United B39M at Denver on Sep 30th 2023, rejected takeoff due to engine fire

Last Update: February 27, 2025 / 10:31:32 GMT/Zulu time

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Incident Facts

Date of incident
Sep 30, 2023

Classification
Accident

Airline
United

Flight number
UA-329

Departure
Denver, United States

Destination
Boston, United States

Aircraft Registration
N37560

Aircraft Type
Boeing 737-900MAX

ICAO Type Designator
B39M

A United Boeing 737-9 MAX, registration N37560 performing flight UA-329 from Denver,CO to Boston,MA (USA) with 167 passengers and 6 crew, was accelerating for takeoff from Denver's runway 16R when the crew rejected takeoff at high speed, in response to the radio transmission tower reported he could see fire from the left hand engine (LEAP). The crew affirmed and stopped the aircraft, subsequently reporting it appeared they had flat tyres on the right hand side and were disabled. The runway was closed, emergency services responded, tower cleared the crew to evacuate if needed stating "the runway is yours!" While emergency services were responding but had not yet reached the runway tower informed emergency services that they no longer observed any fire, it appears extinguished.

The FAA reported: "AIRCRAFT ON DEPARTURE ROLL, ABORTED TAKEOFF DUE TO SMOKE AND FIRE UNDER RIGHT WING AND ARFF EXTINGUISHED FIRE, DENVER, CO." providing the aircraft tail number of the replacement aircraft registration N37541.

Pictorial evidence shows fire damage to the right hand side of the aircraft, all four main tyres blown, the right hand main wheel rims abraded.

A replacement Boeing 737-9 MAX registration N37541 reached Boston with a delay of about 5 hours.

On Feb 26th 2025 the NTSB released their final report reporting the aircraft sustained substantial damage and concluding the probable cause of the accident was:

Overheated brakes due to the extended taxi at a higher power setting in an attempt to burn off fuel to achieve the proper takeoff weight that resulted in a wheel fire during takeoff.

The NTSB analysed:

United Airlines flight 329 conducted a rejected takeoff after experiencing abnormal acceleration while on Runway 16R at Denver International Airport (DEN), Denver, Colorado. The flight was a regularly scheduled passenger flight to Boston Logan International Airport (BOS), Boston, Massachusetts. As a result of a subsequent brake fire following the rejected take off, the aircraft suffered substantial damage. No injuries were reported.

The flight crew reported that before the flight, the captain and the first officer (FO) met to review the flight plan, maintenance documents, weather, and Notice to Airmen (NOTAMS). It was then that the captain noticed that the airplane had just come out of maintenance. The flight crew reported that the airplane would be close to maximum takeoff weight, and that the temperature would be high, and the flight would be taking off on runway 16R. Airport operations made runway 16R the designated runway for departures that day since it is the longest runway at DEN, with a length of 16,000 feet.

Once the flight crew were onboard the airplane they reviewed the takeoff performance data where they noticed that the planned takeoff weight was more than what would be allowed for a takeoff from runway 16R. The weight at the gate was 172,800 lbs. but needed to be below 171,700 lbs. for a safe takeoff, taking into consideration the atmospheric conditions at the time. The captain reported making a call to dispatch where he spoke with a different dispatcher than the one who had created the original flight plan. The original flight plan had been created using a lower temperature of 29 Celsius which had been correct at the time, but the temperature had since risen to 31 Celsius.

The new dispatcher sent 3 flight plan revisions. The flight crew reported that the first revision removed 1,000 lbs. of cargo, but did not remove enough weight to be within limits, and a second flight plan revision was requested. The second revision removed another 1000 lbs. by removing 8 passengers. The flight crew mentioned to dispatch that there was about 1000 lbs. of extra fuel onboard that could be burned off with an extended taxi, and dispatch sent a new revision to the flight plan that required an extended taxi to burn off the 1,000 lbs. of excess fuel to reduce the takeoff weight instead of removing passengers.

The flight crew reported experiencing a normal pushback before preforming a “long slow” taxi to the runway with the power elevated while applying additional braking to burn more fuel.

Once reaching the runway, the flight held there for an additional 10 to 15 minutes with the parking brake set to burn the additional fuel. The pilots reported that they never had any indication that the brakes were getting hot, and the Boeing 737 has no brake temperature monitoring system to inform the flight crew of brake temperatures. The flight crew commented that every other Boeing aircraft they have flown had a brake temperature monitoring system.

Once below the required weight requirement, the flight crew notified Air Traffic Control (ATC) and were subsequently cleared for takeoff.

The captain was the pilot flying and reported quickly noticing the aircraft not accelerating normally during the takeoff roll. He immediately rejected the takeoff and the FO informed tower. The tower then observed and notified the flight crew that there was smoke and fire on the right side of the airplane. The flight crew had no indication of fire in the cockpit. The captain then requested Aircraft Rescue and Fire Fighting (ARFF) and declared an emergency with ATC.

ARFF fought the fire by releasing fire retardant on both main gear while the FO ran through the rejected takeoff checklist.

The captain coordinated with the flight attendants to ensure the safety of all passengers. The captain reported making multiple public announcements (PA) to the passengers to inform them of the situation.

After all appropriate checklists were complete, the captain decided against immediate evacuation based on communications with ARFF and the passengers disembarked via the air stairs that were provided by airport operations. The passengers were then driven back to the passenger terminal in buses.

Postaccident investigation of the airplane revealed that the No. 1 and 2 tires had deflated. Number 3 and 4 tires had separated from the wheel assembly and there was evidence that tire fragments had impacted the airframe in several areas. The number 3 wheel assembly scraped the runway and had ground down with about 1/3 of the assembly missing, the number 4 wheel assembly was ground down to about half, and the number 2 engine nacelle had scraped the runway. In addition, several panels of the wing to body (WTB) fairing panels had suffered heat DCA23LA468 Page 2 of 7damage and tire debris was imbedded in the inner face of the engine inlet inner barrel acoustic panel. The right horizontal stabilizer also received structural damage.
Aircraft Registration Data
Registration mark
N37560
Country of Registration
United States
Date of Registration
NqAl lgqAcAc Subscribe to unlock
Manufacturer
BOEING
Aircraft Model / Type
737-9
Number of Seats
Fl Subscribe to unlock
ICAO Aircraft Type
B39M
Year of Manufacture
Jcpl Subscribe to unlock
Serial Number
Eilqn Subscribe to unlock
Aircraft Address / Mode S Code (HEX)
Pjqlgd Subscribe to unlock
Engine Count
M Subscribe to unlock
Engine Manufacturer
Lkfglbg Subscribe to unlock
Engine Model
NAdcpbihnAqhh Subscribe to unlock
Engine Type
Emjhnbjc Subscribe to unlock
Pounds of Thrust
Mlmkh Subscribe to unlock
Main Owner
BbnkAbAdeib qh iil jefecchlb iffkebmlefpgqnncAclbiknpqlgggqdepmhkcphgbAi Subscribe to unlock
Incident Facts

Date of incident
Sep 30, 2023

Classification
Accident

Airline
United

Flight number
UA-329

Departure
Denver, United States

Destination
Boston, United States

Aircraft Registration
N37560

Aircraft Type
Boeing 737-900MAX

ICAO Type Designator
B39M

This article is published under license from Avherald.com. © of text by Avherald.com.
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