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On July 4, 2009, about 1720 eastern daylight time, a Piper PA-25-235, N4898Y, was substantially damaged during a forced landing near Westerly State Airport (WST), Westerly, Rhode Island. The certificated commercial pilot was not injured. The banner tow flight was operated under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the flight.
According to the pilot, earlier in the day, he flew the airplane on another banner-tow flight that lasted about 3 hours and 45 minutes. After landing, he refueled the airplane from the self-service facility at WST. After fueling, he checked the auxiliary tank drain and the fuel strainer for water. He did not observe any water in the fuel from the auxiliary tank, but he did observe "about an inch" of water the first time he obtained a fuel sample from the fuel strainer, and subsequent checks yielded less water. He repeated the process several times, until no more water was observed, and subsequently departed on the accident flight.
The accident flight lasted about 3 hours, and the pilot reported that the flight was "bumpy." The pilot stated that when he was inbound to and approximately 2 miles from WST, the engine lost all power. At that time, the airplane was at an indicated altitude of approximately 1,000 feet. The pilot "immediately turned towards a golf course," enriched the mixture, applied carburetor heat, and attempted to re-start the engine. The engine did not re-start, and the pilot jettisoned the banner when he realized that the airplane would not be able to reach the golf course. He then steered the airplane for "the smallest trees in the least populated area" that he could reach. The airplane touched down in a clearing, and struck a fence during the rollout.
Federal Aviation Administration (FAA) records indicated that the pilot held a commercial pilot certificate, with airplane single-engine land, multiengine land, and instrument airplane ratings. He also held a glider rating with private pilot privileges. At the time of the accident he had 1,334 total hours of flight experience, including 27 hours in the accident airplane make and model. His most recent flight review was completed in January 2009, and his most recent FAA second-class medical certificate was issued in April 2009.
The PA-25 series airplane was designed and manufactured by Piper Aircraft as an aerial application airplane. The airplane series was certificated in the restricted category, as specified in type certificate 2A10. The accident airplane was manufactured in 1968, and was equipped with a Lycoming O-540 series engine. It was manufactured with a single, 38 gallon fuel tank, located between the engine and the cockpit. The type certificate data sheet specified an unusable fuel quantity of 12 pounds, or approximately 2 gallons.
According to Piper Service Spares Letter number 413, dated May 8, 1998, the new Piper Aircraft Incorporated "officially sold the PA-25 series aircraft to a manufacturer in Argentina. This sale included all drawings, engineering data, parts inventory, tools, catalogs and manuals," and became effective on April 15, 1998. As of that date, Piper no longer provided support for the PA-25 series airplanes.
A review of the FAA airworthiness and registration documentation for the accident airplane revealed that a banner tow hitch and release system was installed in July 2003, and the accident operator (Simmons Aviation Services), purchased the airplane in January 2005. In April 2005, the agricultural agent hoppers were removed, and the airplane was converted to the normal category, in accordance with type certificate 2A8. In September 2005, an auxiliary fuel tank and the "associated plumbing" that was installed by "persons unknown" was removed, and the "fuel system [was] returned to original stock configuration." A review of the FAA airworthiness documentation for the accident airplane did not reveal any information regarding the installation of the auxiliary fuel tank that was removed in 2005.
In June 2006, an aluminum "auxiliary fuel tank with a 38.5 gallon capacity limited to a max of 25.0 gallons [was] fabricated and installed" in the airplane. A sight gauge of "polyurethane tubing" was fabricated and installed. The sight gauge was calibrated in 10 gallon increments "for both ground and level flight attitudes." A pilot-controlled electric pump was installed to transfer fuel from the auxiliary tank to the main tank at a rate of 0.5 gallons per minute. The FAA airworthiness documentation indicated that the auxiliary tank was equipped with a dedicated sump drain, but the documentation did not specify the location of the drain relative to the location of the fuel line pickup.
Airplane maintenance records indicated that the most recent annual inspection was completed on July 3, 2008. The records indicated that as of that date, the airplane had a total time in service of 7,183 hours, and that the hour meter registered 2,554 hours. The records also indicated that as of the annual inspection, the engine had a total time in service of 3,359 hours, and the engine had accumulated 1,702 hours since major overhaul (SMOH).
According to the pilot, the manually-controlled electric fuel pump was used to transfer fuel from the auxiliary tank to the main tank, and the engine obtained fuel from the main tank. The auxiliary tank was equipped with a dedicated sump drain, but the main tank was not equipped with one. A fuel strainer was located between the main tank and the engine.
The 1653 automated weather observation at WST included winds from 250 degrees at 10 knots with gusts to 15 knots, scattered clouds at 6,000 and 7,000 feet, temperature 23 degrees C, dew point 16 degrees C, and an altimeter setting of 29.76 inches of mercury. Visibility was not included in the observation.
WRECKAGE AND IMPACT INFORMATION
According to information provided by the FAA inspectors who responded to the accident scene, the main landing gear was collapsed, and the leading edges of both wings had multiple impact damage sites. The inspectors conducted a check of the engine controls; they stated that all controls were operational, and all functioned as intended. The inspectors noted that approximately 10 gallons of fuel remained on board the airplane, but they did not specify which tank or tanks the fuel was in. The carburetor bowl was opened, and it contained "plenty of fuel," although a small amount of water was also observed in the bowl. The fuel strainer was sampled, and a small amount of water was also recovered from that sample. Together, the two sources, which provided several ounces of fuel, only yielded approximately 1/2 ounce of water. The airplane was secured for additional examination, and the FAA inspectors instructed the operator "not to work on the airplane" until it was determined what other examinations, if any, were necessary.
Engine Examination and Test Run
On July 16, 2009, two FAA inspectors re-visited the airplane at the operator's facility. When they arrived, they observed that there was no fuel in the airplane. The operator informed the FAA inspectors that when he retrieved the airplane after the accident, he removed approximately 4 gallons of fuel from the main tank, and that the auxiliary tank was empty. There were no witnesses to the removal of fuel by the operator.
The inspectors stated that the airplane was equipped with a float-type fuel quantity gauge on the main fuel tank, and that the auxiliary tank was not equipped with a fuel quantity gauge. The main fuel tank quantity gauge was mounted on the upper fuselage skin above the fuel tank, approximately 3 feet ahead of the pilot. The gauge was enclosed in a clear plastic housing, but opacity due to crazing of the plastic prevented the inspectors from being able to read the gauge.
The FAA inspectors conducted an engine cylinder compression check that used a reference input air pressure of 80 pounds per square inch (psi). Four of the cylinders had residual pressure readings of approximately 70 psi, while two had readings in the 50 to 60 psi range. The inspectors attempted to verify magneto and ignition system functionality by rotating the propeller by hand and visually observing for sparks from the plug leads, but the inspectors stated that the test results were inconclusive. They did not provide information on the appearance of the spark plug electrodes. The inspectors added fuel to the main tank, and the engine was observed to start and run normally, with no anomalies.
The FAA inspectors stated that the fuel vendor that sold fuel to the operator checked the vendor's fuel tanks, and no water was found. The vendor also told the FAA inspectors that no other airplanes that the vendor sold fuel to experienced any fuel other contamination problems, including water in the fuel
The operator told the FAA inspectors that the pilot was new to this make and model airplane, and therefore he might not have leaned the engine sufficiently. The implication was that operation of an insufficiently leaned engine would result in increased fuel flow, which could result a fuel exhaustion or starvation event.
Temperature and dew point values for the approximate time and location of the engine failure indicated that the relative humidity was approximately 65 percent. When the intersection of the two temperature values was located on a chart that depicted carburetor ice envelopes, the point was in the region of the chart denoted as "Serious Icing at Glide Power," approximately mid-way between the region denoted as "Icing - Glide and Cruise Power" and the one denoted as "Serious Icing - Cruise Power."