This paper explores the design spaces of a thin-haul and a regional aircraft with parallel hybrid-electric propulsion architectures for a 2030 entry into service date. Notional technology reference aircraft models were developed for a 19- and a 50-passenger aircraft based on publicly available data on Beechcraft 1900D and ATR 42-600, respectively. A set of airframe and propulsion system technologies projected to reach maturity by 2030 was infused into the aircraft models. Parametric, physics-based models were created for the charge-depleting hybrid architecture. Different modes of operation were identified and parameterized with a range of design variables to investigate the feasibility and trade space for peak power shaving, climb power boosting, electric taxi, battery usage schedules, and in-flight battery recharge strategies. Thousands of electrified aircraft concepts with varying electrification, operation, and technology scenarios were sized under the same system-level requirements as their conventional counterpart. The resulting multidisciplinary design space exploration environment was used to identify the optimum vision system designs and modes of operation for the minimum block fuel-burn objective. It has been found that both vehicle classes with the charge-depleting parallel hybrid electric architecture provided fuel-burn benefits over their 2030 advanced technology counterparts under certain operational modes.

Airworthiness certification is a mandatory but expensive process in aircraft development. To reduce certification cost, it is desired to incorporate certification considerations into aircraft early...

Distributed electric propulsion (DEP) concepts leverage the synergistic benefits of aeropropulsive coupling and improve the overall flight efficiency by placing propulsors at optimal locations, such as the wingtip. However, placing propulsors far away from the aircraft centerline may bring aircraft difficulties in complying with critical-engine-inoperative flight certification rules. To investigate the impact of certification requirements on the DEP aircraft design, this paper takes NASA’s PEGASUS concept as a use case and presents a study of certification-constrained vertical tail sizing and propulsive power split optimization. For comparison, a vertical tail retrofit study is also conducted on the ATR 42-500 aircraft using the same design space, to gain insights into the different impacts of certification constraints on the design process between conventional and unconventional aircraft. In each study, a design space exploration is performed, including a feasibility test and a multi-objective optimization. The feasibility test shows that the certification constraints yield a much smaller feasible design space for the DEP concept when compared to the conventional aircraft. Despite a much smaller feasible design space, the constrained Pareto optima of the PEGASUS still exhibit lower cruise drag coefficient, fuel burn, and operational energy cost when compared to those of the ATR 42.

To ensure flight safety, a set of flight certification rules are defined at critical-engine-inoperative (CEI) conditions for conventional fuel-powered tube-and-wing aircraft. However, the definition of CEI is unclear for distributed hybrid-electric propulsion aircraft, where a single propulsor can be driven by multiple power sources in parallel and/or propulsive power can be unevenly distributed among power sources. These innovative designs necessitate a revisit of CEI conditions for the demonstration of certification compliance. This paper proposes a potential solution for determining critical propulsion failure states and demonstrating the equivalent safety level for distributed hybrid-electric aircraft through reliability analysis and flight dynamic simulations. As an example, NASA’s PEGASUS aircraft is selected as the use case. The failure rates of propulsive failure states computed using a Bayesian modeling approach indicate that PEGASUS’s overall reliability is improved compared to its conventional counterpart despite its more complex propulsion architecture. The flight dynamic simulations show that PEGASUS requires at least 45% of maximum power at sea level for takeoff and maintaining steady level flight. To satisfy the controllability constraints specified in CEI rules, the yawing moment induced by asymmetric loss of thrust may not exceed 1.7 times that induced by the critical engine failure of the ATR 42-500.

Exploring the performance potential of conventional tube-and-wing aircraft is imperative to bridge the gap for sustainable aviation until the adoption of novel configurations. This paper investigates the strategy of reducing design range and cruise speed for the conceptual design of next-generation single-aisle aircraft. The impacts on fuel consumption are evaluated at both vehicle and fleet levels. Performance analysis shows that simultaneously optimizing aircraft design parameters and cruise Mach number can reduce mission fuel burn by 3% compared to the fixed-Mach optimization. The reduced cruise speed also maximizes the benefit of natural laminar flow technology, yielding an additional 5% fuel saving. Shorter design ranges result in smaller airframes and engines, reducing fuel burn by about 1.4% per 500 nmi decrease relative to the long-range vehicle operating at its off-design missions. Tradeoffs between aircraft range capability and fuel savings are captured by the fleet analysis. The results show that 6% of the flights operated by large single-aisle aircraft become infeasible if the aircraft design range reduces to 1500 nmi. The projected 2050 fleet-level fuel savings vary non-monotonically with reduced design ranges, with the highest reduction of 6.4% achieved by a 2500 nmi design among six optimized candidates.