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went below an altitude of 450 feet on instruments, it was in violation of the company's procedures and consequently of the CAA-approved operating specifications. It was clearly the responsibility of the pilot in command of the flight, Captain Marsh, not to allow his copilot to go below 450 feet unless the aircraft was being flown visually.
As Captain Marsh stated that he had the runway in sight from 500 feet on down, it was his duty to take over the flying of the aircraft when Briggs indicated to him at an altitude of 500 feet that he (Briggs) did not have visual contact, or to instruct him to start a missed approach. To allow the copilot to continue a descent on instruments was clearly contrary to the carrier's CAA-approved operating procedure, because the meaning of a minimum altitude is that all flight below that level shall be made exclusively by visual means.
Mention has been made earlier in this report of the possibility of altimeter error, and it was shown how relatively negligible such accumulative error could be. But the fact remains that once the aircraft was below its specified minimum, it should have been flown exclusively by visual reference to the ground, with little or no aid from altimeter readings in making the approach.
Of course there remains the possibility that the aircraft was being flown visually by Briggs. Adding weight to this possibility are a number of facts which are not to be overlooked. First is the weather. It has been shown that it was deteriorating rapidly at the time and place of the accident. There were clouds and/or fog patches below the 500-foot level and in the aircraft's path. The nature of the damage
