Trans/Rhoades B732 at Honolulu on Jul 2nd 2021, ditched about 2nm out of Honolulu
Last Update: June 16, 2023 / 16:07:49 GMT/Zulu time
Incident Facts
Date of incident
Jul 2, 2021
Classification
Accident
Airline
Transair
Flight number
T4-810
Departure
Honolulu, United States
Destination
Kahului, United States
Aircraft Registration
N810TA
Aircraft Type
Boeing 737-200
ICAO Type Designator
B732
ATC further informed rescue services that they had lost communication with the aircraft, the aircraft had lost an engine, no further information was known to ATC.
The FAA confirmed the aircraft developed engine trouble and needed to land in the water while attempting to return to Honolulu.
The coast guard reported the aircraft ditched in the waters about 2nm short of Kalaeloa Airport. Both crew were taken to Queens Medical Center, their condition however is unknown.
On Jul 3rd 2021 Coast Guard men involved in the rescue reported the debris field of the aircraft was about 1.25nm long. They discovered both pilots, one (58) was standing at the tail of the aircraft waving at the helicopter, the other clinged to a cargo net of cargo swimming around the aircraft. When the aircraft sank, the one pilot at the tail momentarily disappeared, they got sight of him again while he was struggeling to stay afloat and lifted him into the helicopter at 02:58L. The pilot was exhausted and unable to talk, but was conscious. The other pilot (50) was rescued by a boat at 02:51L, the pilot had head injuries and needed to be cleaned from aircraft fuel before he walked off the boat on his own and was received by medical staff who took him to the hospital.
The NTSB have opened an investigation into the accident stating: "NTSB sending team of 7 investigators for investigation of Friday's crash of a Transair Boeing 737-200 cargo airplane in the waters off the island of Oahu near Honolulu." The NTSB subsequently added, a total of 10 investigators is being dispatched to Honolulu.
The hospital reported one of the pilots (58) is in the intense care unit in critical condition, the other (50) received serious head injuries and multiple lacerations and is in serious condition. On Jul 6th 2021 the pilot (50) could be released from hospital care.
On Jul 6th 2021 the NTSB reported that small amounts of debris were recovered from the water surface. Sonar scans are being conducted to locate the FDR and CVR.
On Jul 10th 2021 the NTSB released photos of the aircraft wreckage at the sea floor before Honolulu.
On Nov 2nd 2021 the NTSB reported that both FDR and CVR as well as the major aircraft components have been recovered from the sea floor about 350-450 feet below the water surface.
On Dec 20th 2022 the NTSB released their investigation docket.
The power plant group's factual report stated that the engines were maintained in compliance with the relevant Airworthiness Directives and had shown no anomaly prior to the accident flight. With respect to an Engine Health Monitoring post maintenance report on Oct 30th 2019 the NTSB stated:
"The raw EHM data were submitted to P&W for review. P&W reported that the No. 1 engine EGT averaged 18F higher than the No. 2 EGT, and that, for most flights, both engines had operated slightly below, but close to, the engine manual cruise limit of 977F."
The report also stated that the fuel sample taken from the fuel truck, that had fueled the accident aircraft for its last flight was in compliance with all specifications.
The power plant group annotated with respect to Engine #1: "The low rotor was seized. Static borescope inspection of the C3 and C4 blades at six evenly spaced locations showed full-length C3 and C4 blades with no obvious distortion. There appeared to be 360° clash damage to the C4 and C5 stator TEs."
Engine #2 showed two blades (#1 and #6) fractured about 2.5 inches above their platforms in the high pressure turbine (T1). Those blades were sent for metallurgic tests. The metallurgy report concluded: "It was determined that the most probable failure mode was internal oxidation/corrosion that led to the loss of load-bearing cross section, resulting in stress rupture fracture. It was inconclusive which of the two blades failed first."
The aircraft performance group reported: "Based on performance data consistent with data used to develop the Airplane Flight Manual (AFM), the B737-200 ADV has adequate performance capability with one engine inoperative (OEI) to climb or maintain altitude for the accident airplane loading and flight conditions. In addition, subsequent to the right engine rapid EPR reduction, with no change to the left engine EPR, the accident airplane demonstrated the ability to climb to 1,000 feet, accelerate, climb to 2,000 feet, and maintain altitude. When left engine EPR reduced and remained below 1.2, the total airplane engine thrust was less than the thrust required for the airplane to maintain altitude over the recorded range of flight conditions, flight control inputs, left and right engine EPR values, and flap configurations encountered. Finally, the accident aircraft motion, in response to gear/flap configuration changes, flight control inputs, and engine EPR changes, was generally consistent with the behavior of the nominal B737-200 ADV integrated airplane/engine/flight controls simulation model."
The flight data recorder group summarized their findings:
In the accident flight, the engines were advanced to takeoff power starting at 01:33:08 HST, and both stabilized at an EPR consistent with takeoff. Engine 1 (the left engine) was at 2.00 EPR and engine 2 (the right engine) was at 1.97 EPR. Longitudinal acceleration peaked at 0.2055 g during the takeoff roll. The aircraft rotated at about 140 knots and took off on a heading of 80 degrees.
As the aircraft passed through about 390 ft at 155 knots, engine 2 EPR suddenly dropped to 1.43, while engine 1 remained at its previously set takeoff power. Immediately after engine 2 EPR dropped, the rudder pedal moved to about 5.5 degrees of left rudder, consistent with a command to counteract the adverse yaw of losing thrust on the right engine. The climb paused at 1,000 feet for 25 seconds, then continued to 2,000 ft.
At 2,000 feet, engine 1 EPR reduced to a value of 1.051, which is consistent with idle power in previous flights. It stayed at this value for the remainder of the flight.
Engine 2 EPR also reduced at 2,000 feet, however it continued to be advanced and reduced several times until the end of the flight.
Altitude and airspeed decreased over the next 9 minutes until the end of the recording. At the end of the recording, engine 2 EPR was 1.462 and engine 1 EPR, having been stable since it reduced at 2,000 feet, was still consistent with previous flight idle settings at 1.052.
On Jun 16th 2023 the NTSB released their final report concluding the probable cause of the accident was:
The flight crewmembers’ misidentification of the damaged engine (after leveling off the airplane and reducing thrust) and their use of only the damaged engine for thrust during the remainder of the flight, resulting in an unintentional descent and forced ditching in the Pacific Ocean. Contributing to the accident were the flight crew’s ineffective crew resource management, high workload, and stress.
The NTSB analysed:
The captain first declared an emergency to the controller about 36 seconds after the CVR recorded the thud sound; he also advised the controller to stand by. The controller responded with a routine departure clearance; thus, the controller likely did not hear or understand the captain’s transmission. About 7 seconds later, the captain again declared an emergency and advised the controller to stand by. During the 30 seconds that followed, the captain reminded the first officer to fly the airplane on a heading of 220° and level off at 2,000 ft.
The controller again provided routine instructions to the flight crew about 33 seconds after the captain’s second transmission about the emergency. The captain then declared an emergency (for the third time) and stated that the airplane lost an engine and was on a 220° heading. The controller responded, “say again heading two four zero.” Immediately after issuing this instruction, the controller informed the captain that the heading was intended for another airplane. The captain did not hear, understand, or remember this transmission because he later instructed the first officer to fly the airplane on a 240° heading.
The controller then cleared the accident airplane for a visual approach to the airport, and the captain informed the controller that he and the first officer had to perform a checklist and would let her know when they were ready to return to the airport. The controller then asked the captain to keep her advised.
The process of declaring the emergency to ATC took 1 minute 53 seconds. During a postaccident interview, the captain stated that his communications with the controller “became a project” and that “it took a while for ATC to know what was going on” regarding the emergency. The captain added that those communications “took too much of [his] time away from the cockpit.” Although frequency congestion impeded the captain’s efforts to declare an emergency to ATC, the captain could have entered squawk code 7700 (indicating an emergency situation) into the transponder and deferred further radio communications until after the first officer stabilized the airplane in level flight.
In addition, about 25 seconds after the previous exchange between the controller and captain ended, the controller asked for more information about the emergency, including which engine was affected. The operator’s simulator guide stated that, after declaring an emergency involving a single-engine failure after V1, the captain could provide additional information to ATC when time permitted. Because further communication with ATC was not a priority at that time, the captain responded appropriately to the controller by stating that he would provide the information later.
The simulator guide also stated that, after declaring an emergency to ATC, selecting flaps to the UP position, reducing thrust, and establishing the airplane’s climb at 210 knots, the pilot flying was to fly, navigate, and communicate, and the pilot monitoring was to “reconfirm” the failure. However, much of the captain’s time by this point in the flight was spent listening and responding to ATC transmissions. Thus, communications between the captain and controller after the onset of the emergency caused interruptions that delayed the flight crew’s efforts to address the emergency situation.
While the captain was communicating with the controller, the first officer, as the pilot flying, incrementally reduced left and then right engine thrust to near flight idle so that the airplane could slow down after leveling off. The first officer stated that he had been trained in the simulator to move the thrust levers together until the crew was ready to confirm the affected engine. Thus, the first officer’s decision to independently move the left and then the right thrust lever was inappropriate.
When the captain turned his attention back to the airplane after communicating with the controller, both engines were near flight idle (the EPR was 1.05 and 1.12 for the left and right engine, respectively), and the airspeed was 227 knots and decreasing. The captain commanded a speed of 220 knots and then announced that he was taking control of the airplane. FDR data indicated that the captain did not promptly increase thrust after the airspeed subsequently dropped below the 220-knot target speed. During a postaccident interview, the captain stated that he was unaware that the first officer had reduced left engine thrust to near flight idle. The captain’s lack of awareness of the first officer’s thrust reductions played a role in his handling of the in-flight emergency, as discussed in the next section.
Misidentification of the Affected Engine and Failure to Verify
About 4 minutes elapsed between the time of the flight crew’s correct identification of the right engine as the affected engine and the first officer’s incorrect assessment about the left engine. This amount of time played a role in the first officer’s misidentification of the left engine as the affected engine. The first officer had a high workload during that time; as the pilot flying, he had to (among other things) closely monitor basic flight parameters and fly the airplane to achieve the target airspeed, altitude, and heading. The first officer was also dealing with interruptions due to the interspersing of various operational tasks.
Although the first officer had previously verbalized that the right engine had lost power, the first officer’s workload demands left few opportunities for him to commit that information to memory. In addition, after the airplane had leveled off and the left and right EPR had been reduced to near flight idle, no adverse yaw (the primary cue indicating that the right engine was affected) was occurring, and the engine indications were ambiguous because both were producing low thrust (with the EPR on the left and right engines at 1.05 and 1.12, respectively).
Although thrust was low on both engines, the first officer might have thought that the left engine was affected because its EPR level was lower than that for the right engine. For that to be the case, the first officer would have had to have forgotten his earlier actions of pulling back the power on the left (operational) engine and then the right (damaged) engine to reduce airspeed.
The National Transportation Safety Board (NTSB) considered whether the first officer’s use of prescription medications played a role in (1) forgetting his and the captain’s initial correct diagnosis and his movement of the left thrust lever (along with the right thrust lever) to reduce airspeed and (2) asserting erroneously that the left engine was the affected engine. The NTSB's analysis of the potential side effects of these medications found that the use of these medications likely did not play a role in the accident.
The NTSB also considered whether the first officer’s errors were due to fatigue. Even though the errors that the first officer made were consistent with the effects of fatigue, the evidence supporting fatigue was inconclusive. Stress is also known to degrade cognitive functions such as working memory, attention, and reasoning, and it provides an alternate explanation for the first officer’s actions. The loss of right engine thrust at a low altitude over the ocean at night was a surprising and stressful event, especially for the first officer as the pilot flying at the time of the engine event.
The captain initially questioned the first officer’s assessment, stating “number one is gone?”, but then accepted the assessment and stated, “so we have number two.” At that time, no salient cue was available to indicate which engine was affected (due to the reduced thrust on both engines and the lack of adverse yaw). During a postaccident interview, the captain remembered his initial assessment that the right engine was affected but stated that he had assumed that the first officer had a better understanding of the engines’ status because he was flying the airplane when the captain was communicating the emergency to ATC.
The captain had confidence in the first officer’s assessment of the affected engine based on their flight experience together; during a postaccident interview, the captain stated that the first officer “never makes a mistake.” Nevertheless, the captain did not take any action to verify the first officer’s assessment about the left engine, such as advancing the thrust lever for the left engine to determine whether an increase in thrust occurred. The operator’s simulator guide stated that pilots should be alert for changes indicating that thrust was being reduced on the incorrect (operational) engine. However, the crew did not notice the reduction in adverse yaw that resulted from the first officer’s reduction of thrust on the left engine. Subsequently, the reductions in thrust on the left and right engines (which the first officer made to reduce airspeed) meant that there would be no noticeable indications that would have reinforced the idea to the crewmembers that the left engine was affected, as they determined initially.
If the captain had thought to test the thrust on the left engine by advancing the left thrust lever, the flight crew would likely have noticed an increase in left engine thrust, a yaw to the right, and engine sounds indicating that the left engine was capable of producing normal power. The captain could also have simultaneously advanced both thrust levers and observed the left engine producing more thrust. However, neither flight crewmember suggested that the captain perform these actions, and neither of these potential diagnostic steps was included in the operator’s Engine Failure or Shutdown checklist.
Further, the Engine Failure and Shutdown checklist would not have helped the captain sort out the situation because the checklist appeared to assume that the airplane would be experiencing ongoing asymmetric thrust, which was not the case at this point in the accident flight. The checklist did not consider the possibility that a flight crew would need to delay checklist execution until after completing steps in an operator’s single-engine departure procedure, such as leveling off at a low altitude and reducing thrust on both engines. Because there was no longer a clear sign of which engine had failed and the crew had forgotten its earlier determination that the right engine had lost power, critical thinking was required for the crew to devise diagnostic steps to confirm the affected engine. However, each pilot’s thinking was degraded by high workload and stress.
Rhoades Aviation Inc. trades as Transair operating 5 Boeing 737.
Metars Kalaeloa Airport:
PHJR 021253Z AUTO 08007KT 10SM BKN049 26/18 A3004 RMK AO2 SLP177 T02560178 TSNO=
PHJR 021153Z AUTO VRB04KT 10SM FEW038 OVC050 26/19 A3004 RMK AO2 SLP179 T02560189 10261 20250 57008 TSNO=
PHJR 021053Z AUTO VRB04KT 10SM BKN048 25/18 A3005 RMK AO2 SLP181 T02500183 TSNO=
PHJR 020953Z AUTO 07007KT 10SM CLR 25/18 A3006 RMK AO2 SLP185 T02500178 403170217 TSNO=
PHJR 020853Z AUTO 08004KT 10SM FEW039 OVC048 26/19 A3007 RMK AO2 SLP187 T02610189 51007 TSNO=
PHJR 020753Z 07005KT 10SM OVC050 26/19 A3007 RMK AO2 SLP187 T02610189=
Metars Honlulu International Airport:
PHNL 021253Z 07010KT 10SM FEW024 FEW046 26/17 A3002 RMK AO2 SLP166 T02560167=
PHNL 021153Z 06010G21KT 10SM FEW025 SCT050 26/17 A3003 RMK AO2 SLP169 60000 T02560172 10267 20256 56008=
PHNL 021053Z 07013KT 10SM FEW025 SCT045 26/18 A3004 RMK AO2 SLP170 T02560183=
PHNL 020953Z 06009KT 10SM FEW025 SCT050 26/18 A3005 RMK AO2 SLP175 T02560178 403110244=
PHNL 020853Z 09014G20KT 10SM FEW025 BKN050 26/17 A3006 RMK AO2 RAB09E17 SLP177 P0000 60000 T02610172 50008=
Aircraft Registration Data
Incident Facts
Date of incident
Jul 2, 2021
Classification
Accident
Airline
Transair
Flight number
T4-810
Departure
Honolulu, United States
Destination
Kahului, United States
Aircraft Registration
N810TA
Aircraft Type
Boeing 737-200
ICAO Type Designator
B732
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This article is published under license from Avherald.com. © of text by Avherald.com.
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