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Where Did the Water Contamination come from?

I have had several people inquire about the source of the water contamination that I experienced. The history of events in my letter to the FAA dated April 1999 that is available on the documents page provides some details on this topic. Since the history of events requires a lot of reading, here I have consolidated these details into a more general explanation that, hopefully, will explain that it doesn't matter where the water contamination came from.

First, my aircraft's fuel caps and access plates were inspected during the tests that were performed. These items proved to be in excellent condition, and maintenance history indicates that they are not the source of water contamination. I purchased my aircraft new in 1981, and with few exceptions, when parked, it is normally kept in a hangar.

Research indicates that water contamination occurred from small quantities of water accumulating over a period of years from condensation and fueling services.

For years, before every flight, I took fuel samples from my aircraft's sump drains during preflight checks, and not once did I detect water contamination in a fuel sample taken from the integral wing tank sump drains. It was my aircraft's mechanic and a FAA representative on scene at the incident of my emergency landing in a field who, for the first time, drained a sample of fuel from a sump drain that showed evidence of water contamination. Following this event, myself, a FAA representative, and the airport manager investigated the fuel services at the airport where I last refueled. Our investigation revealed that the water contamination (about 10 to 12 ounces) found at the incident was not introduced from the airport's fueling services.

Tracing the source of water contamination and correcting the problem is an obvious safety precaution for prevention once it is known to exist. The chronological order of when someone detects water contamination within a chain of events is all-important. If it is not detected during a preflight check, it may reveal itself in-flight resulting in an engine failure that may lead to a forced emergency landing. Regardless of the source of water contamination, a pilot must be able to detect it during his or her preflight check.

Cessna's integral wing tank drainage system can not be trusted to reveal water contamination during a normal preflight check. Given the design of the integral wing tank, if water contamination is discovered and the system is completely drained using every means possible to insure the water contamination has been removed, then simply refueling the aircraft puts a pilot right back into an unknown situation. Taking a fuel sample soon after refueling may or may not reveal if water contamination is present from the refueling. It's a catch-22. In this circumstance, with knowledge of the problem, a real burden of responsibility is placed on a pilot to make a prudent decision to ground the aircraft. If no water contamination is detected, a pilot may make the decision to risk continuing with the flight, but this decision is not fair to or safe for the public over whom the flight will be made.

Water contamination is not a new problem. It is one with which Cessna has experience. I highlight this issue because Cessna has a history of diverting attention away from the real problem--their certified engineering designs that do not function as certified.

For example, AD 84-10-01 R1 (Bladder fuel cells) became effective in 1988. This AD places significant emphasis on the fuel caps. The significance of the bladder tank design is seemingly irrelevant, but it is the bladder tank design that is the source of the problem, not the fuel caps.

In a more recent example, Cessna in correspondence with me has attempted to divert my attention away from their engineering design problems by focusing attention on the source of water contamination. Cessna has not admitted to me that there is a problem with the design of their integral wing tank drainage system. Basically, Cessna has told me that their design meets certification requirements, and they have attempted to turn my attention away from design issues by over shadowing them with emphasis on sources of and correctional procedures for water contamination. You may read the correspondence to which I'm referring to in a letter that I received from Cessna regarding the problem.

For about sixteen years, I placed a lot of confidence in the FAA certification of my aircraft. I now know that it was dangerous to be as confident as I was. Until I experienced one in-flight rough running engine and three in-flight engine failures, I never asked myself, "Why do I never detect water contamination in a fuel sample during a preflight check"? With blind faith, I assumed that the integral wing tank's drainage system works as certified.

Some of you may want to do your own review of NTSB reports for accidents involving engine failure and water contamination that have probable causes that blame weather or pilots. View the reports with the assumption that pilots perform a proper preflight check on an aircraft that has a flawed fuel drainage system. Then ask yourself, "When the engine quit, did it matter where the water came from"? My answer is no. What matters in this assumption is that a pilot performs a proper preflight check and does not detect water contamination.

Yes, it is important to discover the source of water contamination, but it is more important to detect it once it is present.

Here are three NTSB reports for your review.

NTSB Identification: CHI84LA008

NTSB Identification: CHI85FA054

NTSB Identification: CHI92FA020


Or, search the NTSB database for more reports.

If you have questions or comments about this topic, please post them to the Sump This Message Board.

Robert E. Scovill, Jr.


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