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May 14, 2008
A top concern among AOPA members is the rising
cost of avgas. Although alternate fuel sources are being explored
all over the world, it will be some time before any of them have a
direct impact on general aviation.
You can minimize the hit to your wallet by
practicing a few simple fuel management techniques. Proper leaning
combined with a lower economy cruise setting and a cruise descent
profile can result in significant savings. Also, remember when
you’re planning cross-country flights to check FBO fuel prices in
AOPA’s Airport
Directory for the best deals.
Leaning
Leaving the mixture knob forward the entire flight
is a big fuel waster; not to mention that a full rich mixture at
cruise power can actually hurt some engines by causing rougher
engine operation and vibration. When properly done, leaning provides
greater fuel economy, smoother operation, and longer engine life.
Most engine manufacturers recommend leaning when
operating at or below 75-percent power. Above 75-percent power, the
engine needs more fuel to help keep it cool. Flying lean of peak is
another step to maximize your fuel savings. We’ll leave this
decision up to you per the manufacturer’s recommendations.
On longer cross-country flights, adjust the
mixture to account for pressure and weather changes and changes in
altitude to maintain the best economy fuel/air ratio. On the ground,
at lower power settings, you don’t have to worry about over-leaning.
You can save fuel by leaning aggressively during taxi.
Economy cruise
In combination with proper leaning techniques,
consider bringing the throttle lever farther back during cruise. A
best-economy power setting will provide the most miles for the
gallon.
For instance, on a 200-nm cross-country flight in
a Piper Archer, bringing the power to 65 percent at best economy
will save 3 gallons (6 gallons round trip) when compared to flying
at 75-percent best power.
AOPA’s Real-Time
Flight Planner shows the flight arriving nine minutes later when
flying at 65 percent. Time is valuable, but nine minutes is likely
worth the $18 savings on each leg of the flight.
Aircraft manufacturers provide best-power and
best-economy fuel flow based on proper leaning technique, so fly at
the recommended power setting. Simply leaning at a random power
setting or only reducing power without touching the mixture won’t
yield the desired fuel burn and may lead to serious fuel
mismanagement.
Cruise descent
The most poorly managed segment of a flight is the
descent. Instead of flying straight to the airport traffic pattern,
leave the power setting where it is and prepare for a gradual
500-fpm descent to the airport.
If, for example, you are cruising at 5,500 feet
msl and want to descend 3,500 feet to the traffic pattern altitude,
start your descent about 15 miles out to achieve a smooth cruise
descent profile. No need to touch the power, just lower the nose
slightly with a trim adjustment. The passengers in the back will
also enjoy this smooth and well-planned descent. Compared to the
alternative practice of arriving at the airport high and adding time
in flight by circling down to the proper altitude, you can save $6
in fuel costs.
Over the course of a 200-nm cross-country in the
Archer, a pilot can save a gallon by leaning when taxiing on the
ground, 4 gallons in flight with proper leaning and economy power
settings, and another gallon with a cruise descent.
At a total of 6 gallons and $6 per gallon, that’s
$36 one way and $72 round trip! Over the course of a dozen flights,
investing a few minutes of your time each leg of your trip will
yield a savings of hundreds of dollars. Not a bad way to fight back
against inflated fuel costs.
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