Boeing 737 incident near Phoenix (Phx), Arizona, June 27, 2008
On June 27, 2008, a Boeing 737, registered N514AU, suffered minor damage in an incident during pushback/tow (engine not oper) near Phoenix (Phx), Arizona (Phoenix Sky Harbor Intl. airport). It was flown under scheduled airline rules (Part 121). No one was hurt.
The NTSB's probable cause their words, unchanged
The failure of the MLG was due to cracking in the cylinder wall resulting from a fatigue mechanism which initiated at, and near the inner diameter (ID) surface, with propagation through the wall toward the outer diameter(OD) surface. Crack initiation was due to base metal damage which took the form of over tempered martensite (OTM) and chemical attack/pitting of the base metal.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 27, 2008
- Place
- Phoenix (Phx), Arizona · Phoenix Sky Harbor Intl. · map
- Type
- Incident
- Injuries
- No one was hurt.
- Weather
- not recorded
- Aircraft
- Boeing 737 3B7 · all 737s on the register
- Registration
- N514AU · no longer on the register · serial 23700
- Damage
- Minor damage
- Flight
- Flight · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
In June 2008, after the incident airplane was towed, ground personnel noted that the left hand (LH) main landing gear (MLG) was leaking shock strut fluid from a crack in the wall of the outer cylinder. A visual examination of the outer cylinder revealed a crack located approximately 26” below the shock strut air valve. The outer cylinder had accomplished 3 ground air ground (GAG) cycles after completion of the December 2007 overhaul, and approximately 5836 cycles since the prior overhaul in 2004. The subject outer cylinder developed fatigue cracking in the wall which resulted in leakage of shock strut fluid. The fatigue cracking initiated at and near the ID surface, and propagated through the wall toward to OD until the leakage was detected and the cylinder was removed from service. Crack initiation was due to base metal damage which took the form of over tempered martensite and chemical attack/pitting. The over tempering reduced the strength of the material and caused reduction of shot peen induced residual compressive stresses. The combination of these factors results in the affected material having reduced resistance to fatigue cracking. The ID surface displayed base metal chemical attack which most likely developed during a plating operation on the sealing surface during the 2004 overhaul. The pitting features act as stress raisers, thereby serving as favorable crack initiation sites. The observed ID surface conditions appear to have been created during the overhaul in 2004, with the fatigue cracking occurring once the cylinder was returned to service. The cracking in the cylinder wall was not detected during the 2007 overhaul. Spectrochemical analysis and hardness testing confirmed that the cylinder was fabricated from the specified material, in the required heat treat condition. The cylinder exhibited slightly elevated bulk hydrogen levels, likely caused by the multiple plating and stripping operations during the 2004 overhaul. The condition may have provided a minor contribution to the propagation of the fatigue crack after initiation had occurred.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Aircraft inspection event during pushback/towing
- Aircraft inspection event during pushback/tow (engine not oper)
- Aircraft structural failure during pushback/tow (engine not oper) defining event
The NTSB's findings
- Aircraft › Aircraft systems › Landing gear system › Main landing gear › Damaged/degraded
- Aircraft › Aircraft systems › Landing gear system › Main landing gear › Fatigue/wear/corrosion
- cause Aircraft › Aircraft systems › Landing gear system › Main landing gear › Incorrect service/maintenance
The aircraft
- Last inspection: inspection type not recorded
- Maximum gross weight: 138,500 lb
- Landing gear: retractable
- Engine 1: Cfm 56/3B2 (turbofan); 0 hours total
- Engine 2: Cfm 56/3B2 (turbofan); 0 hours total
- Operator: US Airways INC
The flight
- Flight plan: none
Weather at the time
- Temperature: 0°F (-18°C), dew point 0°F (-18°C)
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.