Regardless of your views on global warming, there are compelling reasons for running a so-called “green” operation — and perhaps the most important one is “greenbacks,” or the money that can be saved through fuel conservation.
The combustion process being directly related to the production of carbon dioxide (CO2) — the gas most faulted for the greenhouse effect that many scientists believe is raising the earth’s temperature if you burn less Jet-A, your engines expel correspondingly less CO2, as well as carbon monoxide (CO), nitrogen oxide (NOX) and water vapor. Moreover, you save fuel, a benefit that goes straight to your operation’s bottom line.
Beyond that, many companies — especially publicly traded corporations — have adopted the green ethic, some because they believe lowering a business’s carbon footprint is inherent to being a good corporate citizen and “the right thing to do,” and others to reflect a publicly positive image. Either way, the upshot is that these businesses are saving significant amounts of money on energy costs, while releasing less CO2 in their operations. In converting their various activities to a green standard, these companies will eventually get to their flight departments, and management will want to know what can be done — if anything — to lower the environmental impact of the corporate aircraft.
The ready answer, of course, is to purchase one of the newest, state-of-the-art business jets since they are powered by engines that use less fuel for a given power setting and emit lower amounts of greenhouse gases (GHGs) than anything previously certified. But these are challenging times and you may have to make the best with the equipment you’ve got for a while longer.
With good maintenance and handling, an aircraft can remain in service indefinitely. Indeed, a significant portion of the business fleet — perhaps your aircraft among it — has been operating for decades with engines designed perhaps 30 years ago, with fuel consumption and emissions figures reflecting the technology and standards of those times.
So, how do you fly green? And as a practical matter, why, since your aircraft might log 500 hr. or less annually?
Because It Makes Sense, That’s Why
“The answer to why you would want to do this,” says Steve Brown, vice president of operations at the NBAA, “is that you are becoming more efficient, reducing your cost of doing business, especially in this economy.” And “with the environmental benefit of being responsible, from the business and societal viewpoint, by reducing emissions.”
Brown added that he doesn’t hear members arguing abut the efficacy of global warming. “Instead they are responsibly managing what they are doing and saving money,” he said, “regardless of how they feel about the science of global warming. It is the unifying business principles that they are interested in.”
For operators of older aircraft, there is a compromise to buying new, greener equipment, and that’s retrofitting with newer engines, installing winglets and aerodynamic cleanups, and swapping aging avionics for more precise digital technology. Of course, this presupposes that these upgrades exist for your machine. Also, it assumes the investment in dollars and downtime make sense, which may not be the case in a down market when excellent, relatively new and efficient used aircraft are available at attractive prices.
Changing the Way You Operate
Irrespective of retrofits, however, all operators can lower fuel expense and carbon footprint by simply modifying the way their aircraft are loaded and flown.
According to Brown, “there are things you can do with the airplane, on the ground, with the hangar, a complete green profile, looking at all your assets and how you manage them.” In terms of operating the aircraft, these options can include:
Reducing discretionary payload. Conduct an inventory of everything routinely transported that can be pared to save weight, all the way down to extra or unnecessary items carried in the galley that can be left at home. Encourage passengers to limit the amount of luggage brought aboard. These may seem like small increments, but they add up.
Limiting APU runs.
When away from base, parking as close as possible to the active runway, towing the aircraft as far as possible, and turning the aircraft to the outbound direction before starting engines.
Or not starting engines until receiving ATC clearance to taxi to the runway. Confronted with ATC delays, obtain revised departure times before engine start.
Taxiing on one engine, if the aircraft and its engines and systems can support this practice (some older types do not). Consult your aircraft operating manual.
Reducing takeoff thrust where possible if flight and conditions warrant.
Optimizing the aircraft’s c.g. to reduce drag (i.e., shifting it aft within the strictures governing safe operation) and, thus, fuel burn. Also, observing proper trim procedures.
Operating at maximum-range cruise power settings. More than any other practice, this is a major fuel-saver.
Being proactive with ATC by filing for the most direct route possible, optimizing cruising altitude, and using the jet stream to advantage wherever possible, and avoiding it where it presents a handicap.
Brown, who oversaw the U.S. ATC system while serving as an FAA deputy administrator, explained that the mandate for controllers is to “only intercede with the aircraft’s normal operation when there is a need to maintain separation. When I file my flight plan and specify the parameters — altitude, cruise speed and so forth — the FAA will not change that unless there is conflicting traffic. They assume what I ask for is my optimum in terms of the available options.”
He claims that 80% of the time you will get exactly what you file for, because there is plenty of capacity in the system. “Only in denser airspace where a number of operators may be asking for the same thing will they give you an alteration to your flight plan in order to avoid conflicts and maintain safety.”
Taking advantage of constant-rate descents (CDAs, an efficiency-enhancing procedure already being implemented in some places as part of the FAA’s NextGen ATC modernization plan) wherever they’re available and attempting to determine top-of-descent points as early in the flight as possible to begin preparation for configuring the aircraft.
Limiting use of the high-flow setting for air-conditioning packs.
Where possible, avoiding tankering fuel. It takes fuel to transport fuel, and unless there is an enormous price advantage to taking much more than you need, don’t.
“Some of these things are situational,” Brown said, “but be aware that you should use them whenever you have an opportunity.”
Also, as part of an overall effort to reduce fuel burn and emissions, you should review how the aircraft is used, that is whether some missions can be consolidated, thereby reducing legs and deadheads. (This is ultimately a management decision, as the flight department exists as a business tool to promote productivity.)
Putting It All Together
At the 2008 NBAA Convention, Gulfstream Aerospace officials presented a study titled “Performance Procedures for Fuel Conservation and CO2 Reduction,” which advanced an intriguing premise: By applying the fuel-saving techniques outlined above, it was possible to fly a G550 with six passengers on a 2,200-nm westbound trip and save 6,986 lb (1,021 gal.) of fuel while avoiding the production of 22,000 lb of CO2.
These savings were predicated on operating the aircraft at a long-range cruise speed of Mach 0.80 as opposed to a maximum cruise of Mach 0.87, removing 500 lb of discretionary items from the aircraft, cutting use of the APU and engine idling time by 30 min. each, and not carrying fuel for the return trip — plus addition of other factors, which we’ll detail further on.
At a California spot market price of $5.08/gal. (including taxes) in late December 2010, this equated to a savings of $5,186.68 in fuel for the trip. Hard to argue with that. A more detailed breakdown of how Gulfstream did it follows.
It starts with flight planning. As its example, Gulfstream posits a transcontinental trip from White Plains, N.Y. (HPN) to Burbank, Calif. (BUR), a distance of 2,200 nm. File for the most direct route possible under the forecast weather conditions and temperatures, planning both lateral and vertical profiles, choose the closest suitable alternates and limit “discretionary” (i.e., excess) fuel. As Gulfstream planners point out, tankering may save you some money, but it never saves fuel. Additionally, the practice is guaranteed to reduce aircraft performance and efficiency in takeoff, climb, cruise, descent and holding. For the trip example, carrying return fuel in the G550 on the outbound leg will require an additional 1,650 lb of Jet-A just to haul it across the country, and blowing 5,200 additional pounds of CO2 out the tailpipes in the doing.
Pulling unnecessary weight out of the aircraft will be at the discretion of the operator — some of Gulfstream’s examples are questionable, such as carrying six 170-lb passengers as opposed to six 190-pounders, leaving one of the pilot’s Jepp cases (40 lb) at home, etc. — but the exercise is still worthy, if significant weight can be saved on a practical level. Using the example of 500 lb eliminated, Gulfstream shows that for a 6,000-nm mission in the G550, 265 lb of fuel and 834 lb of CO2 can be saved (at max-range cruise).
Gulfstream recommends maintaining c.g. in the mid-to-aft range, claiming that shifting c.g. forward 1 deg. for a 6,000-nm mission in the G550 will consume 311 lb of extra fuel. Limiting excessive idling on the ramp and use of the APU is self-explanatory. Ground-idling the G550’s Rolls-Royce BR710s for 30 min. consumes 638 lb of fuel and pumps out 2,009 lb of CO2. For a half hour of APU time, figure 91 and 287 lb, respectively.
If a choice is available, select the closest runway of appropriate length to accommodate the BFL of the aircraft, and accept “reasonable” crosswinds, if necessary. The goal here is to reduce taxi time as much as possible. Getting a tow from the ramp will help toward that end, then taxiing on one engine to complete the trip to the runway completes the fuel-saving exercise. The tug driver should be instructed to turn the aircraft into position before disconnecting, as turning a departure-heavy aircraft under engine power uses more fuel.
Request a rolling takeoff, if the tower will give it to you, to avoid wasting thrust while holding brakes, Gulfstream advises, and depart using “flex,” or reduced takeoff thrust, if runway and conditions permit, to reduce overall fuel consumption. You’ll also be doing your engines a favor in terms of internal temperatures and wear.
Once airborne, things get more challenging in terms of maintaining the green flight profile due to the exigencies of air traffic control. Remember that initial climb speed and flap settings will affect fuel burn. Therefore, straight-out departures are preferable, cleaning up the aircraft as quickly as conditions and safety considerations warrant. If not departing on course and minimum altitude is required before the turn on course, Gulfstream advises the following actions to minimize distance flying in the “wrong” direction:
Maintain flap setting, trade speed for altitude to turn sooner and keep speed low to affect a faster turn rate. With the turn outbound predicated on reaching a navigation fix or assigned position, minimize fuel burn to the fix, clean up the airframe to the minimum-drag configuration and accelerate upon completing the turn.
En route, while it is obvious that the cockpit crew should adhere to the filed flight plan, since it was chosen to promote maximum fuel conservation, the best-laid plans are subject to the priorities of ATC. Maintaining the vertical profile is most critical because altitude deviations often eat up fuel. Consequently, Gulfstream recommends trading altitude changes for lateral deviations. If this is not possible, then attempt to regain flight plan altitudes ASAP following an ATC-directed altitude change. Additionally, monitor winds at lower altitudes and consider descending if winds are favorable in terms of saving fuel.
And Slow Down . . .
“Flying faster yields small time savings compared to increased fuel consumption,” the Gulfstream study admits, arguing for use of long-range cruise (Mach 0.80 for the G550). This practice is probably the most effective tool available to the flight crew to complete a mission in reasonable time at the most efficient fuel burn for the given aircraft. For example, the difference in consumption between LRC for the G550 and Mach 0.87 for a 1,000-nm flight is 1,392 lb of Jet-A, 4,383 lb of CO2 and 8.5 min. en route. For a 4,500-nm mission, the numbers are, respectively, 10,799 lb, 34,001 lb and 45.8 min.
Gulfstream characterizes the continuous-descent approach as “the ideal descent profile: uninterrupted, idle power, clean configuration.” It’s a gift for saving fuel, but flight crews are advised to enter arrival and runway data into their FMS early to optimize the aircraft’s top-of-descent point; maintain the FMS’s calculated vertical profile, as early or late descents waste fuel; and to plan ahead to avoid speed brake use followed by power applications to maintain the descent profile. It’s a challenge, but one with a significant payback if you get it right.
At destination, the optimum in terms of runway selection (if that’s an option) is a straight-in approach to a runway offering a short taxi to the FBO with no requirements to cross other runways or hold short. Gulfstream urges crews to evaluate flying time to a particular runway versus taxi time to the ramp and — as always, if possible — to select a shorter runway, accepting crosswinds, with safety considerations in mind and a visual approach, if available. The runway exit should be evaluated in terms of taxi-back distance versus brake use and use of reverse thrust at idle power in lieu of full reverse thrust. As Gulfstream points out, using idle reverse offers a veritable banquet of advantages: less fuel, and lower emissions, noise, engine wear, chance of FOD and passenger discomfort.
Again, taxi in on one engine, if possible, with the understanding that, with the aircraft lighter at destination, taxiing will require less energy and minimize brake applications. Once parked, limit APU operation.
The beauty of these procedures is that they can apply to any size aircraft. By using a large aircraft like its G550, Gulfstream was able to present some really large numbers in terms of fuel and CO2 savings. But the point is that any flight department can implement these practices into its daily operations, yielding tangible benefits whether it fields the smallest turboprops and VLJs or the beefiest heavy iron.
For it to work, green ops must be made part of the operation’s culture, and everyone involved — company management, flight crews, dispatchers, even the maintenance department — has to sign on to the initiative. While some of the suggestions here may seem niggling — parking close to the active runway, aligning with departure heading, etc. — all of it helps the environment, and your bottom line. So, it’s to your advantage to develop the mindset to exploit them when and where you can.
Gulfstream also recommends that operators maintain accurate records of their flights and track improvements in order to gauge success in reducing fuel consumption and costs. Again, global warming or no, the days of cheap fuel are over, so conservation of what we have left makes more sense than ever before. BCA