ASN Aircraft accident Junkers Ju-52/3mg4e HB-HOT Piz Segnas

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Last updated: 4 March 2021

Status:	Final
Date:	Saturday 4 August 2018
Time:	16:56
Type:	Junkers Ju-52/3mg4e
Operator:	Ju-Air
Registration:	HB-HOT
C/n / msn:	6595
First flight:	1939
Total airframe hrs:	10189
Cycles:	8783
Engines:	3 BMW 132A3
Crew:	Fatalities: 3 / Occupants: 3
Passengers:	Fatalities: 17 / Occupants: 17
Total:	Fatalities: 20 / Occupants: 20
Aircraft damage:	Destroyed
Aircraft fate:	Written off (damaged beyond repair)
Location:	1,2 km (0.8 mls) SW of Piz Segnas ( Switzerland)
Crash site elevation:	2475 m (8120 feet) amsl
Phase:	En route (ENR)
Nature:	Domestic Non Scheduled Passenger
Departure airport:	Locarno Air Base (LSMO), Switzerland
Destination airport:	Dübendorf Air Base (LSMD), Switzerland

Narrative:
A Junkers Ju-52/3m aircraft, operated by Ju-Air, was destroyed in an accident in a mountainous area in Switzerland. The aircraft crashed into the western slope of Piz Segnas at an elevation of 2540 m. All 17 passengers and three crew members were killed.
The aircraft had departed Locarno, Switzerland, at 16:10 on a flight to it's home base at Dübendorf.
The aircraft flew on a northeasterly course into the basin southwest of Piz Segnas. Towards the north end of the basin, it began a left turn, which developed into a descending spiral trajectory. A short time later, the aircraft collided with the ground almost vertically and at high speed.
Following the crash, all Swiss Junkers Ju-52 aircraft were grounded. Ju-Air was allowed to restart operations on August 17 with the two remaining aircraft of the same type. Since there were no indications of general technical defects at this time, the FOCA had approved the resumption of flight operations in compliance with precautionary measures.
On November 20, the Swiss TSB published an interim report. There was still no evidence that a serious technical problem led to the accident. The investigation of the wreck, however, revealed severe structural damage in the form of cracks and corrosion on the main spar, the supporting element of the aircraft wing, and other parts of the aircraft. This damage was hidden during normal inspections and maintenance and could only be determined from the debris.
Since the two Ju-52 HB-HOP and HB-HOS stationed in Dübendorf correspond in age as well as in hours of operation to the crashed aircraft, the Swiss authorities temporarily grounded both aircraft for inspections.

Probable Cause:

Direct cause:
The accident is attributable to the fact that after losing control of the aircraft there was insufficient space to regain control, thus the aircraft collided with the terrain.

The investigation identified the following direct causal factors of the accident:
- The flight crew piloted the aircraft in a very high-risk manner by navigating it into a narrow valley at low altitude and with no possibility of an alternative flight path.
- The flight crew chose a dangerously low airspeed as regard to the flight path.
Both factors meant that the turbulence which was to be expected in such circumstances was able to lead not only to a short-term stall with loss of control but also to an unrectifiable situation.

Directly contributory factors
The investigation identified the following factors as directly contributing to the accident:
- The flight crew was accustomed to not complying with recognised rules for safe flight operations and taking high risks.
- The aircraft involved in the accident was operated with a centre of gravity position that was beyond the rear limit. This situation facilitated the loss of control.

Systemic cause
The investigation identified the following systemic cause of the accident:
- The requirements for operating the aircraft in commercial air transport operations with regard to the legal basis applicable at the time of the accident were not met.

Systemically contributory factors
The investigation identified the following factors as systemically contributing to the accident:
- Due to the air operator’s inadequate working equipment, it was not possible to calculate the accurate mass and centre of gravity of its Ju 52 aircraft.
- In particular, the air operator’s flight crews who were trained as Air Force pilots seemed to be accustomed to systematically failing to comply with generally recognised aviation rules and to taking high risks when flying Ju 52 aircraft.
- The air operator failed to identify or prevent both the deficits and risks which occurred during operations and the frequent violation of rules by its flight crews.
- Numerous incidents, including several serious incidents, were not reported to the competent bodies and authorities. This meant that they were unable to take measures to improve safety
- The supervisory authority failed to some extent to identify the numerous operational shortcomings and risks or to take effective, corrective action.

Accident investigation:

Investigating agency:	STSB Switzerland
Status:	Investigation completed
Duration:	2 years and 6 months
Accident number:	No. 2370
Download report:	Final report

Classification:

Non-adherence to procedures
Loss of control

Sources:

» 20min.ch
» STSB Preliminary information

Follow-up / safety actions

Operations had been voluntarily suspended after August 4, 2018. The Swiss Federal Office of Civil Aviation (FOCA) allowed operations to be conducted per August 17 since the investigation by the STSB had not yet brought to light any technical problems with the accident aircraft. However, JU-Air first had to comply with the precautionary measures of the FOCA to commence flight operations. First, the FOCA required that, for the time being, a minimum altitude above the legal minimum altitude be maintained. Secondly, JU-Air’s aircraft had to carry a GPS data recorder that records every flight and allows subsequent assessment of the route. Third, the passengers should also remain strapped during the flight and not be able to circulate freely in the aircraft. This also applies to visits to the cockpit during the flight.

STSB issued 8 Safety Recommendations

Issued: --	To: FOCA	561
The Federal Office of Civil Aviation should ensure that rules are adapted to air operations with passengers on aircraft referred to in annex I of European Regula-tion 2018/1139 and that these effectively address the risks specific to such operations.
Issued: --	To: FOCA	562
Until safety recommendation no. 561 has been implemented, the Federal Office of Civil Aviation should ensure that the risks specific to the particular flight operations involving passengers on annex I aircraft, as defined in European Regulation 2018/1139, are identified and effectively reduced with an effort suited to the complexity and scale of the respective operation.
Issued: --	To: FOCA	563
When granting exemptions for annex I aircraft, as specified in European Regulation 2018/1139, the Federal Office of Civil Aviation should take into account the risks specific to their relevant operation and periodically review the exemptions.
Issued: --	To: FOCA	564
The Federal Office of Civil Aviation, together with organisations which operate his-toric aircraft primarily for the transport of passengers, should define effective risk-based management and supervisory measures which are capable of identifying and correcting the specific problems with this type of operation at an early stage.
Issued: --	To: FOCA	565
The Federal Office of Civil Aviation should improve its organisation of audits and inspections in such a way as to improve the exchange of information within the authority, as well as to enable both critical analysis of the organisation concerned and the identification of relevant problem areas more effectively.
Issued: --	To: FOCA	566
The Federal Office of Civil Aviation should acquire the necessary technical and methodological expertise for the supervision of historic aircraft or make it available from an independent party. Furthermore, it should ensure that supervision is exercised in an effective manner.
Issued: --	To: FOCA	567
The Federal Office of Civil Aviation should require the air operator to determine key performance data of its Ju 52/3m g4e aircraft following a major overhaul, and adapt the corresponding documents accordingly prior to the aircraft type being released for service.
Issued: 21-NOV-2018	To: FOCA	548
The Federal Office of Civil Aviation (FOCA), in cooperation with the flight operator, should take appropriate measures to ensure that the sister aircraft, HB-HOP and HB-HOS, are inspected for corrosion damage and defects in system components. (implemented)

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Photos

accident date: 04-08-2018
type: Junkers Ju-52/3mg4e
registration: HB-HOT

flight path into the valley

accident date: 04-08-2018
type: Junkers Ju-52/3mg4e
registration: HB-HOT

Aircraft history

date	registration	operator	remarks
1 Oct. 1939	A-702	Swiss Air Force
29 July 1985	HB-HOT	Ju-Air	registered

Map

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 Locarno Air Base to Dübendorf Air Base as the crow flies is 137 km (86 miles).
Accident location: Exact; as reported in the official accident report.

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.

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