Do microbursts even occur at FL390?

To the credit of Ian Ross (Ch9 Sydney?) I was watching the news when he came on with the old "In breaking news" and introduced the Qantas issue he only mentioned that a Qantas Airbus has called Mayday and made an emergency landing at Learmonth with passengers suffering suspected fractures.

There was no sensationalism at that time.

CASA on turbulence
 

CASA has a page devoted to Turbulence at http://www.casa.gov.au/airsafe/trip/turbulen.htm

Here is what they have to say about CAT:

It could never have been an A320 as this has only a seat capacity of 148 passengers. It was an A330-300 and it carried 302 Passengers.

fly in to Perth on a warm day and you'll understand what turbulence is all about... :eek:

roughest flights I've ever had have always been the ones coming back to Perth in the summer time from the east coast, especially when your coming over the hills on approach to YPPH.

reports coming through that sources inside QF have mentioned the incident was caused by a "computer malfunction"....:confused:

[QUOTE=Christian Dietzel;14053It was an A330-300 and it carried 302 Passengers.[/QUOTE]


That's funny. I thought QF's 333's were only configured 30J/267Y a total of 297 seats. Unless QF included the crew in the passenger count.




Jason

easy 5 infants and babies, not having assigned seating

Banjo

I'm not a pilot, but I am an engineer. Logic would suggest that if the aircraft systems told it to change altitude even suddenly, the nose would lower and it would descend, albeit rapidly. It wouldn't just drop. The only thing that is going to make it drop as it apparently did is sudden loss of the lift component, due to absence of air flowing over the leading edge.

Tech crew, feel free to correct me if I'm wrong.

Computer 'irregularity' on dropped plane

AIR safety investigators say there was an "irregularity" in the onboard computer equipment of a Qantas plane involved in a mid-air incident between Singapore and Perth.

The Airbus A330-300, with 303 passengers and a crew of 10, struck what the airline described as a "sudden change in altitude'' north of its destination yesterday.

The plane landed at Learmonth, about 40km from Exmouth, without any further incidents.

West Australian police said at least 20 passengers and crew aboard QF72 were seriously injured - some with spinal injuries and others with broken bones and lacerations.

Two Australian Transport Safety Bureau (ATSB) investigators are on the ground at Learmonth and five more are expected to arrive there later today.

The bureau's director of aviation safety investigation, Julian Walshe, says the plane was travelling at 37,000 feet and 110 miles north of Carnarvon when the incident occurred.

"The pilots received electronic centralised aircraft monitoring messages in the cockpit relating to some irregularity with the aircraft's elevator control system,'' he said in Canberra.

The aircraft then "departed level flight'', and climbed approximately 300 feet.

"The crew had initiated the non-normal checklist response actions.

"The aircraft is then reported to have abruptly pitched nose down.''

If the nose first tilted upwards as some passengers said (and the news report above), is it possible that the aircraft, because of its high altitude and heavy load, stalled, and then descended rapidly because of the stalling?

If that did happen, perhaps its a question of what caused the upward movement of the aircraft to start with...

Also i found this FAA document regarding operations of aircraft at altitudes over 25,000 feet. It provides a small section about weather and the jet streams, and some info about CAT as well (Starting at page 12 on your PDF reader).

http://www.bom.gov.au/weather/national/charts/UV.shtml - Pretty extreme UV conditions out to the NW - thats todays forecast, but it wouldn't change much between 2 days.

Come on Rhys, you really think experienced Qantas pilots are going to let a jetliner stall at cruise altitude?

Next you'll be saying someone shot at it from the grassy noll.

The suggestion it stalled is preposterous.

If it was a computer failure, though, as has been reported, how much of a say would the pilots have in avoiding a stall?

You can't discount a theory just because it 'sounds' impossible. With that theory, there shouldn't be any aircraft incidents as all 'experienced' pilots should able to handle every situation, even a computer malfunction outside of their control.

Where is VH-QPA at the moment? I suppose it hasn't left yet

Quite the opposite, and as many here know I would rather fly no other airline than Qantas, and believe their safety standards are very high, and i have no issue at all flying with them, and the pilots i know are very very experienced, so that is not what i am saying at all.

What i am saying is that for one reason or another, the plane gained altitude, then descnded rapidly - this sounds like a stall of some sort to me, and i have absolutely no suspicion that it was the direct fault of the flight crew whatsoever.

The reason for it gaining altitude will provide the key for why this incident happened - unusally high volume of hot air in the area? Flight computer malfunctioned (What caused it?). These are all questions that must be answered.

I flew on VH-QPA from Melbourne to Hong Kong back in August 2005.

Nick,

Rhys is saying the incident was created by a stall, not the computer glitch causing the 300 feet climb and then stalling. There has never been any mention of a stall.

A 300 feet climb is a relatively minor altitude change which I doubt would directly result in the engines stalling.

news.com.au has just released an article blaming computer issues for the incident.

Thats why its a theory and not proof - to be proven right or wrong nick.

What i did say NickN was that something caused it to gain altitude during cruise, which needs to be determined. This should in turn explain the sudden descent.

I agree David any command given, no matter how urgent or rapid would be a smooth transition ( thats if it was a command). In saying that, it does not count out an computer error occuring eg. reverse thrust being engaged. I know it sounds unlikely, as you might need weight on wheels and some other logics to achieve this to operarate, but i have seen computers do weird things.

Until we get the full story and maybe knowing what occured at what time during the flight from a data download it is hard to diagnose the fault.

I'm not sure on the loop time on the FDR on the A330, but isn't there a danger in incidents like these that the time taken for the aircraft to land is long enough to overwrite the data from the incident?

If the time is long enough yes of course, but I think I read somewhere the plane was on the ground in a very short time after this incident

Yes thats entirely possible, but i'm not sure of the time either, and a google search hasn't yielded anything.

Modern DFDR's can handle over 25 hours of flight time so any data would still be on the DFDR from this flight and probably previous flights.

As for the irregularity being reported by the ATSB - it wouldn't be unheard of due to the information coming into the main computer and that information possibly becoming corrupt for some reason giving the 300ft climb.

As for the rapid 6,000ft decent/drop being reported :eek: Thats a huge drop.

I have seen main computers 'freeze' on aircraft allowing for some weird disrepencies at times and the best the manufacturers came up with was a full memory capacity. On one occasion all four MFD's froze, leaving the crew unaware of their current location/situation for 30 odd minutes until they noted a moving map had not moved for some time.

Thanks Damien. I recall that with the China Airlines 747SP incident that the data on the FDR on the barrel roll was overwritten because of the time it took for the aircraft to get on the ground. It's good to see modern technology overcoming this problem.

Media release on the ATSB web site

The herc FDR can record up to the last 25hrs of data. I am sure civi aircraft are very similar. We also have other data retreival methods we can use to determine everything that has happened throught the flight. eg take off/landing times, cautions and warngings that occur, engine data etc etc.

Again i am not sure what sort of data retrieval devices airliners have besides the DFDR and CVR, but i am sure they would have the data stored to deterime what happenned at the time of the incident.

Are you perhaps displaying a lack of knowledge here?
You seem to be confusing the different types of stall that may affect an aircraft.

Cheers

Thanks for that was bugging me for a while!

Hi,

A 300ft climb may be relatively minor change in altitude but a potential stall (not engines rather airflow envelope over surfaces) can occur if there is a simultaneous significant loss in airspeed at FL390.

I have been scheduled on at least 2 flights in memory where the a/c (all QF A333's) have gone U/S and the same reason given for both has been a problem with the Flight Control Unit. Now whether this event is the manifestation of such issues inflight it is something that has certainly struck a chord with me.

Regards,
VC

FDR and CVR capacity
 

Not sure about the A330, but the B744 only has 2 hours of CVR compared to 25 hours of FDR, and if the CVR is not powered off after landing, there is a likelihood of its contents being overwritten by ground crew conversations, as partially happened in Manilla.

I think the newer solid state devices such as would be on the A380 have greater capacity but I'm not aware of the A330 situation; I'm pretty sure it was one of the earliest solid state recorders but it was circa 1993 from memory and the technology has moved on a lot in that time.

The ATSB's ongoing investigation into the Manila accident is meant to include "a review of the operator’s procedures for preserving a CVR recording following a serious incident or non-catastrophic accident."

Even though that's ongoing, hopefully one way or another the CVR in this latest accident has been preserved.

Hopefully the passenger interviews will try to see if any passenger activated a personal electronic device that was "dirty" enough to upset the aircraft computer.

I've always been a little worried about the Airbus autopilot systems even since the lecturer at my software programming course at Uni told us about the bugs they found in some of the first Airbus systems.

One of the bugs they discovered would have flipped the aircraft 180 degrees on its back if it ever went over the Arctic circle!

Remember the Lauda B767? It crashed after this very occurance.

Whichever way we look at things computers are only going to become a greater part of the global flight experience and regardless of what type of computer it is or what function it controls technology is not always perfect and these incidents are going to continue to happen one way or another. The real question is, how often are they going to occur and are people going to die as a result.

We have already seen faulty technology cause loss of life in the past. I really think that we have to try and have a little faith in those responsible for its development and hope they make their systems and hardware as perfect as possible.

Interestingly I found this from a website about risks to the public in computers and related systems...

The original source is from AFP news:

"On 19 Apr 1999, an Air India Airbus 320 en route from Singapore to Bombay via New Delhi had apparent had an autopilot failure at 27,000 feet, resulting in a dive that injured three crew members (two seriously) and an infant. The pilot was able to regain control, and manually flew the jet to Bombay. [Source: AFP, 19 Apr 1999]"

Did Laptop Cause Plane to Plunge?
 

This from todays news.com.au

http://www.news.com.au/travel/galler...013959,00.html

Just wondering, if the ATSB will be quizzing passengers about "whether they were using computers or electronic equipment before a Qantas aircraft plunged hundreds of metres", wouldn't some pax be afraid that they might be found accountable and therefore deny that they were ever using one (even if they possibly were using one at the time)? In such a case, if the use of electronic devices did cause the incident, we might never really know.

That's sounds interesting, however something strikes me as odd. If the a/c was going via New Delhi ex Singapore, then I would imagine it would have been tracking pretty much directly towards New Delhi. When they had the problem (and I'm not sure how far from New Delhi they were), why would they divert to Bombay (Mumbai)?? For one, it would have been closer to New Delhi; and two, there are are many other closer airports they could have gone to (especially since it was an A320 and size wouldn't have been an issue).
http://www.mapsofindia.com/maps/indi...r-airports.jpg

On the flip side, technology has greatly improved the safety of flying, and, fopr example, there are far less instances of "controlled descent into terrain" these days, and less events attributes to "pilot error" than when humans were totally in control.

You are absolutely right there too.

Gotta take the good with the bad.

Look at TCAS, that must have saved a few skins in its time.

Although that incident where the bizjet clipped a GOL 737 coz the bizjet pilots accidentally turned off their TCAS/Transponder was a worry.

Technology is great when it is used properly and it works well.

On your 1st point, i dont think if it was something as trivial as a wireless mouse or something that insignificant (thats what they believe so far), i dont think the ATSB would be pursuing any kind of legal action against said person, and would probably make that clear before being interviewed.

2nd point - it may have already landed in New Delhi and was then continuing onwards to Bombay from New Delhi when the incident occurred.