Register to reply

Harrier fuel consumption

by chris190
Tags: consumption, fuel, harrier
Share this thread:
chris190
#1
Oct20-05, 07:53 PM
P: 2
Greetings!

Would anyone know about how much fuel does a Harrier aircraft (with the Pegasus Turbo fan engine) consume when taking off verticaly?
I tried searching the net with no success.

Thank You
Chris
Phys.Org News Partner Science news on Phys.org
Apple to unveil 'iWatch' on September 9
NASA deep-space rocket, SLS, to launch in 2018
Study examines 13,000-year-old nanodiamonds from multiple locations across three continents
Clausius2
#2
Oct20-05, 09:29 PM
Sci Advisor
PF Gold
Clausius2's Avatar
P: 1,479
A lot .
Pengwuino
#3
Oct20-05, 09:36 PM
PF Gold
Pengwuino's Avatar
P: 7,120
A lot? Arent you just re-directing thrust? Seems like at the most, it would consume its normal 100% thrust requirement.

russ_watters
#4
Oct21-05, 07:15 AM
Mentor
P: 22,295
Harrier fuel consumption

Since it's non-afterburning, it's probably less than most military jets at takeoff.
Clausius2
#5
Oct21-05, 04:26 PM
Sci Advisor
PF Gold
Clausius2's Avatar
P: 1,479
Saying "A lot" I am not intending to say "A lot more than other jets" (I was just kidding).
surfbum42
#6
Oct21-05, 04:44 PM
P: 2
Here's some help for you. The weight of an empty Harrier is 22,950lbs and it provides 23,800 lbs of thrust from its engines Pegasus Turbofan engine. In order to find the amount of fuel needed to take off you now need to find the amount of fuel consumed in order to acheive >97% of it's maximum thrust. I think that it is correct so maybe it should help you. Now all that you need to do is find out how much this Pegasus Turbofan engine fuel consumption at 97% is to acheive liftoff.
surfbum42
#7
Oct21-05, 04:50 PM
P: 2
You also have to remember that as the aircraft rises it will be consuming fuel reducing the thrust that is required to maintain a constant upward acceleration. Also as you do this to maintain a steady acceleration you must reduce the thrust to maintain the same thrust to weight ratio.
Pengwuino
#8
Oct21-05, 05:06 PM
PF Gold
Pengwuino's Avatar
P: 7,120
I think they accelerate up as fast as possible (as opposed to steady acceleration) because you can only hover for a limited time. They can (although I may very well be wrong because I remember someone saying something contrary to this idea) hover for about 45 seconds because they have a limited supply of water to cool the engine which would normally be done by the passing air in flight.
chris190
#9
Nov4-05, 05:10 PM
P: 2
......It can hover for more than 45 sec. I went to two air shows that had Harriers and one of them was still at about 100-150 feet altitude in front of the crowd for at least 1 min then it slowly turned around and after about 2-3 min of downward thrust it started slowly to move forward until it achieved the required speed to use only the back thrust.
.....I could not find how much a Harrier consumes at 100 thrust off google.
Either way it would not be 1 gal/sec like some one mentioned to me would it?
russ_watters
#10
Nov4-05, 06:02 PM
Mentor
P: 22,295
Well, the Harrier carries about 1000 gallons of internal fuel alone. At a gallon a second, that's more than 15 minutes. It does seem a little high for the consumption rate, but it's conceivable.
Pengwuino
#11
Nov4-05, 06:55 PM
PF Gold
Pengwuino's Avatar
P: 7,120
Quote Quote by chris190
......It can hover for more than 45 sec. I went to two air shows that had Harriers and one of them was still at about 100-150 feet altitude in front of the crowd for at least 1 min then it slowly turned around and after about 2-3 min of downward thrust it started slowly to move forward until it achieved the required speed to use only the back thrust.
.....I could not find how much a Harrier consumes at 100 thrust off google.
Either way it would not be 1 gal/sec like some one mentioned to me would it?
Well beats me, i read it a long time ago after watching True Lies. Guess hollywood screwed me again.
adrnmrnda
#12
Apr20-08, 05:13 PM
P: 6
is there any one still interested in this question, the thread looks pretty old and i might add a little on it.
Averagesupernova
#13
Apr20-08, 07:23 PM
P: 2,528
Add away. The harrier has always interested me.
engware
#14
Apr20-08, 11:00 PM
P: 62
Hi there:

Here is a URL that might help you with required thrust and fuel consumption calculations:

http://engware.i-dentity.com/calc3.htm

Thanks,

Gordan
adrnmrnda
#15
Apr21-08, 11:27 AM
P: 6
aviation measures in weights rather then gallons and of course in the US it is in pounds, had to mention becuase there are aroung 6 countries that use the harrier. the hover limitation is not solely on a time bases but on liitations of fuel availability and temperature of the engine so as not to damage it, and there is the outside temperature that has a direct impact on engine performance, everything is based on engine performance. Water is not required but it is prefered as it does help cool the engine temperature, more on that next time true believers.
mgb_phys
#16
Apr21-08, 11:58 AM
Sci Advisor
HW Helper
P: 8,953
The water on a Harrier doesn't diectly cool the engine.
It is injected into the exhaust after the engine - the purpose is to cool and increase the density of the output jet (a kind of anti-afterburner) it also increases the engine power by condensing the exhaust and so sucking more air out of the engine.

A lightly loaded harrier (such as at an airshow) with no external stores can hover pretty much indefinately without using cooling water, certainly in the cold wet rainy conditions that are traditional at British airshows. Although they generally try and move slowly forward while hovering for a long time, injesting hot oxygen poor exhaust back into the engine intake is a problem if hovering in still conditions.

Water cooling is needed for take off with heavy combat payloads or in desert conditions - but becauuse of the fuel required for a VTOL take off, they prefer runways (or catapults) if possible.
adrnmrnda
#17
Apr21-08, 11:12 PM
P: 6
the water is injected in three stages, the first is in the cooling air supply for some early turbines, the second is is in the combustion chamber air flow and the third is directly into the combustion chamber. it does not directly improve thrust but reduces engine temperature allowing the engine to work at higher rpms and indirectly improves thrust, i dont believe that i have ever seen a harrier use a catapult but that does not mean that it has never happened.
mgb_phys
#18
Apr21-08, 11:30 PM
Sci Advisor
HW Helper
P: 8,953
Yes you're right, the Harrier doesn't use a catapult but does have a clever little ski jump on British carriers.
These were originally designed for helicopters only so a bit of ingenuity was required to operate aircraft from them. http://www.aerospaceweb.org/question...s/q0281b.shtml The US Marines don't use the ski jump - I think this is because US Navy practice is to store most aircraft on the deck and the ski jump reduces available deck area.


Register to reply

Related Discussions
Question on the AV8 Harrier. Mechanical Engineering 3
Stiochiometric air-to-fuel ratio for heavy fuel oil Engineering Systems & Design 2
Fuel consumption Introductory Physics Homework 2
Why Harrier didn't success? Aerospace Engineering 20
Relativity and fuel consumption General Physics 6