Pictures of the fuel vlave.

At the end of this page is more information on the fuel valve and problems with it in 1999 which are similar to the one causing the September 4, 2009 SF260 crash in Atlanta.

the fuel cap

More on fuel caps.

Perhaps one of the most over looked items in the SF260 is the fuel cap. The rubber gets hard and since new ones cost $100 from Mike Patlin, nothing is done about them. The rubber needs to be soft and new caps can be bought from Aircraft Spruce and plywood for $14.00 each. This rubber will get hard too but they may last anywhere from one year to 5 years. What I have done to make closing the toggles easier is to insert a plastic washer under the toggle. This way you do not have metal against metal, which causes gnarling.

Be certain that the wing tip tanks have vented caps and the main tanks have non-vented caps. Mixing these up can cause serious problems including collapsing the wing tip tank.

A lose fit on the main wing tanks will result in fuel leaking out during flight. This results in a spray coming out of the overflow tubes. Also, water will get into the fuel system. If you have tightened the caps all the way and the caps are still lose, then add washers under the toggle until you can get new rubber for the caps.

My original solution was to cut off the stems that screw into the toggles. This is definitely the wrong thing to do.



Estimating the quantity of fuel in the wing tip tank.

Put a yardstick into the wing tip tank and remove it quickly and look at the level of the fuel. Here is an estimate of how much fuel is in the tip tank. Since the fuel will creep up the wood by capillary action this is only a rough approximation of the fuel level.

Wing Tip Tank measurements
14" = 18.5 gallons Full
12" = 17 gallons
11" = 15.5 gallons
10" = 13.5 gallons
09" = 11 gallons
08" = 9.5 gallons
07" = 8 gallons
06" = 6 gallons
05" = 4.5 gallons
04" = 3.4 gallons
03" = 2 gallons
02" = 1 gallon
01" = 1/3 gallon


PROBLEMS The main gas tanks can leak and the fuel drains out into the wing. It then can run along the trailing edge inside the wing and go right into the fuselage. This creates a real fire hazard.
SOLUTION: Check under the wing around the plate that covers the main tanks. Look for any fuel staining. There have been reports of fuel leaking out through the fuel sender gasket and also along a line where the retaining straps hold the tank in. When this is repaired be certain to use chafing tape to prevent a repeat.

The fuel system in the SF.260 is very simple.
There are four tanks that feed into the central fuel selector and then goes through the fire wall and into an electric fuel pump, a mechanical fuel pump, the fuel flow transducer and then into the fuel injectors.

The engine driven fuel pump will not clear air out of the line. Since the wing tanks sit so much lower than the fuel selector, the slightest air leak will result in air getting into the fuel line. In starting the engine the electrical auxiliary fuel pump must be used since it is the only way of clearing air from the fuel lines. Because the wing tip tanks are so much higher, these tanks are far less likely to have problems with air getting into the fuel lines. However, the POH demands that all take off's and landings be done on the main wing tanks and not the wing tip tanks. Because of the air cavitation problems the electric fuel pump must also be used during take off and landing.

Some hapless souls neglect to turn on the fuel pump during takeoffs because they then must remember to turn it off later. They live with the delusion that if the engine stops they will simply switch on the auxiliary pump. (I am one of those people.) When the engine stops on takeoff the adrenaline will flow into your systemic circulation so quickly that you may delay three or four seconds before turning on the fuel pump. By then it may be too late to save the plane.

The tank selector fuel valve has four positions on the Pre SF260C models and five positions on the C and later models. The both selection connects the wing tip tanks and they will gravity feed into the fuel pump. If one of the tanks does not drain, because of a restriction in the vent cap or an air lock in the fuel line, that wing will become heavy. If you are on autopilot you will not know this until the engine quits. Therefore I have gotten into the habit of momentarily turning off the autopilot every hour. I do this to be certain that fuel is draining equally from both wing tip tanks. Air can get trapped in the wing tip fuel lines if you fly inverted. This results in fuel being drained from only one wing tip tank. By selecting either left or right tip tank the air can be purged from the line.

The next problem is fuel draining out of a high wing tip tank into a low wing tip tank while the plane is on the ramp. This only happens if one of the one-way fuel valves malfunctions.

These one-way valves, as pictured here, are located on each side of the forward center console. They are in plain sight and quite easy to remove. I have tried to buy replacements and have been unable to find them. Aircraft Spruce and Specialty has a one-way valve that is 5mm longer than the one in our plane. Instead of working with a spring-loaded flapper valve it works with a floating ball valve. I have made up a shorter fuel line to use with this valve but have not used it since I finally got the Marchetti supplied valve to work. This valve is very simple to remove and open up to service.

To insure that there will be no cross-tank fuel transfer you can run the wing tip tanks empty and then do not use them after refilling. This will insure an air lock, which will prevent cross drainage. This should also tell you that after running a tank, any tank, dry you must clear the air out of the fuel line when you next select it. This must be done with the auxiliary fuel pump on and requires enduring an anxious moment or two while the air is cleared through the injection system.

The fuel gauges that come with the Marchetti are EDO AIR. The Mitchell instruments look exactly the same but will not work. I am presently calling Sigma Tech to see if we can buy the replacement instruments. However, the Edo Air instruments use a condenser in the circuit and these are notorious for going bad and causing spurious readings. Changing out these instruments with the Mitchell instruments is not a workable solution.

The Electric Fuel Pump.

Two types are shown in our parts manual. The first type is the Bendix interrupter type pumps that are connected in parallel. This doubles the volume output but not the pressure. Bendix was bought out by Purolator and the pump is now called a Fascett interrupter pump. The company is still in Elmira, NY. Part number 476439 is no longer made. Instead there is part # 476088. This is a 24-volt pump what puts out 4 to 6 pounds of fuel pressure. This pump barely works. It is sold by Aircraft Spruce and Specialty for $69.00 each. Then there is part # 480563. This is a 24-volt pump that puts out 7 1/2 pounds of pressure. You can get these from J&N auto electric in Cincinnati Ohio. They cost $90 each.

A good pump is the Dukes. Cost $500. This has plastic paddles, which do much better than the carbon paddles in the Parker pump. The only problem is that this pump is very sensitive to particulate matter. Since the gascolator comes after the fuel pump there is no fuel filter to keep out particles that get into the wing tip tanks. A small particle can get into the Dukes pump and keep the valve open, which will keep it from developing pressure.

The other type pump shown is in figure 7/17A. This is a parker Pump and is used in the Aztec and costs $1,800. Yes that is right it costs a lot. These pumps produce 38 lbs of pressure and put out 386 PPH, which is around 60 gallons an hour. These pumps use 4 graphite paddles, which start to stick after a year. In my opinion, the interrupter pump is better suited for the SF260 because the auxiliary fuel pump is used so little.

For drawings of the fuel pumps click here.

Fuel Valve

The 4 or five position fuel valve is very simple. However, it can bind up over a one-week period. For this reason, once it gets at all difficult to turn take it out and polish the stem and the hole the stem goes through. Failure to do this will result in a frozen valve that will not turn at all. There are 5 wafers in the 5-position valve. Be careful so each goes back into its original position. The valve is very simple so do not be afraid of it. Also, while it is out be certain that all of the fittings are not leaking fuel. Look for any staining. This valve is an engineering masterpiece and worth looking at. It is in a position that is hard to get to, but it is simple to remove and rebuild.
The valve can freeze up when the stem starts to knarl with the plate it passes through. Once this process starts it accelerates quickly. There is also a 22 cent "O" ring around this stem that keeps air out of the valve. Once this "O" ring gets hard or brittle it can start letting air seep into the valve and this results in the engine running rough. I also had a fuel line that was so badly made that the fittings almost fell off the ends. If an end had come off during flight I would have crashed. However, once the fuel line was replaced, the engine ran well again. Bob Gandt tells me that his engine was running so rough that he had to fix it. First he got a five gallon fuel tank and connected it directly to the mechanical pump. The engine ran well. Then he connected to the main fuel line and it ran rough again. Next he moved the 5-gallon fuel line to the gascolator and again the engine ran smooth. He connected the 5-gallon line to the fuel valve and ran off of the 5-gallon tank and the engine almost quit. Finally, after replacing $2,000 worth of fuel pumps and fuel lines he took the 4 position fuel selector valve apart and replaced the 22 cent "O" ring that goes around the valve stem shaft and this corrected his problem. Corrections by Bob Gandt
Dudley,
Your reprise of my air leak adventure is almost exact. The five gallon can experimentation ended after plumbing it to the gascalator and proving that the problem was aft of the firewall. I then plumbed the right tip tank directly to the fuel system - bypassing the faulty tank selector, and still had a smooth-running engine. You might also mention that this malady most dramatically affects the fuel-injected engines and probably would go unnoticed on the carbureted models. It was good seeing you here today. Keep up the good work and stay in touch.
Best wishes, Bob

NTSB Identification: ERA09LA516
14 CFR Part 91: General Aviation
Accident occurred Friday, September 04, 2009 in Atlanta, GA
Aircraft: SIAI-MARCHETTI F.260, registration: N517P
Injuries: 2 Minor.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

On September 4, 2009, about 1330 eastern daylight time, a Siai-Marchetti SF-260, N517P, was substantially damaged after a loss of engine power and forced landing after takeoff at Cobb County Airport (RYY), Atlanta, Georgia. The certificated private pilot and passenger sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local personal flight that was originating at the time of the accident. The flight was conducted under the provisions of 14 Code of Federal Regulations Part 91.

According to the pilot, the preflight, engine run-up, taxi, and takeoff from runway 9 were all “normal.” At 500 feet above ground level (agl), the engine lost power, and the pilot maneuvered the airplane for a downwind landing on runway 27. The pilot confirmed the positions on the throttle, propeller, fuel pump, and fuel selector controls and the engine regained power temporarily. About 300 feet agl, the engine again lost power, and the pilot elected to land in a field off-airport, gear up, due to the extension time required for the airplane’s landing gear system. The pilot described a “benign” off-airport landing in tall weeds and brush, and he and his passenger were greeted by airport emergency personnel almost immediately after egressing the airplane.

The pilot held a private pilot certificate with a rating for airplane single engine land. His most recent FAA third class medical certificate was issued April 18, 2008. The pilot reported 1,300 total hours of flight experience, of which 369 hours were in the accident airplane make and model.

According to the owner, the airplane was manufactured in 1968 and had accrued 1,592 total aircraft hours. Its most recent annual inspection was completed on January 30, 2009, at 1,584 total aircraft hours.

At 1346, the weather reported at RYY included few clouds at 3,000 feet and winds from 110 degrees at 12 knots, gusting to 16 knots. The visibility was 10 miles. The temperature was 24 degrees Celsius (C) and the dew point was 15 degrees C.

Examination of the airplane by an FAA inspector revealed the airplane sustained substantial damage to the nose section, firewall, cabin structure, and empennage.

The integrity of the fuel system was verified, and no evidence of fuel contamination was noted during sampling. The airframe fuel filters were inspected as well as the airframe fuel pump filters with no clogs or contamination noted. The carburetor was broken off at its mount; however the lines and controls were still intact. Operation of the airframe boost pumps revealed that the pumps would not draw fuel. Closer examination of the fuel selector valve and fuel shut off valve revealed staining consistent with fuel leakage.

When positive pressure was applied to the fuel tanks, fuel leaked around the shaft of the fuel shut -off cock located under the cockpit instrument panel area. Pressure was removed from the tanks, the fuel shut-off cock was sealed with a rag, and the boost pumps were then able to draw fuel when power was applied. Removal of the rag created an air leak, and the boost pumps would not draw fuel.



N404FD crashed on Nov. 2, 1995 at the Grand Canyon airport. It had been flown from England to the USA and had an auxillary fuel tank. The ON OFF valve for this tank was found to be in a position that was neither off or on and had allowed air into the line which caused the engine failure. Can you imagine what would have happened if the valve had been miss positioned while over the Atlantic Ocean.

Here is the link to the accident report. http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX96LA036&rpt=fa

P.S. Dudley, we used to fly FB111's and do a fuel dump and then light the after burner. Here is what it looked like.