Fuel Flow and temperature
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Fuel Flow and temperature
Hi guys, I am little confused about the relationship between FF and Temperature. On jet engines do you consume more or less fuel on a cold day?
Thanks
Thanks
Actually, for the same amount of thrust, there is very little difference in fuel required vs. ambient temperature. The compressor should be slightly more efficient on a cold day and hence require less fuel, but were talking a very small number here - basically in the mud.
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Thanks oggers and tdracer for your answer, I really appreciate.
A friend of mine flying the Q400 showed me on his the FCOM the FF at different temperatures for the same weight and FL, and obviously you will consume more on a cold atmosphere, but is it the same with jet engines?
A friend of mine flying the Q400 showed me on his the FCOM the FF at different temperatures for the same weight and FL, and obviously you will consume more on a cold atmosphere, but is it the same with jet engines?
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I would think that at the same weight and FL you will consume more on a cold day, because the air you are flying through is denser (more drag). But on a cold day you should be able to climb higher to achieve optimum altitude, and at that higher level consume much the same fuel as you would have consumed on a warmer day at a lower level.
In other words, if you just think about density, the engine doesn't really care about temperature (within practical limits).
I have no figures for this, just my gut feeling.
In other words, if you just think about density, the engine doesn't really care about temperature (within practical limits).
I have no figures for this, just my gut feeling.
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Fuel consumption
The simple answer to the original question is:
Cold air is more dense, so for a given engine RPM, more fuel is required to maintain that RPM on a cold day (and thrust at that RPM will be greater on a cold day than on a hotter day).
In summary, if an engine produces X RPM on an ISA Standard day at a given fuel flow at sea level, that engine will require more fuel and will produce more thrust at X RPM on an ISA -10 day than the fuel it would require to maintain X RPM on an ISA +10 day (with a lower thrust produced).
BTW Mintraman, the Q400 is powered by a jet engine, albeit one which drives a propeller.
Cold air is more dense, so for a given engine RPM, more fuel is required to maintain that RPM on a cold day (and thrust at that RPM will be greater on a cold day than on a hotter day).
In summary, if an engine produces X RPM on an ISA Standard day at a given fuel flow at sea level, that engine will require more fuel and will produce more thrust at X RPM on an ISA -10 day than the fuel it would require to maintain X RPM on an ISA +10 day (with a lower thrust produced).
BTW Mintraman, the Q400 is powered by a jet engine, albeit one which drives a propeller.
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