ASN Wikibase Occurrence # 243869
This information is added by users of ASN. Neither ASN nor the Flight Safety Foundation are responsible for the completeness or correctness of this information.
If you feel this information is incomplete or incorrect, you can submit corrected information.
| Date: | Thursday 22 December 1988 |
| Time: | 16:29 |
| Type: |  ATR 42-312 |
| Owner/operator: | Simmons Airlines |
| Registration: | N427MQ |
| MSN: | 091 |
| Year of manufacture: | 1988 |
| Total airframe hrs: | 1819 hours |
| Engine model: | P&W PW-120 |
| Fatalities: | Fatalities: 0 / Occupants: 37 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | near Mosinee, WI -
 United States of America
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | |
| Mosinee, WI | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
During approach, in level flight at 6000ft, when flying in conditions later on clearly established as freezing rain, not using the airframe de-icing system, during a right bank turn with 0°flap and autopilot engaged at 157 kt (engine torque 22-23%) and at an AOA of 10.2°, the aircraft progressively rolled out to a 0° bank angle, while aileron and rudder positions were maintained.
When the AOA reached 11.5°, the autopilot disengaged, the ailerons immediately deflected to about 12,5° and the aircraft rolled to the left to an 80° maximum bank angle. The maximum aileron deflection was recorded at 12.5°.
Recovery was achieved by a prompt reaction of the crew, which applied maximum power and brought the wings back to a level position by quickly positioning the ailerons opposite to the initial roll upset. The loss of altitude was 600 feet.
On April 7, 1989, the FAA issued AD 89-09-05, which prohibited the use of the autopilot in icing conditions. The FAA determined during its investigation that the autopilot masked an asymmetric ice buildup, and the airplane rolled when the autopilot disconnected. This AD was later superseded by a new AD which removed the autopilot restriction following the installation of vortex generators to improve roll control of the airplane.
NTSB Probable Cause: "Stall induced by the accretion of moderate to severe clear icing."
Accident investigation:
 |
|
Sources:
NTSB CHI89IA034
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 15-Oct-2020 10:26 | harro | Added |
Corrections or additions? ... Edit this accident description
The Aviation Safety Network is an exclusive service provided by:
Quick Links:
| ASN Home | Send Correction / Feedback |
| FSF Home | Disclaimer | Copyright |
| Contact Us | Privacy Policy |
| Press / Media |
CONNECT WITH US:
©2024 Flight Safety Foundation