Page:NTSB Aircraft Accident Report, United Airlines Flight 389.pdf/37

 A study of the calculated flightpath of the aircraft using these points reveals that the flightpath was well within the normal operating parameters of a B-727 making a clean descent when operated in conformance with UAL's operating procedures and techniques. The resultant flight profile (See Attachment No. 1), shows an average rate of descent from 35,000 feet to the lake level of approximately 2,000 feet per minute. UAL 389 was cleared from cruising flight at 350 to several lower altitudes; however, these clearances were given in a manner which precluded the necessity of leveling the aircraft and holding any one altitude for a period of time. The descent was continuous and the pointers on the altimeters would have been in continuous motion, making them more susceptible to misreading. Upon breaking out of the clouds between 8,000-10,000 feet, the crew's attention would have been divided between their routine duties preparing for an approach and landing, and maintaining a lookout for other traffic.

Additional calculations were performed based on the flight's reports and the controller's recollection of its location at various times. Based on the extremes of their recollection the ground speed of the flight in the Sturgeon area would have been between 240-300 knots. Using 240 knots a straight line descent from 2,000 feet m.s.l. would have resulted in an impact with the water at 2120:38. If the speed were calculated to be 270 knots the impact would have been at 2120:27 and 2120:14 for 300 knots. All of these performances are well within the operating envelope of the aircraft.

If we assume the flight leveled off at 6,000 feet as their clearance required, and were at 6,000 at the time of their last radio communication with the approach controller, in order to proceed four miles at a speed of 240 knots