AIRSERVICES Australia changed its procedures for flights at Sydney airport after a turboprop commuter plane was involved in a freak mishap because of wake turbulence from an Airbus A380 superjumbo landing on another runway.
The SAAB 340 was on a 14km final approach for runway 34 right in November last year, the Australian reports.
It was descending through an altitude of about 2400ft when it experienced an uncommanded roll, the nose pitched down and it dropped 300-400ft .
The crew managed to regain control after about 15 seconds when the autopilot disengaged but a passenger suffered minor injuries in the upset.
The incident raised new concerns about the giant jets and the impact on smaller planes flying behind and those landing on nearby runways.
The circumstances are unusual enough that the Australian Transport Safety Bureau yesterday released a report alerting international safety agencies to the problem.
Wake turbulence is caused by vortices – horizontal twisters – generated by an aircraft’s wingtips. Bigger planes generally generate bigger vortices and they have been known to upset smaller following planes, and even cause crashes.
The SAAB was not following the A380 but on a different runway 1km to the west.
By: Schorsch - 13th December 2009 at 16:45
I was just being tongue-in-cheek about the 20 min separation. But as we all know, there have been several fatal accidents involving small planes behind medium aircraft (B727 etc) so they will have to look at the current separation criteria, although the A380 probably generates a similar amount of wake turbulence to the 747:)
All the test conducted with the A380 for the certification and wake vortex limits showed how limited the system of fixed seperation is. Sometimes it works well as the seperation is normally quite large, but sometimes it doesn’t. I don’t know if the ICAO requires seperation for aircraft which are not on the same flight path. Theoretically, with given wind conditions, there alsways exists a “no-go-area” behind an aircraft changing its shape with wind and weight-relation between the aircraft. An 380 could pass behind a B737 with 5m distance, while a CRJ200 may need a 3 minute seperation on a parallel or crossing flight path when an A380 leads.
The A380 produces on average 20% stronger wakes than a B747, although it is about 50% heavier. The B757 is known to have particularly nasty wakes (for its size).
By: PMN - 13th December 2009 at 13:38
I was just being tongue-in-cheek about the 20 min separation. But as we all know, there have been several fatal accidents involving small planes behind medium aircraft (B727 etc) so they will have to look at the current separation criteria, although the A380 probably generates a similar amount of wake turbulence to the 747:)
In all fairness I’m sure the clever people who design aircraft and keep planes from meeting at high speed in the air have actually thought about this!
Paul
By: Arabella-Cox - 13th December 2009 at 12:31
No, why?
Actually, when you have a healthy cross-wind the seperation can be reduced to the usual 3nm irregardless of aircraft type. The strength of the wake vortex is not linearly connected to aircraft weight, and its dissipation changes with weather conditions. Under some circumstances very stable vortices can form.
I was just being tongue-in-cheek about the 20 min separation. But as we all know, there have been several fatal accidents involving small planes behind medium aircraft (B727 etc) so they will have to look at the current separation criteria, although the A380 probably generates a similar amount of wake turbulence to the 747:)
By: Balu the Bear - 13th December 2009 at 11:29
Good work Balu. The increased separation requirements will surely inconvenience small operators.
thx for the flowers, but another user in another forum actually did the work!
By: Schorsch - 13th December 2009 at 11:14
Is the aircraft going to operate to any airports with a single runway only? They will have to apply 20 minute separation.
No, why?
Actually, when you have a healthy cross-wind the seperation can be reduced to the usual 3nm irregardless of aircraft type. The strength of the wake vortex is not linearly connected to aircraft weight, and its dissipation changes with weather conditions. Under some circumstances very stable vortices can form.
By: PMN - 13th December 2009 at 11:09
The increased separation requirements will surely inconvenience small operators.
Not if it means their aircraft stay in the sky when they’re supposed to.
Paul
By: Arabella-Cox - 13th December 2009 at 10:49
Good work Balu. The increased separation requirements will surely inconvenience small operators.
By: Balu the Bear - 13th December 2009 at 09:55
By: Arabella-Cox - 13th December 2009 at 08:01
A suitable short-term solution would surely be to know where the wind is coming from and to ensure that smaller, more vulnerable aircraft are able to land without the risk of wing vortices from preceding aircraft blowing into their path. If, for example, you have a runway 36L and 36R with a light wind blowing out of the west, you are going to encounter problems if you have an A380 landing on the left runway and a Saab 340 on the right runway.
Is the aircraft going to operate to any airports with a single runway only? They will have to apply 20 minute separation.
By: T5 - 13th December 2009 at 04:44
A suitable short-term solution would surely be to know where the wind is coming from and to ensure that smaller, more vulnerable aircraft are able to land without the risk of wing vortices from preceding aircraft blowing into their path. If, for example, you have a runway 36L and 36R with a light wind blowing out of the west, you are going to encounter problems if you have an A380 landing on the left runway and a Saab 340 on the right runway.
By: Arabella-Cox - 12th December 2009 at 22:23
Zounds! Another fudge factor to build into the equation. Biggest plane + latest technology = loads of profit(I forgot there were other planes in the sky)
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December 12, 2009 at 10:11 pm