MILITARY
By Steve “Elroy” Colby
Old School Fuel Planning
Computing available fuel for con- tingency mission execution is an art lost to the technology of mis- sion computers. Sometimes having a simple tool to pull from your mental
toolkit or from a page in your kneeboard
can be a godsend during time-critical mission tasking.
When tasked for a mission that includes
a search, it’s paramount to properly calculate
all the segments of the search and rescue
which consume fuel. Clearly, you must
calculate the time and fuel consumption for
the enroute portion of your mission. Based
upon mission criticality and/or available
onboard fuel, this may be flown at maximum continuous speed VH or maximum
range speed VM/R. A commonly omitted
allowance is for sighting checks. Deviations
from planned search patterns to confirm
or ignore a possible sighting often consume
5 percent of total fuel onboard during a
search. Remember to include fuel for the
survivor landing (or hoist) and recovery.
Some turbine aircraft burn substantial
amounts of fuel even at flat pitch while waiting for the medics to package your patient.
Some aircraft can’t be throttled back to idle
without bringing an APU online which then
consumes a large portion of the potential
idle RPM fuel savings. Knowing and using
your most fuel efficient idle mode is essential to saving fuel and maximizing support
time. Knowing your bingo fuel helps make
the idle versus shutdown decision. The
next enroute leg is to the hospital or recovery area. Again speed is dependent upon
patient criticality, available fuel and distance.
Remember to calculate the distance from
the farthest point in the search area as Murphy always seems to put you there when you
need gas or find your survivor. Sometimes
you’ll simply have to fly at VM/R to have sufficient fuel reserves to make it to the delivery
site. Delays at the hospital helipad are inevitable. From the delivery point you’ll have to
either get to a fueling site or home. Finally,
civilian and military regulatory guidance
provides the requirements for your VFR
or IFR fuel reserve. What results is a simple
kneeboard spreadsheet format on which
you have all the consumables in the top box
in both pounds and hours and the available
fuel on the bottom from which you subtract
the sum of the consumable segments. The
fuel remaining after these segments is that
available for the search. The planner then
has to determine at what speed he’s going
to fly his search pattern to maximize cover-
Search & Divert Fuel Calculation Sheet
Fuel Required
a. Enroute Hrs
b. Sighting Checks Hrs
c. Recovery Ground/Hoist Hrs
d. Trip to Hospital Hrs
e. Hospital Loiter Hrs
f. RTB/Refuel site Hrs
g. Reserve Hrs
Total Hrs
Fuel Available
Total in Tanks Hrs
Minus Total Above Hrs
Total Available
for Search Hrs
Joker = Bingo + 20 min
Bingo = Sum d. to g.
#
#
Hrs
Hrs
Joker
Bingo
age. A good rule of thumb is to use recommended cruise speed for preliminary route,
parallel or creeping line searches, and max
endurance VM/E speed for the concentrated
search portions. Establish a Joker fuel level
that triggers a crew decision point for search
continuation or a refueling stop.
One obvious need with this manual
method is a quick means to measure time,
distance and heading for the initial divert
and for the various segments without using
the navigation computer. Even the most
advanced flight management systems don’t
have the flexibility to quickly calculate segment fuel without manually entering several waypoints and running the fuel calculator. Keying in several lat/long takes a long
time and using a plotter and a whiz wheel
is a bit of a pain. I carry in my flight bag,
what’s called a Declitractor. I’ve made a local
modification creating a flexible laminated
plastic plotter scale that’s pinned in the center of it. This scale has distance and time (at
nominal VM/R speed) measurements with
1:500 sectional scale on one side and 1:250
JOG on the other. You drop the device
centered on your present position, align
the declination grid (adjustable for agonic
line changes), pull the plotter scale to your
destination to obtain time and distance, and
read the plotter line against the compass for
proper magnetic heading. Quickly put these
times into your fuel chart and compute the
appropriate fuel consumption for each segment based on required speed. The chart
provides a quickly calculated loiter/search
time for your mission, taking the guesswork
out of search and divert fuel planning.
