June 2005-
If you are an airplane owner, you undoubtedly already know what an AD is. Airworthiness Directives are issued by the FAA to address mechanical safety of flight issues that become evident in the field after an aircraft has been produced and delivered to the customer. The document itself is mailed to the owner of every registered aircraft that may be affected by the AD.
Sometimes an AD may require nothing more than the addition of a placard to the aircraft; other times it may require that the entire engine be torn down. Most of the time, the owner is not a mechanic and simply passes the information on to his/her AMT (aircraft maintenance technician) at annual time.
Some ADs are of the emergency type, requiring action prior to the next flight and can’t wait for the next service event. Others may need to be performed in a specified time interval like the next 25 hours or at the next oil change or within 100 hours or the next annual inspection (the same can be said of mandatory Service Bulletins).
There is also a type of AD called a recurring AD. This is a maintenance procedure that must be performed repeatedly at specified intervals or until a permanent fix is accomplished, if an approved permanent fix exists.
It is valuable for the aircraft owner to know and understand just exactly what is required for compliance with a specific AD, especially a recurring AD because it inevitably will cost you, the owner, money.
Sometimes the least expensive way to comply with a recurring AD is more expensive in the long run. If you plan to keep an aircraft for a long time, then permanently addressing an AD may be a better financial choice than the recurring solution. Complex ADs that have permanent solutions which go unaddressed will also affect the sale price of your aircraft when you sell it.
A perfect example of a recurring AD that has multiple methods of compliance is AD 98-04-07. This particular directive affects thousands of retractable gear Piper aircraft. The root problem is a landing gear side brace stud. This particular part is a machined bolt.
Apparently, several have failed due to cracking on a machine line causing the landing gear to collapse. The original part was 9/16” in diameter. The AD requires that after every 500 hours of airframe time, you must remove this stud and have it subjected to NDT (Non-Destructive Testing) to see if it is cracked.
If no cracks are found you can return the part to service. If it is cracked, then you must replace it.
But you can no longer buy another 9/16” stud. The new replacement part is 5/8” in diameter, so the bushings that the stud fits into must be removed and line bored to accept the larger diameter stud. That new part costs $210, and of course there would be two of them, one for the left side and one for the right—$420 in parts alone.
To NDT the existing stud, you will pay about $25 each. Then you need to consider the physical act of removing the stud in the first place. It is held in a cast housing attached to the front of the main spar. It takes two people an hour to get the housing off and another hour to get it back on, again, times two sides.
I don’t know what your local shop labor rate is but here in South Florida it is in the $60 per hour range. So figure another $240 in labor, on and off.
Once the housing has been removed and the stud extracted to be either NDT’d or replaced, you can assess the condition of the bushings inside the housing. On my airplane, I needed to replace two of the four at a cost of $50 each, plus freight.
Upon receipt of the new bushing, they needed to be line bored in the housing (as per the text of the AD) and that cost another $90 from the local machine shop.
So, here is my choice: Permanently comply with the AD and eliminate the 500-hour inspections for an additional 420 bucks, or do it all again in 500 hours.
At this point you need to consider your aircraft use. If you fly less than 100 hours a year, and plan to keep the plane for a while, it just doesn’t make financial sense to spend the money if the existing part is serviceable. If on the other hand, you fly more than 100 hours a year, this AD will need to be addressed again in a time frame of less than five years and you might want to consider permanently complying with the AD.
Since you have to remove the old part to do the recurring inspection, the labor cost will be the same if you choose to permanently comply with the AD or do the recurring inspection. As you can see, labor makes up a sizeable portion of the cost and sometimes it is in the best interest of the aircraft owner to be proactive about impending ADs, particularly if you are going to have the aircraft apart to comply with an existing AD.
But how do you know if there is an impending AD on your aircraft? You can look it up on the web for free at https://dms.dot.gov/. The procedure for creating a new AD is called NPRM, (Notice of Proposed Rule Making) and you can read the NPRM before it actually becomes an AD.
Many times these are amendments to existing ADs. An example of this is an NPRM that has been published to amend an existing AD 93-24-14. This AD addresses a mandatory bolt replacement in the nose gear of the same retractable gear Pipers that are affected by the main gear side brace pin inspection described earlier. It is required every 500 hours.
In the current AD, you are required to replace the bolt, nut and washers that attach the upper drag link to the lower drag link. No big deal really, about ten bucks in parts. But the new NPRM requires yet another replacement of the bolt that attaches the upper drag link to the collar on the landing gear. Again, just another $15 in parts.
Now, this is not an AD yet, but it will be soon. Since you already have the airplane apart and on jacks to do the original AD, you might as well have your mechanic change the upper bolts as well. Then when it does become an AD, the only work required is a logbook endorsement confirming compliance. The cost savings is in the labor to put the aircraft on jacks, and then take the airplane apart to get to the bolts in the first place.
Another recurring AD that affects a lot of aircraft is the Bendix magneto impulse coupling AD. Every 500 hours the affected magnetos need to be visually inspected to see if the little rivet that holds the impulse coupling to the fly weight has come loose or fallen off. I know some mechanics have performed this inspection while the mag is on the aircraft, but if you read the text of the AD it specifies that you take it off.
If you find nothing wrong with the impulse coupling, then you can reinstall the magneto for another 500 hours. When I do this AD I take the opportunity to change the points and condenser and have the cam lubricated, in other words, general magneto maintenance, since I had it off anyway. Total cost about $45 per mag plus one hour labor, on and off.
You could replace the Bendix mags with Slick mags that are unaffected by that AD for an exchange cost of $380 per side, but if the Bendix mags are in good shape and have low times, I generally opt to do the inspection, and do it again in 500 hours.
Now let’s discuss Service Bulletins. They come in two flavors, regular and mandatory. They are issued by the manufacturer of the component, but are usually accompanied by a Special Airworthiness Information Bulletin (SAIB) from the FAA.
If you think you don’t have to comply with these because your aircraft is for private (read non-commercial) use, you are wrong. Mandatory SBs are just that, mandatory. Compliance with SBs is a gray area, but I can tell you that if you were to have an insurance claim, then it would become black and white.
For example, I received a mandatory Service Bulletin from Lycoming last week for fuel pumps manufactured between Oct.1, 2001 and Feb. 2, 2004. It doesn’t affect my engine because my pump was manufactured in 1998, but I will still put a logbook entry in the aircraft records stating compliance by date of manufacture just to be sure.
If in fact I had replaced the fuel pump anytime in that time frame, I would need to go back to verify the part number of the pump installed and if it is the same as the one in the SB I would have had to replace it prior to the next flight.
Sometimes you will receive an SAIB from the FAA, and receive nothing from the manufacturer. The SAIB will refer you to a manufacturer’s Service Bulletin. In this example, CE-5-42 that was issued on March 18, 2005, the SAIB refers you to a manufacturers Service bulletin dated October 2003.
You would think that all affected aircraft would have been serviced by now but the FAA has issued this for a reason. This particular SAIB addresses landing gear actuators on M-20 series aircraft. In the text of the manufacturer’s instructions it specifically states it is “to be completed before next flight.” So while the FAA doesn’t consider an SAIB mandatory, the manufacturers do.
In this case, the landing gear actuator fails and you can neither extend nor retract the landing gear. You would probably want to have that fixed. I’m sure that your insurance carrier will consider the aircraft unairworthy, thus voiding the insurance if you don’t comply with the SBs.
The bottom line here is this: though you depend heavily on the advice of your trusted mechanic, it is in the owner’s best interest to read and understand the context of the ADs that affect the airplane you own or want to own, so you can make quality decisions about how best to comply with them.
Michael Leighton is a 3,400 + CFIIMEI/ATP as well as an A&P mechanic and former FAA Accident Prevention Counselor. He operates an air charter company in South Florida. You can reach him via e-mail at av8tor0414@aol.com.
