MINIMUM EQUIPMENT LIST
A helicopter operating under Part 135 with certain installed equipment inoperative is prohibited from taking off unless the operation is authorized in the approved MEL. The MEL provides for some equipment to be inoperative if certain conditions are met [Figure 7-6 on page 7-7]. In many cases, a helicopter configured for single-pilot IFR may depart IFR with certain equipment inoperative, provided a crew of two pilots is used. Under Part 91, a pilot may defer certain items without an MEL if those items are not required by the type certificate, CFRs, or airworthiness directives (ADs), and the flight can be performed safely without them. If the item is disabled, or removed, or marked inoperative, a logbook entry is made.

PILOT PROFICIENCY
Helicopters of the same make and model may have variations in installed avionics that change the required equipment or the level of augmentation for a particular operation. The complexity of modern AFCS, AP, and FD systems requires a high degree of understanding to safely and efficiently control the helicopter in IFR operations. Formal training in the use of these systems is highly recommended for all pilots.

During flight operations, you must be aware of the mode of operation of the augmentation system, and the control logic and functions employed. For example, during an ILS approach using a particular system in the three-cue mode (lateral, vertical, and collective cues), the flight director collective cue responds to glide slope deviation, while the horizontal bar of the “cross-pointer” responds to airspeed deviations. The same system, while flying an ILS in the two-cue mode, provides for the horizontal bar to respond to glide slope deviations. This concern is particularly significant when the crew consists of two pilots. Pilots should establish a set of procedures and division of responsibility for the control of flight director/autopilot and FMS modes for the various phases of flight. Not only is a full understanding of the system modes essential in order to provide for a high degree of accuracy in control of the helicopter, it is the basis for identification of system failures