#### John.Roo

##### Well-Known Member

I suppose that they are not planning to use max. cont. power all the time. 3,5 hours with 92 kWh battery means for example:And their numbers don't make sense. From Wikipedia:

"The 57 lb (26 kg) Siemens SP70D has a takeoff rating of 90 kW (120 hp) and 70 kW (94 hp) continuous. Utah-based Electric Power Systems provides the 92-kWh energy storage including battery modules, management and distribution."

How does a 92 kWh battery provide 3.5 hours endurance at 70 kW? How does a 1900-pound airplane get a climb of 1050 FPM on 120 HP? What sort of 38-foot wing gives a 20.6: L/D at 1900 pounds?

Crew:oneCapacity:one passengerWingspan:38 ft (12 m)Wing area:129 sq ft (12.0 m2)Empty weight:1,460 lb (662 kg)Gross weight:1,900 lb (862 kg)Powerplant:1 × Siemens SP70D[21] electric motor with up to six lithium-ion battery packs, 115 hp (90 kW)Maximum speed:135 kn (155 mph, 250 km/h)Endurance:3.5 hoursMaximum glide ratio:20.6:1Rate of climb:1,050 ft/min (5.3 m/s

There's either some hidden magic, or a lot of mathematical deception. They built one airplane four years ago and flew it two years ago. Got 200 deposits. Are they waiting and hoping for a still-nonexistent battery a lot better than what they have? That's what the Harbour Air electric Beaver is waiting for.

- Takeoff = approx 1,5-2 min. of max power 90 kW

- Climbing = 3-5 min. of 70 kW cont. power

- Cruise = 3,5 hours at 25 kW

In reality will be probably 3 hours cruise and small safety reserve.

I am just wondering what is weight of battery.

In case they use actually available cells will be 92 kWh =+-400 kg (880 lb).

So...

MTOM = 862 kg

EW = 662 kg

And in EW is included:

Battery = 400 kg

Siemens motor = 26 kg

Controller, wiring BMS... = 20 kg

Airframe... lets says = 220 kg

That looks realistically from my point of view.

EW will be probably bit higher (I would say that for pilots will be availabe +-180 kg). And during flight at MTOM 862 kg will be not easy to achieve 25 kW of power for horizontal flight, but with one light pilot....