Self-service avgas at my home airport is now $5.65 a gallon. And it promises to go higher with the next delivery from the fuel supplier. Suddenly, the cost of fuel is a much larger portion of my operating costs. I've been running lean of peak so the Lycoming IO-360 in my Cessna Cardinal runs at something under 10 gallons per hour. Doing the math at 10 gallons per hour is simple. It's costing me slightly more than $56 per hour just for fuel. In mid-August, AirNav's Fuel Price Report found that of the 3,530 FBOs it surveyed, the average price was $5.60 (the low price was $3.75 and the high price was $8.70).
One of the indisputable rules of aerodynamics is that things get quiet when fuel no longer reaches the engine, whether from mismanagement of the fuel system or fuel exhaustion. Nevertheless, the accident history is rife with accounts of pilots who crashed or made emergency landings when their engines were starved for fuel. They either didn't know how to manage the fuel system or they were overly optimistic about how long their engines would run with the fuel they had on board.
I worry that the accident record is only going to get worse with the increase in the price of avgas and jet fuel as pilots try to stretch flights to reach their destinations without having to make a fuel stop or to reach an airport with less expensive prices at the pump.
In the past, I've religiously tried to fly at least once a week -- and the engine in the Cardinal seems to be happy with the frequent workouts. It continues to purr along hundreds of hours past TBO. But recently, I've found myself extending my "exercise" flights to a week and a half or two weeks. I'm not sure I'm being cost effective -- particularly as the less frequent use may affect the engine's health. Flying less often may also cause a diminution of my aviating skills.
So, the escalating cost of avgas has a potential influence on safety. Sharing flights with another pilot is one way to maintain proficiency while conserving fuel. I'll probably hear from readers that if I can afford an airplane I can afford the price of avgas, but I bought my 32-year-old airplane with a partner more than two decades ago and it cost less than many cars. Since then the costs for hangar rent, insurance, maintenance and now fuel have all increased much faster than my ability to easily pay them. So conserving fuel is a practical goal.
In order to retain proficiency, Doug Stewart, an instructor and examiner who conducts safety seminars, suggests that pilots use their $100 hamburger flights as an opportunity to practice airwork and procedures to keep their skill sets honed.
There is some confusion about the efficiency of an airplane. Just because one airplane burns 10 gallons an hour and another burns 12 gallons an hour doesn't mean that the second is less efficient. In comparing fuel burns it's important to consider not only how much an airplane burns per hour, but how far it can go in that hour.
As an example, let's say the June Bug burns 10 gallons an hour and the Bumble Bee burns 15 gallons an hour. Before putting pen to paper, it would seem the June Bug is more efficient; but now consider that the June Bug lumbers along at 100 knots while the Bumble Bee buzzes at 200 knots. If they're both making a 600-mile trip in no wind conditions, the Bumble Bee will set down after three hours, the June Bug after six hours. When the two are refueled, the June Bug will take on 60 gallons but the Bumble Bee will only have burned 45 gallons. At $5.00 per gallon, the faster airplane would actually save $75 on a 600-mile flight compared to the slower airplane. So which is more efficient?
What we're talking about here is "specific range" or "specific air range," which is the distance an airplane can travel for every gallon (or pound) of fuel burned. The June Bug at 10 gallons per hour and a speed of 100 knots has a specific range of 10; the Bumble Bee at 15 gallons per hour at 200 knots has a specific range of 13.333.
It seems you don't have to give up speed for efficiency. Of course, if the Bumble Bee burned 20 gallons an hour, the two airplanes would have the same specific range and be equally efficient. And if it burned more than 20 gallons it would be less efficient.
Another consideration in terms of fuel economy is a function of the quantity of fuel an airplane can carry -- often a tradeoff with payload. Obviously, if it's necessary to make a fuel stop on a cross-country flight, that's going to increase the fuel requirement. So specific range as well as the range of an airplane as a factor of its fuel capacity is another consideration.
On the other hand, if you're only using an airplane to enjoy the feeling of freedom an airplane can offer and not for transportation, then you'd be more interested in the time aloft than the distance traveled, and the less fuel an airplane burns per hour would be the deciding factor. The LSA airplanes, with their typically parsimonious fuel burns might have an advantage if your flights keep you close to home.
During their students' introduction to preflighting an airplane all instructors stress the importance of checking that there is sufficient fuel in the tanks to comfortably complete the flight. But after that first lesson, some instructors assure their students there's enough fuel for the lesson and don't require them to verify it. That can create bad habits.
Another oft neglected instructional procedure is how and when to properly control the mixture. Since most flight training takes place at relatively low altitudes and students are admonished not to lean below 5,000 feet (where engines can develop more than 75 percent power), they don't learn to lean the mixture. And if they do, they're leery about pulling the red knob and tempting fate since they know that's how they kill the engine at shutdown.
