Register Forms FAQ Wikiposts Calendar Search Today's Posts Mark Forums Read

 Tech Log The very best in practical technical discussion on the web

 4th Sep 2011, 11:07 #1 (permalink) Thread Starter   Join Date: Jul 2003 Location: germany Age: 45 Posts: 264 flashpoint of JetA1 Hi, max. fuel temperature in the AFM or our aircrafts (Citation CJ1+/CJ2+) is described as +57 degrees Celsius. Given the fact that the flashing point of Jet A1 is at +38 degrees, I was wondering why max. fuel temperature is not also set at +38. Inputs welcome, Cheers Cecco
 4th Sep 2011, 11:34 #2 (permalink) Join Date: Oct 2009 Location: UK Posts: 1,272 Hi Cecco, The flash point of petroleum is about -40degs C. Have you never driven a petrol fuelled car in summer?
 4th Sep 2011, 13:13 #3 (permalink) Join Date: Dec 1998 Location: . Posts: 2,844 yes that's for petrol but jet fuel is around +60C
 4th Sep 2011, 13:24 #4 (permalink) Join Date: Feb 2009 Location: Worldwide Posts: 580 Cecco, The flash point is the lowest temperature where the liquid gives off vapours that can be ignited by an ignition source. So even if the fuel temperature is above the flash point, it will not ignite by itself. That won't occur until above 200 degrees Celsius.
 4th Sep 2011, 13:47 #5 (permalink) Join Date: Nov 2007 Location: Texas Posts: 1,580 Many times the upper fuel temperature limit is a function of the fuel serving as a heat sink in the oil cooler.
 4th Sep 2011, 14:51 #6 (permalink) Thread Starter   Join Date: Jul 2003 Location: germany Age: 45 Posts: 264 @MarkerInbound Can you specify that? You mean that above the max. fuel temp. the heat exchange fuel/oil doesn´t work properly?
 4th Sep 2011, 15:13 #7 (permalink) Join Date: Jul 2007 Location: France Posts: 611 Flash Point of JetA1 Cecco: The flash point of Jet A1 is approximately 40 degrees centigrade, The equivalent in Russia was called JT-1 which had a flash point of 28 degrees centigrade, so the risk was a little bit greater. Tmb
 4th Sep 2011, 23:05 #8 (permalink) Join Date: Jan 2007 Location: Vermont Age: 61 Posts: 173 The flash point is the lowest temperature at which the fuel vapor can burn in the presence of a continuous ignition source. If the ignition source is removed, the fuel stops burning. The fire point is the lowest temperature at which the fuel vapor will continue to burn after the ignition source is removed...much higher than the flash point. Both of these are specification standards; they are used to characterize a fuel's chemistry and behavior, not necessarily as specific safety thresholds. However, a higher flash point is used to distinguish a greater safety factor in storage and fuel delivery. The US Navy uses JP-5 for shipborne aviation because it has a flash point of around 62C. Neither of these temperatures is related to the auto-ignition temperature, at which the fuel will spontaneously ignite and burn. This is generally much higher than the fire point.
5th Sep 2011, 02:09   #9 (permalink)

Join Date: Nov 2007
Location: Texas
Posts: 1,580
Quote:
 Can you specify that? You mean that above the max. fuel temp. the heat exchange fuel/oil doesn´t work properly?
Yes, think about it. If you had 65 degree fuel (granted, hard to get to but for an example) there is not going to be much cooling of the oil. Sixty five would be the lowest temperature but there is not a 100 % transfer from the oil to the fuel so the oil temperature will remain higher.