# NTSB MIA94FA001: Mcdonnell Douglas MD-83, Miami, FL, October 3, 1993 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Field investigation · Final report - Date: October 3, 1993, 15:55 local (19:55 UTC) - Place: Miami, FL - Location: 25.7743° N, 80.1937° W: Placed by OpenAirDocs: center of Miami, FL, within about 6 miles (OpenAirDocs) - Nearby events: https://openairdocs.org/map.md?lat=25.7743&lon=-80.1937&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 1 serious, 1 minor, 80 uninjured - Status: Completed, report November 1, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 37403 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA94FA001 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/37403/pdf - Page: https://openairdocs.org/ntsb/MIA94FA001 ## Probable cause THE FAILURE OF THE WATER HEATER RELAY AND THE OVERPRESSURE RELIEF VALVE TO OPERATE PROPERLY. IN ADDITION, THE DESIGN OF THE RELIEF VALVE WAS INADEQUATE IN THAT IT ALLOWED THE O-RING TO MIGRATE FROM ITS NORMAL POSITION PREVENTING THE VALVE FROM OPENING. ## 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 - misc eqpt/furnishings,galley - life expired (cause) - misc eqpt/furnishings,galley - inoperative (cause) - acft/equip,inadequate design, manufacturer (cause) - misc eqpt/furnishings,galley - pressure excessive (cause) - Explosion, climb - to cruise - misc eqpt/furnishings,galley - exploded ## Analysis THE WATER HEATER IN THE FORWARD GALLEY EXPLODED. EXAMINATION REVEALED THAT THE CONTACTS OF THE WATER HEATER RELAY, WHICH, WHEN ENERGIZED, PROVIDES ELECTRICAL POWER TO THE 3 HEATER ELEMENTS, WERE ROUGH, RAGGED, DISCOLORED, AND SHOWED EXCESSIVE EROSION. ACCORDING TO THE MANUFACTURER, WHEN A RELAY EXCEEDS ITS LIFETIME, IT IS POSSIBLE FOR EROSION AND WEAR ON THE SURFACE TO CAUSE THE CONTACTS TO STICK IN THE CLOSED POSITION. IN ADDITION, THE PRESSURE RELIEF VALVE, WHICH IS DESIGNED TO CRACK AT 65 PSI, WAS TESTED TO 300 PSI WITHOUT CRACKING. UPON DISASSEMBLY, THE O-RING WAS FOUND TO HAVE MIGRATED FROM ITS NORMAL LOCATION INTO THE LOWER VALVE BODY WHERE IT LODGED BETWEEN THE INSIDE DIAMETER AND THE HEAD OF THE POPPET. IN THIS CONDITION, THE O-RING PRESENTED A COMPLETED FLOW BLOCKAGE AND PREVENTED THE PRESSURE RELIEF VALVE FROM OPENING. ## Factual narrative HISTORY OF FLIGHT On October 3, 1993, about 1555 eastern daylight time, 9Y-THR, a McDonnell Douglas MD-83, experienced an explosion in the forward galley during climb to cruise altitude. The airplane was registered to and operating as British West Indies Airlines [BWIA] flight No. 431, scheduled, international, passenger service from Miami, Florida, to Barbados. The airplane was substantially damaged, 1 flight attendant received serious injuries, 1 flight attendant received minor injuries, 82 persons were not injured. Visual meteorological conditions prevailed at the time and an IFR flight plan was filed. The flight had originated from Miami, Florida, about 1525 and landed back at Miami, Florida, around 1625 the same day. Examination of the airplane revealed that a water heater, Nordskog model, had over pressurized and exploded. The entire forward galley and the cabin wall to the cockpit was destroyed. The water heater was removed and examined at the NTSB laboratory. All failures noted were consistent with overload. The over pressure valve was examined and the "O" ring had migrated blocking the valve "Pop Off" function. The electrical contacts to the heater element were found failed in a way that allowed constant power to the element. Details of these examinations are included in this report as attachments. ## Aircraft - Registration: 9YTHR (not matched to a registry record) - Reported make and model: MCDONNELL DOUGLAS MD-83 - Category: Airplane - Serial number: 49568 - Airframe hours: 14657 - Engines: P&W JT8D-219 20000 lbs thrust turbo jet - Damage: Substantial damage - Flight: Part 129 - Operator: British West Indies - Registered owner: British West Indies - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, September 12, 1993, 162 hours before - Destination: TBPB, BARBADOS, OF - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 39; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 8,500 total, 4,200 in this make and model, 220 as pilot in command, 200 in the last 90 days, 65 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 330° at 5 knots - Visibility: 7 statute miles - Lowest ceiling: 14,000 ft overcast - Temperature: 79 °F, dew point 73 °F - Altimeter: 30.00 inHg - Observed at: MIA, 100 nm away 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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.