SUPPLEMENTAL TYPE CERTIFICATE?
The minimum equipment list with its attached "letter of authorization" is, as stated, a supplemental type certificate by definition and therefore takes care of revalidating the original type certificate. Is this magic or what? But wait; pity the poor technician who is unfamiliar with such things and who releases an aircraft for flight with some item that does not work, like a heater, radio, generator, etc., and who fails to properly MEL the item or defer the item in the aircraft records. Civil penalties and certificate actions are commonplace where confusion and outright ignorance of MEL instructions are found by FAA inspectors. Technicians who work in the air carrier arena and those in a turbine aircraft Part 91 setting have to be familiar with the rules that surround the application of the minimum equipment lists for the aircraft they work on.
A common example was described to me just recently. A technician could not locate a replacement flap motor for his Cessna twin used by a medevac company. The technician knew the aircraft could fly perfectly well without operating flaps and indeed were not required for takeoff at all. He informed the pilot that the flaps were inoperative and that he would replace the motor in a day or so when it arrived from a parts source. This seemed to satisfy the pilot. The technician noted in the maintenance record, however, that the flaps needed a new motor and were inoperative. He said nothing about the aircraft being grounded. After an inspector did a routine check of the records he noted the discrepancy and violated the air carrier, pilot, and technician. Use of flaps is a recommended procedure in the factory handbook and flaps are required for landing. The conclusion is that without its flaps working, the aircraft was no longer airworthy simply because it did not conform to its type certificate. The technician was embarrassed for not grounding the aircraft and the pilot was educated regarding equipment that had to work before flight. The air carrier paid a fine. Needless to say, the pilot will now make sure there is a copy of the MEL aboard the aircraft at all times.
The FARs refer to the need for an MEL in Parts 91.213, 121.628, and 135.179. These sections provide that you can't fly legally when the aircraft has any equipment that is inoperative. The sections go on to list exceptions which include the use of an approved MEL. Even though the aircraft is technically unairworthy, if you have an approved MEL document for the aircraft, magic makes it airworthy! There are other exceptions to the rule. FAR 91.213 for example provides exceptions for helicopters and piston powered airplanes and gliders for which a master minimum equipment list has not yet been developed. Another exception common to all the FAR sections is of course the ferry permit or special flight permit described in FAR 21.197 and 21.199. A recent bulletin from FAA referring to air carrier manual requirements cites the need for inspectors to pay particular attention to MEL instructions concerning minimum equipment list conditions and limitations. (See HBAT 98-18, dated 4-28-98.) This is a fertile area for technicians and pilots to pick up FAR violations when they use the MEL. The bulletin cites the need to include additional instruction, necessary to clarify actions taken under particular situations and conditions regarding the MEL. Contact your local PMI for data concerning this recent additional concern for inspectors and technicians.
As a final note, it is interesting to observe that the current controversy over "Instructions for Continued Airworthiness" (see Flight Standards Bulletin FSAW 98-03) as it relates to Field Approvals via 337 forms, sounds very similar to what occurred when regulatory compliance was applied to the MEL. Apparently, now the FAA wizards have divined that all 337 applications must have instructions and may include a manual or other form of instruction. The rub is that some FSDOs maintain that they can't approve these instructions. They say it takes FAA engineering to do the job at an FAA Aircraft Certification Office (ACO).
The problem is that it takes about a year to get such things through the ACOs. Oh well, there goes the field approval process! Some suggest that avoidance of field approvals is the real reason for the change. It never ceases to amaze some folks how FAA keeps attempting to fix something that really ain't broke! (For further information on this issue see FSAW 98-03, dated 1-30-98.)
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