Narrative:

Upon landing; the first officer was unable to initially unlock and deploy the thrust reversers. He pulled and they would not unlock. He bumped the thrust levers forward and pulled them back against the stops and tried again unsuccessfully. On the third attempt; the thrust reversers then unlocked and deployed normally. Approach and landing normal; runway 31C. My first officer was cognizant of the abnormality as he tried so his response was immediate; I would estimate 2-3 seconds from initial attempt to the third attempt which was successful. In the years we have been flying the 737-700; I have had this happen on a flight of mine about 20 times; probably more in the earlier history of the airframe; but about once a year in the last 5 years. This event did mirror that of a 737-700 accident as described by the accident crew. There appears to be some sort of anomaly in the -700 thrust reverser system that at times inhibits a timely deployment. Most runways this condition would seldom be a factor. However; landing mdw with all braking modes bracketed except maximum; the inability to deploy the thrust reversers immediately becomes a crucial safety issue. We need to understand and fix the anomaly. Callback conversation with reporter revealed the following information: reporter advised that his airline has regulatory approval to compute landing weight restrictions using a 'reverse thrust credit.' thus; when landing in a runway limited situation the availability of reverse thrust is required to satisfy the limit. Reporter further stated there is no specific response to a failure to deploy situation; the assumption being the FAA mandated 15% additional runway length requirement will prove adequate.

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Original NASA ASRS Text

Title: B737-700 Captain reports unacceptable frequency of failure of thrust reversers to deploy when commanded.

Narrative: Upon landing; the First Officer was unable to initially unlock and deploy the thrust reversers. He pulled and they would not unlock. He bumped the thrust levers forward and pulled them back against the stops and tried again unsuccessfully. On the third attempt; the thrust reversers then unlocked and deployed normally. Approach and landing normal; Runway 31C. My First Officer was cognizant of the abnormality as he tried so his response was immediate; I would estimate 2-3 seconds from initial attempt to the third attempt which was successful. In the years we have been flying the 737-700; I have had this happen on a flight of mine about 20 times; probably more in the earlier history of the airframe; but about once a year in the last 5 years. This event did mirror that of a 737-700 accident as described by the accident crew. There appears to be some sort of anomaly in the -700 thrust reverser system that at times inhibits a timely deployment. Most runways this condition would seldom be a factor. However; landing MDW with all braking modes bracketed except MAX; the inability to deploy the thrust reversers immediately becomes a crucial safety issue. We need to understand and fix the anomaly. Callback conversation with Reporter revealed the following information: Reporter advised that his airline has regulatory approval to compute landing weight restrictions using a 'reverse thrust credit.' Thus; when landing in a runway limited situation the availability of reverse thrust is required to satisfy the limit. Reporter further stated there is no specific response to a failure to deploy situation; the assumption being the FAA mandated 15% additional runway length requirement will prove adequate.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.