At the Ohio Air Mobility Symposium, Whisper Aero CEO Mark Moore revealed a 100 seat commercial aircraft vision concept that the company is calling “Whisper Jetliner” on a panel with Robin Riedel, co-leader of the McKinsey Center for Future Mobility at McKinsey & Company.

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The concept utilizes larger versions of Whisper’s ultra-low noise electric ducted fans integrated into a wing to achieve Upper Surface Blowing, as pioneered by the NASA QSRA flight demonstrator. Moore refers to the integration as a jetfoil because the propulsion system is embedded directly into the wing airfoil while being distributed across the entire leading edge of the wing

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Ultimately, Whisper sees this as a north star for where their propulsion systems can achieve major reductions in carbon emissions across the core aviation market. Whisper has submitted a proposal for the NASA Advanced Aircraft for Sustainable Aviation (AACES) which has recently been announced to provide a path toward net-zero aviation emissions by 2050.

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A holistic approach

Aviation advances in electric propulsion, energy storage, and aircraft integration open up the realm of the possible. These, combined with sustainability goals, infrastructural constraints, economic expectations, and operational pressures, require a reevaluation of current aircraft configurations. Solving environmental challenges requires a holistic approach with detailed understanding of the emerging technologies, coupled to strategies that can economically compete to encourage retirement of the existing hydrocarbon-based fleet.

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Step changes in propulsion have always preceded step changes in aircraft capabilities. In the absence of more advanced, sustainable propulsion solutions, the industry will follow a path of extrapolation with the use of unducted turbofans (e.g., CFM Rise) running on sustainable aviation fuel (SAF).

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This future has high risk of not being economically or environmentally competitive with existing hydrocarbon field aircraft, with fuel prices and higher noise levels that would inhibit aviation sustainability and community friendliness. Whisper Aero feels it’s critical to show future technology pathways that can achieve dramatically better community noise, efficiency, and direct operating costs - all at the same time.

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Details about the aircraft

The Whisper Jetliner is a 100 passenger regional air mobility (RAM) concept seeking to meet these new sustainability goals by leveraging Whisper’s ultra-quiet, ultra-efficient high thrust systems integrated into a jetfoil along its main wing. Through Whisper’s innovations, the team is able to maintain a 27% T/W for the aircraft overall with fan pressure ratios closer to 1.2, as opposed to 1.4 with today’s geared turbofans.

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The reduction in fan pressure ratio increases overall propulsive efficiency allowing regional aircraft to operate with 804 Wh/kg batteries (cell-level, 2050 projections assuming 3.6% improvement year over year) for energy in combination with a 4 MW series hybrid for reserves to achieve battery electric ranges up to 769 miles while satisfying FAA Instrument Flight Rule missions.  

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The jetliner concept leverages an outboard horizontal tail configuration for improved aerodynamics, lower noise at all flight phases, and shorter takeoff and landing field lengths of <3000 ft. Integration of Whisper’s electric ducted fans along the leading edge of a wing increases the aircraft’s wing loading by >20% to increase the cruise high speed lift-to-drag ratio from 17.5 to 22.

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This decreases energy use, and subsequently, direct operating cost while improving passenger ride quality. Whisper has taken learnings from its studies on near-term regional air mobility concepts like its 9 passenger Whisper Jet concept to generate directly applicable insights to much larger aircraft.

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Shift to Sustainability

While much of industry has focused on the very near-term with smaller regional jets and electric vertical takeoff and landing aircraft (eVTOL), Whisper has begun to look at how aviation can feasibly achieve 2050 net-zero carbon goals.

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Global aviation organizations from the FAA, to ICAO, IATA, as well as airlines like Delta, Southwest, and United have pledged to hit these net-zero greenhouse gas (GHG) goals, realizing that aviation accounts for about 2% of global CO2 emissions. Today’s regional airliners generate 0.13 kg of CO2 per passenger per mile.

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For a 700 mile flight, the Jetliners enabled by Whisper’s propulsion systems at full capacity would save 9,100 kg of CO2 each flight, nearly 10 tons, as compared to a similarly sized aircraft flying today.

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Recharging batteries requires 45 minutes with 14 MW chargers, which is the typical turnaround time for similarly sized aircraft today.  The charging and discharge rates are only .7C, enabling high battery cycle life.  Battery electric vehicles using recycled batteries with renewable energy based electricity is the most environmentally friendly approach for achieving environmental goals.

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Reinvigorating Regional Air Travel

Ultimately, achieving sustainability is about the ability to outcompete existing hydrocarbon-based alternatives on operating costs, which would force early retirement of existing fleets. From 1995 to 2020 commercial aircraft carriers (such as Southwest Airlines) have increased their U.S. domestic average trip stage length from 401 to 678 miles, as lower load factors and less profitable service across regional city pairs has been discontinued.

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Battery electric commercial aircraft have a compelling economic advantage at these shorter trips due to lower energy and propulsion maintenance costs (turbines experience increased hot-cold cycles at shorter trips that increases their maintenance burden). Energy costs for a typical 500 mile trip are $733 for the Whisper Jetliner (@$.07 kWhr industrial electricity rates) compared to $2,100 (@$2.00/gallon JP fleet based fuel price) for an equivalently sized current commercial aircraft (e.g. Airbus A320-100).

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The Whisper 100 passenger Jetliner concept can meet the range required at typical U.S. domestic distances to reinvigorate regional airports across mid-sized cities. This spreads out air travel from congested major hubs and provides greater convenience and choice for shorter trips that occur more frequently than long distance trips.

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Quieter, more efficient propulsion across jetliner flights can further improve passenger experience and community friendliness. Lower noise at all phases of flight due to Whisper’s propulsive improvements can quiet cabin noise and reduce neighborhood noise impacts, further increasing the amount of airports available to operators. Whisper quiet flight will allow for these future jetliners to even operate at night for faster, more affordable cargo transportation.

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The dramatic decrease in noise enables long sought after capabilities such as “Intermodal” fuselage concepts to be implemented to perform passenger operations during the day and cargo operations at night, with a 15 minute “Quick Change” capability through a cassette that replaces palletized seats with cargo containers. Such a capability increases the daily utilization of the aircraft, enabling improved amortization of fixed costs over more operating hours. Electric vehicles excel at achieving lower operating costs, so the combination of these approaches is highly synergistic.

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