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Certification of Aircraft, Design and Production
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|Content source:||Cranfield University|
|Content control:||Cranfield University|
Aircraft Certification Requirements
Certification requirements for civil [commercial] aircraft are derived from ICAO Annex 8 Airworthiness of Aircraft [ICAO, 2016] and the ICAO Airworthiness Manual, Part V State of Design and State of Manufacture [ICAO, 2014]. Each ICAO contracting state then establishes its own legal framework to implement the internationally agreed standards and recommended practices.
Procedures for certification of aeronautical products (aircraft, engines and propellers) are published in each state. In the EU, these are contained in EC Regulation 748/2012 Annex I - Part 21 [EC, 2012], whereas in USA they are within FAR Part 21 [FAA, 2017]. These “Part 21” regulations also include procedures for the approval of design organisations (Sub-part J) and production organisations (Sub-part G). These processes are known respectively as Design Organisation Approval (DOA) and Production Organisation Approval (POA).
Such approvals are a necessary pre-requisite to obtaining product certification. The main technical codes to be followed for the design of products for certification are set out below as a list of certification specifications for Europe (EASA) and airworthiness standards for USA (FAA) applicable to different categories of product and environmental consideration.
|CS-22||Sailplanes and Powered Sailplanes|
|CS-23||Normal, Utility, Aerobatic and Commuter Aeroplanes||Part 23||AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES|
|CS-25||Large Aeroplanes||Part 25||AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES|
|CS-27||Small Rotorcraft||Part 27||AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT|
|CS-29||Large Rotorcraft||Part 29||AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT|
|CS-31GB CS-31HB||(Gas Balloons) (Hot Air Balloons)||Part 31||AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS|
|CS-E||Engines||Part 33||AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES|
|CS-P||Propellers||Part 35||AIRWORTHINESS STANDARDS: PROPELLERS|
|CS-LSA||Light Sport Aeroplanes|
|CS-VLA||Very Light Aeroplanes|
|CS-VLR||Very Light Rotorcraft|
|CS-34||Aircraft Engine Emissions and Fuel Venting||Part 34||FUEL VENTING AND EXHAUST EMISSION REQUIREMENTS FOR TURBINE ENGINE POWERED AIRPLANES|
|CS-36||Aircraft Noise||Part 36||NOISE STANDARDS: AIRCRFAT TYPE AND AIRWORTHINESS CERTIFICATION|
For full details of EASA Certification Specifications see the EASA Agency rules (Soft law) [EASA, 2017]. Full details of FAA Standards are also available [FAA, 2017].
Compliance with these specifications or standards is approached in one of two ways depending on the requirement. For structures typically the approach is known as Deterministic whereas for systems, a Probabilistic approach is taken. One example of each approach would be:
- For structure - No detrimental deformation of the airframe under the loads produced by a given magnitude of manoeuvre.
- For systems - Any catastrophic failure condition must (i) be extremely improbable [1 in 109 flight hours]; and (ii) must not result from a single failure.
For the safety assessment of aircraft systems, regulations are given in EASA CS25.1309 [EASA, 2016] and FAA Aviation Rulemaking Advisory Committee draft AC25.1309-1B [FAA, 2002]. Useful guidelines for conducting the safety assessment process are also given in ARP4761 [SAE, 1996].
The process for civil aircraft by which type certification is achieved comprises four steps. These are outlined below, but additional details can be found from EASA (2010), Type certification [EASA, 2010] and FAA Order 8110.4C [FAA, 2011]
1. Technical Overview and Certification Basis The product designer presents the project to the primary certificating authority (PCA) - EASA in EU, FAA in USA - when it is sufficiently mature. The certification team and the set of rules (Certification Basis) that will apply for the certification of this specific product type are established. In principal this agreed certification basis remains unchanged for a period of five years for an aircraft, three years for an engine.
2. Certification Programme The PCA and the designer define and agree on the means to demonstrate compliance of the product type with every requirement of the Certification Basis. Also at this stage the level of regulatory involvement is proposed and agreed.
3. Compliance demonstration The designer has to demonstrate compliance of the aircraft with regulatory requirements: for all elements of the product e.g. the airframe, systems, engines, flying qualities and performance. Compliance demonstration is done by analysis combined with ground and flight testing. The PCA will perform a detailed examination of this compliance demonstration, by means of selected document reviews and test witnessing.
4. Technical closure and Type Certificate issue When technically satisfied with the compliance demonstration by the designer, the PCA closes the investigation and issues a Type certificate. For European-designed aircraft, EASA delivers the primary certification which is subsequently validated by other authorities for registration and operation in their own countries, e.g. the FAA for the USA. Similarly EASA will validate the FAA certification of US-designed aircraft. This validation is carried out under a Bilateral Aviation Safety Agreement (BASA) between the states concerned.
a. A Type Certificate applies to an aircraft (engine or propeller) of a particular Type Design. Every individual aircraft of that type has to gain its own Certificate of Airworthiness C of A which is achieved when it can be shown to conform to the certificated Type Design and is in a condition for safe operation. As a general rule civil aircraft are not allowed to fly unless they have a valid C of A.
b. Organisation approvals, issued under Part 21, are based on regulatory assessment of capability, facilities, manpower, resources and quality assurance systems in relation to the tasks undertaken. Helpful supporting standards in this respect are AS/EN 9100 and AS/EN9120B [SAE, 2016].
c. Certification of military aircraft has in the past not followed the typical Type Certification Process outlined above. However since 2010 in Europe a very similar process has been evolved by the European Defence Agency (EDA). Known as the Military Airworthiness Authorities (MAWA) Forum [EDA, 2017], one of the documents published is a military guide to certification, denoted EMAR21 [EDA, 2016]. The documents are issued as requirements and do not have legal standing but are nevertheless being followed by a number of states both within and outside Europe.
Accidents and Incidents
There follows a sample of extracts from reports held on SKYbrary that involve a design issue as a contributory factor in the accident:
- AT72, en-route, Mediterranean Sea near Palermo Italy, 2005 (On 6 August 2005, a Tuninter ATR 72-210 was ditched near Palermo after fuel was unexpectedly exhausted en route. The aircraft broke into three sections on impact and 16 of the 39 occupants died. The Investigation found that insufficient fuel had been loaded prior to flight because the flight crew relied exclusively upon the fuel quantity gauges which had been fitted incorrectly by maintenance personnel. It was also found that the pilots had not fully followed appropriate procedures after the engine run down and that if they had, it was at least possible that a ditching could have been avoided.)
- MD82, Madrid Barajas Spain, 2008 (On 20 August 2008, an MD82 aircraft operated by Spanair took off from Madrid Barajas Airport with flaps and slats retracted; the incorrect configuration resulted in loss of control, collision with the ground, and the destruction of the aircraft.)
- B788, London Heathrow UK, 2013 (On 12 July 2013 an unoccupied and unpowered Boeing 787-8, remotely parked at London Heathrow after an arrival earlier the same day caught fire. An investigation found that the source of the fire was an uncontained thermal runaway in the lithium-metal battery within an Emergency Locator Transmitter (ELT). Fifteen Safety Recommendations, all but one to the FAA, were made as a result of the Investigation.)
- A346, en-route, Amsterdam Netherlands, 2005 (On 8 February 2005, a Virgin Atlantic Airways A340-600 experienced in-flight fuel management problem which led to loss of power of No 1 engine and temporary power loss of No 4. The captain decided to divert to Amsterdam where the aircraft landed safely on three engines.)
- SH36, vicinity Edinburgh UK, 2001 (On 27 February 2001, a Loganair SD3-60 lost all power on both engines soon after take off from Edinburgh. An attempt to ditch in the Firth or Forth in rough seas resulted in the break up and sinking of the aircraft and neither pilot survived. The loss of power was attributed to the release of previously accumulated frozen deposits into the engine core when the engine anti icing systems were selected on whilst climbing through 2200 feet. These frozen deposits were considered to have accumulated whilst the aircraft had been parked prior to flight without engine intake blanks fitted.)
- CRJ2, en-route, east of Barcelona Spain, 2006 (On 27 July 2006, a Bombardier CRJ200 being operated by Air Nostrum on a scheduled passenger flight from Barcelona to Basel, Switzerland in night VMC, suffered a sudden left hand engine failure and an associated engine fire when passing FL235 some 14 minutes after take off. An air turn back was made with indications of engine fire continuing until just three minutes before landing. An evacuation using the right hand exits was ordered by the Captain as soon as the aircraft had come to a stop and had been promptly actioned with the RFFS in attendance. There were no injuries to the 48 occupants during the evacuation and the only damage was to the affected engine.)
- Accident and Serious Incident Reports: AW - a list of reports concerning events where airworthiness was a causal or contributory factor.
- De Florio F (2016), Airworthiness: An Introduction to Aircraft Certification, 3rd edition, Butterworth-Heinemann
- EASA (2016), Certification Specifications and Acceptable Means of Compliance for Large Aeroplanes CS-25 (external links)
- EASA (2010), Type certification, PR.TC.00001-002 (external link)
- EASA (2017) Agency rules (Soft law), Certification Specifications
- EC (2012), Commission regulation (EU) No 748/2012, laying down implementing rules for the airworthiness and environmental certification of aircraft and related products, parts and appliances, as well as for the certification of design and production organisations. (external link)
- EC (2014), Commission regulation (EU) No 1321/2014 on the continuing airworthiness of aircraft and aeronautical products, parts and appliances, and on the approval of organisations and personnel involved in these tasks. (external link)
- EDA (2017) Military Airworthiness Authorities (MAWA) Forum
- EDA (2016), EMAR 21 - Certification of Military Aircraft and Related Products, Parts and Appliances, and Design and Production Organisations, Edition 1.2
- FAA (2011), Type Certification, Order 8110.4C (external link)
- FAA, FAA Standards
- FAA, FAR Part 21 - Certification Procedures for Products and Articles (external link)
- FAA (2002), AC25.1309-1B System Design and Analysis, Draft Arsenal edition. (external link)
- ICAO (2016), Annex 8 Airworthiness of Aircraft, 11th Edition, ICAO
- ICAO (2014), Doc 9760 Airworthiness Manual, Part V. State of Design and State of Manufacture, 3rd Edition, ICAO.
- SAE International (1996), ARP 4761 Guidelines and Methods for conducting the safety assessment process on civil airborne systems and equipment, SAE (1996)
- SAE International (2016), AS/EN9100D, Quality Management Systems - Requirements for Aviation, Space, and Defence Organisations
- SAE International (2016), AS/EN9120B Quality Management Systems – Requirements for Aviation, Space, and Defence Distributors