bank angle in the Heading Select mode are significantly  more robust than in the NAV mode. Figure 7-3 represents  the bank angle and roll limits of the S76 used by the FAA for  flight testing. It has a roll rate in the Heading Select mode  of 5 degrees per second with only 1 degree per second in  the NAV mode. The bank angle in the Heading Select mode  is 20 degrees, with only 17 degrees in the NAV Change  Over mode. Furthermore, if the Airspeed Hold mode is  not selected on some autopilots when commencing the  missed approach, the helicopter accelerates in level flight  until the best rate of climb is attained, and only then will  a climb begin.  WAAS localizer performance (LP) lateral-only PinS testing  conducted in 2005 by the FAA at the William J. Hughes  Technical Center in New Jersey for helicopter PinS also  captured the flight tracks for turning missed approaches.  [Figure 7-4] The large flight tracks that resulted during  the turning missed approach were attributed in part to  operating the autopilot in the NAV mode and exceeding  the 70 KIAS limit.  A flight operated under 14 CFR Part 135 has minimums and  procedures more restrictive than a flight operated under  14 CFR Part 91. These Part 135 requirements are detailed  in their operations specifications (OpSpecs). Helicopter Air  Ambulance (HAA) operators have even more restrictive  OpSpecs. Shown in Figure 7-5 is an excerpt from an  OpSpecs detailing the minimums for precision approaches.  The inlay in Figure 7-5 shows the minimums for the ILS  Runway 3R approach at Detroit Metro Airport. With all  lighting operative, the minimums for helicopter Part 91  operations are a 200-foot ceiling, and 1,200-feet runway  visual range (RVR) - one-half airplane Category A visibility  but no less than 1⁄4 SM/1,200 RVR. However, as shown in  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  A helicopter operating under 14 CFR 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]  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 14 CFR 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,  removed, or marked inoperative, a logbook entry is made.  the OpSpecs, the minimum visibility this Part 135 operator  must adhere to is 1,600 RVR. Pilots operating under 14 CFR  Part 91 are encouraged to develop their own personal  OpSpecs based on their own equipment, training, and  experience.  MAP  1000 ft.  2000 ft.  3000 ft.  4000 ft.  5000 ft.  6000 ft.  7000 ft.  8000 ft.  Distance from MAP  × × × × × × × × × × × × Bin Mean  Bin Maximum  Approach Tracks  Legend  × Heading hold  VOR/RNAV  (Capture)  VOR/RNAV  (On Course)  Heading Select  VOR/RNAV  (Course Change  Over Station/Fix)  <6  +/–22  +/–13  +/–20  +/–17  None specified  5  1  5 VOR/RNAV Approach  5  1  Bank Angle Limit  (Degrees)  Roll Rate Limit  (Degrees/Sec)  Autopilot  Mode  SAMPLE NOT FOR ACTU AL USE Figure 7-3. Autopilot bank angle and roll rate limits for the S-76  used by the William J. Hughes Technical Center for Flight Tests.  Figure 7-4. Flight tests at the William J. Hughes Technical Center  point out the importance of airspeed control and using the correct  technique to make a turning missed approach.  Minimum Equipment List (MEL)  Operations Specifications  Pilot Proficiency  7-5 