# NTSB LAX92IA027: Mcdonnell Douglas DC-10-10, N1820U, Las Vegas, NV, October 28, 1991

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: October 28, 1991, 07:05 local (15:05 UTC)
- Place: Las Vegas, NV
- Location: 36.1750° N, 115.1372° W: Placed by OpenAirDocs: center of Las Vegas, NV, within about 7 miles (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=36.1750&lon=-115.1372&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 179 uninjured
- Status: Completed, report May 5, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27457
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX92IA027
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27457/pdf
- Page: https://openairdocs.org/ntsb/LAX92IA027

## Probable cause

RUPTURE OF A FORWARD PRESSURE BULKHEAD BECAUSE OF CYCLICALLY INDUCED METAL FATIGUE. FACTORS WHICH CONTRIBUTED TO THE INCIDENT WERE: THE OPERATOR'S DECISION NOT TO STRUCTURALLY MODIFY ITS AIRPLANE IN ACCORDANCE WITH THE MANUFACTURER'S BUT RATHER TO RELY ON THE MANUFACTURER'S ALTERNATIVE RECOMMENDATION OF PERFORMING REPETITIVE VISUAL INSPECTION IN THE SUSPECT AREA: AND THE OPERATOR'S FAILURE TO UTILIZE AN INSPECTION PROGRAM ADEQUATE TO VISUALLY DETECT CRACK DEVELOPMENT IN A PREVIOUSLY IDENTIFIED SUSPECT AREA.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, climb - to cruise
  - fuselage,bulkhead - fatigue
  - maintenance,modification - not performed, company/operator management (contributing factor)
  - maintenance,inspection - inadequate, company maintenance personnel (contributing factor)
- Decompression, descent - emergency
  - fuselage,bulkhead - ruptured (cause)
  - emergency procedure - initiated, pilot in command
  - descent - intentional, pilot in command

## Analysis

WHILE CLIMBING THRU 35,000 FT FOR A CRUISE ALTITUDE OF 37,000 FT, THE CREW HEARD A LOUD 'THUMP' & THE ACFT DEPRESSURIZED. AS THE CREW DESCENDED TO 11,000 FT, THE CABIN ALTITUDE CLIMBED TO 30,000 FT. THE FLT DIVERTED TO A NEARBY ARPT & SAFELY LANDED. EXAM OF THE ACFT DISCLOSED THAT REPETITIVE PRESSURIZATION CYCLES CAUSED THE INITIATION OF A FATIGUE CRACK & THE RESULTANT RUPTURE OF A FORWARD PRESSURE BULKHEAD. OVER 14 YRS EARLIER, DOUGLAS ISSUED SERVICE BULLETINS ADVISING OPERATORS THAT LEAKS COULD OCCUR IN THE FWD PRESSURE BULKHEAD AREA BECAUSE OF METAL FATIGUE. DOUGLAS RECOMMENDED THAT SPECIFIC CORRECTIVE ACTION BE TAKEN WHICH INVOLVED INSPECTING THE AREA AT 1,500 HOUR INTERVALS OR MAKING PERMANENT STRUCTURAL AIRFRAME MODIFICATIONS. CONTRARY TO THE MAJORITY OF ACFT OPERATORS, UNITED CHOSE NOT TO STRUCTURALLY MODIFY THIS ACFT. RATHER, IT CHOSE TO PERFORM RECURRING VISUAL INSPECTIONS FOR LEAKS IN THE SUSPECT AREA. THE ACFT'S PRESSURE BULKHEAD RUPTURED 1,367 HRS AFTER IT LAST INSPECTION.

## Aircraft

- Registration: N1820U (not matched to a registry record)
- Reported make and model: MCDONNELL DOUGLAS DC-10-10
- Category: Airplane
- Serial number: 46619
- Airframe hours: 50708
- Engines: GE CF 6-6 42500 lbs thrust turbo fan
- Damage: Minor damage
- Flight: Part 121
- Operator: United Airlines
- Registered owner: United Airlines
- Airworthiness certificate: Standard, Transport
- Last inspection: Continuous airworthiness, May 18, 1991, 1,367 hours before
- Departed: LAX, LOS ANGELES, CA
- Destination: DEN, DENVER, CO
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 56; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 20,000 total

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 50 statute miles
- Lowest ceiling: none

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Incident 19911028048529I](https://openairdocs.org/incident/19911028048529I), Oct 28, 1991: Doug DC1010, Las Vegas, NV, Minor damage. Experienced rapid decompression. Masks deployed. Found a tear in lower pressure bulkhead. Modification not done.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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