SAAA Safety Alerts

Safety Alerts

2011-11-21

ALCOHOL CONTAINING FUELS IN AIRCRAFT

From July next year all regular ULP petrol will be ethanol blended. The law will require any ethanol blended fuel be labelled as such at the pumps. There is no mention of using ethanol in premium grade fuels.Ethanol fuels should never be used in an aircraft or its engines.The downside applies especially to seaplanes.The following information comes from a special airworthiness information bulletin on Gasohol issued by the Federal Aviation Administration http://www.faa.gov/aircraft/safety/alerts/saib/media/CE-07-06.pdf and from my direct experiences as an industrial chemist:- * Alcohol present in automobile petrol is subject to phase separation, where the alcohol separates to bottom of the fuel tank, on two counts. It is brought about by traces of water contamination. The separation is not gradual, but happens all at once when a critical limit is reached. a) Only anhydrous alcohol is compatible with petrol. Alcohol is hygroscopic - it absorbs water from the atmosphere. Small amounts of water such as encountered with overnight condensation in the aircraft fuel tank can cause the alcohol component (including the water) to separate to the bottom of the tank which doesn’t help the engine to run. A water check of the fuel tank will be clear vodka, and not cloudy, so the check may not pick that a non combustible liquid is about to go into your engine. Using ethanol fuel in a humid environment can absorb water, or condensation can occur, either of which can cause separation. Garage fuel tanks which are underground are also susceptible to condensation and on rare occasions leaks. The water checks used here do not work any more if alcohol is present, and while some water can be tolerated in the fuel, it may be near the limit, increasing the risk of separation. b) Cooling can trip the separation over the edge in this case. This can occur when an aircraft is climbing to the cooler higher altitudes, or overnight on cold nights. A check before flight can’t work if the fuel is near the critical limit.* Vapour Locks. The addition of alcohol to automobile gasoline adversely affects the volatility of the fuel, which increases the risk of vapor lock.* Corrosive to Synthetic Materials. Alcohol present in automobile gasoline is corrosive and not compatible with the rubber seals and other materials used in many aircraft, which could lead to fuel system deterioration and malfunction. It has destroyed the lining inside integral fuel tanks, and in a known case has proceeded to destroy the composite structure of the wings as well, and of course the wing itself. Attack on tank linings has also caused gumming up and failure of carburettors.* Range and power are reduced. Alcohol present in automobile gasoline reduces the energy content of the fuel. Methanol has approximately 55 percent of the energy content of gasoline, and ethanol has approximately 73 percent of the energy content of automobile gasoline. The greater the amount of alcohol in the automobile gasoline, the greater the reduction in the aircraft’s range. And as an aside, the cheaper price of the petrol will be more than offset by the fact that you will have to buy more fuel to get there.

2009-08-24

URGENT AIRWORTHINESS DIRECTIVE – TCM 520/550

The FAA has issued an AD affecting cylinder assemblies manufactured by Superior Air Parts (SAP) fitted to TCM 520 and 550 series engines. There are roughly 980 aircraft on the Australian register fitted with TCM 520 and 550 series engines. Of those engines is not possible to determine how many are fitted with SAP cylinders, so it would be impossible to get in touch with every one likely to be affected. But the effect could be severe!
The AD requires:
- A check to confirm whether certain cylinder assemblies are fitted. If the cylinder assemblies have more than 750 flight hours, then an initial leak check is required within 25 flight hours and repeat inspections every 50 flight hours.
- Prohibition of installation of such cylinders and the removal of said cylinders when they reach the engine TBO.
The FAA AD becomes effective 9 September 2009 and CASA has agreed to make the Australian AD effective on 24 Sep, so there is some lead time.
Check out the forum for the correct link to the AD.

2009-05-04

Zenith Grounding

NTSB Asks FAA To Immediately Ground Zodiac CH-601XL Aircraft.
In an unusual move on Tuesday, the NTSB issued an "urgent safety recommendation" asking the FAA to prohibit further flight of the Zodiac CH-601XL, which has been involved in six in-flight structural breakups since 2006. The board cited four accidents in the U.S. and two in Europe in which a CH-601XL broke up in flight, killing a total of 10 people. According to the NTSB, there is a problem with the airplane design that makes it susceptible to aerodynamic flutter -- a phenomenon in which the control surfaces of the airplane can suddenly vibrate, and if unmitigated, can lead to catastrophic structural failure. The NTSB wants the U.S. fleet grounded until the FAA can determine that the problem has been solved. "The NTSB does not often recommend that all airplanes of a particular type be prohibited from further flight," said NTSB Acting Chairman Mark Rosenker. "In this case, we believe such action will save lives. Unless the safety issues with this particular Zodiac model are addressed, we are likely to see more accidents in which pilots and passengers are killed in airplanes that they believed were safe to fly."

The NTSB also found the stick force gradient was not uniform, and was lesser at high Gs, which could make the airplane susceptible to over-control by the pilot, which could lead to over-stressing the design limits and result in in-flight structural failure. The board also made several requests of ASTM International, the entity that provides the design standards for light sport aircraft. The NTSB says ASTM should add requirements to ensure the standards for LSAs reduce the potential for aerodynamic flutter to occur, develop standards on stick-force characteristics that minimize the possibility inadvertent over-controlling by the pilot, and ensure standards for LSAs result in accurate airspeed indications and appropriate documentation in new airplane pilot operating handbooks. For more details, click here for the full text of the NTSB's safety recommendation letter (PDF) and click here for the NTSB letter to the ASTM (PDF).

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