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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 o

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-prototype-fire-crash-death/ https://electrek.co/2018/06/04/siemens-electric-plane-protot...

Tade0 7y ago
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.
- mannykannot 7y ago
  That's probably OK: having to replace a motor would be a small cost compared to that of an off-field forced landing that went badly.
  - sandworm101 7y ago
    >> off-field forced landing that went badly. Parachutes. They are now a very practical option for GA aircraft. More than a few cessnas have been saved. The concept of "off-field forced landing" should too be going away. https://brsaerospace.com/cessna-faqs/ https://brsaerospace.com/cessna-faqs/ " Q. How many aircraft saves are credited to a BRS Whole Aircraft Rescue Parachute System? A. As of August 2017, 376."
    - verelo 7y ago
      "Q. How much damage will be done to my plane if I land it with a parachute? A. In all likelihood the aircraft will suffer some significant damage. The terrain where you land will affect this greatly. Though the extent of damage has varied from plane to plane, most GA aircraft that have come down under a BRS deployment have eventually (or will soon) fly again." Call me a skeptic until they provide hard numbers and details of what planes make it back into the sky v's scrapped, and those planes have a year or two of a service history showing they make it back into a reasonable service lifestyle, I'd be shocked to hear this is great at saving planes. I find a lot of the old 172's i fly have plenty of bumps and scratches, but wouldn't be super excited to trust the frame of a plane that went through an experience like this. I like it from a safety perspective, but in my mind, the reward you get out of a system like this should be your life...I have zero expectations the plane will ever fly again.
      - codeduck 7y ago
        If the plane is designed to take a BRS then there is a good chance that after some (admittedly costly) repairs it will take to the air again. A 172 or similar that has been retrofitted with a BRS? Yeah, not so much.
        mannykannot 7y ago
        It seems that, at least until fairly recently, most Cirrus aircraft that used their parachute were written off, and that is still the most likely outcome. https://aviation.stackexchange.com/a/1122 https://aviation.stackexchange.com/a/1122
      - sandworm101 7y ago
        How many are written off is irrelevant. What matters is passenger lives. Success is measured in total number of not-dead people because of not crashing as violently.
        verelo 7y ago
        Agreed.
marcosdumay 7y ago
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.
- mannykannot 7y ago
  A fire in an airplane is a lot more scary than a loss of power (proportionally more so in a small airplane, where an off-field landing is feasible, and increasingly they have ballistic parachutes), while there is currently a well-known problem of fires (that can't be extinguished) in high-power-density batteries. Gasoline is dangerous, but we have learned how to handle it safely.
  - rbanffy 7y ago
    You could mount batteries on pods that could be released if needed. Additional benefit would be that the pods could be replaced on the ground by fully charged ones for faster turnaround.
    - vosper 7y ago
      You can't really rain burning battery pods down on the landscape, though. What if the plane is over a populated area?
      - deleted 7y ago
        [deleted]
      - zdragnar 7y ago
        Or a dry forest, or grassland. Burning lithium probably can't be all that good for ponds, rivers or lakes either.
erobbins 7y ago
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.
abeld 7y ago
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_kisrepulo_lezuhant_baleset_halalos_aldozatok_rendorsegi_nyomozas 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.)

Tade0 7y ago

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.

mannykannot 7y ago
That's probably OK: having to replace a motor would be a small cost compared to that of an off-field forced landing that went badly.
- sandworm101 7y ago
  >> off-field forced landing that went badly. Parachutes. They are now a very practical option for GA aircraft. More than a few cessnas have been saved. The concept of "off-field forced landing" should too be going away. https://brsaerospace.com/cessna-faqs/ https://brsaerospace.com/cessna-faqs/ " Q. How many aircraft saves are credited to a BRS Whole Aircraft Rescue Parachute System? A. As of August 2017, 376."
  - verelo 7y ago
    "Q. How much damage will be done to my plane if I land it with a parachute? A. In all likelihood the aircraft will suffer some significant damage. The terrain where you land will affect this greatly. Though the extent of damage has varied from plane to plane, most GA aircraft that have come down under a BRS deployment have eventually (or will soon) fly again." Call me a skeptic until they provide hard numbers and details of what planes make it back into the sky v's scrapped, and those planes have a year or two of a service history showing they make it back into a reasonable service lifestyle, I'd be shocked to hear this is great at saving planes. I find a lot of the old 172's i fly have plenty of bumps and scratches, but wouldn't be super excited to trust the frame of a plane that went through an experience like this. I like it from a safety perspective, but in my mind, the reward you get out of a system like this should be your life...I have zero expectations the plane will ever fly again.
    - codeduck 7y ago
      If the plane is designed to take a BRS then there is a good chance that after some (admittedly costly) repairs it will take to the air again. A 172 or similar that has been retrofitted with a BRS? Yeah, not so much.
      - mannykannot 7y ago
        It seems that, at least until fairly recently, most Cirrus aircraft that used their parachute were written off, and that is still the most likely outcome. https://aviation.stackexchange.com/a/1122 https://aviation.stackexchange.com/a/1122
    - sandworm101 7y ago
      How many are written off is irrelevant. What matters is passenger lives. Success is measured in total number of not-dead people because of not crashing as violently.
      - verelo 7y ago
        Agreed.

marcosdumay 7y ago

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.

mannykannot 7y ago
A fire in an airplane is a lot more scary than a loss of power (proportionally more so in a small airplane, where an off-field landing is feasible, and increasingly they have ballistic parachutes), while there is currently a well-known problem of fires (that can't be extinguished) in high-power-density batteries. Gasoline is dangerous, but we have learned how to handle it safely.
- rbanffy 7y ago
  You could mount batteries on pods that could be released if needed. Additional benefit would be that the pods could be replaced on the ground by fully charged ones for faster turnaround.
  - vosper 7y ago
    You can't really rain burning battery pods down on the landscape, though. What if the plane is over a populated area?
    - deleted 7y ago
      [deleted]
    - zdragnar 7y ago
      Or a dry forest, or grassland. Burning lithium probably can't be all that good for ponds, rivers or lakes either.

erobbins 7y ago

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.

abeld 7y ago

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_kisrepulo_lezuhant_baleset_halalos_aldozatok_rendorsegi_nyomozas 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.)