Purpose & Scope

The aviation industry has undergone transformative advancements in recent decades, including the adoption of carbon composite materials and the emergence of high-efficiency propulsion technologies such as geared turbofan engines. These innovations have primarily benefited commercial and military aircraft, leaving specialized sectors like agricultural aviation with relatively stagnant development. Recognizing this gap, NASA issued a challenge to U.S. universities to reimagine the agricultural aircraft of the future – emphasizing efficiency, sustainability, and safety.

Aggie Aviation’s response to this challenge is the AA-357: a hybrid-electric, next-generation agricultural aircraft designed for Entry Into Service (EIS) by 2035. Our aircraft is built to meet the rigorous demands of low-altitude operations, short-field performance, and precision agricultural spraying, while complying with Federal Aviation Regulations (FAR) Part 23. The design supports a 2,000lb payload capacity for mission-specific chemicals or materials and integrates innovative systems for autonomous precision farming.

Background

To develop the AA-357, our team conducted a comprehensive aircraft design process using industry-standard methods and custom-built Python tools. Dedicated modules were developed for drag buildup, weight estimation, center of gravity analysis, power loading, V-n diagram construction, and cost modeling. The drag polar model calculates total drag across clean, takeoff, and landing configurations using zero-lift drag (CD0), flap drag, trim drag, and AVL-derived lift-induced drag (CDi). These outputs informed propulsion sizing, mission analysis and overall aerodynamic performance. All geometric inputs were extracted from OpenVSP, while aerodynamic coefficients were validated with AVL to ensure accuracy. Preliminary sizing led to a 35 ft fuselage length and a high-wing configuration for better field clearance and lateral stability. The NACA 2412 airfoil was selected for all lifting surfaces to meet stall and lift performance targets. A full weight breakdown and center of gravity analysis resulted in a maximum takeoff weight (MTOW) CG of 15.079 ft from the nose. The aircraft’s estimated flyaway cost is $1,236,664.46, and the direct operating cost is calculated at $5.03 per cargo ton-nautical mile – significantly outperforming legacy agricultural aircraft in terms of cost-efficiency and sustainability.

Weight Estimation

Each of the weights and component positions in the final weight and CG (Center of Gravity) table was derived either through Raymer-based empirical equations, validated external references (e.g., AT-502B,PT6A specs), or explicit subsystem-level estimates based on real-world avionics and agricultural spraying equipment. This hybrid approach ensures that our final estimates are grounded in both theory and practice. The iterative Python-based weight estimation method allows for dynamic fuel fraction evaluation across multiple flight segments (taxi, climb, cruise, loiter), refining the fuel weight with greater precision than fixed fuel ratios. The final MTOW of 8219.2 lbs, reached through successive convergence, is within a realistic and reasonable range for an agricultural utility aircraft powered by the PT6A-52, which is typically used on aircraft with MTOWs between 7000–10,000lbs.The CG locations reported across various flight scenarios demonstrate a well-balanced air-craft. CG remains in a tight range between 15.46 ft and 15.95 ft across the mission profile, with the most forward location occurring during takeoff (without payload) and the most aft CG at basic operating weight. These shifts are relatively small and reflect a well-trimmed airframe. The location of high-mass systems (e.g., engine, payload, fuel) has been placed thoughtfully along the fuselage to prevent excessive pitch moment arms and minimize CG travel.

From a feasibility standpoint:

• The fuel weight of 1449 lbs is consistent with expected fuel capacity for 2–3 hour missions involving repeated low-altitude spraying passes. This supports a realistic mission endurance while leaving ample room for payload and structural mass.

• The payload of 2000 lbs is comparable to that of the AT-502B and Thrush 510P, validating that our design remains competitive in its class, even if the payload was a crucial part of this assignment and was provided to us as a strict guideline.

• The CG locations fall within a feasible envelope, assuming a MAC (mean aerodynamic chord) of 7.7 ft based on wing geometry. When normalized to MAC and analyzed via static margin plots, the aircraft shows sufficient static stability across all conditions.

• Each subsystem weight (e.g., avionics, electrical, flight controls) was either verified with real component data or computed using conservative Raymer equations, ensuring neither underestimation nor excessive design margin.

Furthermore, the weight breakdown reveals that no single subsystem dominates the air-craft’s empty weight excessively, suggesting a well-balanced design. Notably, subsystems such as the power management system, avionics, and flight control systems are slightly heavier due to the hybrid-electric propulsion configuration. However, these are justified tradeoffs given the intended hybrid operation and mission performance requirements. In summary, the updated weight and CG analysis confirms that our aircraft design is structurally viable, operationally balanced, and realistically achievable with current technology. The data reflects strong alignment with comparable aircraft while meeting the unique demands of hybrid agricultural operations. My full weight analysis is shown below.

Aerodynamics

Write up in progress