# NTSB Incident CHI90IA006
> **BOEING 757-251** · 1989-10-09 · SAN FRANCISCO, CA, USA · NONE
## Event
- **NTSB number:** CHI90IA006
- **Event ID:** 20001213X29555
- **Type:** Incident
- **Date:** 1989-10-09
- **Location:** SAN FRANCISCO, CA, USA
- **Coordinates:** 37.799781, -122.399513
## Injuries
- **Highest injury:** NONE
- **Fatal:** 0
- **Serious:** 0
- **Minor:** 0
- **Uninjured:** 147
- **Total aboard:** 147
## Aircraft
- **Make:** BOEING
- **Model:** 757-251
- **Registration:** N512US
- **FAR Part:** 121
- **Engines:** 2
- **Damage:** MINR
## Conditions
- **Light:** DAYL
- **Weather:** VMC
## Probable cause

THE EXTREME WEAR AND EVENTUAL FAILURE OF A TORQUE TUBE IN THE INBOARD TRAILING EDGE FLAP SYSTEM. INSPECTION AND LUBRICATION INTERVALS WERE A FACTOR, AS WAS THE PHYSICAL LOCATION OF THE TORQUE TUBE WITH REFERENCE TO EXTERNAL FACTORS.

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*Source: [NTSB CAROL](https://data.ntsb.gov/carol-main-public/basic-search?source=ntsb&type=event&ntsb_number=CHI90IA006) · AI Analytics · CC0 1.0*