Boeing 757-222 incident near Chicago, Illinois, October 29, 1999
On October 29, 1999 at about 2:32 am local time, a Boeing 757-222, registered N575UA, was involved in an incident near Chicago, Illinois. It was a flight of an unrecorded kind under scheduled airline rules (Part 121). No one was hurt; 68 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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 aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 29, 1999 · about 2:32 am local time
- Place
- Chicago, Illinois
- Type
- Incident
- Injuries
- No one was hurt; 68 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Boeing 757-222 757 · all 757-222s on the register
- Registration
- N575UA · no longer on the register · serial 26689
- Damage
- Not recorded
- Flight
- Flight of an unrecorded kind · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported, "We encountered substantial vertical control flutter FL310-350 .78-.80 Mach with left, center, right autopilot and no autopilot. Flutter stopped when IAS was decreased. Descended to FL310, 250 kts., .75 Mach and had no more flutter. The flight diverted to O'Hare Airport and made an uneventful landing. Maintenance inspections revealed excessive free play in the elevator flight controls. The allowable limit is 0.340 inch and 0.50 inch was measured. The free play was corrected in accordance with the current maintenance manual. The bushings, the left center power control actuator (PCA), two reaction links, and four ilder links were replaced. During a subsequent test flight, vertical oscillations were still present. Further maintenance action included replacing all elevator hinge bearings and four PCA's. The third flight test was successful and the airplane was returned to service. Inspection of two reaction link rod ends revealed axial and radial wear which exceeded allowable limits. Inspection of the 16 hinge bearings revealed 3 bearings had axial and radial wear which exceeded limits and had moderate to severe corrosion. On October 11, 2001, the FAA issued Airworthiness Directive (AD) 2001-20-11 that was applicable to all B-757 series airplanes to "prevent unacceptable airframe vibration during flight, which could lead to excessive wear of elevator bearings and result in reduced controllability of the airplane…" The AD required, "Before further flight after the free-play checks, lubricate the bearings in the elevator PCA load loop and hinge line." Lubrication of the hinge bearings had not been required in a previous AD. The new AD required recurrent inspections every 18 months instead of the previous requirement of 4,000 hours, or 3,000 hours for some models. On January 28, 2001, Boeing issued a maintenance manual revision that corrected improper instructions for elevator free-play checks. The improper procedures in the maintenance manual had been in effect from September 20, 1997, to January 28, 2001.
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
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 20,178 hours in all; 10,882 in this make and model; 179 in the last 90 days; 82 in the last 30 days
- Last flight review: June 30, 1999
- Medical certificate: Class 1 (valid medical--no waivers/lim.)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 23,631 hours
- Last inspection: continuous airworthiness programme, November 16, 1998; 3,160 hours since
- Maximum gross weight: 241,000 lb
- Seats: 196
- Landing gear: retractable
- Engine: P&W PW2037 (turbofan); 0 hours total
The flight
- Departed from: IAD Herndon VA at 11:43 pm
- Destination: SFO San Francisco CA
- Flight plan: IFR
- A second pilot was aboard
Weather at the time
- Light: night
- Wind: from 080° at 3 knots
- Visibility: 7 statute miles
- Sky: scat at 25,000 ft
- Temperature: 50°F (10°C), dew point 46°F (8°C)
- Altimeter: 30.00 inHg
- Observation at 1:56 am from ORD, 105 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 6 | |||
| Passengers | 62 |
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.