So, a company or an individual wants to begin the aircraft design process… Have you ever wondered where to start? Thankfully, there are a few key principles which can help guide engineers through any design process, through improved analysis the fundamentals of design, this same process can be refined into a aircraft design process. However, before moving on to design process, it is important that an engineering product follows a very similar design approach. In previous articles we discussed how to avoid major mistakes as a mechanical engineer, these design processes are excellent examples of how you can help to avoid errors.
The general engineering design process
There are two types of engineering companies; assembler companies and the sub-contractors. Companies like Jaguar Land Rover, Airbus, and Apple are the assemblers. They are the brand you buy. But these companies often outsource their work to sub-contractors: smaller companies developing specialized products.
A very typical approach to any product development is as shown in the diagram below:
The Aircraft Design Process
The design process for an aircraft can be seen as very similar to other engineering products. However, the complexity of an aircraft and the tight safety regulations required make it a very expensive and long process. The general process can be divided as shown below:
In order to succeed, it is important to properly frame your issue by identifying key design requirements. Creating a process map is the first step towards designing and building a new aircraft.
STEP 1: Problem Definition
At this initial stage, a new market demand has been identified. For example, a company might have identified that there is a growing demand for small private jets. In the inital problem definition stages it is crutial to first identify the key requirements of the new product then to determine how realistic it is to create this product through a feasibility analysis.
STEP 2: Conceptual Design
This stage includes back of the envelope calculation, where all the ideas are brainstorm. As the design continues to be revised it will undergoe many transformations to conform to the fit/form/functions that are desired by the end user or purchaser. These basic functions are brought together to create the initial configuration design which is used to discuss different possibilities with the consumer during a conceptual design review.
STEP 3: Preliminary Design
The preliminary design phase is where engineers go a step further into the design process to create a basic proof of concept. In this stage the engineers will calculate requirements that the airplane will have to conform with in order to fly, these can include Aerodynamics, Flight Mechanics, Structure stresses and stability. Following these is a preliminary design review, to ensure the concept can become a reality and for a reasonable price.
STEP 4: Detail Design
At the detail design stage, every single component will be designed from and tested. This is a highly complex and critical stage of the process. It also requires all the different design teams to work closely. The main aircraft components designed stages are:
- Wing Design
- Tail Design
- Fuselage Design
- Propulsion System
- Landing Gear
- Wing Tunnel Testing
- Wight Distribution
- Performance and stability analysis
- Control Surfaces design
- Evaluation and test review
STEP 5: Flight Testing
At this stage, a prototype is build and will undergo rigorous flight tests.This is a very lengthy and expensive process to ensure quality and safety in the new aircraft, this can take years to complete. There are two different types of aircraft certifications:
Military Aircraft: e.g.: Mil-Specs
Civil Aircraft: e.g.: EASA (Europe) or FAA (USA)
In order to become certified the design must follow these standards, sometimes also referred to as Technical Standard Orders (TSOs) which govern the approval of the design.
STEP 6: Critical Design Review
Here the design is reviewed, final small changes are made to adjust for different needs identified in flight testing.
STEP 7: Certification
Once the aircraft is certified, it can now be allowed into commercial airspace and move into full use and production. During the final certification process there are a wide variety of approvals that are needed to be obtained for design and safety:
- Aircraft Software
- Engines, Propellers, Aux power units
- Human safety factors
- Technical Standard Orders
- Parts Manufacturer Approval
- Origional Design Approval Process
- National Automated Conformity Inspection Process
This myriad of tests and approvals is done to ensure the safe operation and functions of the aircrafts.
Different versions of aircrafts?
Okay, so you have noticed that there are several versions of the Airbus A320 or even Boeing 777. Well, designing an aircraft from scratch is a very long process (15-20 years) and extremely expensive. Hence a solution to this is to modify existing aircraft by upgrading some parts. These newer versions are then released under a different variant name. These can be done much more quickly as most of the aircraft has undergone the approval and certification processes already, this is why you have the Airbus A320 family.