Ask Captain Lim ~ All about Aviation

Dear Capt Lim,

What is the fuel consumption per engine of your huge Boeing 777? I am very fascinated by whatever statistics you tell me. I like facts and figures. Does it use kerosene? Why kerosene, and not diesel ? Does kerosene have more energy density than diesel? The engines must be tremendously powerful. I once read that a passenger bus parked behind an Air India airliner in New Delhi airport was blown away when the pilot applied power on the engines (accidentally ?) Just fancy that !

How much fuel does a Boeing 777 use? Years back when I was traveling in the older Boeing 707, I read in the leaflet left behind the seat in front of us. It was a very short one page non-technical description about the plane we were in. The leaflet stated that the Boeing 707 uses 40 gallons of kerosene per minutes per engine. Wow ! a whopping 40 gallons per minute per engine, I said to myself. I was absolutely thrilled by that figure. I was impressed by the thought that a plane must be carrying tons of kerosene to last hours of flight. I do not know if it was the US or the British gallon, and if it was the ordinary kerosene found in our kitchen, or was it a special grade aviation kerosene ?

Regards,
Dr Lim Ju-boo.

Dear Dr Lim,

I was trying to retrieve some information regarding the old Boeing 707 you referred to but I was unable to get or verify the fuel consumption figure. You told me you got the value on the leaflet at the back of the seat and I take it to be correct.

You know, I am rather surprised to note that the Boeing 707 was so fuel inefficient, 40 gallons per engine per minute! The Boeing 777 consumes only 14.4 Imperial gallons per engine per minute but carries about 300 passengers whereas the Boeing 707 carries only 141 passengers! So the Boeing 777 is 2.77 times more fuel-efficient and carries 2.1 times more in passenger load as well!

You are right! The Boeing 777 jet engines use kerosene that is almost similar to those that you find in the kitchen. However, the kerosene used by jet engines are more specific and given names such as Jet A, Jet A-1 or JP-8 because they contain mixtures of anti-icing additives to prevent fuel from freezing in very cold and high altitudes. I am not an expert in fuel technology but I believe kerosene has higher octane ratings than diesel or more energy density as you have described.

The Boeing 777 has two very powerful Rolls Royce Trent 892 engines with a maximum thrust rating of 90,300 lbs thrust each that can lift off the plane with a maximum weight of 632,500 lbs compared to a Boeing 707 with a weight of 336,000 lbs.