Field Test for Determining Presence and Amount of Alcohol
Field Information Number 306
EXPERIMENTAL AIRCRAFT ASSOCIATION, INC. (EAA) appreciates the permission of Conoco, Inc. to base this field test procedure on one developed by the company.
This method determines the amount, if any, of alcohol present in gasoline. This test is designed specifically for field-testing where time and simplicity are important factors.
Summary of Method
A sample of gasoline is shaken at room temperature with an amount of added water. The volume increase of water is proportional to the amount of alcohol initially in the fuel sample. Nine (9) parts of the gasoline sample are combined with one (1) part water.
Appartus Required for Either of the Methods Below
Graduated Cylinder Method - One (1) each one thousand milliliter (1000 ml) clear Pyrex or shatter-resistant glass graduated cylinder OR transparent chemical-resistant plastic (such as TPX) graduated cylinder. (These can be purchased from laboratory or chemical equipment suppliers.)
Measuring Cup Method - One (1) each 2-quart clear pyrex, glass, or chemical resistant plastic container. One (1) each 4-fluid-ounce measuring up (1/2 cup). One (1) each 32-fluid-ounce measuring cup (1 quart).
On the 2-quart container, mark the level of exactly four (4) fluid ounces (1/2 cup) permanently on the side (a piece of masking tape can be used).
Graduated Cylinder Method - To 9 parts of gasoline (900 ml), add 100 ml of water for a total of 1000 ml in the graduated cylinder. Shake thoroughly, let stand for 10 minutes or until gasoline is again bright and clear. Record the apparent level of the line between the gasoline and water. This “Final Volume” is used in the calculation below.
Measuring Cup Method - To nine (9) parts of the gasoline sample (36 ounces or 1 quart plus ½ cup), add 4 fluid ounces (1/2 cup) of water for a total of 40 fluid ounces in the 2-quart container. Shake thoroughly, let stand for 10 minutes or until gasoline is again bright and clear. Record the apparent level of the line between the gasoline and water.
The Measuring Cup Method is intended to indicate the presence of alcohol and is not practical to evaluate the amount of alcohol. If the final line between gasoline and water is measurably higher than the ½ cup mark, the presence of alcohol is indicated.
NOTE: Erroneous results are probable if sample and water are not thoroughly shaken and mixed.
Graduated Cylinder Method - Note the final volume and calculate the percentage of alcohol in the sample using the following calculation: Percentage of Alcohol in Gasoline = (Volume – 100 divided by 900) X 100.
Where: V = “Final Volume” of water as determined in procedure above (read at separation line between water and gasoline).
Within +/- 1% alcohol if you measured and recorded accurately.
Action to be Taken
In the opinion of EAA, and in the interest of most conservative operations, the following observations are offered:
If alcohol content is less than 1%, fuel will probably have no effect on aircraft.
If fuel contains up to 5% alcohol, caution must be exercised. Do not permit it to remain in tanks or fuel system for more than 24 hours, then drain and refill with alcohol-free fuel, ensuring that no alcohol concentration remains in fuel lines or sump. Vapor lock may be a problem. DO NOT FLY.
If alcohol content is more than 5%, DO NOT FLY. Drain the fuel system, flush all parts, replace with clean alcohol-free fuel and run up engine long enough to exchange fuel in carburetor bowl.
Alcohol attacks some seal materials and varnishes on cork floats of fuel level indicators. This could cause leakage of seals and release particles of varnish from floats, causing blocked screens in fuel lines or blocked carburetor jets. Excessive entrained water carried by alcohol could lead to fuel line blockage or blockage at screens or values when operating at low ambient temperatures at ground level or at high altitude. Fuel volatility is also increased with the addition of alcohol in a manner that is not detected by the Reid Vapor Pressure test, which is used to determine if a fuel meets the automotive specification. For example, a gasoline with alcohol will meet the Reid Vapor Pressure limit of 13.5 psi but it will behave as though it has a volatility of roughly 20 psi. Gasolines with alcohol will also phase separate. Phase separation occurs as the gasoline/alcohol blend cools, such as when a plane climbs to a higher altitude. When water that is absorbed in the fuel by alcohol comes out of solution, it takes most of the alcohol with it. The quantity that comes out of solution cannot be handled by the sediment bowl and tank sumps. Furthermore, if the alcohol is used to raise the octane of the base gasoline, the gasoline that remains will not have sufficient octane to prevent detonation. A good reference for this phase separation problem is: Paul Corp., Laboratory Investigations into the Effects of Adding Alcohol to Turbine Fuel, DOT/FAA/CT-TN88/25 July 1988, FAA Technical Center, Atlantic City International Airport, NJ 08405.
Gasoline is volatile, extremely flammable and harmful, or fatal if swallowed. Avoid prolonged or repeated breathing of vapor or contact with skin or eyes. If swallowed, do not induce vomiting, get medical care immediately.