On July 2, 2021 a Part 121 cargo flight experienced a partial loss of power shortly after takeoff, leading to a forced ditching in the Pacific Ocean. The NTSB final report found that the crew’s ineffective resource management, high workload and stress contributed to the accident, as well as the misidentification of the damaged engine and subsequent use of only that engine for thrust the remainder of the flight, rather than the other working engine.
Rhoades Aviation flight 810, a Boeing 737 (N810TA) took off from the Daniel K. Inouye Airport (HNL) in Honolulu, Hawaii and was ditched in Mamala Bay in the Pacific Ocean 11.5 minutes later, 5.5 miles southwest of HNL. The Captain sustained serious injuries, the first officer sustained minor injuries and the airplane was destroyed. The final report analyzed the right engine’s partial loss of power, the captain’s communications with ATC, the first officer’s left and right engine thrust reductions, the first officer’s misidentification of the damaged engine and the captain’s failure to verify the information, and the survival factors. The NTSB said the maintenance was not a factor in the accident.
Shortly after flight 810 took off from HNL the CVR recorded a “thud” and the sound of a low-frequency vibration. The captain and first officer also reported hearing a “whoosh” and “pop” noise respectively. The plane climbed to an altitude of 390 feet with an airspeed of 155 knots and the right engine pressure radio decreased before the plane yawed to the right. The first officer countered the yaw with the appropriate left rudder pedal inputs and the CVR determined that the captain and first officer then correctly determined that the right engine had lost thrust within five seconds of hearing the thud sound.
The flaps were moved to the UP position and the captain reduced thrust to maximum continuous thrust, causing the left EPR to decrease while the plane was in a climb. The captain reported that he did not move the thrust levers again until after he became the flying pilot. The first officer reportedly reduced the thrust on both engines after the plane leveled off at an altitude of 2,000 feet. The captain was unaware of the recent thrust changes as he was contacting the controller about the ensuing emergency. He told ATC they had lost an engine, but he had declared an emergency twice before, first about 36 seconds after the CVR recorded the thud sound and the second about seven seconds later.
After the captain took control he asked who had the exhaust gas temperature, and the officer stated the left engine was “gone” and “we have number two” (the right engine) which was a misidentification of the damaged engine. The captain did not verify the first officer’s assessment and the EPR level on the right engine began to increase since the captain was advancing the right thrust lever so the plane could maintain airspeed and altitude. The right engine EGT fluctuated many times during the remainder of the flight while the left EPR remained near flight idle.
The crew chose to remain within 15 miles of the airport. The captain told the NTSB in his interview that because there was no fire and the engine appeared to be running, he planned to keep the plane at 2,000 feet and stay within 15 miles of the airport to avoid traffic and make time to address the engine issue. The captain also claimed that he had previously been criticized by the company chief pilot for returning to an airport without completing the required abnormal checklist for a different in-flight emergency. The NTSB found this decision, while resulting in the crew flying farther from the airport and over the ocean at night, was reasonable for a single-engine failure event.
The captain remained at the radios and the first officer was instructed to begin the Engine Failure or Shutdown checklist. While reading the checklist out loud, the first officer stopped to tell the captain the right EGT was at the red line and that thrust should be reduced on the right engine. The captain then decided to return to the airport and contacted the controller to request vectors.
The crew continued showing concern over the right engine, with the first officer telling the captain the EGT was “beyond max” when he was asked to check. The first officer continued reading the checklist out loud but then stopped, stating “We have to fly the airplane though,” and the crew stopped the checklist, not performing key steps like identifying, confirming and shutting down the affected engine.
The plane was losing altitude and the captain told the controller “We’ve lost number one (left) engine…there’s a chance we’re gonna lose the other engine too it’s running very hot…we’re pretty low on the speed it doesn’t look good out here.”
The captain told the controller to contact the U.S. Coast Guard since he was anticipating water ditching. The first officer was relaying messages to the controller as the captain was trying to control the plane. CVR recorded a sound similar to a “stick shaker” which continued throughout the rest of the flight and then recorded sounds consistent with a water impact. The crew evacuated out the window and they both found floating pieces of the plane or cargo materials to float on while waiting for rescue while the plane sank.
The postaccident examination revealed that the right engine had been rotating at a much faster speed at impact than the left engine, consistent with the engine operating at near flight idle. The teardown of the right engine revealed that two high-pressure turbine stage 1 blades were missing their outer spans and both had failed from a stress rupture fracture due to oxidation and corrosion of the internal blade lightening holes, which then resulted in a loss of load-bearing cross-section. The blade failures caused secondary damage to the low-pressure turbine which resulted in a loss of thrust. This would have presented to the flight crew as the decrease in EPR in the right engine and the recorded thud sound and subsequent yaw to the right.
A large factor that led to the ocean ditching was the misidentification of the affected engine and the failure to verify. Roughly four minutes passed between the flight crew’s correct identification of the right engine as the affected engine and the first officer’s incorrect assessment of the left engine. The report noted that the first officer had a high workload at that time and he had to closely monitor the basic flight parameters and fly the plane to achieve the target airspeed, altitude and heading, while dealing with interruptions due to interspersing of different operational tasks. While he had previously confirmed the right engine as the damaged engine, his workload may have impeded his ability to commit the information to memory.
The NTSB investigators found that stress may have been a factor in the first officer forgetting the affected engine and misidentifying it, not only due to his excessive workload, but the shock and stress of the loss o engine thrust at low altitude over the ocean at night. Upon hearing the first officer’s assessment the captain asked, “Number one is gone?” but accepted and stated “So we have number two,” but since he trusted the first officer’s judgment and knowledge of the engines, he did not question it again. If he had thought to test the thrust on the left engine, they likely would have noticed the increase in thrust indicated normal power. However, neither thought to perform this diagnostic step, which was included in the abandoned checklist.
The engine checklist, had it been completed promptly, might have helped the crew determine the misidentification and fixed the thrust problem.
The report indicated that the thinking of both the captain and first officer was degraded by the high workload and stress. In addition, a lack of awareness prevented the captain from catching the left engine thrust level and verifying the first officer’s assessment. The stress before the event was compounded by the stress of the partial engine failure, further impeding the crew’s response.
Despite “chronic maintenance writeups” for the accident plane, the examination did not find that maintenance is what led to the ocean ditching. The NTSB found that it was the misidentification of the damaged engine which led to the unintentional descent and ditching. Other factors, like workload, stress and resource management heavily contributed to the crash.