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3. EA 853 was properly certificated, and dispatched and was capable of safe flight.
4. Altimeter (SN 197523) had been modified in compliance with Kollsman Service Bulletin No. 9, and should have been capable of meeting the performance requirements of TSO C-10A.
5. Both aircraft were capable of operating within their normal design limitations.
6. The powerplants of both aircraft were developing power to the time of impact.
7. TW 42 crew reset the altimeters to 29.63 upon passing through 18,000 feet on their descent.
8. EA 853 was given the Bradley altimeter setting of 29.58 upon passing Hartford, Connecticut.
9. TW 42 was at the assigned altitude of 11,000 feet just prior to the collision.
10. EA 853 was at or near the assigned altitude of 10,000 feet just prior to sighting the TWA aircraft.
11. In the Carmel, New York area at the time of the accident there was an overcast cloud condition, the tops of which were generally just above 10,000 feet m.s.l. Buildups were scattered through the area with tops tending to be higher to the north than to the south, providing an apparent upslope condition to the north.
12. The crew of EA 853 observed TW 42 at about their 2 o'clock position and believing them to be at their same altitude on a collision course, executed an emergency pullup to avoid a collision.
13. The crew of TW 42 had an instantaneous view of the EAL aircraft and executed an immediate reactionary evasive maneuver by making an abrupt right turn.
14. The left Wing of TW 42 collided with the right vertical fin and horizontal stabilizer of EA 853.
15. The aircraft collided at an altitude of approximately 11,000 feet at approximately 1619 e.s.t.
(b) Probable Cause
The Board determines the probable cause of this collision accident was misjudgment of altitude separation by the crew of EA 853 because of an optical illusion created by the up-slope effect of cloud tops resulting in an evasive maneuver by the EA 853 crew and a reactionary evasive maneuver by the TW 42 crew.
BY THE CIVIL AERONAUTICS BOARD:
/s/ CHARLES S. MURPHY
Chairman
/s/ ROBERT T. MURPHY
Vice Chairman
/s/ G. JOSEPH MINETTI
Member
/s/ WHITNEY GILLILLAND
Member
/s/ JOHN G. ADAMS
Member
