Trim Baselines When Hoisting

I mention the use of force trim frequently in hoist discussions. It’s an elementary topic—so basic, in fact, that most helicopter pilots trim subconsciously. But in demanding hoist environments, this unconscious habit can increase workload and degrade helicopter control. 

As a hoist instructor working with pilots from services that don’t specialize in rescue, I’ve had the opportunity to train some highly experienced helicopter pilots. Often, these pilots have thousands of flight hours but relatively few hoist repetitions. One of my consistent observations: the more experienced the pilot, the more critical it becomes to re-emphasize intentional use of force trim. Years of maneuvering in land environments with rich visual cues have created habits that don’t translate well to the limited-cue, precision-hover demands of maritime hoisting. Similarly, with relatively junior pilots, good trim habits should be developed from the onset. 

Being a stable hoist platform in a degraded visual environment requires an intentional mindset shift—to ensure trim is being used consciously and methodically. This post outlines how force trim can serve as a baseline—a known reference point to return to or work against—to control lateral and vertical motion more deliberately and effectively. 

Cyclic Trim Applications

1. With a Vessel Underway: Trim the cyclic to fly in formation with the vessel. This creates a force trim reference that matches the helicopter’s motion to the vessel’s speed. It reduces workload while establishing a stable hover over the hoist target and becomes especially valuable if visual contact with the vessel is temporarily lost. 

2. Over a Stationary Target (Dead in the Water Vessel / Swimmer / Survivor): Trim laterally for zero relative motion. If there’s no current, this equals zero groundspeed. If there is current, groundspeed should match the current’s velocity. Setting this zero-relative-motion trim is crucial when the survivor or swimmer is directly beneath the helicopter and outside the pilot’s field of view. It enables the crew to hold position precisely with minimal cues. 

3. Swift Current Situations: Setting and maintaining zero-relative-motion trim allows the crew to understand drift behavior—how quickly the survivor may be moving toward hazards like jetties, rocks, or surf zones. At night, or in degraded visuals, this trim baseline provides a shared mental model for the crew, supporting better spatial orientation and coordination between pilots and the flight mechanic.  

Once the “baseline” is trimmed, work against the trim for lateral movement. If the pilot needs to move the helicopter forward and right relative to the hoist target: 

• Displace the cyclic forward and right against the force trim to initiate movement. 
• Once moving, neutralize the cyclic. 
• To stop motion, move cyclic aft and left as needed, then use force trim to re-establish the new hover reference. 

Most force trim systems require only fingertip pressure to work against and small, subtle control inputs. 

Collective Trim Applications & Power Settings 

In the Coast Guard H60 community, we commonly use RADALT hold over calm water. However, as sea state worsens or terrain varies, RADALT hold can command unwanted climbs or descents. BARALT hold is another option but can become unstable due to pressure fluctuations caused by wind and rotor wash near the surface. These autopilot systems can become a crutch—precise in benign conditions, but unreliable in the dynamic ones where manual control with force trim is essential. 

When using collective force trim to maintain hover power: 

• In-Ground Effect (IGE): A given power setting correlates to a specific altitude. Example: 87% torque = 40’ hover; 83% = 20’. If you set 87% at 20’, the helicopter will climb to 40’ and stabilize. 

• Out of Ground Effect (OGE): Hover power is not specific to an altitude. A specific torque will hold a level hover at different altitudes (e.g., 93% at a specific weight = a level hover at 100’ and 150’). Changing power alters altitude, but returning to baseline stabilizes the aircraft—not at the previous height, but at the current one. 

In either case, starting lateral movement from a zero-wind, zero-groundspeed hover usually causes a descent unless power is added. Stopping motion to reestablish a hover often requires reducing power to avoid a climb. The exception is when you hover with a relative wind that is greater than effective translational lift (ETL). As you accelerate into or above ETL, the aircraft becomes more efficient, which can cause a climb unless power is reduced. Decelerating out of ETL has the opposite effect—requiring a power increase to prevent a descent.  

Regardless of wind conditions, lateral movement will require power adjustments to maintain level flight. Working against the trim for these brief transient power adjustments maintains a collective force trim baseline when the helicopter resumes zero relative motion over the hoist target. This helps minimize altitude deviations and vertical oscillations—both critical for maintaining a stable hoist platform. 

Caveats for Non-CG H60 Operators – The H60’s stability augmentation system (SAS) is highly capable. With force trim engaged, the autopilot helps smooth out hover inputs and wind gusts. Some other helicopter models lack this capability, and in those aircraft, the pilot bears more of the burden of manually dampening motion—with or without trim. Still, even in helicopters without advanced SAS, force trim remains a powerful tool for hover precision. It provides a tactile reference point, which is especially useful when visual cues are limited. 

I’ve also worked with operators using EGI (Embedded GPS/INS) holds. In some airframes, EGI hold provides excellent lateral and vertical stability, even in dynamic sea states. In others, performance varies. If your aircraft has EGI hold, test its behavior under different conditions and integrate it into your crew’s procedures accordingly.