Sometimes, I think there are pilots who do not understand the relationship between speed, building time, and money. Especially those with only a bit of flight time in their logs. They need to build time; yet, they fly their cross-country training flights at 75 percent power and proclaim a “need for speed.”
The idea that airplanes are supposed to go fast is one part of why inexperienced pilots fly too fast. Another part comes from low-time flight instructors who have not figured it out yet themselves. It is not until the low time pilot or new flight instructor goes out, buys an airplane—, and consequently, becomes responsible for the fuel bill, do they realize the importance of proper flight planning and cruise speeds. I was no different—I had to become responsible for the fuel bill to fully understand.
With just a little math, here is the difference between cruising right and cruising wrong.
Using basic numbers, a Cessna 172 at 75 percent power consumes 8.4 gallons per hour (gph). If the pilot flies the airplane at 55 percent, consumption drops to 6.2 gph. In context of cost, at $4.95 per gallon, the 8.4 gph amounts to $41.58 and 6.2 gph is $30.69 for a difference of $10.89 per hour.
Now, for a private owner who flies his or her airplane 250 hours a year, that is a savings of $2723. Another way to look at this is for the same amount of money required to fly at 75 percent, the owner can fly the airplane an additional 89 hours at lower power settings.
Some pilots will argue the reason for flying is to save time. True, but you don’t have to fly fast all the time. There are times when the clock has to be beat; there are times when you can scoff at the clock and enjoy the ride.
Here is something else to ponder: how much time do you actually save? For example, consider Al Mooney’s fast little cruiser, the M20J. With a Lycoming O-360 on the front end, 75 percent cruise yields 12.5 gph at 7500 feet at ISA at best power. At the same altitude, 55 percent delivers 9.3 gph. Cruise speeds are 164 @ 75 percent power and 144 @ 55 percent. For a typical 300 nautical mile trip, the flight times are 1+49 and 2+05 respectively, a difference of only 16 minutes.
The cost in fuel, at an average of $4.95 a gallon, is a difference of $15.84—too high, for saving only 16 minutes of time. Personally, I would leave 16 minutes earlier to save the almost $16 in gas.
If you take this to a higher level of thinking and apply the savings across the life of the engine at 2000 hours, you would save a total of $31,680. That alone, would pay for the cost of the engine’s overhaul. Now, take it a step further and consider operating a small flight school with seven aircraft. Total savings with the fleet for the life of the engines approaches $225,000. A large flight school or other company operating 100 airplanes could save more than $3 million.
Pilots I have talked with about this sometimes say, “But I have to pay by the time, not the fuel.” True enough. However, this is what I refer to as “rental car mentality.” (Not my car, I don’t have to take care of it!) By using higher power settings, the FBOs and flight schools have to buy more fuel so they are losing the money, right? Actually, they are not; they simply pass the costs down to the renters in the form of higher rental fees. And like most pilots, I object mightily to higher rental fees.
Think about the benefits of flying a little more slowly, saving gas, and enjoying the ride. On the next post, I will explain the difference between max endurance and max range.
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©2011 J. Clark
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Very nice, Joe. Here’s some trivia for you. Increasing speed to minimize the effect of headwind is sometimes a good idea in the fastest aircraft (jets) and the slowest aircraft (sailplanes). A jet, fighting a 100 knot wind can actually save fuel by minimizing the time it is subjected to the slower ground speed and a sailplane can increase the glide distance by penetrating the headwind as quickly as possible. Neither of these situations have anything to do with your discussion, but as painful as it is, you made me think. Another time to fly faster to save fuel is when you’re holding and limited to the maximum hold speed for your altitude. By asking ATC to approve a higher hold speed (230k as opposed to 180k) you can avoid the use of flaps and slats. Of course, the turn radius of the pattern now covers half of Texas, but traffic permitting, it saves fuel. Again, it doesn’t apply to your topic, but thanks for booting my brain this morning.
Harrison, you bring up good points for future blogs – especially the idea of staying out of headwinds as much as possible and riding the tailwinds as long as you can. Reminds me one great trip back from California in an A-7 – with a 175 knot tailwind! Faster than 700 knots across the ground! Oh to have a tailwind with every flight… 😉
Joe, I love this post. Flying, as most have come to find out the hard way, is expensive. It’s unfortunate that such a great hobby has to cost so much. The “need for speed” is a cliche that is all too often used as an excuse. Keep the posts coming and have a great Christmas!
Jay, glad you liked the post. Sometimes, there actually is “a need for speed,” but I have yet to corner couple of Migs in my part of the sky that I needed either to dispatch or bug out from during the fight–while tooling around the air in my trustworthy ol’ Cessna 170. You and your wife also have a very merry Christmas and be safe if you’re traveling.