Page:CAB Aircraft Accident Report, United Airlines Flight 227.pdf/9

 1.15 Tests and Research

Power response curves for the JT8D engines indicate that they will accelerate from idle to takeoff thrust in 6-8 seconds. Approximately 5 seconds of this time interval elapses before 50 percent of available thrust is developed.

Various performance curves approximating the accident conditions, were developed from flight test data. They indicate that idle thrust is required to maintain a stabilized descent rate of approximately 2,300 feet per minute, in the landing configuration. From this condition it is possible to initiate a flare at 148 feet and land with a zero sink rate without any addition of power. This requires that the pilot rotate and maintain the aircraft in the stick-shaker attitude, which would produce an average acceleration of approximately +1.27-g throughout the maneuver. While this will result in some airspeed decay, the touchdown occurs well above the stalling speed.

A more normal recovery from such a rate of descent can be accomplished by flaring at an average landing flare rate, approximately +1.06-g, and adding sufficient power to maintain constant airspeed throughout the maneuver. This landing would require action by the pilot at 375 feet, with the maximum power requirement, 50 percent of takeoff thrust, occurring at an altitude of 50 feet. The power required decreases from this point on because of ground effect.

1.16 Crew Training and Certification Changes

On March 8, 1966, the FAA issued an order for all Principal Operations Inspectors to review their assigned air carrier's jet operating procedures and approved training programs. All operations manuals were to provide procedures to increase pilot awareness of altitude and descent rates. Further, pilot-in-command experience of 100 hours was established as a minimum level before he could allow the copilot to execute a takeoff, approach, or landing. The order imposed training requirements for a high rate of descent demonstration by pilots in command of turbojet aircraft. The maneuver shows the undesirable landing approach profile and its effects. Also the minimum numbers and types of landings were increased for pilots who were receiving their initial checkout in turbojet equipment. The new criterion of 35 landings, which may be reduced to 25 for exceptional pilots, requires at least six day landings and five night landings be made without reference to visual or electronic glide slopes. Additional special emphasis is to be placed on training in the proper use of artificial horizons and flight directors and the attitudes necessary to maintain level flight in various thrust and airplane configurations.

2.1

The evidence indicates that there was no significant malfunctioning of the aircraft systems or components. The separation of the landing gear and No. 1 engine