Concept Selection
This section analyzes the various concepts and highlights the design that will be used to move forward in the project.
The reasoning for the Criteria
The concept designs are created with the goal of short air taxi transport operations with a smaller amount of people in each aircraft. This mission primarily is targeted at business people that don't have time to use traditional ground transport but also have too short of a destination distance to use conventional airport-based regional flights. Fort his purpose, the aircraft's aesthetics play considerable importance. An aircraft's appearance and uniqueness would draw attention from the targetted customers and provide a higher success potential.
Next, the weight of an aircraft's design and propulsion complexity is really high due to the fact that it affects the required research and development cost and time. Complex propulsion requires high maintenance, requires high funding to develop and maintain, and may lead to low reliability. On the other hand, a complex design will require more complex in-depth analysis and maybe even new experiments to discover the feasibility of the design.
Redundancy and configuration stability is weighted with the highest weight since it directly takes part in safety. Redundancy allows the aircraft to safely transport passengers while ensuring their safety even in an event of failure. Configuration stability also allows for the aircraft to be more stable and controllable in a predictable way throughout the operation. This is important to allow crews that were mostly trained in conventional aircraft to be trained safely in this aircraft. This would also allow for safer general operations by eliminating unexpected behaviors.
Design use versatility is weighted similar to the appearance of the aircraft since it allows the aircraft to be used outside of its initial mission which might attract customers. For example; with the ongoing covid-19 restrictions, it may be challenging to allow individuals to travel between cities and provinces but by allowing the aircraft to be used outside of its initial intended role, it may still be used for different services such as cargo. Another major example is to allow the aircraft to be used as an air ambulance or patient and organ transport aircraft. This criteria also measures how the aircraft to be operated in various environments and be modular for multiple different roles. Aircraft designs should take into considerations how it may be used in various regions around Canada and around the world in general. For these reasons, companies may pick an aircraft that can be flown despite economic and environmental changes that lead to minimizing down-time, increasing income.
Evaluation Criteria
The criteria for the weighted trade study are as follows:
Aesthetics with a weight of 3.
Describes how appealing and sleek the appearance of the aircraft is.
Propulsion complexity with a weight of 5.
Describes how complex the VTOL and engine set up could possibly be.
Design Complexity with a weight of 4.
Describes how the aircraft design language and aerodynamic feature may complicate the feasibility of the aircraft.
Redundancy with a weight of 5.
Describes the redundancy potential of the aircraft in the scenario of a partial or full failure.
Configuration stability with a weight of 5.
How stable the configuration of the aircraft is for the VTOL and fixed-wing operation.
Design use versatility with a weight of 3 .
How upgradeable the aircraft is as well as how well it can adapt to various environments.
Cabin space with a weight of 4.
How much space there is for passengers and cargo as well as lifting potential of the aircraft.
Accessibility with a weight of 1.
How accessible is the aircraft in terms of seating, door, and window layout especially for handicapped individuals.
Cabin space is considered important since it allows passengers to be comfortable during travel. The comfort of passengers determines how likely the aircraft will receive positive reviews from customers. This determines how likely customers will use the service again. Better cabin space and layout also improve safety by allowing more room for passengers to evacuate in case of emergencies. Another result for a better cabin space is being able to fit more people reasonably which can decrease cost for passengers and increase profit for companies operating the aircraft.
The last criteria discussed is the accessibility of the aircraft. This involves how the design considers the accessibility for passengers. This primarily affects handicapped individuals that may need to use the aircraft. This section is weighted relatively low considering the main purpose of the aircraft and the size of the aircraft. This aspect is also something that can always be modified for various purposes outside of the initial intended purpose. As an example, the aircraft's doors can be modified and redesigned relatively easily for an air ambulance later down the cycle of the aircraft. Accessibility of an aircraft is an aspect that can always dynamically change depending on the operator and environment that the aircraft is operating in.
Concept 1: Evaluation
This aircraft was rated as one of the worst due to multiple reasons. Starting from the positives, the aircraft's propulsion complexity was relatively simple despite having multiple engines. The set up is essentially just a combination of a helicopter and fixed-wing aircraft at once. However, the small cabin space, mediocre aesthetics, and average design use versatility bring the score to the lower end of the spectrum.
The design use versatility of this aircraft is relatively average or mediocre dues to the smaller cabin space. The size of the wing and the number of engines that need to fit within the fuselage decrease the usable space of the aircraft. Conversion for different uses or passenger configurations can prove to be difficult due to the mediocre layout of the space.
Concept 2: Evaluation
This aircraft was placed at second place closely behind the first place. This aircraft has a relatively simple VTOL concept. This aircraft type has been proven to be capable and useful in the industry by the example of the V-22 Osprey. This aircraft also features a fuselage design that can be modified and extended easily for different purposes outside of the air taxi configuration. The cabin space of this aircraft is also relatively large and can prove to be comfortable while also being able to carry a large amount of cargo. However, the aircraft is considered not considered to be unique compared to the other designs as it resembles the AW609 in design. The aircraft's redundancy can also prove to be average while also having an expensive system to maintain.
Concept 3: Evaluation
This aircraft was placed in the first place during the trade study. This aircraft is very similar in design to the second concept. However, this aircraft utilizes an amphibious fuselage for amphibious operations. This ability allows the aircraft to be utilized anywhere in the world even in areas with large bodies of water. The concept of a VTOL amphibious aircraft is also more unique compared to the second concept.
This aircraft utilizes two turbine engines that drive four different rotors for both vertical take-off and fixed-wing operations. The cabin space of the aircraft can be modular but may have an average to mediocre accessibility due to the height of the door locations. However, during water operations, it can have excellent accessibility since the bottom part of the aircraft will be underwater. This aircraft has the same mechanical cons as the second concept since it utilizes a tilting rotor system.
Concept 4: Evaluation
This aircraft received a perfect score from all three participants in the Aesthetics criterium. The aircraft has a very modern concept and design utilizing lift fans. However, the specified propulsion system was considered to be somewhat complex due to the power transfer system, that is required to power the fans on the wing. Placing the lift fans on the wings also resulted in a thicker wing section which may induce drag. This leads to another reasoning for the average design complexity score it received. Infinity wing design is a complex design that has not been used in a full-size practical aircraft. The redundancy of the aircraft operation was also questioned since it utilizes three critical propulsion systems for VTOL operation. Failure of one of the propulsion systems may lead to the failure of the aircraft.
Concept 5: Evaluation
This aircraft was placed in the third position in the weighted trade study. This aircraft's goal and basic fuselage idea are very similar to Concept 2. Both of the aircraft utilizes a flying boat design which allows them to have a versatile use. However, this also meant that the fuselage must be reinforced. The wing must also be reinforced since it must hold the lift fan system as well as the twin-boom which contains the turbine engines and a third rotor. This design was deemed to be complex and impractical. However, it does have a nicely laid out fuselage design that has a large cabin space as well as simpler accessibility compared to the 2nd design.
Selection Process
Three participants (The author, Josh Ritchie, and Abhishek Singh) rated the different concepts for the concept selection. Each of the scores from the different participants was then summed up to form the NET score for each of the concepts. this method was done in order to reduce bias when selecting the aircraft. The following is the result of the trade study:
Concept 3
Concept 2
Concept 5
Concept 4
Concept 1 (Tied with Concept 4)
Result of the survey.
Selected Concept
This concept was chosen due to its versatility and uniqueness compared to other aircraft. Concept #2 was really close to being chosen for this project due to its practicality and capability. However, it was determined that the concept was far too close in resembling the AW609. While it would implement some new and unique technologies, Concept #3 seen in Figure 1 below prove to be one of the first of such concepts. The chosen aircraft also pose some unique problems that can be both challenging and unique compared to the others.
Figure 1, Drawing of the chosen design Concept #3.