Narrative: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.
|Date:||21 JUL 2001|
|Type:||McDonnell Douglas MD-81|
|Operator:||Scandinavian Airlines System - SAS|
|C/n / msn:|| 53001/1815|
|First flight:|| 1991|
|Total airframe hrs:||23673|
|Engines:|| 2 Pratt & Whitney JT8D-217C|
|Crew:||Fatalities: 0 / Occupants: 6|
|Passengers:||Fatalities: 0 / Occupants: 63|
|Total:||Fatalities: 0 / Occupants: 69 |
|Airplane damage:|| Substantial|
|Airplane fate:|| Repaired|
|Location:||55 km (34.4 mls) W of Helsinki (Finland)
|Phase:|| Unknown (UNK)|
|Nature:||International Scheduled Passenger|
|Departure airport:||Stockholm-Arlanda Airport (ARN/ESSA), Sweden|
|Destination airport:||Helsinki-Vantaa Airport (HEL/EFHK), Finland|
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."
Follow-up / safety actions
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.
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not
display the exact flight path.
Distance from Stockholm-Arlanda Airport to Helsinki-Vantaa Airport as the crow flies is 396 km (247 miles).