GMAS et al

[Bob Cook]

GMAS

Why does the fuel "boil" at high altitudes ?

Bob

[GMAs]

as you go higher the vapor pressure decreases....

Here lets do a experiment.... remember in physics when you put a vacuum on a beaker of water in a vacuum chamber... it started to boil when the pressure decreased.... same with the fuel... it starts to boil when the pressure from way up their starts to be lower ... it starts to boil...

but,.....

you have another factor that comes into play with fuels... because they are airomatic they have lighter mixtures of stuff.... and so the temp, pressure and mixing all play a factor... if for instance the temp is lower... like density altitude the pressure is greater and also the fact that the temp is lower causes the voc (viscosity) of the fuel to increase... thus the vapor pressure is going to be much higher... in this case higher means lower pressure....


Now where can we get heat from... well the hoses can transmitt the radient heat... but, more the mechanical action of the pump while in operation can add to the heat of the fuel... and thus the vapor pressure would be lowere from say 14 to 10.... hope this helps.. G.M.

[kevin]

When does this occur? How does it effect our aircraft and pilot technique?

Perhaps y'all discussing this at the Bahamas meeting, but for those of us who weren't there...

Kevin

[WebMaster]

Well, see what you missed!!!
There was lots of stuff discussed, you'll just have to try and make it next year!!

[GMAs]

Sorry.. Kevin

Its a little too much to try and put to word here on the web... and yes we did discuss it at the meeting....

Now... some people have written and suggested that we have another for out west...of the big gofer hills.. but,... its a lot of work... and time... en all... however is enough people want to .... we can... although the last one... was real weak in attendence... even though it was planned....


BY THE WAY... I ALMOST HAVE THE OIL CHANGE POWRE POINT PRESENTATION DONE... AND THAT WE CAN POST ON THE WEB.... I STILL HAVE TO EDIT IT... BUT, IT DOES HAVE PICTURES EN ALL TO TAKE ONE STEP BY STEP ON THE CHANGING OF OIL AND FILTERS ON THE SKYMASTER.... SOMETHING TO LOOK FOR AND DOWN LOAD FROM THE CLUB...

Of course it will be open to editing... and comments from the users... in case I missed anything... smile...

remember that even though changing oil is a pilot thing.. and it will save you money by doing it yourself... it by no means is going to cut your mechanic out... and its intention and presentation is not such that one can bypass their mechanic... it is a general ... how to... that should be reviewed by the owner/pilot/operator... and then discussed with their mechanic... and have him show you the proper way to do things like torqing the bolts and safety wiring the devices... you will only be helping him out by doing some of the little things that he won't have to .... which is called getting dirty... and that saves you money.... again.... your mechainc is the first line of maintance for your plane... and after he supervises your work... and signs you off... would one want to take it on by themselves.... G.M>

[Kevin McDole]

Originally posted by Bob Cook
GMAS

Why does the fuel "boil" at high altitudes ?

Bob,

There's a good explanation of this on the Chevron Web site. See the paragraph titled "Fuel Boil-Off":

http://www.chevron.com/prodserv/fuels/bulletin/aviationfuel/8_ag_perf.shtm