Hong Kong Probes Cathay-Dragonair in Near Miss

[oz_mark]

HONG KONG–Aviation authorities in Hong Kong say they are investigating an incident in which two jets carrying more than 600 people had to take evasive action after straying into each other's path as they were trying to land.

Cathay Pacific Airways said Tuesday that in the September 18 incident, one of its Boeing 777s and a Dragonair Airbus A330 were at the same altitude southwest of Hong Kong's airport when they came too close, triggering coughpit alarms.

Cathay said in a statement that the pilots responded immediately, with the Dragonair jet climbing and the Cathay plane descending.

The airline said the planes were one nautical mile (1,850 meters) apart at the closest and there was "no risk of collision."

Hong Kong Probes Cathay-Dragonair in Near Miss - WSJ.com

 

[Mal]

The airline said the planes were one nautical mile (1,850 meters) apart at the closest

While I realise this is still a decent distance, is anyone else concerned at this closeness?

Also, can anyone assist me with working out how one plane climbs, and one descends? Is this an automated computer system?

 

[pshepvic]

While I realise this is still a decent distance, is anyone else concerned at this closeness?

Also, can anyone assist me with working out how one plane climbs, and one descends? Is this an automated computer system?

My understanding is that TCAS provides a specific direction to each pilot - it will tell one of them to climb and the other to descend, but I'm not sure of the "rules" around how it determines who does what.

Some more info on TCAS: Traffic collision avoidance system - System Description

 

[ozmille]

While I realise this is still a decent distance, is anyone else concerned at this closeness?

Also, can anyone assist me with working out how one plane climbs, and one descends? Is this an automated computer system?

I would hope it is computer triggered because every time I walk straight to another person we go the same way :shock:

 

[pshepvic]

i would hope it is computer triggered because every time i walk straight to another person we go the same way :shock:

rofl

 

[rechoboam]

Jb747 could clarify I'm sure but my understanding is that TCAS warnings are actually very common.

 

[v8Statesman]

Jb747 could clarify I'm sure but my understanding is that TCAS warnings are actually very common.

Dear God, I hope not! (Unless it is at a Gate )

 

[casanovawa]

Hmmm, not much scope for avoidance in the vertical axis when approaching the gate eh... And never heard it say right or left (or where the hell did he come from) on Air Crash Investigations (think they follow the KISS principle with it)....


You'd probably hope it doesn't go off all the time coz when things do that (ie cry wolf) they tend to get ignored and/or switched off if at all possible...

 

[Demented Freak]

The article also doesn't mention that one of the planes (think it was the Dragonair one) encroached inside minimum separation with another plane as a result of taking evasive action. There's a couple of interesting threads on PPRUNE regarding the situation in HK and this incident, sounds like the ATC operations over there are struggling with a whole raft of staffing issues.

 

[serfty]

Interesting thread referred to:

• [*=1]Multiple Near Collisions in Hong Kong Airspace: Sunday 18 September - PPRuNe Forums

 

[jb747]

First thing...if you get to a fuel state at which you feel the need to declare an emergency, you don't request anything. You tell....

TCAS has two levels of warning. A traffic advisory, and a resolution advisory. Most traffic advisories come up because (say) you might be climbing to F200, and an aircraft above you is descending to F210. The system does not know that you'll both be leveling out soon, and just calls what it can see.

But, if it progresses to a resolution advisory, the TCAS will start to give directions to the pilots. They can be displayed in various ways, but will basically consist of a relatively gentle vertical manoeuver. This requires the autopilot and flight directors to be switched off, and the manoeuver is flown manually (in all aircraft). ATC clearances are overridden by TCAS. If moving away from one aircraft puts you onto a conflicting path with another, the systems are quite capable of 'threading the needle', and may demand reversals of the initial manoeuver.

TCAS alarms are not common at all. Even traffic advisories (which are non events) happen rarely. The only 'real' TCAS alert that I've seen also happened in HK, but it didn't affect me directly. My aircraft got a traffic advisory, and the CX following got a resolution alarm. In that case it was caused by an arriving US airliner who descended through his cleared altitude and went straight through the (rather busy) departure tracks.