ASN Wikibase Occurrence # 39384
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| Date: | Monday 25 November 1985 |
| Time: | 17:42 |
| Type: |  Aero Commander 500S Shrike Commander |
| Owner/operator: | Iowa State University |
| Registration: | N81589 |
| MSN: | 3297 |
| Total airframe hrs: | 3185 hours |
| Engine model: | LYCOMING IO-540-E1B5 |
| Fatalities: | Fatalities: 7 / Occupants: 7 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Des Moines, IA -
 United States of America
|
| Phase: | Approach |
| Nature: | Passenger - Non-Scheduled/charter/Air Taxi |
| Departure airport: | Milwaukee, WI (MKE) |
| Des Moines, IA | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The Aero Commander 500S Shrike Commander (N81589), owned and operated by Iowa State University, crashed in the front yard of a Des Moines, Iowa, residence. Instrument meteorological conditions prevailed and an instrument flight plan had been filed. The commercial pilot and his six passengers received fatal injuries. The airplane was demolished by impact and postcrash fire.
The aircraft had encountered icing conditions during arrival to Des Moines and was vectored for an ILS approach to runway 12L behind a Boeing 727.
Radar data showed that the separation between the aircraft was 3.74 miles in the early stages of their approaches, but had increased to 4.7 miles by the time the Boeing 727 had passed the point where N81589 subsequently made a course deviation.
The predicted altitude drop of the Boeing 727's wingtip vortices would have been 400 to a maximum 900 feet.
After a substantial altitude deviation in the approach or landing configuration, the aircraft’s ability to climb and/or accelerate would have been seriously degraded, if structural icing and/or engine power loss occurred.
The normal approach speed (without airframe ice) is 100 KIAS or greater. Although the reason for N8i589’s altitude deviation could not be positively determined, the Safety Board believes that it was most likely due to a combination of relatively slow flight and the presence of light airframe icing, which resulted in premature aerodynamic stall. It is also possible that N81589 had descended well below the ILS glide slope and encountered wake turbulence that lasted considerably longer and remained much higher than either theory or flight tests would indicate possible. The Safety Board believes that the pilot’s reference to “severe turbulence” is consistent with an encounter with either ice-induced aerodynamic buffeting or wake turbulence. The engine may have lost power due to the unporting of fuel lines during the loss of control.
Accident investigation:
 |
|
Sources:
NTSB: http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-summaries/AAR87-03S.pdf
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Oct-2008 10:30 | ASN archive | Added |
| 21-Dec-2016 19:23 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 26-Sep-2021 09:59 | xrecovery9 | Updated [Source] |
| 26-Sep-2021 10:06 | harro | Updated [Nature, Destination airport, Narrative, Accident report] |
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