# NTSB DCA11FA052: Boeing 737, N12221, Greenville, MS, May 6, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Field investigation · Final report - Date: May 6, 2011, 02:00 local (07:00 UTC) - Place: Greenville, MS - Coordinates: 33.469165, -90.983612 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.4692&lon=-90.9836&mi=10 - Phase of flight: [Taxi](https://openairdocs.org/ntsb-phases/250) (OpenAirDocs' grouping) - Defining event: [Taxi-to runway: Airport occurrence](https://openairdocs.org/ntsb-events/070) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report December 27, 2011 - Report: Approved by Office Director - NTSB office: Major Investigations Division - NTSB case key (mKey): 79069 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA11FA052 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/79069/pdf - Page: https://openairdocs.org/ntsb/DCA11FA052 ## Probable cause The failure of a utility pipe beneath the ramp surface, which caused a localized void in the soil and resulting reduction in the load bearing capability of the ramp. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Runway/land/takeoff/taxi surface](https://openairdocs.org/ntsb-findings/03023000): Environmental issues › Physical environment · Contributed to outcome (probable cause); cases with it: [Boeing 737-824, 1 case](https://openairdocs.org/ntsb-findings/03023000/cases.md?model=13844BZ), [All aircraft, 253 cases](https://openairdocs.org/ntsb-findings/03023000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Taxi-to runway: Airport occurrence](https://openairdocs.org/ntsb-events/070) (defining event); cases with it: [Boeing 737-824, 1 case](https://openairdocs.org/ntsb-events/070/sequence.md?model=13844BZ), [All aircraft, 56 cases](https://openairdocs.org/ntsb-events/070/sequence.md) ## Analysis A failed utility pipe caused erosion of the soil beneath the reinforced concrete ramp resulting in a void beneath the ramp surface. When the airplane taxied over this area of the ramp, the left main landing gear penetrated the concrete and sank into the void. Without the support of the soil beneath the concrete, the ramp surface was not strong enough to support the accident airplane. ## Factual narrative HISTORY OF FLIGHT On May 6, 2011, at 0200 central daylight time, a Boeing 737-800, registered as N12221, was taxiing from a paint facility to the runway for an anticipated takeoff from Mid Delta Regional Airport (GLH), Greenville, MS. During taxi, about 100 to 150 yards from its parking spot, the aircraft's left main landing gear assembly sank into the ramp surface. The two pilots onboard were not injured. No other people were on the airplane. The airplane was substantially damaged. The airplane was registered to and operated by Continental Airlines under the provisions of 14 Code of Federal Regulations Part 121 and the flight was to be operated as a non-revenue repositioning flight to George Bush Intercontinental Airport (IAH), Houston, TX. According to the captain, he and the first officer immediately initiated the evacuation checklist and exited the airplane. DAMAGE TO AIRPLANE The left main landing gear strut failed and the airplane settled onto the left engine and rear fuselage, damaging the engine cowl and rear fuselage sheet metal. AIRPORT INFORMATION According to FAA personnel who examined the ramp after the event, the thickness of the concrete varied from 6 to 6 1/2 inches and was reinforced by 3/4 inch square rebar. A large void was found directly beneath the area of sunken ramp pavement. The void was about 6 feet deep and 20 feet across. Further examination of the void revealed the presence of a failed utility water pipe, which was found to have failed at a pipe joint. ## Aircraft - Registration: [N12221](https://openairdocs.org/aircraft/N12221), registered now, S/N 28930, built 1998 (OpenAirDocs) - Reported make and model: BOEING 737 (800) - Registry model: [Boeing 737-824](https://openairdocs.org/model/boeing-737-824) (registry code 13844BZ) (OpenAirDocs) - Registry engine: [CFM International CFM56 series](https://openairdocs.org/engine/cfm-international-cfm56-series) (registry code 13802, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 28930 - Airframe hours: 40491 - Damage: Substantial damage - Flight: Positioning, Part 121 - Operator: Continental Airlines Inc - Registered owner: Wells Fargo Bank Northwest NA Trustee - Airworthiness certificate: Standard, Transport - Departed: GLH, Greenville, MS - Destination: IAH, Houston, TX - Flight plan: Unknown - Airport: GLH, Mid Delta Regional Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 41; injuries: none; airline transport, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review April 19, 2011; seat: left; flight hours: 11,000 total, 5,500 in this make and model, 4,600 as pilot in command, 210 in the last 90 days, 67 in the last 30 days, 3 in the last 24 hours - Co-pilot; age 36; injuries: none; flight instructor, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review August 15, 2010; seat: right; flight hours: 10,000 total, 2,000 in this make and model, 3,800 as pilot in command, 180 in the last 90 days, 50 in the last 30 days, 8 in the last 24 hours ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20110506008009A](https://openairdocs.org/incident/20110506008009A), May 6, 2011: Boeing 737-824, Greenville, MS, Substantial damage. While taxing out of paint facility to active runway the aircraft encountered a sink hole that opened during taxi over ramp causing left landing gear/left… ## Other investigations on N12221 (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB IAD99FA052](https://openairdocs.org/ntsb/IAD99FA052), Jul 8, 1999: Boeing 737-824 (N12221), Atlantic Ocean (Atlantic Ocean), minor damage. Probable cause: the aircrew's inadvertent encounter with unforecast clear air turbulence. From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.