Flight Details
Flight 560 was a scheduled Braniff Airways daily flight operating between Dallas, Texas, and Chicago, Illinois, with intermediate stops at Oklahoma City, Oklahoma; Wichita, Kansas; and Kansas City, Missouri. On July 17, the flight crew, assigned at Dallas for the entire trip, consisted of Captain Allen R. Tobin, First Officer Orbin W. Hanks, and Hostess Mary E. Teel.
Preflight and Departure
Captain Tobin and First Officer Hanks arrived at the airport more than an hour before scheduled departure. Preflight preparations were made in a normal and routine manner. The pilots received the latest weather forecasts and reports. No significant weather conditions were noted except fog forecast for the Chicago area, with visibility expected to be restricted to possibly one-half mile on arrival. Flight 560 departed Dallas on schedule at 0100.
Intermediate Stops
The flight segments between Dallas and Wichita were uneventful. While starting the No. 1 (left) engine at Wichita prior to departure, a small carburetor intake manifold fire occurred, which was immediately extinguished. No damage was incurred, and the engine started easily on the second attempt. The flight proceeded to Kansas City, landing at 0416. As the aircraft taxied to the terminal, several persons noted that the No. 1 propeller was feathered and stopped. Captain Tobin explained that the propeller feathered while being returned to positive pitch after reverse thrust had been used during the landing roll. The captain unfeathered the propeller before deplaning, and maintenance personnel checked for malfunction; none was indicated. No other mechanical service was requested or performed. The aircraft was serviced to 1,000 gallons of fuel while the pilots received supplemental weather information and completed other preparations for the final segment.
Final Segment and Approach
Flight 560 departed Kansas City at 0435 under a VFR flight plan. Company records indicated a gross weight of 45,622 pounds, less than the maximum allowable of 47,000 pounds, with load properly distributed for center-of-gravity limits. The flight climbed to 15,000 feet MSL. At 0519, it requested and received an IFR flight plan for the remainder of the trip. En route reports were routine. This segment was described as very pleasant and smooth, conducted primarily above or clear of clouds. At 0547, ARTC cleared the flight to the Naperville Omni via Peoria, Victor 116 over Joliet, maintaining at least 1,000 on top (tops reported 2,000 MSL), contact Chicago Center on 118.9 mc passing Peoria. At 0556, Chicago ARTC broadcast a special weather observation: thin obscuration, visibility one-half mile. At approximately 0609, the flight was asked if it could land with one-half mile visibility and 1,000 feet thin obscuration; the flight replied affirmatively. At 0611, the flight reported over Joliet, 1,000 on top, and was advised to contact Chicago Midway Approach Control. The crew reported over Naperville at 0618 and was radar vectored to the outer marker for an ILS approach to runway 13R.
Accident Sequence
At 0624, the aircraft struck an advertising sign and its supporting steel post, located approximately 1,000 feet short of the runway threshold, and crashed through the airport boundary fence onto the airport. Another flight holding off the runway before takeoff observed the wreckage stop and immediately notified the tower; crash emergency procedures were promptly initiated. Weather conditions at the time were: partial obscuration, visibility one-half mile, fog and smoke, sea level pressure 1014.2, temperature 71°F, dewpoint 68°F, wind south 6 knots, altimeter 29.94 inches, with fog 8.
Investigation Findings
Examination of the aircraft wreckage and components revealed no evidence indicating malfunction or failure, and no evidence of an emergency aboard the flight. The reported weather conditions permitted the flight to land and were accurately reported from the observer's position. Navigational aids, ILS components, and ground lighting facilities were functioning normally. An ILS approach was executed precisely and accurately until approximately one-half mile from touchdown. Radar advisories were furnished in a normal manner supplementing the ILS approach. After approximately one-half mile from touchdown, the aircraft descended at a high rate. Fog with near-zero flight visibility enveloped the crash site over an indeterminable area.
Probable Cause
The Board determined that the probable cause of this accident was momentary disorientation caused by the loss of visual reference during the final visual phase of the approach, resulting in an increased rate of descent at an altitude too low to effect recovery.