<div id="readability-page-1"><div>[SINGAPORE] The fatal SQ321 Singapore Airlines (SIA) flight in May 2024 may have flown into severe turbulence after the jet’s weather radar possibly failed to display a rapidly forming storm cloud, said Singapore’s transport safety regulator.Released on Tuesday (May 19), the Transport Safety Investigation Bureau’s (TSIB) final report concluded that it “cannot be ruled out” that the Boeing 777’s radar failed to paint a storm cell or issue fault warnings.Such an issue could have left pilots completely unaware of severe vertical drafts from a quickly forming cumulonimbus cloud, a type of storm cloud.While the TSIB declined to name the weather radar system’s manufacturer, previous media reports indicated that the aircraft may have used a Honeywell radar. SIA, Boeing and Honeywell did not immediately respond to requests for comment regarding the findings.The incident, which left one passenger dead and 56 seriously injured, highlights a systemic vulnerability where intermittent radar failures go undetected. Because aviation weather radars struggle to depict certain moisture-lacking vertical clouds, a blank display does not immediately signal a malfunction, which can create a false sense of safety, an active US airline pilot told The Business Times.<h2>Surprised despite preparation</h2>The pilot-in-command of Flight SQ321 had his radar sensitivity – or “gain” – turned to its maximum setting. Sharing the cockpit with him was another captain, who was the augmenting pilot on the flight, and had his radar display set to “auto”. Following the turbulence encounter, the cockpit voice recorder captured the pilot-in-command saying: “I was on MAX... I don’t see anything here”.The crew’s situational awareness may have been further stretched by their display scales; the report noted that both navigation screens were set to a long-range 320-nautical-mile view. Such a macro setting can compress and obscure rapidly closing, localised threats.Four other nearby aircraft, using different radar models at varying altitudes, successfully detected weather ahead and sidestepped it. While satellite data and these flights indicated widespread cloud coverage, the SQ321 crew maintained that their immediate path was clear.“The investigation team is unable to understand why the flight crew of the occurrence flight did not see the widespread clouds,” the report stated.Flight data showed the encountered cloud grew vertically at 1,200 feet per minute, reaching cruising altitude faster than the equipment could paint the threat.The resulting turbulence was severe: despite being pitched 5 degrees nose-down, the Boeing 777 was forced upward at over 2,000 feet per minute. SIA and Boeing independently calculated that the jet hit a massive updraft of roughly 9,000 feet per minute.This external force triggered a catastrophic sequence inside the cabin. In just over half a second, passengers went from experiencing a 1.35G force – 1.35 times the normal force of gravity – to a negative 1.5G, unseating unbuckled passengers and flinging them, crew members and cabin objects into the ceiling as the aircraft dropped about 180 feet (54 m).An active widebody pilot, speaking on the condition of anonymity, told The Business Times that he has not encountered a localised updraft of that speed in the year he has been flying. Most of his flights have had enough warning for pilots to tell cabin crew and passengers to be seated, he added.<h2>Weather radar functionality disputed</h2>As indicated by the TSIB report, maintenance records showed that 0.36 per cent of SIA’s Boeing 777 flights between May 2023 and July 2025 logged radar issues, including 20 cases of completely blank screens amid inclement weather. SQ321’s specific aircraft logged a similar “no-painting” fault just six days prior to the incident.Post-incident testing yielded differing conclusions. The equipment manufacturer found “no evidence” that the hardware failed to detect weather during the flight.TSIB, maintaining reservations about the manufacturer’s conclusions, also noted unusual behaviour during testing, including erratic antenna scanning at extremely cold temperatures and unexplained display anomalies. Noting the limitations of recreating high-altitude freezing conditions in a test facility, TSIB stated that standard ground tests were insufficient to rule out an intermittent radar failure.Honeywell’s RDR-4000 radar line, also likely used on the SQ321 aircraft in question, has faced recent European regulatory scrutiny over identical “under-painting” vulnerabilities. A 2025 report from Germany’s aircraft investigators said Honeywell and Airbus identified severe software and hardware anomalies within the system that cause an “undetected loss of weather display” completely hidden from onboard automated fault alerts. System glitches were found to misclassify and erase genuine weather returns from cockpit displays, forcing manufacturers to formally alter flight manuals to warn crews of late radar detections beyond 80 nautical miles. <h2>Safety actions recommended</h2>SIA has since overhauled pilot weather radar training and integrated predictive applications such as the so-called SkyPath.TSIB has also urged Boeing to upgrade maintenance manuals, noting standard ground tests fail to replicate cruising altitude conditions. It also recommended that radar manufacturers develop image-recording for weather displays to help diagnose “under-painting” issues.Boeing and Honeywell have 90 days to respond. Regulators, including the Civil Aviation Authority of Singapore and the US Federal Aviation Administration, will also review findings to determine if mandatory airworthiness directives are required.<h2>Compensation and liability</h2>The findings will likely feature in ongoing passenger compensation claims. Under the Montreal Convention, airlines are strictly liable for injuries up to US$170,000, though courts can award higher damages if claimants prove the carrier failed to take reasonable precautions.SIA initially offered US$10,000 to passengers with minor injuries and US$25,000 advance payments for serious injuries. However, a group of passengers sued SIA in the UK High Court on May 6, pursuing elevated damages for severe spinal injuries.TSIB’s conclusion of a potential silent hardware issue could now shift liability dynamics in these cases from the airline to equipment manufacturers.The 2024 incident follows previous regional encounters. In October 2011, an older SIA Boeing 777 experienced severe turbulence over Vietnam, injuring 21 after the crew encountered drafts just outside the radar’s moisture-detection limits.These limitations are compounded by changing weather patterns. Following a 2022 incident, TSIB noted that a warming atmosphere is contributing to rapidly developing storms that challenge traditional forecast models. Combined with intermittent radar faults, this narrows the window for crews to take evasive action, the US pilot said.</div></div>

The final report on the SQ321 Singapore Airlines flight indicates a possible radar failure may have left pilots unaware of severe turbulence, resulting in one death and 56 injuries. The Transport Safety Investigation Bureau noted that the Boeing 777's radar might not have detected a rapidly forming storm cloud. The report highlights systemic vulnerabilities in aviation weather radars and calls for improved training and maintenance protocols. SIA has since revamped pilot training and integrated predictive applications to enhance safety.

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SQ321 final report: Possible radar issue may have left SIA pilots blind to severe turbulence