Airworthiness

Nurcombe, C. (2005) Airbus cabin air quality-still the best Airbus Technical Magazine FAST-Flight, Airworthiness, Support, Technology 37, pp. 7-10. 

UK Civil Aviation Authority, Molybdenum Disulphide Lubricants - Effect on Turbine Engines, Airworthiness Notice No. 12, Appendix No.38, (16 March, 1988). 

Cawley, N. R., Harlow, D. G., and Wei, R. P., Probability and Statistics Modeling of Constituent Particles and Corrosion Pits as a Basis for Multiple-Site Damage Analysis, FAA-NASA Symposium on Continued Airworthiness of Aircraft Structures, DOT/FAA/AR-97/2, II, National Technical Information Service, Springfield, VA (1997), 531-542. 

Wei, R. P., and Harlow, D. G., Probabilities of Occurrence and Detection, and Airworthiness Assessment, Proceedings of ICAP 99 Symposium on Structural Integrity for the Next Millennium, Bellevue, WA July 12-16,1999. 

The example chosen here is that of inspection of civil aircraft as part of the system for assuring the public that airworthiness is maintained throughout the service life of airframes, avionics, and aircraft structures. It is part of a maintenance process and is typical of many transportation applications, such as for maritime transport, heavy goods vehicles, or even the space shuttle. 

Airworthiness of civil aircraft depends upon a process by which a team composed of aircraft manufacturers, regulators, and one or more airlines predicts possible system failures. This process. Maintenance Steering Group 3 (MSG-3), considers possible failure pathways (e.g., in structures, controls, avionics) and for each pathway determines a recovery strategy. For structural failure, this may be replacement after a fixed service life, regular inspection to ensure detection, or an indication to crew of the malfunction. The concern here is with the reliability of the primary failure recovery system for aircraft structural inspection regular inspection to ensure detection. 

This whole reliability assurance process thus rests upon an inspection system that checks both points where malfunctions are expected and points where they arc not expected, for a variety of malfunctions. For good reasons, human inspectors are part of this inspection system, and thus human inspection leUahitity is an essential element in ensuring structural integrity emd hence airworthiness. 

Such a task description invites task analysis, which would lead naturally to human reliability analysis (HRA). Indeed, perhaps the earliest work in this field applied HRA techniques to construct fault trees for aircraft structural inspection (Lock and Strutt 1985). The HRA tradition lists task steps, such as expanded versions of the generic functions above, lists possible errors for each step, then compiles performance shaping factors for each error. Such an approach was tried early in the FAA s human factors initiative (Drury et al. 1990) but was ultimately seen as difficult to use because of the sheer number of possible errors and PSFs. It is occasionally revised, such as in the current FRANCIE project (Haney 1999), using a much expanded framework that incorporates inspection as one of a number of possible maintenance tasks. Other attempts have been made to apply some of the richer human error models (e.g.. Reason 1990 Hollnagel 1997 Rouse 1985) to inspection activities (La-toreUa and Drury 1992 Prabhu and Drury 1992 Latorella and Prabhu 2000) to inspection tasks. These have given a broader understanding of the possible errors but have not helped better define the PoD curve needed to ensure continuing airworthiness of the civil air fleet. 

FAA 14 CFR airworthiness standards Part 23 normal, utihty, acrobatic and commuter category airplanes. Part 25 transport category airplanes. Part 27 normal category rotor-craft, Part 29 transport category rotorcraft. Federal Aviation Administration, www. airweb.faa.gov. 

Outside the damage size limitations, an engineering decision is requited for the design of the repair scheme by the aitcrafl airworthiness design authority. 

In summary, bonded repairs are the preferred approach for manufacturing repairs to both honeycomb sandwich and monolithic secondary stmcture. However, for the FAA and European Airworthiness and Safety Administration, the main reason for withholding certification of bonded repairs for primary structure is the lack of certainty over bond quality as it is not possible to assess strength and durability of bonded joints without destructive testing. 

Xie J, Lu Y. Study on airworthiness requirements of composite aircraft structure for transport category aircraft in FAA. In Procedia engineering, 2nd international symposium on aircraft airworthiness, vol. 17. ISAA 2011. pp. 270—8. 

Structural health monitoring (SHM) rehes on sensors that can be permanently placed on the stracture and monitored over time either in a passive or in an active way. These sensors should be affordable, hghtweight, and unobtrasive such as to not impose cost and weight penalty on the stmcture and to not interfere with the structural strength and airworthiness. Some of the sensor types that have been considered for SHM appUca-tions are ... 

The Airworthiness regulation mandatory requires some software QA activities be performed... 

For an airplane situations could occur for which a power generation system is required, independent from the main engines and the APU, to keep the aircraft controls operative. According to the airworthiness standards for large commercial aircraft a situation must be considered in which all internal combustion engines, main engines and APU, fail due to contaminated fuel, or kerosene lava dust in the atmosphere. 

Those actions taken to eliminate hazards or reduce risk to an acceptable level are appropriately documented to ensure this is maintained in the Continuing Airworthiness phase. 

AC20-131B, March 1993. Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II) and MODE S Transponders. FAA, Washington. 

FAR25, November 2007. Airworthiness Standards Transport Category Airplanes. Amendment 25-123. Federal Aviation Anthority, Washington. 

Markov Analyses (MA) Similar to the DD and FTA, but additionally calculates the probability of the system being in various states as a function of time. Here airworthiness is not a simple mathematical calculation, but depends on relative states of part of the system. However, MA has limitations that an FTA does not (e.g. it is difficult to model large complex systems and visualise fault paths in an M A model). For more information, see Appendix F in SAE ARP4761 (App E) and Chfton (2005, Chl8). 

CAP562, November 23, 2013. Civil Aircraft Airworthiness Information and Procedures. Safety... 

The PRA considers any event outside the immediate boundaries of a system which conld cause system failure and impact airworthiness. Once identified, each particular... 

Hazardous Materials TBD- review each supplier s Haz Mat dehverable. TBD for causes Negative airworthiness consequence only if material leaks in failure conditions (incl. overheat) Revisit this topic at CDR. Ensure that the H S departments see the HazMat List so that D-level and I-level maintenance procedures can be amended accordingly ... 

Mitigate using procedures These Instructions for Continued Airworthiness (ICA) provide the operator with limitations of use as weU as information on how to cope with the failure event when it does occur (see Chapter 11 for more information). 

A summary of the findings to date, including any open actions/activities. These findings should include all prescribed maintenance activities needed to ensure continued airworthiness. 

Recommendations of talk and intervals to go into the Zonal Inspection Programme (ZIP) and other Instructions for Continued Airworthiness (ICA). 

Learn (and share) best industry practices in the interest of Continued Airworthiness. 

Working with the flight crew (e.g. test pilots) and the HF Specialist, the safety engineer needs to coordinate the drafting of appropriate instructions on how to deal with system failures should they occur (regardless of their probability of occurrence). Under the EASA system, this issue of these instructions forms part of the Instructions for Continued Airworthiness (ICA) (refer EASA Part 21 and C25 Appendix H). 

What is needed is smooth handover from the Initial Airworthiness Phase to the Continuing Airworthiness Phase, with the ability to accomplish some of the outcomes listed in Section 11.1.3. Certifying staff always need to remember that airworthiness is the delivery of the technical aspects of a societal expectation for safety, not the delivery of safety in itself. 

The aim of this chapter is to look beyond the Initial Airworthiness Phase (leading... 

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