Few of us will forget the first time we faced all the dials, gauges, knobs, and switches in a typical general aviation airplane. Glass cockpit avionics in newer airplanes are less cluttered; still, all the gadgetry can be intimidating to the novice. Over time, though, we come to know and understand the equipment that allows us to aviate, navigate, and communicate in our trips to and from the sky.

Because it is extremely reliable, we also learn to trust that equipment. Unlike the aviators of an earlier age, who always launched wondering what would break and when it would happen, most pilots of today’s aircraft take the reliability of our machines for granted. But equipment can and does fail. As the saying goes, aviation is terribly unforgiving of carelessness, incapacity, or neglect. Consequently, there are some fairly precise rules – Title 14 Code of Federal Regulations (14 CFR) section 91.213 to be exact – to guide the go/no-go decision when you find faulty equipment in the airplane you plan to fly.

For most general aviation aircraft, the key regulation for determining airworthiness of an aircraft with inoperative equipment is 14 CFR section 91.213(d). If you find something wrong with the aircraft, here is a four-question checklist you can use to determine if that problem renders it unairworthy.

Question 1: VFR-Day Type Certificate.  Is the deficient equipment part of the aircraft’s VFR-day type certificate? If yes, then the aircraft is unairworthy.

Question 2: Listed as Required on Equipment List or KOEL? Is the affected equipment listed as required on the aircraft’s equipment list or on its Kinds of Operations Equipment List (KOEL)? If yes, then the aircraft is unairworthy.

Before we continue, though, let’s take a closer look at these lists. The aircraft’s equipment list is usually located near the back of the pilot operating handbook (POH) or airplane flight manual (AFM). If you haven’t paid much attention to it before, take a minute now to pull out the POH/AFM and take a look. If the list shows that the manufacturer considers the equipment required, then the aircraft is not airworthy if that item is inoperative.

If you fly one of the newer aircraft, you need to be familiar with the Kinds of Operations Equipment List, which is generally located in the Operating Limitations Section of the POH/ AFM. The KOEL is meant to be an easy-to-use reference for what the manufacturer deems essential for particular operations. In the Cessna C182T Nav III POH, for example, the KOEL is set up in table form. The left-hand column lists the item or system and the next four columns allow the manufacturer to say whether the system is required for a given kind of operation: VFR day, VFR night, IFR day, and IFR night. The right-hand column allows for comments.

For example, the KOEL indicates that the C182T Nav III POH/AFM is required for all four operations, and the comment states that the POH/ AFM must be accessible to the pilot in flight. Most pilots of my acquaintance are surprised to learn from the KOEL that the manufacturer does not require the 24V standby battery to be operative for any of the four kinds of operations, but a prudent pilot might want to think hard about launching into day or night instrument meteorological conditions (IMC) without it.

Question 3: Required by Any Other Regulation? Is the affected equipment required by any other regulation, i.e., 14 CFR sections 91.205 and 91.207? If yes, then the aircraft is considered to be unairworthy. You need to be familiar with both of these equipment-related regulations. The first, 14 CFR section 91.205, lists the instruments and equipment required for different types of flight. Some pilots use acronyms (e.g., TOMATO FLAMES) to remember these items. Another way is to think of them in terms of three categories: engine, performance/navigation, and safety.

Question 4: Required by Any Other Regulation? Is the affected equipment required to be operative by an airworthiness directive? If so, the aircraft is considered unairworthy.

Now What? If you were able to answer each of the four questions in the negative, then the aircraft is not unairworthy – but you still have some work to do before you can legally fly. Specifically, 14 CFR section 91.213 (d) requires that you remove or deactivate the inoperative item, placard it as inoperative, and record your actions in the maintenance log. If you take this step, though, remember that 14 CFR section 91.405(c) requires that it be repaired, replaced, removed, or inspected at the next required inspection.

Know before you go, because it takes all kinds of (operative) equipment to ensure a safe flight.  (FAA Safety Briefing – MarApr 2010)