See also Exxon’s November 25 recall.
See also Exxon’s November 27 recall.
See also Exxon’s technical Q&A (November 28).
See also Special Airworthiness Information Bulletin (December 11).
Last week, Texaco alerted fixed-base operators (FBOs) and marketers who received avgas from the Pennsauken (New Jersey) Terminal from September 9, 1998, to the present; and Providence (Rhode Island) Terminal from October 29 to the present that fuel from these locations had been found to be off-specification.
Texaco requested that FBOs and marketers cease sale of the fuel and advise aircraft owners/operators to drain the fuel from their aircraft and refill with fuel meeting specifications. This step was taken as a precautionary measure when the avgas in question failed ASTM D 130, “Standard Test Method for Detection of Copper Corrosion from Petroleum Products by the Copper Strip Tarnish Test”. This test method indicates the propensity of a fuel to tarnish or corrode copper or its alloys. Since the effects of tarnishing or corrosion are long term in nature, it was determined there was no immediate danger or safety compromise to aircraft containing this fuel. The copper strip tarnish test is only one of a battery of tests to which the fuel was subjected, and in all other tests the avgas met specifications.
In addition to this precautionary measure, Texaco determined that thorough filtering of the affected product brought the fuel back into specification; thus a filtering program began on November 26. In fact, subsequent sampling at the point of entry into the aircraft indicated that proper fuel filtering precluded off-specification fuel from being introduced into the aircraft fuel system. We believe that the filtering program offers an immediate and complete solution, and we will continue this effort until all suspect fuel passes the specification test.
Long-term exposure to the suspect fuel, such as putting the aircraft up for the winter or other static storage, should be avoided. The sooner the suspect avgas is removed from the aircraft, the better it is for the engine, airframe, and fuel system. However, if the fuel has already been consumed, there should be no residual effect on the metal parts of the engine, airframe, or fuel system. Also, it is important to note that no field samples tested showed evidence of copper corrosion; none exceeded the dark tarnish standard rating.
The Pennsauken avgas tank remains closed. However, as of Monday, November 30, fresh specification-compliant fuel was delivered to the Providence Terminal, and avgas deliveries have resumed.
Texaco has established an information line at 888/813-4527 to assist customers with any questions about these recommendations or technical concerns regarding the fuel.
This letter is supplementary to the previous notification from Texaco regarding the Copper Strip test. It is intended to clarify the meaning of the test and how its results might affect your customers’ aircraft.
It is important that pilots, owners, and maintenance personnel understand that if the suspect fuel is drained from the aircraft fuel system within a reasonable period of time, no adverse effects to the engine, airframe, or fuel system should be encountered. Since tarnishing and corrosion of copper and copper alloys is long term in nature, there is no immediate danger or safety compromise to aircraft containing this fuel. However, long-term exposure to the fuel, such as putting the aircraft up for the winter or other static storage, should be avoided. The sooner the off-specification avgas is removed from the aircraft, the better it is for the engine, airframe, and fuel system.
Texaco has issued procedures to all affected FBOs in an effort to assist pilots/owners regarding the proper action to reduce the possibility of tarnish/corrosion of copper or copper alloy fuel system parts in aircraft fueled with the suspect avgas. Please avail yourself of this service so that the fuel may be reclaimed and replaced. Should you have any questions regarding the test for copper strip tarnish, see the question/answer section below.
Question: What is the copper strip test all about?
Answer: The copper strip test is technically an ASTM standardized test method known as ASTM D 130, Standard Test Method for Detection of Copper Corrosion from Petroleum Products by the Copper Strip Tarnish Test. The test procedure involves submersing a polished copper strip into the fuel in a laboratory test tube. The test tube is then inserted into a steel “bomb” and placed in a boiling water bath. After two hours in the bath, the copper strip is removed, washed with solvent, and rated by visually comparing it to a standard scale of color photographs. The scale ranges are: 1a-1b (slight tarnish), 2a-2e (moderate tarnish), 3a-3b (dark tarnish), and 4a-4c (corrosion). Avgas must rate 1a or 1b to pass the test.
Question: Why is this test important to my fuel system?
Answer: The copper strip test helps to indicate the propensity of a fuel to tarnish or corrode copper or its alloys (usually bronze and brass) in engines, airframes, and fuel systems. Parts made from these alloys are particularly susceptible to corrosion from certain sulfur compounds that may be present in the fuel. For this reason, the avgas specification (ASTM D 910) also limits sulfur in the fuel to a maximum of 0.05 mass percent.
Question: Is safety compromised if I fly with this fuel?
Answer: No. Tests conducted at Texaco’s R&D laboratory in Beacon, New York, have shown that this fuel is not corrosive (worst case was 3a/3b—dark tarnish), so there is no safety compromise. Also, the concentration of sulfur in the suspect fuel was determined to be well below the maximum specification limit of 0.05 mass percent.
Question: Then why is it important to remove the fuel from my aircraft as soon as possible?
Answer: Again, although this type of tarnishing would take place over a long period of time, it is not prudent to subject parts to continuous exposure any longer than necessary.
Question: How can I find out even more about the copper strip test or other tests and specifications for aviation gasoline?
Answer: You may contact ASTM (American Society for Testing and Materials) at 610/832-9500 or visit its Web site.
December 02, 1998