Pilot Techniques in Heavy Seas and Surf – 5 – Bracketing Lateral Speed
In the Hoist Principles post, we discussed the importance of the pilot and flight mechanic working in concert to move the helicopter the correct distance, in the necessary direction, and at the appropriate rate. Distance and direction are usually intuitive; the helicopter must be positioned in the right place for each portion of a hoist. The rate at which it moves, however, is more nuanced and situationally dependent. The following techniques provide guidance on how to assess and achieve appropriate lateral speed.
The Flight Mechanic Knows Best
The flight mechanic (FM) is the best judge of closure rate. Although the pilot’s field of view is limited, the FM can maintain continuous sight of the swimmer and survivor throughout the hoist, enabling them to manage cable at a rate commensurate with helicopter movement, monitor the effects of rotor wash, and anticipate wave impacts on the hoist. As such, the simple calls of “increase your rate,” “slow your rate,” and “rate is good” are invaluable for achieving the correct speed.
Reducing Flight Mechanic Task Saturation
That said, providing constant rate calls in addition to distance and direction while managing cable in a dynamic environment can saturate a FM. To reduce reliance on continuous rate conns and thereby lessen the burden on the FM, the pilot can use the following bracketing techniques to self-assess and maintain appropriate closure.
1. Using Wave Speed
In the surf zone, the swimmer and survivor will never move faster than the waves. Therefore, the helicopter should not need to move faster than the waves either. When keeping the swimmer and survivor in the green zone while they take white water amid a set, the helicopter’s motion should be paced no faster than the waves. Once the pilot has the swimmer and survivor in sight, they can still use the waves as a guide but should strive to maintain a consistent catenary with the FM, sliding and stopping while using the swimmer and survivor as a reference until recovery is possible.
2. Watching the Cable in Catenary
When the helicopter is positioned nose- or door-to the surf, the pilot can observe the hoist cable. When moving away from the swimmer, if the cable catenary straightens and starts to be pulled clear of the water, the helicopter’s separation from the swimmer and survivor is too rapid and closure must be slowed or stopped.
3. Establishing a Hover Bar Baseline
In heavy seas, currents often create significant relative motion between the helicopter and survivors. By trimming the aircraft when there is zero relative movement between the helicopter and the swimmer (or other reference – aeration/sea foam), the pilot can note the direction of drift and ground speed on the hover bars. If the control position for the hover bar baseline is trimmed and that force trim is maintained by the pilot it provides a valuable reference for gauging closure rates later in the evolution.
4. Relating Closure to Hoist Speed
The maximum hoist speed in the MH-60T is 250 fpm, which equates to roughly 2.5 knots. If the helicopter is moving faster than this relative to the survivor, it risks outpacing the hoist. While this is somewhat simplified—angles and cable geometry play a role—it remains a useful rule of thumb. If the swimmer and survivor are not moving, the speed of the zero relative motion drift + or – 2.5 kts helps bracket lateral speed appropriately.
5. Understanding the Impact of Vertical Movement on Lateral Stability
Finally, understanding what the FM is trying to accomplish allows the pilot to manage vertical movement in a way that supports lateral cable control. For example, if the FM is positioning the helicopter for a quick pickup ahead of a large wave face, a pilot who inadvertently descends while moving toward the swimmer and survivor impedes the FM’s ability to provide cable tension, delaying recovery. Although, ideally, the helicopter maintains a constant altitude, in this situation a slight climb is preferable to a descent. Similarly, if the FM is paying out cable to give the swimmer freedom of movement in the surf, an unintentional climb will create unwanted tension, restricting cable management. Although, ideally, the helicopter maintains constant altitude, in this case a slight descent is preferable to a a climb.