# NTSB WPR24LA205: Replica PA-12 Replica, N406Z, Douglas, WY, June 22, 2024

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Class 3 · Limited · Final report
- Date: June 22, 2024, 08:35 local (14:35 UTC)
- Place: Douglas, WY
- Coordinates: 42, -105
- Nearby events: https://openairdocs.org/map.md?lat=42.0000&lon=-105.0000&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Defining event: [Approach-VFR pattern downwind: Fuel exhaustion](https://openairdocs.org/ntsb-events/192)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Western Pacific Region
- Parties: Back Country Supercubs, Federal Aviation Adminstration, Progressive Air Services, Transport Safety Board of Canada, EFII
- NTSB case key (mKey): 194537
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR24LA205
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194537/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=194537
- Page: https://openairdocs.org/ntsb/WPR24LA205

## Probable cause

A loss of power due to fuel exhaustion as a result of the pilot’s failure to calibrate the fuel flow indicator.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=05638T0), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md)
- [Fluids: fuel](https://openairdocs.org/ntsb-findings/01071010): Aircraft › Fluids/misc hardware · Fluid management (probable cause); cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-findings/01071010/cases.md?model=05638T0), [All aircraft, 1,695 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md)
- [Fluids: fuel](https://openairdocs.org/ntsb-findings/01071010): Aircraft › Fluids/misc hardware · Fluid level (probable cause); cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-findings/01071010/cases.md?model=05638T0), [All aircraft, 1,695 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md)
- [Engine fuel and control: fuel flow indicating](https://openairdocs.org/ntsb-findings/01057331): Aircraft › Aircraft power plant · Not serviced/maintained (probable cause); cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-findings/01057331/cases.md?model=05638T0), [All aircraft, 4 cases](https://openairdocs.org/ntsb-findings/01057331/cases.md)
- [Ignition system](https://openairdocs.org/ntsb-findings/01057400): Aircraft › Aircraft power plant · Unknown/Not determined; cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-findings/01057400/cases.md?model=05638T0), [All aircraft, 18 cases](https://openairdocs.org/ntsb-findings/01057400/cases.md)
- [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=05638T0), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md)
- [Planning/preparation: fuel planning](https://openairdocs.org/ntsb-findings/02061030): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-findings/02061030/cases.md?model=05638T0), [All aircraft, 719 cases](https://openairdocs.org/ntsb-findings/02061030/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Approach: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340); cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=05638T0), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md)
- [Approach-VFR pattern downwind: Fuel exhaustion](https://openairdocs.org/ntsb-events/192) (defining event); cases with it: [Replica PA-12 REPLICA, 1 case](https://openairdocs.org/ntsb-events/192/sequence.md?model=05638T0), [All aircraft, 804 cases](https://openairdocs.org/ntsb-events/192/sequence.md)

## Analysis

The pilot was performing a Phase 1 flight test in the airplane following the installation of a new engine. The pilot reported that before departure the engine ran rough, with a loss of about 250 rpm while operating on only one of the two electronic magnetos. He dismissed the anomaly as the engine functioned normally with both electronic control unit (ECUs) on or on the other ECU. The pilot then flew for 2 hours on 40 gallons of fuel. The pilot switched tanks halfway through the flight. About 20 minutes before the accident, the pilot saw one of the multi-function displays flicker and then 20 minutes later a total loss of engine power occurred. Both ECUs indicated they were off and the pilot’s three attempts to restore power to the engine by recycling the ECUs were unsuccessful. The pilot initiated a slip maneuver to descend quickly from the base leg and rolled out into a three-point attitude over the runway. The airplane landed hard, both main landing gear axles failed, and the airplane nosed over and came to rest inverted. The vertical stabilizer and rudder were substantially damaged. The pilot noted that the axles were likely insufficient to carry the loads of the airplane during normal operations and sheared during the hard landing. Postaccident examination of the airplane and engine did not reveal any preimpact mechanical anomalies that would have precluded normal operation. The pilot reported that his multi-function display flickered and that he received indications that ECU 1 was off and ECU 2 was disconnected after the loss of power; however, all the ECU connections were secure and both ECUs functioned normally during a postaccident engine run. Performance computations showed that the airplane would have consumed about 39 gallons of the 40 gallons of fuel onboard at the beginning of the flight. Thus, it is likely that the loss of engine power was due to fuel exhaustion. The displayed fuel consumption (in gallons per hour) by the ECU was likely incorrect and may have been off by several gallons as the pilot had not calibrated the fuel flow, which was required by the ECU manufacturer after installation. The ECU operation would not have been influenced by or affected the system’s fuel management during the accident flight, as the systems were not connected.

## Factual narrative

On June 22, 2024, about 0835 mountain daylight time, an experimental amateur-built replica PA-12, N406Z, was substantially damaged when it was involved in an accident near Douglas, Wyoming. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 flight test. According to the pilot, he was beginning Phase 1 flight testing following the installation of a new engine. Before departure, the pilot completed an engine run-up, during which time he cycled the ECU switches (the airplane was equipped with two ECU switches). The engine ran smooth and continuously when ECU 1 was switched off and ran rough when ECU 2 was switched off. The pilot then switched both ECUs to the ON positions and enrichened the mixture before departure to cool the cylinders while breaking in the engine. He cycled the ECUs one more time and received the same result, but determined the airplane was safe to fly with both ECUs on. Most of the flight was uneventful. The pilot remarked that he maintained about 38% fuel trim to maintain the cylinder temperatures within a desired range. He also manually switched fuel tanks from the left tank to the right tank after 1 hour of flight time. At that time, ECU 1 indicated blue and ECU 2 indicated green (both were connected and operating: the green indication meant that ECU 2 was operating and connected to the rest of the system; the blue indications meant that ECU 1 was in control of the fuel injectors). However, at about 0815 one of the multi-function displays started to flicker. About 20 minutes later the pilot flew over his destination airstrip at an altitude about 700 ft above ground level. As he approached the airstrip, the pilot configured the airplane for landing by establishing an airspeed of 65 mph, indicated with 2 notches of flaps extended. After he decreased manifold pressure on the downwind leg for the northwest runway, the engine lost all power. When the pilot looked at the display after the power loss he noted that the ECU 1 indicator displayed red and the ECU 2 indicator displayed grey (indicating that both ECUs were off). The voltage meter showed a battery strength of about 14 volts with no low power annunciations. The pilot turned to the base leg of his approach and cycled the ECU switches; however, both ECUs repeated the same indications (ECU 1 red, ECU 2 grey). After he turned to the final approach leg he cycled the fuel pump, which operated properly according to the flight display, but observed no change when he cycled the ECUs a third time. The pilot selected a landing point on the runway and put the airplane in a slip momentarily to descend. He then rolled wings level when he was ready to make runway contact, and subsequently flared. The airplane touched down “moderately” hard with the wings level in a three-point attitude; however, both main landing gear axles failed, and the airplane nosed over, which resulted in substantial damage to the rudder and verticalstabilizer. Data retrieved from an onboard panel display showed that the airplane departed Converse County Airport, Douglas, Wyoming, at 1235:15 and flew uneventfully for about 2 hours. At 0833:14, as the airplane was starting on the downwind leg of its approach, the engine speed was 2,400 rpm with a fuel pressure of 24 psi. The engine speed and fuel pressure then started to decrease and reached 1,170 rpm with a fuel pressure of 6.2 psi as the airplane started its base turn at 0834:01. The engine power advanced slightly to about 2,000 rpm with a fuel pressure of 11.9 psi and engine power decreased to about 670 rpm with an increase in fuel pressure to about 21 psi; at the time the airplane was on final approach at 0834:27. Over the next 20 seconds (to the end of the flight), engine power decreased to about 400 rpm with short, momentary advances in power; however, fuel pressure continued to indicate about 21 psi. No data was available from the ECU. According to the pilot, he had selected and installed axles that were insufficient for the airplane. He told his mechanic to proceed with the installation and that he would “keep an eye on them,” contrary to his mechanic’s suggestion. The airplane was equipped with an Aero Sport Power IO-375-EXP air-cooled, horizontally opposed, 200 hp, reciprocating engine. The airplane also had an electronic fuel injection and ignition system manufactured by EFII. According to the company’s website, the system is a fully redundant electronic engine management system that could be used in any experimental category airplane equipped with four- or six-cylinder Lycoming engines. The website also describes the integration of the engine control unit with the engine accessories and fuel delivery system. “The system is controlled by an ECU (the computer) and incorporates a fully mapped fuel curve and ignition timing curve. The electronic fuel injection portion of the system utilizes electronic fuel injector valves that are installed into each cylinder using our Port Mount Injector (PMI) system. A throttle body replaces the typical carburetor or mechanical injector butterfly assembly. The electronic ignition portion of the system utilizes high energy inductive ignition coils instead of magnetos to deliver a very strong and efficient spark to each plug. All System32 kits are fully redundant and include two System32 ECUs and redundant engine sensors.” According to the ECU manufacturer, the fuel flow must be calibrated for accuracy, and they provide instructions to complete this task. The pilot’s mechanic reported that the pilot declined their offer to calibrate the fuel flow system before the first flight. Testing data from the engine conversion showed a fuel flow of 7.7 gph at 2,200 rpm, 10.3 gph at 2,400 rpm, and 18.2 gph at 2,700 rpm. The pilot reported that he departed with 40 gallons of fuel onboard and subsequently flew for 2 hours before he experienced a total loss of engine power. Data captured by the engine monitoringsystem showed that the pilot maintained an engine speed of 2,500 rpm for most of the flight. Performance computations showed that the engine would have maintained a fuel flow of about 14.3 gph at this engine speed without fuel trim applied and 19.6 gph with 38% fuel trim, which was the trim used as reported by the pilot. A photograph of the fuel flow during a flight the day before showed 14.4 gph fuel flow at an engine speed of 2,500 rpm. The ECU also uses a color-coded system displayed on panel in the cockpit to show the status of the ECU and its redundancy. According to the manufacturer: · Green indicates that the ECU is operating and connected to the rest of the system · Blue indicates the ECU is in control of the fuel injectors and connected to the system · Red indicates that the ignition function (P-lead switch) is in the off position, but the ECU is still connected · Grey indicates the ECU is not connected to the rest of the system, which could be due to a power loss or disconnected communications cable The ECU manufacturer also noted that only one ECU can be in control of fuel delivery and that the ECU select switch manages which ECU is in control. A blue label on the ECU monitor indicates the ECU that is actively in control of fuel delivery and a green label shows that the ECU is not actively in control. According to the ECU manufacturer, two engine run-up switches toggle each ECU between RUN and STOP mode (one switch controls ECU 1 and the other controls ECU 2). The ECU will show red if the engine is in STOP mode. The ECU manufacturer reported that the pilot would never select STOP mode in flight as these switches are designed to complete the run-up ignition test, or “mag check.” The ECU manufacturer also reported that the system comes pre-programmed, but that the fuel flow on the ECU is not considered accurate until it has been calibrated. Postaccident examination of the engine did not reveal any preimpact mechanical anomalies or malfunctions that would have precluded normal operation. All the electrical components of the EFII engine management system were secure at their appropriate terminal connections and found to be in serviceable condition. A postaccident engine run showed that with both ECUs in the ON position and the engine speed at 1,530 rpm, the ECU 1 indicator displayed blue and the ECU 2 indicator was green. When ECU 1 was switched off the indicator displayed red while ECU 2 displayed green. The engine was smooth and continuous at 1,500 rpm and when ECU 1 was switched on the engine continued to run smooth. When ECU 2 was switched off the engine speed dropped to 1,270 rpm. During this time ECU 1 indicated blue and ECU 2 indicated red on the controller panel. When ECU 2 was switched on the engine speed increased to 1,520 rpm and ran smooth. The engine was subsequently operated between 1,000 rpm (idle speed) and 1,800 rpm with no rough running indications or interruptions in power. The ECU indications did not change when thefuel was depleted and the engine ceased running. According to the ECU manufacturer, a grey annunciation with one ECU and a red annunciation with the other ECU suggests there was likely a “global fault affecting multiple systems, such as a primary ground or power connection somewhere in the plane exhibiting an intermittency (loose connection, broken wire, etc).” The ECU manufacturer also noted, “During flight operations, the ECU labels would never be RED. They would only be GREEN or BLUE. If ECU labels are something other than GREEN or BLUE, this indicates a wiring or voltage issue. The two ECUs have their own separate power and ground wiring and operate as separate systems. If both ECUs are showing status indications that are other than GREEN or BLUE, this indicates that both systems are seeing power faults of some sort.” The ECU manufacturer also offered an opinion about the change in ECU labels. He opined, “…this suggests there was an upstream cause of the power fault either on the+12v supply or on the ground supply that was affecting both ECU systems (and possibly the MFD as stated in the text). The observation of the pilot suggests that three different systems experienced some type of power or ground interruption (two ECUs and the MFD). Again, this suggests a main supply wiring issue on 12v or ground that is affecting multiple systems.”

## Aircraft

- Registration: [N406Z](https://openairdocs.org/aircraft/N406Z), registered now, S/N MB 1201, built 2009 (OpenAirDocs)
- Reported make and model: REPLICA PA-12 REPLICA
- Registry model: [Replica PA-12 REPLICA](https://openairdocs.org/model/replica-pa-12-replica) (registry code 05638T0) (OpenAirDocs)
- Registry engine: [Lycoming O-320-E2D](https://openairdocs.org/engine/lycoming-o-320-e2d) (registry code 42123, 4 cycle) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: MB 1201
- Year built: 2009
- Airframe hours: 493
- Engines: Aerosport power IO-375 EXP 200 hp reciprocating
- Damage: Substantial damage
- Flight: Flight test, Part 91
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Condition, March 20, 2023
- Departed: DGW, Douglas, WY
- Destination: Same as departure
- Airport: priv, Backcounty Supercubs, runway PRIV, 1,349 × 125 ft, grass/turf
- Equipment: Handheld GPS, Electronic primary flight display, Electronic multifunction display, ADS-B, Satellite tracking device, Onboard weather

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 48; injuries: minor; private; airplane ratings: single-engine land; medical: class 2, with waivers/limitations; last flight review October 5, 2023; seat: front; restraint: 4-point; flight hours: 307 total, 305 in this make and model, 247 as pilot in command, 4 in the last 90 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 100° at 5 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 70 °F, dew point 50 °F
- Altimeter: 30.12 inHg
- Observed at: KEAN, 4 nm away
- METAR: KEAN 221435Z AUTO 10005KT 10SM CLR 21/10 A3012 RMK AO2 T02080102

## 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 20240622008829A](https://openairdocs.org/incident/20240622008829A), Jun 22, 2024: Back Country Cub PA-12, Douglas, WY, Minor damage. Electronic magnetos lost electric power and engine quit. Pilot had to dead stick aircraft to runway. Landed hard and broke both axles off at landing gear…

## Docket (14 files)

The files NTSB released with the investigation on April 23, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=194537. 24.3 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 13 pages, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17889366&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf
- Accident photographs (item 2, PDF, 6 pages, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17903005&FileExtension=pdf&FileName=Accident%20Photographs-Rel.pdf
- Memorandum of record, ecu manufacturer (item 3, PDF, 2 pages, 69 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18026007&FileExtension=pdf&FileName=MOR%20ECU%20manufacturer-Rel.pdf
- Correspondence with ecu manufacturer (item 4, PDF, 2 pages, 135 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17897308&FileExtension=pdf&FileName=correspondence%20with%20ECU%20manufacturer_Redacted-Rel.pdf
- Correspondence with pilot's mechanic (item 5, PDF, 7 pages, 598 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17898370&FileExtension=pdf&FileName=correspondence%20with%20pilots%20mechanic_Redacted-Rel.pdf
- Initial tuning procedure - efii (item 6, PDF, 1 page, 198 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17897785&FileExtension=pdf&FileName=System%20tuning%20procedure-Rel.pdf
- Efii fuel flow and RPM configuration (item 7, PDF, 1 page, 188 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17897886&FileExtension=pdf&FileName=Fuel%20Flow%20and%20RPM%20config,%20rev%2010-19-Rel.pdf
- Engine exam/run report from aero sport power (item 8, PDF, 5 pages, 47 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17897969&FileExtension=pdf&FileName=engine%20exam%20and%20run%20aero%20sport%20power-Rel.pdf
- Aero sport power engine run data prior to installation (item 9, PDF, 1 page, 4.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17907216&FileExtension=pdf&FileName=Engine%20test%20run%20at%20aero%20sport-Rel.pdf
- Statement of party representatives to NTSB investigation (item 10, PDF, 3 pages, 3.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17897517&FileExtension=pdf&FileName=Party%20forms_Redacted-Rel.pdf
- Release of aircraft wreckage, NTSB form 6120.15 (item 11, PDF, 2 pages, 122 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17897108&FileExtension=pdf&FileName=Release%20of%20Wreckage_Redacted-Rel.pdf
- Electronic devices - specialist's factual report (item 12, PDF, 14 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18029414&FileExtension=pdf&FileName=WPR24LA205%20Electronic%20Devices%20-%20Specialist%27s%20Factual%20Report-Rel.pdf
- Attachment 1 to electronic devices - specialist's factual report (item 13, CSV, 38 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18029738&FileExtension=csv&FileName=WPR24LA205%20Attachment%201%20to%20Electronic%20Devices%20-%20Specialist%27s%20Factual%20Report-Rel.csv
- Attachment 2 to electronic devices - specialist's factual report (item 14, CSV, 7.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18029748&FileExtension=csv&FileName=WPR24LA205%20Attachment%202%20to%20Electronic%20Devices%20-%20Specialist%27s%20Factual%20Report-Rel.csv

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.

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