Delta Air Lines Flight 2461
Boeing 737-232 · Incident: airframe, component or system failure on approach
From Boston Logan International Airport (BOS) to Orlando International Airport (MCO)
Event
- NTSB case
- MIA99IA046
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Incident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Airline
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Boeing 737-232
- Aircraft type
- Boeing 737
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N327DL
- Operator
- Delta Air Lines
- Onboard fatalities
- Unknown
- Route
- From Boston Logan International Airport (BOS), Boston, MATo Orlando International Airport (MCO)
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 121: Air Carrier
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Approach · VFR pattern turn to base
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Airframe, component or system failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Minor
Cause areas
- Electrical system, battery › Discharged
- Electrical system, fuse › Open
- Electrical system, rectifier › Undetermined
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The auxiliary power unit (APU) was started on base leg. The first officer called for gear and flaps 15. The airplane experienced a total loss of electrical power as the gear and flaps were extended. The APU did not start, and the battery indicated between 17 to 18 volts. Checklist procedures were accomplished and electrical power was unable to be restored. A go-around was initiated, and a subsequent landing was made without further incident. Examination of the electrical system revealed the DC voltmeter in the cockpit was reading 2 volts high. The battery was discharged due to a loss of electrolyte, and there were latent shorted failures of the No. 1 and 2 generator control unit (GCU) blocking diodes. The failure mode of the diodes was not determined. The failures created an excessive current drawn from both GCUs, during the flight crews attempted APU start, immediate overload of the AC power supply input fuses internal to each GCU, loss of the No.1 and 2 generators, complete discharge of the battery, and subsequent total loss of electrical power.
Probable cause
A discharged battery due to a loss of electrolyte, and the latent shorted failures of the No. 1 and 2 generator control unit (GCU) blocking diodes (CR910) for undetermined reasons. These failures resulted in an excessive current drawn from both GCUs, during the flight crew's attempt to start the auxiliary power unit, that caused the immediate overload (opening) of the AC power supply input fuses (POR fuses) internal to each GCU, and subsequent loss of the No.1 and 2 generators; complete discharge of the battery, and subsequent total loss of electrical power. Contributing to the incident was the incorrect reading of the cockpit DC voltmeter (read higher than actual reading) allowing the flight crew to depart with an unreliable (discharged) battery.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record MIA99IA046
- Event ID
- 20001211X11596
- Case number
- MIA99IA046
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 8b7c4f718bbfb8d387a43c879497732f57a689a4e08e9b0a28d7473a8bc8d2b6; retrieved 2026-09-18T17:01:40.233Z.