3Sixty

3Sixty

Fuel For Thought

Will pumping jet fuel into your car make it fly like a Formula One race car (or plane)? In this issue, Captain Lim Khoy Hing dissects the issue of fuel. 

Jet Fuel & Your Car

Unless you drive a diesel car, putting jet fuel into your tank will likely result in a stalled engine! That was what happened to several drivers when they refueled at a gas station in New Jersey, USA. Apparently, a fuel truck had accidentally delivered jet fuel instead of normal gasoline to that particular station.

     Some still erroneously think that using jet fuel in cars will greatly enhance performance just because a jet can cruise at around 500 miles per hour! Amusingly, this is one of many myths surrounding the use of jet fuel and aviation gas or ‘avgas’, which is used by piston-engine propeller planes.

Pilot-Perspective-Fuel-For-Thought-Air-Asia-AirAsia-Travel-3Sixty-Travel360

The truth is, jet fuel is basically kerosene, closer to the regular old diesel fuel. As such, you would be able to run it in a diesel car, although it would not lubricate the fuel system as normal diesel fuel would.

     On the other hand, smaller flying club piston planes such as the Cessna 172 use avgas that normally has a very high octane rating (a standard measure of fuel performance) – often around 100. You can use this for your car, but it has only a little advantage: Helping to stop premature detonation (knock). However, this would require modifications to the carburettor or injector settings. 

Fuel To Fly

Airplanes consume a lot of fuel, which is one of the reasons why the supersonic Concorde was a failure. An airline’s survival, just like any other business, depends on making profit – ensuring costs do not exceed revenue. However, with fuel prices escalating, many legacy airlines are on the verge of bankruptcy or forced to merge in order to stay afloat. Low cost carriers find it easier to thrive because of their operating philosophy. 

     Airplane fuel is seldom measured in litres or gallons, but rather in kilogrammes or pounds for obvious reasons. When flying, it’s easier to work with weight. For instance, I would request 50,000 kilogrammes of fuel to Melbourne from Kuala Lumpur on the A330 aircraft instead of 16,202 gallons. This is because it’s easier for me to work out weight restrictions, for example, whether the plane can take off safely without exceeding the maximum allowable take-off weight.

     Let’s look at this from another angle. A Boeing 747 consumes about five gallons of fuel for every mile flown. This looks very bad when compared to say 25 miles per gallon achieved on some cars on the road. However, if you consider that a Boeing 747 can carry 500 passengers on each flight, it actually gets four times better mileage per passenger as opposed to a single-passenger car! With a bigger Airbus A380 carrying a maximum of 800 passengers and a fuel consumption that is comparable to the Boeing 747, the figures would be even more impressive!

     The fuel bill of an airline makes up to about 30 to 50% of its operating costs. That’s why most airlines are very conscious about fuel saving.

     The story making its way in social media circles is that in order to reduce fuel bills, Qantas pilots flying the Airbus A380 super jumbos are being asked to carry less fuel on long-haul flights. As a result, apparently at least two flights were forced to divert due to fuel issues, although the airline insists that there were other reasons for the diversion. In view of such media reports, some passengers have asked me whether pilots carry sufficient fuel for a particular flight, and how they determine how much is adequate.

A Typical Airline Fuel Policy 

Let me explain the fuel planning policy of a typical flight and how conservativeness is factored into the fuel uplift to comply with international regulations.

     For a typical flight, say from Kuala Lumpur to Melbourne, the total fuel carried would consist of the trip fuel plus a certain percentage for contingency. On top of this, it must carry enough extra fuel to redirect to an alternate aerodrome and hold at this airport for an additional 30 minutes in the event of an air traffic delay. Some airports have long taxiways, which would cause a plane to spend more time on the ground; this too would be taken into account.

     Finally, the captain can carry any extra discretionary fuel he considers necessary in anticipation of approaching storm, snow or fog.

Practising Fuel Saving

Airlines strive to save fuel and initiate many steps in that direction. One simple step is similar to the car driving tip of removing any unnecessary heavy items in the trunk or backseat to reduce fuel consumption. The aviation equivalent of this is captured in the saying: ‘The heavier you are, the more fuel you will burn!’ As such, removing unnecessary items from cabins such as galley tables and magazine racks, reducing water uplift for short sectors, as well as taking only necessary fuel for the flight would be the smart option.

     Operationally, pilots have been trained to fly efficiently with minimum drag (air resistance) during approach to land, delay the start-up of the auxiliary power unit and use minimum reverse thrust  consistent with safety after landing. Such are the fuel saving measures being encouraged.

Sharklets To The Rescue

In AirAsia, the low cost carrier moves one step ahead of the rest by being one of the first airlines in the world to introduce the new Airbus A320 with sharklets on their wings. The purpose is to enhance the amount of cargo that the plane can carry and increase the range performance by adding an extra 100 nautical miles range and a payload capability of up to 450 kilogrammes.

Pilot-Perspective-Fuel-For-Thought-Travel-3Sixty-Travel360-Air-Asia-Airasia-Airbus-A320

The new AirAsia Airbus A320 with sharklets on its wing tips.

The sharklets are so-called because of their resemblance to a shark’s dorsal fin. The inspiration for the design came from large birds such as the crane, which curls its wingtip feathers upward, greatly improving its energy efficiency in flight. Sharklets not only improve fuel efficiency but also climb at a steeper angle, which reduces noise emissions in the vicinity of an airport.  

     Upon receiving the new planes from Airbus, Tan Sri Dr Tony Fernandes, Group CEO of AirAsia said that these new wing tip devices would contribute towards fulfilling the airline’s goal: To be the most efficient and innovative low cost airline in the world.

“The sharklets are so-called because of their resemblance to a shark’s dorsal  fin. The inspiration for the design came from large birds such as the crane, which curls its wingtip feathers upward, greatly improving its energy efficiency in flight.”

Running Out Of Fuel

On January 25, 1990, Colombian airline Avianca’s Boeing 707 ran out of fuel and crashed in JFK Airport near New York. It had been in a holding pattern for over one hour due to a heavy thunderstorm and winds interfering with smooth arrivals and departures into the airport. While holding for the weather to improve, the aircraft was exhausting its reserve fuel supply, which would have allowed it to divert to an alternate airport in Boston.

     The accident investigation board determined the main cause of the accident to be pilot error as the captain never declared the fuel emergency to the air traffic control (ATC). Apparently, one of the causes cited for this accident was language difficulties – not using the proper terms when communicating distress.

Pilot-Perspective-Fuel-For-Thought-Travel-3Sixty-Travel360-Air-Asia-Airasia-Jet-Fuel-Pump

The fuel bill of an airline makes up about 30 to 50% of its operating costs. That’s why most airlines are very conscious about fuel saving.

     Normally, once the crew has around 30 minutes flying time left, they must declare a ‘PAN PAN!’ call three times. The ATC will acknowledge such distress calls as they are international messages requesting priority over other aircraft. This would be followed by a ‘MAYDAY!’ call three times in very dire emergencies, such as less than 30 minutes endurance left; immediate landing clearance will be given to the plane. In the Avianca accident above, the Spanish speaking captain neither declared a ‘PAN PAN!’ nor ‘MAYDAY!’ call, which would have made a huge difference.

Conclusion

I hope that this article has corrected some commonly held misconceptions. Knowing what you now know (of course, after reading this article), you will understand that the pilot will have carefully plotted out the optimum amount of fuel to carry in order to transport you safely to your destination. It is a fine balancing act, but we do it on a daily basis – so much so, that it has become second nature. Rest easy and fly safe!

Captain-Lim-Khoy-Ling-Pilot-Perspective-Travel-3Sixty-Travel360-Air-Asia-AirAsia

Captain Lim Khoy Hing is a former AirAsia Airbus A320 and AirAsia X A330/A340 pilot who also used to fly the Boeing 777. He has logged a total of more than 25,500 flying hours and is now a Simulator Flight Instructor with Air Asia X. In his spare time, he shares his opinion on aviation issues with others. For more air travel and aviation stories, check out his website, ‘Just About Flying’ at www.askcaptainlim.com.

RESOURCES: