Max Range Calculations/Planning (Continued)
A few common consideration gaps for helicopter pilots unfamiliar with max range planning:
True Airspeed versus Indicated Airspeed at altitude: True airspeed is the speed over the ground (zero wind). Many helicopter pilots inexperienced in long-range flying use indicated airspeed for max range calculations when true airspeed is the appropriate measure for calculating distance covered over time.
In the MH6T0 Coast Guard community, the charts show both indicated and true airspeed. However, a solid rule of thumb is that true airspeed is 2 knots faster per 1000’ than indicated airspeed (e.g., at 6000’ 100 kts indicated airspeed = approximately 112 kts true airspeed). I still harness this rule of thumb for quick mental calculations or to double check chart work.
Max Range Airspeed Adjusted for Wind: Another rule of thumb for max range airspeed adjusted for wind is to increase indicated airspeed 2.5 knots for every 10 kts of wind (flying faster into a headwind and slower with a tailwind). This is what CAAS uses to calculate max specific range airspeed.
Fuel consumption updates/variability: I regularly see pilots using the initial fuel burn throughout a mission, which is conservative. However, if the mission requires more specificity, the burn rate should be updated at regular intervals such as every 100 nms or every 1000 lbs. of fuel burned.
The “Triangle Route”: When going offshore for a mission, pilots tend to be fixated on returning to the location from which they departed. Often a “triangle route” is optimal because it can reduce overall distance traveled. The southwest U.S. provides an excellent example. I have launched for a long-range case west of San Diego and recovered in Santa Barbara because it was closer than San Diego.
In other instances, the triangle route allows pilots to reduce the headwind or increase the tailwind components. Using the northeast as an example, I have launched from Cape Cod on a long-range case to the southeast with strong winds out of the east and recovered in Atlantic City, traveling more distance but burning less fuel than going back to Nantucket.