Concorde Type Certificate and Airworthiness
To operate as a passenger airliner, Concorde was required to conform to a type Certificate (TC). There have been many comments made on various forums regarding the TC for Concorde, so I have decided to write this section to try and make the situation clearer.
The prototypes and pre-production Concordes did not conform to the Type and are not covered by the TC.
Initially, the applicant firm who wants to construct and fly the prototype submits documents to their local aviation regulating body, in the UK this would be the CAA. This details how the proposed design would fulfil the airworthiness requirements. After investigations by the regulator the CAA, the final approval of such documents (after the required comments and amendments in order to fulfil the laws), becomes the basis of the certification. The firm follows it and draws a proposed timetable of actions required for certification tests. With the application, the regulations to be applied will usually be frozen for this application for a given amount of time in order to avoid a situation where the applicant would have to change the design as a result of changed regulation.
An initial design sample known as a prototype is built. This would refer to either the aircraft or the engines, depending on the basis of the certification. For the purpose of illustration, the discussion shall be limited to the aircraft. Normally a few prototypes are built, each subject to different tests. In the case of Concorde there were two Static-test airframe prototypes built, there was one French version at Toulouse, which was used for purely for static tests, and tests such as vibration and flutter.
The other one British and located at Farnborough in the UK and used for the long-duration thermal fatigue tests. There were also two prototypes built for flight purposes (Airframes 001 & 002) to test the basic design. These two prototype aircraft were used to expand the flight envelope of the aircraft as quickly as possible and to prove that the design calculations for supersonic flight were correct.
The prototypes are first used for ground and system tests. One of the prototypes (known as the “static airframe”) is subject to destructive testing, i.e., the prototype is subject to stress beyond normal and abnormal operations until destruction. The test-results are compared with initial submitted calculations to establish the ultimate structural strength.
Other prototypes will undergo other systems tests until the satisfaction of the regulators. With all ground tests completed, prototypes are made ready for flight tests, as with 001 and 002. The flight tests are flown by specially approved flight test pilots who will fly the prototypes to establish the ultimate flight limits which should be within the airworthiness rules. If a long range airliner is tested, the flight tests may cover the whole world, which is what we saw with the Concorde prototypes. With Concorde two further prototype aircraft were built, known as the pre-production airframes (01 and 02)
Both of the two pre-production aircraft had a lengthened fuselage, smaller passenger cabin windows than the two previous prototypes airframes, and a new glazed visor design, something that the FAA (The American regulating body) had insisted on. Olympus 593-4 or 593 Mk 602 engines were also fitted to the aircraft. The pre-production aircraft were used to further develop the design of the final production aircraft that would conform to the Type. Other changes to the design included a different wing plan form that of the basic prototypes, a larger fuel capacity, and different air intake systems. Both the two pre-production Concordes differed in size and design from each other, the French one which built last, being close to the final production design of Concorde.
In parallel with aircraft testing, the applicant firm also draws up maintenance program to support continuous airworthiness after approval of the design. The program is drawn with inputs from tests results and also from initial customers’ engineering departments. The proposed maintenance program is submitted to the regulators for comment and approval.
The normal process is that after successful completion of all ground and flight tests, along with an approved maintenance program, the prototype is then approved, and the firm is granted the type certificate for the prototype. It is normally understood that the prototypes should include all furnished equipment for its intended role of the aircraft As the Concorde prototypes did not conform to this standard, the manufacture built and used two production development aircraft G-BBDG and F-WTSB, and later a production airframe G-BOAC. The legal term for the firm is now the “type certificate holder”, in the case of Concorde this was jointly held at first by BAC and Aerospatiale, the two companies that built the airframe. They later past the TC on to Airbus SAS, of which both companies held shares. Subsequently normally the prototype would serves as a template for the aircraft production. Hence the aircraft rolling out of the factory should be identical to the prototype, and each given a serial number (a “series aircraft”). But of course this was not the case with Concorde so hence the reason they built two further development production aircraft (G-BBDG and F-WTSB) to fulfil this role as the four prototype aircraft did not conform to the final design.
The Concorde prototypes and development aircraft were…
001 F-WTSS (French) Prototype Airframe
F-WTSS (production designation 001) was the first Concorde to fly, on 2 March 1969, and was retired on 19 October 1973, having made 397 flights covering 812 hours, of which 255 hours were at supersonic speeds.
002 G-BSST (British) Prototype Airframe
G-BSST (002) first flew on 9 April 1969 from Filton UK to RAF Fairford UK. Its last flight was on 4 March 1976. It had made 438 flights (836 hours), of which 196 flights were supersonic.
101 (01) G-AXDN (British) Pre-production Airframe
Concorde G-AXDN (101) first flew on 17 December 1971 from Filton and was retired on 20 August 1977, having made 269 flights (632 hours), of which 168 flights were supersonic.
102 (02) F-WTSA (French) Pre-production Airframe
Concorde F-WTSA (102) first flew on 10 January 1973 from Toulouse. It was the fourth aircraft and the first to have the dimensions and the shape of the future production aircraft. It was the first to fly to the United States (on 20 September 1973 to Dallas, Texas). For several years the aircraft was painted in British Airways colours on one side and Air France colours on the other. It made 314 flights (656 hours), of which 189 supersonic and was then retired on 20 May 1976.
201 F-WTSB (French) Development Production Airframe
F-WTSB first flew on 6 December 1973 from Toulouse. Its last flight was on 19 April 1985 from Chateauroux to Toulouse flying a total of 909 hours.
202 G-BBDG (British) Development Production Airframe
G-BBDG first flew on 13 December 1974 from Filton to RAF Fairford. It last flew on 24 December 1981 after a total of 1282 hours. After the final flight, it was stored at Filton in a state of semi-airworthiness throughout 1982, where it could be returned to flight in two weeks if required. However this was never required and the aircraft was eventually bought by British Airways as part of a Concorde support buy-out in 1984. G-BBDG was a 5100 variant aircraft and not a 5101/5102 variant as with the final production airliner Concordes
The Type Certificate
This is awarded by aviation regulating bodies such as the CAA to aerospace manufacturers after it has been established that the particular design of a civil aircraft and engine has fulfilled the regulating bodies’ current prevailing airworthiness requirements for the safe conduct of flights under all normally conceivable conditions (military types are usually exempted hence the difference between Concorde return to Flight and the Vulcan that flies today). Aircraft produced under a type certified design are each issued a Standard Airworthiness Certificate, this was what was removed from each Concorde by the CAA following the Paris crash.
A Type Certificate (TC) is a design approval issued by the Civil Aviation Authority (CAA) of a given country (such as the US FAA and EU EASA) when the applicant demonstrates that a product complies with the applicable regulations. The TC normally includes the type design, the operating limitations, the Type Certificate Data Sheet (TCDS), the applicable regulations, and other conditions or limitations prescribed by the CAA. The TC is the foundation for other approvals, including production and airworthiness approvals. TC’s are normally issued for airframes and engines.
An “Airworthiness Certificate” is only issued to an aircraft that is properly registered and was found to conform its TCDS and be in a condition for safe operations. The Airworthiness Certificate is valid and the aircraft may be operated as long as it is maintained in accordance with the rules issued by the CAA
Supplemental Type Certificate (STC)
This is issued by the aviation Authority approving a product (aircraft or engine) modification. The STC defines the product design change, states how the modification affects the existing type design, and lists serial number effectively. It also identifies the certification basis listing specific regulatory compliance for the design change. Information contained in the certification basis is helpful for those applicants proposing subsequent product modifications and evaluating certification basis compatibility with other STC modifications.
After the aircraft enters into service, it is subject to operational wear and tear which may cause performance degradations. The approved maintenance program serves to maintain the aircraft airworthiness. Users have to comply in order to maintain their aircraft’s airworthiness certificate. The maintenance may be light or heavy (such as overhauls) as dictated by the schedules and tasks in the aircraft’s maintenance program.
Airworthiness Directives (ADs)
Sometimes during service the aircraft may encounter problems that may compromise the aircraft’s safety, which are not anticipated or detected in prototype testing stages. The aircraft design is thus compromised. The regulators will now issue an airworthiness directive to the type certificate holder and to all owners globally. The directives normally consist of additional maintenance or design actions that are necessary to restore the type’s airworthiness. Compliance is mandatory and thus if an operator does not comply with an AD, then the datum aircraft is not considered airworthy. ADs may also be raised with changes of the local or global aviation rules and requirements, for example the US requirement to fit armoured cockpit doors for all airliners post 9-11.
A real example of this type of documentation can be found by clicking on the link below. It is with reference to the post 9/11 Introduction of a reinforced cockpit door, the surround and lock system
The certifying authority issues an AD when an unsafe condition is found to exist in a product (aircraft, aircraft engine or appliance) of a particular type design. AD’s are used by the certifying authority to notify aircraft owners and operators of unsafe conditions and to require their correction. ADs prescribe the conditions and limitations, including inspection, repair, or alteration under which the product may continue to be operated.
Service Bulletins (SBs)
With increasing in-service experience, the type certificate holder may find ways to improve the original design resulting in either lower maintenance costs or increased performance. These improvements (normally involving some alterations) are suggested through service bulletins to their customers as optional (and may be extra cost) items. The customers may exercise their discretion whether or not to incorporate the bulletins. Sometimes SBs can become mandated by relevant ADs.
Changes to the Type Certificate (TC)
Often the basic design is enhanced further by the type certificate holder. Major changes beyond the authority of the service bulletins require amendments to the type certificate. For example, increasing (or decreasing) an aircraft’s flight performance, range and load carrying capacity by altering its systems, fuselage, wings or engines resulting in a new variant may require re-certification. Again the basic process of type certifications is repeated (including maintenance programs). However, unaltered items from the basic design need not be retested. Normally, one or two of the original prototype fleet are remanufactured to the new proposed design. As long as the new design does not deviate too much from the original, static airframes do not need to be built. The resultant new prototypes are again subjected to flight tests.
Upon successful completion of the certification program, the original type certificate is amended to include the new variant (normally denoted by a new model number additional to the original type designation).
Supplementary/Supplemental Type Certificate (STC)
Any additions, omissions or alterations to the aircraft’s certified layout, built-in equipment, airframe and engines, initiated by any party other than the type certificate holder, need an approved supplementary (“supplemental” in FAA terminology) type certificate, or STC. The scope of an STC can be extremely narrow or broad. It could include minor modifications to passenger cabin items or installed instruments. More substantial modifications may involve engine replacement, and or a complete role change for the aircraft, such as converting the aircraft in to heritage role aircraft. STCs are applied due to either the type certificate holder’s refusal (frequently due to economics) or its inability to meet some owners’ requirements. STCs are frequently raised for out-of-production aircraft types conversions to fit new roles. Before STCs are issued, procedures similar to type certificate changes for new variants are followed, likely including thorough flight tests. STCs belong to the STC holder and are generally more restrictive than type certificate changes.
Validity of Type Certificate
The type certificate holder keeps the type certificate valid by continuously following airworthiness directives, issuing service bulletins and as well as providing spares and technical support to keep the aircraft current with the prevailing rules, even after the production of the type has stopped, as was the case with Concorde. This is what is meant by supporting the type and in this manner many out-of-production aircraft continue useful lives. STCs are also bound by the same rules. When the holder decides to stop supporting the aircraft type, the type certificate is returned to the regulators and the remaining aircraft fleet permanently grounded. In this manner the whole Concorde fleet was finally grounded when Airbus SAS surrendered its type certificate, Airbus SAS no longer hold the Type Certificate for Concorde.
These are the British Airways aircraft that conformed to the type certificate issued for Concorde by the CAA. The British fleet Variant 102 aircraft 5102 numbers were:
G-BOAC – 5102-01.
G-BOAA – 5102-02.
G-BOAB – 5102-03.
G-BOAD – 5102-04.
G-BOAE – 5102-05.
Although G-BOAG (G-BFKW) and G-BOAF (G-BFKX) were originally Variant 192 (British unsold aircraft), these correspondingly became 5102-06 and 5102