Page:CAB Accident Report, 1963 Purdue Aeronautics Corporation crash.pdf/7

 and used the VOR approach plate to check the minimums he would have advised the crew that the weather was not suitable for a VOR approach.

The captain's attempt to use a radial from the Grantsville VOR to establish the location of "Deck" shows a lack of understanding, on his part, of the display of navigational information on the approach plate he was using, as well as the inherent limitations on the use of a VOR station. He took no cognizance of the effect of distance and terrain on the emissions of very high frequency radio transmitters which broadcast essentially on a line of sight basis. His inability to differentiate between instrument centering brought about by weak signals, as opposed to a course interception, coupled with an inaccurate estimate of his ground speed to give him an erroneous position indication.

The apparent passing of the Deck fix was compounded by the captain's lack of knowledge regarding the head wind in the approach area. At the time he believed he was at the Deck fix, 3.5 nautical miles from the VOR, he had actually traveled only 2.5 nautical miles. He stated that he had begun his timing after passing the cone of ambiguity over the VOR.

The aircraft wreckage was found to have crashed on the 340° radial of the VOR rather than the 337° radial which would put it about 1/2 nautical mile right of the centerline of the approach radial. Had the aircraft been on track it would have cleared all terrain between the VOR and the airfield. Furthermore, had the minimum altitude for the approach been established as it is now the aircraft would have cleared the terrain en route to the airport, even though it was not exactly on track.

The Board determines that the probable cause of this accident was the pilot's execution of an instrument approach in an aircraft not equipped with navigational instrumentation appropriate to the ground facilities being used.

BY THE CIVIL AERONAUTICS BOARD: