Claims that RVSM system is higher risk than previously thought

[Memetic]

An article at : http://www.newscientist.com/news/news.jsp?id=ns99994369

Claims the new RVSM system is more risky than previously calculated.

It starts:

"European airspace safety rules 'flawed'

19:00 12 November 03

A leading air safety expert is warning of a serious flaw in the risk analysis undertaken before rules were changed to halve the vertical distance between planes flying over Europe. He says this means the risks of flying in European airspace are not as low as the public is being led to believe. ..."


I'm not qualifed to even begin to comment but thought it might be of interest to this forum.

Memetic

[Daysleeper]

interesting that one mid air per 150 years is acceptable losses. we're going to have to work some to achieve that level of reliability.

[PPRuNe Towers]

Written by Peter Ladkin who's been a PPRuNer and contributed for many years on the excellent Bluecoat forum.

I welcome his research, which may seem pretty deep and esoteric to us at the pointy end, as it is the only thing that will counter the the 'boffins' who do all the ATC theoretical and statistical work. They really are on a planet of their own and need a good hard slap - aka reality check.

This is not a dig at ATCers who work at the glass face:ok: :ok:

Regards
Rob

[BlueEagle]

The following UK AIB bulletin relates to an incident over the North Atlantic in year 2000 and may be of interest as it highlights a possible RVSM safety issue,

The Bulletin (http://www.dft.gov.uk/stellent/groups/dft_avsafety/documents/page/dft_avsafety_501275.hcsp)

[alf5071h]

The specific problem cited in New Scientist was concern over “the unpredictability of the response by pilots and ATC to warnings from ACAS”. To an extent this is true for ACAS as shown by the initial findings of the Swiss accident and the differing responses posted to this site relating crews understanding and reaction to an ACAS warning, but the problem also applies to much of today’s modern technology. The unpredictability of crew actions could also be seen as misunderstandings by crew of the designer’s intent or the operational assumptions made about the equipment. Many gaps in these areas are due to poor communications between design, certification, and the operation; the in-service problems result from the differing training requirements and standards.

Examples can be seen with auto flight systems, where some crews may not appreciate what is happening, and many flavors of FMS that can construct routings in just as many different ways. Modern radar systems that define so clearly the edge of hazardous weather that crew now fly closer to storm cells than they use to, often forgetting about the other hazards to flight such as anvil/outflow ice and turbulence. TAWS that depict terrain with graphic quality equating to a map, so good that some crew will use TAWS as primary navigation, yet the source of the TAWS navigational position accuracy may be no better (or reliable) than the navigation aid that could cause a terrain encounter. Wind shear warning systems that we are told as so good that we can ignore the common sense of not taking off with cb activity, etc,etc.

“Technology has become so sophisticated that the limiting factors are less technical and now more social, cultural, and often political” ‘Nathan Shedroff ‘ Experience Design.

IMHO this quote reinforces the need to close the assumption gaps between design and operation (communications and knowledge) and to focus on good technical and CRM/airmanship training.

[error_401]

Just keep in mind:

Below FL 290 it has always been 1000 feet.

The mid air collisions did not happen because of a mismatch or a deviation in altitude but because of climbing throug assigned altitudes, deviation from procedures (ueberlingen, germany, accident mentioned in the study could have avoided when both crews had used their TCAS) or even using exactly the same altitude (german airforce with us airforce on west coast of africa - so much for how precise the equipment is...)

So this discussion is really academic as in real life the real dangers are probably in the approach areas where aircraft climb/descend throug all levels. Would a separation of 2000 feet below FL 290 help? I doubt it.

[Captain Phaedrus]

...and the status of ACAS in Air Law is...

...is...

...is non-existent.

...and bear in mind that a pilot who deviates from an ATC clearance or instruction assumes absolute responsibility for the safe conduct of the flight. (ref Ueberlingen, where the B757 crew deviated from their clearance whilst the Bazik crew did as they were told - there's a strong argument that they were in the right).

What about the Rules of the Air? 'Aircraft which has the other on its right' etc?

Remember ATC have no responsibility to prevent collisions between aircraft, in law.

[Captain Stable]

Phaedrus - sorry, but almost all your post is incorrect.

TCAS does have legal backing. It depends, of course, on what you consider to be "Air Law".

And the Russian crew did not act correctly. The DHL crew did. And ATC have a duty of care towards aircraft they are controlling. Their legal responsibilities may lie in Common Law rather than statute, but they most certainly do have a responsibility to do all they reasonably can to prevent collisions.

[Captain Phaedrus]

Capt Stable,

Would you care to enlighten me as to where ACAS is encapsulated within the regulatory framework, and to illustrate how common duty of care would override the provisions of the Tokyo Convention, please? And then, show me where there is a statement to the effect that ATC are responsible for preventing collisons in the relevant instruments of an ICAO contracting state?

My post was deliberately worded to allow some doubt and room for interpretation; yours was not.

You could even point out an ACAS statement from a regulator which uses the word 'must' (outwith the negative connotation), though I fear there is not one.

Whether the DHL crew acted 'correctly' depends upon your viewpoint and brief. I might argue that they failed to maintain a good lookout, they failed to comply with the Rules of the Air with regard to the prevention of collisions, and they did not react promptly and effectively in the light of the information presented to them by their instrumentation.

If the Rules of the Air had been observed, there would have been no collision (very good VMC prevailed on the night of the accident).

A similar event in the UK (which whilst giving rise to a near miss did not lead to a collision) the following day also illustrates my point (DHC8 vs EMB145 over Wales).

We need a joined-up approach to safety from legislators, through regulators, to operators. This is denied us at the moment, and we should fight for it.

(Please understand that my post and references to the tragic events at Ueberlingen are by way of academic discussion of the aetiology of the collision, and that I am, as I am sure you are, very deeply saddened at the loss of life there).

[Captain Stable]

52 On any flight on which an airborne collision avoidance system is required by paragraph 1 of Schedule 5 to this Order to be carried in an aeroplane, the system shall be operated:

(a) in the case of an aircraft to which article 31 applies, in accordance with procedures contained in the Operations Manual for the aircraft;

(b) in the case of an aircraft registered in the United Kingdom to which article 31 does not apply, in accordance with procedures which are suitable having regard to the purposes of the equipment; or

(c) in the case of an aircraft which is registered elsewhere than in the United Kingdom, in accordance with any procedures with which it is required to comply under the law of the country in which the aircraft is registered.

(http://www.hmso.gov.uk/si/si2000/20001562.htm#52)

You will find that Schedule 5 lists ACAS equipment as Scale J.

You can speculate all you like about whether, had the DHL crew acted differently, there would have been an accident or not. You need to understand the structure of an accident/error chain - it is clear that you don't. I suggest you read up on it before making allegations as you do above.

Furthermore, if Car A veers out of the correct lane, into the path of an oncoming car and all in both vehicles are killed, it is not enough for the police to say that the driver of Car B should have veered into the opposite lane. If he had, there would have been no accident. Yet that is what you are suggesting.

The rules for use of TCAS are quite clear. You follow its instructions. If they differ from your clearance, you follow the TCAS, and alert ATC as and when you can. This is very simple. It is not open to misunderstanding, misinterpretation or debate.

The Russian crew failed to follow the instructions their TCAS gave them and elected to follow ATC instructions instead.

If you want a joined-up approach to safety, you need to ensure that you understand what the regulations are, and you need to practise them. Until you understand the method of use of TCAS, maintaining instead that the Russian crew acted correctly and the DHL crew incorrectly, you cannot be part of such a joined-up approach.

[Captain Phaedrus]

Captain Stable,

First, I take exception to your suggestion that I don't understand cause, effect, and the 'chain'. I have discussed this with Prof Ladkin, Prof Reason, and others at their level of expertise, and they were quite happy to listen to what I had to say... As a professional safety investigator and trainer, I don't accept your allegation. (By the way, I made no allegation - I put forward a hypothesis. The two actions are quite different, and YOU should be able to distinguish between them).

Your motoring analogy is not appropriate. A correct analogy would be approaching a roundabout and seeing another car coming on your right hand side. You should give way to it. Aproaching head on in motor cars is quite another matter.

I am well aware of the regulatory provision for ACAS as you copy it. Perhaps you would now like to dig into the Tokyo convention, and provide us with chapter and verse on ATC clearences and the requirements to comply, whilst also considering that the words 'Must' and 'Shall' are absent in all ACAS literature provided by operating companies that I have ever seen?

We should note, by the way, that 'operating the system' is quite separate from 'reacting to it's outputs'.

Could you also explain how aircraft may become exempt the Rules for Avoiding Aerial Collisions, by dint of having ACAS fitted? I am horrified at the number of pilots who, in a simulated TCAS encounter, are happy to fly blindly on waiting for TCAS to save them, despite being able to 'see' the intruder aircraft on the visual. The only thing more horrfiying is the number of instructors who take issue with them if they decide to take action prior to an RA...

[Anthony Carn]

Tis confused I am....

You halve the vertical separation of aircraft at high altitude.....

.....and you wonder if it's less safe ! :rolleyes:



If you work out the separation of two aircraft above 30,000 ft steaming head on at almost 1000 knots, assuming worst case errors in their altimeters, then it makes you stop and think !

This assumes that commercial pressures are'nt forcing/"persuading" one or both Commanders to ignore "slight" altimeter deviations from laid down limits. Going "non RVSM equipped" can be a real pain, to put it mildly.



Or am I missing something subtle here ? :confused:

[Semaphore Sam]

Bad logic, I think, Mr. Carn

'confused I am....
You halve the vertical separation of aircraft at high altitude.....
.....and you wonder if it's less safe !
......................................
Or am I missing something subtle here ? '

Not so subtle...by that logic, 4000' is better than 2000', 8 better than 4, but then all aircraft must be fit into very few flight levels/alts, leading to a few crowded, dangerous flight levels, and lots of safe, empty space between. The question is, what is the minimum safe separation by alt/fl; 1000' with current altimetry seems to fit the bill, and provide safe separation; after a few years, 2000' above 290 will be seen to be highly unsafe due to over-crowding. Something had to be done; it has been done, & I, for one, feel safer. Sam.

[BlackSword]

Reducing vertical spacing on oceanic has obvious benefits for better altitude etc but has always left me puzzling.........

Why was RVSM introduced (back when) in oceanic airspace to solve capacity problems, when reducing lateral spacing was simpler and safer to do? Especially, when one then has to (sometimes hurriedly) adjust to non-RVSM when leaving oceanic?

It seems (to me) that it was done as an experiment, to gain practical experience in RVSM before introducing it in European airspace. Odd, given the potential TCAS problems and the lack of communications in oceanic.

By the way, I do not share everyone's confidence in the accuracy of baro at 35,000. Scientifically speaking, that is.