The Death and Life of Helicopter Commuting [video] | Hacker News Reader

The Death and Life of Helicopter Commuting [video]

youtube.com

58 pointskenneth55 comments

In order to commute to offshore oil rigs via helicopter you need to do a training course to learn how to escape a helicopter should it need to be ditched in the water. A large reason for this is that if its ditched it will likely invert as they are top heavy, which makes escape disorienting.

This is one certification: https://en.wikipedia.org/wiki/Helicopter_Underwater_Escape_T...

I've always wondered if folks commuting by helicopter like this have to undergo any sort of training. Given the nature of non-redundant systems in a helicopter it seems like having an emergency plan is prudent. I've never been on a helicopter except to go to an offshore platform though.

I wonder how common it is or if it's always required. When I used to travel out to oil rigs by helicopter (admittedly a long time ago), I never had any training. But it wouldn't shock if rules were stricter today.

Given how helicopters are used for all sorts of scenic flights, I'd be surprised if it were any sort of universal requirement.

I've done some helicopter pilot training, and the only specific emergency plan I was informed of for passengers is to get out if appropriate, duck, and run forward. (To avoid the tail rotor.)

I think that rule applies for flights at night over water (as it's much less disorientating in light).

I think that's the rule in the Royal Navy anyway.

Tl;Dr - helicopters are noisy and expensive to operate, but hopefully electric 'quad copter' like vehicles won't be.

The caveats being that batteries, air traffic control, and regulations have to change so in short, "I've your 25 today, perhaps your grand children will see a benefit here." :-(. Somehow I think even the hyperloop is nearer term than this technology, and its still out there.

An electric helicopter would be cool, but a single large rotor is more efficient and quieter than four small ones. You could make make a two-rotor VTOL craft like an Osprey. An electric version would be more reliable since you don't have to move fuel and oil around in various dimensions. That would let you get lift from wings during flight, which means longer range than a helicopter with the same battery capacity.

Exactly right. Aviators know that a propeller blade provides thrust/lift but also induces drag. Given a certain power output, the more blades you have, the more drag you have, but you don't get any more lift/thrust. Therefore, if efficiency is what you want you really want as few blades as you can get away with. Normally more blades are a consequence of other design constraints, such as how wide you can realistically build a propeller blade before the stress causes it to disintegrate.

Small multi-rotors have to spin faster to compensate for their reduced efficiency, leading to the characteristic drone sound.

Computer cooling guys know this too... bigger slower fans move more air and do it with less noise.

With electric motors it optimizes differently. Torque is expensive while individual motors are cheap. Distributed propulsion makes a lot more sense.

Let's say you have one 2 MW rotor disk. Rotors are tip speed limited. Let's make it have an angular velocity a. Torque would need to be 2 MW / a.

Having four 0.5 MW disks would have same tip speed but half the span so double the angular velocity and thus each would need torque of only 0.5 MW / (2 x a). Torque dropped to one eighth, and the motor became lighter!

Now, at the one end you have a traditional helicopter with one to a few main rotors, high torque, cyclic and collective pitch in each (because torque is slow to change).

At the other end you have a huge amount of small thrusters that are directly connected to their own motor and thrust is varied by electric means.

In between you have things like intermediate number of thrusters / rotors having maybe a simple gear and/or collective pitch control.

Why is torque expensive in an electric motor? They tend to produce high amounts of torque at lower RPMs than ICEs. Even a Nissan Leaf gets 187 ft-lbs, and a Tesla motor has a flat torque curve to to 10,000 RPM.

I thought that was a generally known thing. A higher speed motor is smaller than a high torque motor for the same power. I don't think electric motors are almost ever connected to speed increase gear. It's almost always reduction or direct drive.

You can check any hobby shop or Alibaba to verify the above.

Probably related to some physics of magnetic field vs current. Would need to dig deeper into that dome day...

Well I don't really know how much torque a helicopter would need. The only number I was able to find was that a 35-foot rotor could spin about 550 RPM. Even with a smaller rotor that would spin somewhat faster, I was guessing that a reasonable gear ratio would give an electric motor plenty of torque at those speeds.

And we are back at square one where the whole point was to go multirotor to avoid the gearbox and cyclic pitch complexity.

In a car, it's a bit similar thing. With a combustion engine it optimizes to a single engine with fixed + variable ratio and shafts to the wheels and things like differentials. Lots of places to have oil, to maintain, to break, being heavy too. Tesla has 1-2 electric motors with a fixed gear ratio of about 10. Some concept vehicles have a direct drive motor near each wheel or even inside the wheel.

The electric motor has different characteristics than a turbine or a piston engine. Hence it can affect the whole machine design.

You wouldn't see a quadcopter on a human-scale craft. The efficiency is too low. The reason they are used in drones is that you can get 3 axis control with only varying motor torque, instead of varying blade pitch/tilt.

Less efficient, but much simpler mechanically.

I beg to differ: https://www.youtube.com/watch?v=OazFiIhwAEs

Well played! (Though I would argue that the parent is still technically correct about multirotors / quadcopters being very inefficient compared to other flight methods)

That said, I am really curious at actual lifetime costs of a system like this, and if it makes up for lack of efficiency by being simpler mechanically (leading to lighter weight, less maintenance costs, etc.) I think thats going to be the big thing that determines if this is a viable commuting option vs. rich person's toy.

Except that there are many examples now of human scale 4, 6, and 8 rotor craft. So perhaps the litmus test is 'efficient enough'. And the article did point out the need for improved batteries.

As energy density in batteries gets closer to kerosene the 'mechanically simpler' aspect of these crafts flips the value equation in their favor.

Relevant: "Why haven't quadcopters been scaled up yet?"[1]

The gist is, scaling up multi-rotor systems isn't as simple as making things bigger - the size adds many issues that the small models don't face (models having nearly impossible performance characteristics compared to full scale versions). Also, there's safety issues regarding controlling such as system when one or more rotors/motors fail.

It's not to say it cannot be done, because obviously it can. It's a question of "why?", when there's clearly better, more simple and efficient ways to get around.

Also, battery power density (and weight) has a long way to go before it will match Kerosene, or even regular AvGas - "Could an electric engine provide the same performance as jet engines on current aircraft?"[2].

[1] https://aviation.stackexchange.com/questions/3300/why-havent...

[2] https://aviation.stackexchange.com/questions/26910/could-an-...

> It's not to say it cannot be done, because obviously it can. It's a question of "why?", when there's clearly better, more simple and efficient ways to get around.

I observe that in spite of the 'simple and efficent' ways to get around there is a tremendous amount of capital being invested to find new transportation modalities. Perhaps one or more of those investments will surprise you.

There are two things that a full-sized electric multi-rotor vehicle must contend with to be practical:

1) Battery power density must have a tremendous breakthrough, in both terms of weight and stored capacity.

2) Electric motors capable of producing the energies required to produce the thrust necessary to propel a full-sized vehicle must also have a tremendous breakthrough in size, weight, and heat dissipation (especially if we're discussing vehicles capable of typical cruise altitudes over long distances).

It would be far more simple and efficient to make a full-sized Kerosene, AvGas, or any other petroleum-based fuel multi-rotor vehicle... but then you must also overcome the unnecessary challenges multi-rotor systems introduce at this scale. Which... leads back to today's average helicopter and airplane designs.

Like I said, it's not impossible... it's just not practical for these reasons. If someone wants to do it, they can... obviously... but it's not the most effective way.

> Perhaps one or more of those investments will surprise you

Indeed, people often invest in some very surprising ideas... sometimes even without really understanding what they are getting into...[1]

[1] https://aviation.stackexchange.com/questions/33541/are-fixed...

And all I'm saying is that you are looking backwards to guess what will happen in front of you. Historically when people have done that, they have been surprised by what came next.

You're absolutely right... but it's important we put faith into feasible ideas instead of chasing down fun, but terribly unproductive and/or unsafe ideas... and also obey the laws of physics.

Differentiating between the two is sometimes difficult, especially when people, generally, want to "believe" in a fantastical vision of tomorrow.

> 2) Electric motors capable of producing the energies required to produce the thrust necessary to propel a full-sized vehicle must also have a tremendous breakthrough in size, weight, and heat dissipation (especially if we're discussing vehicles capable of typical cruise altitudes over long distances).

This one had me wondering, especially since one of the reasons that model quadcopters even exist is because of breakthroughs in brushless motors which have good power to weight ratios for things that fly. So trying to compare a state of the art helicopter engine and a state of the art brushless motor lead me down this path ...

It is notoriously difficult to get details out of Tesla but according to this: https://chargedevs.com/newswire/elon-musk-cooling-not-power-... the Model S electric motor is 362 bhp at a weight of 70 lbs (5.2 HP/lb), and according to this: https://www.geaviation.com/sites/default/files/datasheet-T70... the engine used in the AH-64 Apache is 1662 shp at a weight of 458 lbs (3.62 HP/lb).

The point about cooling is well taken (Elon mentions it as a challenge) however in both model airplanes and quadcopters the motor typically is mount directly under the rotor so that not only does the prop wash provide the lift for the craft, it provides a lot of cooling for the motor driving it.

Again, not saying that you're wrong or that I'm right, I'm just saying that things are changing rapidly, people are investing in that change, and that is a recipe for surprising results.

Just a note on your comparison - aviation engines/motors are not directly comparable to land vehicle engines/motors. They have different expected duty cycles[1][2] and thus, are designed quite differently.

I believe the engines in an Apache are jet turbines, which may also not be directly comparable, but that's only a guess. They are also "war machines", and likely are built to tolerate abuses Tesla cannot imagine and do not design for (my assumption here is that is what adds quite a bit of weight to the Apache engines).

All this is to say the obvious, one could not simply take a Tesla electric motor and install it in an aircraft, expecting good things.

Things may eventually change, and ultimately you may be right - I just don't want to put that much faith, yet, into this idea.

[1] https://aviation.stackexchange.com/questions/11527/what-are-...

[2] https://aviation.stackexchange.com/a/34361/2294

The motors are there. Batteries not. A vehicle carrying multiple persons would have a gas turbine and a high speed generator. The electricity would be used to run distributed direct drive thrusters. The key here is to bypass the complex, heavy, expensive, maintenance intensive and unreliable gearbox. Also no shafts are needed. Power can be varied instantly.

> Also no shafts are needed. Power can be varied instantly

You need to be able to decouple from the motor/engine for safety. Gearboxes provide this ability. One cannot autorotate if a motor has seized and locked the rotor in position, or has been damaged and pegs to full RPM. Also gearboxes can vary torque and RPM without having to adjust the engine/motor RPM/Power.

Also, varying power instantly isn't necessarily a desirable trait in a full-scale aircraft. You have rotors/propellers traveling close to, or exceeding the speed of sound. Instant acceleration would put a lot of forces never before seen on these components.

Usually in aircraft, the RPM of the rotor/propeller remains fairly constant, or within a small bounds. Typically you increase power to the engine/motor, and the gearbox keeps the rotor/propeller RPM's constant.

> unreliable gearbox

They're a lot more reliable than you seem willing to give credit for. Even in your run-of-the-mill car, the gearbox usually fails well after many other major components, especially with regular maintenance (where it may never fail over the lifetime of the vehicle). Aircraft are subject to very stringent maintenance and inspection schedules.

> The motors are there

Seems they aren't quite.[1]

[1] https://aviation.stackexchange.com/questions/26910/could-an-...

If you have fixed pitch, you can't really autorotate anyway. Safety would be provided by redundancy.

With collective pitch, it becomes interesting. Does the motor help or hinder autorotation?

In a hybrid system, you anyway decouple the propeller and turbine with the electric system.

Your car gearbox operates at much lower speeds (because it's not attached to a turbine) and has a lot less weight constraints. Helicopter powertrains require a lot of maintenance.

The stack exchange link talks about jetliners while we're talking about copters.

> If you have fixed pitch, you can't really autorotate anyway

Helicopters are not fixed pitch... your run-of-the-mill hobby multi-rotor is, but that's due to the reasons mentioned above in my previous posts (eg. simplicity at this small scale).

> Safety would be provided by redundancy

Unless you suffer a total electric failure. Or even just a failure on one side of the aircraft (or even just one motor, in a quad setup). Being able to mechanically work these systems is fairly important, since it's less likely both mechanical and electrical systems fail simultaneously.

> In a hybrid system, you anyway decouple the propeller and turbine with the electric system

Unless your electric system is the failure.

> Your car gearbox operates at much lower speeds (because it's not attached to a turbine)

Even some model multi-rotors use gearboxes. You have a motor, spinning either slower or faster than the desired RPM for the rotors... a gearbox solves that difference, and provides a mechanical means of fully decoupling from the motor should the need arise.

> Helicopter powertrains require a lot of maintenance

This is true, but this is not really an issue... and nobody really is looking to "solve" this non-problem. Aircraft require a lot of maintenance and inspections.

It's hard to see how to overcome the rotor inertia issue in larger craft. So I'd expect human-sized quads would just use collective pitch control. Here's a hobby quad that has taken this approach: https://hobbyking.com/en_us/assault-reaper-500-collective-pi...

A lot of the noise of helicopters comes from the rotor, and there is little more that can be done about it. Electric rotorcraft are not likely to be as quiet as their promoters like to suggest (e.g. through animations with unrealistic sound tracks), regardless of the number of rotors.

A significant part of the noise comes from the antitorque (tail) rotor, which is much smaller and typically turning ~3x as fast as the main rotor. There are several solutions to minimizing this noise, including ducted tail rotors and NOTAR https://en.wikipedia.org/wiki/NOTAR

Can we substitute batteries for fuel cells? They seem near-useless for cars, but very promising for aircraft.

They are not "useless" for cars, just currently impractical. The problems are the catalyst requires rare, precious metals and, even using hydrogen, efficient fuel storage.

Correct me if I am wrong, but AFIAK the efficient fuel storage issue has been solved with using Methanol/Ethanol (liquid at room temperature) instead of Hydrogen as a fuel.

Just a curiosity, in Brazil some executives are using ambulances for commuting[0].

[0] https://www.metrojornal.com.br/foco/2017/08/29/empresa-aluga... (article in portuguese)

Orson Welles also famously used an ambulance to get around to various radio shoes in NYC: https://en.wikipedia.org/wiki/Talk%3AOrson_Welles

  Due to his busy radio schedule,
  he was hard pressed to find ways
  to get from job to job in busy New
  York City traffic. In an interview
  conducted in his later years,
  Welles tells how he "discovered
  that there was no law in New York 
  that you had to be sick to travel 
  in an ambulance." Therefore, he
  took to hiring ambulances to take 
  him, sirens blazing, through the
  crowded streets to get to various
  buildings.

There's a lady in South Carolina who's on medicaid that did that to the tune of costing the medicaid office about $400,000. I'll have to see if I can find the article.

EDIT: Found it http://www.live5news.com/story/22075845/live-5-news-investig...

Shameful to see the officials congratulate themselves on busting the lady after she copped a free ambulance ride 100 times.

Seems like she was merely hacking a horribly inefficient system.

Can't argue that. Can you imagine the liability from the ambulance staff if they just didn't pick her up though?

Yup, age old "that's not my job" strikes again.

Wrong: the shame is on the woman who knowingly abused the system and took money away from sick people. Just because you can hack a system doesn't mean that you should.

What portion of the blame does the poor woman bear? What is the just punishment?

What about people who visit emergency rooms, for non-medical emergencies?

Okay, but why does an ambulance ride in America cost $4,000 a pop? An Uber travelling the same distance would cost $4, maybe $40.

This is health care costs being out of control right there.

That's illegal though. It has only survived so far due to lack of enforcement.

That's bound to change pretty quickly after the press got involved.

São Paulo has the biggest helicopter transport fleet in the world, so that's not necessary. Just a case of someone trying to cheat the system, paying less for something illegal.

Executives and doctors are some of the common users of helicopters around here.

Apparently this is (or was in 2013) a thing in Russia as well: https://jalopnik.com/ultra-rich-russians-hire-fake-ambulance...

Stephen Fry reputedly uses a black cab in London for similar reasons (black taxis in London can use lanes reserved for buses that are less congested).

I suspect that a black cab ceases to be a "black taxi" when it is no longer operated by a licensed black cab driver.

https://tfl.gov.uk/modes/driving/red-routes/rules-of-red-rou... specifically says "Licensed London Taxis" which I'm guessing Mr Fry isn't driving.

I suspect that the police/traffic cameras can't tell or don't check and that is how he is (or used to) get away with it.

They could just extend the NJ PATH by 3 miles and make it a $3 ride to the airport.

The distance to any of the 3 major airports from Manhattan is quite short. The idea that we need helicopters to make good time is crazy. It doesn't scale.

Fair point, though as a study in potential, promise, players, and failure modes, this is a fascinating story.

I live in Manhattan and it's an absolute joke that there isn't good mass transit to any of the three major airports in the area (Newark, JFK, and La Guardia). There are various air trams and buses and such, but none that are directly part of the mass transit system. Considering that NYC has the best mass transit in the country, you'd think it could take you to the airports, but nope! The best ways to get to the three are subway to regional rail for Newark, subway to air tram for JFK, and subway to bus for La Guardia (which has guaranteed terrible traffic pretty much always).

Contrast with Washington National Airport, which has a Metro station right at the airport.

Airports normally aren't the most valuable nodes to connect in a mass transit system, compared to other projects that could be accomplished with a similar amount of space and money. Alon Levy wrote a fairly detailed argument to that effect here: https://pedestrianobservations.com/2014/05/28/airport-connec...

According to the article:

"The mode of transportation that best suits the needs of international airports is then mainline rail."

Exactly, and mainline rail is not normally what people are referring to when they complain that the airports aren't connected to NYC's mass transit system.

There are 472 stops in the MTA subway system alone. Theoretical JFK and La Guardia stops would get more daily riders than the majority of the existing ones.

Airport connections tend to serve higher value riders too, so you make back more in total economic value to the city from airport riders than from riders at some random stop. This study is treating all riders as equal.

Reply on news.ycombinator.com