Two Questions: Who is responsible for airworthiness and where is it in the FARs?

Sept. 1, 2004
If you ask a general aviation mechanic this question: Who is primarily responsible for the airworthiness of the aircraft? Young or old, he will answer immediately and without batting an eye

If you ask a general aviation mechanic this question: ?Who is primarily responsible for the airworthiness of the aircraft?? Young or old, he will answer immediately and without batting an eye: ?Owner or operator!? And he would be right.

Then I set them up for the next question. ?Where does it say in the FARs that owners and operators are primarily responsible for the airworthiness of the aircraft?? Few mechanics can answer that question correctly.

The correct answer to the question, I say in my best bureaucratic voice, is found in Part 91, Subpart E, Maintenance, preventive maintenance and alterations, section 91. 403 (a) General. Then I go on to tell them that Part 91 Subpart E has 12 individual rules or sections that pertain to maintenance and then I start on a three-hour, mind-numbing lecture that covers all of Subpart E of Part 91.

This article will cover only the first four rules of the subpart. It is my hope that I might provide an insight or two into this subpart and perhaps even encourage one or two of you to take on the task of actually reading the rest of the rules in Subpart E.

Before we get into it, there are two concepts I need you to understand. First, Part 91 is talking only to the owner/operator responsibilities for performing maintenance, not mechanics. So why involve mechanics? Because more often than not, a mechanic, acting as the owner?s agent will be doing the scheduling, inspections, and record keeping required by this subpart. So, in order to keep the owner out of trouble, mechanics need to know these rules.

Second item. Part 91 is an ?operating? based rule, unlike Part 43, which is a ?performance based rule.? This operating and performance concept is the major difference between the two rules. Allow me to take a shot at explaining this. If you performed an unairworthy repair on an aircraft and signed it off as required by Part 43 section 43.9 and the aircraft never flew, a FAA inspector can write a violation against you for the bad repair. To get a violation written against an owner/operator for not complying with a Part 91 Sub-Part E rule, the aircraft had to be operated for the violation to happen. For example if the annual is pass due by five years and the aircraft never is operated, then no violation has occurred under this Subpart.

With that said, let us press on.

Section 91. 401 Applicability. In this su bpart sub paragraph (a) prescribes the rules governing the maintenance, preventive maintenance, and alterations of U.S registered aircraft operating in or outside the United States. Note again the use of the word ?operating,? as in ?world wide.? The rest of this section?s sub paragraphs (b) and (c) grants relief to Part 121, 125, 129 and 135 operators from certain sections of the Subpart because of the different maintenance program, those operators are required to be under.

Section 91. 403 General. Sub paragraph (a) very clearly states that the owner or operator is primarily responsible for maintaining the aircraft in an airworthy condition of the aircraft including compliance with Part 39, Airworthiness Directives, of this chapter. While the owner or operator is primarily responsible by this rule it does not relieve the pilot from the responsibility of determining the airworthiness of the aircraft prior to and during a flight (Ref: Section 91.7) or a mechanic from performing airworthy repairs (Ref: Section 43.13).

Sub paragraph (b) starts with: No person may perform maintenance, preventive maintenance or alterations on an aircraft other than as prescribed in this subpart and other applicable regulations including Part 43 of this chapter. This is a clarifying statement that says all applicable rules apply and reinforces paragraph (a). Government lawyers do this all the time to prevent confusion and possible conflict between different Parts or sections. They are not always successful.

Sub paragraph (c) says any aircraft with maintenance manual and a set of airworthiness limitations, those airworthiness limitations such as replacement times are mandatory unless superceded by alternative maintenance and inspections requirements on the operating specifications of Part 121 or 135 operator or an inspection program under section 91.409(e). This exception gives the air carriers some wiggle room to adjust the life limit items based on their data driven reliability programs.

Section 91.405 Maintenance required: Sub paragraph (a) says: Owner or operator shall have their aircraft inspected and have discrepancies repaired in accordance with Part 43. Again, there is an exception built into the rule for those inoperative items under sub paragraph (c) that allows those items to remain in an inoperative status and the aircraft can still be flown legally. A few decades ago when I could part my hair, this rule was more absolute. Back then; no aircraft could fly with inoperative equipment on board. This was changed about 10 years ago to grant some relief. I will talk more about it in sub paragraph (c).

Sub paragraph (b) states that the owner/operator shall ensure that maintenance personnel make appropriate entries and approve the work for return to service. This is a good example of parallel rule making. As a mechanic, Part 43, sections 43.9 and 43.11 require you to make maintenance entries. So in an effort to make sure these records are made, the drafters of this Subpart made the owner/operator responsible for checking the mechanic so that he made the entries in the logbook that he is required to make by another rule. Trusting souls weren?t they.

Sub paragraph (c) states the owner/operator shall have any inoperative instrument or item of equipment permitted to be inoperative by section 91.213(d)(2) to be repaired, replaced, removed, or inspected at the next required inspection. Section 91.213 inoperative instruments and equipment allows aircraft without a minimum equipment list to fly with inoperative instruments or equipment on board only if they are not part of the required VFR-day type certificated instruments/equipment, or required by any other rule.

For example, a rotating beacon on a PA 28-140 no longer rotates. That inoperative beacon can remain on the aircraft for years because a rotating beacon is not required for day VFR operation. However, please remember that this is not a one-time inspection. At each required inspection you must inspect the beacon and check that it is in compliance with Section 91.213. Then you must sign off that Section 91.213 inspection in the logbook for as long as that inoperative beacon is on the aircraft. For additional information on Section 91.213 is found in AC 91.67.

Paragraph (d) says the owner or operator must ensure that a placard be installed for all inoperative equipment as required by section 43.11. All this means that in our previous example the rotating beacon on/off switch must be placarded ?INOP?. In some cases the beacon?s circuit breaker is collared. All these precautions notify the pilot that the aircraft is not legal for night VFR flights.

Section 91.407. Operation after maintenance, preventive maintenance, rebuilding or alteration. Sub paragraph (a)(1) of this rule requires the owner/operator to have an approval for return to service statement in the logbook prior to flight. Sub paragraphs (a)(2) require a maintenance entry in accordance with Part 43.9 and 43.11. So far sub paragraphs (1) and (2) are just a rehash of the requirements under sections 91.403 and 91.405. It?s sort of like being trapped in a regulatory cul-de-sac.

Sub paragraph (b) is important. This paragraph requires an aircraft to undergo a test flight if it has been maintained, rebuilt, or altered in a manner that might appreciably change its flight characteristics or substantially affect its operation. The test flight has to be performed by an appropriately rated pilot with at least a private pilot certificate. After the flight, the pilot must record the flight in the logbook and state that the aircraft is operational and safe to fly.

Now a couple of comments. Part 61 is a little vague on how qualified a pilot has to be to fly. That?s a little scary especially if you just installed a STOL kit on a Cessna 180 and the check pilot wannabee had three hours total time in a tail dragger and when you talk to him he has funny little lights behind his eyes. So, ask the pilot for his pilot certificate and logbook and check him out before sending him off to test your handiwork. Also, before the engine is started make sure that you have recorded all the work that you have performed in both the logbook and a Form 337 as applicable. Make sure that you stated in the aircraft records that you are approving the work performed for return to service. In the same entry state that before the aircraft is returned to service an ?operational? test flight of the aircraft must be performed in accordance with section 91.407(b). An operational check/test flight means that the aircraft should be tested at all applicable speeds, weights, CG ranges, and maneuvers, and then the aircraft is signed off by the check pilot as being safe to operate within its operational envelope. This two-step approach is required because legally when maintenance is performed that affects the operation of the aircraft, it is a mechanic who, ?approves an aircraft for return to service,? but it is the pilot who, ?returns the aircraft to service.?

Sub paragraph (c) is what I call a by-the-way statement. This sub paragraph says that the aircraft does not have to be test flown if the work performed is tested, inspected, and both show conclusively that the maintenance performed did not change or alter the flight characteristics or flight operation of the aircraft. For example you changed all the tires on a PA-28R-200, you did a gear swing and the tires did not stick in the wheel wells. Life is good and based on the gear swing, no operational test flight is required.

We are almost done. Just to ensure that you can remember what rule in Subpart E talks to ?primarily responsible,? the next time I stand in front of you, I will ask those two questions and I will give a one U.S dollar, right out of my own pocket to the first mechanic who says ?Owner/operator and Section 91.403 (a).?

About the Author

Bill O'Brien