Page:CAB Accident Report, Piedmont Airlines Flight 349.pdf/9

 situation, it is doubtful that any analysis can determine the sequence of events with complete definitiveness. Nevertheless, the Board believes it reached a determination which best satisfies the aforestated requisites and the known factors.

It is the opinion of the Board that the laterally erroneous flightpath developed from an initial navigational error at the Casanova omni. It is believed it occurred as an omission in that the flight did not turn in conformity with the V—l4O airway from the inbound radial of 260 degrees to the outbound radial of 239 degrees, a left turn of about 20 degrees. It is believed that the ﬂight continued on the 260-degree radial until it reached the 335-degree radial of the Gordonsville mum at a location approximately 13 miles northwest of the Rochelle intersection. It is the Board's opinion that at this location, which was believed by the pilots to be Rochelle, the flight turned left to and flew the approximate heading indicated by the flight plan and log to be flown from Rochelle, 200 degrees.

The Board has reached its opinion as to the sequence of events based upon several factors. The first was the results of an analytical time, distance, and groundspeed plot. It is probable that the flight flew about 15 minutes after reporting Rochelle until it crashed. This time, being considerably longer than the time normally required to fly from Rochelle to the inbound heading of the procedure turn, Shows a greater distance must have been flown. A plot of the probable flightpath in reverse was therefore prepared using the time flown, a reciprocal of the soundpath, and the estimated groundspeed of the DC-3. This showed that 15 minutes before the accident the aircraft would have been over an area about 13 miles northwest of Rochelle intersection.

The second phase of this work was a radius of action plot from the Casanova omni. Based on the elapsed time between the Casanova and Rochelle reports, 15 minutes, it was determined that the flight would have flown 33 miles. A line of position with a radius of 33 miles from Casanova was found to intersect the initial plot at a location which was approximately 15 minutes from the crash or again about 13 miles northwest of Rochelle.

At the completion of this work two additional Significant factors were apparent. The point of intersection of the plots was closely coincident with the 335—degree radial of Gordonsville. Secondly, the heading to the location of intersecting plots from Casanova was the Zoo—degree radial of Casanova and the same as the inbound radial to Casanova from Springfield.

At Casanova Copilot Haley made the position report and most probably recorded it in the flight plan and log. Thereafter he would be expected to tune his omni set to the Gordonsville frequency and select the 335-degree radial in order to identify the Rochelle intersection. Considering the small amount of turn required at this time, the first actions could nave diverted his attention for the period during which the captain would normally have made the turn. Tuning his omni to Gordonsville, though necessary, would also reduce his opportunity to observe by omni indications the relative position of the aircraft to the course of the airway. Additionally, there was indication that Captain Lavrinc flew with a lower than average level of instrument panel illumination. In the Board‘s opinion these factors are valid reasons in this instance for the copilot not having detected the navigational omission.