- Date
- December 12, 2017, 07:35 local (12:35 UTC)
- Place
- Detroit, MI
- Injuries
- 61 uninjured
- Damage
- Substantial damage
- Phase of flight
- Standing
- Aircraft
- N924DLMcdonnell Douglas MD 88
- Defining event
- Standing: Ground handling event
- Weather
- Visual (VMC) · Day
- Status
- Completed · report July 8, 2020
- Report
- Approved by Office Director
- NTSB office
- Major Investigations Division
- Lead agency
- Other
- Case key
- 96468
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Probable cause
failure of the flight crew to confirm the left engine throttle lever was at idle during engine start.
Findings · 1
NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.
Sequence of events
The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.
Analysis
On December 12, 2017, about 0735 EST, Delta flight 2421, Boeing McDonnell Douglas MD-88, N924DL, after being pushed back from the gate, with the towbar still connected, was substantially damaged after the airplane moved forward after engine start and struck the tug at Detroit Metropolitan Airport (DTW), Detroit, Michigan. There were no injuries to the 61 passengers and crew onboard. The flight was operating under 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight from DTW to Raleigh-Durham International Airport (RDU), Morrisville, North Carolina. During pushback, the tug driver informed the flight crew they were cleared to start. After the left engine was started, the airplane started to unexpectedly move forward. Both flight crew members were focused inside the cockpit, running checklists, when the tug driver asked if the brake was set on the airplane. The captain responded "no" and the first officer then noticed the position of the tug and told the captain that they needed to stop the airplane. The airplane struck the tug before stopping. After the airplane's brake was set, the flight crew noticed that the engine throttles were not at idle as expected. Ground conditions were reported as slippery. The tug struck the right forward lower fuselage causing damage to the pressure vessel (skin, stringers, and frames).
Factual narrative
On December 12, 2017, about 0735 EST, Delta flight 2421, Boeing McDonnell Douglas MD-88, N924DL, after being pushed back from the gate, with the towbar still connected, was substantially damaged after the airplane moved forward after engine start and struck the tug at Detroit Metropolitan Airport (DTW), Detroit, Michigan. There were no injuries to the 61 passengers and crew onboard. The flight was operating under 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight from DTW to Raleigh-Durham International Airport (RDU), Morrisville, North Carolina. During pushback, the tug driver informed the flight crew they were cleared to start. After the left engine was started, the airplane started to unexpectedly move forward. Both flight crew members were focused inside the cockpit, running checklists, when the tug driver asked if the brake was set on the airplane. The captain responded "no" and the first officer then noticed the position of the tug and told the captain that they needed to stop the airplane. The airplane struck the tug before stopping. After the airplane's brake was set, the flight crew noticed that the engine throttles were not at idle as expected. Ground conditions were reported as slippery. The tug struck the right forward lower fuselage causing damage to the pressure vessel (skin, stringers, and frames).
Aircraft
- Registration
- N924DL
- Reported as
- Mcdonnell Douglas MD 88 (88)
- Category
- Airplane
- Serial number
- 49711
- Built
- 1988
- Airframe hours
- 74,998
- Engines
- Pratt and Whitney JT8D-219, turbo jetPratt and Whitney JT8D-219, turbo jet
- Damage
- Substantial damage
- Flight
- Part 121
- Operator
- Delta Air Lines
- Registered owner
- Delta Air Lines Inc
- Airworthiness certificate
- Standard, Transport
- Last inspection
- December 11, 2017
- Departed
- DTW · Detriot, MI
- Destination
- RDU · Raleigh/Durham, NC
- Flight plan
- IFR
- Airport
- DTW · Detroit Metropolitan Wayne Cou
- Equipment
- Electronic primary flight display, Onboard weather, Stall warning system, Angle of attack indicator, Data recorder, Electronic multifunction display
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 320° at 14 knots, gusting 24
- Visibility
- 8 statute miles
- Temperature
- 23 °F, dew point 9 °F
- Altimeter
- 29.80 inHg
- Observed at
- KDTW
Docket · 3
The files NTSB released with the investigation on October 9, 2020, on NTSB’s docket system: statements, records, photos and specialists’ reports. 1.1 MB in all.
Other investigations on N924DL · 2
Matched to the same aircraft by N-number and date.