Welcome to article #1! I am excited to create this multi-faceted content page as somewhat of a knowledge base for various aspects of aviation. Most posts will focus on improving common weakness areas I see on check-rides, but that will morph into many other aspects of aviation, and of course knowledge is knowledge, so I hope this is found beneficial to more than just near term applicants.
One of the most common gaps I see is in FAR 91.213… handling inoperative instruments and equipment. Let’s break that regulation down here and define some terms that may be confusing. In the end, I hope you gain a level of understanding regarding certification and inoperative equipment that will get you through most scenarios involving inoperative equipment.
So how do we handle the discovery of inoperative equipment? Let’s assume that during preflight you discover an instrument that isn’t working. 91.213 will walk us through the process.
Is there a Minimum Equipment List (MEL)? If so, abide by it. I don’t want to take too much time talking about MEL’s, because they rarely apply to piston aircraft in the GA/training environment. A MEL is a list of equipment onboard an aircraft, and it provides conditions for continuing operations in the event of inoperative equipment. MEL’s are generally provided/created by an operator and approved for use by the FAA via a letter of authorization (LOA). Similarly, in training, or small non-turbine aircraft, we will not see a Master Minimum Equipment List either (MMEL). This is similar to a MEL, however it was created by a designer for a fleet of aircraft as opposed to a particular aircraft.
Since we don’t have an MEL (or MMEL), let’s move on in the regulation. Next we need to make sure that the inoperative equipment is not part of the VFR-day type certification instruments and equipment under which your aircraft was certificated. What does this mean? Your aircraft was certified under a certain part of the regulations, and at that time, there were instrumentation requirements that had to be met for the aircraft to get certified. We really have two sources for this information. The first is the Type Certificate Data Sheet (TCDS). This is the document awarded by the FAA to a manufacturer after an aircraft meets certification standards. It includes limitations, equipment, and other applicable data. The second source of information is the equipment list (or Kinds of Operations Equipment List). If an item is required by either the TCDS or equipment list, you can’t go (without a special flight permit)!
So, we don’t have an MEL, and the inoperative item isn’t required by certification of the the equipment list in our POH/AFM. Now we must make sure the item isn’t required by 91.205 (or any other regulation) for our type of flight (VFR day, VFR night, IFR).
If it’s not required on any of the above, we need to verify that the equipment is not required by an Airworthiness Directive. This is harder to determine. But you need to have this knowledge so at a minimum, you can have a conversation with your mechanic.
We are almost there! We determined that the equipment isn’t required by any regulation/certification/equipment list. Now we need to handle the inoperative equipment. Here you have choices. You can either:
Have the equipment removed, the cockpit controlled placarded, and have all this logged in the maintenance records. Or;
Deactivate the inoperative equipment and placard it “Inoperative”. If the deactivation requires maintenance, it must also be recorded in the aircraft logs.
Last item listed in the regulations, and I always wonder why this isn’t first… make a determination as the pilot in command that it’s safe to fly!
In summary, this is pretty easy! When we find inoperative equipment, we should make sure it’s not required by certification requirements, 91.205 (or any regulation really), and by Airworthiness Directive. If we find its not required by those items, let’s deactivate it and placard it! If we can’t deactivate it, have a mechanic do it. If they can’t deactivate it, have them remove it. Anytime a mechanic takes action, make sure it’s properly logged. Now let’s go fly!
Since we brought up the topic of Type Certificate Data Sheets, let’s delve into that a tad bit more and discuss Supplemental Type Certificates and Field Approvals.
Earlier we mentioned that all equipment an aircraft is certified with will be listed on the aircraft’s TCDS. New technology is always being developed so how are we able to make upgrades? What if we want to install a piece of equipment onto our aircraft that isn’t listed on the TCDS?
When new technology is developed for a certified aircraft, the designer or manufacturer of the equipment can go the extra mile and apply for a Supplemental Type Certificate (STC). Then when they sell you that new piece of equipment that isn’t listed on your aircraft's TCDS, you can still install it if your aircraft is listed in the STC. It’s a supplement to your aircraft certification/TCDS.
What if the equipment you would like to install doesn’t come with a STC? Are you dead in the water? Nope! You have another option. You can work with a local Designated Airworthiness Representative (DAR) to provide a field approval for your alteration. This is documented on a FAA Form 337. A properly approved Form 337 becomes part of the aircraft records and also acts as a supplement to your aircraft certification/TCDS.
So! Do you want bigger wheels and tires on your Cessna, but the TCDS doesn’t specify that tire/wheel size? Search for a manufacturer that has provided a STC for your aircraft. Cant find one? Work with your mechanic and a DAR to get a field approval.
That's a lot of abbreviations! MEL, MMEL, KOEL, TCDS, DAR, STC, LOA… did I miss any? I hope this article gives you a better understanding of these items, and how they play a role in certification and ongoing aircraft operation.