Ceiba Intercontinental B738 over Senegal on Sep 5th 2015, midair collision with ambulance jet
Last Update: August 21, 2017 / 11:27:35 GMT/Zulu time
Incident Facts
Date of incident
Sep 5, 2015
Classification
Accident
Aircraft Registration
3C-LLY
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
Non-Compliance of 6V-AIM with the assigned flight level. The aircraft was at FL350 while the crew had correctly read back to maintain FL340. The captain of 3C-LLY claimed 6V-AIM was descending on them.
Only the black boxes could have helped to identify how such a scenario could have developed. However, the black boxes disappeared with the aircraft.
It is possible that a fault in the air data may have contributed to the mid air collision.
Contributing factors
- An misindication by one or both of the altimeters of 6V-AIM appears plausible.
On Jul 23rd 2015 ATC detected the aircraft at FL310 instead of assigned FL320, which was indicated by the altimeter(s) while the transponder showed FL310.
On Aug 31st 2015 ATC detected the aircraft at FL350 instead of assigned FL360 indicated by the altimeter(s).
On Sep 5th 2015, flight Dakar to Ouagadougou, the autopilot acquired FL311 when flight level 330 was assigned and later acquired FL333 when flight level 330 was assigned.
- Failure to comply with procedures
Provisions in the Senegalair operating manuals prohibit the climb into RVSM airspace as soon as an altitude difference of 200 or more feet of one or both of the primary altimeters is being detected (during flight preparation a maximum altitude difference of 75 feet is permitted).
Following the significant altitude deviation of Jul 23rd 2015 no tech log entry was made. The aircraft such continued operations without interruption or intervention by maintenance until Sep 5th 2015.
The maintenance engineer authorized to overview maintenance and sign the aircraft airworthy left the company on Aug 15th 2015. At the very latest the aircraft should not have been returned to service following that date.
The aircraft had returned from a flight on Aug 8th 2015 and remained on the ground until Aug 29th 2015. On Aug 27th 2015 the notification of the serious incident was sent. The application of the procedures required for this type of situation would have prevented the aircraft to continue operation for the series of flights including the accident flight with its defective altimeter system(s).
- renewal of aircraft airworthiness certificate while the level 1 anomaly still existed
- re-validation of the first officer's pilot's license although he did not have the medical certificate required. The basic Algerian license was issued not in accordance with RAS 1 and the requirements of a personal pilot license.
The BEA published the testimony of the captain of the Ceiba Boeing:
We were cruising at FL350 from DKR to COO on Airway UA601 with Dakar Control on 129.5. Communication with Dakar was unstable and he informed us to maintain FL350 and approach waypoint GATIL to contact with Bamako on 125.4. Aircraft status was good, no significant weather, no turbulence. I was pilot monitoring (PM) and my FO was pilot flying (PF). Flight attendants were making service for passengers.
Our radios were set: N1 Box: 129.5 (Dakar, active), N2 Box: 125.4 (Bamako, active), so we could monitor both of them. Monitoring Bamako on 125.4 we defined that we will have one opposit traffic at FL340 approx the same time overhead GATI (at 18:14 UTC). We started to scan our display and outside expecting one traffic one thousand below us at FL340. But we could see nothing about any traffic. Some time later on our displays we could see the other traffic one thousand above us at FL360. We continued scanning but it was not easy to make visual contact because there were clouds (CB) ahead as a background, and haze on the horizont. After all when we saw the plane it was really very close and looked as if it was descending through our flight level. It was small jet aircraft. There were no any preventions and TCAS warnings about traffic. When the traffic passed by we felt a sharp but not strong shake up of the aircraft. And only after the aircraft passed by and was below and behind us we got a TCAS aural warning "Traffic! Traffic!" I did check flight controls, systems and engine instruments. Everything was good. We tried to communicate with Dakar but communication with Dakar was broken. As we already passed point GATIL we changed to Bomafo on 125.4. Bomafo confirmed that the plane which was conflicting had to maintain FL340 and was flying from Bomako to Dakar Airspace. He gave us callsign and type of that traffic. It was 6V-AIM and H125B.
After that I received information from other crew members about missing part of the right wing let. Having enough fuel and good weather in our final destination Malabo I decided to divert to our base.
Signed Sep 6th 2015 by the captain.
The BEA reported that 6V-AIM departed Ouagadougou's runway 22 at 16:36Z, was cleared to climb to FL340 and levelled off at FL340. At 17:02Z the aircraft was handed off to Bamako Center at 125.4MHz and was cleared to proceed to GATIL via Bamako, the crew provided estimates for waypoint GATIL was provided at 18:10Z and for Dakar at 18:54Z. At 17:13Z the crew requested to climb to FL380 because of clouds ahead and was cleared to climb to FL380. 6 minutes later the crew requested to descend to FL240 but also advised they could maintain FL380, they had a sick person on board and a lot of turbulence. 88nm ahead of Bamako the crew requested to climb to FL400 and was cleared to climb, but 5 minutes later advised that up there was turbulence too and requested to descend to FL340. At 17:27Z Bamako cleared the flight to descend to FL360, 4 minutes later the crew repeats the request for FL340, Bamako now clears the flight down to FL340.
At 17:55z 6V-AIM reported passing waypoint ENINO at FL340. Bamako instructed the flight to contact Dakar on 129.5MHz once they had passed GATIL waypoint. At 17:57Z 6V-AIM requested to deviate 10-30 degrees left to avoid (probably weather) and was cleared for the deviation.
At 18:00Z 6V-AIM contacted Dakar and requested to deviate 10nm to the left of the airway due to weather. Dakar instructed the flight to maintain FL340 and set the transponder to 5040, the crew correctly read back both instructions at 18:01Z. At 18:04Z Dakar requests the crew to verify transponder code 5040, the crew responded advising 5040 was set.
The aircraft passed waypoint GATIL, the collision took place at about 18:12Z between GATIL and DEMOL, numerous attempts to contact the flight crew, including attempts by other aircraft, starting 18:16Z remained without response. At 18:22Z the aircraft appeared on Dakar Center's radar screen showing FL350 instead of FL340 and transponder code 5004 (instead of 5040). At 18:53Z the aircraft overflew Dakar VOR at FL350 and continued on radial 293 towards the west. About 48nm from Dakar VOR the aircraft begins to descend, at 19:07z the aircraft descended through FL330, turned right, then immediately left, then descended from FL326 to FL126 within seconds and disappeared from radar 59nm from Dakar VOR.
At 19:10Z Dakar pronounced DETRESFA reporting the loss of an aircraft. A Senegalese Falcon 50 was dispatched the crash site and arrived at 21:29Z. A patrol boat was dispatched as well and arrived the following day at 04:50Z, an Air Force King Air was dispatched the following morning and arrived at the crash site at 06:52z, a Portugese CASA 295 arrived at 09:35Z. On Sep 7th 2015 the Falcon 50 at 11:46z received an ELT signal at 243 MHz which was located at 63nm from Dakar VOR on radial 263. The patrol boat rushed to that position but could not find anything. A Spanish Casa 235 joined the search, the fleet of aircraft and boats continued for a couple of days to search the area around the last known position of the aircraft, however to no avail. The search was finally aborted and the aircraft was pronounced disappeared.
Incident Facts
Date of incident
Sep 5, 2015
Classification
Accident
Aircraft Registration
3C-LLY
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
This article is published under license from Avherald.com. © of text by Avherald.com.
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