NLM Cityhopper Flight 431

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NLM Cityhopper Flight 431
Summary
Date   October 6, 1981
Type   Extreme midair turbulence and wind shear (cruise phase)
Site   near Moerdijk, North Brabant, Netherlands
Fatalities   17
Injuries   0
Aircraft
Aircraft type   Fokker F28 Fellowship 4000
Operator   Nederlandse Luchtvaart Maatschappij (NLM Cityhopper)
Tail number   PH-CHI 11141
Passengers   13
Crew   4
Survivors   0

NLM Cityhopper Flight 431 was a short range passenger flight departing Rotterdam Airport (RTM) in Rotterdam, South Holland, Netherlands, scheduled for arrival at Eindhoven Airport (EIN) in Eindhoven, North Brabant, Netherlands, late on the afternoon of Tuesday, October 6, 1981. Eindhoven was a stopover before final arrival at Hamburg Airport (HAM) in Hamburg, Germany.

The Fokker F28 Fellowship 4000 jet took off at 5:04 p.m. CET (UTC +1). At 5:09 p.m., the crew noted heavy rain in thunderstorms on the weather avoidance radar and received clearance to avoid the area. At 5:12 p.m. the aircraft entered a tornado whilst flying through clouds. The stress resulted in loads increasing to +6.8 g and -3.2 g. The right wing separated, there was in-flight breakup, and the aircraft crashed out of control from 3000 ft (900 m) near Moerdijk in the southwestern Netherlands. Flight 431 went down 15 miles (24 km) south-southeast of Rotterdam, killing all 17 aboard.

The disintegrating airliner was seen exiting cloudcover. A police officer first photographed the tornado, then smoke from the burning plane a few minutes later. An investigation concluded that a sharp increase in altitude registered on the altimeter was not a change in altitude, rather a pressure drop associated with the tornado.

[edit] Airline changes

NLM Cityhopper was acquired by Koninklijke Luchtvaart Maatschappij (KLM), or Royal Dutch Airlines, in 1990 and became the KLM Cityhopper division in 1991. NLM Cityhopper began as NLM (Nederlandse Luchtvaart Maatschappij) Dutch Airlines in 1966 and changed to NLM Cityhopper in 1976.

[edit] Aircraft details

[edit] Weather

During the weather briefing 44 minutes before takeoff, the crew was apprised to an area of strong thunderstorms with 3/8 (37.5%) sky coverage of cumulonimbus at a base of 1200 feet (365 m), winds 210° at 15 - 25 knots (17 - 29 mph; 28 - 46 km/h), and 5 kilometres (3.1 mi) visibility at Rotterdam Airport.

[edit] Turbulence

The ICAO turbulence definitions, including the supplementary g loading – positive or negative, relative to the normal 1 g load, are:

  • Very low – below 0.05 g – Light oscillations
  • Low – 0.05 to 0.2 g – Choppy; slight, rapid, rhythmic bumps or cobblestoning
  • Moderate – 0.2 to 0.5 g – Strong intermittent jolts
  • Severe – 0.5 to 1.5 g – Aircraft handling made difficult
  • Very severe – above 1.5 g – Increasing handling difficulty, structural damage possible.

[edit] External links

[edit] References

  • Grazulis, Thomas P. (2001). The Tornado: Nature's Ultimate Windstorm. University of Oklahoma Press: Norman, OK. pp 260-1. ISBN 0-8061-3258-2
  • Roach, W.T., and J. Findalter (1983). "An Aircraft Encounter with a Tornado". Meteorological Magazine (Meteorological Office, London) 112 (February): 1327, pp 29-49.
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