# NTSB LAX86MA275: Boeing 747-122, N4718U, Pacific Ocean (Pacific Ocean), June 24, 1986

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Major investigation · Final report
- Date: June 24, 1986, 12:00 local (20:00 UTC)
- Place: Pacific Ocean (Pacific Ocean)
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 436 uninjured
- Status: Completed
- Report: Approved by Office Director
- Safety recommendations: Yes
- NTSB case key (mKey): 25284
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX86MA275
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/25284/pdf
- Page: https://openairdocs.org/ntsb/LAX86MA275

## Sequence of events

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

- Miscellaneous/other, cruise - normal
  - reason for occurrence undetermined (cause)
  - air cond/heating/pressurization - blocked(partial) (contributing factor)
  - fuselage,cabin - other (cause)
  - physical impairment(other organic problem), other person

## Analysis

WHILE UAL FLT 1 WAS CRUISING AT FL 310, APRX 1.8 HR AFTER TAKEOFF, A FLT ATTENDANT (F/A) RPRTD A HEADACHE & LIGHTHEADED-NESS. THE FLT CLIMBED TO FL 350, THEN ANOTHER F/A & SVRL PAX RPRTD SIMILAR SYMPTOMS. AT THAT TIME, THE TROPOPAUSE WAS AT40,000'. AS THE FLT CONTD, THE TROPOPAUSE LOWERED SOME, THEN INCREASED IN ALT. SUBSEQUENTLY, SVRL OTHER OCCUPANTS HAD SIMILAR SYMPTOMS. THE CAPT TURNED ON THE 'NO SMOKING' SIGN AS A PSBL SOLUTION, BUT THIS DID NOT SEEM TO HELP. NO HAZARD-OUS CARGO LEAK WAS FND & NO PAX ADMITTED CARRYING BUTANE OR OTHER SUCH SUBSTANCE. THOSE AFFECTED BY THE PSBL IRRITATING OR GASEOUS SUBSTANCE WERE IN ZONES B, C, D, E OR THE UPPER DECK OF THE ACFT. NO OCCUPANTS OF ZONE A OR THE FLT DECK WEREAFFECTED, EXCEPT THE 2ND OFFICER RPRTD A SLIGHT PAIN BETWEEN HIS EYEBROWS AFTER SPENDING 10 TO 20 MIN IN THE PAX CABIN. AN INVESTIGATION FOR A POSSIBLE OZONE ENCOUNTER WAS MADE, BUT NO SPECIFIC EVIDENCE WAS FOUND. THE CATALYTIC CONVERTERS IN THE AIR CONDITIONING SYS WERE TESTED & FOUND TO BE 51.2% EFFICIENT.

## Aircraft

- Registration: [N4718U](https://openairdocs.org/deregistered/N4718U-1998-02-17), registration cancelled 1998-02-17, S/N 19879 (OpenAirDocs)
- Reported make and model: BOEING 747-122
- Registry model: [Boeing 747-122](https://openairdocs.org/model/boeing-747-122) (registry code 1384872) (OpenAirDocs)
- Category: Airplane
- Serial number: 19879
- Engines: UNKNOWN UNKNOWN turbo fan
- Damage: No damage
- Flight: Part 121
- Registered owner: United Airlines
- Airworthiness certificate: Standard, Transport
- Departed: ORD, CHICAGO, IL
- Destination: HNL, HONOLULU, HI
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 59; airline transport, flight engineer; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 20,170 total

## Weather

- Conditions: Visual (VMC), Day
- Lowest ceiling: none

## Other investigations on N4718U (1)

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.

- [NTSB CHI87FA081](https://openairdocs.org/ntsb/CHI87FA081), Feb 12, 1987: Boeing 747-122 (N4718U), Detroit, MI, no damage

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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