Back Shop Commercial Edition: Industry Insights

If you work for a 14 CFR 135 or 121 operator, you probably have seen the Minimum Equipment List(s) governing the equipment with which your aircraft are allowed to fly inoperative. Your Minimum Equipment List (MEL) was developed by someone in your organization or an outside consulting firm, using the FAA’s Master Minimum Equipment List as a guide.

These Master Minimum Equipment Lists (MMEL) are among the finest contributions to aviation safety ever devised. All are available at www.opspecs.com and are free.

Most MMELs were developed in the 1980s. The Flight Operations Evaluation Boards, consisting of FAA personnel, manufacturer’s representatives and operators, worked to make them usable documents when they first came out, but most meet maybe once a year now, as the aircraft mature. Their meetings generally cover new and optional equipment and deletions of some equipment now deemed critical to safe flight. They act independently from each other, which is why some include the ELT under Chapter 25 for emergency equipment, while others put the ELT in Chapter 23 for communications. Someone should be in charge of standardization, just so we all know where to look.

More importantly, since your MMEL was produced, the governing regulations might have changed. As a result, although your MEL is in conformity with the MMEL, it might not match the regulations or the manufacturer’s current maintenance practices.

One example of this is the MMEL provisions for operating the aircraft without the anti-collision system operative. Most MMELs say that if you have two systems, anticollision beacon and strobes, either one can be inoperative, but not both, if you’re operating at night. The next item, however, says that both systems may be inoperative for daylight operations. Almost all MMELs contain this or a similarly worded provision.

But here’s the rub: 14 CFR 91.209, which covers aircraft lighting, was revised in February 1996, long after your MMEL was produced, to include part (a), which covers navigation lights, and (b), which covers anti-collision lighting. Only (a) has a reference to time of day. Paragraph (b) states, "(No person may) operate an aircraft that is equipped with an anticollision light system, unless it has lighted anticollision lights. However, the anticollision lights need not be lighted when the pilot-in-command determines that, because of operating conditions, it would be in the interest of safety to turn the lights off."

Note that the regulation does not provide an exemption for maintenance conditions, nor is there any reference to time of day. This means that if an FAA inspector sees an aircraft equipped with anti-collision lighting operating without that system operable, even in daylight hours, a violation may be written, with an investigation following. If the system has been deferred as inoperative, the operator can be fined for every flight the aircraft has made since the deferral took place.

Now, when you tell the inspector that the item is properly deferred in accordance with your FAA-approved MEL, the reply you get will be that the MEL is only an advisory document and that the regulation prevails in any conflict. This will probably only happen when you are out of your local FSDO area of responsibility and can’t appeal to the manager.

In order to keep pilots from getting trapped, you need to revise your MEL Chapter 33 to eliminate the daylight exemption. Then the MEL will agree with the regulations. When you send the revision to your FSDO for approval, make note that your change is in conformity with 91.209(b) and is more restrictive than the MMEL. You might also do a maintenance record review to see if the entire system has been deferred as inoperative for daylight operation at any time since 2/96 and include all instances in a self-disclosure letter along with that application. That should cover you for any past deferrals. Otherwise those items amount to self-incrimination that could bite you at any time.

Within a year, we’ll probably see all the MMELs revised to comply with 91.209(b), but until that time, you’ll want to be proactive on the issue. It will not only cover you, but will also make you look good in the FSDOs eyes, and that never hurts.