AOPA Pilot Magazine - August 2022 - 86

RUDDER & WRENCH
SWITCH
AND
SAVE
and our need for speed? One answer can
be found in a seminal research paper
written in 1980 by renowned professor
Bernard H. " Bud " Carson, Ph.D., of the
U.S. Naval Academy.
In his paper, Carson examined this
question: How much does it cost (in extra
fuel) to fly faster than the most fuel-efficient
airspeed (best L/D)? When he looked
at the ratio of excess airspeed to excess fuel
consumption, he found that it reaches a
maximum at an airspeed of about 32 percent
greater than best L/D. Carson referred
to this airspeed as " the least wasteful way
of wasting fuel. " The rest of the aviation
world calls it " Carson speed. "
For my Cessna 310, Carson speed is 146
2%
Cash Back1
on FBOs
& Flight Schools;
Aviation & Auto Fuel
CASH BACK1
APPLIED AS STATEMENT CREDIT.
QUARTERLY BONUS POINT CAP OF 2,500 POINTS*
Switch today to the AOPA
World Mastercard®, and stop
paying too much on your
aviation purchases.
Visit
AOPA.org/creditcard
to learn more
KIAS. For a Cirrus SR22, it's 121 KIAS and
for a Cessna 172 it's 86 KIAS. Now, that's a
little more like it!
Mixture
To optimize fuel efficiency, you need to
lean the engine aggressively. So-called
" best economy mixture " -which is the
mixture that achieves minimum brake
specific fuel consumption and maximum
miles per gallon of fuel-occurs well on the
lean side of peak exhaust gas temperature,
typically somewhere between 30 degrees
Fahrenheit and 70 degrees F lean of peak.
But you don't need to worry about EGT. If
you simply pull back the mixture knob to
the onset of perceptible roughness, then
push it back in just enough to make the
roughness go away (and not any farther),
you'll be in the best economy ballpark.
In addition to optimizing fuel efficiency,
operating LOP has other benefits.
The engine runs cooler and cleaner. The
stress on critical engine components
is reduced, as is the buildup of harmful
exhaust deposits on valves and other
combustion chamber components. LOP is
a kinder, gentler way to operate the engine,
and pays dividends in engine longevity.
Many pilots believe carbureted
engines can't be operated LOP, but that's a
myth. Most carbureted Lycoming engines
will run quite well LOP because the symmetrical
design of their induction system
provides reasonably even mixture distribution
to the cylinders. Carbureted
Continentals can be more challenging-
particularly the O-470 that powers the
Cessna 182, whose poor mixture distribution
is legendary-but with attention
to detail and a few tricks it can be done.
*Certain points and purchase restrictions apply; see full Rewards
Terms and Conditions for full details at AOPA.org/creditcard
editcard.
1 Rewards points can be redeemed for Cash Back or other items provided
through AOPA Pilot Rewards. A Cash Back redemption is applied
as a statement credit. The statement credit will reduce your balance
but you are still required to make at least your minimum payment. A
minimum of 2,500 points is needed to redeem for Cash Back. Values
for non-cash back redemption items such as merchandise, gift cards
and travel may vary.
Relationship among three
key indicated airspeeds:
best endurance, best
range, and optimum
cruise (Carson speed).
86
AOPA PILOT / August 2022
http://www.AOPA.org/creditcard http://www.AOPA.org/creditcard
AOPA Pilot Magazine - August 2022

Table of Contents for the Digital Edition of AOPA Pilot Magazine - August 2022
