Two heavy aircraft departing Hong Kong International Airport (HKG) had a very close call, which is now being investigated by regulators. I guess at least a close call wasn’t in the United States, for once?
In this post:
TCAS saves the day for two cargo jets departing HKG
This incident happened at around 7AM on Thursday, February 27, 2025, and involves two cargo jets that were both departing the airport:
- An MNG Airlines Airbus A330-300 with the registration code TC-MCN was departing for Istanbul (IST) with the flight number MB380
- A Silk Way West Airlines Boeing 777-200 with the registration code VP-BMU was departing for Baku (GYD) with the flight number 7L625
These flights were departing around the same time, with the A330 given clearance to depart from runway 7C, and the 777 being given clearance to depart from runway 7R. Those are parallel runways, and of course it’s common to use parallel runways for multiple operations around the same time.
However, in this case, the two planes ended up taking off at almost exactly the same time, and they had very similar departure paths. While air traffic controllers instructed them to maintain vertical separation, that wasn’t realistic given the limited departure separation.
The challenge with departing into the east from Hong Kong is that there’s a very narrow corridor through which planes can operate, due to terrain on both sides. As you might expect, putting two heavy jets on a near collision course with little ability to deviate isn’t ideal.
After takeoff, the planes kept getting closer and closer. Initially they took off and had around 1.5 nautical miles of separation, with 200 feet of vertical separation. However, that gap narrowed all the way to 0.45 nautical miles of separation, with no vertical separation.
Fortunately, as usual, TCAS (Traffic Collision Avoidance System) saved the day. The Silk Way West Airlines 777 received the alert first, around seven nautical miles after takeoff, and then descended in order to avoid a collision. Once the TCAS was resolved, both planes continued on their way, and completed their journeys without further incident.
VASAviation has an excellent video with a depiction of what happened, plus some of the air traffic control audio.
Regulators are now investigating this incident
Hong Kong’s aviation regulators have revealed that “relevant air traffic control personnel” have been removed from frontline duties, as “preliminary information indicates that the incident may involve non-compliance by ATC personnel with established procedures.”
With how tight Hong Kong’s departure path is into the east, I’m puzzled as to how they can issue near simultaneous clearance for jets. It’s normal to provide clearance with a bit of spacing, but one wonders what exactly happened here.
Did the air traffic controllers actually clear both planes at virtually the same time? Did one of the aircraft just take some time to actually start its takeoff roll, after being given clearance? Did air traffic controllers not realize earlier on what was happening?
We recently saw Hong Kong Airport’s new three runway system go live, so we’re seeing a lot more simultaneous takeoffs and landings. Hopefully what’s learned from this close call will help to prevent a similar incident in the future. You’ve just gotta appreciate how TCAS saved the day, as usual…
Bottom line
Two aircraft performing a parallel takeoff from Hong Kong had a very close call, whereby they were at the same altitude, just 0.45 nautical miles apart. While parallel takeoffs are common, typically there would be some separation in terms of when they take off, especially given the narrow corridor through which planes can fly after takeoff.
For whatever reason, that didn’t happen this time around, but fortunately TCAS saved the day. The air traffic controllers have been removed from their duties for now, while an investigation is being performed.
What do you make of this Hong Kong Airport takeoff incident?
I have a question on how TCAS works, or how responding to it works: 1) Do the two TCAS systems communicate to each other or is each one isolated and just tells you that you are in danger?
Where I am going with this is does TCAS say to each jet "Jet A and Jet B you are too close, Jet A climb, Jet B descend" or does TCAS just warn each jet that...
I have a question on how TCAS works, or how responding to it works: 1) Do the two TCAS systems communicate to each other or is each one isolated and just tells you that you are in danger?
Where I am going with this is does TCAS say to each jet "Jet A and Jet B you are too close, Jet A climb, Jet B descend" or does TCAS just warn each jet that they are too close and then the pilots have to figure out what to do? If it doesn't communicate with each other, then how do you prevent both jets from responding the same, in this case maybe both descending, and thus not solving the problem?
They communicate with each other in order for each aircraft to get "opposite" resolution - climb / descent. I believe there is also some "light mode" which can be utilised if one of the aircraft doesn't have TCAS, which uses the other A/Cs direction to make the "decision".
Thanks, I appreciate the info!
Further to my comment above, based on flight paths it would appear the 7C takeoff followed the 7R SID for whatever reason. Naturally two planes on the same SID taking off at same time with minimal horizontal separation due to parallel runways is not supposed to happen. Why this happened, will inevitably be learned via investigation.
There is nothing dangerous about the parallel takeoff, shame on such speculation. At first blush the aircraft departing 7C did not follow the SID, which calls for a left turn shortly after takeoff. Fairly straightforward.
At the end of the video it already states "As the climbing rates of the two cargo flights varied from what the ATC officers had anticipated, the desired vertical separation was not achieved"