Pilot Techniques in Heavy Seas and Surf – 4 – Horizontal Stability

In Pilot Techniques in Heavy Seas and Surf – 1, we examined the qualities of effective hoisting: responsive, smooth, stable, and appropriately assertive. In this follow-up, I want to focus on horizontal stability and share a few practical techniques that have helped me over the years. 

Because establishing a trim baseline is critical to hoist stability, I recommend first reviewing the Trim Baselines When Hoisting post if you are unfamiliar with the trim baseline concept. These tips apply not only to heavy seas and surf hoisting, but to any time the helicopter transitions from a zero-groundspeed hover, moves, and then reestablishes a hover. 

Hover References and Fixation 

When the swimmer or survivor is far enough from the aircraft to remain in the pilot’s line of sight, they provide an excellent hover reference, making horizontal stability relatively easy to maintain. But as the helicopter moves laterally and the swimmer or survivor disappears from the pilot’s view, hovering becomes more difficult. 

To avoid fixating on a single reference, which often leads to pilot-induced oscillations, the pilot, when using the swimmer or survivor as a reference, should deliberately shift their scan to secondary references, including debris, buoys, jetties, rocks, or—more commonly in open water—sea foam or aeration created by wind, waves, and breaking surf. 

The Embedded GPS/INS (EGI)-derived hover bars also provide a valuable way to augment and validate outside visual cues. 

Anticipating Reference Loss 

As the helicopter slides toward the swimmer and survivor—whether delivering the rescue device or recovering them—the pilot must anticipate losing them as a visual reference. Because clinging to the swimmer or survivor for as long as possible only to lose them during the most critical portion of the hoist is ineffective, it is incumbent on the pilot to shift more of the scan to sea foam, hover bars, and other available cues before the swimmer and survivor disappear from sight.  

Vection Awareness 

Vection, or illusory motion, is another challenge. The classic example is sitting at a stoplight when the car next to you creeps forward, tricking your brain into feeling like you are rolling backward. A similar, but more pronounced, illusion occurs when a large breaking wave dominates a pilot’s field of view, making it appear that the helicopter is sliding in the opposite direction of the whitewater. Recognizing this illusion allows the pilot to trust cyclic force trim and hover bar indications, rather than reacting to false motion cues. 

Using Post-Wave Aeration 

Fortunately, after a large breaking wave passes, the aerated water it leaves behind provides excellent short-term hover references. Just as looking beyond the swimmer ensures continuity when they leave your line of sight, shifting your scan to the aeration left in the wake of whitewater improves horizontal stability. Though it may feel unnatural at first, this technique improves performance.