follows assumes that the pilot wishes to defer mainte- nance that would ordinarily be required prior to flight. Using the deferral provision of section 91.213(d), the pilot determines whether the inoperative equipment is required by type design, the CFRs, or ADs. If the inop- erative item is not required, and the helicopter can be safely operated without it, the deferral may be made. The inoperative item shall be deactivated or removed and an INOPERATIVE placard placed near the appropriate switch, control, or indicator. If deactivation or removal involves maintenance (removal always will), it must be accomplished by certificated maintenance personnel. For example, if the position lights (installed equipment) were discovered to be inoperative prior to a daytime flight, the pilot would follow the requirements of sec- tion 91.213(d). The deactivation may be a process as simple as the pilot positioning a circuit breaker to the OFF position, or as complex as rendering instruments or equipment totally inoperable. Complex maintenance tasks require a cer- tificated and appropriately rated maintenance person to perform the deactivation. In all cases, the item or equip- ment must be placarded INOPERATIVE. All rotorcraft operated under part 91 are eligible to use the maintenance deferral provisions of section 91.213(d). However, once an operator requests an MEL, and a Letter of Authorization (LOA) is issued by the FAA, then the use of the MEL becomes mandatory for that helicopter. All maintenance deferrals must be accomplished in accordance with the terms and conditions of the MEL and the operator-generated procedures document. The use of an MEL for rotorcraft operated under part 91 also allows for the deferral of inoperative items or equipment. The primary guidance becomes the FAA- approved MEL issued to that specific operator and  N-numbered helicopter. The FAA has developed master minimum equipment lists (MMELs) for rotorcraft in current use. Upon writ- ten request by a rotorcraft operator, the local FAA Flight Standards District Office (FSDO) may issue the appro- priate make and model MMEL, along with an LOA, and the preamble. The operator then develops operations and maintenance (O&M) procedures from the MMEL. This MMEL with O&M procedures now becomes the operator's MEL. The MEL, LOA, preamble, and proce- dures document developed by the operator must be on board the helicopter when it is operated. The FAA considers an approved MEL to be a supple- mental type certificate (STC) issued to an aircraft by serial number and registration number. It therefore becomes the authority to operate that aircraft in a condi- tion other than originally type certificated. With an approved MEL, if the position lights were dis- covered inoperative prior to a daytime flight, the pilot would make an entry in the maintenance record or dis- crepancy record provided for that purpose. The item is then either repaired or deferred in accordance with the MEL. Upon confirming that daytime flight with inopera- tive position lights is acceptable in accordance with the provisions of the MEL, the pilot would leave the position lights switch OFF, open the circuit breaker (or whatever action is called for in the procedures document), and plac- ard the position light switch as INOPERATIVE. There are exceptions to the use of the MEL for deferral. For example, should a component fail that is not listed in the MEL as deferrable (the rotor tachometer, engine tachometer, or cyclic trim, for example), then repairs are required to be performed prior to departure. If main- tenance or parts are not readily available at that  location, a special flight permit can be obtained from the nearest FSDO. This permit allows the helicopter to be flown to another location for maintenance. This allows an aircraft that may not currently meet applica- ble airworthiness requirements, but is capable of safe flight, to be operated under the restrictive special terms and conditions attached to the special flight permit. Deferral of maintenance is not to be taken lightly, and due consideration should be given to the effect an inop- erative component may have on the operation of a  helicopter, particularly if other items are inoperative. Further information regarding MELs and operations with inoperative equipment can be found in AC 91-67, Minimum Equipment Requirements for General Aviation Operations Under FAR Part 91. During the engine start, rotor engagement, and systems ground check, use the manufacturer’s checklists. If a problem arises, have it checked before continuing. Prior to performing these tasks, however, make sure the area near the helicopter is clear of personnel and equipment. Helicopters are safe and efficient flying machines as long as they are operated within the parameters established by the manufacturer. The exposed nature of the main and tail rotors deserve special caution. You must exercise extreme care when taxiing near hangars or obstructions since the distance between the rotor blade tips and obstructions is very difficult to judge. [Figure 9-1] In addition, you cannot see the tail rotor of some helicopters from the cabin. Therefore, when hovering backwards or turning in those helicopters, allow plenty of room for tail rotor clearance. It is a good practice to glance over your shoulder to maintain this clearance. ENGINE START  AND ROTOR ENGAGEMENT ROTOR SAFETY CONSIDERATIONS 9-2