A Ju-Air Junkers JU-52 ("Tante Ju", "Auntie Ju"), registration HB-HOT performing a flight from Locarno to Dubendorf (Switzerland) with 17 passengers and 3 crew, impacted terrain at N46.9001 E9.2288 coming to rest at an elevation of about 2540 meters/8330 feet just southeast of Martinsloch/Piz Segnas (Switzerland) at about 16:50L (14:50Z). A Rescue and Recovery operation has been initiated. All 20 occupants were killed.
Local Police confirmed a Junkers aircraft crashed at Piz Segnas, no further details are known, 5 helicopters have been dispatched for rescue and recovery. Police later added, the wreckage is at an elevation of 2540 meters at the western flank of Piz Segnas. A flight restriction to protect rescue and recovery operation was issued.
In the morning of Aug 5th 2018 local police confirmed HB-HOT of Ju-Air was involved in the accident and announced a press conference at 14:00L (12:00Z).
Ground observers watched the aircraft flying in the area over Obersaxen (Switzerland) south of Piz Segnas and estimated they were flying at 11,000 feet.
Ju-Air confirmed the accident stating on their website: "Accident 4th August 2018: We have the sad duty to announce that one of our Ju-52 aircraft had a accident today. At the moment, no further information is available."
The aircraft had performed a flight from Dubendorf to Locarno on Aug 3rd 2018 and was about to return to Dubendorf.
Mode-S Data show HB-HOT departing and climbing through 4500 feet between 14:20Z and 14:25Z.
A weather station at Crap Masegn (Elevation 2500 meters), about 3.5nm southwest of Martinsloch, reported winds from the north gusting up to 25 knots.
In a press conference on Aug 5th 2018 local police reported all 17 passengers and 3 crew were killed in the accident. Local Police have handed the investigation to the Bundesstaatsanwaltschaft (federal prosecution office). Switzerland's SUST stated that the aircraft did not collide with other aircraft or cables, there is no indication of external influences, the aircraft also did not lose any parts prior to impact. The aircraft came down nearly vertically at high speed, the reason for this scenario needs to be determined. There was no emergency call and no post-impact fire. Ju-Air stated the captain, ex Airforce and Swiss, had 900 hours on type, the first officer, ex Air Force, Swiss and Edelweiss, had 250 hours on type. Ju-Air have suspended their operations, the museum is also closed.
On Aug 6th 2018 a ground witness, a military pilot, reported he had observed the aircraft from his garden about 10 minutes prior to the accident. He saw the aircraft rolling to initiate a left turn when all of the sudden the aircraft tipped over to the left and nose down. One of the motors roared up and seconds later the aircraft was stabilized again and continued its flight normally. The military pilot believes this was a first indication of a serious control problem. It is probable, the witness continued, that they had the problem again up in the mountains and were not able to correct it. If the controls fail in this scenario with the aircraft tipping to the side the nose drops and the aircraft impacts ground near vertical.
On Aug 6th 2018 a ground witness located at the alpine hut at Segnesspass/Martinsloch reported that the aircraft was tracking north passing Martinsloch, but before overflying the ridge the aircraft entered a left turn and then went down, as if following a plumbline. Initiating the turn until impact lasted less than 15 seconds.
On Aug 6th 2018 Switzerland's Civil Aviation Authority (BAZL) announced, that the JU-52 is not being grounded, hence is permitted to fly.
On Aug 6th 2018 the CEO of Ju-Air announced they are planning to resume their flights at around August 17th 2018.
On Aug 7th 2018 BAZL stated that the flight restrictions at Piz Segnas are being ended by the end of day after completion of recovery of the wreckage. BAZL further states that they have taken note of Ju-Air's intention to resume flights on Aug 17th 2018. As long as there is no substantiated suspicion of a technical defect BAZL can not order a grounding of the aircraft. Should new findings be made until Aug 17th 2018, the BAZL will act and if necessary issue a grounding order. Ju-Air have to ascertain that their crews and maintenance personnel are mentally capable to ensure safe flight operations. HB-HOT had been last examined by BAZL on Apr 6th 2018 and received the air worthiness certificate for the next two years after no discrepancies were found.
On Aug 16th 2018 BAZL reported that the investigation so far has not revealed any clues to a technical cause of the crash of Aug 4th 2018. Nonetheless, the BAZL demands that a number of precautionary measures are being implemented by Ju-Air prior to resuming flying operations on Aug 17th: all aircraft must carry a recording GPS receiver to permit assessment of flight routes, the aircraft must observe an increased minimum safety height above legal requirements and the passengers must remain seated with their seat belts fastened throughout the flight and are no longer permitted to move freely within the aircraft (including cockpit visits). Ju-Air have already indicated they are going to comply with the demand. The investigation is ongoing and could take several weeks to months until first preliminary results. Should during the investigation new information of a technical problem be found, the BAZL will again assess the situation and may introduce new measures up to grounding the aircraft.
On Aug 21st 2018 Switzerland's SUST announced they have opened an investigation into the crash. The SUST reported the aircraft entered the enclosed valley southwest of Piz Segnas on a northeasterly heading. Approaching the northern end of the valley the aircraft initiated a left turn which developed into a spiral descending trajectory. A brief time later the aircraft impacted terrain almost vertically. All 17 passengers and 3 crew died in the impact, the aircraft was destroyed, no third parties were harmed, there was minor land damage.
On Nov 20th 2018 Switzerland's BAZL grounded the remaining JU-52 aircraft HB-HOP and HB-HOS of Ju-Air reasoning that the investigation by the SUST brought about substantial structural damage in the area of the wing spars at HB-HOT, which could not be detected during regular maintenance and inspections. According to today's knowledge and investigation findings that damage has no link to the crash of HB-HOT.
On Nov 20th 2018 Switzerland's SUST released a preliminary report in German stating that a number of cracks were found in the area of the left hand engine mount at the lower spar of the left wing as well as corrosion in the area of the wing root. Further examination of the damage is being conducted, at first sight the damage does not appear to be causal for the accident.
A preliminary brief analysis states that there is no evidence the deficiencies found on the wreckage of HB-HOT were causal for the accident. It is likely however, that similiar damage exists on other aircraft of the operator and thus adversely affect flight safety. A number of deficiencies were also found in the documentation of maintenance works as well as in the management of spare parts, which establishes a potential risk.
On Nov 20th 2018 the operator stated that the investigation so far found no technical reasons for the crash of HB-HOT. The SUST detected corrosion at one of the wings of the accident aircraft, however, this damage was not cause of the crash. The summer operation 2018 has already ended, bookings for 2019 are being accepted. The operator agrees with the grounding of their aircraft to ensure that no damage similiar to HB-HOT remains on the remaining aircraft. One of 8 spars is affected at an area that so far was not accesible during regular maintenance and inspections, the damage thus was only detected following the accident. A third JU-52 aircraft, registration HB-HOY and not affected by the grounding because of different production and year, is anticipated to join the fleet shortly.
A NOTAM reports a new rope way cable has been erected at an elevation of 2251 meters/7385 feet MSL about 100 meters/330 feet AGL on Aug 3rd 2018 about 1.3nm south of the crash site, this however was not related (see not related NOTAM below).
On Aug 2nd 2019 Switzerland's SUST released a Status Report reporting that the investigation succeeded in reconstructing the complete flight path of HB-HOT based on photos, videos taken by the passengers as well as by testimonies of witnesses on the ground. The SUST wrote:
It is possible to reconstruct the entire history of the flight based on the various data storage devices, using the following high-precision method for the last minutes of the flight: The valley south-west of Piz Segnas was captured using a three-dimensional laser scan and combined with the three-dimensional terrain model from the Federal Office of Topography. A laser scan of a sister aircraft of HB-HOT was taken and a three-dimensional model of the aeroplane was created. This means that images of the accident aircraft taken from the ground during the flight can now be positioned and analysed with regard to the terrain. This model can also be used to evaluate images from inside the aircraft to determine the flight path. The existing still images and video material should make it possible to determine the positions of the accident aircraft in space, its attitude relative to the terrain and its speed relative to the ground for the critical phase of the accident flight.
At the same time, the audio tracks from the existing video material will be analysed. Spectral analysis of the audio recordings may make it possible to determine the revolutions per minute of the engines and draw conclusions about the condition of the engines during the course of the accident. This work is ongoing, and the STSB is receiving support from the French safety investigation authority, the BEA.
Furthermore, the mass of the aircraft and the position of the centre of gravity are being determined in order to determine their influence on flight performance.
In order to reconstruct the flight characteristics and the aerodynamic parameters prevailing during the course of the accident (e.g. attitude and true airspeed), it is necessary to know the small-scale movements of the air masses in the valley south-west of Piz Segnas. For this purpose, the wind flows in this valley will be simulated using a sophisticated model, with the real wind and temperature data being incorporated as boundary values. In order to validate and quantify the regularity and extent of the effects calculated during this simulation, for several weeks this year, measurements will be conducted in the area of the accident. A traditional weather station will determine the wind, atmospheric pressure, temperature and humidity on the ridge next to the Segnas Pass. A lidar system (Laser Detection and Ranging - a measuring system that emits laser pulses and evaluates the backscattered light from the atmosphere, in this case with regard to the Doppler Effect. In the present case, it is used for threedimensional measurement of wind above the site) will be used to record the three-dimensional flow conditions in the area of the flight path shortly before the beginning of the spiral-shaped flight path. The technical and logistical challenges mean that the success of these measurements cannot be guaranteed. In particular, for the measurements being helpful for explaining the accident of HB-HOT, weather conditions comparable to those on the day of the accident must occur during the midsummer measuring period.
The SUST states in the status report that they estimate the release of the final report for the first quarter of year 2020 if everything continues according to plans.
On Aug 4th 2020 the SUST released their second status report now indicating the draft final report has already been sent out, the investigation expects the final report to be released until end of 2020.
The SUST stated:
The STSB used photogrammetric methods to determine the positions in space of the aircraft involved in the accident, its orientation angles in three axes and its speed relative to the ground, especially for the crucial flight phase before the accident.
An analysis of the audio tracks from the available video recordings made it possible to determine the rotational speed of the engines and to assess their operation during the accident.
In addition to a detailed analysis of the weather conditions, the STSB arranged for the wind flow around the Segnes Pass to be simulated using a fine-mesh model, by means of which the actual wind and temperature data were used as boundary values. Moreover, for several weeks last summer, the STSB took measurements in the area of the accident. In addition to a classic weather station, which measured the wind, air pressure, temperature and humidity on the ridge of the Segnes Pass, a solar-powered wind measuring system (Lidar) recorded the three-dimensional flow conditions in the area of the flight path shortly before the onset of the spiralshaped flight path. This measurement enabled the STSB to reconstruct the wind conditions on the day of the accident in the valley basin southwest of Piz Segnas to such a degree that it could assess their likely effect on the aeroplane involved in the accident.
The SUST also looked into systemtic issues like flying tactics in the mountains and general flight operations.
Related NOTAM:
LS W1440/18
B)2018AUG04 1610 C)2018AUG05 2359 EST
E)TEMPO R-AREA ESTABLISHED AT SEGNASPASS RADIUS 9.3 KM
(465408N0091329E RADIUS 5.0 NM). DUE TO RESCUE MISSION, ENTRY
PROHIBITED FOR CIV ACFT EXC HEL EMERG MEDICAL SER (HEMS).
F)GND
G)FL130
Not related NOTAM:
LS B0866/18
B)2018AUG03 0551 C)2018SEP07 2359 EST
E)ROPEWAY CABLE 1.7KM SSE SEGNASP. MARKED, LGTD, LEN 699M, 465238N0091407E, 100.0M / 328.1FT AGL, 2251.0M / 7385.0FT AMSL.