From the Left Seat

A hearty welcome back to all who flew the coup for the summer (you know who you are) and for those of you who persevered the heat of Florida!!!!  Cooler weather coming.

NEXT MEETING SAT. 11/07/2009 9:00am.

A history of gas  (AvGas )

Very early aircraft used the fuel that was available at the time, mostly 60 octane car gas.  In the 1930's aircraft engines got up to around 9 to 1 compression, and the auto gas burned too quickly, and caused detonation, so they added tetra-ethyl lead to the gas to control the combustion process.

At the end of WW11, there were 4 types of aviation fuel.  80/87 octane (dyed red), 91/96( blue) 100/130 (dyed green) and 115/145 (dyed purple).  The lower number in each case was the octane rating with a "lean" mixture, while the higher was for the "rich" mixture.  The 91/96 was the first to disappear, and when the air force and the airlines switched to jets, the 115/145 went away as well.  Low sales forced the 80/87 octane to go away.

By then the environmentalist movement  led to the development of  a  new 100 octane fuel called 100LL (Low Lead)  Note that even though 100LL (dyed red) is designated as " low lead" fuel, and contains only half of the lead of the old 100/130 (green), it still contains four times the lead content of the old 80/87 (red)  AvGas.  However, switching to the 100LL caused some problems in lower compression engines such as plug fouling that was not present with the 80/87 octane fuel.  This led to EAA and others to start testing the uses of auto gas, or "MoGas" in the lower compression engines, and as a result several STC's  (Supplemental Type Certificates) being issued.  Since that time engine manufactures have now eliminated much of the lead fouling problems with the 100LL in lower compression engines.

Now recent changes to the MoGas formula, including the widespread use of Ethanol as an additive, has now created problems for those using the Auto Fuel STC.

More as this develops.

Don't forget that there are elections this month!!!