figure 2, next page).

Avidyne PFD? Only required for IFR flight. What about an Avidyne MFD? That’s been a healthy topic of discussion on our forums, but the general consensus is that as long as your PFD has Rev 7 or higher and can display oil temperature, the MFD is not required. Needless to say, if both the PFD and MFD are out, enjoy the airport cafĂ©.

Seat belts? Yes, one for each occupant. What about seat belt airbags and components? They were not even installed in early Cirrus models, so if those components have failed, can you just remove them and still fly? Some will say no, but the consensus is yes. The AmSafe system is not listed on the KOEL, nor are seatbelt airbags required under any FAR.



FIGURES 1 & 2 Kinds of Operations Equipment List (KOEL) Source: Cirrus POH, Section 2

What about wingtip strobes on a bright sunny day? Even though you may personally feel they are just not that important, the folks at Cirrus (and the FAA) say otherwise. Both strobes must be working, or you are grounded. For those of us with pre-LED strobes that might fail, maybe this should belong in your AOG kit.

If equipment is not required by regulation or KOEL, can we just fly?

Not so fast. In order to fly with nonrequired equipment that is inoperative, further action is required. The remainder of FAR §91.213 states:
(3) The inoperative instruments and equipment are –
(i) Removed from the aircraft, the cockpit control placarded, and the maintenance recorded in accordance with § 43.9 of this chapter; or
(ii) Deactivated and placarded “Inoperative.” If deactivation of the inoperative instrument or equipment involves maintenance, it must be accomplished and recorded in accordance with part 43 of this chapter; and
(4) A determination is made by a pilot, who is certificated and appropriately rated under part 61 of this chapter, or by a person, who is certificated and appropriately rated to perform maintenance on the aircraft, that the inoperative instrument or equipment does not constitute a hazard to the aircraft.

As used in (d)(3)(i), “Removed” seems relatively straightforward, but what if equipment is only partially working? For example, a GNS430 may have no GPS signal and therefore the GPS navigation feature is inoperative (INOP), but the radio and VOR functions still work. It would seem silly to yank out a perfectly good radio, so a placard of “GPS Function INOP” would probably suffice to meet the regulation’s intent. If removed, an entry must be made in the airframe logbook to document the removal. Some items may be removed by a pilot (such as a radio that slides out of a tray), while others (i.e., an autopilot) require a certified mechanic.

“Deactivated” (d)(3)(ii) is a bit more esoteric. If it has a power switch, just turn it off. No power switch? Pull and collar the circuit breaker? Fine, so long as that breaker does not also power other equipment that is still operative. The FAA once published an Advisory Circular 91-67 on this subject, but it was terminated in 2017, and no replacement has been made available yet.

Finally, under a June 13, 2018, Opinion Letter¹ the FAA’s Office of the Chief Counsel has opined that the benefits of subpart (d)(3) are only valid until the next annual (or 100-hour, if required) inspection. At that time, the equipment needs to be re-evaluated and the proper determinations made. It does not necessarily mean that INOP equipment must be repaired or replaced at the next annual. It only means that its non-functional status receives a fresh look at that time. In other words, no equipment can be permanently placarded “INOP” without reaffirming that determination.

Inoperative … “sometimes”?

Some equipment may work fine 95% of the time but have an intermittent failure 5% of the time. How much is too much before we must declare it inoperative? Perhaps this is where subpart (d)(4) comes into play: “inoperative [intermittent] instrument or equipment does not constitute a hazard to the aircraft.” Is 5% too much? What about 1%? That might depend on which equipment. An oil pressure indicator that seems to fail for 30 seconds every half hour or so can probably wait until you get home. A glideslope indicator that fails for 30 seconds IMC inside the final approach fix will necessitate a missed approach, and that is serious. No regulation can be written for every conceivable scenario, so apply commonsense. In our world, that is best defined as “What would I do if an FSDO inspector were flying with me?”


This article was initially published in the November / December 2020 issue of COPA Pilot.

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