# NTSB ANC22LA064: 5 Rivers SQ-2, N58SQ, Soldotna, AK, July 27, 2022

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Class 3 · Limited · Final report
- Date: July 27, 2022, 09:10 local (17:10 UTC)
- Place: Soldotna, AK
- Coordinates: 60.165006, -150.3927
- Nearby events: https://openairdocs.org/map.md?lat=60.1650&lon=-150.3927&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Defining event: [Enroute-cruise: Fuel related](https://openairdocs.org/ntsb-events/190)
- Highest injury: Serious injuries
- Injuries: 1 serious, 1 uninjured
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Alaska Regional Office
- Parties: Federal Aviation Administration
- NTSB case key (mKey): 105645
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC22LA064
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/105645/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=105645
- Page: https://openairdocs.org/ntsb/ANC22LA064

## Probable cause

A total loss of engine power due to carburetor icing, which resulted from the pilot's failure to use carburetor heat while operating in conditions conducive to the formation of carburetor ice.

## Findings

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

- [Temp/humidity/pressure: conducive to carburetor icing](https://openairdocs.org/ntsb-findings/03031030): Environmental issues › Conditions/weather/phenomena · Effect on equipment (probable cause); cases with it: [5 Rivers SQ-2, 1 case](https://openairdocs.org/ntsb-findings/03031030/cases.md?model=05628YV), [All aircraft, 435 cases](https://openairdocs.org/ntsb-findings/03031030/cases.md)
- [Ice/rain protection system: intake anti-ice, deice](https://openairdocs.org/ntsb-findings/01023020): Aircraft › Aircraft systems · Not used/operated (probable cause); cases with it: [5 Rivers SQ-2, 1 case](https://openairdocs.org/ntsb-findings/01023020/cases.md?model=05628YV), [All aircraft, 108 cases](https://openairdocs.org/ntsb-findings/01023020/cases.md)
- [Action: lack of action](https://openairdocs.org/ntsb-findings/02041030): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [5 Rivers SQ-2, 1 case](https://openairdocs.org/ntsb-findings/02041030/cases.md?model=05628YV), [All aircraft, 792 cases](https://openairdocs.org/ntsb-findings/02041030/cases.md)
- [Info processing/decision: identification/recognition](https://openairdocs.org/ntsb-findings/02041510): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [5 Rivers SQ-2, 1 case](https://openairdocs.org/ntsb-findings/02041510/cases.md?model=05628YV), [All aircraft, 559 cases](https://openairdocs.org/ntsb-findings/02041510/cases.md)

## Sequence of events

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

- [Enroute-cruise: Fuel related](https://openairdocs.org/ntsb-events/190) (defining event); cases with it: [5 Rivers SQ-2, 1 case](https://openairdocs.org/ntsb-events/190/sequence.md?model=05628YV), [All aircraft, 361 cases](https://openairdocs.org/ntsb-events/190/sequence.md)

## Analysis

The pilot reported that, while in cruise flight at about 4,000 ft mean sea level (msl), he advanced the throttle to initiate a climb, but the engine began to lose power. In an effort to regain power, he further advanced the throttle and propeller levers and switched the fuel selector to the left tank to no avail. He subsequently made a forced landing in a small gully, which resulted in substantial damage to the wings and fuselage. When the pilot was asked if he applied carburetor heat after the loss of power, he stated that he did not, as there was no visible moisture in the area, and he thought carburetor ice would be unlikely. A postaccident examination revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. According to a carburetor icing probability chart, the ambient conditions present at the time of the accident were conducive to the development of serious icing at cruise power. It is likely that the loss of engine power was the result of the formation of carburetor icing, and had the pilot applied carburetor heat, engine power would likely have been restored.

## Factual narrative

On July 27, 2022, about 0910 Alaska daylight time, a 5 Rivers LLC SQ2 airplane, N58SQ, was substantially damaged when it was involved in an accident near Soldotna, Alaska. The private pilot sustained serious injuries, and the passenger was uninjured. The airplane was operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, while in cruise flight at about 4,000 ft msl, he advanced the throttle to initiate a climb, but the engine began to lose power. In an effort to regain power, he further advanced the throttle and propeller levers and switched the fuel selector to the left tank to no avail. He subsequently made a forced landing in a small gully, which resulted in substantial damage to the wings and fuselage. A postaccident examination revealed no preaccident mechanical malfunctions or anomalies with the airplane that would have precluded normal operation. A Global Data Assimilation System (GDAS) model sounding was created for the accident time and location, with the modeled surface elevation about 2,415 ft msl. When the GDAS sounding data was interpolated for an elevation of 4,000 ft msl, the data indicated the temperature was about 4.9°C (40.8°F) and the dewpoint was about 1.6°C (34.9°F), with a relative humidity of about 79 percent. Based on the carburetor icing probability chart, these conditions would result in “serious icing – cruise power.” When the pilot was asked if he applied carburetor heat after the loss of power, he stated that he did not, as there was no visible moisture in the area, and he thought carburetor ice would be unlikely. Figure 1. Carburetor icing probability chart (Courtesy of FAA). The conditions present at the time of the power loss are indicated with a red circle. A Lycoming Service Instruction states in part: "Flight Operation – During normal flight, leave the carburetor air heat control in the full cold position. On damp, cloudy, foggy or hazy days, regardless of the outside air temperature, be alert for loss of power. This will be evidenced by an unaccountable loss in manifold pressure or RPM or both, depending on whether a constant speed or fixed pitch propeller is installed on the aircraft. If this happens, apply full carburetor air heat, and open the throttle to limiting manifold pressure and RPM.”

## Aircraft

- Registration: [N58SQ](https://openairdocs.org/aircraft/N58SQ), registered now, S/N 2009 (OpenAirDocs)
- Reported make and model: 5 RIVERS LLC SQ-2
- Registry model: [5 Rivers SQ-2](https://openairdocs.org/model/5-rivers-sq-2) (registry code 05628YV) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 2009
- Year built: 2010
- Airframe hours: 1335.1
- Engines: Lycoming O-375-C2A 205 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Condition, June 30, 2022
- Destination: Same as departure

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 66; injuries: serious; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review May 6, 2022; seat: front; restraint: 4-point; flight hours: 2,584 total, 1,195 in this make and model, 2,414 as pilot in command, 33 in the last 90 days, 6 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 10 statute miles
- Temperature: 52 °F, dew point 48 °F
- Altimeter: 30.20 inHg
- Observed at: PASX, 1 nm away
- METAR: PASX 271717Z AUTO 00000KT 10SM SCT008 11/09 A3020 RMK AO2

## 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 20220727013219A](https://openairdocs.org/incident/20220727013219A), Jul 27, 2022: 5 Rivers LLC SQ-2, Soldotna, AK, Substantial damage. On 27 July 2022 at approx 0920 local, an experimental ambuilt kit model SQ-2 was in a climbing left turn east of tustumena lake at about 4000' MSL based on…

## Docket (4 files)

The files NTSB released with the investigation on October 19, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=105645. 11.2 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 7.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14482221&FileExtension=pdf&FileName=6120%20dms_Redacted-Rel.pdf
- Global data assimilation system (gdas) data (item 2, PDF, 1 page, 58 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14481595&FileExtension=pdf&FileName=1800utcGDASsoundingtext_Redacted-Rel.pdf
- Wreckage examination summary (item 3, PDF, 2 pages, 164 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14483002&FileExtension=pdf&FileName=FAA%20Wreckage%20Examination%20Notes-Rel.pdf
- Photos (item 4, PDF, 2 pages, 3.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14583188&FileExtension=pdf&FileName=Photo%20Array-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.

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