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Bye Aerospace unveils 8-seat all-electric eFlyer 800; Safran supporting propulsion design

Bye Aerospace announced an eight-seat all-electric twin turbo-prop class airplane, the eFlyer 800. Performance estimates for the eFlyer 800 include up to 320 knot cruise speed, 35,000 feet ceiling and 500 nm range with 45-minute IFR reserves at normal cruise speed of 280 knots.


Safety features include two wing-mounted electric motors, each with dual redundant motor windings, quad-redundant battery packs and a full airplane parachute. Additional potential features include emergency auto-landing system; intelligent algorithm ensuring envelope protection; terrain avoidance and routing for emergency auto-land; and an option for supplemental power solar cells and in-wheel electric taxi.

The airplane’s 8-seat configuration consists of up to seven passengers and one or two pilots. The eFlyer 800 will have only one-fifth the operating costs of traditional twin turboprops and is geared for the air-taxi, air-cargo, regional and charter aircraft markets.

The eFlyer 800 is the first all-electric propulsion technology airplane that achieves twin-turboprop performance and safety with no CO2 and extremely low operating costs. This type of remarkable economy and performance is made possible by the electric propulsion system and advanced battery cell technology that results in significantly higher energy densities.

—George E. Bye, Bye Aerospace CEO

Bye Aerospace and Safran are currently assessing the most efficient electric powertrain for the eFlyer 800 (dual ENGINeUS electric motors and GENeUSGRID electric distribution and network protection system).

Safran product lines with the ENGINeUS motors, rated from 50kW to 500kW/1MW and GENeUSGRID systems, perfectly fit with the Bye Aerospace portfolio of e-aircraft. Building upon our successful cooperation on eFlyer 2 and eFlyer 4, we are very proud to bring our best expertise to support Bye Aerospace in the design of the new eFlyer 800.

—Hervé Blanc, Executive Vice President and General Manager Power with Safran Electrical & Power

Safran presented the first electric motor from its ENGINeUS range designed for future hybrid and electric aircraft, at NBAA’s Business Aviation Convention & Exhibition (NBAA-BACE) in Orlando, Florida in 2018. The ENGINeUS 45 motor has a continuous power of 45kW. It has built-in, dedicated control electronics with an energy efficiency of more than 94%. It also has an excellent power-to-weight ratio of 2.5kW / kg at 2,500rpm. The ENGINeUS product line will eventually include a range of electric motors with a power output of up to 500kW.

Bye said eFlyer 800 customer deposit agreements are complete, and several are being developed with US and European air-taxi, air-cargo and air charter services. Details will be forthcoming when the agreements are finalized.

Bye Aerospace is in the process of obtaining FAA Part-23 certification for the eFlyer 2 for the professional flight training mission and the four-seat eFlyer 4 for air taxi, cargo and advanced training uses.



I was hunting for the details of the battery to enable all this, and just got that they were witholding what they use.

And also:

' Bye will not name the propeller suppliers or products under evaluation, but says the selection will be based on the aerodynamic performance and lightweight design of each system.'


'An enterprise of great advantage, but nobody to know what it is.'

Bob Niland

For electric a/c, the IFR Reserve requirements are a steep challenge. Under US FAR Parts 121 & 135 (and Part 91, for personal IFR ops), they amount to perhaps an extra hour of endurance on top of mission range. I'm, umm, surprised to see a claim of it this early in the e-flight age.


@bob, they might have to change the rules for IFR for electric aircraft, for the reasons you have given. As they say, it has a full airplane parachute, though I wouldn't like to test it. The rules for energy dense chemical fuel may be different for energy poor batteries.
Or someone may crack H2 and off we go.
However, it is a long way from a 45 kW electric motor to a 1850 kW as used in an ATR72.

Bob Niland

Mahonj, although we occasionally see relaxation of rules (such as for ETOPS), and ICAO is already a bit more liberal for IFR reserve than FAA for turbine engines, if I were developing electric aircraft, I don't think I'd count on it happening. The reserve requirement arose from factors not necessarily related to motor & fuel type.

Moeller might still be waiting for {unrelated} regs changes to green light the Skycar.

Account Deleted

Bye Aerospace has been collaborating with Oxis Energy on Lithium Sulfur batteries (https://byeaerospace.com/bye-aerospace-oxis-energy-begin-collaboration-to-increase-the-endurance-of-future-bye-aerospace-eaircraft/).


Thanks gryf.
That explains the projected performance.
Pretty speculative stuff though, hardly prime time ready for reliable operational use I would have thought.



Phil Brooke

Range of 500 nm?

Account Deleted

From Forbes Apr 21, 2021,"Electric Aviation Trailblazer Bye Aims To Dethrone The King Air"
"Bye’s plans for the eFlyer 800 are based on the assumption that it will have battery cells containing 550 Wh/kg in energy; Oxis says it will achieve that by 2023."
You can read more details here:

Bob Niland

Oxis, interestingly, lists their top 2 advantages as energy density and safety. Their site seems silent on charging rate. What are the expectations for Li-S on this?


VFR (Visual Flight Rules) requires 30 minutes fuel reserve during daylight and 45 minutes fuel reserve during night operations. IFR (Instrument Flight Rules) require 45 minutes fuel reserve (or energy reserve in this case) at normal cruise.

The first generation Quasi Solid-State Li-S cell at 450 Wh/kg Specific energy with an Energy density of 550 Wh/L will be delivered by the Summer of 2022. A target of 550 Wh/kg, 700 Wh/L has already been set for the Autumn of 2023. Independently of the above, OXIS has set forecast targets of 600 Wh/kg and 900 Wh/L to be achieved by 2026.

See: https://www.greencarcongress.com/2021/04/20210421-oxis.html

You might get longer range with hydrogen but for ranges up to the quoted 500 nm (925 km) range, battery operations will be much lower cost. I think that I would bet on the batteries.


Also see:



' Cycle life

OXIS Li-S scientists are constantly improving our Ultra Light cell. Within the next two years we aim to double the current cycle life to achieve upwards of 500 cycles.'


So it is still in the 'nice if it works' category, and even 500 cycles is not great.


To be clear although I have posted many comments here favourable to hydrogen and fuel cells, I have absolutely nothing against using batteries wherever they are an effective solution.

I felt and feel that the hype was overdone on batteries, whilst enthusiasts discount fuel cells far too much, but so long as the job is done, I am happy with either solution.

Account Deleted

There is another Lithium Sulfur battery from LG that also looks promising.
It was tested last year by the Korea Aerospace Research Institute in an EAV-3 drone (see: http://www.businesskorea.co.kr/news/articleView.html?idxno=51623).

The LG battery uses Carbon Nanotubes and LG Chem recently launched the largest carbon nanotube (CNT) manufacturing plant in Korea and is actively targeting the CNT market for cathodes in electric vehicle batteries.(read:https://www.greencarcongress.com/2021/04/20210421lgchem.html#comments).
An open access technical report describes CNT use in work supported by LG Chem.
"Achieving three-dimensional lithium sulfide growth in lithium-sulfur batteries using high-donor-number anions",Nature Communications volume 10, Article number: 188 (2019), https://doi.org/10.1038/s41467-018-07975-4).


gryf, all great if they work.

This has not yet even reached prototype stage though, and there are a million things that could stop production.

I am afraid I just concentrate on things which are less speculative.


To meet those specs, 40% of the gross weight of this aircraft will be batteries if we assume 500wh/kg.

That will require be some impressive lightweighting of the airframe vs current aircraft (e. King Air B200)

Seems difficult.

Account Deleted

Not sure about what you are basing your estimates. However, if one assumes a 750kWh battery mentioned in the Forbes article, then that equates to 1500 kg or 3300 lbs @500 Wh/kg. If you use a 10,000 lb GTOW then that equates to 33% of the GTOW for the battery. (The Beechcraft King Air C90 has a 10,000 lb GTOW.
Another similar aircraft (A special Beechcraft King Air 350ER has a 31.5% fuel to GTOW mass (reference: "King Air 350ER: Flying Fuel Tank", https://www.flyingmag.com/pilot-reports/turboprops/king-air-350er-flying-fuel-tank/).

Account Deleted

BTW a Beechcraft King Air C90 has a 2573 lb fuel weight.


Pye in the sky. A King Air burns c.a. 500 lbs/hr at cruise (250 kts) = 2700 kWh/hour (of fuel). 35% efficient so 950 kWh needed at 100% efficiency. Electric would be 85% efficient from electrons to propulsive power so needs 1100 kWh/hour = 2.2 tonnes of Oxis battery per hour at even an optimistic 500 Wh/kg. 4.4 tonnes of battery for 2 hours cruise, plus reserve. MTOW of a 7 pax C90 = 4600 kg. Non starter. Even with a cleaner, lighter airframe how much can you improve? Well if they went BWB/ lifting fuselage they'd reduce drag 20% at least, have radically better payload to emty weight ratio and have more wing room for batteries - I'd say the standard wing and fuselage design has no chance with battery power. May have some chance with a fuel cell and high pressure gaseous H2, not done the numbers.


A few advantages over turboprops:
1. Efficiency of gas turbines at loitering power levels (for reserve) are really bad. Efficient slower flying capability with a larger wingspan will work in favor of the reserve requirements.
2. Regen during descent should save energy and allow steeper later descents maybe saving time also.
3. Air breathing engines lose power with altitude, proportional to density. Larger propellers will allow the same electric motors to push the aircraft much faster at higher altitude.


A Fool Cell has no chance at high altitudes.

The Lurking Jerk

The drastically lower cost of flight miles, increased reliability and reduced complexity has too much potential profit for electric aviation not to take off. In fact, aviation is going to wind up being a major driver of electrification, and much more crowded skies will be one likely result.
I realize Bye is bordering on Eeestor-like vapor, but the potential earnings are going to move the development forward in a way that will surprise us all.

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