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Along the years and countless flight hours, we tend to forget, or at least to downgrade some of our most remarkable experiences. Take, for example, those of the early days of our training where the memories may fade in favor of the new and more exciting things we experience as we progress in aviation. There’s even more displacement if you pursue aviation professionally as the challenges become increasingly more difficult.
The other day while flying an ETOPS (see definition below) route south of the Sahara Desert, at least a couple hours of our closest alternate, a rather insistent strong headwind made for a much higher fuel consumption than planned. The additional fuel was significant enough for me, as pilot monitoring on that sector, to suspect something more than a stronger than forecasted headwind. In the end, any suspicion of a fuel leak was gone as all our fuel consumption numbers started to match what was planned and we even arrived at our destination with even more fuel than planned.
ETOPS – (Extended-range Twin-engine Operational Performance Standards) the rules by which twin-engine airplanes can be operated beyond one hour from a suitable alternate airport.
And since fuel is one of those parameters that we learn to monitor closely from the start, it reminded me of a story written over Florida’s panhandle ten winters ago. The flight school where I was building my time did not allow us to stay overnight with the airplanes out of base. So all of our flights had to be turnaround or out-and-back flights. After flying to dozens of airports in Florida, and to destinations in Georgia and even South Carolina, I wanted to add a new state to my list. So, maybe inspired by the “Sweet Home” song by Lynyrd Skynyrd, I invited a friend to be my safety pilot on a flight to Alabama.
After considering some options, we decided to fly to Dothan (KDHN), located conveniently close to the border with Florida. After all, we did not have time to do much during our short stay and the idea was more like having the personal achievement of putting a pin on the map of another state. The straight line route was 225nm, quite comfortable for the range of a Cessna 172. Yet, with the Military Operations Areas (MOAs) we had to avoid, plus choosing some familiar alternates to fly over, the final distance of the route was 280nm. We did the math and completed a full navigation log. Given the forecast winds, planned true airspeed, and adjusted ground speed, we calculated a flight time of three hours and five minutes. Expecting to burn seven gallons per hour, that would be roughly 21-25 gallons total, with some margin. This burn is was well below the 38 gallons of usable fuel aboard the 1960’s era Skyhawks, and comfortably above the 30 minutes reserve fuel required for day VFR flights.
On a beautiful morning, we lined up on DeLand’s (KDED) runway 5 and took off, leaving the home base behind. The skies could be classified as a severe CAVOK (ceiling and visibility OK). We could see a bigger chunk of central Florida as we gained altitude, and with only a thin cloud layer up in the flight levels, we climbed to 6,500ft over Lake Crescent. As planned, our Cessna 172 was taken North to Palatka, then west to Cross City, before turning northwest on an almost straight line to Dothan that eventually overflew the Florida capital of Tallahassee as well.
On a beautiful morning, we departed from DeLand’s (KDED) runway 5 not aware of what the day would bring.
It was over the green plains of the Gulf of Mexico coast that our carbureted engine started to complain about the cold. Not that we weren’t wearing jackets ourselves, but with no clouds around, the carb icing came literally out of the blue. As was standard procedures, we opened the carb heat and experienced an even bigger drop in RPMs. Therefore, we put some more throttle in to compensate. The power recovered as the ice dissipated. Nevertheless, entering an area with not many alternate airports, we decided to keep the carb ice half opened to prevent any surprise.
We opened the carb heat and experienced an even bigger drop in engine RPM.
With the winds a bit stronger than planned, and with colder temperatures and more moisture than we anticipated, the extra power and time aloft meant more fuel consumption. But different from an airliner where you have accurate and reliable fuel indicators, in our 1968 piston single, we were going more by the time and planned fuel burn.
And when it comes to flight time, we were already expecting a long one, but Tallahassee seemed to take forever to appear below us and Marianna wasn’t any faster. Finally, Dothan was coming into view. The approach to Dothan was a long and uneventful straight in, under a beautiful early afternoon sun. The first sign that something wrong was when my mobile started ringing during the roll out. Since it was in the front pocket of my jacket and we had already determined our taxi route, my friend Regis picked it up and answered. It was Flight Service calling with whom we had filled the flight plan earlier that morning and we had gone beyond the 30 minutes after our estimated time of arrival!
The approach to Dothan was a long and uneventful straight in, under a beautiful early afternoon sun.
How come? Maybe our delay on the way out was longer than we noticed… well, ok, “we are on the ground, thank you sir”.
We parked by the local FBO and requested them to top off our fuel for our flight back to home base. We went to the vending machine, had some snacks, relaxed a bit on the comfy seats and then it was time to pay the fuel bill – WHAT?!
Surprisingly, the FBO pumped 34.5 gallons into our Skyhawk! That calculates to only 3.5 gallons remaining (slightly below the 30 minutes of required fuel). Not yet a close call, but obviously much less than we were planning to have, and certainly an amount that would have granted us a MAYDAY fuel under the VFR rules if we were aware of it.
Almost a decade later, the reasons why we got into that situation are easy to explain: the extra RPMs to compensate for the half-opened carb heat, a probably too conservative mixture, and of course stronger than forecasted winds aloft. It’s been said that no strategy resists to the battlefield – or as Mike Tyson used to say, everybody has a plan until they are punched in the face. So, if I forgive (the inexperienced) ourselves just a bit, we did a proper planning. In the end, we did not run out of fuel altogether even with so many odds against us. But this is a great reminder of the Dan Gryder concept: the regulations give you the minimum while Mother Nature and karma ask you for the maximum.
- Always a student—some advice for aspiring professional pilots - December 4, 2023
- My near fuel emergency - February 20, 2023
- Fly-by-wire for beginners - November 25, 2022
Woww, that was close!
Yeah, too close for my taste. But a lesson learned, and now shared. Cheer!
I fly a 182 with the extended range tanks. I also won’t fly more than 2-3 hours at a stretch before a bathroom break. That’s a good time to refuel and get out of the seat. Try this method.
Very well said. That was our usual approach, but this day we tried to stretch the range instead. I’ve done longer flight later, all the way to DC, without this kind of surprise. I have never flown the C182, must be a nice ride! Thank you for the comment!
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I have been flying my 1966 172g for 39 years. I was instructed in primary flight training to NEVER use partial carb heat. Use either full heat or none.
I don’t know if this info is in any Cessna manuals but it has served me well.
Good to hear the flight ended well.
Great insight, thank you!
An additional comment on carb heat in a Cessna.
The pilot noted an additional loss of power when he applied carb heat. That is fairly normal as the heat is melting the ice in the carburetor throat and the engine is ingesting the ice/water leading to a temporary additional loss of power.
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Carb heat also changes the fuel-air mixture. Hotter air means less air. So lean out the mixture too.
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The reference to Dan Gryder’s concept highlights the idea that regulations often set a minimum standard, but real-world conditions can demand much more from pilots @io games