Paradise Airlines Flight 901A

Investigation

Investigators from the CAB arrived at the headquarters of Paradise Airlines on the day the plane went missing, even before the crash site had been located. Just as company president Herman Jones was about to meet with officials from the CAB and the FAA the next morning, word came in that the crash site had been located. After the meeting, investigators impounded all of the company's records. More than thirty CAB investigators were involved in the probe, studying the maintenance records of the plane, interviewing witnesses, studying the weather reports, and examining pieces of the wreckage for indications of the cause of the crash. The aircraft was not equipped with a cockpit voice recorder. All four propeller hub assemblies were located and shipped, with the broken propeller blades, to a shop in Hayward, California, to determine how much power the engines were generating when the plane crashed. By May 1, investigators had recovered the key instruments and the radio equipment of the crashed plane. A salvage operator began removing the rest of the plane, taking the pieces to a warehouse at Reid–Hillview Airport near San Jose and storing them there in case they were needed by CAB investigators.

The CAB held a probable cause hearing in Oakland from June 2–5. The investigative team learned that pilots had made eleven reports of problems with the plane's directional instruments in the nine months before the crash. Testimony from the Tahoe Airport's weather observer repeated some of what was said during the appeal of the FAA's suspension of Paradise Airlines' operating certificate. The pilot of the Paradise Airlines flight that left Lake Tahoe an hour before the crash testified that he took off because the weather observer assured him that the weather was clear enough, but the observer said that he did not recall such a conversation. The pilot was asked about the company's procedures for operating in bad weather, and the company's financial arrangements with its pilots. He explained that the pilots were paid a flat fee of $35 per flight. In the hearing, the CAB interviewer hinted that the financial arrangements gave an incentive to pilots to avoid diversions due to bad weather because they would not be paid for their additional time.

Investigators learned that neither of the company's aircraft operating at the Tahoe Airport had been equipped with de-icing equipment, and that Flight 802 had picked up rime ice half an inch thick when it was flying out of the Tahoe Valley earlier that day. They also learned that the maintenance records of the company's aircraft had several discrepancies, but that the FAA had no enforcement actions pending at the time of the crash. Previous flight crews had noted minor errors in the altimeters aboard the aircraft, and instrument repairmen had worked on both altimeters in the plane that crashed in the incident. The first officer's fluxgate compass was known to be faulty on the day of the crash, with crews reporting that it was "completely unreliable in any kind of banking turn". Instrument technicians had worked on it two days earlier, but it was still not functioning reliably. Investigators learned that there had been gaps in the cloud cover when the flight had arrived, but a snow squall hit the north end of the airport just as the aircraft was approaching from the north for landing.

On July 15, 1965, the CAB released its final report. The report stated that the crash was caused by pilot error, a falsified weather report, and illegal maintenance practices. The accident report stated:

The CAB report stated that maintenance had been performed on both altimeters and the No. 2 fluxgate compass transmitter on the evening before the accident. Paradise Airlines did not have any of its own maintenance personnel, and used an FAA-approved maintenance company located at Oakland Airport. The technicians who had performed the work had also inspected and signed off on their own work. The report stated the mechanic who had worked on the compass had never worked on that type of transmitter, and did not refer to any technical publications for guidance. He failed to check the entire system and did not perform all of the actions outlined in the maintenance manual. The technician who performed the work on the altimeters could not remember whether or not he had secured the barometric adjusting screw that he had unscrewed during the adjustments he had made. The reinstallation of the unit had been performed by a mechanic who had never performed that type of work before, and had been done without performing all of the checks outlined in the manual. The captain's altimeter that was recovered from the wreckage showed a pre-impact discrepancy that would have indicated the aircraft was flying 280 ft higher than its true altitude. In addition, the compass had an error of 15 degrees or more, which at the moment of the crash could have caused the aircraft's indicated heading to be more southerly than the aircraft's true heading.

Weather reports that were available to the company dispatcher included warnings of icing conditions in the Tahoe Airport area and that clouds and snow showers would be obscuring the mountains in western Nevada. None of this information was communicated to the captain of Flight 901A before or during the flight, and the board speculated that ice accumulation on the aircraft may have affected its ability to gain sufficient altitude to clear the mountains while attempting to divert.

The report concluded that when the crew abandoned the approach to Tahoe Valley Airport, they decided to proceed through Daggett Pass for unknown reasons, possibly to avoid an area of known icing that they had passed through during their descent, or possibly because icing was preventing the aircraft from being able to climb higher. The pilots would have been aware that an altitude of 9000 ft would have given the aircraft 1500 ft of terrain clearance through the pass's center, and an easterly heading from the southern end of the lake would have taken the aircraft through the pass's center, an opening several miles wide. The aircraft leveled off at 9,000 feet, either because the pilots believed that they had sufficient clearance, or because icing prevented further altitude gains. It was possible that the crew was unaware that its heading, altitude, or both, were not being accurately shown on the aircraft's instruments, and that undetected tail winds might also have affected the flight's heading.