Causal risk models of air transport - NLR-ATSI

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Airways 25 , although this is exceptional. Accident prevention and safety management therefore are as important as ever, despite the high level of safety that has been achieved. The very success of the aviation system in terms of safety performance makes it difficult to determine the linkage between actions and decisions and safety outcomes. Because accidents are so rare it is impossible to determine directly whether actions or decisions had any effect on safety. Hence there is no proper feedback loop from day-to-day operations to safety decision-making [Amalberti 2001]. In other words, the fix and fly approach is no longer effective. Yet new hazards are constantly lurking due to such factors as insertion of new technologies, trends in the economy and change in the regulatory environment. To maintain and improve the current level of safety, there is a need for an aviation safety performance evaluation methodology that is not based on analysis of fatal accidents and hull losses alone. Such a methodology should include a safety evaluation construct, safety hazard identification and risk analysis, safety performance measures and risk indicators and safety diagnostic procedures [FAA 2004]. A causal risk model can play a central role in such methodology. In conclusion, the main drivers for aviation safety improvement have been technological development and the industry’s practice of thorough accident investigation and subsequent remedial actions. Because of the high level of safety, the latter approach is no longer effective and there is need for a new safety performance evaluation methodology, of which a causal risk model could be a central part. We have also seen how in the past the regulatory authorities shifted from prescribing detailed requirements to a quantitative target level of safety, and to requiring the industry to demonstrate numerically that the target is obtained. For parts of the aviation system this is already done, and existing methods for analysis may suffice, but there is a need now to also analyse the aviation system as a whole. This is another potential application of a causal risk model, which requires the model results to be quantitative and reproducible. The causal risk model should therefore: • Include risk indicators, • Provide reproducible results, • Represent the aviation system as a whole, and • Have quantitative model output. The Concorde disaster The BAC/Sud-Aviation Concorde aircraft was the embodiment of aeronautical progress. With a cruising speed of more than twice the speed of sound it was twice as fast as all other commercial aircraft. To attain these speeds, the shape of the aircraft was special as well, with an elegantly pointed nose and beautifully curved ogival delta wing platform. The shape of the wing was in fact a compromise between the requirement to be able to fly at supersonic speeds and still provide satisfactory characteristics at low speed for take-off and charter operator, most people on-board were German tourists. The accident was initiated by incorrect airspeed indications due to a blocked pitot tube [JIAA 1996]. 25 On 14 August 2005, Helios Airways flight 522, a Boeing 737-300 crashed near Athens in Greece on a flight from Larnaca, Cyprus. All 121 occupants were killed. The immediate cause of the accident was flight crew incapacitation due to hypoxia. Helios Airways was a low fares carrier, established in 1999. At the time of the accident, Helios was operating four aircraft and conducted flights out of Larnaca and Paphos, Cyprus [AAIASB 2006]. 40
landing. Nevertheless, Concorde’s typical take-off speed of 200 kts is approximately 35% higher than that of other commercial jet aircraft. These high take-off speeds are more demanding to the tyres, and the rate of tyre bursts for Concorde has always been relatively high at one occurrence per 1,500 cycles rather than the one occurrence in 100,000 cycles which is the rate for modern airliners such as the Airbus A340 [BEA 2001]. Modifications such as strengthened tyres led to a reduction in the tyre failure rate, but it still remained relatively high. This was not considered to be a major safety hazard until 25 July 2000, when during take-off from runway 26R at Roissy Charles de Gaulle Airport, shortly before rotation, the front right tyre of the left landing gear of Air France Concorde F-BTSC ran over a strip of metal which had fallen from another aircraft. The tyre exploded and debris was thrown against the underside of the wing, leading to a rupture of one of the wing’s integral fuel tanks. A major fire, fuelled by the leak, broke out immediately under the left wing. Ingestion of tyre debris and hot gases caused malfunctions to the engines on the left wing, and the fire destroyed control surfaces at the wing’s trailing edge. The flight crew had no possibility to recover from the catastrophic situation, and the aircraft crashed less than two minutes after take-off. All 109 passengers and crew members, as well as 4 people on the ground, were killed. Previous to this accident, there had been five tyre burst events on Concorde which had caused structural damage to fuel tanks. Reinforcement of the lower wing was considered after the first incident, but it was considered unnecessary [BEA 2001]. After the accident, Air France immediately grounded its Concorde fleet, and although British Airways (the sole other operator of Concorde) continued operating the aircraft for a few weeks, the CAA ordered the British fleet to be grounded as well. An extensive modification program including the fitment of Kevlar lining to key fuel tanks and installation of strengthened tyres was executed, and the Certificate of Airworthiness was re-issued 14 months after the accident. For commercial reasons, Concorde was retired in October 2003. Figure 7: Concorde. 41
Page 1: Causal risk models of air transport
Page 4 and 5: Dit proefschrift is goedgekeurd doo
Page 6 and 7: Acknowledgements A PhD study has be
Page 8 and 9: Chapter 6. Risk models in other ind
Page 10 and 11: List of abbreviations AC Advisory C
Page 12 and 13: STAR Standard Arrival Route STCA Sh
Page 14 and 15: esults of such models are possible
Page 16 and 17: processes? The second dimension is
Page 18 and 19: Chapter 2. Fundamentals of risk Bef
Page 20 and 21: Figure 1: Voluntary exposure to ris
Page 22 and 23: Y (RDC) [km] 495 490 485 480 475 47
Page 24 and 25: achieved (i.e. an aspirational targ
Page 26 and 27: accidents’ because these accident
Page 28 and 29: e restricted to ‘objective’ ris
Page 30 and 31: is irrelevant. The fire-fighter wil
Page 32 and 33: In this example, the drug appears b
Page 34 and 35: ender the model outcome too uncerta
Page 36 and 37: If we adopt Leveson’s [2004a] sys
Page 38 and 39: models. A strategy for avoiding thi
Page 40 and 41: Number of accidents per 100,000 fli
Page 42 and 43: After World War II aviation became
Page 44 and 45: about 100 potential system failure
Page 48 and 49: Douglas DC-10; an aircraft with a t
Page 50 and 51: of small airlines that went bankrup
Page 52 and 53: Throughout the service life of an a
Page 54 and 55: an inverse relation should exist be
Page 56 and 57: Safety versus the environment: the
Page 58 and 59: A causal risk model could support t
Page 60 and 61: adequate levels of safety in the ci
Page 62 and 63: also because of the large amount of
Page 64 and 65: met. The explanatory material empha
Page 66 and 67: Article 8 of the Seveso Directive (
Page 68 and 69: 4.4. Summary of user requirements a
Page 70 and 71: Grouped by type of requirements, th
Page 72 and 73: Representation of regulation Regula
Page 74 and 75: characteristics make test pilots ve
Page 76 and 77: Table 3: List of fatal flight test
Page 78 and 79: 4.5. User expectations: lessons fro
Page 80 and 81: helpful tool. This will have to be
Page 82 and 83: is to have a top-level representati
Page 84 and 85: Chapter 5. Examples of aviation saf
Page 86 and 87: therefore the approach cannot be co
Page 88 and 89: N az ⎡ ⎪⎧ 2λ y& z ⎪⎫ ⎤
Page 90 and 91: acceptable. The question, scope and
Page 92 and 93: Chapter 6. Risk models in other ind
Page 94 and 95: support [Paté-Cornell & Dillon 200
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Techniques that have been used in t
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airline passengers face. A complica
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problems, already well accepted in
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computationally more intensive. A d
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BASIC EVENT - A basic initiating fa
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fault trees best represent the logi
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Bayesian Belief Nets are convenient
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The approach for CATS was with q =
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PDPs can be used to construct model
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analysis is repeated for each secti
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Chapter 8. Quantification The causa
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hole’ is impossible to tell unles
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An example of a complex issue for w
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determined, given the results of th
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Indeed it can be misleading to thin
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determine what preventive action ma
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to provide quantitative data to the
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data the most accurate and detailed
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It takes years to set up and conduc
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Another problem with the use of aud
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Ambiguity in the classification sys
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vulnerable to differences in interp
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Chapter 9. Modelling challenges In
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considerable procedure guidance, do
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Procedures Availability Error proba
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9.2. Modelling safety management IC
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phenomenon 73 . As a matter of fact
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shift changeovers or when an aircra
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will be crossed if no action is tak
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capsule, Grissom realized that he w
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According to this model, ‘fatigue
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Archetype accident example 1: Take-
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Table 8: Runway overrun accidents a
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evolution 78 . An advantage of this
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systems. They then provide a conven
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that the rest contains no ‘new’
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quick handling by the flight crew a
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Cumulative probability 1 0.9 0.8 0.
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speed 86 for the 500 ft altitude ga
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Probability density 0.0008 0.0007 0
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This example concerns an approach f
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10.6. Conclusions for this section
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accident chains in which the ultima
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esults are being used in a certific
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are not ‘calibrated’. These asp
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equirements. The degree to which dy
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this may seem to be an oversimplifi
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Main research question: What does c
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References AAIASB. (2006). Accident
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BEA. (2001). Accident on 25 July 20
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Carpenter, M.S., Cooper, L.G., Glen
Page 198 and 199:
EAI. (2002). Review of Causal Model
Page 200 and 201:
FAA. (1995a). Aviation safety actio
Page 202 and 203:
Hale, A.R. (2000). Railway safety m
Page 204 and 205:
IATA. (2008b). IOSA Standards Manua
Page 206 and 207:
Khatwa, R., Roelen, A.L.C. (1996).
Page 208 and 209:
Lloyd, E. (1980). The development o
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Nijenhuis, W.A.S., Spek, F., Moelek
Page 212 and 213:
Onisko, A., Druzdzel M.J., Wasyluk,
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around airports, Part 1: Main repor
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Simons, M., Valk, P.J.L. (1998). Ea
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Tweede Kamer. (2003b). Toekomst van
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Summary Aviation safety is so well
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existing data bases. Preferably the
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verder verbeteren daarvan, zijn er
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internationale regelgever zoals EAS
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LPG [Tweede Kamer 1983], which set
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of this a situation has been create
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Holding En-route Approach Go-around
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Approximately 5 minutes prior to de
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cockpit announcing flight parameter
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The ground controller then takes ov
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aircraft input will occur. They wil
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Basic principles for the design, co
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egulation became evident and the In
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its functions was to develop and ad
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the delivery systems determines a m
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