Qantas emergency landing
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iompasseo
you wrote something about the first priority being to protect the aircraft...I submit that the first priority should be to protect the people aboard the aircraft.
because the plane's structure is perhaps not as robust as I would like the plane saved itself at the expense of the passengers (granted they were not wearing seatbelts).
''they don't build 'em like they used to''.
you wrote something about the first priority being to protect the aircraft...I submit that the first priority should be to protect the people aboard the aircraft.
because the plane's structure is perhaps not as robust as I would like the plane saved itself at the expense of the passengers (granted they were not wearing seatbelts).
''they don't build 'em like they used to''.
...authority....
Lightbulb: The automatic i.e. no pilot intervention (simplistically) worked. The fault ended its authority. If the autopilot still had authority do deal with the problem that it had detected, it would have voted the incorrect source of data out and disconnected that input into the EFCS, then carried on flying normally. It is not designed to do this, that is what pilots are for. You open the loop and let them decide what is the next course of action using the relevant documentation to understand what fault is being displayed and isolate it.
It appears Airbus are making changes to how you would deal with the information presented if this fault reoccurred. Don't blame the pilots OR the aircraft.
It appears Airbus are making changes to how you would deal with the information presented if this fault reoccurred. Don't blame the pilots OR the aircraft.
Lightbulb: It appears Airbus are making changes to how you would deal with the information presented if this fault reoccurred. Don't blame the pilots OR the aircraft.
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FDR
The fault remained because the aircraft could not turn the faulty unit off. That is a human function. The AoA sensor could safely remain faulty if ADIRU 1 was switched off.
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This event is a first time experience for that specific ADIRU type, Airbus is confident a similar fault cannot duplicate on the other ADIRU type, or at least would not lead to such an adventure.
But for the Litton ADIRU, even if the probability of re-occurrence is very low, they want to make sure the crew will have the proper tool, not to totally eliminate the risk, but at least to significantly reduce the exposure time to that risk : That’s the reason for the Operations Engineering Bulletin publication.
Some Airbus automatisms, in my view, are one step too far.
Surely wonderful on paper as well as in real time when everything is by the book, but can also badly bite and so by complete surprise as lately demonstrated.
Put back QF72 in a simplified FBW A330 version, one with NO protection and the crew had ample time to deal with the defective equipment.
Still, I am confident Airbus and Litton will find a technical solution to the issue, but for now …
Follow the OEB if you want to be protected from the protection !
People will shoot me for doing so, but this event brings me back 20 years earlier :
Habsheim was the first case when flight controls responded in an unexpected way.
But for the Litton ADIRU, even if the probability of re-occurrence is very low, they want to make sure the crew will have the proper tool, not to totally eliminate the risk, but at least to significantly reduce the exposure time to that risk : That’s the reason for the Operations Engineering Bulletin publication.
Some Airbus automatisms, in my view, are one step too far.
Surely wonderful on paper as well as in real time when everything is by the book, but can also badly bite and so by complete surprise as lately demonstrated.
Put back QF72 in a simplified FBW A330 version, one with NO protection and the crew had ample time to deal with the defective equipment.
Still, I am confident Airbus and Litton will find a technical solution to the issue, but for now …
Follow the OEB if you want to be protected from the protection !
People will shoot me for doing so, but this event brings me back 20 years earlier :
Habsheim was the first case when flight controls responded in an unexpected way.
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Perhaps unfair of me to comment, as unlike you I have no professional experience of Scarebusses, but this surely won't be the last time that man is surprised by this increasingly complicated system. It is all very well electronically engineering more and more levels of protection/ intervention, but it doesn't half put the onus on swift thinking and systems knowledge (perhaps in excess of the Type Rating course? ) when things do go wrong.
I don't wish to imagine the joys to come when these beasties get older and fall into the hands of "less well known carriers in exotic climes".
Wiggly Amps & Wobbly Aircraft OOer. . .
I don't wish to imagine the joys to come when these beasties get older and fall into the hands of "less well known carriers in exotic climes".
Wiggly Amps & Wobbly Aircraft OOer. . .
Already in those times my friend, Garuda already operate the A330, have done for a long time.
And a lot of Airlines in mainland China and Taiwan and Korea blah blah blah
They seem to cope ok so far.
And a lot of Airlines in mainland China and Taiwan and Korea blah blah blah
They seem to cope ok so far.
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Wait till they get older and end up with less well known operators, although in all fairness the oldest 320's aren't exactly yung. (sorry actually meant young, freudian slip)
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Some more info.......US military link to Qantas jet plunge | Herald Sun
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I REALLY have a lot of problems with how anybody, having even the remotest notions of physics, and aeronautical engineering, can believe a high-power VLF communication station can inject enough energy into an aircraft system (ADIRU... and the AoA sensor if you want to be picky), to cause such a fault.
We're talking about an aircraft at 37000 ft, i.e., about 7 miles away, even if right overhead.
KISS, please.
Electromechanical and electronic faults DO happen......
We don't need little green man to explain them all.
CJ
We're talking about an aircraft at 37000 ft, i.e., about 7 miles away, even if right overhead.
KISS, please.
Electromechanical and electronic faults DO happen......
We don't need little green man to explain them all.
CJ
The base uses powerful low frequency radio transmissions to US Navy and Australian Navy ships and submarines.
It is understood to be the most powerful transmission station this side of the globe and includes 13 radio towers, the tallest of which is 387m tall.
The base is named the Harold E. Holt communications station after the former Australian Prime Minister.
ATSB spokesman David Hope confirmed the new line of inquiry today, after "several" groups had raised it as a possibility.
It is understood to be the most powerful transmission station this side of the globe and includes 13 radio towers, the tallest of which is 387m tall.
The base is named the Harold E. Holt communications station after the former Australian Prime Minister.
ATSB spokesman David Hope confirmed the new line of inquiry today, after "several" groups had raised it as a possibility.
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I believe Harold would have disturbed ADIRU 2 and ADIRU 3 as well ...
Whatever the reason which caused ADIRU 1 to fault, the airplane took control on the base of that single piece of equipment dysfunction, and so in an ugly way.
What a chock for the crew ... curious to hear the CVR.
Also curious to know if ADR1 has been switched OFF after the second upset or did the spikes just quit ?
What happen if a spike value is generated in final …
Whatever the reason which caused ADIRU 1 to fault, the airplane took control on the base of that single piece of equipment dysfunction, and so in an ugly way.
What a chock for the crew ... curious to hear the CVR.
Also curious to know if ADR1 has been switched OFF after the second upset or did the spikes just quit ?
What happen if a spike value is generated in final …
Quote from ChristiaanJ:
I REALLY have a lot of problems with how anybody, having even the remotest notions of physics, and aeronautical engineering, can believe a high-power VLF communication station can inject enough energy into an aircraft system (ADIRU... and the AoA sensor if you want to be picky), to cause such a fault.
We're talking about an aircraft at 37000 ft, i.e., about 7 miles away, even if right overhead.
[Unquote]
Hi Christian,
The trouble with you electronics engineers is that you are too impatient with us mere mortals! I note only that the A330's altitude was probably less than one wavelength of the LF transmission, so a close flyby could place the aircraft exactly one wavelength away on two occasions over a period of less than two minutes. That may or may not be relevant to RFI (probably the latter), but it makes one think.
Most of us have little understanding of the mechanism whereby an electromagnetic wave can induce EMF in a wire, and the latter's possible effects. We are also reluctant to pursue a crash course in elementary electronics. Assuming you have some idea of the order of power of a transmission that is capable of propagating a receivable ground wave across (and under?) thousands of miles of oceans, could you hazard back-of-the-envelope figures of what effect this radiation might have on a (say) 10-metre cable about 15km slant-range from the transmitter array? [I'm suggesting, for sake of argument, that the AoA probe might be about 10m from the ADIRU.]
Could you also tell us if the Faraday cage of the fuselage structure would be even more effective against VLF than shorter wavelengths?
Chris
I REALLY have a lot of problems with how anybody, having even the remotest notions of physics, and aeronautical engineering, can believe a high-power VLF communication station can inject enough energy into an aircraft system (ADIRU... and the AoA sensor if you want to be picky), to cause such a fault.
We're talking about an aircraft at 37000 ft, i.e., about 7 miles away, even if right overhead.
[Unquote]
Hi Christian,
The trouble with you electronics engineers is that you are too impatient with us mere mortals! I note only that the A330's altitude was probably less than one wavelength of the LF transmission, so a close flyby could place the aircraft exactly one wavelength away on two occasions over a period of less than two minutes. That may or may not be relevant to RFI (probably the latter), but it makes one think.
Most of us have little understanding of the mechanism whereby an electromagnetic wave can induce EMF in a wire, and the latter's possible effects. We are also reluctant to pursue a crash course in elementary electronics. Assuming you have some idea of the order of power of a transmission that is capable of propagating a receivable ground wave across (and under?) thousands of miles of oceans, could you hazard back-of-the-envelope figures of what effect this radiation might have on a (say) 10-metre cable about 15km slant-range from the transmitter array? [I'm suggesting, for sake of argument, that the AoA probe might be about 10m from the ADIRU.]
Could you also tell us if the Faraday cage of the fuselage structure would be even more effective against VLF than shorter wavelengths?
Chris
Last edited by Chris Scott; 26th Oct 2008 at 16:28. Reason: Last paragraph added
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Could you also tell us if the Faraday cage of the fuselage structure would be even more effective against VLF than shorter wavelengths?
Last edited by Luap; 27th Oct 2008 at 01:18. Reason: typo
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The base uses powerful low frequency radio transmissions to US Navy and Australian Navy ships and submarines.
Maybe nobody thought of such low frequency high energy radio transmissions when dsesigning the electromagnetic shielding of the computers ?
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the vlf tx
the tx in question is I believe 19.8 khz.ABC radio in Melbourne for example is 774khz so that will give you some idea how low it is.
this theory has been discussed at some length on this or another thread dealing with the same incident.what hirf freqs are used for testing no idea.
the wavelengths at these low freq's are enormous (15 kms)and for a number of reasons most of us have discarded the theory.
Does not mean we are correct,just means some of us agree.
for "it" to get in and selectively target one system would indicate big shielding and filtering issues.
vlf is not new and I could not believe filtering and shielding against any rf that could interfere would be dealt with.Shielding and LC ccts are very effective against rfi.
electronics maufacturers also need to deal with the harmonics of signals also the beat freq's as well as the fundamentals freq's.
Whilst other info would be superimposed , for example, on the carrier or sidebands of the fundamental the strength of those is normally less and refer to the above shielding and filtering of unwanted freq's.
this theory has been discussed at some length on this or another thread dealing with the same incident.what hirf freqs are used for testing no idea.
the wavelengths at these low freq's are enormous (15 kms)and for a number of reasons most of us have discarded the theory.
Does not mean we are correct,just means some of us agree.
for "it" to get in and selectively target one system would indicate big shielding and filtering issues.
vlf is not new and I could not believe filtering and shielding against any rf that could interfere would be dealt with.Shielding and LC ccts are very effective against rfi.
electronics maufacturers also need to deal with the harmonics of signals also the beat freq's as well as the fundamentals freq's.
Whilst other info would be superimposed , for example, on the carrier or sidebands of the fundamental the strength of those is normally less and refer to the above shielding and filtering of unwanted freq's.
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Red Herring
Maybe nobody thought of such low frequency high energy radio transmissions when dsesigning the electromagnetic shielding of the computers ?
This base is NOT new and it lies directly beneath the flightpath from DPS-PER. As far as I am aware, none of these flights have fallen from the sky over the years?
Theres a bit of official information on the net and some research papers published but how this stuff could affect an aircraft is really unknown.
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Chris Scott asked for some back-of-the-envelope figures.
I'll start with some very simple assumptions, then we'll see if there are any major errors in those assumptions.
Published frequency 19.8 kHz, say 20 kHz = wavelength 15 km.
Published power 1 MW (1,000,000 Watt = 10^6 Watt). Let's assume this is radiated power rather than the transmitter power.
Transmitter is a "point source", radiating evenly into a hemi-sphere above the station.
Aircraft at 11 km high (36000 ft) and a slant range of 16 km (45° above the horizon).
Aircraft is a 777, which we can consider as a 60 m long and 6 m thick cylinder, presenting at most a surface of 360 m² to the transmitter.
Surface of the hemi-sphere = 2 * pi * r^2 = 6.3*(16000)^2 = 1600 * 10^6 m². With 10^6 Watts radiated, the power at location of the aircraft is 1/1600 W/m², so the entire aircraft structure intercepts about 0.225W, about 1/6th of the power of the bulb in a typical flashlight/torch.
I'll have to leave it to an antenna expert to tell us exactly what voltages and currents are induced in a cylinder that is a minute fraction of the wavelength, how much will be simply dissipated in the skin (skin effect, Faraday cage effect) and how much of it would be detectable inside.
One of my assumptions is that the transmitter radiates evenly into a hemisphere. In practice, we see huge antenna farms on the photos, with dimensions in the order of half a wavelength, so we can expect the radiation to be at least somewhat directional in both the horizontal and vertical plane. But it seems unlikely to me, that gains of more than 3 to 4 are obtained in any one direction.
My other assumptions of course are the actual distances: 16 km slant range and 11 km height and 45° above the horizon. Since there is an r_squared involved, reducing the slant range to 11 km will roughly double the power. I haven't done that because usually the "overhead" power of a transmitter installation is less than that at lower radiation angles.
So OK, even if I'm out by a factor 10 or so, the total power arriving on the skin of the entire aircraft is still about that of the bulb in a flashlight. Only a fraction of that will get "inside". To actually affect the electronics (not the radio, but the electronics such as the ADIRU), something already has to be very seriously wrong with those electronics.
CJ
I'll start with some very simple assumptions, then we'll see if there are any major errors in those assumptions.
Published frequency 19.8 kHz, say 20 kHz = wavelength 15 km.
Published power 1 MW (1,000,000 Watt = 10^6 Watt). Let's assume this is radiated power rather than the transmitter power.
Transmitter is a "point source", radiating evenly into a hemi-sphere above the station.
Aircraft at 11 km high (36000 ft) and a slant range of 16 km (45° above the horizon).
Aircraft is a 777, which we can consider as a 60 m long and 6 m thick cylinder, presenting at most a surface of 360 m² to the transmitter.
Surface of the hemi-sphere = 2 * pi * r^2 = 6.3*(16000)^2 = 1600 * 10^6 m². With 10^6 Watts radiated, the power at location of the aircraft is 1/1600 W/m², so the entire aircraft structure intercepts about 0.225W, about 1/6th of the power of the bulb in a typical flashlight/torch.
I'll have to leave it to an antenna expert to tell us exactly what voltages and currents are induced in a cylinder that is a minute fraction of the wavelength, how much will be simply dissipated in the skin (skin effect, Faraday cage effect) and how much of it would be detectable inside.
One of my assumptions is that the transmitter radiates evenly into a hemisphere. In practice, we see huge antenna farms on the photos, with dimensions in the order of half a wavelength, so we can expect the radiation to be at least somewhat directional in both the horizontal and vertical plane. But it seems unlikely to me, that gains of more than 3 to 4 are obtained in any one direction.
My other assumptions of course are the actual distances: 16 km slant range and 11 km height and 45° above the horizon. Since there is an r_squared involved, reducing the slant range to 11 km will roughly double the power. I haven't done that because usually the "overhead" power of a transmitter installation is less than that at lower radiation angles.
So OK, even if I'm out by a factor 10 or so, the total power arriving on the skin of the entire aircraft is still about that of the bulb in a flashlight. Only a fraction of that will get "inside". To actually affect the electronics (not the radio, but the electronics such as the ADIRU), something already has to be very seriously wrong with those electronics.
CJ
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Let me add some anecdotical "evidence".
Have a careful look at the forward part of the fin. See the two green-brown vertical "slashes"? They are indeed two "slashes" into the metal structure, covered by "radio-transparent" fibreglass, and for some reason never painted over until nearly the end of the flight test programme. They are there on all Concordes, but painted over on the others.
They are the HF (high-frequency) slot antennas.
In the olden days, a wire strung from the cockpit back to the fin would do the job, but that wasn't really acceptable in the supersonic era....
But a slot cut into a metal structure, closed on the inside, and connected to a radio transmitter, will radiate HF energy.
So that was the solution on Concorde, and you will find similar solutions on most present-day airliners.
However.... a radio engineer will tell you that such a slot aerial at HF frequencies is not exactly the most efficient, and will set up very high high-frequency currents in the surrounding structure.
As happened on Concorde.
So.... here we had an 100W HF transmitter, directly connected to the airframe, and trying to radiate at least some of its energy.... but some it just got dissipated in the structure (SWR not quite one, for the experts).
As it so happened, the yaw rate gyros, part of the autostab system, were mounted precisely in this area.
Guess... when we started to test the HF radios on longer-range flights, we found the tail wagged and twitched a bit whenever somebody talked on the HF radio....
Even so, it took us some time to correlate the twitches with the autostab. A small filter solved the problem.
Moral of the story?
Nearly forty years ago it took us 100W injected directly into the structure of an aircraft (still being flight tested, mind you) to provoke a mere 'twitch' in an analog control system.
Less than a milliWatt/m² of VLF impacting on an aircraft, from a facility overflown regularly, and suddenly causing a malfunction in an electronics unit (ADIRU or AoA sensor)? Try another one, this one has bells on.
CJ
Have a careful look at the forward part of the fin. See the two green-brown vertical "slashes"? They are indeed two "slashes" into the metal structure, covered by "radio-transparent" fibreglass, and for some reason never painted over until nearly the end of the flight test programme. They are there on all Concordes, but painted over on the others.
They are the HF (high-frequency) slot antennas.
In the olden days, a wire strung from the cockpit back to the fin would do the job, but that wasn't really acceptable in the supersonic era....
But a slot cut into a metal structure, closed on the inside, and connected to a radio transmitter, will radiate HF energy.
So that was the solution on Concorde, and you will find similar solutions on most present-day airliners.
However.... a radio engineer will tell you that such a slot aerial at HF frequencies is not exactly the most efficient, and will set up very high high-frequency currents in the surrounding structure.
As happened on Concorde.
So.... here we had an 100W HF transmitter, directly connected to the airframe, and trying to radiate at least some of its energy.... but some it just got dissipated in the structure (SWR not quite one, for the experts).
As it so happened, the yaw rate gyros, part of the autostab system, were mounted precisely in this area.
Guess... when we started to test the HF radios on longer-range flights, we found the tail wagged and twitched a bit whenever somebody talked on the HF radio....
Even so, it took us some time to correlate the twitches with the autostab. A small filter solved the problem.
Moral of the story?
Nearly forty years ago it took us 100W injected directly into the structure of an aircraft (still being flight tested, mind you) to provoke a mere 'twitch' in an analog control system.
Less than a milliWatt/m² of VLF impacting on an aircraft, from a facility overflown regularly, and suddenly causing a malfunction in an electronics unit (ADIRU or AoA sensor)? Try another one, this one has bells on.
CJ