McDonnell Douglas MD-81 – LN-RMT

Incident Overview

Date: Saturday 21 July 2001

Aircraft Type: McDonnell Douglas MD-81

Owner/operator: SAS Scandinavian Airlines

Registration Number: LN-RMT

Location: 55 km W of Helsinki – ÿ Finland

Phase of Flight: En route

Status: Substantial, repaired

Casualties: Fatalities: 0 / Occupants: 69

Component Affected: Aircraft WindshieldAircraft Windshield

Investigating Agency: SIAFSIAF

Category: Accident

On October 14, 2014, an MD-81 aircraft experienced a serious incident during a flight over Finland. The aircraft was climbing to cruising altitude, FL 290, and encountered severe turbulence and hailstones due to a cumulonimbus cloud (CB) at an airspeed of 303 knots. The aircraft was issued a clearance to descend to flight level 100 and subsequently handed over to radar control. The pilots, while attempting to use the airborne weather radar, encountered a malfunctioning radar image that showed only an error code. The aircraft’s windshield cracked, and the co-pilot?s windshield also cracked. The aircraft then sent a distress message, indicating the presence of cracked windshields and requesting vectors. The APP controller instructed the crew to turn right to heading 070 and continue descent to 2000 feet. The aircraft landed on runway 22. The probable cause was inadequate en-route weather preparation and a failure to adequately assess the weather conditions, leading to the pilots’ failure to utilize the airborne radar effectively. Recommendations include improved weather preparation procedures and the development of a system for monitoring rapidly developing weather phenomena and issuing timely warning messages.On October 14, 2014, an MD-81 aircraft experienced a serious incident during a flight over Finland. The aircraft was climbing to cruising altitude, FL 290, and encountered severe turbulence and hailstones due to a cumulonimbus cloud (CB) at an airspeed of 303 knots. The aircraft was issued a clearance to descend to flight level 100 and subsequently handed over to radar control. The pilots, while attempting to use the airborne weather radar, encountered a malfunctioning radar image that showed only an error code. The aircraft’s windshield cracked, and the co-pilot?s windshield also cracked. The aircraft then sent a distress message, indicating the presence of cracked windshields and requesting vectors. The APP controller instructed the crew to turn right to heading 070 and continue descent to 2000 feet. The aircraft landed on runway 22. The probable cause was inadequate en-route weather preparation and a failure to adequately assess the weather conditions, leading to the pilots’ failure to utilize the airborne radar effectively. Recommendations include improved weather preparation procedures and the development of a system for monitoring rapidly developing weather phenomena and issuing timely warning messages.

Description

The pilots used the airborne weather radar during the climb, but it was switched off 10 minutes after take-off. The plane climbed to the cruising level, FL 290. The cruise part of the flight was flown above clouds in clear weather, and flight visibility forwards was unrestricted. Tampere area control centre (ACC) cleared SAS1700 to descend to flight level 100, and thereafter handed the aircraft over to Helsinki approach radar (APP) from reporting point LAKUT. SAS1700 contacted the APP controller at 17:05 and the aircraft was issued an arrival clearance. While descending in a cumulonimbus cloud (CB) through flight level 152, with the indi-cated airspeed (IAS) of 303 knots (kt) the MD-81 flew into a powerful cell which contained turbulence and large hailstones. There was also thunder in the CB cloud. The co-pilot tried to switch on the weather radar on the captain’s request, but a radar image could not be obtained. The device only showed an error code. The windshield in front of the captain was cracked, and a moment later also the windshield on the co-pilot’s side. At 14.10.14 the APP controller gave the MD-81 crew a heading of 060deg and cleared it to continue descent to 5000 feet. At 14.10:58 SAS1700 sent a distress message: “Mayday, Mayday, Mayday, we?re having cracked windshields here and request vectors”. The APP controller instructed SAS1700 to turn right to heading 070deg and cleared it to continue descent to 2000 feet, which the crew acknowledged. At 14.19 the aircraft landed on runway 22. PROBABLE CAUSE: “SAS1700 flight preparation was partly inadequate in respect of en-route weather, and the pilots did not form a correct picture of the weather conditions in flight so that the air-borne weather radar would have been used to avoid the CB cloud. A contributing factor was that the warning message on significant weather (SIGMET) was prepared too late considering the development of weather conditions.” It was recommended that SAS should take appropriate actions to ensure that the pilots pay sufficient attention to weather conditions during flight preparation and in flight, and make efficient use of airborne weather radar. Also, the Finnish Meteorological Institute should consider creating a system to facilitate the monitoring of rapidly developing weather phenomena and preparation of warning messages on significant weather.

Source of Information

https://turvallisuustutkinta.fi/fi/index/tutkintaselostukset/ilmailuonnettomuuksientutkinta/tutkintaselostuksetvuosittain/ilmailu2001/b52001lraekuurovauriohelsinginlansipuole.htmlhttps://turvallisuustutkinta.fi/fi/index/tutkintaselostukset/ilmailuonnettomuuksientutkinta/tutkintaselostuksetvuosittain/ilmailu2001/b52001lraekuurovauriohelsinginlansipuole.html

Primary Cause

Inadequate en-route weather preparation and a failure to adequately assess the weather conditions, leading to the pilots’ failure to utilize the airborne weather radar effectively.Inadequate en-route weather preparation and a failure to adequately assess the weather conditions, leading to the pilots’ failure to utilize the airborne weather radar effectively.

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