* INTRODUCTION
What does "Time In Your Tanks" mean? Depending upon your aircraft's
particular fuel consumption rate, the amount of useable fuel in your aircraft
equates directly to how long your aircraft will fly. The longer you can fly,
the more
choices you have for ensuring a safe flight: consequently, you can say that
flight time equates directly to flight safety. What no pilot wants to happen
is to have a forced off-airport landing and an accident because of fuel
starvation, or an emergency without enough fuel to be able to solve the problem
or to reach an airport safely.
To ensure that a fuel-related forced landing is not in your future, you should
always plan on landing before the "time" in your tank expires. Know
your aircraft's limits and don't exceed those limits. Every pilot needs to remember
that the performance and fuel information in his or her POH is based upon manufacturer's
data derived from testing new aircraft with experienced test pilots. You and
your aircraft may or may not be able to match its POH data.
You should be conservative and allow for that extra margin of safety.
The following provides some general tips on determining and managing the "time"
in your tanks. These are general comments only. All pilots need to review and
follow the operating procedures and limitations published in their particular
aircraft's Pilot Operating Handbook or other operating manual.
HOW TO DETERMINE THE "TIME IN YOUR TANKS"
Maintain accurate flight time, power setting and refueling records for each trip to determine fuel usage per flight hour.
Be conservative. Figure your flight time from engine start up to shut down.
Reasonably accurate fuel consumption rates can be computed after a few flights under similar operating conditions.
The amount of useable fuel for your aircraft can be found in your aircraft's POH.
Multiply the useable fuel on board by 75% and divide the result by your previously
confirmed consumption rate. This will be your SAFE FLIGHT TIME limit for the
aircraft at that specific operating condition. Resolve never to
exceed it.
VFR and IFR fuel reserves required by Federal Aviation Regulations parts 91.151 and 91.167 specify 30 minutes of reserve fuel for day VFR and 45 minutes of reserve fuel for night VFR and IFR flight, assuming normal cruising speed.
OTHER TIPS ON FUEL MANAGEMENT
Compute a reasonable time limit for your aircraft.
Factors to be considered in planning each flight include:
1. Trip length
2. Cruise altitude
3. Wind - don't count on forecasted tailwinds, they can change. Allow for stronger
than forecasted head winds.
4. The number of passengers (weight plus baggage)
5. In-flight physiological endurance of those on board
6. Guidance in the pilot's operating handbook.
7. Available fuel stops and alternate destinations in case of weather.
8. Computed aircraft gross weight and center of gravity limitations.
Compute your estimated time of arrival (ETA) for each checkpoint. Be aware of your actual progress and think about landing at an alternate if you are running behind on your ETA's.
Use the grade of aviation gasoline specified in your POH for your particular
aircraft. Normally, you can use the next higher grade when the specified grade
is not available. Always follow your aircraft's POH regarding any aircraft
operating question. Never use automotive gasoline or aviation fuel of a lesser
grade than that specified by your aircraft's manufacturer without the approval
of the manufacturer or FAA. Lower grade fuels detonate under less pressure and
can cause excessive engine temperatures.
Visually check the fuel in your aircraft for proper type, grade and possible
contamination. Drain the fuel sumps and strainers before the first flight of
the day, after each refueling (wait 15 minutes for any water or sediment to
settle) and during each pre-flight inspection as directed in your aircraft's
POH.
NEVER assume your fuel quantity and grade to be correct. Visually check it.
Know the fuel system of your aircraft and how it operates. Never operate a fuel system selector control without visually checking its position and operation, confirming it has fully actuated and is resting in the correct detent.
Fuel gauges are subject to malfunctions and errors. Fuels gauges must only
be calibrated to accurately indicate an empty tank. They do not have to be accurate
at any other fuel level. Therefore, unless restricted by the gross
weight or center of gravity limits of your aircraft, it is considered good judgment
to top off the tanks at all stops. If the fuel load must be limited, an accurate
measurement can be made by use of a dipstick calibrated for your
specific aircraft.
Water condensation can occur in partially-filled fuel tanks when the temperature drops. Filling your aircraft's tanks at the completion of each trip will reduce the probability of condensation. Be aware that water condensation can also occur in fuel storage tanks and trucks. Because there is always the possibility of water contamination, you should always check your fuel for water. In winter operations, if your fuel contains any water, ice can form in your fuel tanks and lines during freezing temperatures.
Do not reposition the fuel selector just before takeoff or landing. Always check your aircraft's POH for the proper procedure.
Never run a fuel tank dry as air can be drawn into the fuel system by the fuel pump(s) and cause vapor lock.
Know why you should lean the fuel mixture (i.e., increase the proportion of
air in the fuel-air mixture). Although you should always follow your POH and
appropriate checklist when operating your aircraft, you generally lean an
engine:
1. To improve engine efficiency and increase airspeed
2. To provide smoother engine operation
3. To provide greater fuel economy and longer range of operation
4. To provide longer spark plug life with less fouling (including clearing a
fouled plug during run-up)
5. To reduce maintenance costs
Generally you should lean:
Normally aspirated engines
a. Lean any time the power is 75% or less
b. Use full rich for full throttle operation at 5,000 feet density altitude
and below
Turbocharged engines
a. Always use full rich for takeoff regardless of altitude
b. Lean at cruise as recommended by the manufacturer
Know how to adjust the mixture setting for high density altitude takeoff and
landing. Again, you should follow your aircraft's POH, but you should generally:
1. Lean to maximum RPM for carburetor engines
2. Lean to proper fuel flow and fuel pressure settings for injected engines
3. Lean before entering the traffic pattern to ensure maximum power for go-around
Enrich the mixture for descent as required only:
1. Enough to keep the engine running smoothly.
2. Go to full rich when in the traffic pattern (or as required for full available
power when landing at high density altitude elevations). Check your POH for
the proper procedure.
REMEMBER - "YOUR WATCH IS YOUR BEST FUEL GAUGE"
"A TANK FULL OF FUEL IS A TANK FULL OF TIME"
Answer these questions, then go back and see if you got them right.
1. True or False: Fuel gauges must only be calibrated to accurately indicate an empty tank; they do not have to be accurate at any other level.
[ ] a) True
[ ] b) False
2. The practice of running a fuel tank dry prior to switching tanks is considered unwise primarily because
[ ] a) the engine-driven fuel pump or electric fuel boost pump may draw air
into the fuel system and cause vapor lock
[ ] b) the engine-driven fuel pump is lubricated by fuel and operating on a
dry tank may cause pump failure
[ ] c) any foreign matter in the tank will be pumped into the fuel system
3. Which one of the following would likely cause cylinder head temperature and engine oil temperature to rise beyond their normal operating ranges?
[ ] a) Using fuel that has a lower-than-specified fuel rating
[ ] b) Using fuel that has a higher-than-specified fuel rating
[ ] c) Operating with higher-than-normal oil pressure
4. Filling the tanks after the last flight of the day is considered a good operating procedure because this will
[ ] a) force any existing water to the top of the tank away from the fuel
lines to the engine
[ ] b) prevent expansion of the fuel by eliminating airspace in the tanks
[ ] c) prevent moisture condensation by eliminating airspace in the tanks
Copyright (C) 2010 by David R. Hunter, All Rights Reserved