N7663YPiper PA-30 · 1965

On September 21, 2016, about 1920 central daylight time, a Piper PA-30 airplane, N7663Y, was substantially damaged following a forced landing near Mineral Wells Airport (MWL), Mineral Wells, Texas. The airline transport certificated pilot and one passenger were seriously injured and one passenger was not injured. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no Federal Aviation Administration (FAA) flight plan had been filed for the flight. The cross-country flight departed Marfa Municipal Airport (MRF), Marfa, Texas, at 1655 and was en route to MWL.According to the written statements provided by the pilot, he departed Draughon-Miller Central Texas Regional Airport (TPL), Temple, Texas, on the day of the accident, to fly to MRF to pick up two passengers. He wrote that when he departed TPL the main fuel tanks, the auxiliary fuel tanks, and the tip tanks were all full; a total of 114 gallons of useable fuel. After landing at MRF 19.38 gallons of fuel were added. The pilot did not recall how many gallons were added in each tank; he only recalled that he did not add fuel to the tip tanks as he had "burned those off on the way" from TPL to MRF. The pilot was assisted in fueling the airplane by an airport employee.

In the written statements submitted by the pilot, he described using the "Shadin fuel flow [instrument] to lean each engine to 8.7 to 8.9 gallons per hour at level cruise." He also described using fuel out of the tip tanks by switching "the little silver switch" to burn fuel out of the tips." The pilot did not mention the position of the fuel selector valve handle or the illumination of the red fuel transfer light when the tip tanks were selected. During the flight from TPL to MRF, he estimated flying on the tip tanks for one hour and twenty minutes and then flying on the auxiliary fuel tanks for an additional hour and ten minutes. He used the main fuel tanks for takeoff and landing only.

The pilot wrote that during the flight from MRF to MWL he only flew on the auxiliary tanks and the main tanks. As the flight passed San Angelo, Texas, he switched back to main tanks and remained in that position for the duration of the flight. While on approach to runway 13 at MWL, he advanced the mixtures to rich about 7 to 10 miles from the runway, at which time the right engine began to surge. He "turned on both electric fuel boost pumps" and established that the fuel gauges did not indicate anything abnormal. He elected not to shut down the right engine.

As the pilot maneuvered the airplane for landing, the left engine started to "do the same thing" as the right engine. The airplane started to "loose [sic] airspeed" and the pilot maneuvered the airplane for a forced landing in the "clear", away from trees and obstacles.

During the impact with the ground, the fuselage and wings were crushed and wrinkled and the empennage separated partially from the fuselage. The airplane was recovered to a hangar for examination under the auspices of the National Transportation Safety Board, assisted by a FAA inspector, and air safety investigators from Piper Aircraft and Lycoming Engines.

The right wing fuel system included the tip tank (15 gallons useable), outboard or auxiliary tank (15 gallons useable), and the inboard or main tank (30 gallons total, 27 gallons usable). The right tip tank was impact damaged and compromised. No fuel was recovered from the tip tank. The damage to the tip tank was consistent with the fuel tank being full at the time of impact.

The right auxiliary tank fuel cap was in place and the bladder was in place but was crushed up and wrinkled consistent with the impact damage to the wing. The auxiliary tank was borescoped and revealed no anomalies and no evidence of tearing or breach of the fuel tank bladder. The tank float was unremarkable. Evidence of fuel was documented at the finger screen and there was no evidence of a fuel leak on the upper or lower surface of the wing.

The right main tank fuel cap and bladder were in place. The main tank was borescoped and revealed no anomalies and no evidence of tearing or breach of the fuel tank bladder. The tank float was unremarkable. One gallon of fuel was recovered from the right main tank fuel lines.

The right side fuel filter was removed and exhibited trace fuel. There was no evidence of visible contamination in the fuel filter.

The left wing fuel system included the tip tank (15 gallons useable), outboard or auxiliary tank (15 gallons useable), and the inboard or main tank (30 gallons total, 27 gallons useable). The left tip tank was impact damaged and compromised. No fuel was recovered from the tip tank. The damage to the tip tank was consistent with the fuel tank being full at the time of impact.

The left auxiliary tank fuel cap and bladder were in place and the bladder was wet with a small amount of fuel on the bottom. The auxiliary tank was borescoped with no evidence of tearing or breach of the fuel tank bladder. The tank float was unremarkable. Evidence of fuel was documented at the finger screen and there was no evidence of a fuel leak on the upper or lower surface of the wing. Three gallons of fuel were drained from the left auxiliary tank.

The left main tank fuel cap and bladder were in place. There was no evidence of fuel in bladder. The main tank was borescope with no evidence of tearing or breach of the fuel tank bladder. The tank float was unremarkable.

The left side fuel filter was removed and exhibited trace fuel. There was no evidence of visible contamination in the fuel filter.

The tip tank fuel lines for the left and right tanks contained several ounces of fuel. When the lines were opened and the solenoid activated the tip tank light illuminated.

The forward fuel sump contained 3 ounces of fuel. The filter was free of visual contamination. The rear fuel sump contained 2 ounces fuel. The filter was free of visual contamination.

There were no mechanical anomalies with the airplane fuel system that would have precluded normal operation at the time of the accident.

The left engine data plate identified the engine as a Lycoming IO 320 B1A. The upper bank of spark plugs were removed and illustrated signatures consistent with lean state. The internal exhaust tubing was white in color/residue consistent with a lean mixture. No evidence of fuel was found in the main fuel line between the fuel pump and manifold. Both magnetos were removed and driven with a power drill. Spark was observed on all leads. The engine was rotated through at the propeller. Tactile and audible detection of air movement was documented on all cylinders. Valve train and accessory case continuity was confirmed. The turbocharger spun freely when rotated by hand.

The fuel pump was rotated through by hand without resistance or hesitation. The fuel screen was free of visual contaminants. The fuel injector nozzles were free of visible particulates. There was no evidence of fuel in the engine. There were no mechanical anomalies with the left engine that would have precluded normal operation at the time of the accident.

The right engine data plate identified the engine as a Lycoming IO 320 B1A. The upper bank of spark plugs were removed and illustrated signatures consistent with lean state. The internal exhaust tubing was white in color/residue consistent with a lean mixture. No evidence of fuel was found in the main fuel line between the fuel pump and manifold. The magnetos were removed and driven with a power drill. Spark was observed on all leads. The engine was rotated through at the propeller. Tactile and audible detection of air movement was documented on all cylinders. Valve train and accessory case continuity was confirmed. The turbocharger spun freely when rotated by hand.

The fuel pump rotated through by hand without resistance or hesitation. The fuel screen was free of visual contaminants. The fuel injector nozzles were free of visible particulates. Trace fuel was observed in the fuel servo. There were no mechanical anomalies with the right engine that would have precluded normal operation at the time of the accident.

According to the Piper PA-30 Owners Handbook and the Piper PA-30 Turbo Twin Comanche (located in the accident airplane), the airplane as equipped had 114 gallons of useable fuel. The manual stated, "Fuel should be used from the main fuel cells during take-off, landing, climb, and descent. Auxiliary fuel and tip tank fuel is to be used in level flight only."

The "Tip/Aux Fuel Management Instructions" placard in the airplane, just above the fuel selector valves, advised on the fuel selector valve handle and toggle switch placement to select fuel from each tank. Specifically for fuel use from the tip tank, the fuel selector valve handle should be selected in the aux position and the toggle switch selected to tip tanks.