(Replying to PARENT post)

A battery fire is a scary prospect unless the fire can be effectively contained and the hot gases vented (I don't suppose extinguishing one is likely to be an option.) There has been at least one crash involving fire, though I have not been able to find out if it was a propulsion battery fire. [1]

In Eviation's Alice, the failure or shutdown of one of the wingtip's motors would require the shutdown of the other, on account of asymmetric thrust. It can be flown on the rear motor alone, but I do not know how well it would climb in the case of a motor failure on takeoff. Maybe an EE can step in and say whether electric motors can be over-powered for relatively short durations (in this case, a few minutes to return to the airfield) without much increase in the risk of it failing?

BTW, I see that this prototype is a tail-dragger, though rendered images show a tricycle gear.

[1] https://electrek.co/2018/06/04/siemens-electric-plane-protot...

👤mannykannot🕑6y🔼0🗨️0

(Replying to PARENT post)

Electric motors in their specs usually have an entry specifying a 30s or one minute window during which the motor can operate at around twice the power without damage.

In this state the motor cannot maintain temperature, so going beyond that time window will shorten its lifespan or cause damage if continued.

Hobbyst EVs often take advantage of this by having a small motor and overloading it when accelerating.

👤Tade0🕑6y🔼0🗨️0

(Replying to PARENT post)

About the accident in Hungary: the police investigation has been apparently closed, and the cause was ruled to be pilot error (If I understand it correctly, they did a too severe turn too low). There was no sign of a fire before the crash, so even though the wreckage burned out, the crash was not due to electrical issues or fire. A hungarian news article: https://hvg.hu/itthon/20190401_magnus_aircraft_elektromos_ki... (Unfortunately I couldn't find an English article, and the accident investigation of the transportation safety organization might not be finished yet, since they only issued a preliminary report for now.)
👤abeld🕑6y🔼0🗨️0

(Replying to PARENT post)

Assuming battery swaps are the aviation "norm", it might be possible to design the aircraft so that the batteries could be jettisoned in an emergency. This would also give much better glide performance for the emergency, and make the possibility of parachute recovery a lot higher since suddenly there's half as much weight to bring down.
👤erobbins🕑6y🔼0🗨️0

(Replying to PARENT post)

Why so few motors? Electric motors have low cost and low maintenance, so I would expect electrical planes to have many of them.

Overpowering the motor during the entire take-off would bring a high risk of having it fail too. But overpowering it to overcome the most common obstacles is perfectly viable in an emergency.

Anyway, about fires, they are a reasonably easy problem to deal with. Fires on liquid are much more dangerous than fires on solid, and batteries have a lower tendency of exploding and creating fumes than the gasoline that propels smaller planes. I imagine the largest problem of a fire would be on losing power. You can mitigate this by creating many independent battery banks, but this adds weight.

👤marcosdumay🕑6y🔼0🗨️0