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<\/a><\/p>\nby Bjorn Fehrm and Henry Tam<\/p>\n<\/div>\n
December 12, 2025, \u00a9. Leeham News:<\/strong> We do a series about ideas on how the long development times for large airliners can be shortened. New projects talk about cutting development time and reaching certification and production faster than previous projects.<\/p>\n The series will discuss the typical development cycles for an FAA Part 25 aircraft, called a transport category aircraft, and what different ideas there are to reduce the development times.<\/p>\n We will use the Gantt plan in Figure 1 as a base for our discussions. We have completed the articles on Prototype Manufacturing and Ground Vibration Tests (GVT). We now conduct the program\u2019s flight tests with the manufactured test aircraft.<\/p>\n Figure 1. A generic new Part 25 airliner development plan. Source: Leeham Co. Click to see better.<\/p>\n<\/div>\n After high-speed taxi tests, the flight test aircraft is ready for its first flight.\u00a0 Starting from the first flight, the team would cautiously expand the operating envelope, such as speed, altitude, and center of gravity.\u00a0 The team would go on to verify the flight characteristics, systems functionalities, etc.\u00a0 Keep in mind, tests at this stage are company tests, not certification tests.\u00a0 The FAA Part 21, Certification Procedures for Products and Articles, states:<\/p>\n 21.35 Flight tests:<\/p>\n (a) Each applicant for an aircraft type certificate (other than under \u00a7\u00a7 21.24 through 21.29) must make the tests listed in paragraph (b) of this section. Before making the tests, the applicant must show\u2014<\/p>\n (b) Upon showing compliance with paragraph (a) of this section, the applicant must make all flight tests that the FAA finds necessary\u2014<\/p>\n The OEM\u2019s test pilots must fly each test case before the authority\u2019s test pilots (or their delegates) jump onboard for certification test flights.\u00a0 The test aircraft must also conform to the type design.\u00a0 We will cover some of the processes in a future article on the certification Implementation phase.<\/p>\n In practice, a flight-test aircraft is rarely 100% conformal to the type design.\u00a0 The OEM, for each deviation, must justify why the difference would not affect the test result for each test.\u00a0 For instance, the team plugged one of the cabin windows with flight test instrumentation.\u00a0 This would not impact a water ingestion test.<\/p>\n Figure 2. Water ingestion tests on the CS300. Note the plugged cabin window. Source: Bombardier.<\/p>\n<\/div>\n The flight test program must generate all the data necessary for the OEM to show compliance and the authority to find compliance with the airworthiness standards.\u00a0 It takes thousands of flight test hours to go through all the company test cases and certification test cases.\u00a0 For example, the Boeing 787-8 took approximately 5,000 hours of flight test to obtain the initial type certificate (source: Wikipedia).\u00a0 The Gulfstream G650 business jet took approximately 2,000 hours (source: AOPA).<\/p>\n In an ideal world, a flight test campaign is intended to confirm results from simulations and analyses.<\/p>\n<\/a><\/p>\nFlight Test<\/strong><\/h5>\n
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