Inex-Adria Aviopromet Flight 450

Inex-Adria Aviopromet Flight 450, JP 450, was an international charter flight from Tivat in the Socialist Federal Republic of Yugoslavia to Prague, Czechoslovakia which crashed in the Prague suburb of Suchdol on 30 October 1975, at 09:20 AM. The McDonnell Douglas DC-9-32 with 115 passengers and 5 crew on board descended, under Instrument Meteorological Conditions (IMC), below defined Minimum Descent Altitude (MDA) during the final approach to Prague Ruzyně Airport RWY 25, entered a gorge above Vltava river, and was unable to outclimb the rising terrain. 75 of the 120 occupants died during the crash itself while 4 others died later in hospital. The accident remains the worst aviation disaster on the territory of today's Czech Republic.

Accident

The DC-9 was operated by Inex-Adria Aviopromet on a morning flight from Tivat to Prague with mostly Czechoslovak tourists returning home from vacations on the Adriatic sea. Captain Miodrag Marović (40) and First Officer Rade Popov (49) had an uneventful flight with clear weather, until they entered a published landing procedure above PR non-directional beacon (NDB). Czechoslovak ATC took over the aircraft at the border at 09:01. After identification, the crew asked for weather information. ATC responded that the total visibility in Prague is 1,500 m and on runway 25 (later known as runway 24) only 200 m. At the same time, ATC warned the crew that both the instrument landing system (ILS) for RWY 24 and the precision approach radar (PAR) were inoperative - "JP450, ILS and PAR are out of service on runway 25".

The pilot asked - "I understand, but what do we do now?". ATC responded - "You can continue to Prague or divert to another airport."

"Please wait" - the pilot replied.

After a while, the pilot continued - "So the RVR of 1,100 metres and the ILS and approach lights out of service?"

Since ATC never mentioned approach lights to be out of service, this message from the crew reveals that mental load started to build up caused by the uneasiness with the situation at the airport.

ATC responded - "The ILS is out of order. The approach lights and the runway lights are working. There are also beacons (NDBs) in operation."

Based on the information received, the crew decided to proceed according to the flight plan to Ruzyně Airport.

ATC contacted the crew again, while the aircraft was at an altitude of 1,500 m approaching PG NDB (beacon) from the southeast, and instructed the crew to continue to PG NDB then to PR NDB, and make a published, standard turn. ATC approved descent to 550 m (communication was in metres, not feet) and provided QFE pressure of 981. ATC's instruction was correctly read back by the JP450's crew. After passing overhead PR NDB the crew entered a published landing procedure. However, somewhere above the village of Vodochody the crew inadvertently missed the start of the published right turn and continued in a broader turn over the villages of Veliká Ves and Kojetice. After executing a wider-than-published right turn, the crew entered the final approach for runway 25 in IMC conditions (fog). Without the ILS and PAR support the crew was placed in a challenging and stressful situation during the final approach. Stress hormones level found, post mortem, in the body of the First Officer proves the emotional stress the crew was exposed to.

In addition, while executing a non-standard right turn the crew positioned the aircraft to the south (left) of the published glide path for the final approach. This horizontal deviation from the glide path continued to increase and at the place of the impact it was approximately 0.7 nmi.

During the turn, ATC again alerted the crew to an ILS outage, repeated the information about the QFE pressure at the airport, and required confirmation of the approach over two NDBs - "JP450, confirm approach over PR beacon and L beacon".

At 09:18 JP450 confirmed - "I understand, PR and L beacons".

This was the last transmission received from the JP450.

During this communication the crew continued to descend below the altitude approved by the ATC and deviate horizontally from the glide path, flying directly towards a Suchdol gorge, cut by the Vltava river, and well below the airport's elevation. Unfortunately, there are no publicly available Cockpit Voice Recorder (CVR) or Flight Data Recorder (FDR) recordings, to credibly reconstruct the cockpit communication and actions of the crew. Moreover, some sources cited the official report that the CVR stopped recording some 15 minutes before the crash due to a short magnetic tape, so there is no data regarding cockpit communication in this critical part of the flight. The crew, most probably, realized their mistake after establishing visual contact with the gorge. They selected full power, trying to climb above the rising ground of the river gorge, but it was too late. The aircraft first hit trees, 91 m below the airport's elevation, then struck a building and crashed into the residential area, leaving a debris trace of 350 m. The time of the crash was 9:20 AM. Taking into account elevation of the first impact 91 metres below the airport elevation, and the last approved descent to 550 metres QFE (above the airport elevation), the crew descended 641 m below the approved altitude.

At 09:21, when the crew did not report, ATC called them - "450, this is Prague. Confirm over PR beacon"

"JP450, can you hear me?"

"450, 450, do you hear?"

"450, I'm broadcasting blindly."

Response from JP450 never came.

Of 115 passengers and 5 crew on board, 40 passengers and 1 flight attendant survived the crash.