Delivering Pound for Pound Performance in a Precision Crop-Dusting UAS

Delivering Pound for Pound Performance in a Precision Crop-Dusting UAS

by

Daniel J. Hall, Jr.

In Partial Fulfillment of the Requirements for

ASCI 530

Embry-Riddle Aeronautical University

November 1, 2013

Delivering Pound for Pound Performance in a Precision Crop-Dusting UAS

The use of commercial off-the-shelf (COTS) hardware is commonplace in the design and development of unmanned aerospace systems (UAS).  The acronym COTS, within the context of this paper, refers to aviation systems, subsystems, and components available for purchase on the open market.  Sadraey (2013) stated, “In order to minimize cost, it is recommended to select standard parts that are commercially available (i.e., commercial off-the-shelf items) for which there are multiple viable suppliers” (p. 32).  The use of COTS hardware enables the UAS developer to focus on the air vehicle as a collection of systems rather than spending resources on the design and development of each individual system, subsystem, and component.  This approach usually accelerates the design and development process, while reducing cost.

During the design of the precision crop-dusting UAS several errors were made resulting in an overweight condition often faced by aviation systems engineers.  Nicolai and Carichner (2010) stated:

It is almost impossible to estimate the empty weight of something that has not been built (usually with new subsystems and structural materials) with any degree of accuracy.  However, it is important to press on or the aircraft will never be designed. (p. 125)

In this case both design teams should have been more cognizant of their weight budgets and the impact their COTS hardware would have on the final product.  Sadraey (2013) emphasized:

First and foremost, it must be emphasized that any engineering selection must be supported by logical and scientific reasoning and analysis.  The designer is not expected to select a configuration just because he/she likes it.  There must be sufficient evidence and reasons which prove that the current selection is the best. (p. 10)

At this point the system engineers must reevaluate the requirements and specifications stipulated by the customer to ensure they are working towards the desired goals.  Sadraey (2013) wrote; “From the perspective of systems engineering, the design of aircraft should not only transform a need into an air vehicle, but also ensure the aircraft’s compatibility with related physical and functional requirements” (p. 22).  The design team needs to meet with the customer and ensure they understand the requirements and specifications that are absolutely necessary and the requirements and specifications that are flexible.  Perhaps the customer will accept compromises in a design aspect that could save the necessary weight.  For example, the design team may discover the customer really wants the capabilities offered by the COTS hardware and is willing to compromise on the fuel capacity.

If the stated requirements and specifications are absolutely necessary then the system engineers must find a means to meet the weight budget.  This would entail a review of not only the COTS hardware systems in question but all systems on the proposed UAS.  It may be possible to reduce weigh in the airframe, propulsion, or flight control systems.  Sadraey (2013) described this type of analysis as a “trade-off analysis” (p. 28).  “As the name implies, trade-off analysis involves both gains and losses; the gains have to be maximized, and the losses must be minimized.  Trade-off is a compromise made between two or more favorable alternatives” (Sadraey, 2013, p. 28).  Ultimately, a means must be found to meet the customer’s requirements and specifications.  If this is not possible then the system engineers must inform the customer of all available options in order to make a decision on whether to pursue the UAS development or cancel the project.  However, in this case it appears the system engineers have identified the issue early enough in the design process that an acceptable solution can be found and a precision crop-dusting UAS developed, tested, and delivered to the customer.

 

References

Nicolai, L. M., & Carichner, G. E. (2010). Fundamentals of aircraft and airship design. Reston, VA: American Institute of Aeronautics and Astronautics.

Sadraey, M. H. (2013). Aircraft design: A systems engineering approach. Chichester, UK: John Wiley & Sons Ltd.