Wednesday, April 4, 2018

McDonnell Douglas MD-83, Flight G4-636, N881GA, operated by Allegiant Air: Incident occurred March 19, 2017 near Dayton International Airport (KDAY), Montgomery County, Ohio

The National Transportation Safety Board did not travel to the scene of this incident.

Additional Participating Entities: 
Federal Aviation Administration / Flight Standards District Office; Lakewood, California
United Technologies Aerospace Systems; Rockford, Illinois

Aviation Incident Final Report - National Transportation Safety Board:

Investigation Docket -  National Transportation Safety Board:

National Transportation Safety Board - Aviation Incident Factual Report

Location: Dayton, OH
Incident Number: ENG17IA017
Date & Time: 03/19/2017, 1211 EDT
Registration: N881GA
Aircraft: DOUGLAS DC 9 83
Aircraft Damage: None
Defining Event: Powerplant sys/comp malf/fail
Injuries: 163 None
Flight Conducted Under: Part 121: Air Carrier - Scheduled 


The No. 2 engine fire was caused by the uncontained failure of the generator main rotor. Deformed generator rotating components and/or metal fragments radially released by the generator severed the constant speed drive (CSD)-to-oil cooler return line located adjacent to the generator. The severed line sprayed oil onto hot generator and engine case surfaces that subsequently ignited.

The sections of the generator main rotor that remained intact and the metal fragments recovered from the generator case exhibited extensive thermal and impact damage that precluded material analysis.

The operating history of the failed generator was not available and federal regulations do not require operators to maintain hour and cycle counts for non-life limited components. An estimate of generator operating hours was provided by Allegiant Air and the date of manufacture was provided by UTC Aerospace Systems. Based on the available records the generator main rotor was never overhauled or re-wound and the total operating hours likely exceeded the 40,000 hour recommended overhaul interval specified in UTC Aerospace Systems service information letter (SIL) 449. 

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this incident to be:
The probable cause of the No. 2 (right) engine fire was an uncontained generator failure. Deformed rotating generator components and/or metal fragments radially released by the generator severed the constant speed drive-to-oil cooler return line located adjacent to the generator and caused oil to spray onto hot generator and engine case surfaces that subsequently ignited.


Accessory drives - Failure (Cause)

Factual Information


On March 19, 2017, about 1100 eastern daylight time (EDT), a McDonnell Douglas MD-83, N881GA, operated by Allegiant Air experienced a No. 2 (right) engine fire during approach to Dayton International Airport (DAY), Dayton, Ohio. The crew followed the quick reference handbook procedures, discharged both fire bottles, and shutdown the No. 2 engine. The airplane made an uneventful single engine landing at DAY and was met by aircraft rescue and firefighting (ARFF) vehicles on the runway. ARFF crews determined the fire had been extinguished and the airplane was cleared to taxi to the gate under its own power. The flight was a regularly scheduled flight from Orlando Sanford International Airport (SFB), Sanford, Florida to DAY and was conducted under the provisions of 14 Code of Federal Regulations Part 121. There were no reported passenger or crew injuries.


Allegiant Air maintenance crews performed a visual inspection of the No. 2 engine at DAY and reported significant thermal damage on the bottom half of the engine, concentrated around the constant speed drive (CSD) and generator. A section of the generator case was fractured and missing. The CSD-to-oil cooler return line located adjacent to the generator was severed. Oil pooling and metal debris were observed at the 6 o' clock position in the engine cowling.


Constant Speed Drive and Generator Examination and Disassembly

The digital flight data recorder (DFDR) engine parameters and photographs of the engine provided by maintenance personnel on scene at DAY were reviewed and it was determined that the failure was isolated to the No. 2 engine CSD or generator. Both components were removed from the engine and shipped to United Technologies Aerospace Systems in Rockford, Illinois for examination and disassembly.

The CSD was disassembled and fine metal debris was observed throughout the case, on all internal components and on the magnetic oil plug. The CSD gears and bearings were intact and the gear train could be manually rotated with some resistance.

The center section of the generator frame case was fragmented and missing. All generator rotating components exhibited severe thermal damage and deformation. The generator main rotor copper holding wedges, V-shaped steel wedges, and copper windings were separated. Several small copper holding wedge fragments were recovered from the generator case, but the parts were too damaged to perform materials analysis.


A record of uncontained generator failures on Douglas Aircraft DC-9/ McDonnell Douglas MD-80 series airplanes was requested from UTC Aerospace Systems and Boeing. Eleven prior uncontained generator failure events were reported since the year 2000. The event descriptions for each of the prior 11 events were based on crew statements, and from the statements an accurate count of generator failures that resulted in an engine fire was inconclusive. It was confirmed that none of the events to date have resulted in an uncontrolled fire.

Following the events in 2010, Boeing provided the NTSB with a safety risk assessment. According to the assessment, any fragments released by an uncontained generator failure are low energy projectiles and do not pose a threat to the airframe. The assessment also states that design features including overboard drains, fire detection and extinguishing systems are in place to mitigate the risks associated with flammable fluid leaks in a designated fire zone.

In June 2005 Hamilton Sundstrand Corporation (now UTC Aerospace Systems) released service information letter (SIL) 449 recommending that air cooled generator rotors installed on Boeing 707, 727, 737, DC9, MD80, and DC10 airplanes should be overhauled and re-wound at 40,000 operating hours. As part of the overhaul, the interpole copper wedges are replaced. Boeing released a service letter, DC9-SL-24-104/MD-80-SL-24-104 in November 2005 notifying all operators of the SIL. 

Aircraft and Owner/Operator Information

Aircraft Manufacturer: DOUGLAS
Registration: N881GA
Model/Series: DC 9 83 83
Aircraft Category: Airplane
Year of Manufacture: 1988
Amateur Built: No
Airworthiness Certificate: Transport
Serial Number: 49708
Landing Gear Type: Retractable - Tricycle
Date/Type of Last Inspection:
Certified Max Gross Wt.:
Time Since Last Inspection:
Engines: 2 Turbo Fan
Airframe Total Time:
Engine Manufacturer: Pratt & Whitney
ELT: Installed, not activated
Engine Model/Series: JT8D-200
Rated Power:
Operator: Allegiant Air
Operating Certificate(s) Held:  Flag carrier (121) 

Meteorological Information and Flight Plan

Conditions at Accident Site: Unknown
Condition of Light: Day
Observation Facility, Elevation:
Observation Time: 1100 EDT
Distance from Accident Site:
Direction from Accident Site:
Lowest Cloud Condition:
Temperature/Dew Point:
Lowest Ceiling:
Wind Speed/Gusts, Direction:
Visibility (RVR):
Altimeter Setting:
Visibility (RVV):
Precipitation and Obscuration:
Departure Point: ORLANDO, FL (SFB)
Type of Flight Plan Filed:  Unknown
Destination: Dayton, OH (DAY)
Type of Clearance: Unknown
Departure Time:
Type of Airspace: Unknown

Airport Information

Runway Surface Type:  N/A
Airport Elevation: 1009 ft
Runway Surface Condition: Unknown
Runway Used: N/A
IFR Approach: Unknown
Runway Length/Width:
VFR Approach/Landing:  Unknown 

Wreckage and Impact Information

Crew Injuries: 6 None
Aircraft Damage: None
Passenger Injuries: 157 None
Aircraft Fire: In-Flight
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 163 None
Latitude, Longitude:  39.902500, -84.221944 (est)

NTSB Identification: ENG17IA017
Scheduled 14 CFR Part 121: Air Carrier operation of Allegiant Air
Incident occurred Sunday, March 19, 2017 in Dayton, OH
Aircraft: DOUGLAS DC 9 83, registration: N881GA
Injuries: 163 Uninjured.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft incident report.

At about 1211 eastern daylight time, a McDonnell Douglas MD-83, N881GA, operated by Allegiant Air experienced a No. 2 engine fire during approach to Dayton International Airport (DAY)- Dayton, Ohio. The crew completed the emergency checklist, shut down the No. 2 engine, and discharged both fire bottles. The airplane made an uneventful single engine landing at DAY and was met by emergency response vehicles on the runway. It was determined that the fire had been extinguished and the airplane taxied to the gate under its own power. No injuries were reported to the passengers or crew. The flight was being operated in accordance with 14 Code of Federal Regulations Part 121 and was a regularly scheduled flight from Orlando International Airport (MCO)- Orlando, Florida to DAY.

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