- 7 -
It has been the company practice to use the 344-degree radial of the Tri-City VOR which crosses the localizer about 6-1/2 miles east of the outer marker as an additional safety measure to assist the pilot in remaining within a safe area.
The company witness further said that the ADF is not an essential piece of radio equipment for the ILS procedure. However, he said a properly operating ADF is required by Civil Air Regulations and company regulations for flight in instrument weather conditions. In such conditions the company considers it a "no go" item. He said also that when malfunction occurs to this unit or other such item, company policy requires that it be noted in the aircraft log and corrective action be taken before originating a flight segment. As stated before, Captain Bond made no entry in the flight log concerning the ADF although he was certain that it was not operating. Records indicate that no maintenance was performed on the receiver during the stops at Nashville or Knoxville.
During the investigation many persons were interviewed in an attempt to locate witnesses to the flight of the aircraft. Many saw aircraft during the evening; however, none was able to establish the time of his observation with sufficient accuracy to be of great value to the Board in plotting a probable path for Flight 308.
A meteorologist, who was on duty at the Tri-City Airport testified concerning the weather conditions which existed at the time of the accident. He said that the ceiling was 1,700 feet overcast with scattered clouds at 1,000 feet. The visibility was 5 miles. The witness said a study of the information available to him indicated that from Bulls Gap to Tri-City at 5,000 feet the flight would have been operated in instrument weather conditions. He estimated the en route winds would have been north-northwest at approximately 20 knots. The Piedmont captain of Flight 383 estimated winds which he encountered at 5,000 feet were from the west-northwest at 25-30 knots.
Analysis
Examination of the wreckage of N 18941 revealed no evidence of any failure or malfunction of either the airframe or the powerplants. There was no indication of fire in flight and all components of the airframe were accounted for in the wreckage. Both engines and propellers were capable of normal operation prior to impact. From this evidence it is clear that no structural or mechanical failure or malfunction occurred which in any way contributed to the cause of this accident.
Examination of the radio equipment of N 18941 indicated that the crew was not utilizing all the facilities available to them. First, the No. 2 navigation receiver was not tuned to a frequency of any facility in the area. It is therefore presumed that the No. 2 navigation receiver was not in use. Normally this receiver would be tuned to the TRI VOR (117.7 mcs.) and utilized to determine the backup radials which define the safe easternmost limit of the procedure turn area.
Second, as near as can be determined the low frequency receiver was tuned between 325 kcs. and 349 kcs. Again, this frequency is unrelated to that of any facility in this area which could be utilized by this receiver.
