Flight Planning & Fuel Calculations

by HPA · November 20, 2011

It’s All Going According to Plan

By Hank Gibson, CFI, CFII, MEI

Fuel Calculations

How much fuel does the airplane you are flying hold? This is a very important question that most pilots take for granted. Let’s keep things simple and use a Cessna Skyhawk for example. It holds 53 usable gallons of fuel. At an average cruise power setting, the airplane burns roughly 9 gallons an hour. That all adds up to approximately 5 hours and 48 minutes of fuel till the tanks run dry. Let’s say that you own the airplane and you and a co-worker fly it 4 days a week for work. With both of you in the front seats, you can take full fuel and don’t have to worry about weight and balance. The trip takes about four and a half hours, there and back, so you never have to worry about filling up until you get back home.

How much fuel can you take on this flight? This is, quite possibly, an even more important question than the one of fuel capacity. Let’s go back to our Skyhawk example. One day, your boss calls and tells you that a new guy is coming aboard and he will be accompanying you on your flights. The first, most obvious question is, how much does he weigh? Every pilot thinks about that. But now, suddenly, you can’t take full fuel.

The night before, you call the FBO and have them fill up the airplane with only 25 gallons much lower than normal. After a glass of milk, you’re off to bed with no second thoughts. Early in the morning, you sump the tanks after some coffee and a donut, then you and your co-workers are off. You press the direct to key shortly after lift-off, turn the autopilot on and sit back to enjoy the sunrise. (side-note: doing the math, 25 gallons only gives you 2 hours and 42 minutes of fuel; 2 hours and 12 minutes before the FAA mandated VFR reserve).

After a long day on location, all of you hop back into the airplane for the ride home. You never check the fuel before leaving because there is always enough. After a chocolate bar and some water, it’s off into the night. Half an hour into the flight, the engine sputters, you stall the airplane while trying to find a place to land in the dark, overcompensate when a wing dips with the yoke, spin and die, killing two others with you.

Harsh? Yes. Real? Absolutely. Fuel plays into more than just weight and balance. Fuel is a pilot’s life blood and when he doesn’t take the time to do fuel calculations for a flight, it is asking for trouble. Weight and balance questions should always be followed by fuel burn questions. Will we have enough fuel to make the trip like normal? Do we need to fill up elsewhere? Do we need an extra fuel stop? Should I run the engine on 65% power instead of 75%?

All that to say, planning must still go into flights. It is so easy to fall into the trap of getting in the airplane, pressing the direct to key to the destination and just flying, letting the G1000 “do all the work.” The last question to ask before getting into the airplane should always be, have I calculated the fuel needed for our flight?

How it Started

One of my best friends in high school, (Doug Gray) was a private pilot. He offered to take me up for a flight in a 1967 Cessna 150, N6228S. We took off from Calhoun, Georgia, and he took me on a scenic tour of the area, I was hooked. I later found out that my English teacher, (Jan Haluska) was also a flight instructor and the school was offering a ground school course the next year, which he taught, along with flight training with the goal of becoming a private pilot. I managed to talk my dad into funding the training, at the time the total cost was right around $500. Cessna 150 rental rates where $12 an hour, and the 172 we used for cross country was $15 an hour including fuel.

Training Begins

It started August of 1977. The fall semester rolls around, and I am enrolled in ground school, and if memory serves me, we met twice a week. First came the paperwork for my student pilot certificate, which at the time was included with the 3rd class medical. I loved ground school, especially learning navigation, plotting courses on the sectional, again this was before iPads and GPS, so we did a lot of dead reckoning and VOR navigation for cross countries. At the end of the course, I made an 83% on the Private Pilot written exam, remember this was before we had the question-and-answer books that on future test I would consume before taking a written.

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The fun really began on August 22, 1977, it was my first flight. To my surprise we used the same Cessna 150, N6228S that my friend Doug Gray had taken me for a ride in. The Cessna 150 had a standard VFR instrument panel, with one NAV/COM, and one VOR CDI. No intercom, so no headset, at the time I didn’t know what I was missing. I didn’t get my first headset until I started my instrument training in 2003. I was a big guy, I was 6’ 4” and weighed 245 lbs. but I do not remember being uncomfortable in the 150 even with the instructor in the right seat.

First flight lasted .8 hours, and we accomplished orentation, shallow turns, stability, and effects of flight controls. Over the next few months we added steep 720’s, slow flight, stalls, turns around a point, S-turns, emergencies, landings, (short field, soft field and normal).


At this point I want to talk about a training experience that still stands out. We were close to solo and were practicing takeoffs and landings. Turning base to final Jan got very upset at the way I was cross controlling the aircraft. Cross control is when you are in, say a left turn, and use opposite rudder to line the nose up with the runway. So, he had me depart the pattern and head east to the practice area, and climbing up to 5500 feet MSL, he had me slow down to just above stalling speed, start a left shallow turn and add right rudder. As the airplane stalled I had the strangest sensation, no roller coaster has ever come close, instead of blue sky in the windscreen I was looking at brown ground, and as far as I could tell we were upside down, through the terror of the moment Jan talked me out of the spin, controls neutral, oposite rudder, pull slowly out of the dive. As we leveled off he asked me what altitude we were at, as I remember it was around 2,800 feet MSL. Then he asked me what would happen if I experenced this on base to final in the traffic pattern. The answer was obvious, I would be a pile of wreckage off the end of the runway with a very short-lived aviation career. Needless to say this cured my cross-control tendencies.

Another training event the sticks out in my mind was the first time we did takeoffs and landings at the High School runway. The runway was 1,500 feet long, not sure of the width, but it seems like we had about 5 feet on each side of the wheels when on the center line of the runway. Landing from the south you also had to go between a cutout in the trees to be able to stop in time on the runway. After getting confortable landing here every runway since seemed huge. I remember landing at Chattanooga (KCHA) on a night cross country and commenting to Jan, that I felt like I could of landed sideways on the runway, it felt that large.

Very soon after this I started wearing old shirts to all my flight lessons, the reason for this occurred on February 8, 1978. The lesson that day was stalls, takeoffs and Landing. As we were taxing back in Jan told me it was time for my first solo. I was very excited, and after some last minute advice from Jan, including watch for floating on landing the plane will be light with him not in the right seat, complete 3 takeoffs and landings to a full stop. It was a blast, and at the end of my shirt was shorter in the back because Jan cut the tail out of it signed and dated my solo [an aviation tradition]. Total flight time accumulated on the day of my solo was 18.1 hours. I was now officially a pilot with solo priveleges.

In my next article I start cross country training, when Jan decided that it would be best accomplished this in the 172. Checking out in N5970R was like moving into a 747, this started a love affair with one of my faviriote planes to date. Since this time I have flown over 900 hours in many different models of the 172 and feel like I am stepping into an old friend every time.

More about Randy here: https://www.flyhpa.com/team/randy-delong/


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