US Airways Boeing 737-3B7 incident
Boeing 737-3B7 · Incident: aircraft structural failure
Event
- NTSB case
- ENG09IA009
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Incident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Airline
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Not recorded
Boeing 737-3B7
- Aircraft type
- Boeing 737
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N506AU
- Operator
- US Airways
- Onboard fatalities
- Unknown
- Route
- From not recordedTo not recorded
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 121: Air Carrier
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Other
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Aircraft structural failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Minor
Cause areas
- Aircraft › Aircraft systems
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
On July 15th, 2009, US Airways reported that the Left Hand (LH) Main Landing Gear (MLG) from the incident airplane was found to have a hydraulic fluid leak through a pin hole on the forward side of the outer cylinder. The leaking gear was sent to AAR Landing Gear Services (LGS) where ultrasonic inspection found crack indications approximately 31 inches from the open end of the outer cylinder. The main landing gear was disassembled and subsequent magnetic particle inspection found a long, sharp indication through the chrome plating in the working inner diameter (ID) section of the outer cylinder. The subject outer cylinder was sent to Boeing Material and Process Technology in Seattle Washington for fracture analysis.
It was reported that the subject outer cylinder had been through three overhauls, the first two being performed by US Airways. It was further reported that during the first two overhauls, US Airways did not perform any rework on the working ID of the cylinder. AAR performed the last overhaul and it was reported that at that time, corrosion was found and removed from the working ID section of the cylinder in accordance with the component maintenance manual (CMM). The oversized ID surface was then chrome plated and ground to the design diameter.
AAR overhauled the LH MLG in December 2008, and it was installed in the incident airplane in April 2009. The subject gear accumulated a total cycles of 40,639 (379 since last overhaul) and a total hours of 59,837 (606 since last overhaul).
A crack measuring 1.95” was present on the working ID on the forward side of the outer cylinder. Several microcracks of varying lengths were also found present on this region. The primary crack was made up of three cracks that had linked together. The cracks originated from heat induced cracks that were present on the ID surface and propagated primarily by fatigue towards the outer diameter (OD) surface of the cylinder. The microcracks that were present on the region originated and propagated in a similar manner. The heat induced cracks were the result of abusive grinding/polishing of the chrome plate that was applied during the last overhaul.
Probable cause
The failure of the left hand main landing gear was caused by heat induced cracks resulting from abusive grinding/polishing of the chrome plate that was applied during the last overhaul.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ENG09IA009
- Event ID
- 20090730X12915
- Case number
- ENG09IA009
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 75c31bbc12f6cf2f3f6b7edf7566e87f211ecb8b81d6e6a597783023e9141f4f; retrieved 2026-09-15T12:04:48.512Z.