How to reduce flying fuel costs

	With a motorglider’s engine shut down, fuel efficiency is essentially infinite.
	Although the Cessna 172 is a great aircraft, it is not overly fuel efficient.
	Aircraft type affects efficiency. The words helicopter and fuel efficiency should not occur in the same sentence.
	Flying high can not only increase fuel mileage but also avoid airspeed robbing turbulence.
	Many amateurbuilts and advanced ultralights are so aerodynamically clean and fast they boast great fuel efficiency.

The stock market shows the price of a barrel of oil has broken yet another record. Are you feeling it when you top up your tanks for a flight?

If not, read no further as the cost of fuel likely is of little concern to you. Perhaps you operate a big old inefficient twin – like a Beech 18 – and fly it because you love that grand old bird and money is no issue.

For the rest of the readership, let’s look at some of the ways you can save money through efficient aviation. This is a topic near and dear to my heart as I am not only of Scottish decent, but also an efficiency freak.

The challenge of flying a route more efficiently and faster provides a great deal of allure to me and helps to fill the time on a lengthy cross country.

Most aircraft were designed around the concept of fast transportation – not mileage per gallon. As a result, the older designs tend not to be overly efficient.

There are many exceptions to this observation and many of them are sleek amateurbuilts that are fast and efficient. Mind you some of them will have payload and runway limitations, but that’s a different topic.

Since fuel is likely to become the highest cost consideration in aircraft operation, it might be time to consider a change from a gas guzzling twin to a more efficient single. Or from a draggy turbocharged single to a fuel injected version (they tend to be more fuel efficient per horsepower than carbureted engines).

Some turbocharged aircraft can be rather efficient by flying them high where they are designed to optimize fuel flow with higher true airspeeds and potentially strong tailwinds (Airliners essentially fly high for increased TAS and lower fuel flows). However, most turbo pilots do not fly at those relatively fuel efficient altitudes because they don’t like the need to don oxygen breathing equipment.

Our piston engines are typically "fuel cooled engines" in that a portion of the fuel flow is used to help cool the engines at high power settings. These air cooled engines also have sloppier clearances than liquid cooled powerplants to allow for expansion/contraction of parts during temperature changes in these engines with less thermal mass and less effective cooling than the liquid cooled brethren.

OK what can you do? Well, you can consider engines with coolant and better specific fuel consumptions (SFC) like my Rotax 912 powered motorglider. It burns 3.6 U.S. gallons per hour at 106 KTAS at altitude, yielding 34 statute miles per gallon.

A Cessna 150 by comparison would only provide 21 mpg. For the same payload, the Diamond Xtreme is 62% more efficient.

Similarly, more diesel engines are appearing in the marketplace either as new entry aircraft or as STC’s to existing planes such as the Cessna 182. Diesel engines have much higher SFC’s than gas engines and they are now designed to burn readily available jet fuel. With aviation gas slowly disappearing at many airports, Jet A or B is becoming the fuel of choice.

Choices are not limited to single-engine aircraft since the Diamond Twinstar provides the safety benefits of twin engine operation and is quite miserly with the diesel engines. Although not as efficient with fuel, there are some twins that come to mind that provide many mpg’s as well – such as the Piper Twin Comanche.

Although some of the singles have fairly high fuel flows, their ability to fly very fast due to sleek aerodynamics allows them to be efficient because their miles per gallon numbers are quite high.

Mooney’s often fit this category whether normally aspirated or turbocharged. When it comes down to the bottom line, for cross country flying, it is not the hourly fuel flow that matters but rather the miles per gallon.

One handy example of reasonable turbo efficiency is the new Cirrus SR22 which gets 17.8 mpg cruising 199 mph at 55% power. This compares very favourably to an aircraft that is an aviation icon, the Cessna 172. They share the same fuel efficiency; however, the Cirrus carries more payload, goes faster, farther and has a little more pizzaz at the pumps amongst peers. Mind you, what price do you want to pay for looks?

Other than changing aircraft types, there are many piloting techniques that can get you farther on a litre of fuel.

If you need clearances, get them on a portable radio before start up – just as the airlines generally do. If you fly at a congested airport, try to aviate when it isn’t busy to avoid long lines awaiting departure – or landing.

After start up, taxi with the mixture leaned somewhat as this will reduce fuel flow and lead deposits - consult your Pilot Operating Handbook (POH) for details on your engine.

After take off consider climbing to a higher cruising altitude where less fuel flow in a normally aspirated engine results in higher cruising speeds in the thinner air and increased mpg. Check to see if your engine can be leaned in the climb when you use a cruise climb technique.

Chose your altitude for cruising, taking the winds into consideration to optimize mpg’s. Climbing higher into a stronger tailwind can really help and sometimes staying lower to avoid a stronger headwind aloft is the best choice. Make sure you work out the numbers because you may be surprised to learn the reduced fuel flow at altitude makes it worthwhile to fly in somewhat of a headwind.

During the climb, constantly monitor your groundspeed as you may find an aerial river of winds that are favourable at an intermediate altitude. Of course, you must do this while looking for other aircraft, following Nav Can directions and flying the aircraft. This is likely a lot easier than driving a car on a busy highway while talking on the cell phone, drinking coffee whilst looking at a business report for reference – and safer too!

I use this technique on all climb outs and it’s quite surprising to see wide variations in wind directions. By the way, when you are noting the Ground Speed (GS) you should be mentally comparing it with TAS as that is naturally increasing with altitude at a given power setting.

So, if your GS is say 150 knots at 4,000 feet and the same at 10,000 feet, you may have had some tailwind at 4,000 but the higher altitude will yield a lower fuel consumption – assuming a naturally aspirated engine which will now be producing maybe 65% power at best. Therefore, mpg’s will be much better up higher.

Another benefit of higher altitude cruises concerns turbulence. Not only is the bump and grind deleterious to your riding comfort, the yawing, pitching and rolling also sheds airspeed due to increased drag.

When coupled with the over-controlling most pilots manifest and the resulting control surface deflections into the slipstream, turbulence can easily shed 5-10% of the aircraft’s cruising speed and this translates to lost miles per gallon.

Loftier flights can often overfly convective altitudes and areas with mechanical turbulence and sometimes it will be more effective to fly in smoother air with a modest headwind than endure the rough ride.

After leveling at cruising altitude, be sure to follow your POH (and perhaps even reference the engine manufacturer’s available data) to set the optimum mixture setting. Depending on engines and installed instrumentation this may be rich of peak, at peak or lean of peak on the exhaust temperature gauge.

The latter will result in a slightly reduced IAS/TAS, but will likely increase mpg’s significantly. There are a lot of arguments about running fuel injected engines lean of peak with respect to damaging them due to high temperatures and detonation etc. However engines which are designed to operate on these lean mixtures derive no harm and in fact lean of peak results in lower EGT’s.

Again, be sure to check your POH and update information from the engine folks. An average number for increased fuel efficiency with an engine leaned as opposed to running full rich is 20% fuel flow reduction.

With some engines running lean of peak, this can be much higher – even more than 50% reduced consumption compared to running rich – which some pilots do in the mistaken belief it is better for their engines.

In fact, rich running is very hard on engines – but, that’s another article and one I published in these pages years ago.

Burning less fuel per mile on a trip has a host of other advantages that go beyond simple economics. Reducing fuel flow allows the pilot to go further on a tank of fuel or reduce the fuel load and carry more payload. It may also mean the ability to overfly an intermediate fuel stop and this greatly reduces en route time while increasing fuel savings as a lot of the go juice is wasted/used on decent, taxing, take off and climbs that are unnecessary and they are generally flown at rich mixture settings.

When purchasing a new aircraft consider long range tanks to increase your range and minimize en route stops even more. Additionally, this will allow you to more often fly to a broader selection of airports that may have less expensive fuel.

The price per gallon can be a major factor and it pays to shop around and organize your flights to stop at airports with lower fuel prices. Often landing fees and other "use" taxes and fees are buried in the gas price so be sure to shop around for best values.

During the cruise portion of your flight utilize GPS tracking to fly as direct as possible (and watch for other aircraft coming the opposite direction on the direct track while you are navigating precisely).

When I climb out on runway heading I usually press direct on the GPS a couple of times to make a direct track from my current location in the climb out so I am flying a slightly different track than those fixated airframe drivers who are going from one airport center or nav aid to another. Some extra safety consideration.

Also, don’t forget to carry maps of your flying area because GPS receivers can fail!

While many pilots fly as efficiently as possible from start up till the cruise portion of the flight is completed, very few continue with efficient practices.

For VFR operations, the best way to plan the decent and airport arrival begins with the practice of calculating the commencement of the decent. To be effective, one should anticipate a reasonable rate of approximately 300 fpm as this is easier on the ears than 500 fpm or more.

Additionally, power should be reduced somewhat and the engine re-leaned to maintain the planned cruise TAS. Many pilots leave the power up and lower the nose and pick up extra speed for this segment, but with extra speed comes extra drag and less efficiency. It’s better to pull the power back a modicum and reduce the fuel flow further for the approach.

Additionally, for some high performance aircraft, it is rather difficult to get them slowed down if one doesn’t plan to start the decent early enough and this can be hard on the engine with the aircraft at high speed and the power at idle for super cooling the engine.

Moreover, without advance planning, these pilots are often extending the gear, dive brakes or flaps to bleed off speed and this is just plane wasted energy.

So, plan to arrive at the circuit at a power setting that provides the desired speed in the portion of the circuit you are joining and that automatically causes this speed to occur as you level off at circuit altitude. This isn’t easy to accomplish the first few times, but you will develop the skills.

Plan to land on the runway at a position that will allow you the shortest taxing distance to your destination point – with due consideration to safety and runway length.

Sometimes owners find their aircraft is slower than other similar models. There can be many reasons for this. They include the possibility of a twisted aircraft as a result of an accident or even miss-rigging of control surfaces that are creating trim drag as they are extended into the slip stream.

You may also find your plane flies faster when it is slightly out of trim due to the way the relative airflow impinges on the aircraft – many helicopters exhibit this phenomenon and a few fixed wings I’ve flown do too. Mind you, in some cases this could be miss-rigging of the needle and ball etc.

Other culprits include faulty fitting gear doors or flaps not fully retracting, bad cabin door seals, an abundance of external antennae or issues related to the smooth flow of cooling air and its exit from the cowling.

For instance on some of the 120-140 series Cessna, there is a little bent lip on the bottom cowl trailing edge that acts as a venturi to help speed up exiting cowling airflow to free stream speeds. If this is missing (and it often is) the exiting airflow will be at a considerably lower exit speed creating additional drag.

A slower airplane may also be caused by engine issues, some of which will reduce not only power output but also efficiency. An example would be leaking induction system plumbing that would create mixture issues or fouled plugs (from inadequate leaning perhaps) that lead to higher fuel flows and less mpg.

Remember to lean aggressively on the ground since the engine is running very rich and you can’t run it too lean in a damaging way at such low power settings. Not only will fuel be saved, but so will your plugs and rings from harmful lead deposits.

There are several reasons not to automatically fill fuel cells. The primary reasoning for topping tanks historically has been to fill the air spaces within to avoid condensation when the area cools and thereby precipitating the water vapour into the solution and adding water to your fuel. Valid point, but…

Many flights are short and carrying 80 gallons of avgas to fly for less than an hour is inefficient and counterproductive – for several reasons. If you fill the tanks to the brim as is the custom of many pilots and if the aircraft is then parked in the sun or put in a warmer environment, that fuel will expand and with nowhere else to go will be pushed out of the tank vents onto the ground. This can result in the loss of several gallons of gas – and a fire hazard!

Moreover, some aircraft parked on sloped ground with the fuel selector left on will siphon fuel from the high tank into the lower tank and out the vent and depending on the slope this can result in a large loss. So, if you really need full fuel for a flight, fill up just before departure.

Another reason for not tankering fuel is the additional fuel burn to accelerate the additional mass to take off speed, the reduced rate of climb and higher duration at that high power setting and the extra fuel required just to carry the extra gallons along. This all adds up to much less efficiency.

There are so many ways to reduce flying costs associated with fuel and other factors that one simply needs to be thinking during a flight to accomplish considerable cost reductions.

Getting ATIS and clearances on a portable radio before start up will save running time/costs, taxiing and taking off at times the airport is not busy and lined up will also be winning techniques.

If you must climb out to a given altitude on the wrong heading, maximize the rate of climb so you can set course ASAP and if you are anticipating tailwinds at your cruising altitude, continue with the maximum ROC within engine cooling limitations.

Plan your descents well in advance so you can reduce power (fuel flow) in an advantageous manner. Too many pilots leave it to late to descend and end up honking the throttle closed and enriching the mixture while flinging out wheels and flaps to create extra drag to get down to circuit altitude.

My plan involves planning the descent at my cruise speed with a small power reduction that yields a rate of descent in the 300 fpm range (easier on everyone’s ears), re-leaning the mixture for that power setting and planning it so I arrive at circuit altitude at that power setting and letting the speed bleed back to the desired downwind speed.

This technique avoids super-cooling the engine, promotes fuel flow efficiency and minimizes ear popping.

Wish I could claim omniscience on everything aviation; however, let’s just say my tastes in 2001 led me to an efficient wing planform, sleek, low drag airframe and a miserly, fuel efficient engine that burns car gas.

Not only is unleaded autogas more friendly to the environment, it is much cheaper – especially if you burn the marine version without road taxes. In this vein, some commuters who fly a lot in a given year might want to consider an efficient amateurbuilt, a sleek advanced ultralight or some of the more efficient certified aircraft – often composites.

Even Cessna has gotten instep with consumer demands for efficiency and not only designed their own composite two place, but also bought the Columbia series.

Aviators should consider that fuel is only one of the costs of aircraft ownership/operation. Dollars can be saved in many overhead costs such as hangarage/tiedowns, insurance, maintenance and aircraft selection by shopping around and researching all of the true costs associated with aviating.

There are many actions a pilot can take to reduce fuel flow and minimize the cost of flying and when a pilot efficiently utilizes all of these techniques it is possible to conceivably reduce fuel costs by 50% or even more in some instances.

There is no doubt that the surging gas prices are going to create changes in market dynamics. It is very likely that twins with high fuel flows are going to see steep depreciation in coming years and fuel efficient aircraft are going to be in demand and increasing their value in the marketplace.

For aviators flying an "average" aircraft with a fuel flow of 8 gph at cruise and a TAS of 130 mph you can expect to see a broad range of fuel costs. A pilot flying short trips in a worse case scenario can expect to pay 69 cents a mile for his fuel whereas the long range flyer practicing a broad spectrum of pilotage techniques could get the cost below 37 cents a mile. The choices are yours.

Incidentally, the fuel cost on my motorglider is currently 15 cents per mile – and that’s only when the engine is running which is considerably less than half my flight time. Mind you, since I start and end my flight at the same airport most of the time, some might argue that I am getting nowhere and that my fuel is infinitely expensive. Fuel costs can also be a matter of perspective.