GLASS GOOSE GAZETTE * ISSUE #18, April, 2001

Page 15

the O-ring and groove mating. You can now screw the nut down against the O-ring to secure the seal. The O-ring will be trapped between the land in the nut and the land in the fuel pump and when the nut is tightened down, the O-ring will be squeezed between the two, providing the required seal.
From the fitting on the fuel pump, down to the fuel system for the engine, I recommend Aeroquip 601-6 hose and Aeroquip 816 hose fittings. The 601 hose is the type that is covered with stainless steel braid. This hose and fittings are quite expensive. However, there is an alternative at your local hot rod shop. I have never been able to tell any difference between the Aeroquip hose and fittings they sell at those hot rod shops and the aircraft version except for the color (aircraft is blue, and auto is red) and the price, (aircraft is expensive, and auto is much less expensive). So you can make that choice for yourself. The part #’s at the auto shop will be similar but different, but if you know what you want, they usually have them hanging on pegboards in bubble packs and they sell the hose by the foot.

One very serious warning. Assembling these hoses is not as simple as it appears. Improperly assembled hoses have caused a lot of unsuspecting builders and mechanics to go bald prematurely! You must use a mandrel when assembling the ends to the hose. If you don’t, the fitting can slice the interior of the hose as it goes in. This can create a "flap" of rubber inside the hose that cannot be detected by normal inspection. This "flap" can become a one way check valve when the hose is put in operation and

stop up the tube! Because the flap naturally wants to lay down flat, it won’t bend up and stop up the tube until there is adequate flow through the hose. Because the flap lays back down when there is no flow, the reason the engine is starving for fuel can be very hard to find. Refer to The book, "Firewall Forward" by Tony Bengelis for the correct method to install these. The ACS catalog also has instructions. They also refer to the mandrel as "the assembly tool". When cutting the stainless steel braided hose, wrap the area you are going to cut with numerous wraps of masking tape to prevent the "threads" of the braid from raveling. The neater the braid remains, the easier it will be to do the installation of the fittings. Cut the braid and hose with a very fine-toothed hacksaw blade. A course blade will catch the threads of the braid and pull them instead of cutting them.

The elbow on the mechanical fuel pump on an 0-320 (and I assume on an 0-360), will interfere with the plywood and glass motor mount ear right next to it. The ear must be trimmed to provide adequate clearance to prevent the elbow from contacting the ear. The builder must consider that the engine will rotate slightly to the right (looking at the engine from the propeller end) against the engine torque when the engine is under power. This will move the right side of the engine closer to the airframe components on that side. If the elbow is too close to the ear with the engine at rest, when the engine is under power the elbow will contact the ear.

One result of this contact is that the vibration of the engine will be transmitted to the airframe and manifest itself as extremely high noise levels in the cockpit!

FIREWALL AND NOISE SUPPRESSION

In an aircraft with the engine mounted in the front (tractor), the firewall serves to protect the passenger compartment from the heat in the engine compartment and frequently also serves to act as a sound barrier. This would include the normal heat from the engine, or protection should a fire develop in the engine compartment. The fact is that fires are almost unheard of in engine compartments during flight because of the high rate of airflow through that area.

The airflow literally "blows out" any flames before they can develop.; Most in flight flames in aircraft are dramatic depictions created by Hollywood producers. We all automatically think that aircraft can burn up in flight from engine fires because of all those WW 2 movies we’ve seen, but the reality is somewhat different. There have been exceptions of course, but those usually involved an in flight explosion or collision in which

GLASS GOOSE GAZETTE * ISSUE #18, April, 2001

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