April, 2008

Some "fuelosophy"

The price of fuel is at an all time high. Locally the price for 100LL avgas is running on the high side of the $4.00 to $5.00 range, and I'm sure some places are charging more than that for the precious stuff. So what can the poor pilot do? Anything at all? Or is the "hundred dollar hamburger now going to be called the "two-hundred dollar hamburger?" Herewith are some of my thoughts that may help you make your own fuel dollars go a lot further, based on the concept that reducing your cost is best done by your reducing fuel consumption.

How much fuel weight are you carrying?

I remember it as clearly as if it happened yesterday. The year was 1982 and I was working on my Commercial Pilot's License. A fresh Instrument Rating was in my pocket, and since I had the time and still hadn't run out of money I had decided to go for the commercial ticket. Kevin Curley, my CFII, had gotten me through the instrument rating, and now he was getting me started on the commercial certificate. On this day we were getting an early morning start after breakfast at the airport cafe, and Kevin was carefully evaluating my preflight inspection of the big Cessna 210. Noticing that the fuel was down a little, I told him we needed to head for the pump. Kevin asked, "How much flying are we going to do today?" "About an hour and a half, give or take," was my response. "Do you have enough fuel for that?" he asked. "Sure, there's at least 45 gallons in there." I knew, because that calibrated stick was accurate. "Then why would you want to carry around a bunch of unnecessary fuel? That costs money and it detracts from the airplane's performance!" Kevin pointed out that if I were a charter pilot I could be faced with having to haul only three guys:but maybe they're all fat, with heavy bags, and one might bring his Black Lab along for the ride! "Now if you started with your tanks topped up you wouldn't be able to carry them! What would you do--drain out some of the fuel that you just put in?"
"Black Gold" (Oh, how we wish it were cheaper!)

Time for a reality check

Welcome to the real world! This was the first time I had ever been forced to think of the subject of carrying fuel in those terms. But that's exactly what REAL commercial pilots have to think of every day, for every flight. So why do they teach us in primary flight instruction to top off the tanks after every flight? I suppose it's so they don't have to do it, and so they won't have to worry about some inexperienced student pilot running out of gas. But for me, ever since Kevin's remarks, I have tried to MANAGE my fuel, rather than just fill it up every time I land the airplane. In fact, I have given a lot of thought to the amount of fuel I carry, especially with the high density altitudes we have here in the Southwest. Unfortunately, while a lot of designers and builders are thinking about fuel capacity also, they're usually thinking along the lines carrying more fuel, rather than less! As a rule of thumb each extra 100 pounds you are carrying penalizes your fuel mileage 1 to 2 percent. Carrying anything unnecessary hurts your mileage. Plus, we all know that your airplane will turn in better performance on the ground, taking off, climbing and crusing, with lighter gross weight. Doesn't that sound good? I thought so!

An "aside"--Fuel and bladder considerations

It's kind of funny if you think about it--we go to great lengths to keep our aircraft weight down, and then we tank up with twice as much fuel as anyone on board can physically endure! We take off with brim-full 50 or 60 gallon fuel tanks, subjecting other passengers to an extremely long and boring (for them) cross country odyssey. A stop for fuel and to stretch, use the restrooms, etc. would be a welcome respite for them! In addition to consideration for the well-being of our passenger, we all know that too many hours behind the wheel (or the yoke, or stick) without a break can cause the kind of fatigue that in turn causes accidents. Goodness knows, a too-long day of flying can transform the most handsome pilot into a crab, even if the flight went well! So for that and other reasons (economy, structural considerations, etc.) I recommend planning for a reasonable flight, say three hours worth at cruise power, which is a pretty long flight between fuel stops for many passengers, especially kids. If you insist on putting others through hours and hours of what for them is sheer boredom, often noisy and somewhat intimidating, I can only warn you that you'll "lose" them at some point. Because when the day comes that you can no longer order them on board for another grueling trip, and when you want to take a short flight with that precious son or daughter just for fun, chances are they will make an excuse and opt out. In fact, I wonder how many "would-be pilots" we lose that way? This reminds me of the effect of "maneuvers" on passengers who are not used to flying. Please--Resist the urge to demonstrate your daring and skill at stall recoveries and steep turns on their first flights!
Aircraft Performance Chart (sample)
Pwr Stg (SQ)%PWRFuel (gph)Max Range (nm) TAS (Kts)

Power settings versus fuel burn

Your most helpful guide to saving fuel with your own aircraft is found in the Aircraft Performance Chart section of your Pilot's Operating Handbook (POH) if you have one. For newly built homebuilt aircraft, you should develop your own performance chart as you gain experience with various power settings. For purposes of illustrating how you can save fuel, I have reprinted above a set of hypothetical power settings for a homebuilt, two-place aircraft with fixed gear and a constant speed prop. As with any other such hypothetical chart, "Your mileage may vary!" (So will speeds, climb rates, etc.) Remember, this is only an illustration, not a performance chart for your airplane! This Performance Chart shows that changing your power settings can result in fuel consumption ranging from 6.9 to 10.4 gallons per hour, or $35.00 to $60.00 per hour, with a Lycoming O-360 engine (180 hp). That is a dramatic range of fuel burns! Obviously if you are just out sightseeing or if you're not in any particular hurry, you can set 2,200 rpm and 22.0 inches of manifold pressure and "putt along" at a nice easy speed of around 135 mph (117 knots)! At 50 percent power you'll save 3.5 gallons of fuel per hour compared to the customer 75 percent cruise power setting. Your dollar savings? Oh, approximately $15.00 per hour at today's fuel prices, $150.00 for ten hours or flying. That is a considerable saving! Even at 60 percent power rather than 75 percent power, you will save close to $10.00 per hour while cruising at nearly 160 mph (138 knots). And remember, in addition to dollar savings you will be helping to conserve an important resource.

Don't be too hasty on climbout

Another fuel savings trick is to carefully consider your rate of climb. You should always set and maintain the aircraft's best rate of climb speed at full power immediately after takeoff (or best angle, if ground obstructions exist), but you don't need to keep that up forever! Once you turn out of the pattern you can lower the nose a bit to get some extra miles out of that throttle setting. Better yet, reduce your manifold pressure and throttle settings and accept a slower rate of climb. Remember, there isn't any FAR (Federal Aviation Regulation) that tells you how fast you must climb to altitude! If you don't run in to something while climbing out, the Air Traffic Controllers are pretty happy, no matter what your rate of climb. Managing your power on approach is also important. If you have to deploy your flaps early on during your approach in order to avoid overshooting the touchdown zone, Congratulations! You have just wasted some more fuel! You would be better off to have throttled back and slowed down a bit more early on during the approach, even if you have to add back a little power later to make the field.

What works in the air, works on the ground!

Managing your power settings to save aviation fuel really works, I guarantee it. And the same can be said for your car! Remember, wasting fuel is wasting fuel, whether it's your lawn mower, airplane, car, or gas range. The worst automotive fuel-wasters are "jackrabbit starts" and screaming along at high-speed cruise until you're so close to the next red light that you have to jam on your brakes. Instead, you should practice slower acceleration, more moderate cruise speeds (like maybe obeying the speed limits for a change!), and looking way up ahead to avoid sudden stops. If you lower your cruise speed from 70 mph to 60 mph, you can expect a sizable fuel savings. I know this to be true from my experience, as I have recently reduced both acceleration rates and cruise speeds in my pickup truck and my Harley Davidson. The fuel savings have been dramatic with both vehicles! Now I can hardly wait to try some of my conservative fuel management tricks in our RV, which ordinarily slurps plenty of fuel. I have found that RV owners can be notorious liars when it comes to telling others how little fuel their particular rig burns. I have heard low fuel consumption figures that I don't believe could realistically be achieved unless the entire trip were made at 25 mph, with a tailwind. I chalk it all up to wishful thinking, or to their inability to perform mathematical calculations correctly. We are leaving on an extended RV trip in a couple of weeks. Rather than scrub our travel plans due to high fuel costs, which was our initial inclination, we plan to offset the increases by saving the amount of fuel burned with the tricks I have been practicing. That and saving money on our campground fees. We'll still have just as much fun, I am sure, and I won't have to lie later on about how great our gas mileage was, I'll just tell them how much we reduced our fuel consumption. That'll wow the guys and gals out there!

Fuel in the Celerity and Marathon

Larry Burton built the prototype Celerity with slightly over 40 gallons fuel capacity. It's a fuel quantity that fits the airplane, the engine, and most missions very nicely. Larry's Celerity had tip tanks that held over 15 gallons each, and an auxiliary tank out near each wing tip. The new leading edge fuel tank design works well also, furnishing enough room for 40 gallons of fuel in the Marathon. Leading edge fuel tank capacity in the Celerity is approximately 30 gallons due to space restrictions caused by the retractable gear wheel well. To carry more fuel in the Celerity, auxiliary tanks must be added. With 40 gallons of fuel on board you have about 740 miles range at 75 percent power, plus 45 minutes of fuel in reserve at the same power setting. Reducing power to 60 percent will give you approximately 55 to 70 miles greater range on full tanks, and you'll be able to stay in the air somewhat longer before refueling, all of this at an approximate 20 to 25 mph speed penalty. This isn't too bad a trade-off, with the price of fuel as high as it is right now. Some builders prefer to use autofuel in order to save money. I would guess that you can save more than a dollar per gallon with autofuel. There have been some reported problems with certain engines or carburetors due to the ethanol content of autogas (oftentimes "winter blends") and also some reported vapor lock, so be careful. You can also shop fuel prices using the Internet and plan your fuel stops accordingly. I found 100LL fuel prices ranging from $4.30 to $4.88 per gallon in this part of Arizona yesterday. That could mean a savings of $20.00 or so on just one fill-up of avgas! Sounds good to me.

Model airplane mystery solved, thanks to Gary Briley!

We ran this photo recently in our newsletter, and I wondered if this thing was really meant to fly. Or could it be just some twisted Internet geek's little joke on the rest of us? I encouraged any of our readers who might know ""the rest of the story" to fill us in on this project. Gary Briley promptly emailed me with the answer to my question:a reference to a YouTube video of this airplane in flight. I viewed the video and I must say, this thing in flight is very impressive as the model sounds and looks exactly like the original, full size U.S. Air Force B-52 bomber. All I can say is, "WOW!!!"

Inspection hole covers

Shown is one solution to the inspection hole cover problem, as seen on Celerity N180JG, Jim Glencross' project that is being prepped for flight by Don O'Rourke. This type of inspection hole provides six screw anchor points and is a nice lightweight solution.
Ready? Almost, but not quite!
Jim Glencross' Celerity N180JC is getting close to regaining flight. New owner Don O'Rourke reports that landing gear maintenance and testing are coming along. Significant time was recently spent removing the Molex type wiring connectors that Don had installed when reassembling the aircraft, as he was not happy with their performance. Seems like there's always something that crops up when the weather is beautiful and you are anxious to launch an airplane project into the air! But like Don says, "The airplane will dictate when it's time to fly!" This is an excellent attitude to have when you're "getting close" with your own project.