I was lucky enough to help Composite FX at Oshkosh 2022 when they reviewed their first Electric Prototype. First stats is that it will hover 20-25 minutes and 45 minutes in forward flight. Testing continues along with development of enhanced performance of their 285/290 variants. CFX is now producing their own rotor blades, which are now flying and are developing an engine that will replace the MZ 202 in the XEL and XE models.
I’m very curious to hear what numbers CFX is measuring.
I have a liquid cooled EMRAX 228 motor in my electric Mosquito, CFX uses the combined cooled motor which can handle 15% more power.
My longest flight so far was 14 minutes which included six climb outs and autos. Motor temperature reached 83C with an OAT of 27C. DA was 1400ft and average motor power about 22kW. From the temperature graph it can be seen that continuous operation under these conditions is possible.
For the same motor temperature the CFX motor will be able to deliver about 3kW more, around 25kW. Unfortunately from measurements I did the tail rotor alone will eat up more than that, my saving grace is that my EMRAX motor does not have to drive a tail rotor because I have an electric tail driven by separate motors.
The CFX machine does have larger diameter rotors (19.5 foot vs my 18 foot) which should give better efficiency. What I have measured though is that the profile drag of the rotors is very high. At zero lift and 540 rrpm the 18 foot rotor consumes 7kW, a 19.5 foot rotor will consume much more. To reduce power the rrpm will need to be lowered, something I can easily do with my aircraft empty weight of 135kg, but unlikely an option considering the weight of the CFX machine.
I will thus be surprised if the motor in the CFX machine will be able to handle a flight of more than about 10 minutes, especially on a warm day.
Another thing is that the inverter in the CFX machine is air cooled and mounted horizontally. I suspect temperature limits will again be reached after about 10 minutes with that configuration, water cooling will be necessary for continuous operation.
The EMRAX 228 is the perfect motor for a lightweight single seat helicopter, especially when running an electric tail. The current CFX machine with conventional tail might just be asking a bit too much from it.