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21Certification of Firefighting Aircraft

CERTIFICATION OF FIREFIGHTING AIRCRAFT

Introduction

Aircraft certification standards are determined by a multitude of factors depending on the purpose. In order to ensure air worthiness, aircraft standards are broadly grouped into domestic regulations, technical projects and general policies and regulations. Prior to deploying an aircraft for a special or technical projects, it is important to note that the advisory circular AC 21-3(1) released by the Civil Aviation Safety Authority (CASA) in November 2010 requires special conditions to be met. As a prerequisite for a project to be undertaken by a start-up company under my leadership as a CEO, I shall give an insight on the minimum requirements that should be achieved in order to avoid framework breakdown once it is up and running. The company intends to utilise Antonov AN74TK-200 aircraft in an aerial firefighting venture to be contracted to a consortium of Australian State Governments. This aircraft shall be imported from the manufacturer after which modification shall be carried out by fitting with external saddle style tanks similar to those previously fitted to Bombardier Q400 aircraft. The aircraft shall be registered and operated under the Australian register as per the prevailing rules and regulations. This contract requires 6 aircrafts to be availed on a 2-hour standby basis from October 15th to the start of March the following year. Each aircraft shall be flown for 600 hours between this periods. It is planned that once this period elapses, the aircraft shall be flown to Antonov factory for maintenance and then availed in Canada for the same kind of contract from June to start of September. The complexity of this operation is perceived as an issue of concern by CASA as this would have an impact on the air worthiness of the aircrafts to be deployed to the activity. This paper outlines some of the issues identified as key to the technical airworthiness of these aircrafts and how the company intends to manage this kind of issue. This shall be carried out together with the minimum issues associated with the initial certification which is associated with the base aircraft and the modifications that shall be carried out for firefighting. This paper shall also discuss on the likely form and operation of the continuing airworthiness management organisation (CAMO) with an emphasis on how such information shall be dealt with form in service occurrences, urgent repairs and information from Antonov. The operational impacts on the major forms of maintenance to be conducted is also carried out to indicate how the continuing airworthiness management organisation shall manage this.

General Specifications of Antonov AN74TK-200

This section offers a brief highlight of the specifications of Antonov AN74TK-200 since they will be required when carrying out the certification process. To begin with, Antonov AN74TK-200 is propelled by A36 series twin-turbofan rated at 6,500kgf each. It is specially designed to support research, transport operations and reconnaissance activities within the arctic and Antarctic regions. Other operations such as medium air cargo haulage are allowed for conditions within the range of -60°C up to +45°C making it a suitable bet for firefighting activities. For cargo purposes, this plane is allowed for up to 7.5 tonnes at a maximum cruising speed of 700km/h and a maximum altitude of 10,100m. The design of this aircraft is inspired by the AN-72 airlifter based on its excellent airlifting performance and subsequent self-sufficiency. It is adapted for autonomous short take-offs and landings on unpaved airfields due to low-pressure tires and high engine arrangement that prevents the ingestion of foreign objects. In order to meet the International Civil Aviation Organization (ICAO) requirements, the aircraft is limited in terms of noise and emissions (Antonov Company, 2014).

Antonov AN74TK-200 is installed with an auxiliary power unit that is based on TA-12 gas turbine that is installed in the right landing gear sponson. This ensures power supply to the engines for pneumatic start, air-conditioning power and compressed air generators. These aircrafts have undergone several modification with subsequent certification being cleared as per the ICAO chapter 3 annex. The adaptability is evident from the contingency power setting that is designed for use in case of engine failure especially when the conditions of operation are extremely hot. AN74TK-200 aircraft is designed as a special purpose freighter whose range can be varied from 1,650 km to 2,300 km with 7.5 tonnes of cargo. Generally, this type of aircraft is open to multiple modern technology modifications as long as the power rating is not exceeded (Antonov Company, 2014).

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Figure 1: Principle dimensions of Antonov AN74TK-200.

Minimum Airworthiness Certification Requirements

According to De Florio (2011) airworthiness of an aircraft refers to possession of allowable limits of safety conditions and regulatory requirements by an aircraft. Safety conditions refer to freedom from any illness, injury or loss of life and damages that might result from having not met certain requirements. The necessary requirements on the other side may vary from one location to the other depending on the intended aircraft utility but the higher standards by ICAO still hold. These are intended to promote safety by laying down a mitigation framework for all the factors that are thought to pose as a danger to human and property. Allowable limits refer to a certain bracket within which aircrafts are confined due to the operation parameters that are obviously contributory to air safety. At times, exceeding or undermining the allowable limits pose as a threat to safety of aircrafts.

Technical Requirements

The technicalities of airworthiness of an aircraft is based on the design which is expected to meet the approved standards of a locally or internationally approved organisation. The construction of an aircraft is also important due to the required strengths and other design specification from the aeronautical architecture bodies (DOAs). In order for continued approval or first approval within a locality, the aircraft must be maintained in accordance to approved regulations of guided by an approved body. The acceptability of the regulator in meeting the set rules and regulations is an important aspect of certification (Bianco & Amanda, 1996). The design and construction of the tanks should be governed by features and details that are not hazardous to any extent. For certification to be carried out, the regulatory body must approve all the critical characteristics associated with the rotorcraft so as to avoid the shortcomings associated with integrity levels.

The major contentious issue that may arise during the certification process of the Antonov AN74TK-200 for purposes of firefighting are the design standards. Design standards are defined by the operating intent of the end user and as such, most civil processes summaries defined in document AC-21-40A of Australia aviation framework. The design standards that are required for a firefighting aircraft should at least have a high manoeuvrability and controllability. During the modification process, the weight and balance aspect must be adhered to in order to ensure that the design requirements are achieved. According to subpart B of the European construction standards, the design requirements that should be achieved include protection against fire and heat. Pressurisation should also be inspected prior to certification since the aircraft shall be highly affected by the external environment (Tackett, 2000).

Material Requirements

The materials used in building the bottom tanks must be durable and suitable in accordance to the AMC CS-LURS.602 regulations. This should be established based on the industrial experience or the upcoming superior materials. The strength data for the tanks and the features attaching them to the aircraft’s belly must be taken into account when carrying out the preliminary designs for certification measures. The environmental conditions must be considered since the aircraft shall be operating in high temperature zones. The minimum requirements are for the tanks to be made up of fire-retardant materials due to the low flight altitudes that are experienced (Blue Ribbon Panel, 2002).

Design and Construction

If by any chance the external saddle tanks are going to be fastened to the main aircraft using bolts or any other type of fastening that could jeopardise the safety of the firefighting operations, then the aircraft must be allocated with two more locking devices. The environmental conditions must not affect the locking devices that are associated with the fastening the tanks. Due to the terrestrial nature of the modification, the material used shall be checked prior to the certification. The material should be suitably protected towards deterioration or even such environmental adversities as weathering, corrosion, and abrasion. The material that is used in performing the modification should not in any way react with the plane material. In short, it could be more preferable if the technical specifications of the materials used are the same as that of the ones utilised on Antonov AN74TK-200 (Clothier, et al., 2011).

Special factors are also part of certification requirements especially when strength of the modification done needs special attention. In case the external saddle style tanks are to be casted the strength requirements shall need at least one static test in order to establish their strength and subsequent airworthiness of the plane. This may be carried out by visual and other allowed non-destructive tests that take the high temperatures of operation into consideration (Joint Authorities for Rulemaking of Unmanned Systems, 2013).

Design Approvals

Prior to listing of all these factors as applicable in the certification of special purpose aircraft Piper (1961) states that the industry that had modifications done had to be approved. Modifications had to be done in accordance to the latest design standards by the approved civil aviation bodies. Improved guides have been produced by the ICAO when it comes to airworthiness certification for modified aircrafts. In order to speed up some of these issues it is mandatory that documents with regard to any changes in structure be certified by such bodies as Design Organisation Approvals (DOAs) prior to the airworthiness survey. Approved organisations are hierarchies which ensure that individuals who are involved in the design approvals are held accountable. These bodies are documented by the Australian Civil Aviation Safety Authority (CASA) as a summation of the requirements contained in design assurance processes by Federal Aviation Administration (FAA) and ADF (RMIT University, 2014).

Establishing Compliance

Since it is the sole responsibility of the certification applicant to demonstrate compliance of the aircraft towards a series of airworthiness requirements, it is important that reports other than structural be availed. These include environmental test, functional test, fire or flammability test which may be important for qualitative, quantitative, or comparative. It is suggested that comparative tests be carried out against similar firefighting aircrafts such as Bombardier Q400 aircraft. This is based on the fact that they were also fitted with external saddle style tanks before being phased out. The compliance test shall involve a revised compliance list thus any slight changes made have to be documented in utmost good faith to allow for smooth transitioning of aircraft for operation purposes. These tests should be evaluated and approved by CASA and locations of failure be determined before the aircraft is certified for airworthiness (Joint Authorities for Rulemaking of Unmanned Systems, 2013).

Handling Information

Handling of information received from in service occurrences and aircraft manufacturer needs a careful approach in order to achieve Continuing Airworthiness Management Organisation (CAMO) requirements. Information with respect to continued worthiness should be embraced for purposes of periodical maintenance and acceptance by an approved organisation. This shall be used to ensure that defects are rectified for compliance with all the airworthiness directives. Modifications and repairs shall also be enhanced if information received from field is utilised accordingly. There is a tendency by certain items to be obsolete with time, it is therefore necessary for replacement action to be undertaken in order to avoid malfunction by the aircraft and subsequent disqualification by CAMO. The information can also be used to achieve continued airworthiness by approving the maintenance program. Ensuring that all serviceable items are done accordingly is important since some of them are vital for the aircraft to perform operations effectively not only in the Australian region but also when it moves to Canada from June and the start of September. It should be noted that the airworthiness guidelines that apply around the world are drafted jointly by leading organisations such as CASA, FAA and CAA. The maintenance program that shall hence be carried out within Australia shall be applicable in the rest of the world thus information received should be handled with the importance it deserves lest the operations be grounded (RMIT University, 2014).

Information from Antonov is most likely to come in form of a document manual known as an AFM (Aircraft Information Manual). This document is drafted by the manufacturer and approved by an approved organisation for purposes of safe aircraft operation. This document contains information such as the operating procedures and their subsequent operational limitations. Information received from Antonov shall be treated with importance when it comes to aircraft operation since this is meant to be complied with in accordance to all airworthiness directives (ADs). Manufacturer information provides descriptive information such principle airframe dimensions and power plant. According to Wald et al. (2010), manufacturer information is important for the intended modifications and any other changes that shall follow. Use of this information shall not only aid the crew in ensuring safe operation of the aircraft but also in the maintenance and general service.

Adherence to manufacturer information for maintenance purposes shall ensure continued air worthiness as this contains preventive and minor maintenance activities to be carried out every 25 and 100 hours respectively. Inspections programs that are contained in the manufacturers’ manuals are mandatory if the company operating the aircraft desires to be continued certification for airworthiness. Other documentation such as master minimum equipment lists (MMELs) have been adopted by CASA to guide the emergency crew in their operation. The list of items to be replaced from time to time is also contained in the manufacturer information with the inclusion of what is to be removed, installed or repaired, items to be replenished depending on the operation of the aircraft, personal protective equipment, wheels replacement (and the type of wheels to replace with – chemical composition), approved operational installations, instrument replacement and modification adaptations, equipment replacement and maintenance and software updates among others. Stringent information adherence is followed up by CAMOs to ensure matters highlighted by manufacturers are followed for purposes of continued airworthiness certification. To add on this, manufacturer information contains various key abbreviations explanation and conversion material which needs to be handled painstakingly for operational success (Federal Aviation Administration, 2009).

Information from in service occurrences may pose unsafe conditions to human life and property. EASA guidance is very clear when it comes to information on unsafe conditions identified from years of in service experience and tests. It is important that this information be handled by the safety managers with the care it deserves since this is the only way to ensure continued air safety and any further complications that may occur. This information should also be counterchecked with manufacturer information enlisted above in order to establish discrepancies that may further arise and how to prevent them for purposes of recertification by CASA if a major periodical maintenance or inspection might have to follow. Design features failure due to the modifications carried out on Antonov AN74TK-200 aircraft need to be attended to as a matter of emergency to avoid accidents. Unsafe conditions must be attended to in order to save the fading safety margins, avoid distress and excessive work load to the aircrew (RMIT University, 2014). Documentation regarding actions taken by the company in order to ensure continued airworthiness must be kept up-to-date so as to ensure smooth transitioning between the two countries of operation.

Due to the delicate nature of air operations, information about emergency repairs should be handled with the urgency they deserve. Grounding an aircraft due to such information is a paramount move to allow for repairs while the replacement aircraft continue operating. Due to the fact that there shall be six aircrafts operating within the company fleet, it shall be sound to attend to one in need of urgent repairs to ensure air safety. As part of the company’s loss mitigation policies, the enterprise risk management policies have to be followed too. This systematic approach shall work hand in hand in order to allow for performance management especially considering the modification part of the aircraft has to be closely monitored. Once information on emergency repairs has been passed to the management, it is important for the engineers to establish the key impacts that this risks pose to airworthiness. The second procedure is to ensure a deep analysis and coverage of the eventualities for top level risk analysis. This translates to future mitigation measures that shall be imposed by the company owing to the fact that the emergencies occur often. The repeatability of these emergency repairs should also be analysed with the involvement of the major stakeholders i.e. the aircraft manufacturer and the approved certification body. Mitigation measures and findings documented with regard to the urgent repairs undertaken by the stakeholders shall then be documented and handed over to CASA for continued airworthiness approval. From this information is notable that bodies approved for certification are mandated with responsibilities of monitoring aircraft safety. It is however important for company safety management to ensure that the aircraft is monitored for implementation of effective control processes for continuous risk assessment and reduced risk profile in association with arising emergencies (Chansa-ngavej & Saikaew, 2008).

Operational Impact on Maintenance

Due to the abrupt nature in which fires occur, the operational impact of firefighting operations on aircraft shall be more profound than any other field of operation. Furthermore, the environment of operation is very harsh in comparison to other areas of work such as passenger transport. Another aspect of operational impact that is worth discussion is the modification that have to be carried prior to commencement of operations. It shall be a common occurrence for the structure to fail from time to time due to its extraneous nature. The fact that the aircraft shall always be loaded with around 4.5 tonnes of water from time to time call for more inspection and repairs than any other aircraft since this calls inspections to be conducted more often.

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Figure 2: Operational impacts on the aircraft.

According to Ahmadi, et al. (2013), the periodical assessment is meant to look for failures associated with ground and air operations interruption. Maintenance shall therefore be impacted negatively due to redundancy, equipment failure and increased maintenance bills from time to time. The crew shall have to suffer from operational interruption from time to time due to maintenance problems and cancellation of flight for subsequent safety. Increase in maintenance activities due to the heavy nature of operations is expected to cause loss of opportunity and customer dissatisfaction. All the projected maintenance costs have to be incorporated in the initial bill for smooth operations. The chart below shows some of the operational failures that shall be encountered by the maintenance team.

CAMO shall have to introduce more stringent measures of checking the aircrafts fleet due to the nature of operations. CAMO shall further determine the qualification levels of the persons to be appointed to the accountability levels as shall be dictated by CASA from time to time. Due to the extreme operation nature, the competence of these people has to be monitored and certified by agreeable bodies. Releasing aircrafts to operation after a major maintenance operation needs certification of release to service (CRS). The delicate nature of firefighting operations also requires that the AMO ensure that the employees responsible of special projects aircrafts be CASA approved as per training procedure and qualified by the exposition organisation. These translate to responsibility impacts on CAMO as shall be bestowed to the engineering fraternity that shall be responsible for the maintenance of the aircraft fleet (Civil Aviation Safety Authority, 2013).

Conclusion

Certification of special projects aircraft Antonov AN74TK-200 to be modified for firefighting services poses both structural and operational challenges to the aviation fraternity. The main challenges that the modifications present to the company are well covered herein with the solutions that are going to aid in solving the principle issues. Also discussed in this report is the approach of handling information from in service occurrences, Antonov and urgent repairs. The documentation issue is therefore important for certification by authorities such as CASA and Canada Civil Aviation (TCCA) in both countries of operation. The maintenance is also not going to be hindered by the operations thus the modifications have to be done to conform to design standards by DOAs.

List of References

Ahmadi, A., Gupta, S. & Kumar, U., 2013. Assessment of the cost of operational consequences of failures in aircraft operation, Luleå, Sweden: Luleå University of Technology, .

Antonov Company, 2014. AN-74T / Special-Purpose Freighter. [Accessed 24 May 2014].
Available at: http://www.antonov.com/aircraft/transport-aircraft/an-74t
[Online]

Bianco, . D. P. & Amanda, M., 1996. Professional and occupational licensing directory: A descriptive guide to state and federal licensing, registration, and certification requirements.. s.l.:Gale Research.

Blue Ribbon Panel, 2002. Federal Aerial Firefighting: Assessing Safety and Effectiveness, New York: USDA.

Chansa-ngavej, C. & Saikaew, C., 2008. Enterprise risk management in action for aircraft maintenance services. Services management in Asia Pacific: issues and challenges, pp. 271-296.

Civil Aviation Safety Authority, 2013. Acceptable Means of Compliance (AMC) and Guidance Material (GM) CASR Part 66: Continuing Airworthiness – Aircraft Engineer Licences and Ratings, Sydney: Civil Aviation Safety Authority.

Clothier, R. A., Palmer, J. L., Walker, R. A. & Fulton, N. L., 2011. Definition of an airworthiness certification framework for civil unmanned aircraft systems. Safety Science, 49(6), p. Pages 871–885.

De Florio, F., 2011. Airworthiness: An Introduction to Aircraft Certification. 2 ed. Sydney: Elsevier.

Federal Aviation Administration, 2009. Pilot’s Handbook of Aeronautical Knowledge. New York: Skyhorse Publishing Inc..

Joint Authorities for Rulemaking of Unmanned Systems, 2013. Certification Specification for Light Unmanned Rotorcraft Systems (CS-LURS), Canberra : Civil Aviation Safety Authority.

Lutters, W. G. & Ackerman , M. S., 2002. Achieving Safety: A Field Study of Boundary Objects in Aircraft Technical Support. New York, Association for Computing Machinery.

Piper, W. T., 1961. Flying Magazine Feb 1961. Briefings, February, p. 8.

RMIT University, 2014. AERO2513: Airworthiness Management Frameworks. Aerospace Mechanical, and Manufacturing Engineering, pp. 1-154.

Tackett, W. R., 2000. General Aviation Firefighting for Structural Firefighters. New York: Cengage Learning.

Wald, A., Fay, C. & Gleich, R., 2010. Introduction to Aviation Management. 1 ed. Berlin: LIT Verlag Münster.