[Industrial Standard] On the differences of airworthiness standards of piston engines in civil aviation (1)

On 13th May, 2016, the General Office of the State Council issued “Guiding Opinions on Promoting the Development of General Aviation Industry” (hereinafter referred to as "Opinions"), which made important plans to further promote the General Aviation Industry. The Opinions proposes five key tasks, i.e., to foster the general aviation market, accelerate the construction of general airports, promote industrial transformation and upgrading, expand the opening of low-altitude airspace and strengthen the whole process of safety supervision. It emphasizes the role of industrial transformation and upgrading in the future industrial development. By improving manufacturing, promoting industrial aggregation and deepening international cooperation, the level of R & D and manufacturing of general aircraft and the rate of self-reliance are gradually elevated, increasing the proportion of domestic general aviation aircraft in general aviation fleet. The main power type of general aircraft is piston engine. According to current statistics, the development projects of piston engine researches in domestic civil aviation adopt international cooperation in addition to imitation products. With the help of foreign advanced integrated technology and electronic control technology, the vehicle engine is changed into aero engine for aviation. The global cooperation of products will certainly lead to the cooperation of the airworthiness authorities among many countries, especially in the stage of product model certification. Due to the difference of airworthiness standards of civil aviation piston engines in the mainstream airworthiness systems of Europe and America, it is essential to understand the development trends of the standards and safety levels in the certification requirements, summarize the differences between Chinese and European standards, and make clear the key points concerned in the certification process.

一、ⅠDevelopment of airworthiness standards

Airworthiness standards are continuously revised through the accumulation of long-term work experience, lessons learned from previous flight accidents, necessary verification or demonstration, and public consultation. At present, the most influential airworthiness standards for aero engine are the Part 33, Chapter 14 of Federal Aviation Code (FAR33), and the CS-E of European Aviation Safety Agency (EASA).

1、The United States

The airworthiness standard of American aero engine is established based on the Law of the Sea System and revised by the amendments of accident case formation. Its evolution is closely related to several major changes of American civil aviation institution reforms. In 1937, as the predecessor of FAR33, the engine airworthiness standard of CAR part13 was formulated by the Department of Commerce Aviation Administration. At that time, aeropiston engines were mainly used, the terms and conditions for which covered the design and construction of civil aviation piston engines. But there was no special requirement for engine bench test. In 1941, the Civil Aviation Administration was reformed. As a result, the Civil Aviation Administration replaced the Department of Commerce Aviation Administration, during which CAR part13 added the terms of the engine bench test. In 1952, the Civil Aviation Administration revised the airworthiness standard of CARpart13 engines, and divided the airworthiness clause into two chapters to distinguish between piston engines and turbine engines, which is still in use today. In 1958, the Civil Aviation Administration was renamed the Federal Aviation Administration (FAA), and in 1965, the FAR 33 was issued, replacing CAR part13. Up to August, 2016, FAR33 had undergone 34 revisions. The development of aero-piston engine has gradually and fully matured since 1903 (more than a hundred years ago) when the first aeroplane equipped with a piston engine took off. Nevertheless, there is no great change in its design principle and structure. During the two world wars, the invention of turbocharger has brought about a great change in the requirements for product safety so as to improve the air intake pressure under the high altitude condition and the high altitude performance of the engine. In order to guarantee the safety in design and construction, no new technical requirement has been added except for that of turbocharger rotor. For bench test verification, the requirements of the clauses become clearer and more specific with the development of test verification technology, and the requirements of most clauses have been revised, except for the initial ones of knock test.

2、Europe

The European Aero engine Airworthiness Standard is developed from Chapter 3 of BCAR (British Civil Airworthiness Requirements, issued in 1949). The JAA (Joint Aviation Authorities), established in 1970, issued JAR-E to replace BACR, which became the general airworthiness requirement for aero engines in Europe. JAR-E has undergone a total of 12 revisions from 1970 to 2003 and has been replaced by the audited specification CS-E issued by the agency-reformed EASA (European Inspection Safety Agency). The correspondence between Chapter C of BCAR, JAR-E and CS-E is shown in Table 1. CS-E is applicable to civil aviation turbine engine and piston engine model certification, and the contents are divided into two volumes: The first volume is about airworthiness specification, and the second one is about acceptable conformity method. The EASA has made a plan for the revision of CS-E. Since its promulgation on 24th October, 2003, CS-E has undergone four revisions respectively. The current effective layout is CS-E Change4. For aeropiston engines among the results of the previous revisions, other revisions did not change the technical requirements of the clause except for redefining the term critical height of the piston engine, the maximum economic cruise power state, and the maximum recommended cruise power state in Revision 2.