Translating Tendency, Lateral Guidance, Hover Attitude
Translating Tendency – On an instrument approach to a hover, as power increases and airspeed decreases, if the helicopter remains in a level attitude, translating tendency will create a “slide.” In helicopters with main rotor blades that turn counterclockwise (e.g., the MH-60T), translating tendency results in an appreciable right drift at slow relative airspeeds with wings level. This drift starts around 40 kts of relative wind and increases as relative wind approaches zero. Avoiding the right drift requires left wing down to track a straight line over the ground.
The MH-60T is equipped with EGI hover bars to gauge the appropriate left wing down attitude to track a straight line over the ground. The hover bars replace the CDI at 50 kts groundspeed and course deviation is indicated by a small, magenta cross under the attitude indicator (HSD). In situations requiring precise lateral navigation, it is imperative pilots are proficient at scanning this lateral deviation indicator on the MH-60T flight instrument display because of the propensity to end up right of the intended course, due to translating tendency.
Also, pilots in the MH-60T tend to overlay RADAR on the CDI. However, the hover bars automatically replace the CDI at 50 kts groundspeed, which removes the RADAR overlay. A common error in our community is to start the approach without the RADAR selected on another display (MFD), as RADAR provides the only accurate, real time obstacle clearance information available when the helicopter is low to the water. While the nonflying pilot can rectify the error with a few button pushes, it unnecessarily detracts from his or her pilot monitoring duties during a critical phase of flight.
Hover Attitude – The MH-60T hovers 4-5 degrees nose up and 2-3 degrees left wing down. In the decelerating and descending attitude, the pitch attitude will be higher than hover attitude and pilots should slowly feed in left wing down to track a straight line over the ground. As the helicopter slows, pilots need to smoothly lower the pitch to the hover attitude. If a decelerative attitude is maintained (above the 4 to 5-degree hover attitude), the helicopter will back down. If pitch is lowered too far, the helicopter will continue a forward air taxi, cutting into horizontal obstacle clearance.
I prefer to trim the 4–5-degree pitch attitude early in the approach and work against the trim to decelerate. I find it extremely beneficial to have the force trim set at the hover pitch attitude when establishing a stable instrument hover.
