NTSB Identification: CHI91FA254.
The docket is stored on NTSB microfiche number 45238.
Accident occurred Tuesday, August 06, 1991 in OTTUMWA, IA
Probable Cause Approval Date: 01/27/1993
Aircraft: CESSNA 172M, registration: N61568
Injuries: 2 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

DURING ARRIVAL, THE PILOT WAS CLEARED FOR AN ILS RUNWAY 31 APPROACH. AS HE CONTINUED THE APPROACH, THE AIRPLANE DESCENDED INTO TREES AND THE TERRAIN, INSIDE THE OUTER MARKER, 4.0 MILES FROM THE THRESHOLD AND .19 MILE TO THE LEFT OF CENTERLINE. INITIAL IMPACT WAS ON A HEADING OF 356 DEGREES MAGNETIC AT AN ELEVATION OF 820 FEET MSL. THE AIRPORT ELEVATION WAS 845 FEET MSL. MINIMUM DESCENT ALTITUDE (MDA) BEFORE REACHING THE ILS GLIDE SLOPE WAS 2800 FEET; MDA FOR A LOCALIZER ONLY APPROACH WAS 1200 FEET. DECISION HEIGHT (IF ESTABLISHED ON THE ILS LOCALIZER & GLIDEPATH) WAS 1041 FEET. SUBSEQUENT INVESTIGATION FAILED TO REVEAL ANY MECHANICAL MALFUNCTION OF THE AIRCRAFT OR SIGNIFICANT WEATHER PHENOMENA WHICH WOULD HAVE RESULTED IN THE ACCIDENT.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

IMPROPER IFR PROCEDURE BY THE PILOT BY NOT MAINTAINING THE PROPER MINIMUM DESCENT ALTITUDE (MDA) UNTIL ESTABLISHED ON THE ILS LOCALIZER AND GLIDEPATH.

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