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testimony of all surviving crewmembers, substantiates that both aircraft were capable of operation within their design criteria.
Flight 42 (N748TW) was certificated and maintained within the framework of the existing Federal Aviation Regulations and company rules in effect at the time of the collision.
Although one altimeter installed aboard Flight 853 (N62180) was not of an acceptable type, it could be expected to perform with accuracy equal to a like model that had met the TSO requirements. N6218C was capable of safe flight and there was no evidence to indicate the unauthorized altimeter in any way contributed to the accident. The following factors tend to discount the likelihood of any material error:
(1) The static system design incorporates separate static systems for the captain's and first officer's positions.
(2) The altimeter scale error correction at 10,000 feet is usually much less than the 80 feet maximum tolerance.
(3) During the several flights flown after the completion of the phase check, there were no reported discrepancies in the altimeter systems.
(4) The testimony of the first officer of EA 853 that nothing abnormal was noted in the altimeter system during the flight from Boston.
(5) Eastern Air Lines procedures require altimeter change if the crew notes as much as a 50-foot difference in readings.
The Board must rule out the possibility of collision because of altimeter malfunctions or false altitude indications. The possible errors caused by altimeter system design, scale correction, and atmospheric conditions are so negligible that both aircraft would not have been more than approximately 100 feet above or below their indicated altitudes. The design incorporation of separate aircraft altimeter-static systems on the EA 853 aircraft would make it highly improbable that any significant errors would go undetected by crewmembers. In addition, there were no reported discrepancies in the altimeter systems of either aircraft during the previous several flights and surviving crewmembers stated there was nothing of an abnormal nature noted in the altimeter systems of their respective aircraft just prior to the collision. It is therefore concluded that the maintenance of the altimeters system aboard EA 853, while not meeting standards as specified in the maintenance manual, was not a factor in the accident.
Testimony and flight recorder data indicate that TW 42 was being flown in accordance with the clearance issued by Air Traffic Control. Just prior to arriving at the Carmel VORTAC from the northwest, the aircraft had been descended to an altitude of 11,000 feet and was flying above a cloud deck with no restrictions to visibility.
EA 853 was being operated in accordance with the clearance issued by Air Traffic Control and was in level flight at 10,000 feet, in and out of the tops of clouds as it approached the Carmel, New York VORTAC from the northeast. This
