GUTHRIE, OK, USA
N4410P
Piper PA-23-160
During a multi-engine certification check flight, the left engine was shut down and feathered. The designated pilot examiner then had the applicant restart the engine. The restart was unsuccessful, and the examiner took control of the aircraft, returning to the originating airport. The applicant performed the manual gear extension procedures, but the landing gear position could not be verified, and the gear was not down and locked on final approach. The examiner executed a go-around; however, the airplane was unable to maintain altitude. The airplane impacted trees, and terrain while descending during the go-around. A post impact fire destroyed the aircraft. The landing gar was found in the retracted position, and the left propeller was found in the retracted position, and the left propeller was found feathered. Metallurgical examination found areas of electrical arcing in the part of the starter cable passing through the wing root. When the left engine starter was energized using an exemplary cable, the starter rotated the engine crankshaft. Density altitude was calculated at 3,100 feet. The aircraft manufacturer reported ad single-engine aircraft climb capability of -7 feet per minute with the landing gear extended.
HISTORY OF FLIGHT: On May 18, 1998, at 1820 central daylight time, a Piper PA-23-160 twin engine airplane, N4410P, registered to Seward Leasing, Inc., and operated by Crabtree Aircraft Company, Inc., of Guthrie, Oklahoma, as a 14 CFR Part 91 flight, crashed while attempting a single engine go-around at the Guthrie Municipal Airport. Visual meteorological conditions prevailed and a flight plan was not filed. The airplane was destroyed by a post impact fire. The commercial pilot/flight instructor who was designated by the FAA as a pilot examiner was conducting a commercial multiengine certification flight check for a private pilot. The pilot examiner, and the passenger received fatal thermal injuries during the post impact fire and the private pilot received serious thermal injuries. The flight originated from Guthrie at 1800. According to the operator and the private pilot's flight instructor, the flight departed with the main fuel tanks full (72 gallons) of 100LL aviation fuel for the purpose of conducting the flight portion of the practical examination for the commercial multiengine certification. The FAA Designated Pilot Examiner (DPE) was seated in the right seat to administer the flight portion of the examination. The flight instructor reported that during the private pilot's training, he had shut down and feathered the right engine; however, he never shut down and feathered the left engine during the private pilot's training. The private pilot had received ground instruction on the emergency gear extension procedures and had used the emergency gear extension handle to extend the flaps during preflight inspections only. During interviews conducted by the investigator-in-charge, and on the enclosed statement, the private pilot reported that the flight check was being conducted at 3,500 feet msl. During the latter portion of the flight check, the pilot examiner requested that the applicant shut down, feather, and then restart the left engine. During the restart procedures, the left engine propeller would not rotate and the engine would not restart. The airplane was loosing altitude and the pilot examiner took control of the airplane for the return flight to the airport. The pilot examiner flew the airplane at the single engine best rate-of-climb speed for a downwind entry for runway 16 at the Guthrie Municipal Airport. The landing gear handle was placed in the down position and the emergency gear extension procedure performed. However, on final approach at 1,700 feet msl, the private pilot noticed that there were no green lights, indicating that the gear was not fully extended. When the private pilot advised the pilot examiner that there were no green gear lights, the examiner directed the private pilot to perform the gear retraction procedures while she continued to fly the airplane for a go-around. The private pilot performed the emergency gear retraction procedure. The pilot examiner flew the airplane with the throttle full forward for the right engine and the airspeed at the single engine best rate-of-climb speed; however, the airplane did not maintain altitude. During the forced landing, the wings of the airplane struck trees and the ground. The door of the airplane jammed; however, the private pilot and the passenger kicked the door open to egress the airplane. A post impact fire erupted in the right engine and spread to the surrounding grass. The Guthrie Police Chief, traveling southbound on Division Street, observed the beige airplane during the base to final turn for runway 16. Within less than 5 minutes, he saw the smoke coming from the accident site. A witness, driving northbound on Interstate 35 observed the airplane flying "just above the tree tops. The [air]plane was rocking from side to side but was level." The landing gear was not down and there was no visible smoke or fire while the airplane was airborne. Other witnesses, who observed the airplane descending near a construction area along Interstate 35, reported that the airplane barely missed hitting a 70 foot construction crane boom and high lines before descending toward the ground. PERSONAL INFORMATION: The FAA records reviewed by the investigator-in-charge (IIC) revealed that the FAA Designated Pilot Examiner (DPE)/commercial pilot reported a total flight time of 10,000 hours on her last medical certificate application dated January 2, 1998. Pilot weight on the medical certificate was 149 pounds. The commercial pilot/flight instructor had been authorized as a DPE for airplanes since 1989. She was the chief pilot/flight school manager for Crabtree Aircraft Company, Inc., a FAA Designated Written Test Examiner, a FAA Accident Prevention Counselor, and a Gold Seal Flight Instructor. At the time of the accident, the DPE was authorized by the FAA to perform the duties of pilot examiner in the following multiengine aircraft: BE-55, BE-58, CE-310, and the PA-23. On March 11, 1998, the DPE received a FAA flight check in N4410P during the annual renewal of her examiner designation. This 0.9 hour flight included stalls, VMC demonstrations, steep turns, single engine (zero thrust) landings, and cross wind landings. The FAA and flight school records revealed that the multiengine applicant received his private pilot certificate with the airplane single engine land rating on June 2, 1997. He added the instrument rating on December 17, 1997. In April, 1998, he received 8.2 hours of dual instruction toward the commercial single engine land rating. In May 1998, he received 20.2 hours of dual instruction for the commercial multiengine land rating. The accident occurred during his commercial multiengine certification flight check. The pilot weight on his medical certificate was 145 pounds. The Oklahoma Drivers License for the passenger listed his weight as 185 pounds. AIRCRAFT INFORMATION: The aircraft (serial number 23-1922) was manufactured in 1960 and registered to the current owner in 1995. Aircraft records revealed that the carbon dioxide bottle for the emergency gear extension was replaced in February 1995. The last recorded maintenance on the aircraft was a 100 hour inspection. This inspection was conducted at 3,491.0 hours total aircraft time on May 5, 1998. At the time of this inspection, the left engine (O-360-A1A, serial number L-13515-36A) had 2,430.0 hours total time and the right engine (serial number L-13514-36A) had 2,484.95 hours total time. At the time of the entry, the operator's maintenance board indicated that 78.6 hours remained until the time of the next inspection. The 180 horsepower engines were installed new on the aircraft on October 21, 1968, at an aircraft time of 1,006 hours, in accordance with a Doyn Aircraft supplemental type certificate (STC) installation. The propellers (HC-C2YK-2RBS) were inspected at the last 100 hour inspection with no discrepancies noted. At the time of this inspection, the propellers had accumulated 1,028 hours since the last propeller overhaul in June 1997. The left engine maintenance records stated that in November 1968 an overhauled starter was installed on the left engine. A work order dated November 16, 1996, stated "L[eft/H[and] starter Inop[erative] Replace Starter with O[ver]/Hauled Unit." A work order dated May 9, 1997, stated "Remove L[eft] H[and] Starter replace Drive & Reinstall." METEOROLOGICAL INFORMATION: The National Weather Service Observation for Guthrie at 1853 indicated that the winds were from 160 degrees at 11 knots. Visibility was 10 statute miles with a temperature of 32 degrees Centigrade [89.9 degrees Fahrenheit] a dewpoint of 21 degrees Centigrade [69.8 degrees Fahrenheit]. The IIC calculated the density altitude at 3,100 feet. The Oklahoma Climatological Survey at the University of Oklahoma, Norman, Oklahoma, reported that the Oklahoma Mesonet Guthrie site (2.5 miles west of the Guthrie Municipal Airport) at 1820 indicated winds from 174 degrees at 20 mph with a temperature of 88 degrees Fahrenheit. AERODROME INFORMATION: The Airport Facility Directory list the Guthrie Municipal Airport as a non-towered airport with runways 16/34 and 18/36. Runway 16 is a concrete surfaced runway, 4,102 feet long, and 75 feet wide. The airport elevation is 1,068 feet. WRECKAGE AND IMPACT INFORMATION: The IIC examined the accident site, elevation of 1,066 feet, (35 degrees 49 minutes North; 97 degrees 24 minutes West) approximately 2 miles south of the approach end of runway 16, and found the wreckage distribution path was on a measured magnetic heading of 210 degrees. The initial point of impact was a tree where portions of the outboard right wing, right aileron, and the green navigation lens were found at the base of the tree. This tree exhibited gouges and scrapes measured at 60 inches agl. Sixty-eight feet south of that tree, the empennage was located at the base of a tree with scrapes and gouges measured 48 inches agl. The aircraft came to rest on a measured magnetic heading of 145 degrees at 115 feet from the initial impact point. The nose area of the airplane was crushed aft. See the wreckage diagram for additional details. The cabin, cockpit, and the aircraft door were destroyed by the post impact fire. The landing gear was found in the retracted position. Flight control continuity was confirmed. All flight controls and the aileron counterweights were accounted for at the site. Fire and impact damage precluded a determination of the flap positions. The engines remained attached to the respective engine mounts with thermal damage on the case and the accessories. Crankshafts on both engines were rotated by hand, thumb compression was noted on all the cylinders, and there was continuity to the accessory gears. During rotation of the crankshaft, the impulse coupling on the left magneto for each engine operated. Each engine starter remained attached to the engine, and the respective starter gear was found in the retracted position. Oil pressure screens and fuel screens were free of debris. A hydraulic pump (Gear 1P677, serial number 7809) was observed on the rear accessory case of the left engine. The hydraulic pump was intact and secure. On the left engine, one of the propeller blades was bent aft with scratches near the tip. The spinner dome was removed and the propeller feathering pressure was measured at 77 psi (at 82 degrees Fahrenheit) using a tire pressure gauge at the valve. On the right engine, both propeller blades were bent aft with diagonal chordwise striations near the tip. When the propeller feathering pressure was checked, the tire pressure gauge pegged at 125 psi. MEDICAL AND PATHOLOGICAL INFORMATION: On June 1, 1998, the pilot examiner succumbed to thermal injuries sustained during the accident. The passenger succumbed to his thermal injuries on June 12. 1998. Autopsies and toxicology were not requested by the Board due to the length of time that had passed since the accident. TEST AND RESEARCH: The airplane was examined June 2, 1998, at Lancaster, Texas, under the surveillance of the IIC. On the left engine, the front portion of the starter power wire, which ran along the left side adjacent to the engine, retained a portion of its insulation. Aft of the left side of the engine, all insulation areas exhibited physical evidence of thermal destruction. In the area of the engine accessory section, forward of the firewall, individual stands of the starter wire were found melted together forming a solid radial depression. The depth of the depression was approximately 50 per cent of the wire diameter. Further examination of the section of starter wire from the starter relay in the nose to the firewall revealed thermal damage to the starter relay. Several areas of the wire in the wing root area were found to have individual strands burned or partially melted and separated. The starter wire was forwarded to the NTSB Metallurgical Laboratory for further examination. During the examination of the left engine, the starter was energized using an exemplary starter wire and a test battery. The starter bendix engaged and rotated the engine crankshaft and propeller for a series of revolutions. Engine compression, oil pressure, accessory gear rotation, and left magneto impulse coupling operation were noted. The exemplary starter wire was then stripped of insulation and grounded against an engine mount. When the starter was energized, the starter bendix did not engage. The exemplary starter wire became hot and the battery terminals melted and separated from the test battery. Examination of the area where the insulation had been stripped from the wire revealed physical evidence of melting of the wire strands and molten metal. The propellers were examined on June 8, 1998, at Lancaster, Texas, under the surveillance of a NTSB investigator. The left engine propeller was in the feathered position, and the right propeller was at the start lock blade angle. According to the manufacturer representative, "there were no impact indications that would have been useful for measuring blade angles at impact." NTSB Metallurgical examination of the left engine starter wire in the wing root area revealed areas of electrical arcing damage that cut completely through some of the strands within the starter cable and fused other strands together. No evidence of electrical arcing damage was noted in the region of the resolidified drip of copper conductive material found adjacent to the melted radius curvature area of the starter cable. The New Piper Aircraft, Inc., Vero Beach, Florida, engineering department conducted a single engine performance calculation for the subject aircraft. The following criteria were used for the calculation: 180 hp engines, 90 degrees Fahrenheit, 1,700 feet msl, flaps retracted, airspeed 95 mph. 3,357 pounds aircraft loading and left engine feathered. Under these conditions, the subject aircraft would have a climb capability of + 320 feet per minute (fpm) with the landing gear retracted and -7 fpm with the landing gear extended. ADDITIONAL INFORMATION: The airplane was released to the owner's representative.
The designated pilot examiner's decision to execute a single engine go-around which exceeded the airplane's engine out climb capability in the gear down configuration. Factors were the arcing of an electrical wire that grounded the engine starter and the high density altitude.
Source: NTSB Aviation Accident Database
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