Imagine that one day you’ll be able to go on a short business trip from Jakarta to Seoul and still be able to have breakfast & dinner at home. Imagine it will only take 3 hours to fly there (one way) instead of long, dull 7 hours. Is it possible? The answer is yes, under one condition: travel twice as fast as the speed of sound!
That dream was once a reality few years ago. A well known supersonic transport aircraft from the past is Concorde. Developed by two countries, Britain & France, the beautiful creature had been released to the open sky, produced and serving the society for 27 years from 1976 to 2003. There was another one produced by the Russians but they didn’t last that long, only about a year from 1977 to 1978. But anyway those two had the same fate: they both stopped flying. Why? Were they ‘too far ahead of their time’? Or was it something else that did end the supersonic transport business back then?
One way to answer the question above is by taking a look at the design process of an aircraft. This design process is something that any aerospace engineer in the world must fully understand. There are four major steps in designing an aircraft:
- conceptual design
- preliminary design
- detail design
- tests & certifications
Conceptual design is the first phase of the design process. In this phase, a variety of possible solutions and ideas that meet the requirements are listed, sketched and then compared to each other. What’s important is that the discussion during this process is going to end up being a ‘trade-off study’, a study which includes explaining every advantages and disadvantages of any proposed aircraft configuration candidate.
After discussing and deciding which configuration is going to be the answer to the requirements, the design process steps into the next phase. Preliminary design is the first phase where numbers start to ‘speak’. This phase includes initial sizing of structural major components, aerodynamic analysis using any computers and simulations, stability and control characteristics, and the last but not least the money related aspects, economic and financial feasibility of the project ( aircraft design is not a charity, those people are looking forward to earn huge amount of cash! )
The next step is detail design and not a lot of changes occur here since this phase mostly talks about methods of producing and manufacturing the aircraft. And in the end, the aircraft is going to emerge as a prototype. This prototype ( or sometimes ‘these prototypes’ ) is going to be tested in the next phase which is easily recognized by its’ name, tests & certifications phase. In order to fly and operate, an aircraft needs to pass a number of standards. The success of this phase leads to approval by related organizations which translates to ‘a kind of guarantee in safety and comfort aspect’ to the users ( airline passengers ) in the future.
The analysis starts with an assumption that the design process is simplified into the form of those four steps. Let’s try to carry on the case by eliminating the ‘untroubled candidates’, leaving only the ‘POSSIBLY troubled candidates’. Here are the statements ruling out some aspects off the suspects, narrowing down the list:
- The Concorde operated for 27 years. It’s IMPOSSIBLE for any aircraft to operate up to that long period of time if there was a conceptual design flaw ( e.g: B.O.A.C accident ). Therefore the CONCEPTUAL DESIGN phase is no longer a suspect in this case
- The aircraft carried passengers which bought tickets from airliners back then. This means that the aircraft passed TESTS & CERTIFICATIONS phase of the design process, yet this DOESN’T mean that the tests & certifications phase itself had no contributing flaw back then
- The fact that Concorde operated for an extensive period of time also implies that accidents were so rare and passengers trusted the aircraft. Only 1 major accident of this aircraft was exposed widely ( Flight 4590 ), the few others were not since there were no fatalities
- The spotlight is now aiming at the PRELIMINARY DESIGN and DETAIL DESIGN phases. The accidents listed in point number 3 were all related to the same part of the aircraft: the landing gear wheels and the rudder section. There were 57 accidents related to the aircraft’s wheels and 2 other accidents related to the rudder section. These flaws demanded all Concordes’ rudder and wheels to be redesigned.
- The last but POSSIBLY the major players in the case is the ECONOMIC & FINANCIAL factors. Back at the 1970s, engineering works were not as sophisticated as they are nowadays. Drawings were still done manually, some researches, developments and tests were still very limited and expensive ( for example, imagine the existence of a supersonic wind tunnel back then ). No wonder the total cost of the project blew up to 1.3 billion pounds. The unit cost of Concorde in 1977 was 23 million pounds. Imagine how much each passengers had to pay. A single ticket was so expensive that only a very limited segment of people could afford it. Adding up to the problems, the redesign process after the listed accidents consumed more and more money while people began to lose trust to the aircraft. Recall that all these money related factors should’ve been well discussed and started being planned in the PRELIMINARY DESIGN phase.
The short 5 points step-by-step analysis leads to a conclusion: Concorde retired due to complications between technical and financial design flaw. An article in www.telegraph.co.uk also stated that excessive operational cost was the main cause of the death of the supersonic transport jet, aside of the flight 4590 accident.
To understand the importance of every step in designing an aircraft is mandatory for aerospace engineers. The understanding of the process also makes it a lot easier to track any faults in the design itself. This brief analysis is only an example, everybody who have already read this post and are interested can try doing the same thing using another real cases. Have a good time practicing! Oh and last but not least: are we going to have supersonic flight again sometime in the future? The answer is: yes! BOOM supersonic transport aircraft is currently being developed. But I’m not going to talk about it, that’s a whole different story.
Related books for further explanations & learnings:
- Jan Roskam — Airplane Design 8 volumes
- Daniel P. Raymer — Aircraft Design, A Conceptual Approach
