# NTSB Incident CHI00IA018
> **Boeing 757-222** · 1999-10-29 · CHICAGO, IL, USA · NONE
## Event
- **NTSB number:** CHI00IA018
- **Event ID:** 20001212X19914
- **Type:** Incident
- **Date:** 1999-10-29
- **Location:** CHICAGO, IL, USA
## Injuries
- **Highest injury:** NONE
- **Fatal:** 0
- **Serious:** 0
- **Minor:** 0
- **Uninjured:** 68
- **Total aboard:** 68
## Aircraft
- **Make:** Boeing
- **Model:** 757-222
- **Registration:** N575UA
- **FAR Part:** 121
- **Engines:** 2
- **Damage:** —
## Conditions
- **Light:** NITE
- **Weather:** VMC
## Probable cause

the in-flight vibration of the airplane's elevator due to excessive freeplay in the elevator control system.  Factors included the corrosion of the elevator PCA reaction link bearings and the elevator hinge bearings, excessive axial and radial wear of the elevator PCA reaction link bearings, the inadequate procedures for lubricating the elevator hinge bearings, and the incorrect procedures for measuring elevator free play.

---
*Source: [NTSB CAROL](https://data.ntsb.gov/carol-main-public/basic-search?source=ntsb&type=event&ntsb_number=CHI00IA018) · AI Analytics · CC0 1.0*