The Anatomy of an AD
Does it apply? Is it signed off?
By Joe Hertzler
Determining whether an airworthiness directive (AD) applies to your aircraft or not seems pretty straightforward in most cases. However, what we have found is that applicability can mean one thing to one person and something different to another.
ADs are regulations
An AD is issued as a result of an unsafe condition having been uncovered. This can be a result of the manufacturer of the aircraft having determined that an unsafe condition exists. When the manufacturer discovers such a situation it will issue a service bulletin of some sort (service information) and then ask the FAA to consider issuing an AD for the problem being corrected by the service information document. Other triggering events for an AD can be an accident investigation or an unapproved parts discovery.
What some do not understand is that all ADs are regulations. Whenever an AD is issued, 14 CFR Part 39 of the code of federal regulations is amended and that AD becomes a rule itself. Part 39.3 defines airworthiness directives as follows: FAA's airworthiness directives are legally enforceable rules that apply to the following products: aircraft, aircraft engines, propellers, and appliances.
The AD contents
Basically each AD has three parts: 1) the applicability statement; 2) the body; and 3) the closing statements (aircraft movement, alternate means of compliance and effective date statements). Since ADs are "legally enforceable rules," each AD must clearly define what it applies to in order for the industry to understand its impact and act upon its direction. This is done through the applicability statement. Because different persons who are inconsistent in their approach toward applicability write ADs and each AD addresses a completely different safety concern it can be confusing to the reader who wants to determine if the AD applies to his or her aircraft. Following are some applicability examples with explanations:
2003-19-11 Learjet: Amendment 39-13314. Docket 2000-NM-408-AD. Supersedes AD 95-14-09, Amendment 39-9303.
Applicability: Model 60 airplanes, serial numbers 60-001 through 60-145 inclusive, certificated in any category . . .
AD 2003-19-11's applicability statement includes the aircraft serial number and is clear as to exactly which aircraft the AD applies to.
89-22-14 Beech: Amendment 39-6357. Applicability: 90, 200, and 300 series airplanes (all serial numbers) certificated in any category.
Compliance: Required within the next 100 hours time-in-service after the effective date of this AD, unless already accomplished.
To prevent possible aileron flutter, accomplish the following:
(a) For Models C90A (S/N LJ-1132 through LJ-1167), B200 (S/N BB-1246 through BB-1285 except BB-1272), 300 (S/N FA-91 through FA-140 except FA-120 and FA-128), A200CT (S/N BP-59 through BP-63), and B200C (S/N BP-64 through BP-66 and BV-1 through BV-8), inspect each aileron using the tap procedure in Beech Service Bulletin No. 2256, dated November 1988. If this inspection shows the presence of foam, prior to further flight remove the foam in accordance with the procedures in the above Service Bulletin.
(b) For all other affected airplanes, check the airplane records to determine if any aileron has been replaced for any reason subsequent to Jan. 1, 1985. If so, inspect the aileron using the tap procedure in Beech Service Bulletin No. 2256. If this inspection shows the presence of foam, prior to further flight remove the foam in accordance with the procedures in the above Service Bulletin . . .
These few examples in no way encompass all types of AD applicably statements but you can see that there are several ways that the FAA uses to tell us what an AD applies to. In all cases, the applicability starts in the ADs' applicability statement.
The body of the AD is what makes up the majority of the document. It is the body that describes what needs to be done in order to comply with the AD. In many cases the body of the AD refers to a service instruction from the manufacturer and the content in that service instruction provides step-by-step instructions for compliance. The body of the AD will also tell us what conditions, if any, will cause the AD to be recurring, meaning that recurring inspections or tests are required on a scheduled basis (i.e. every X hours, X cycles, or X months, etc.).
The closing statements of the AD should not be overlooked. They will let you know if the aircraft can be moved by means of a special flight permit (ferry permit) in order to comply with the AD, whether or not an alternate means of compliance is possible, and exactly when the AD becomes effective.
NOTE: You need to know that not all ADs allow an aircraft to be moved in order to comply with the AD. Because of this, anytime (as an Airframe and Powerplant mechanic) you are asked to "find the aircraft safe for the intended flight" when a special flight permit has been issued, you need to look at all ADs applicable to the aircraft and see if any exist that do not allow for a special flight permit and have not been accomplished. This AD check should be done as a part of your inspection of the aircraft.
Recording AD compliance
Now let's look at the rule that describes the record-keeping requirement for the aircraft owner as it relates to ADs.
Part 91.417 Maintenance records.
(a) Except for work performed in accordance with Secs. 91.411 and 91.413, each registered owner or operator shall keep the following records for the periods specified in paragraph (b) of this section:
(1) Records of the maintenance, preventive maintenance, and alteration and records of the 100-hour, annual, progressive, and other required or approved inspections, as appropriate, for each aircraft (including the airframe) and each engine, propeller, rotor, and appliance of an aircraft. The records must include -
(i) A description (or reference to data acceptable to the Administrator) of the work performed; and . . .
(v) The current status of applicable airworthiness directives (AD) including, for each, the method of compliance, the AD number, and revision date. If the AD involves recurring action, the time and date when the next action is required . . .
The key here is the statement "current status of applicable ADs." The key word being applicable. What this means is that if an AD exists that is applicable to your specific aircraft or any component thereof, you must have a record of the compliance for that AD. The record must include the AD number, revision date, and method of compliance. If the AD is one that requires additional or continued recurring action, you must also have recorded the time and date the next action is required. Many believe that the AD amendment number is required when in fact it is the revision date that is required. Following is an example/suggestion of a maintenance record statement that includes the required elements.
Complied with AD 82-01-05 R2, Stall Warning Accelerometer Inspection, effective 4/10/1986, by inspecting the Stall Warning Accelerometer in accordance with SB 35/36-27-12B. No defects noted at this time. Inspection due again at Acft TT 3,676.
To determine which ADs apply to your aircraft, engines, propellers, or appliances, look at the applicability statement of the AD, not the body. Make sure that all ADs that apply to your aircraft, engines, propellers, or appliances are addressed and properly signed for in the maintenance records, including the method of compliance and the effective date. Do not overlook appliance ADs. They are just as mandatory but applicability is usually more difficult to determine. For those ADs that are recurring, make sure that you know when the next action is due and understand that there are no tolerance windows for recurring ADs. They are due when they are due.
Joe Hertzler is the president of AVTRAK Inc., an Aurora, Colorado-based company helping business aircraft owners, repair stations and charter operations manage the compliance of their aircraft and/or businesses. He is an Airframe and Powerplant mechanic with Inspection Authorization and also a private pilot.