Educational by Chapter of the Powered Paragliding Bible

I: First Flight

01 Training Process

02 Gearing Up

03 Handling the Wing

04 Prep For 1st Flight

05 The Flight

06 Flying With Wheels 

II: Spreading Wings

07 Weather Basics

08 The Law

09 Airspace   

10 Flying Anywhere

11 Controlled Airports

12 Setup & Mx

13 Flying Cross Country

14 Flying With Others

III: Mastery

15 Adv Ground Handling

16 Precision Flying

17 Challenging Sites

18 Advanced Maneuvers

19 Risk Management

20 Competition

21 Free Flight Transition

IV: Theory

22 Aerodynamics

23 Motor & Propeller

24 Weather & Wind

25 Roots: Our History

V: Choosing Gear

26 The Wing

27 The Motor Unit

28 Accessories

29 Home Building

VI: Getting the Most

30 Other Uses

31 Traveling With Gear

32 Photography

--- Not in book ---

33 Organizing Fly-Ins

34 Places To Fly

35 Preserving the Sport

36 Tandem

Determining Alcohol Content In Gasoline

Here is a way to roughly estimate the percentage of ethonol in pump gas, courtesy Conoco, Inc and EAA.

See also All About Fuel.

Most paramotor pilots use pump gas as opposed to avgas. In all likelihood, that means you're getting alcohol, specifically ethanol, in your fuel. How much of a problem that is depends on your equipment and how much alcohol is in the fuel. Apparently, the float bowl carbs and inverted engines are particularly averse to alcohol. How much alcohol is in the gas? Here is a way to find out.

You'll add 8 oz (or 8 of whatever units you prefer) of gasoline and 2 oz of water together in a graduated container. The 2 oz of water will sit at the bottom with the gas on top. Since water attracts alcohol, after shaking the container vigorously for a half-minute or so, the water will absorb nearly all the alcohol. Then you set the container down for 10 minutes so the water can come out of solution, complete with its suspended alcohol, and sit on the bottom again. If the fuel had alcohol init, there will appear to be more water than before. How much depends on how much more water there appears to be.

You can calculate the percent alcohol content of the fuel using the following method. F stands for the 2 oz of fuel, W is the 8 oz of water that you started with, and T is the total of both, or 10 in this case. WA is the amount of water that appears to remain after shaking and waiting. That water will now be holding most of the alcohol that was previously in the fuel. More apparent water, less apparent fuel. DIFF is the difference in water from before to after.

The percentage of alcohol in the sample fuel (%FA) is determined using the formula: %FA = DIFF/F x 100. So if you ended up with 3 oz of water and 7 oz of fuel then: %FA = 1/7 * 100 or 14% alcohol in the sample fuel.

It's not perfect since not all of the alcohol will come out of solution but it's pretty close.

According to the EAA's documents, up to 5% alcohol is enough to cause problems. They recommend fuel not even remain in tanks or fuel system for more than 24 hours (this is for aircraft, mind you). Vapor lock may be a problem.

Over 5% can cause serious problems. They say not to fly airplanes with this amount. In fact, they recommend draining the fuel system, flushing all parts, then running with clean alcohol-free fuel long enough to exchange fuel in carburetor bowl.

Here is the rest of the article regarding known problems with alcohol.

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.

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© 2016 Jeff Goin & Tim Kaiser   Remember: If there's air there, it should be flown in!