# NTSB CEN16LA102: Piper PA31, N997DN, Denton, TX, January 22, 2016 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: January 22, 2016, 15:30 local (21:30 UTC) - Place: Denton, TX - Coordinates: 33.222778, -97.346946 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.2228&lon=-97.3469&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Fuel exhaustion](https://openairdocs.org/ntsb-events/192) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report February 13, 2017 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Piper Aircraft, FAA - NTSB case key (mKey): 92703 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN16LA102 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/92703/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=92703 - Page: https://openairdocs.org/ntsb/CEN16LA102 ## Probable cause The total loss of engine power due to fuel exhaustion for reasons that could not be determined because postaccident examination of the airframe and engine did not reveal any anomalies that would have precluded normal operation. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Fluids: fuel](https://openairdocs.org/ntsb-findings/01071010): Aircraft › Fluids/misc hardware · Fluid level (probable cause); cases with it: [Piper PA-31P, 2 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md?model=7103120), [All aircraft, 1,695 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md) - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Piper PA-31P, 3 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=7103120), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Fuel exhaustion](https://openairdocs.org/ntsb-events/192) (defining event); cases with it: [Piper PA-31P, 1 case](https://openairdocs.org/ntsb-events/192/sequence.md?model=7103120), [All aircraft, 804 cases](https://openairdocs.org/ntsb-events/192/sequence.md) - [Landing-landing roll: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Piper PA-31P, 4 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=7103120), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The commercial pilot reported that, during the postmaintenance test flight, the right engine surged and then behaved consistent with a fuel flow issue. The right engine subsequently lost power, and the pilot prepared to return to the airport. However, before the pilot could secure the right engine, the left engine started to surge and then lost power. The pilot conducted a forced landing to a field, during which both wings and the engine nacelles sustained substantial damage. Although a fuel smell was present on scene, there was no visual evidence of fuel in the fuel tanks or in the field. Only a quart of fuel was recovered from the left fuel tank. Further examination of the airframe and fuel system revealed that the fuel tanks were not compromised, and no mechanical anomalies with the airframe, engine, or the fuel system were found that would have precluded normal operation. The pilot reported that there should have been about 120 gallons of fuel on board at the time of departure. Additionally, a fuel receipt confirmed that 99.36 gallons of fuel had been added to the fuel tanks before a 36-minute maintenance engine test run conducted 3 days before the accident flight. No other flights were conducted between the test run and the accident flight, which the engine data monitor indicated was about 30 minutes long. Based upon calibrations set by the operator, the engine data showed that the engines consumed about 5.6 gallons of fuel during the test run and 19.2 gallons of fuel during the accident flight. Performance information from the manufacturer indicated that the engines should have burned between 10 and 18 gallons of fuel during the test run and between 27 and 50 gallons of fuel during the accident flight. Although it is possible the discrepancy between the recorded fuel consumption and the fuel consumption calculations was due to the operator setting the engine data monitor's calibrations incorrectly, it could not be determined when or by whom the calibrations were set. The absence of fuel on-scene and the loss of engine power are consistent with fuel exhaustion; however, the investigation was unable to determine why there was no fuel on board at the time of the accident. ## Factual narrative On January 22, 2016, about 1530 central standard time, a Piper PA-31 airplane, N997DN, was substantially damaged during a forced landing near Denton, Texas. The commercial rated pilot received minor injuries. The personal flight was being conducted under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. Visual meteorological conditions prevailed at the time of the accident. The local flight departed Denton Enterprise Airport (KDTO), Denton, Texas, about 1500. According to the pilot, the accident flight was a routine maintenance flight following maintenance and a 2-year period where the airplane had not flown regularly. Several days prior to the accident flight, the pilot conducted an extensive preflight of the airplane and supervised the fueling of the airplane. He stated that the inboard tanks were filled to 56 gallons and the outboard tanks had 10 gallons of fuel added . The nacelle tanks were empty. Before conducting a flight in the airplane, the pilot performed a maintenance test run of the engines. He stated that he started and shut down the engines on the inboard tanks and conducted the taxi and engine run-ups on the outboard tanks. He estimated that he ran the engines for about 30 minutes. Aside from issues with the fuel boost pumps and the left and right fuel flow indicators, he noted no anomalies with the airframe, engines, or related systems during the taxi and engine run-up. The airplane sat for three days between the maintenance test run and the accident flight. During the preflight inspection he noted a fuel spot on the floor under the right main fuel tank sump. Further examination revealed that the plug was not seated correctly. He estimated that less than a cup of fuel was lost during that time. For the accident flight the pilot estimated the fuel on board at takeoff was 120 gallons – no additional fuel was added prior to the flight, nor did he visually verify the fuel quantity as no one had flown the airplane or ran the engines since his last engine run three days prior. The run-up of both engines prior to the flight revealed no anomalies. The pilot departed with the fuel selected to the inboard tanks and then once at altitude switched to the outboard tanks. The fuel flow meters were now working and when he noted the right engine flow start to drop he switched back to the inboard tanks. He climbed to 1,000 feet, checked multiple systems and then conducted a low approach to Bishop Field. He climbed back up to 2,000 feet and was conducting the cruise checklist when the right engine surged. The pilot noted the sound and behavior consistent with no fuel/fuel flow. The pilot checked the fuel selector valves and trouble shot the engine surge without resolve. The pilot obtained clearance to enter a downwind for runway 36 at DTO at which time the right engine lost power. Before the pilot could declare an emergency and secure the right engine the left engine surged and lost power. During the forced landing tothe field both wings and engine nacelles were substantially damaged. According to the Federal Aviation Administration (FAA) inspectors who responded to the scene, they could smell fuel on scene but found no evidence of fuel. There was no fuel in the fuel tanks and there was no pooling of fuel outside of the airplane in the debris field or where the airplane came to rest. Only a quart of fuel was recovered from the left fuel tank by the airplane recovery team. An examination of the airframe, wings, and fuel system was conducted under the auspices of the National Transportation Safety Board investigator-in-charge, inspectors from the FAA, and an investigator from Piper Aircraft. The examination revealed that the fuel tanks and fuel system had not been compromised during the accident. No mechanical anomalies were noted with the engine, airframe, or airframe fuel system that would have precluded normal operation. The airplane was equipped with a J.P. Instruments EDM-790 that had the capability to monitor and record exhaust gas temperature, cylinder head temperature, oil pressure and temperature, manifold pressure, outside air temperature, turbine inlet temperature, engine rpm, compressor discharge temperature, fuel flow, and battery voltage. The unit contained non-volatile memory for data storage of the recorded parameters. The recorder was in good condition and data were extracted normally. The EDM contained 2.7 hours of data and 15 power cycles. Both the engine run and the accident flight were captured on the EDM. The engine run captured 36 minutes of engine data. The accident flight captured 30 minutes of data. Based upon the calibrations set by the operator, in the EDM, total fuel consumption for the engine run was 5.6 gallons and total fuel consumption for the accident flight was 19.2 gallons. Performance data from the airplane flight manual indicate that fuel consumption (at high cruise) to be 54 gallons per hour (gph) for both engines, and 28 gph at maximum endurance. Using data from the pilot's operating manual and airplane flight manual, investigators estimated the fuel burn for the maintenance test run, 3 days prior to the accident flight, to be between 10 and 18 gallons. Further, investigators estimated fuel burn for the accident flight to be between 27 and 50 gallons. Fuel receipts confirmed the addition of 99.36 gallons of fuel, prior to the engine maintenance test run, on January 18, 2016. ## Aircraft - Registration: [N997DN](https://openairdocs.org/deregistered/N997DN-2018-06-04), registration cancelled 2018-06-04, S/N 31P-7300113, built 1972 (OpenAirDocs) - Reported make and model: PIPER PA31 - Registry model: [Piper PA-31P](https://openairdocs.org/model/piper-pa-31p) (registry code 7103120) (OpenAirDocs) - Registry engine: [Lycoming TIGO-541SER](https://openairdocs.org/engine/lycoming-tigo-541ser) (registry code 41539, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 113 - Year built: 1972 - Airframe hours: 4438 - Engines: Lycoming TIGO 541-E1A 425 horsepower reciprocating; Lycoming TIGO 541 425 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, December 8, 2015 - Departed: DTO, Denton, TX - Destination: DTO, Denton, TX - Airport: DTO, Denton Municipal - Equipment: Onboard weather, Auto-pilot ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 69; injuries: minor; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review August 24, 2015; seat: left; restraint: lap only; flight hours: 13,300 total, 180 in this make and model, 13,063 as pilot in command, 136 in the last 90 days, 31 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 340° at 14 knots, gusting 19 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 46 °F, dew point 27 °F - Altimeter: 30.29 inHg - Observed at: DTO, 9 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20160122006369A](https://openairdocs.org/incident/20160122006369A), Jan 22, 2016: Piper PA-31P, Denton, TX, Substantial damage. The VFR maintenance test flight was the first flight after an annual inspection, prior to the inspection the aircraft was purchased from Canada. The airman… ## Docket (8 files) The files NTSB released with the investigation on November 23, 2016, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=92703. 1.4 MB in all. - Engine Data Monitor - Factual Report (item 1, .PDF, 454 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40446695&FileExtension=.PDF&FileName=Engine%20Data%20Monitor%20-%20Factual%20Report-Master.PDF - Pilot Statement (item 2, .PDF, 39 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40446696&FileExtension=.PDF&FileName=Pilot%20Statement-Master.PDF - Engine Data Monitor - Attachment 1 to Factual Report (item 3, .CSV, 66 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40446697&FileExtension=.csv&FileName=Engine%20Data%20Monitor%20-%20Attachment%201%20to%20Factual%20Report-Master.csv - Engine Data Monitor - Attachment 2 to Factual Report (item 4, .CSV, 57 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40446698&FileExtension=.csv&FileName=Engine%20Data%20Monitor%20-%20Attachment%202%20to%20Factual%20Report-Master.csv - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 5, .PDF, 596 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40459003&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Performance Chart Excerpts (item 6, .PDF, 84 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40446701&FileExtension=.PDF&FileName=Performance%20Chart%20Excerpts-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 7, .PDF, 81 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40446707&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 8, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40446708&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Master.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.