During testing for helicopter holding, the optimum  airspeed and leg length combination was determined to  be 90 KIAS with a 3 NM outbound leg length. Consideration  was given to the wind drift on the dead reckoning entry  leg at slower speeds, the turn radius at faster airspeeds,  and the ability of the helicopter in strong wind conditions  to intercept the inbound course prior to the holding fix.  The published minimums are to be used with no visibility  reductions allowed. Figure 7-11 is an example of a Copter  GPS PinS approach that allows the helicopter to fly VFR  from the MAP to the heliport.  The final and missed approach protected airspace providing  obstacle and terrain avoidance is based on 70 KIAS, with  a maximum 10-knot tailwind component. It is absolutely  essential that pilots adhere to the 70 KIAS limitation  in procedures that include an immediate climbing  and turning missed approach. Exceeding the airspeed  restriction increases the turning radius significantly and  can cause the helicopter to leave the missed approach  protected airspace. This may result in controlled flight into  terrain (CFIT) or obstacles.  If a helicopter has a V$_{MINI}$ greater than 70 knots, then  it is not capable of conducting this type of approach.  Similarly, if the autopilot in “go-around” mode climbs at a  V$_{YI }$greater than 70 knots, then that mode cannot be used.  It is the responsibility of the pilot to determine compliance  with missed approach climb gradient requirements  when operating at speeds other than V$_{Y}$ or V$_{YI}$. Missed  approaches that specify an “IMMEDIATE CLIMBING TURN”  have no provision for a straight ahead climbing segment  before turning. A straight segment results in exceeding the  protected airspace limits.  Protected obstacle clearance areas and surfaces for the  missed approach are established on the assumption that  the missed approach is initiated at the DA point and for  non-precision approaches no lower than the MDA at the  MAP (normally at the threshold of the approach end of  the runway). The pilot must begin the missed approach at  those points. Flying beyond either point before beginning  the missed approach results in flying below the protected  obstacle clearance surface (OCS) and can result in a collision  with an obstacle.  The missed approach segment U.S. Standard for Terminal  Instrument Procedures (TERPS) criteria for all Copter  approaches take advantage of the helicopter’s climb  capabilities at slow airspeeds, resulting in high climb  gradients. [Figure 7-12] The OCS used to evaluate the  missed approach is a 20:1 inclined plane. This surface is  twice as steep for the helicopter as the OCS used to evaluate  the airplane missed approach segment. The helicopter  climb gradient is, therefore, required to be double that of  the airplane’s required missed approach climb gradient.  A minimum climb gradient of at least 400 ft/NM is required  unless a higher gradient is published on the approach  chart (e.g., a helicopter with a ground speed of 70 knots  is required to climb at a rate of 467 fpm (467 fpm = 70  KIAS × 400 feet per NM/60 seconds)). The advantage of  using the 20:1 OCS for the helicopter missed approach  400 feet/NM (standard)  200 feet/NM (standard) 20:1 OC S  40:1 OC S  20:1 versus 40:1 Obstacle clearance surface (OCS) for nonprecision missed approach procedures  MAP  96 feet/NM  48 feet/NM  The Copter 20:1 OCS provides for a lower MDA for the helicopter than for the airplane if the controlling  obstacle is in the missed approach area. A climb gradient of 400 feet/NM will allow a required  obstacle clearance (ROC) of 96 feet/NM for each NM of flightpath.  Figure 7-12. Obstacle clearance surface (OCS).  7-13 