# NTSB CHI89IA034: Aerospatiale ATR-42, N427MQ, Mosinee, WI, December 22, 1988

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: December 22, 1988, 16:29 local (22:29 UTC)
- Place: Mosinee, WI
- Coordinates: 44.779087, -89.679801 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.7791&lon=-89.6798&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 37 uninjured
- Status: Completed, report June 25, 1990
- Report: Approved by Office Director
- NTSB case key (mKey): 14280
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI89IA034
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14280/pdf
- Page: https://openairdocs.org/ntsb/CHI89IA034

## Probable cause

STALL INDUCED BY THE ACCRETION OF MODERATE TO SEVERE CLEAR ICING.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- In flight encounter with weather, missed approach (ifr)
  - weather condition - icing conditions (contributing factor)
  - hazardous weather advisory - not issued, nws personnel (contributing factor)
  - light condition - dark night (contributing factor)
  - weather evaluation - inaccurate, dual student (contributing factor)
  - anti-ice/deice system - not used, pilot in command (cause)
- Loss of control - in flight, approach - iaf to faf/outer marker (ifr)
  - wing - ice (cause)
  - stall - encountered, pilot in command (cause)

## Analysis

A MISSED APPROACH WAS EXECUTED ON THE FIRST APPROACH, AND THE CREW ELECTED TO FLY THE COMPLETE PROCEDURE TURN FOR THE ILS AT THE CENTRAL WISCONSIN AIRPORT. BOTH THE FIRST AND SECOND APPROACHS WERE FLOWN AT 3000 FEET MSL IN IMC CONDITIONS WITH MODERATE TO HEAVY RAIN. A TEMPERATURE INVERSION EXISTED FROM 5000 FEET TO 3000 FEET MSL WHICH CREATED CONDITIONS CONDUCIVE TO MODERATE TO SEVERE CLEAR ICING. THE AIRCRAFT WAS IN THESE CONDITIONS FOR 11.8 MINUTES. APPROXIMATELY ONE-HALF WAY THROUGH THE PROCEDURE TURN, WHICH WAS FLOWN WITH THE AUTOPILOT ON, THE CAPTAIN REDUCED POWER TO SLOW FOR GEAR EXTENSION. AT 157 KNOTS CLEAN CONFIGURATION THE AIRCRAFT STALLED AND ROLLED 80 DEGREES TO THE LEFT AND 60 DEGREES TO THE RIGHT. THE CREW APPLIED FULL POWER AND EXECUTED STALL RECOVERY PROCEDURES. THE AIRCRAFT WAS RECOVERED WITH AN ALTITUDE LOSS OF 600 FEET. THE CREW DID NOT PERCEIVE ANY ICE ACCRETION, AND THE AIRFRAME DEICE WAS NOT ON UNTIL AFTER THE STALL. THE THIRD APPROACH WAS UNEVENTFUL.

## Aircraft

- Registration: [N427MQ](https://openairdocs.org/deregistered/N427MQ-1998-05-12), registration cancelled 1998-05-12, S/N 091 (OpenAirDocs)
- Reported make and model: AEROSPATIALE ATR-42 (ATR 42)
- Registry model: [Aerospatiale/Aeritalia ATR 42-300](https://openairdocs.org/model/aerospatiale-aeritalia-atr-42-300) (registry code 8680920) (OpenAirDocs)
- Category: Airplane
- Serial number: 0091
- Airframe hours: 1819
- Engines: P&W PW-120 1800 horsepower turbo prop
- Damage: No damage
- Flight: Part 121
- Operator: Simmons Airlines, doing business as American Eagle
- Registered owner: Simmons Airlines, Inc
- Airworthiness certificate: Standard, Transport
- Departed: ORD, CHICAGO, IL
- Flight plan: IFR
- Airport: CWA, Central Wisconsin, runway 8, 7,645 × 150 ft, concrete

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 8,614 total, 565 in this make and model, 113 in the last 90 days, 42 in the last 30 days, 5 in the last 24 hours

## Weather

- Conditions: Instrument (IMC), Night/dark
- Wind: 130° at 15 knots, gusting 20
- Visibility: 1 statute miles
- Lowest ceiling: 4,000 ft overcast
- Temperature: 30 °F
- Altimeter: 29.00 inHg
- Observed at: CWA, 10 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).

- [Incident 19881222071639I](https://openairdocs.org/incident/19881222071639I), Dec 22, 1988: Aerosp ATR42300, Mosinee, WI. Light to heavy freezing rain in area. Aircraft stalled but recovered on initial approach. Airframe deice not on.

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.