Poor Fuel Management

Poor Fuel Management


I am the proud father of two wonderful children. I have a son which I am very proud of currently serving in the USMC and stationed across seas. He chose aviation as an area of service and is currently working on the helicopters. I also have a daughter which just turned 15 years old this past February. Just like most teens her age there is one major milestone on her mind, the automotive learner’s permit. After more then 25 years of driving some areas are you can say just 2nd nature to me but, when my daughter is behind the wheel I tend to be a little more apprehensive. I guess I can now understand how my flight instructor felt when he handed the yoke over to me for the 1st time.

Early on in my flight training an instructor once said to me “A new private pilot knows just enough to be dangerous, there’s a lot more to flying then just knowing how to land”.

One area of 2ndnature or rule of thumb if you will in aviation I hear pilots talking about is fuel management. Even I remember as a student pilot long before Duats or AOPA came along with there electronic flight planning program and I was being taught how to fill out a paper flight plan I was told to use a particular figure for the fuel burn on our Cessna 172 that I trained in.

Recently I attended a seminar entitled “Basic VFR flight planning” led by Matt Conway, Chief flight instructor with American Flyers in Atlanta, GA. Poor fuel calculations have claimed the lives of many people explains Matt, as pilots use the “Rule of thumb” to calculate fuel consumption for their flight.  Not a good idea he said!

The round up figure may work for shorter flights but for longer cross country flights don’t take the chance. The Cessna Aircraft Co. recommends the following fuel calculation procedures. The following is an example of proper fuel calculations for the 1982 Cessna Skyhawk 172P.

Flight conditions:

Take off weight               2350 Pounds

Useable fuel                     40 gallons

Temp                                28º C

Field Pressure                   1500 feet

Wind (along runway)       12 knot head wind

Distance                            320 NM

Pressure alt                        5500 Feet

Temp                                 20º C

Wind enroute                   10 knot head wind

Power                               66%

True air speed                  112 knots

Cruise fuel flow                7.4 GPH


Fuel to climb                                                                                            1.6gal

Increase due to non standard temp                                                0.3gal

Corrected fuel to climb                                                                        1.9gal


Total distance                                                                                           320

Climb distance                                                                                         -12

Cruise distance                                                                                         308


(With 10 knot head wind)

True air speed                                                                                           112

Wind speed                                                                                                -10

Actual speed                                                                                             102                                  


308 Nautical Miles

102   Knots                                                                                               = 3.0 hours


45 minute reserve                                                                                  5.6 Gallon


Engine start, Taxi, and take off                                                           1.1

Climb                                                                                                           1.9

Cruise                                                                                                          22.2

Reserve                                                                                                      5.6

Total fuel required                                                                                30.8

Becoming relaxed in your preflight procedures can cost you more then time. Count the cost, spend the time and do it right regardless of your experience.      

Tommy Eldridge  

(source: 1981 Cessna  POH for the Skyhawk 172P)                      
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