N4864SPiper PA-32-260 · 1970

***This report was modified on 5/3/2011 and 5/23/2011. Please see the docket for this accident for the original factual report and revision history.***

On September 24, 2009, about 2044 eastern daylight time, a Piper PA-32-260 (Cherokee Six), N4864S, was substantially damaged when it impacted terrain following a loss of engine power shortly after takeoff from Oakland/Troy Airport (KVLL), Troy, Michigan. The pilot sustained minor injuries. The flight was registered to Galt Zone, LLC, and operated by a private pilot under the provisions of 14 Code of Federal Regulations Part 91. Night visual meteorological conditions prevailed for the flight, which operated without a flight plan. The flight was originating at the time of the accident and was destined for Hillsdale Municipal Airport, Hillsdale, Michigan.

The pilot reported that he performed a preflight inspection of the airplane, during which he verified the fuel quantity and its distribution between the fuel tanks. He noted that the right and left inboard (main) tanks were nearly empty and that both outboard (tip) tanks were almost full. He stated that he had flown earlier in the day and that his last landing was completed using fuel from the left tip tank. The pilot reported that he did not reposition the fuel selector before the accident flight, and, as such, performed the takeoff using fuel from the left tip tank.

The pilot stated that he did not observe any anomalies with the engine operation during his pre-takeoff engine checks. After the engine checks, he positioned the airplane to the approach end of runway 9 (3,549 feet by 60 feet, dry asphalt) and configured for a short-field takeoff with 20 degrees of flaps. Before starting the takeoff roll, the pilot established takeoff engine power and reconfirmed that there were no issues with engine operation. Shortly after liftoff, as the airplane approached the departure end of the runway, the engine experienced a "quick loss of power," which was shortly followed by a total loss of engine power. The pilot noted that the airplane was too low to perform any emergency checklist items. He stated that, after seeing the stall light flicker momentarily, he focused exclusively on performing a forced landing in a parking lot located immediately north of the departure threshold. During the forced landing, the airplane impacted a shopping cart corral and a tree before sliding down an embankment into another parking lot and grassy area. A postimpact ground fire broke out at the right wingtip, which was quickly extinguished by first responders and the local fire department.

A witness reported hearing the airplane's engine momentarily "stall" after takeoff but then resume operation for a short period of time before it experienced a complete loss of power. Several witnesses saw the accident airplane impact a shopping cart corral and then descend an embankment into another parking lot and grassy area. The witnesses further noted that the pilot had already extracted himself from the airplane upon their arrival and that he did not appear to be seriously injured.

After the accident, the pilot and the airport manager visually inspected the fuel tanks at the accident site. Both main tanks were visibly empty. The right tip tank had been destroyed during the impact and fire and contained no recoverable fuel. The left tip tank appeared to be "full of fuel," according to the pilot. A lieutenant with the local fire department reported that he did not observe any fuel leaking from the airplane and that there was no evidence of a fuel spill at the accident site. The airplane was subsequently recovered to a hangar at KVLL for storage and further examination. The hangar was locked, and the airport manager limited access to the hangar. He indicated that the FAA would define who would have access while the wreckage was in their custody (for example, FAA, NTSB, and possibly insurance representatives or the owner).

On September 28, 2009, FAA inspectors examined the accident airplane at KVLL. In the hangar, the airplane was resting on its fractured right wing and engine because the right main and nose landing gear had collapsed during the accident. In this right-wing-low, nose-low attitude, a visual inspection of the left tip tank showed that the tank appeared to contain between 1/2 and 3/4 of its total 17-gallon capacity. The left main tank contained no visible fuel. The right main tank was void of any visible fuel, but a damaged fuel drain port compromised the tank's integrity. The right tip tank was destroyed and contained no fuel. The cockpit fuel selector was observed positioned on the left tip tank.

On October 6, 2009, FAA inspectors reexamined the accident airplane and conducted an operational engine test run at the NTSB's request. The airplane was lifted to a slightly right-wing-down, near-level pitch attitude for the engine test run. There were no observed fuel leaks when the fuel system was pressurized with the electric fuel pump and using the left tip tank as the fuel source. After an uneventful startup, the engine was run at various engine speeds as the engine throttle was manipulated in the cockpit. Investigators did not note any engine system anomalies on the cockpit engine gauges during the operational test run. According to data downloaded from the accident airplane's engine monitoring system, the engine test run took about 1 minute 17 seconds. The left main tank was drained at the fuel drain port and contained about 1 cup of fuel. The wreckage was released by the FAA but remained in the locked hangar with limited access controlled by the airport manager.

On October 26, 2009, an NTSB investigator and two FAA airworthiness inspectors revisited the hangar. The airplane was still in the postaccident attitude. The investigators observed that the left tip tank appeared to be generally 1/2 to 3/4 full. The NTSB investigator had the airplane leveled and then observed that the left tip tank appeared to be generally 1/4 to 1/2 full. There was no loss of fuel between the two observations of "1/2 to 3/4 tank" and "1/4 to 1/2 tank," and there was no evidence of a fuel leak at the accident site or in the hangar where the airplane was stored. The left main and left tip tanks were drained using the airplane's electric fuel pump, and the fuel was collected from the carburetor inlet fuel line. The left main tank contained about 75 fluid ounces (0.6 gallons) of fuel. The left tip tank contained about 4.5 gallons of fuel. (All of the recovered fuel was blue in color, consistent with 100 low lead aviation fuel, and did not contain any water or particulate contamination.) The right main tank was reconfirmed empty of any fuel.

The left tip tank was removed, and the 4.5 gallons of fuel previously recovered was returned to the tank. The fuel outlet port was located near the aft, inboard corner of the fuel tank. The fuel tank was rotated about the longitudinal and lateral axes to determine if the position of the tank's outlet port could allow air to enter the outlet fuel line. With 4.5 gallons of fuel in the tank, the tank was rotated 7 degrees to the right to align the tank with the wing's dihedral of 7 degrees. Starting at the 7-degree attitude, the tank was rotated 20.5 degrees to the left until the tank's fuel outlet port became uncovered. The static test was not representative of an airplane that was banked 20.5 degrees while in coordinated flight; however, it provided a measure of the lateral acceleration necessary in uncoordinated flight or a turning takeoff to unport the tank. The position of the fuel outlet did not allow air to enter the outflow line when positioned at positive pitch angles or in a right-wing-low attitude.

Above the fuel selector assembly was a black placard with white lettering, part number 69192, which stated the following: "All Weight In Excess of 3112 Pounds Must Be Fuel Weight Only; Fill Tip Tanks First, Use Main Tanks First; Restrict Passenger Weights or Cargo Weight As Required For Compliance."

Both propeller blades had leading-edge damage, and their blade tips were curled aft. An inspection of the accident site revealed four distinct strike marks in the asphalt parking lot consistent with damage caused by a rotating propeller. The distance between the first two propeller slash marks was 41 inches. The distance between the second and third marks was 48.5 inches. The distance between the third and fourth marks was 72 inches.

During a postaccident interview with an FAA inspector, the pilot stated that after the loss of engine power, he had reached for the fuel selector but was unsure of what he did because his attention was diverted by the stall warning light.

The pilot reported to the NTSB investigator that the loss of engine power during initial climb was likely due to fuel starvation, as a result of fuel sloshing in the left tip tank during rotation and initial climb. The pilot also contended that the left tip tank contained 1/2 to 3/4 of its 17-gallon capacity before the accident flight.

--- Fuel Consumption Calculations

According to the pilot's flight log and related email correspondence, the accident airplane was last fueled on September 2, 2009, after completing a cross-country trip from South Carolina to Michigan. According to the records obtained from the fuel vendor at KVLL, the airplane was fueled with 46.43 gallons. The pilot reported that the airplane's four fuel tanks were at their full capacity (84 gallons total) after being "topped-off" with the 46.43 gallons. The previous flight was 3.9 hours at 10,000 feet, according to engine monitor and global positioning system (GPS) data. The average rate of fuel use was calculated at 11.9 gallons per hour (gph). The 11.9-gph value assumes that the fuel tanks were topped off completely and consistently after the last two flights in which refueling occurred.

The pilot's flight log showed 4.7 hours were accumulated since the last time the airplane had been fueled (including the accident flight). A data download of the airplane's engine monitoring system indicated that the engine had operated, with a positive oil pressure indication, for 4 hours 29 minutes 11 seconds since the airplane was last fueled. The engine monitoring data collection unit was powered by an electronics master switch and recorded at 1-minute intervals. The data collection unit did not record engine speed, manifold pressure, fuel pressure, or fuel flow.

According to performance data in the 1970 Piper PA-32-260 Owner's Handbook, the fuel consumption rate at 75-percent engine power was 14 gph. The fuel consumption rate at 65-percent engine power was 12.2 gph. The pilot indicated that he typically flew the accident airplane at a lean-of-peak (LOP) fuel economy setting. He had equipped the airplane with a turbo-normalizer system and engine monitor to achieve the lower fuel burn rates by operating LOP. The pilot further stated that he would run LOP during cruise climb and cruise. He stated that he would operate per the owner's handbook for takeoff and landing. He reported that the airplane's average fuel burn was 11 to 12 gph for the six-cylinder, 260 horsepower, Lycoming model O 540-E4B5 engine.

At the time of the accident, the airplane's engine had operated for about 4.5 hours since the airplane had been fueled. The calculated average fuel consumption of 11.9 gph would yield a fuel usage of about 54 gallons. The airplane's maximum fuel capacity was 84 gallons. The maximum amount of fuel remaining would have been about 30 gallons if the fuel tanks had been fully topped off and the average fuel burn rate remained at the calculated 11.9 gph.

The accident airplane's 84-gallon fuel capacity was distributed among two 25-gallon main tanks and two 17-gallon tip tanks. The pilot reported that since the last refueling, he used fuel from both main fuel tanks before selecting the left tip tank. He further noted that the main tanks were empty and that he had not used any fuel from the right tip tank. In the absence of any recorded fuel flow data, the amount of fuel used since the last refueling could not be determined with precision. After the accident, the airplane had about 22 gallons of fuel on board (4 1/2 gallons in the left tip, about 1/2 gallon in the left main, empty right main with no odor of spilled fuel, and 17 gallons or less in the right tip).

--- Airplane Flight Manual (AFM) and Owner's Handbook

The applicable Owner's Handbook for the Piper PA-32-260, serial number 1288, was 753-809 (691915). The handbook advised that each tank contains about 1 pint of unusable fuel. When using less than the standard 84-gallon capacity of the tanks, fuel should be distributed equally between each side and may be placed in either the main or tip tanks. An electric fuel pump was provided in case the engine-driven fuel pump fails. The electric pump operated from a single switch and should be ON for all takeoffs and landings. Before takeoff, pilots should verify the operation of the engine-driven fuel pump by observing fuel pressure with the electric fuel pump OFF. The electric fuel pump should remain ON during takeoff until the airplane has reached a safe altitude during the initial climb. The fuel pump should remain OFF during the cruise-climb, cruise, and cruise-descent flight segments. The electric fuel pump should be turned ON during the final landing approach and landing to ensure adequate fuel pressure if a balked landing occurs.

The handbook recommends that the takeoff be made on the fullest main tank to ensure best fuel flow, and this tank should be selected before or immediately after starting to allow fuel flow to be adequately established before takeoff. The main or tip tank with the highest quantity of fuel should be selected for landing. The handbook does not address takeoffs using the tip tanks or when the main tanks are empty.

The AFM required to be in the airplane was Report VB-156, revision 7 (11-30-78). The pilot had Report VB-156, revision 6 (7-25-75) in the airplane, which was not the current version. Revision 7 changed Placard No. 6 and revised the loading limitations to remove reference to seven-passenger operation. Otherwise, the placard remained the same as revision 6. The placard required by revision 7 should state as follows: "ALL WEIGHT IN EXCESS OF 3112 POUNDS MUST BE FUEL WEIGHT ONLY, FILL TIP TANKS FIRST, USE MAIN TANKS FIRST." That placard was installed in the accident airplane.

The Loading Limitations, page 4, were also modified by revision 7 to remove reference to the seven passenger operation. Otherwise, the limitations remained the same as revision 6 and stated as follows: "1. Fill tip tanks first; use main tanks first; 2. This airplane must not be operated at gross weights in excess of 3,112 pounds unless the weight over 3,112 pounds is fuel weight only; 3. Remove fuel from the main tanks first when required for proper weight and balance."

---Maneuvers Required To Unport the Left Tip Tank

Postaccident static testing showed that the left tip tank outlet would unport during a turn on the ground if the tank contained 4.5 gallons of fuel and the lateral acceleration at the tip tank reached about 0.35 Gs. (A report titled "LATERAL ACCELERATION AT TIP TANK" is in the docket and contains further information.) Recorded GPS data showed that the airplane likely slowed to less than 10 miles per hour and turned 90 degrees to align with the runway to the accident flight takeoff. Calculations showed that, to achieve a lateral acceleration of 0.35 Gs at the tip tank at 10 miles per hour, the 90-degree turn for runway alignment would have to be started and completed within 2 seconds. In addition, the unported condition would persist for 2 seconds or less. After liftoff, the high pitch attitude, high angle of attack, and high climb angle would further increase the fuel level at the outlet port and also increase the lateral Gs required to unport the tank.

--- Fuel Starvation Tests, Time From Unporting to Engine Stoppage

Several fuel starvation tests were made on another Piper PA-32-260. If the engine was started with the fuel tank selector in the OFF position, the engine would run more than 3 minutes at idle or about 30 seconds at full throttle. If the engine was running and the fuel tank selector was switched to an empty main tank, the engine would run for more than 6 minutes at idle or about 35 seconds at full throttle. If the engine was running and the fuel selector was switched to an empty tip tank, the engine would run for more than 8 minutes at idle or about 40 seconds at full power.

Recorded GPS data of the accident flight showed that the loss of engine power likely occurred 22 to 27 seconds after the takeoff roll was initiated.

--- Postaccident Timeline

9/24/09 Accident.

9/24/09 Pilot provided statement to FAA.

9/24/09 FAA requested that KVLL manager secure airplane.

9/24/09 Pilot and KVLL manager observed a nearly full tip tank with airplane at the accident location in the postcrash attitude. The airplane was then moved to a locked hangar to await the FAA's arrival.

9/28/09 FAA observed 1/2 to 3/4 left tip tank. The airplane was resting at the postcrash attitude.

10/1/09 FAA reviewed aircraft and pilot documents and records.

10/1/09 FAA interviewed pilot.

10/6/09 At the request of the NTSB, FAA started and ran engine for 1+ minute.

10/13/09 Airplane released by FAA. NTSB concurred (NTSB never took custody of wreckage).

10/25/09 Permission granted by pilot to examine tank and unporting issue.

10/26/09 NTSB investigator and FAA visited the airplane. The airplane was in the postcrash attitude, airplane nose down and right wing down. It appeared to have 1/2 to 3/4 tank of fuel in left tip tank. The tank contained 4 1/2 gallons of fuel. The hangar had been locked at all times unless persons with a specific need for access were allowed in the hangar (such as NTSB, FAA, and insurance).