United B38M at Houston on Mar 8th 2024, runway excursion and main gear collapse
Last Update: April 5, 2024 / 10:02:24 GMT/Zulu time
Incident Facts
Date of incident
Mar 8, 2024
Classification
Accident
Airline
United
Flight number
UA-2477
Departure
Memphis, United States
Destination
Houston Intercontinental, United States
Aircraft Registration
N27290
Aircraft Type
Boeing 737-800MAX
ICAO Type Designator
B38M
Airport ICAO Code
KIAH
A passenger reported the aircraft had landed normally and in normal attitude, when the crew attempted to turn off the aircraft was too fast, skidded, the gear collapsed and the aircraft went off onto soft ground. The passenger disembarked onto the runway via stairs.
The FAA stated: "After landing at George Bush Intercontinental Airport in Houston, United Airlines Flight 2477 rolled onto the grass when exiting onto the taxiway around 8 a.m. local time on Friday, March 8. The passengers deplaned on the taxiway and were bused to the terminal. The Boeing 737 departed from Memphis International Airport. Please contact the airline for additional information. The FAA will investigate. "
The NTSB announced they have dispatched an investigation team to Houston to investigate the runway excursion of a United Boeing 737 at Houston's Intercontinental Airport.
On Apr 5th 2024 the NTSB released their preliminary report summarizing the sequence of events:
According to the flight crew, the captain (61, ATPL, 15,191 hours total, 9,607 hours on type) was the pilot flying and the first officer (FO) (38, ATPL, 1,252 hours on type) was the pilot monitoring. The captain said he observed the reported runway surface condition codes when checking the automatic terminal information system (ATIS) via his electronic flight bag (EFB). For runway 26L and 26R, he recalled seeing codes of 3/3/3 and for runway 27 codes of 5/5/5. The actual runway surface condition codes being broadcasted on the ATIS for runway 27 at the time were 3/3/3 which according to the runway condition assessment matrix (RCAM) indicated the runway was slippery when wet and “braking deceleration is noticeably reduced for the wheel braking effort applied or directional control is noticeably reduced.”
When the crew checked in with Houston Approach Control, they were told to expect a landing on runway 26L. The captain asked the FO to request a landing on runway 27 instead. The FO made, and the controller approved the request and issued instructions for the instrument landing system (ILS) approach to runway 27. After checking in with Houston Tower (about 12,000 feet msl according to the FO), the captain asked the FO to request approval to roll to the end of runway 27. The FO made the request. A tower controller approved it and instructed them, “keep your speed up”. The captain changed the autobrake setting from 2 to 1 (which would command a reduced deceleration rate). The approach was conducted in instrument meteorological conditions (IMC) and, according to the crew, the airplane broke out of the clouds between 800 and 1,000 feet msl. They reported that visibility under the clouds was good, and the captain recalled that the runway appeared dry. The FO recalled that the runway appeared wet.
The crew stated that the touchdown was uneventful, at an appropriate speed, and within the touchdown zone. The speed brakes extended normally, and the thrust reversers were deployed to idle reverse thrust. The captain said that, shortly after touchdown, he retracted the speedbrakes by the action of moving the speedbrake lever to its down and locked position, which disabled the autobrakes. He did not “slow too much initially” because the runway appeared dry, he wanted to expedite their time on the runway, and because he preferred decelerating gradually for passenger comfort.
The captain said he applied the brakes manually using the toe brakes at about 6,000 feet from the end of the runway but felt as if the deceleration was less than normal. DFDR data and automatic dependent surveillance-broadcast (ADS-B) data indicated that after the disabling of the autobrakes occurred, manual braking did not begin until the airplane was about 4,000 feet from the end of the runway. The captain recalled hearing the runway awareness and advisory system (RAAS) alert indicating 1,000 ft of runway distance remaining. He became concerned and began applying more pressure to the brakes. As he approached the end of the runway, he elected to attempt to turn onto taxiway SC, by utilizing the steering tiller and rudder pedals while pushing aggressively on the brake pedals.
During the turn onto the taxiway, he felt the fuselage and rudder/brake pedals begin to shake violently. He briefly released the brake pressure and the shaking ceased. He then reapplied aggressive brake pressure and the shaking resumed. The airplane slid off the runway and the left MLG tires and nose wheels tires entered the grass before the airplane came to a rest with its left wing low.
A postaccident examination of the accident site revealed that the left MLG tires had impacted a large concrete “manhole” designed as an electrical junction box for lights/utilities at the airport. As a result of the impact, the left MLG separated from the airplane at the fuse pins near the rear spar as designed to prevent more severe damage to surrounding structures. The airplane came to rest on the left engine nacelle, left winglet, and aft fuselage and sustained substantial damage to the left wing and aft fuselage.
...
Data from the DFDR was sent to the NTSB’s Vehicle Recorder Laboratory in Washington, DC, for analysis. A preliminary review of data has been completed and a plot showing the braking parameters is shown in figure 3. Data showed that at touchdown the speed brake lever position [Speed Brake Lever Pos] and auto brake parameters were full up and on for about 5 seconds before transitioning to down and locked and off for the remainder of the landing rollout.
The engine thrust reversers were deployed for the left and right engines for about 27 and 26 seconds respectively at idle reverse. The left and right brake pressure increased to their maximum pressure consistent with aggressive manual braking before and as the airplane’s heading changed consistent with a right turn.
...
Certified ADS-B data, which records more accurate latitude and longitude data than the DFDR, was provided to the NTSB by the FAA. Analysis of the ADS-B and DFDR data shows that the airplane touched down about 1,000 feet from the runway threshold with a groundspeed of about 158 knots. With about 1,000 ft and 500 ft of runway remaining the airplane groundspeeds were about 72 kts and 57 kts respectively. The right turn to exit the runway was initiated at about 39 kts groundspeed and the aircraft departed the end of the paved surface at about 22 kts.
Related NOTAM:
!IAH 03/099 IAH RWY 09/27 CLSD 2403081532-2403231300
Metars:
KIAH 081453Z 16005KT 1 1/2SM BR BKN008 OVC020 23/22 A2972 RMK AO2 SLP063 60002 T02280222 51014=
KIAH 081353Z 19005KT 1 1/2SM BR BKN008 OVC018 23/22 A2971 RMK AO2 SFC VIS 2 1/2 SLP059 T02280217=
KIAH 081311Z 17004KT 2 1/2SM BR BKN008 OVC015 23/22 A2970 RMK AO2 T02280217=
KIAH 081253Z 17003KT 2 1/2SM BR BKN010 BKN021 OVC030 22/22 A2970 RMK AO2 SFC VIS 4 RAE30 SLP056 P0002 T02220217=
KIAH 081246Z 17003KT 2 1/2SM BR BKN010 BKN021 OVC030 22/22 A2969 RMK AO2 SFC VIS 4 RAE30 P0002 T02220217=
KIAH 081153Z 14003KT 2 1/2SM -RA BR OVC008 22/22 A2968 RMK AO2 SFC VIS 4 RAE1058B14 SLP049 P0004 60004 70006 T02220217 10228 20211 53001 $=
KIAH 081053Z 00000KT 7SM -RA BKN006 OVC011 23/22 A2966 RMK AO2 RAB48 SLP044 P0000 T02280217 $=
KIAH 080953Z 16008KT 7SM BKN007 OVC012 22/21 A2967 RMK AO2 SLP046 T02220211 $=
Aircraft Registration Data
Incident Facts
Date of incident
Mar 8, 2024
Classification
Accident
Airline
United
Flight number
UA-2477
Departure
Memphis, United States
Destination
Houston Intercontinental, United States
Aircraft Registration
N27290
Aircraft Type
Boeing 737-800MAX
ICAO Type Designator
B38M
Airport ICAO Code
KIAH
This article is published under license from Avherald.com. © of text by Avherald.com.
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