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Home > Flying on the Boeing 777 > What is the fuel consumption of a Boeing 777 as compared to a Boeing 707?
What is the fuel consumption of a Boeing 777 as compared to a Boeing 707?
Flying - Flying on the Boeing 777
Tuesday, 11 December 2007 20:47

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.

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That 40 gallon/minute/engine figure MUST have been on takeoff... After all, back then we were impressed with big numbers, not efficiency.

Even though the 707 carried a large swimming pool worth of fuel (nearly 25,000 gallons,) if it burned 160 gallons per minute during cruise, 9600 gallons per hour, it would be out of fuel in 2.5 hours...

The plane could fly at least 10 hours, so I'd estimate that it burned about around 2,000 gallons/hour - a lot less, but still MUCH thirstier than the 777 on a passenger-mile per gallon basis.
Mark , 17 Jan, 2010
Lim Ju Boo science medical health nutrition
Visitors to Captain Lim website are also welcomed to visit my blog at http://scientificlogic.blogspot.com/

and also to Dr JB Lim's Corner at

http://www.askcaptainlim.com/index.php?option=com_content&view=category&id=74&Itemid=89

Thanks. JB Lim
Dr Lim Ju Boo , 23 May, 2010
Calculations
I hope you don't do the calculations of fuel when you're flying. 40 gallons x 4 engines = 160 gallons. 14.4 x 2 engines = 28.8 gallons. Therefore 5.55 x more efficient. Not 2.77
Colin , 23 Aug, 2011
777
hi cap lim what could you tell me about the 777 and its bad and good points of the aircraft size weight fual etc range power and how it deals with crosswinds thank you for any info you may have safe flying sir
alan , 31 Aug, 2011
Mr
Hi. . . higher octane does not mean more energy, it just means a higher ingnition temperature . .
Alan , 05 Dec, 2012
Aorplane engines
I worked for Allied-Signal in the late 80's. They had a Boeing 707 that flew daily from Burbank CA to Phoenix AZ and return on weekdays. I called it the Frankenstein monster as it had three GE turbofan jet engines and one diesel prop engine. Two unique things were the prop was like an egg beater and the tips folded in upon themselves. Also the engine was made of lightweight titanium just like a jet. This engine actually produced about 30% more thrust than the jet ones and used nearly have the fuel. Cheaper diesel no less. And in a fire. Diesel would be far less likely to burn The prop used allowed the egine to continue thrust even past 600 MPH. It is a scientific fact that as the prop tips approach the speed of Mach all thrust is lost. By having no tips to the blades this does not apply. Really, unless planes are supersonic there is no advantage to jet engines. Plus a prop type would not punch such a great hole in the ozone layer as it passed through. About the only real limitation to the diesel prop engine is the altitude would be limited to just over 35,000 feet. But only long hop jets tend to fly that high. Allied signal mainly manufactures Auxiliary Power Units for jets as well as helicopter engines. But they once powered some Greyhound Buses as well as Semi Trucks with turbine engines. Never took hold as they tended to overheat when stopped or in slow traffic. And of course the fuel cost. The one huge advantage to turbine engines as they practically never wear out and are not necessary to tear down to inspect But then that is a quality with Titanium. With the Cold War no more Russia has been making plenty of Titanium available. 20 years ago you would never have found it in golf clubs or jewelery.
Only Russia, South Africa and Afghanistan have titanium ore in quality and quantity to mine. Afghanistan's is not yet developed. Along with Lithium deposits I believe those two deposits are the reason the US is there. And of course the renewable source of opium which has increased by over 400% since the US arrived. War is good business. Mothers invest your children (sarcastically). I am a US Citizen and Vietnam Vet, but do not endorse the actions of its government foreign or domestic. Love to see the rigid return of the Constitution that made America great but could be improved even more simply by not violating it with other laws or illegal actions.
Ron , 23 Jul, 2013
Mr
The 707-300 series burned about 14500 lbs per hour TOTAL at heavy weights at 33000 ft and o.78 Mach cruise. near the end of a 4000 nautical mike trip it was burning about 10,000 pounds total per hour at 39000 ft.
Mike70 , 23 Dec, 2013
question on gallons per hour
Greetings all,

Hope 2014 finds you well.

Please help, I am trying to calculate what amount of fuel in gallons per hour does a B777F burn?

If you could show me the formulae I would be most greatful as I would apply the same formulae 'principle' on any aircraft.

Thank you for reading :-)))

Simba.
simba , 11 Jan, 2014
question

Greetings all,

Hope 2014 finds you well.

Please help, I am trying to calculate what amount of fuel in gallons per hour does a B777F burn?

If you could show me the formulae I would be most greatful as I would apply the same formulae 'principle' on any aircraft.

Thank you for reading :-)))

Simba.
simba , 11 Jan, 2014

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