Boeing 737-800Miami Air International
State College, PA, USA · 2005-11-20·N734MA
What happened
NTSB summary, verbatimDuring the approach, the captain had disconnected the autopilot, but had left the autothrottles engaged in what is known as "mixed-mode" method of flight control in which control of the flight path is mixed between manual and automatic means. During this time, the autothrottle began to track an airspeed which had been previously selected in the mode control panel speed window. The captain disconnected the autothrottles, but did not retard the throttles to idle. Therefore, automatic speedbrake deployment did not take place during the first touchdown. During the resultant bounce, the captain then retarded the thrust levers to idle, the speedbrakes deployed, there was a loss of lift and nose up pitching moment, and a tailstrike resulted. The airplane manufacturer recommended autothrottle use only when the autopilot was engaged. They also advised if the airplane bounced while landing, the pilot should hold or re-establish a normal landing attitude and add thrust as necessary to control the rate of descent, and that thrust need not be added for a "shallow skip or bounce," however, if a "high, hard bounce" occurred, the pilot should initiate a go-around. Information concerning the dangers of mixed-mode operations and bounced landing recovery was available to the operator and Federal Aviation Administration (FAA); however there were no prohibition on mixed-mode operations, nor were bounced landing recovery guidance required to be listed in any of the operator's FAA approved manuals. Two months prior to the accident, the Safety Board issued a recommendation to the FAA; to require air carriers to incorporate bounced landing recovery techniques in their flight manuals and to teach these techniques during training. As a result the FAA issued a Safety Alert for Operators (SAFO), which "recommended" each airline, include bounced landing recovery techniques in their manuals and training; however since the SAFO was not mandatory, the Safety Board requested the FAA survey air carriers to establish how many had adopted the SAFO. The Safety Board advised the FAA that until the results of the SAFO were known, the Safety Board's recommendation would remain classified; Open Acceptable Response.
Photographs
3the aircraft, and what the investigators foundPhotographs are NTSB docket attachments — works of the US government, in the public domain. Captions are the Board’s own.
Probable cause
the Board's determinationThe pilot's improper touchdown and recovery from a bounced landing. Factors to the accident were the operator's failure to provide sufficient information on the use of autothrottles and bounced landing recovery techniques, along with the Federal Aviation Administration's failure to require the inclusion of mixed-mode flight control guidance and bounced landing recovery techniques in operator pilot training programs and flight manuals.
Sequence of events
8 timed eventsfrom the FDR factual report · claude-sonnet-5- 85,985.8 SRNlandingp.4Left and right main landing gear transitioned from "Air" to "Grnd" while at 132 knots ground speed
- 85,986.3 SRNlandingp.4Left main landing gear transitioned back to "Air"
- 85,986.5 SRNlandingp.4Right main landing gear transitioned back to "Air"
- 85,987.9 SRNlandingp.4Spoilers 3, 4, 9, and 10 all began to increase while the aircraft maintained 132 knots ground speed
- 85,989.3 SRNlandingp.4Left main landing gear transitioned to "Grnd"
- 85,989.5 SRNlandingp.4Right main landing gear also transitioned to "Grnd"
- 85,989.4 SRNlandingp.4Spoiler 3 increased to 32 degrees, Spoiler 4 to 35 degrees, Spoiler 9 to 37 degrees, and Spoiler 10 to 31 degrees; Spoiler Ground Speed Brake transitioned from "Not Up" to "Panels Up"; vertical acceleration peaked at 2.5 g's
- 85,993.3 SRNlandingp.4Nose landing gear transitioned from "Air" to "Grnd" while at 121 knots ground speed
NTSB analysis
from the final reportDuring the approach, the captain had disconnected the autopilot, but had left the autothrottles engaged in what is known as "mixed-mode" method of flight control in which control of the flight path is mixed between manual and automatic means. During this time, the autothrottle began to track an airspeed which had been previously selected in the mode control panel speed window. The captain disconnected the autothrottles, but did not retard the throttles to idle. Therefore, automatic speedbrake deployment did not take place during the first touchdown. During the resultant bounce, the captain then retarded the thrust levers to idle, the speedbrakes deployed, there was a loss of lift and nose up pitching moment, and a tailstrike resulted. The airplane manufacturer recommended autothrottle use only when the autopilot was engaged. They also advised if the airplane bounced while landing, the pilot should hold or re-establish a normal landing attitude and add thrust as necessary to control the rate of descent, and that thrust need not be added for a "shallow skip or bounce," however, if a "high, hard bounce" occurred, the pilot should initiate a go-around. Information concerning the dangers of mixed-mode operations and bounced landing recovery was available to the operator and Federal Aviation Administration (FAA); however there were no prohibition on mixed-mode operations, nor were bounced landing recovery guidance required to be listed in any of the operator's FAA approved manuals. Two months prior to the accident, the Safety Board issued a recommendation to the FAA; to require air carriers to incorporate bounced landing recovery techniques in their flight manuals and to teach these techniques during training. As a result the FAA issued a Safety Alert for Operators (SAFO), which "recommended" each airline, include bounced landing recovery techniques in their manuals and training; however since the SAFO was not mandatory, the Safety Board requested the FAA survey air carriers to establish how many had adopted the SAFO. The Safety Board advised the FAA that until the results of the SAFO were known, the Safety Board's recommendation would remain classified; Open Acceptable Response.