NLM Cityhopper Flight 431

__NOTOC__Infobox Airliner accident|name=NLM Cityhopper Flight 431
Date=October 6 1981
Type=Extreme midair turbulence and wind shear (Climb phase)
Site=near Moerdijk, North Brabant, Netherlands
Fatalities=17
Injuries=0
Aircraft Type=Fokker F28 Fellowship 4000
Operator=Nederlandse Luchtvaart Maatschappij (NLM Cityhopper)
Tail Number=PH-CHI 11141
Passengers=13
Crew=4
Survivors=0
Ground=4

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", respectively, for a total loading of 10 "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. Among the passengers, nine were Dutch, two were British, and one was American.

The disintegrating airliner was seen exiting cloud cover. 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.

The plane crashed near a Royal Dutch Shell chemical factory in an industrial complex on the southeast outskirts of Moerdijk. One person on the ground, an emergency responder, died of a heart attack.

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.

Aircraft details

*Airline: NLM Cityhopper (now KLM Cityhopper)
*Aircraft type: Civilian, Passenger
*Flight nature: Domestic scheduled passenger
*Aircraft model: Fokker F28-4000
*Registration Number of Aircraft: PH-CHI 11141 (October 19, 1979)
*Model service: 14 years (1967)
*Aircraft service: 2 years
*Total airframe airtime: 4485 hrs; 5997 cycles
*Engines: 2x Rolls-Royce RB183 "Spey" Mk555 turbofan engines
*Max. cruising speed: 843 km/h (523 mph; 454 knots)
*Range: 1 900 km (1 180 mi)
*Max. take off weight: 33 110 kg (73 000 lb)
*Wing span: 25.07 m (82 ft 3 in)
*Length: 29.61 m (97 ft 2 in)
*Service ceiling: 10 675 m (35 000 ft)
*From: Rotterdam Airport (RTM / EHRD), Rotterdam, South Holland, Netherlands
*Destination: Eindhoven Airport (EIN / EHEH), Eindhoven, North Brabant, Netherlands

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.

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.

External links

* [http://aviation-safety.net/database/record.php?id=19811006-0 Aviation Safety Network accident listing]
* [http://planecrashinfo.com/1981/1981-51.htm Accident details] at [http://www.planecrashinfo.com/ planecrashinfo.com]

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.