Crew and instrumentation mass held at 180kg – This enables a reasonable-sized test pilot and associated equipment along with an instrumentation mass budget of 70-80 kg, which is reasonable when compared to previous flight experiments at this scale.
Mass of gasoline engine and associated systems included in exchange mass – The mass associated with the (fairly heavy) gasoline engine, stock electrical system (starter, low-voltage battery, etc.), and other accessories such as oil coolers and engine instrumentation were all considered as part of the “exchange mass” available for the electric powertrain and hybrid-SOFC power system.
Mass of hybrid power system estimated based on SOFC sized for cruise power levels – As discussed above, the hybrid SOFC-electric power system was evaluated based on different sizing conditions. The most effective system, detailed in the Boeing companion paper , sized the SOFC for cruise power output plus battery changing loads, and sized the battery to augment SOFC output for takeoff and climb. The scaling and size estimates from the Boeing study were used to estimate the total mass of the power system.
1. Lancair Columbia 300 at Cessna TTx Gross Weight
A promising candidate is NASA Langley’s Lancair Columbia 300  shown in Figure 4. This aircraft was purchased for the NASA Small Aircraft Transportation System Program and is currently in flyable storage, so making substantial changes to its airframe will not impact other test programs. It is powered by a 310hp (230kW) gasoline engine and has approximately 1,000 pounds of useful load (the total weight available for the pilot, passengers, payload, and fuel). Removing the motor, starter, and other associated equipment yields another 500+ pounds in exchange weight to consider for the electric power system. Unfortunately, the empty weight of the retrofitted system would exceed the maximum zero fuel weight of the Columbia 300. However, the current production version of the Columbia 300, branded the Cessna TTx , shares the same major structural design, but has a higher maximum allowable zero fuel weight and maximum gross weight. As such, it may be possible to modify NASA’s existing asset and take advantage of the higher allowable zero fuel weight and gross weight.
Figure 4: NASA Langley’s Lancair Columbia 300.
2. Cessna 172N/P with SuperHawk Supplemental Type Certificate The Cessna 172 is the most-produced aircraft in the world, with over 40,000 aircraft produced, and variants still
in production today. It is used as an entry-level single-engine aircraft by many pilots, and is used for flight training as well as recreational and limited business transportation. Among its many variants, several Supplemental Type Certificates (STCs) are available, including those that boost the gross weight of the aircraft with limited modifications. One such STC offered by Penn Yann Aero boosts the gross weight of older Cessna 172s to 2,550 pounds by, among other things, increasing engine power from 160hp to 180hp . This STC can result in over 1000 pounds of useful load. The estimated exchange weight is over 350 pounds, yielding an impressive amount of weight available at reduced power levels compared to the Columbia 300, enabling a smaller system.
3. Tecnam P2006T
The Tecnam P2006T is a modern, light twin engine aircraft powered by two Rotax 912S gasoline engines. Like the Cessna 172, it is used for flight training (largely for multiengine ratings), but is also used in recreational and limited business transportation roles. It has a useful load of nearly 1000 pounds and an exchange weight of over 400 pounds. A highly modified Tecnam P2006T is being considered for NASA’s SCEPTOR Distributed Electric Propulsion Flight Demonstrator , so it may be possible to leverage the electric propulsion work under SCEPTOR for a future SOFC flight demonstrator. Two different configurations of the Tecnam P2006T were considered – one
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American Institute of Aeronautics and Astronautics