# NTSB WPR19LA259: Piper PA28, N4403Z, Marana, AZ, September 14, 2019 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: September 13, 2019, 17:30 local (Sep 14, 2019, 00:30 UTC) - Place: Marana, AZ - Coordinates: 32.403888, -111.219718 - Nearby events: https://openairdocs.org/map.md?lat=32.4039&lon=-111.2197&mi=10 - Phase of flight: [Prior to flight](https://openairdocs.org/ntsb-phases/100) (OpenAirDocs' grouping) - Defining event: [Prior to flight: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: CAE, AVStar Fuel Systems, Inc, Lycoming Engines, FAA-FSDO, Piper Aircraft, Precision Airmotive LLC - NTSB case key (mKey): 100261 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR19LA259 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/100261/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=100261 - Page: https://openairdocs.org/ntsb/WPR19LA259 ## Probable cause Excessive fuel pressure and temperature throughout the fuel system due to heat soaking, which resulted in an engine fire during engine start. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Fuel system: fuel pressure](https://openairdocs.org/ntsb-findings/01022844): Aircraft › Aircraft systems · Capability exceeded (probable cause); cases with it: [Piper PA-28-181, 1 case](https://openairdocs.org/ntsb-findings/01022844/cases.md?model=7102807), [All aircraft, 16 cases](https://openairdocs.org/ntsb-findings/01022844/cases.md) - [Fuel system: fuel distribution](https://openairdocs.org/ntsb-findings/01022820): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Piper PA-28-181, 3 cases](https://openairdocs.org/ntsb-findings/01022820/cases.md?model=7102807), [All aircraft, 141 cases](https://openairdocs.org/ntsb-findings/01022820/cases.md) - [Fuel system: fuel temperature](https://openairdocs.org/ntsb-findings/01022843): Aircraft › Aircraft systems · Capability exceeded (probable cause); cases with it: [Piper PA-28-181, 1 case](https://openairdocs.org/ntsb-findings/01022843/cases.md?model=7102807), [All aircraft, 4 cases](https://openairdocs.org/ntsb-findings/01022843/cases.md) - [Temp/humidity/pressure: high temperature](https://openairdocs.org/ntsb-findings/03031015): Environmental issues › Conditions/weather/phenomena · Effect on equipment; cases with it: [Piper PA-28-181, 1 case](https://openairdocs.org/ntsb-findings/03031015/cases.md?model=7102807), [All aircraft, 30 cases](https://openairdocs.org/ntsb-findings/03031015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) (defining event); cases with it: [Piper PA-28-181, 5 cases](https://openairdocs.org/ntsb-events/150/sequence.md?model=7102807), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md) ## Analysis During engine start about 30 minutes following the previous shutdown, the engine caught fire, which resulted in substantial damage to the airplane. The operator reported that six of their airplanes experienced flooding and subsequent fires during the engine start process within the previous 6 months. The airplanes that experienced flooding and fires had all previously flown and been parked between 5 and 28 minutes before the engines were restarted and the flooding occurred. During these events, the daily average temperatures were between 85° and 98°F. Testing conducted to simulate the conditions of the engine fire events revealed that, in the minutes following engine shutdown, the temperature of the fuel system components and fuel pressure to the carburetor would rise, most likely as a result of heat soaking from the combination of the hot engine and high outside air temperature. The tests showed that during the engine restart, about 6 to 12 ounces of fuel and vapor emanated from the carburetor intakes. During some of the tests, a whistling sound was heard originating from the carburetor inlet, which is likely from the buildup of fuel vapor as a result of the heat soaking and escaping through the internal passages of the carburetor before exiting out the carburetor intake. The carburetor from the accident airplane was disassembled, and the accelerator pump needle valve showed wear at the valve contact area. This wear was likely a result of the high fuel pressure vapor and fuel escaping past the valve, causing it to chatter excessively. The operator had experienced recent growth in its student population, which resulted in increased frequency of flights during the day. This most likely prevented the engine and fuel system from cooling between flights. ## Factual narrative On September 13, 2019, about 1730 mountain standard time, a Piper PA-28-181 airplane, N4403Z, was substantially damaged when it was involved in an accident near Marana, Arizona. The flight instructor, student pilot, and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the flight instructor, after landing at Marana Regional Airport (AVQ), Marana, Arizona, they exited the airplane, used the airport facilities, and had the airplane refueled. About 30 minutes later, the instructor completed a preflight inspection, during which he did not see any fuel or liquid leaking from the airframe or engine. They boarded the airplane and performed the engine start checklist. The instructor stated that he attempted to start the engine but was unsuccessful. During a second unsuccessful engine start attempt, the instructor and the two other occupants smelled smoke. They exited the airplane and saw smoke coming from the nosewheel well. The airplane subsequently caught fire and continued to burn for about 15 minutes before the fire department arrived. Postaccident examination of the airplane revealed fire damage to the forward fuselage and cowling. Blue staining was found at the airbox. The carburetor was disassembled, and the accelerator pump needle valve showed wear at the valve contact area. Examination of the engine and airframe revealed no evidence of preaccident mechanical malfunctions or anomalies that would have precluded normal operation. The operator reported that, within a 6-month span, six of their PA-28-181 airplanes experienced flooding and subsequent fires during the engine start process. Five of the airplanes, including the accident airplane, were manufactured in 2013 and one was manufactured in 2019. All of the airplanes that experienced the flooding and subsequent fires had been previously flown then parked for times ranging between 5 and 28 minutes before the engines were restarted. The daily average temperatures at the time of each event were between 85° and 98°F. The operator had been operating for 7 years without any engine fires occurring during the engine start process. The operator also reported that they recently had a significant increase in the student population from about 225 to an excess of 700 students, with an increased frequency of flights per day. Other flight schools in the area that operated the PA-28-181 did not report similar flooding or engine fires during engine start. Testing was performed on the operator’s fleet of PA-28-181 airplanes during hot climate conditions. Engine runs were conducted to establish oil temperatures in excess of 200° F then the engine was shut down. Following shutdown, the temperature of the fuel system components increased and fuel pressure throughout the fuel system to the carburetor rose. After a certain amount of time, the engines were restarted and about 6 to 12 ounces of fuel and vapor were observedemanating from the carburetor intakes. In some of the tests, while vapor was escaping, a whistling sound was heard originating from the carburetor inlet. 100 low lead aviation fuel begins to vaporize at approximately 106°F, and for a given volume, the higher the temperature of the fuel, the greater the ratio of vapor-to-liquid formation. A PA-28-181 manufactured in 1976, which was equipped with a Piper fuel cooling modification installed per Service Letter (SL) 427, Fuel Cooling Kits, was also tested. During the engine run, the engine oil temperature was increased to 230°F and the engine was shut down. The testing could not duplicate the increase in fuel pressure. Piper issued SL427 “Fuel cooling kits” in 1964, which specifies installation of the kit at the owner’s discretion, “in areas where high atmospheric temperatures may be encountered, and additional cooling is desirable.” This modification was discontinued for unknown reasons. None of the operator’s airplanes were equipped with the Piper fuel cooling modification. The operator reported that after installing an ignition modification that increased spark energy during engine start on all of their airplanes, no additional flooding events or engine fires occurred. ## Aircraft - Registration: [N4403Z](https://openairdocs.org/aircraft/N4403Z), registered now, S/N 2843726, built 2013 (OpenAirDocs) - Reported make and model: Piper PA28 (181) - Registry model: [Piper PA-28-181](https://openairdocs.org/model/piper-pa-28-181) (registry code 7102832) (OpenAirDocs) - Registry engine: [Lycoming O-360-A4M](https://openairdocs.org/engine/lycoming-o-360-a4m) (registry code 42276, 4 cycle) (OpenAirDocs) - Category: Airplane - Serial number: 2843726 - Year built: 2013 - Airframe hours: 6063 - Engines: Lycoming O-360-A4M 180 horsepower reciprocating - Damage: Substantial damage - Fire: On-Ground - Flight: Instructional, Part 91 - Operator: Cae Oxford Aviation Academy Phoenix Inc - Registered owner: Cae Oxford Aviation Academy Phoenix Inc - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, August 29, 2019 - Destination: FFZ, Mesa, AZ - Airport: AVQ, Marana Regional Airport - Equipment: Stall warning system, Satellite tracking device, Electronic primary flight display, Electronic multifunction display, Data recorder, ADS-B, Video recording device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 23; injuries: none; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review July 22, 2019; seat: right; restraint: 3-point; flight hours: 307 total, 28 in this make and model, 248.8 as pilot in command, 76 in the last 90 days, 37.2 in the last 30 days, 1.6 in the last 24 hours - Student pilot; age 19; injuries: none; medical: class 3, without waivers/limitations; seat: left; flight hours: 66.5 total, 67 in this make and model, 0 as pilot in command, 0 in the last 90 days, 0 in the last 30 days, 1.6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 320° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 99 °F, dew point 36 °F - Altimeter: 29.87 inHg - Observed at: KAVQ ## Docket (16 files) The files NTSB released with the investigation on May 10, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=100261. 210 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13573342&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Flight instructor-statement (item 2, PDF, 1 page, 80 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13574068&FileExtension=pdf&FileName=Instructors%20Report-Rel.pdf - NTSB engine and airframe examination summary (item 3, PDF, 8 pages, 8 photos, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13573453&FileExtension=pdf&FileName=WPR19LA259%20Engine%20and%20Airframe%20Examination%20Summary-Rel.pdf - Cae-investigative notes (item 4, PDF, 3 pages, 46 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13573114&FileExtension=pdf&FileName=CAE-Investigative%20Notes-Rel.pdf - NTSB fuel system testing-field notes (item 5, PDF, 6 pages, 1 photo, 246 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13573944&FileExtension=pdf&FileName=WPR19LA259%20Fuel%20System%20Test-Field%20Notes-Rel.pdf - Table of events (item 6, PDF, 1 page, 107 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13577601&FileExtension=pdf&FileName=Engine%20Fires%20Table-Rel.pdf - Piper service letter no 427 (item 7, PDF, 1 page, 111 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13848195&FileExtension=pdf&FileName=Piper%20Service%20Letter%20No%20427-Rel.pdf - Champion aerospace-slickstart system (item 8, PDF, 2 pages, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13578085&FileExtension=pdf&FileName=Data-Sheet-SlickStart-Mar-2017-Rel.pdf - Statement of party representatives to NTSB investigation-cae (item 9, PDF, 1 page, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13830901&FileExtension=pdf&FileName=Party%20Form-CAE_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation-lycoming (item 10, PDF, 1 page, 717 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13573931&FileExtension=pdf&FileName=Lycoming%20Party%20Form_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation-avstar (item 11, PDF, 1 page, 798 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13573744&FileExtension=pdf&FileName=Party%20Form-AVStar%20Fuel%20Systems_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation-precision (item 12, PDF, 1 page, 154 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13573352&FileExtension=pdf&FileName=Precision%20Party%20Form_Redacted-Rel.pdf - Test run video-1 (item 13, MP4, 61.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13239643&FileExtension=MP4&FileName=DSCN1746--Rel.MP4 - Test run video-2 (item 14, MP4, 84.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13239689&FileExtension=MP4&FileName=DSCN1747--Rel.MP4 - Test run video-3 (item 15, MP4, 54.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13239699&FileExtension=MP4&FileName=DSCN1749--Rel.MP4 - Photo array-accident airplane (item 16, PDF, 4 pages, 952 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13239862&FileExtension=pdf&FileName=Photo%20Array-Accident%20Airplane-Rel.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.