CHI08IA294
CHI08IA294

On September 18, 2008, about 1245 eastern daylight time, an Indus Aviation Inc. T-211 Thorpedo light sport airplane, N107JF, sustained minor damage during a forced landing near La Porte, Indiana, following an in-flight loss of engine power. The airplane was new and it was being delivered on a positioning flight operated under 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the incident. No flight plan was on file. The commercial pilot reported no injuries. The flight originated from the Kirsch Municipal Airport (IRS), near Sturgis, Michigan, and was destined for the Chisholm-Hibbing Airport, near Hibbing, Minnesota.

The pilot reported that he landed at IRS about 1130 for a fuel stop during the positioning flight. He departed IRS and 42 minutes into flight at 4,500 feet the engine stopped. The pilot said he established best glide, turned towards La Porte Municipal airport and attempted a restart. He notified approach control of the situation, secured the aircraft for and emergency landing, and landed in a soybean field approximately 3 miles from the La Porte Airport. The airplane was not damaged.

Upon inspection of aircraft, the fuel indicator showed 16 gallons of fuel with no fuel in tank. The T-211 has a single bladder with 21 gallons usable fuel.

According to the factory, a siphon started and emptied all the fuel out the single vent line. This slowly collapsed the bladder onto the fuel sending unit, thus the erroneous indication.

In his report, the pilot recommended that the aircraft not be flown until the vent system in re-designed and proven that a siphon is no longer possible.

Subsequent to the incident, the manufacturer issued service notification number IASN 2008-1. The service notification, in part, stated:

ISSUE: The fuel capacity of the T11 and T211 series aircraft is 22 gallons, 21 usable. The pilot operating handbook (POH) states, and placards at the fuel filler, Do Not Fill Above Neck Bottom. This procedure is required to allow for expansion of the fuel within the fuel cell. If the aircraft is filled above the bottom of the filler neck, enough expansion of the fuel could occur that fuel could exit through the air vent on the top side of the fuel cell, and exit out the vent on the bottom of the fuselage. This situation may cause a siphoning process to be initiated. Expansion may occur when the fuel entering the cell is cooler than the fuel cell and surrounding fuselage body, or when the aircraft is left in the sun after refueling. Because the fuel cell is flexible, as opposed to a metal or fiberglass tank, the fuel envelope could contract as the fuel siphons out the vent line. This can occur on the ground or in flight.

RECOMMENDED CORRECTIVE ACTION: Do not fill the fuel cell above the bottom of the filler neck.

WHO MAY PERFORM CORRECTIVE ACTION: Pilot, lineman, anyone who fuels the aircraft. The pilot, as a part of the aircraft preflight, must check the fuel level to ensure the fuel level is below the bottom of the filler neck.

Subsequent to service notification number IASN 2008-1, the manufacturer issued service bulletin number IASB 2009-1. The service bulletin, in part, stated:

ISSUE: In the Thorpedo/Sky Skooter POH, the placards section displays the filler neck placard that states the tank must not be filled above the bottom of the filler neck. If the fuel tank is overfilled above the bottom of the filler-neck, and the fuel vent line fills with fuel, it is possible that a siphoning condition may be induced. If this condition occurs, and continues without interruption, the fuel supply may be depleted.

RECOMMENDED CORRECTIVE ACTION: To provide an additional margin for error in the event the fuel tank is overfilled, the venting in the area of the fuel filler neck and fuel cap have been modified. These modifications prevent the loss of any significant amount of fuel if the vent line becomes filled with fuel. Parts and installation are approved by Indus Aviation, Inc. and are available. Contact Indus Aviation, Inc. if you are unsure if your vent system has been modified.

WHO MAY PERFORM CORRECTIVE ACTION: Aircraft Owner, Light Sport Repairman, A&P or factory authorized representative.

MISCELLANEOUS: It is imperative that the operating limitations described in the POH and the placard markings on the aircraft be followed.

The airplane was certified to American Society for Testing and Materials
(ASTM) consensus standards which allowed the T-211's fuel tank vent design. In contrast, 14 CFR Part 23 listed the following published standards for aircraft certified under it:

Sec. 23.975 - Fuel tank vents and carburetor vapor vents ...

(2) Each vent must be constructed to prevent siphoning of fuel during normal operation ...

(7) Vents must be arranged to prevent the loss of fuel, except fuel discharged because of thermal expansion, when the airplane is parked in any direction on a ramp having a one-percent slope.

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