United Airlines flight 2477 departed taxiway SC while turning off of runway 27 at high speed after landing at George Bush Houston Intercontinental Airport (IAH), Houston, Texas. As flight 2477 departed the paved taxiway, the left main landing gear impacted a concrete structure recessed in the ground adjacent to taxiway SC. This impact resulted in separation of the left main landing gear. Postaccident examination of the airplane found nothing anomalous that precluded normal operation of the landing gear and the wheel braking system. Furthermore, the flight crew reported no anomalous operation of the autobrake system, the speedbrake system, or the thrust reversers during the landing rollout. The captain stated, and the flight data recorder (FDR) data confirmed, that he retracted the speedbrakes about 6 seconds after landing in order to turn off the autobrakes. Additionally, only engine idle reverse thrust was used after touchdown. By not using maximum reverse thrust upon touchdown and by turning off the autobrakes shortly after landing, the captain failed to follow multiple company standard operating procedures (SOPs) that would have assured deceleration of the airplane. The captain delayed application of maximum manual wheel braking after turning off the autobrakes, and the airplane remained at high speed as it neared the end of the runway. Speedbrake deployment increases wing aerodynamic drag and reduces wing aerodynamic lift, thereby slowing the airplane and increasing main landing gear wheel loading for more effective wheel braking. By stowing the speedbrakes shortly after landing, the wheel brakes were less effective in decelerating the airplane when the captain eventually applied maximum manual wheel braking. Had the captain used timely and effective manual wheel braking with the speedbrakes deployed, the airplane would have been capable of decelerating to a safe taxi speed before exiting the runway. The flight crew did not conduct a thorough briefing of the airplane’s landing performance when the captain changed the autobrake setting from 2 to 1, which decreased the target deceleration rate for the autobrake system. Furthermore, the flight crew did not effectively discuss potential threats, such as the wet runway condition, and appropriate threat mitigations in an arrival briefing. When the captain changed the autobrake setting to 1, the first officer (FO) accepted this deviation from the established autobrake SOP without further discussion, missing an opportunity to exhibit good crew resource management by discussing potential risks associated with this action. Lastly, a thorough arrival briefing could have identified and reminded the flight crew of a paved blast pad within the normal runway safety area (RSA) at the end of runway 27. This blast pad and RSA infrastructure provided an opportunity to decelerate to a safe taxi speed for full stop on paved and non-paved, obstacle-free surfaces instead of attempting to turn onto taxiway SC at high speed.
The captain's decision not to establish and maintain deceleration devices in accordance with company training and standard operating procedures.
Honeywell HFR5-D FDR · N27290 — 190,671 samples, 119 parameters, 07:50:59.5 to 08:01:31.5.
| Parameter | Max | at | Min | at | Final | at |
|---|---|---|---|---|---|---|
| Computed airspeed kts | 252.0 | 07:51:57.1 | 45.0 | 07:58:18.8 | 45.0 | 08:01:31.3 |
| Pitch attitude deg | 6.3 | 07:58:32.3 | -2.3 | 07:58:29.3 | 5.4 | 08:01:31.3 |
| Roll attitude deg | 8.3 | 07:58:36.0 | -28.7 | 07:52:15.5 | 7.9 | 08:01:31.3 |
| Vertical acceleration g | 1.6 | 07:58:31.6 | 0.5 | 07:58:31.2 | 1.0 | 08:01:31.5 |
| Engine 1 N1 %RPM | 58.6 | 07:50:59.7 | 5.5 | 08:01:30.7 | 5.5 | 08:01:30.7 |
| Engine 2 N1 %RPM | 58.6 | 07:54:03.2 | 8.5 | 08:01:31.2 | 8.5 | 08:01:31.2 |
| Time | Event | Page |
|---|---|---|
| 06:37:23 CST | The aircraft departed on runway 18R from Memphis International Airport (KMEM), Memphis, Tennessee. The takeoff, climb, cruise, and approach were uneventful. | 6 |
| 07:51:56 CST | AP Glideslope Arm was ARMED. | 6 |
| 07:52:08 CST | AP Localizer Engaged was ENGAGED. | 6 |
| 07:52:54 CST | Radio altitude was 2017 ft, computed airspeed was 230 kts, magnetic heading was 263 deg. The flap handle was moved to 1 deg. | 6 |
| 07:54:22 CST | Computed airspeed was 210 kts. The flap handle was moved from 1 deg to 5 deg. | 6 |
| 07:54:27 CST | Computed airspeed was 206 kts. The flap handle was moved from 5 deg to 10 deg. | 6 |
| 07:54:38 CST | The Speedbrake Lever was moved to the ARMED position. | 6 |
| 07:55:09 CST | AP Glideslope Engaged was ENGAGED. | 6 |
| 07:55:16 CST | Auto brake switch-2 changed from ACTIVE to NOT ACTIVE. Auto brake switch-1 changed from NOT ACTIVE to ACTIVE. The aircraft radio altitude began to descend from 2000 ft. | 6 |
| 07:55:32 CST | The Gear Lever Up and Gear Lever Down parameters changed from UP to NOT UP and the Gear Lever Down changed from NOT DN to DOWN. | 6 |
| 07:55:37 CST | Computed airspeed was 174 kts. The flap handle was moved from 10 deg to 15 deg. | 6 |
| 07:55:50 CST | Radio altitude was 1477 ft, computed airspeed was 171 kts, magnetic heading was 262 deg. The flap handle was moved from 15 deg to 25 deg. | 7 |
| 07:55:55 CST | Computed airspeed was 169 kts. The flap handle was moved from 25 deg to 30 deg. The glideslope and localizer deviation were both -0.02 dots. | 7 |
| 07:56:49 CST | Radio altitude was 620 ft, and computed airspeed was 153 kts. The autopilot was disengaged. | 7 |
| 07:57:34.4 CST | The left outer wheel speed was TRUE (that is, greater than 60 kts). | 7 |
| 07:57:34.7 CST | Both the left inner and outer wheel speeds were TRUE. The Auto Spd Brk Extend Cmd transitioned from "NOT EXTEND" to "EXTEND." The Speedbrake Handle began to transition from the ARMED condition. | 7 |
| 07:57:35.7 CST | The Speedbrake Handle was in the FULL UP position. The air/ground relay switch changed from AIR to GND. Groundspeed was 157 kts (153 kts computed airspeed). | 7 |
| 07:57:36.7 CST | Auto Brakes Applied were ON. | 7 |
| 07:57:39.6 CST | Engine 1 thrust reverser was FULLY DEPLOYED. | 7 |
| 07:57:40.0 CST | Engine 2 thrust reverser was FULLY DEPLOYED. | 7 |
| 07:57:40.7 CST | The Speedbrake Handle began to transition from the FULL UP to DWN+LCKED position. Groundspeed was 140 kts and decreasing. | 7 |
| 07:57:41.7 CST | Auto Brakes Applied changed from ON to OFF. The Speedbrake Handle was in the DWN+LCKED position. Groundspeed was 137 kts. | 7 |
| 07:57:53.7 CST | Main brake pressure began to increase on both gears. | 7 |
| 07:58:06.4 CST | Engine 2 thrust reverser was NOT DEPLOYED. | 7 |
| 07:58:07.1 CST | Engine 1 thrust reverser was NOT DEPLOYED. Groundspeed was 84 kts. | 7 |
| 07:58:18.2 CST | The left main brake pressure reached a maximum value of 2318 psi. The groundspeed was 48 kts and decreasing. | 7 |
| 07:58:18.3 CST | Groundspeed was 47 kts and decreasing. Magnetic heading began to increase from 267 deg. | 7 |
| 07:58:21.6 CST | Groundspeed was 34 kts and decreasing. Magnetic heading was 272 deg and increasing. | 8 |
| 07:58:25.0 CST | Main brake pressure on both gears spiked to approximately 1500 psi. The groundspeed was 26 kts and magnetic heading was 292 deg. | 8 |
| 07:58:35.8 CST | Groundspeed was 0 kts. Magnetic heading was 338 deg. | 8 |
| 07:58:48 CST | The master caution was activated and was active for 1 second, inactive for a half second, and then active again for a half second. | 8 |
| 08:00:21 CST | The APU was powered ON. | 8 |
| 08:01:14 CST | Engine 1 fuel was CUTOFF. | 8 |
| 08:01:21 CST | Engine 2 fuel was CUTOFF. | 8 |
| 08:21:09 CST | End of valid recorded data. | 8 |
651 transcribed utterances from 05:56:20.1 to 08:31:12.5, 14 sources. Final entries:
| 08:31:07.0 | HOT-1 | terminal. |
| 08:31:08.1 | HOT-1 | yeah. |
| 08:31:10.1 | HOT-1 | so call maintenance. |
| 08:31:12.5 | END | OF ACCIDENT FLIGHT RECORDING COCKPIT VOICE RECORDER DCA24FA120 |
| 08:31:12.5 | GROUP | CHAIR'S FACTUAL REPORT PG 80 OF 80 |
Docket: data.ntsb.gov/Docket/?NTSBNumber=DCA24FA120. This brief is an analytical aid assembled from public records; it is not an investigative finding.