PATCH Gate
All CG MH60T pilots know that the flight manual definition of the gate is “the point where the crew selects Auto Approach. If at 300-ft AWL and 70 KIAS, the gate is defined as 1.4 NM (subtract 0.1 NM for every 5 kt of wind) from the hover fix.”
A piece of information that all CG MH60T pilots should have memorized is that if auto approach is commenced at 300-ft AWL and 70 kts, this gate “should result in a coupled hover approximately 500-1000 feet down wind of the hover fix.” While 500 feet seems like an appropriate distance sitting at a desk reading the flight manual, in my experience, when a crew is in the helicopter at night in a ¼ visibility and flies a PATCH down to a large, deep draft with a super structure that is typically well over 100 feet tall (close to 200’ for a Panamax, close to 300’ for the world’s largest cruise ships), 500 feet of horizontal separation no longer seems sufficient.
One point of emphasis, although the gate is predicated on starting the approach from 300’ and 70 KIAS adjusted for wind, the approach can be initiated as high as 1500’. Extrapolating data from our 300’ 70 KIAS PATCHS, operators can reverse engineer the horizontal distance traveled when initiating automatic approaches from higher altitudes, but it is a rough estimate that lacks precision as the auto approach does not fly a consistent glidepath. If any type of precision is required, fly a MATCH from a higher altitude or descend to 300’ 70 KIAS and initiate a PATCH. The only time I personally execute a PATCH from an altitude higher than 300’ is when I am using the PATCH to get the helicopter under what I believe is a low, overcast layer with descent visibility underneath (e.g., a descent from 1200’ to 150’ and 40 kts groundspeed to air taxi underneath low clouds to a general search area to determine the search conditions and the feasibility of locating someone or something in that area).
An important reminder is that pilots can adjust the PATCH “glide path” by moving the cyclic trim switch forward to flatten the approach or back to steepen the approach. A normal angle will resume when the cyclic trim button is pressed. Consistent with my desire to err on the long side of a gate, I prefer to use the trim switch to stretch an automatic approach out, rather than shorten it up. Excessive movement of the trim switch aft can result in an uncomfortable and unusually high pitch attitude during an instrument approach to a hover.
