Air China B738 at Ulanbaator on Jan 8th 2015, rejected takeoff due to amended route clearance

Last Update: December 17, 2018 / 14:40:21 GMT/Zulu time

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Incident Facts

Date of incident
Jan 8, 2015

Classification
Report

Airline
Air China

Flight number
CA-902

Destination
Beijing, China

Aircraft Registration
B-5500

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

An Air China Boeing 737-800, registration B-5500 performing flight CA-902 from Ulanbaator (Mongolia) to Beijing (China), was taxiing for departure on taxiway F when tower cleared the aircraft for takeoff from runway 32. Subsequently departure control advised tower they wanted a different initial route clearance. In the meantime B-5500 had reached the runway and was accelerating for takeoff, when tower began to transmit the amended initial departure clearance. 20 seconds after CA-902 began their takeoff run the crew rejected takeoff at high speed. The aircraft slowed safely and returned to the apron.

The flight was delayed by 3 hours as result.

Mongolia's Aircraft Accident Investigation Bureau (MAAIB) released their final report concluding the probable causes of the incident were:

Initial take-off clearance was delivered to CCA902 early, while aircraft was taxiing on TWY “F” to RWY32.

Tower controller did not use phraseology “Change of Clearance”, when he transmitted departure procedure change to CCA902

The MAAIB reasoned that the incident per se was to be rated an incident and as such was outside their scope of investigation, however, Mongolia's CAA requested a final report by the MAAIB stating: "... we have done associated inspections in accordance with the information related to sudden aborted take-off event and conclusions of inspectors have been delivered to the AAIB, please request final inspection report from the AAIB of Mongolia", a CAA inspector concluding "Air traffic controller gives an instruction during the traffic loads, but flight crew understood that instruction wrong" and another CAA investigation concluding "Air Traffic Controller instruction given in the take-off stage while crew was concentrated on the take-off and it was reason of misunderstanding by the flight crew and sudden aborted take-off."

The MAAIB analysed:

2.1.1 At 07:26:48 AM, Tower controller cleared for take-off, while the CCA902 taxiing on the TWY “F”, near by the intersection with TWY "D".

2.1.2 Area controller contacted to tower controller requesting to change CCA902’s initial permission ANIKU1 departure to radial 160. Area controller made this request to get lateral separation between, KE867 descending from Polho to Ulaanbaatar on airway B339 and CCA902 departing from Ulaanbaatar to Sainshand on airway A575 to comply with:

- 3.7.4 of Annex 11 “Coordination of clearances”,
- 6.3.2.2 of Doc 4444 “Coordination”,
- 6.1.1 of advisory circular AC172-01 “Besides Approach controller provides ATC clearances to the departing aircraft, they clarifies departing procedure and departure standard route in order to maintain safe distances between the aircrafts”,
- 2.2.1.3.3 of General manual of Mongolian Air Traffic Service. “Coordination of cooperation”.

2.1.3 At 07:28:22 AM, Tower controller transmitted departure procedure change information to the CCA902 when the aircraft was on its take-off run phase of the flight.

The tower controller’s above action is inconsistent with the provisions of the following documents:

- 5.2.1.7.3.1.1 of Chapter 5 of Annex 10 Aeronautical Telecommunications. “Except for reasons of safety no transmission shall be directed to an aircraft during take-off, during the last part of the final approach or during the landing roll”,

- 2.8.3.2 ICAO Doc 9432. “An air traffic control route clearance is not an instruction to take-off or active runway” 4.5.4 of ICAO Doc 9432. “Except in cases of emergency, controllers should not transmit to an aircraft in the process of take-off or during the early stage of climb”,

- 5.1.1 of advisory circular 172-01. “In order to ensure safety, it is prohibited that controllers transmit to an aircraft in the process of take-off or during the landing roll)” 12.3.5.3 of Doc 4444. "Change of clearance"

2.1.4 At 07:29 AM, only KE867 was flying in the Approach Area of Ulaanbaatar aerospace at FL10400m via airway B339 and if KE867 descends with average vertical speed of 8m/s, after 9 minutes it could reach FL6000m at 90 km distance from ZMUB.

If CCA902 could take-off on 07:28 AM per plan, it could reach FL6000m at 60 km distance from ZMUB, longitudinal separation between the two aircrafts could be at least about 30 km and lateral separation around 10 km.
Incident Facts

Date of incident
Jan 8, 2015

Classification
Report

Airline
Air China

Flight number
CA-902

Destination
Beijing, China

Aircraft Registration
B-5500

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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