September 2004 –
Only big airplanes with jet engines have to worry about replacing things on a calendar or time in service basis. None of that applies to my airplane, or does it?
We all know that transport airplanes have to change landing gear, and starters, and engine components and many other components on a time table that is based on time the component has been in service, not the condition of the component.
The selection of what is on these time life lists is made during the certification of the aircraft, and sometimes items are added from service history of the aircraft. The time specified can be changed either up or down using the service history and some operators have different service times because of their specific maintenance history… The intention of imposing time life limits on some components is to improve reliability and safety of the aircraft by changing/overhauling components before they fail and cause a potential problem.
A lot of the airplanes that come to mind when we think of time life requirements are operated under FAR 121, 135, or 125, and are issued Operation Specifications by the FAA that can contain requirements for time limited equipment in addition to those time life items that are specified by the manufacturers and normally published in chapter five of the maintenance manual for the aircraft. Instructions for continued airworthiness will also add to the list. Our small airplanes are generally operated under FAR 91.
Maintenance requirements for airplanes operated under FAR 91 are generally found in Subpart E of Part 91. Inspection requirements are found in Subpart E generally 91.409, and section (e) of that regulation requires turbine multi-engine aircraft or turbine rotorcraft use time life limits as specified.
FAR part 43 (maintenance, preventative maintenance, alterations and rebuilding) is specifically referenced in subpart E frequently, for guidance of who can return an aircraft to service after maintenance, specific items to be inspected during an annual inspection, and other items dealing with maintenance and inspection.
91.403 states “the owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition including compliance with part 39.” Part 39 is the chapter that deals with Airworthiness Directives.
So now we know it is our responsibility to have ADs complied with and to maintain the airplane in an airworthy condition. Remember this the next time you leave it to the mechanic to check for airworthiness directives that may be due to your airplane. 43.13 (a) requires the mechanic to use the current manufacturer’s maintenance manual, or instructions for continued airworthiness, or “other methods, techniques, and practices acceptable to the Administrator, except as noted in §43.16”.
43.16 states that any inspection or maintenance specified in an airworthiness limitation section of the manufacturer’s maintenance manual or instructions for continued airworthiness will be complied with.
Most of the small airplanes in service do not have an airworthiness limitation section, or time life section in the maintenance manual. I would suggest that you check the maintenance manual for your specific aircraft to see if a time life or airworthiness limitation section is part of the manual and make your own decision.
The maintenance manual for 1996 or later 172s does have a component time limit section in chapter five. It contains time life limitations on seat belts, mixture and throttle cables, air filters, hoses and other items. This section also deals with vendor established time limits, which references you back to the individual component manuals, and service bulletins for times. The magnetos and engine both are specifically listed in this section.
43.13 requires the use of the maintenance manual, and the maintenance manual has a time life limit section, this section references Textron/Lycoming Service Instruction SI 1009AJ, or latest revision, which specifies time before overhaul (TBO) times. The maintenance manual for 1977 through 1986 aircraft has component time limits listed in section two, Ground Handling, Servicing, Cleaning, Lubrication and Inspection.
There are also time limits listed in this section for other items such as hoses, and a reference to manufacturer’s manuals and service bulletins for other time life items, but they are not listed in a chapter titled Time Life Limitations.
The difference in location of this information in the manuals is primarily from Cessna switching to the Air Transport Association format for manuals that allow a standard method of information publication between manufacturers making finding information much easier for everyone, as specific information is found in specific areas of all manuals.
A lot of the aircraft in service today were originally certified before the FAA was in existence and are certified to standards of CAR 3 (Civil Aviation Regulation 3). Newer aircraft are certified to FAR Part 23, which is the FAA version of CAR 3.
CAR 3 was written for the certification of Piper J-3 cubs and other aircraft of that vintage and did not address many of the concerns we have today. FAR 23 is current and is constantly updated for the latest regulations and procedures.
Instructions for Continued Airworthiness were not specifically addressed in CAR 3, but Appendix G to Part 23 specifically addresses “Instruction for Continued Airworthiness” and requires a manufacturer to establish and publish instructions for continued airworthiness, and section G23.4 requires an airworthiness limitations section.
If you have had some new equipment installed on your aircraft that required a Supplemental Type Certificate (STC) you probably have a flight manual supplement that contains instructions for continue airworthiness. These instructions are mandatory as per FAR 43.16 and could range from no additional maintenance required or be quite intensive depending on what the manufacturer deemed necessary and what the FAA required as part of the STC.
What does this all mean to you? If your aircraft was certified under CAR 3, and has no modifications that require instructions for continued airworthiness you probably have no legal requirement to comply with time life items. If you have an aircraft certified under FAR 23, you may. If you have modifications that contain “Instructions for Continued Airworthiness” you may.
Let’s look at this from a different angle. The manufacturer has established a time limit using service history and experience. Certainly lawsuits have had an effect on the manufacturer’s decision regarding these issues, but it is still in their best interest to provide the most useful time in service possible, within guidelines of reliability and safety.
The manufacturer wants the customer (aircraft owner) trouble free use of the product for the longest possible time; you, the aircraft owner want trouble free, reliable service life from the aircraft for the least possible money. You both want the same thing.
Trying to stretch the time on a piece of equipment could quite possible end up with a missed trip, or an equipment breakdown away from base stranding you somewhere on Saturday morning with no mechanic available, and your wife has dinner plans 200 miles away in four hours. Talk about stress.
If you decide to sell your aircraft a potential purchaser is going to deduct from the purchase price for items that are considered past their service life and if there are many of these items may question if the aircraft has in fact been well maintained. At best you get less money for your aircraft and at worst lose a sale.
The worst case possible is to have an accident and try to convince a jury that it was prudent to ignore the recommendation of the manufacturer to replace/overhaul something because there was no legal requirement. An extra one or two hundred hours past TBO on the engine might not have saved you any money in this case.
It would seem the wise thing to do is follow the manufacturer recommendations on things that are shown as time life components and equipment and enjoy the satisfaction of improved service life, higher resale value, and knowing that you are maintaining your aircraft in the best possible manner, probably with the least amount of stress.
