In An Emergency, Trust But Verify, Part 2
The complete loss of a large transport airplane like a Boeing 737 usually brings out the NTSB in force. That was the case with Transair 810.
The initial NTSB headquarters Search and Recovery team arrived in Honolulu the day of the accident and got started promptly. The team made arrangements to find and recover the wreckage. The Operations and Human Performance and Air Traffic groups arrived the next day. Other groups formed later.
A crash of this type could have been a major (Class 1) investigation, but it was eventually rated as Class 2. Even though major resources were deployed, there were no fatalities, and the NTSB found no reason to write any recommendations. No “sunshine” board meeting was held.
One of the first orders of business was to interview the pilots and the air traffic controllers involved in the accident. The two pilots had sustained injuries but were released from the hospital and were interviewed on July 5 and 6, 2021, days after the accident. It was important to talk to them while their memories were fresh.
Among the first questions for the flight crew, an investigator asked the captain which engine indications he had seen besides the EPR after the failure. “I didn’t get a chance to scrutinize those gauges,” the captain replied. He said he asked the FO what the EGT readings were. Even though he was the pilot monitoring throughout the takeoff and climb, the captain did not try to look at and analyze what the engine instruments were telling him.
“If Greg (the FO) tells you the sky is blue, don't look at the sky—it’s blue,” the captain said. “That is how much I trust Greg.”
When investigators asked the FO to describe the event, he did not hesitate. “Before the 400-ft. call, after the gear came up we lost the Number 1 engine,” he said. “[I] heard a pop and it went still and all the gauges on the left side—the Number 1—just dropped.”
Then the FO seemed less certain. “I thought I knew it was the left engine except the airplane yawed to the, to the right, which shouldn’t have been the case and that may just be I stepped on the rudder or something,” he said. “I don’t know.”
Then came the Freudian slip. “No, I think we—once we agreed it was the right engine—nothing changed after that,” the FO said. “I’m sorry; it was the right engine that was still running is what I …” He caught himself and said it was the right rudder he was pressing to compensate for yaw. His story didn’t make sense and he knew it.
After the initial launch and data collection effort, there was a hiatus while the airplane wreckage, including the recorders, were found and recovered. The aft fuselage was located on July 7. The next day, the rest of the wreckage was found, lying at depths between 354 ft.-437 ft. Wreckage recovery operations began on October 12 and concluded on Nov. 2, 2021.
The captain, 58, had an estimated 15,781 flight hr., with 871 in the Boeing 737-200. He had a Class 1 medical certificate but was required to wear glasses during flight. He was wearing them. He had worked for seven airlines before coming to Transair in 2019. He liked working for Transair and preferred to pick up extra flying on his days off.
He had flown on each of the three days before the accident, each night reporting at 0015 and finishing duty at 0730, 1202 and 0723, respectively, on June 29, 30 and July 1, 2021. On those three days he had flown a total of 20 flights. He remarked that daytime rest was often difficult to get as a result of noise from dogs, sirens, neighbors, and grass cutting using a weed whacker.
The captain said he had experienced five engine failures and seven precautionary or emergency landings in the two years he had worked for the company. After one engine failure, Transair’s chief pilot had criticized him for returning to the airport without performing the relevant abnormal checklist. He had promised to run the checklist if it happened again.
The FO was 50 years old. He had an Airline Transport certificate, was type rated in the Boeing 737, and had a Class 2 medical certificate with a limitation that he must wear corrective lenses, which he was wearing. He estimated his total flying time to be 5,272 hr., 908 of which were in the Boeing 737-200. He had flown for Mesa Airlines from 1991-95 before resigning and going to law school.
The FO was an attorney and had his own law office in Honolulu. He had not flown for 24 years when he decided to take a job with Transair. He had been there for two years, during which time he had not experienced any engine failures. He continued to work at his legal office during the day when he had the time. He felt his sleep pattern was good and he was rested before the accident flight.
The Aircraft And Engine
The Boeing 737-275C was manufactured in 1975 and had accumulated 72,871 total hours and 69,446 total cycles before the accident flight. The two Pratt & Whitney JT8D-9A turbofan engines had been installed in 2019. The left engine, manufactured in 1971, had accumulated 32,305 total hours and 33,670 total cycles. The right engine was manufactured on Jan. 10, 1968, and had accumulated 70,827 total hours and 101,368 total cycles.
The FDR and CVR were recovered in October 2021. The FDR only had 18 parameters and thrust lever position and engine indications other than engine pressure ratio were not included. The two-hour CVR was intact and a full transcript was made.
An NTSB performance engineer and a Boeing performance study confirmed that the 737 had performed properly in accordance with its design. A powerplant study of the right engine showed the outer spans of two high-pressure turbine stage 1 blades were missing. Blade Nos. 1 and 6 were fractured transversely about 2.4 and 2.7 in., respectively, above the platform trailing edge. The blades failed by stress rupture resulting from a loss of load-bearing material due to oxidation and corrosion.
While operator Rhoades Aviation had been subject to several Letters of Investigation from the FAA, the NTSB found that maintenance was not a factor in the accident.
Conclusions of the accident investigation and our comments follow in Part 3 of this article.
In An Emergency, Trust But Verify, Part 1, https://aviationweek.com/business-aviation/safety-ops-regulation/emerge…