Swissair flight 306

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Swissair flight 306
SR Caravelle.jpg

A sister aircraft of the accident HB-ICV
Accident summary
Accident type Crash due to control failure
place Dürrenäsch
date 4th September 1963
Fatalities 80
Survivors 0
Aircraft
Aircraft type Sud Aviation Caravelle III
operator Swissair
Mark HB-ICV
Departure airport Zurich
Destination airport Geneva
Passengers 74
crew 6th
Lists of aviation accidents

Flight SR 306 was a scheduled flight of Swissair from Zurich to Rome with a stopover in Geneva . He became known when on September 4, 1963 a fully occupied Swissair Caravelle crashed a few minutes after take-off around 35 kilometers from Zurich near Dürrenäsch .

All 80 occupants were killed in the crash. 43 of them came from the small village of Humlikon , which suddenly lost a fifth of its inhabitants.

Flight history

On the morning of the flight involved in the accident, thick fog lay over the airport in Zurich, which is not unusual at this time of year. The RVR (runway view) on runway 34, which was intended for the start, was given as 180 meters. However, the required minimum visual range for the launch of the Caravelle was 400 meters.

At 7:04 a.m. local time (6:04 UTC) the aircraft, a Sud Aviation SE-210 Caravelle III with registration HB-ICV, was granted taxiing permission. At 7:05 a.m., the crew reported that they would roll across the runway and back again in order to reconnect the view and at the same time to blow away the fog. The start took place at 7:13 a.m. from runway 34.

At 7:20 a.m. the Caravelle reached an altitude of 2700 meters, whereupon it began to lose altitude again and took a slight left turn. The loss of altitude accelerated increasingly. At 7:21 a.m., an emergency call was received from the pilots and at 7:22 a.m. the aircraft crashed into a field on the outskirts of Dürrenäsch at a steep incline and at very high speed.

Victim

The crash site near Dürrenäsch

All 74 passengers and six crew members were killed. Although some houses were badly damaged at the crash site, none of the residents were harmed.

This accident was particularly significant because of the fact that 43 passengers came from the farming village of Humlikon . They wanted to visit an agricultural testing facility near Geneva, and for most of these passengers it was their first ever flight. Humlikon had 217 inhabitants at that time, so it lost a fifth of the population in one fell swoop.

The accident left 39 full orphans and five half-orphans in the village. In most of the affected families, the grandparents or older siblings were able to take over the duties of the parents, so that only six children had to leave their homes, but they too could be accommodated with close relatives.

Among the victims were all local councils, all school attendants and the postman . Since only 52 men with voting rights lived in Humlikon after the accident (at that time only men were entitled to vote or were authorized to exercise an administrative office in Switzerland), it was not easy to fill the necessary offices again, so that the canton of Zurich temporarily took over the leadership of the community had to take over.

At that time there was urgent field work for which there were no longer enough workers available. The canton's economics department appointed an agronomist to manage the agricultural work. The accident caused a great response all over Switzerland, and every day 40 to 70 volunteers from all parts of Switzerland and even from abroad helped with the harvest. With 2000 working hours, the harvest was brought in on time, so that the fields could be tilled again on time. About 600 tons of potatoes were brought in and the grain was threshed, all without harvesting machines. Nevertheless, the continuation of 22 farms was at risk.

A relief fund of CHF 250,000 was set up from contributions from the canton and numerous donations from Switzerland and abroad. These funds were used to hire auxiliary workers and a village helper, set up a kindergarten and buy washing machines that were installed in the community center. In addition, an agricultural machinery park was acquired, a machine hall built, a workshop set up and a machine specialist employed. Most of the companies could continue to operate.

Today Humlikon has largely recovered from the accident. The machine community and the aid fund still exist today. A memorial stone in the village commemorates the accident of 1963.

Cause of crash

The flight recorders did not provide any information about the cause of the crash. Several witnesses had seen the crash. They unanimously stated that flames had shot out of the aircraft at the left wing root during the flight. When parts of the Caravelle's rim and traces of hydraulic fluid were found on the runway at the starting position , the cause of the crash could be reconstructed.

At that time, a procedure was used in many places to "blow open" the runway in fog before take-off. To do this, the aircraft was turned around at the take-off position and, with the brakes on, the engines were brought to high power for 10 to 15 seconds. The runway was briefly cleared of fog over a length of around 500–800 meters by the hot jet of the engine. When there was no wind, it usually took two to five minutes for the "tunnel" created in this way to close again, which was sufficient for the start.

However, since only the first few hundred meters were fog-free with this method, Swissair refined it so that the aircraft rolled over the runway to the take-off position (i.e. made a so-called "back track"), stopping several times along the way and running the engines up . To a certain extent, several fog-free tunnels were laid one behind the other. However, as the tunnels closed again after a short time, they had to roll at increased speed between the individual stops. So you rolled with increased engine power and regulated the speed with the wheel brakes.

It was obvious that this procedure stressed the wheel brakes, but it was assumed that the brakes would not be stressed more than by emergency braking after a landing and that the usual control of the rim temperature by laying on of hands would therefore also be sufficient here. Precise measurements and recalculations were not made. The procedure was presented to the Swissair technical pilot and several flight instructors, and none of the concerns raised. The supervisory authority and the manufacturer were not informed because it was believed that they were within normal operating limits.

The corresponding procedural regulation has now been distributed to all Swissair pilots. The regulation did contain the note that the brakes should be used «carefully» to prevent them from overheating. However, this note has not been specified.

During the flight involved in the accident, the wheels apparently heated up so much during rolling back with this procedure that the magnesium rims lost their strength and when turning at the take-off point, at least the rim of which the fragments were found later broke. A hydraulic line was probably also damaged. It could no longer be determined whether the leaking hydraulic fluid was already igniting here. In any case, when retracting the landing gear, hydraulic lines that led through the landing gear shaft were damaged - either by the heat or mechanically by the defective rim - whereupon the escaping and at that time still highly flammable hydraulic fluid ignited on the hot brakes. This led to the complete failure of the hydraulics, making the aircraft no longer controllable.

Similar cases

literature

  • Lotty Wohlwend : SOS in Dürrenäsch - a catastrophe shakes Switzerland . Verlag Huber, Frauenfeld, 2009. ISBN 978-3-7193-1504-7
  • Jaqueline Marylin Vessely: Wall of Silence - Attempt to process two villages after the Swiss-Air crash in 1963. In: Bernd Rieken (Ed.): Fear in disaster research: Interdisciplinary approaches. Waxmann, Münster 2019, ISBN 3-8309-4090-4 , pp. 79-92.

documentation

Web links

Coordinates: 47 ° 19 '29.5 "  N , 8 ° 9' 33.1"  E ; CH1903:  654,471  /  241805