Electric planes

[petit_bateau]

What I didn’t see on the Jetson was variable-pitch or feathering props, likely because of complexity, weight, and cost. If a motor fails and the propeller blades cannot feather (rotating the blades on their hub to a position such that the airflow through them provides the least drag), then the dead prop is a huge aerodynamic liability, only slightly less so if it freewheels. In a true helicopter after engine failure, the aircraft falls pretty much like a rock. The pilot flattens the blade pitch and the airflow upward through the blades keeps them turning at speed allowing surprising lateral mobility. Just before crashing into the ground, the pilot Increases the pitch on the blades trading off blade rpm and momentum for a cushioned landing. Works very, very well. No go-arounds though, it’s a commitment and one-time thingie. For the Jetson, having eight motors somewhat mitigates the autorotation issue though, but not the feathering (drag) problem. And for an electric failure at the source (battery), the Jetson pilot is definitely landing immediately and uncomfortably. I would like to see some single- and multi-engine-out landings on their website.

All that said, I’d love one of these.

I think that feathering isn't really relevant in a quadcopter of this nature. The stopped prop is not presenting any more drag (in the forwards direction) than a running prop (actually less). And there is no asymetrical drag issue to be concerned about in respect of loss of control surface effects. The only minor ? effect of a stopped prop is th eextent to which it might present a flow obstruction to the axially in-line paired rotor/motor; and that will depend on failure mode. So simple rigid fixed pitch props are best for simplicity and weight and cost.

I wonder to what extent the electrical systems are split and/or redundant. Perhaps there are 2 battery systems each driving 4 props via 4 motor VSDs. And perhaps loss of one group results in a quick controlled descent scenario.

The conceptual design FMEA and HAZOP on this must be quite interesting.

 

[RichAZ/CapeCod]

If it goes down in the water and you had the presence of mind to unclip your safety belt before hitting the water, you might not get dragged down with it. Planes often float, at least for a bit, if they ditch in the water and the pilot is good. I'll bet this thing sinks like a rock.
...

"...

unclip your safety belt before hitting the water..."

Bad idea. I was taught (this was for rotary-wing ditching in water) that to ensure the most likely survival of such an event:

Once your craft has hit the water, twist your body toward the exit door and place your hand on the door handle. By this time, although it might be a bright sunny day ten feet over your head (above the water) your world will be opaque rushing water.

DO NOT RELEASE YOUR SEAT BELT UNTIL YOU HAVE YOUR HAND ON THE DOOR HANDLE!!!!

If you do so you will "float" to the top of the machine (which will likely be where the floor is), become completely disorientated, and drown.

Once you have opened the door (water has to stop rushing in in order to do this), THEN unclasp your seat-belt and push out of the machine.

When you find yourself above the surface of the water, and your co-pilot or other crew member is still in the craft, DO NOT GO BACK DOWN TO RESCUE THEM.

If you try to do that the recovery team will be recovering your body along with theirs.

Hopes this cheers everyone up.

Rich

Coast Guard helicopter ditching training

 

[Etna]

I wonder to what extent the electrical systems are split and/or redundant. Perhaps there are 2 battery systems each driving 4 props via 4 motor VSDs. And perhaps loss of one group results in a quick controlled descent scenario.

The conceptual design FMEA and HAZOP on this must be quite interesting.

The various electric propulsion systems I have looked into so far were all quadruple redundant. Four groups of batteries, primary busbars, cabling, etc. There is basically no weight penalty and it makes a few things easier to manage like cabling radius, HIRF, etc.

The FMEA stuff being interesting is quite the understatement. I have touched a bit of the FMECA analysis of a hybrid-electric propulsion system and it is mind blowing.

 

[STS-134]

A person flying at treetop height had better have very good eyes and very sharp reflexes.

Even with perfect reflexes, I'm not sure if you'd be able to land safely if a motor failed at just the wrong time. I'm not sure what reason there was to fly that low (other than just being a moron). Altitude just gives you so much more room for error because you can exchange it for airspeed and reaction time. I've flown my drone fairly low over the trees before but the difference is if a motor fails on my drone, I don't go down with it.

 

[RichAZ/CapeCod]

Even with perfect reflexes, I'm not sure if you'd be able to land safely if a motor failed at just the wrong time. I'm not sure what reason there was to fly that low (other than just being a moron). Altitude just gives you so much more room for error because you can exchange it for airspeed and reaction time. I've flown my drone fairly low over the trees before but the difference is if a motor fails on my drone, I don't go down with it.

There are few things more valuable to a pilot in the event of an emergency in flight or when experiencing a mechanical failure:

The distance between you and the ground (higher is better), and,
Your airspeed (more is better).

Just sayin'...

Rich

 

[daniel]

Bad idea. I was taught (this was for rotary-wing ditching in water) that to ensure the most likely survival of such an event:

Once your craft has hit the water, twist your body toward the exit door and place your hand on the door handle. By this time, although it might be a bright sunny day ten feet over your head (above the water) your world will be opaque rushing water.

DO NOT RELEASE YOUR SEAT BELT UNTIL YOU HAVE YOUR HAND ON THE DOOR HANDLE!!!!

If you do so you will "float" to the top of the machine (which will likely be where the floor is), become completely disorientated, and drown.

Once you have opened the door (water has to stop rushing in in order to do this), THEN unclasp your seat-belt and push out of the machine.

When you find yourself above the surface of the water, and your co-pilot or other crew member is still in the craft, DO NOT GO BACK DOWN TO RESCUE THEM.

If you try to do that the recovery team will be recovering your body along with theirs.

Hopes this cheers everyone up.

Rich

Coast Guard helicopter ditching training

From the pictures, the Jetson appears to be completely open, just surrounded by a roll cage. Your emergency description applies when you are inside a cabin. It's a completely different matter if, as the craft sinks, you can just stay floating on top of the water. Furthermore, an enclosed cabin might remain floating for a short while, until sufficient water has entered for it to become negatively buoyant. In the absence of a cabin, the Jetson would not pause on top of the water. It would hit the water and just keep going down. If you are strapped in, it will pull you down with it, right to the bottom. Your only hope is to NOT be strapped in when it hits. Then MAYBE, if the cage frame does not catch you, you might get free and stay on, or swim to, the surface.

More likely it will pull you right to the bottom. Then your survival will depend on the depth and your swimming/freediving skills. And how badly the impact injured you.

Flying over water would be safer in a floatplane. It's designed to land on the water and stay afloat.

(I've flown in a floatplane, twice, one trip, out and then back afterwards. It was very cool. Regularly-scheduled commercial service. One engine. Six or eight passenger, IIRC.)

 

[petit_bateau]

There are few things more valuable to a pilot in the event of an emergency in flight or when experiencing a mechanical failure:

The distance between you and the ground (higher is better), and,
Your airspeed (more is better).

Just sayin'...

Rich

Tell me again how airspeed is relevant to a quadcopter ?

(Height is more of an "it depends" thing.)

From the pictures, the Jetson appears to be completely open, just surrounded by a roll cage. Your emergency description applies when you are inside a cabin. It's a completely different matter if, as the craft sinks, you can just stay floating on top of the water. Furthermore, an enclosed cabin might remain floating for a short while, until sufficient water has entered for it to become negatively buoyant. In the absence of a cabin, the Jetson would not pause on top of the water. It would hit the water and just keep going down. If you are strapped in, it will pull you down with it, right to the bottom. Your only hope is to NOT be strapped in when it hits. Then MAYBE, if the cage frame does not catch you, you might get free and stay on, or swim to, the surface.

More likely it will pull you right to the bottom. Then your survival will depend on the depth and your swimming/freediving skills. And how badly the impact injured you.

I used to commute over water by helicopter for many years, and have done various civilian and military dunkers on many occasions; for a wide variety of helicopters around the world, over about 35 years. Including 'owning/operating' them. At that point 'we' were experiencing helo-related fatalities most years (largely ditching/crashing at sea) and it did concentrate minds. So I'm not an expert but I am reasonably well informed.

You definitely want to be strapped in on impact so as to let the airframe transmit/absorb the loads in as planned (designed) a manner as possible, and for the very immediate crash-motions (or controlled ditching) to subside. (nobody wants 150-200kg of uncontrolled human spreading themselves all over the cabin and over/through the other occupants). What follows after that is very dependent on the chopper type & configuration; impact damage or pre-impact damage; sea state/etc; and where you are located (seated) as well as what is going on around you; and how you are equipped and trained. This is just as true up front as in the back. Some types will be descending underwater inverted nose down rapidly within seconds (Wasp, Lynx, etc). Others have a reasonable prospect of being stable and upright, or stable and horizontally upside down.

There are seats you definitely don't want to be in for some types as well. The far back centre seat in the Super Puma for example is particularly unloved. Or the seats where the door slides across and obstructs the emergency exit window.

It really does all depend.

This Jetson thing probably isn't great, but nor is it a disaster from an egress perspective. There is clearly consideration given to creating a safety cell around the occupant. A lot would depend on how it came to land/impact the surface(s). Sometimes these instances simply aren't survivable.

 

[SalisburySam]

…150-200kg of uncontrolled human…

Sumo wrestler?

 

[petit_bateau]

Sumo wrestler?

Let's just call them 'bears'.

(I actually edited out the first term I wrote so as not to upset anyone. You definitely don't want to be in that back middle seat waiting for some folk to move gracefully through the egress options ....)

 

[daniel]

Tell me again how airspeed is relevant to a quadcopter ?

(Height is more of an "it depends" thing.)



I used to commute over water by helicopter for many years, and have done various civilian and military dunkers on many occasions; for a wide variety of helicopters around the world, over about 35 years. Including 'owning/operating' them. At that point 'we' were experiencing helo-related fatalities most years (largely ditching/crashing at sea) and it did concentrate minds. So I'm not an expert but I am reasonably well informed.

You definitely want to be strapped in on impact so as to let the airframe transmit/absorb the loads in as planned (designed) a manner as possible, and for the very immediate crash-motions (or controlled ditching) to subside. (nobody wants 150-200kg of uncontrolled human spreading themselves all over the cabin and over/through the other occupants). What follows after that is very dependent on the chopper type & configuration; impact damage or pre-impact damage; sea state/etc; and where you are located (seated) as well as what is going on around you; and how you are equipped and trained. This is just as true up front as in the back. Some types will be descending underwater inverted nose down rapidly within seconds (Wasp, Lynx, etc). Others have a reasonable prospect of being stable and upright, or stable and horizontally upside down.

There are seats you definitely don't want to be in for some types as well. The far back centre seat in the Super Puma for example is particularly unloved. Or the seats where the door slides across and obstructs the emergency exit window.

It really does all depend.

This Jetson thing probably isn't great, but nor is it a disaster from an egress perspective. There is clearly consideration given to creating a safety cell around the occupant. A lot would depend on how it came to land/impact the surface(s). Sometimes these instances simply aren't survivable.

Okay. I'm NOT flying a Jetson over water! (That is, if I were ever going to fly one at all. )

Sumo wrestler?

Or a pilot plus one or two passengers.

 

[Earl]

but not the feathering (drag) problem.

Drag really isn't much of a problem with a multi-rotor VTOL on engine out unless one wants to fly fast in which case, the multi-rotor VTOL isn't going to do well anyway. If all you're doing is landing when there's a failure, you 'simply' adjust the control scheme to account for the missing propellor. This is very easy with more than 4 rotors although it can be done with 4 as well.
The biggest problem with the multi-rotor VTOL with fixed-pitch generally tends to be its propulsion inefficiency. Longer, slower blades with variable pitch tend to be more efficient, especially when varied thrust is needed. Sure, its easy to vary thrust, simply by increasing RPMs, however that pesky Vsquared drag issue gets in the way as you increase RPMs. With variable pitch as used by conventional helicopters, the RPM can remain constant while thrust can be varied by changing prop pitch (called 'collective' in helicopter jargon).

 

[MontyFloyd]

4 people at 150 a person will barely cover a Pilot's salary for 8 hours

Yeah, too much hype.
The big issue is insurance for this, on top of certification process for Type Certificate.
Those 2 items alone cost hundreds of millions to solve.

Honestly these ideas feel 99% fantasy.
Not that it is technologically possible, its to make it safe and commercially viable.
Cheaper to add auto-pilot to an old Cessna 172 and make a profitable business taxi to outlying airports.

 

[ThomasD]

Just watch out for Birds

 

[Etna]

What ever happened to the Sea Plane company that converted their Planes to all electric Are they transporting passengers with the electric Planes yet?

Not before 2025 at the earliest: Harbour Air’s ePlane takes off on spring tour, despite program delays

This whole plan is just not realistic IMHO. An electric retrofit of an existing aircraft always involve a choice between battery and payload, you can't have both without going clean sheet with significantly (50%+) higher takeoff weight. I am sure they are aware of this, in the mean time blaming certification requirements for the delay sounds less dumb and keeps the PR wheel turning.

 

[doug]

This is an interesting concept:

 

[Etna]

This is an interesting concept:

This concept appears to suffer from very poor efficiency because most of the energy of the towing aircraft is spent in climbing to the cruise altitude rather than actually towing and then when it descends its potential energy is wasted, since the range of the towing aircraft is non contributing.

So you have multiple climbs of tons of batteries donating a small fraction of their capacity to support the continuous flight of just one aircraft. Back of the napkin this looks to me as something that would end up spending an enormous amount of energy and battery life cycles.

In theory this can work but this is likely to end up more expensive and less energy efficient than liquid hydrogen propulsion or carbon neutral synthetic fuel.

 

[daniel]

Yeah, I think @Etna hit the nail on the head.

If all the energy for charging the batteries came from renewables, it could have the advantage over fossil fuels of being zero carbon, but we'd need a flock-ton more renewable energy capacity before that would be economical. If they flew very low there'd be less loss due to lifting all those batteries to altitude, but the passengers would suffer from the turbulence at low elevations. They insist that there'd be plenty of extra capacity in the batteries, but that means added dead weight.

All in all, this sounds like a scam to raise investor money.

 

[JRP3]

E Plane speed record, (345mph), using Yasa motors.

 

[mltv]

excerpt:

• Joby has received a Special Airworthiness Certificate for the first aircraft built at its Pilot Production Line in Marina, CA, allowing flight testing to begin
• The aircraft is expected to become the first ever eVTOL aircraft to be delivered to a customer

Joby Marks Production Launch, Receives Permit to Fly First Aircraft Built on Production Line

SANTA CRUZ, Calif., June 28, 2023--Joby Aviation, Inc. (NYSE:JOBY), a company developing all-electric aircraft for commercial passenger service, today announced it has received a Special Airworthiness Certificate for the first aircraft built at its Pilot Production Line in Marina, California...

finance.yahoo.com

 

[EVer Hopeful]

VTOL?

I would have thought if you were going electric the last thing you'd want is VTOL ... well the last thing would be supersonic I suppose, but you get my point