Future Helicopters

[relyon]

Along with several other innovative [and some long overdue] vertical flight developments, the Sikorsky X2 TECHNOLOGY™ demonstrator is going to be flying not all too long from now. It got me thinking as to what future helicopters may be like. Here are things I envision coming down the line, some sooner and some later:

• Advanced composite primary and secondary structures.
  

• Counterrotating rigid rotors.
  

• Counterrotating propulsion units (propellors or fans).
  

• Inductively coupled active material control surfaces.
  

• Brushless electric motors for power.
  

• Hydrogen fuel cells for power generation.
  

• Advanced storage cells for peak power requirements.
  

What do you think may be coming?

 

Bob

[Future206Pilot]

I think that the Helicopter Industry is going to be the last to convert to alternative fuels and Hydrogen. A normal helo fire is hot enough without throwing in a hydrogen tank

[relyon]

I think that the Helicopter Industry is going to be the last to convert to alternative fuels and Hydrogen. A normal helo fire is hot enough without throwing in a hydrogen tank

Public ignorance and misguided perception seems to follow the use of hydrogen as an energy source. Most public viewpoints are drawn from the Hindenburg disaster which also suffers from the same ignorance and perception while being simultaneously used as the defining evidence as to why hydrogen is bad. A few things worth pointing out:

• Fuel cells don't involve combustion and produce relatively little heat.
  

• Energy from the little heat that is produced can be further recovered to a degree by thermoelectric processes.
  

• Hydrogen has the highest energy per unit mass of any fuel and that energy can recovered more efficiently than any other fuel as well.
  

• Hydrogen gas rises rapidly when released in the air; liquid (and many gaseous) hydrocarbons fall to the surface and on water they float.
  

• A source of ignition is necessary in all cases if a fire is to follow a fuel system breach. That is less likely to occur if combustion is not present to begin with.
  

Fortunately, there are far greater hurdles to the use of hydrogen as an energy source than it's potential flammability or public perception. As far as conversion to alternate fuels and hydrogen goes, the helicopter industry will do so mainly in response to economic and/or regulatory factors. Due to their fundamental design as well as how and where they are used, helicopters may be prime candidates for such fuels in aircraft.

 

A couple links for those interested are http://www.hyweb.de/index-e.html and http://automobiles.honda.com/fcx-clarity/.

 

Bob

[Eric Hunt]

How about a comfortable seats for everybody with good lumbar support, ergonomic layout of controls, and an air conditioner like the kit in my little $10,000 Hyundai - the $30,000 kit in the S76 is barely capable of reducing the sweat and certainly can't make me want to turn it off in summer because it is too cold.

 

How about air bags all around the cockpit and cabin?

 

How about a rear-view camera? Or even a cabin camera? Only a $700 option in a car, probably a $7000+ option with an aeronautical part number.

 

How about remote key locking? Drives me mad to have to lock every door and the luggage locker with a key, which is so easily lost or broken in the lock. And maybe a key setup for starting the thing - usually all you need is the checklist.

 

How about a disabling device for when it is parked? Stop the potential terrorists stealing it.

 

How about IR head-up display? Even the cost of a Mercedes kit would be cheap compared to the aircraft cost or a FLIR.

Edited March 11, 2008 by Eric Hunt

[SquirrelFlight]

• Fuel cells don't involve combustion and produce relatively little heat.
  

• Hydrogen has the highest energy per unit mass of any fuel and that energy can recovered more efficiently than any other fuel as well.

 

Unfortunately, fuel cells are heavy and make use of expensive and rare componenents (eg platinum) for anode and cathode.

 

Hydrogen may have the highest energy per mass, but it also has very low density, meaning large volume (you'll notice that the container the space shuttle uses to store fuel for about a half hour of sustained use, with some left over for orbital maneuvering is much bigger than the shuttle itself). How big a tank will you use to get at the energy? Will your aircraft be able to lift it?

 

Also, hydrogen is very, very small and has a tendency to diffuse itself through other materials, meaning that your normal pressure vessel isn't really going to be good enough (you'll again notice that the shuttle fuels up right before launch). There are other techniques (mettalic hydride bonding) that could work, but they are not well researched yet and will, again, add weight.

 

Don't get me wrong, I'm a fan of hydrogen power research, and I think most of these problems will be solved, making it useful for ground transport where weight isn't an issue, but aircraft are, by nature, weight limited. If the weight problem for all components can't be solved it'll never work for aircraft.

[relyon]

Eric Hunt - Such a great list and one I largely agree with!

 

Sometimes I'm all but convinced there must be a "Human Factors Division, Ergonomics Team, Uncomfortability Specialist" title somewhere in helicopter manufacturer personnel hierarchies. Their motto? "We're Not Comfortable until You're Not Comfortable."

 

Cameras and HUDs can be integrated, both physical positioning as well as spectra observed. The whole issue of security access and remote control can be dealt with fairly simple hardware and some slick software. Imagine being able to control everything mentioned down to the access item, person, and time of day. Intrusion attempts can be noted as well, preferably in conjunction with the camera(s).

 

I'd be a tad reluctant to have air bags in the cockpit though. A bird strike or hard landing could seriously ruin one's day. Passenger cabin? I want a crew-only in-flight accessible "test" mode. "Calm down back there ... Don't make me press this!"

 

You're entirely correct about the overall cost. I wonder how many GA aircraft are being navigated with handheld GPS, not necessarily of aviation lineage, due to the cost of the alternatives.

 

Bob

Edited March 11, 2008 by relyon

[relyon]

SquirrelFlight - Thanks for replying. I realize this is more of an engineering-oriented topic than most but it is about helicopters. I thought I'd take time to address each of the points made but in no way am I saying they're incorrect. Quite the contrary. These are exactly the sort of things that need to be sucessfully addressed if hydrogen is ever to "fly".

 

Cost: Many aircraft components are made of rare and expensive materials employing equally rare and expensive methods to produce. I doubt that will change but do think the longevity of an electric fuel cell powered drivetrain would increase over what it would replace, at least partially mitigating any increased cost.

 

Weight: Think of the whole system a technology is designed to replace. Hydrogen fueled electric power in aircraft would replace fossil fueled piston/turbine power. That includes fuel storage and distribution as well as power generation and distribution. That's a significant amount of the MGTOW.

 

Volume: It is true that hydrogen has a low bulk density both as a liquid and as a gas. It's bulk energy density isn't too bad and coupled with the ability to get at that energy it's often a superior fuel. Most don't realize that, gallon for gallon of liquid, hydrogen can provide nearly three times the fuel economy of gasoline in current production automobile engines.

 

Diffusion: It is also true hydrogen diffuses through many apparently "solid" materials, significantly more in gaseous form than liquid. Supercritical long-term oxygen and hydrogen storage tanks have been in use since the Gemini the days. There was significantly more of an issue with not using it fast enough due to total pressure concerns than there was with diffusive process loss. A major consideration is that it's use in vehicles is for a motive energy source, not storage.

 

Space Shuttle: Such comparisions are all but completely irrelavent. The Space Shuttle is designed to go from the earth's surface to orbit and zero to orbital velocity in a very short amount of time. From an energy perspective alone it's radically different than most other forms of transportation. The main tanks are filled very shortly before liftoff primarily to due material cold soak considerations, tank ice formation, inability to keep supercritical pressures, and the lack of sufficient cryogenic facilities at the Cape to keep them topped off. The main tank volume also includes liquid oxygen - totally unnecessary for non-rocket atmospheric use - and a significant amount of empty volume as well. One point that is notable is that the Space Shuttle doesn't use metal hydrides for hydrogen storage. I consider that significant given it's overall use of leading-edge technologies.

 

You're absolutely right that the weight issue for all components must be solved or it'll never work for aircraft. That is one of the primary thoughts I had in mind when I wrote that there are far greater hurdles to the use of hydrogen as an energy source than it's potential flammability or public perception. I do feel the problems can and will be solved; if not, we're all going to be walking unemployed when fossil fuels are finally depleted.

 

Bob

Edited March 11, 2008 by relyon

[Future206Pilot]

Ok relyon I'm sorry if i came across as ignorant... I guess I'll add something intelligent to the conversation. The only times where I could see fires happening with Hydrogen, would be during refueling or if you were to get in a crash severe enough to breach the tank, the helicopter would be torn to pieces. The tanks are crash-rated for the application but if it were to be completely impervious to a breach, the tank would be really heavy. Yes, I do have a general knowledge of how a hydrogen fuel cell works.

 

Regarding electric helicopters... The batteries required to power the helicopter under load would be way too heavy counter the benefits of using electricity. Another problem is with the electric motors, the torque of them would increase wear and could increase the chance of a sudden catastrophic failure.

[FLHooker]

As the Sikorsky X2 technology goes, it's not new, the Army did back in the day, and I honestly couldn't tell you the name of the bird or why it never made it... I just know that it was there. I could probably research it.

 

What does everyone think about the tilt rotors? I could see that getting bigger in the future, especially on shorter hops that the fixed wing, regionals do now. I was on a flight with ETE of 26 minutes from Harrisburg, PA to Philly... Took us that damn long to taxi out to the runway, take off, well you get the picture... Instead of just coming to a hover and going for broke.

 

For example http://www.bellagusta.com/air_ba_main.cfm

 

 

CHAD

[relyon]

Ok relyon I'm sorry if i came across as ignorant... I guess I'll add something intelligent to the conversation. ...

I apologize if I came across as implying you or anyone participating in this forum was ignorant. I didn't intend that in any way and encourage all to discuss vertical flight's future whatever their background. I have a number of informed thoughts on the subject as you can see, but I'm open to them being questioned and challenged. That way we can all learn, myself included.

 

My point regarding fuel flammability is that, combustion temperature notwithstanding, I'd opt to be in a hydrogen-based fuel fire than any hydrocarbon-based fuel fire if I have to be in one at all. I wouldn't even try to design a tank impervious to breaches - you're correct that would be way too heavy. Instead, design a tank that selectively breaches and vents the fuel in as safe a manner as possible. Similar to crumple zones in automobiles. Even now, any crash that can breach a fuel tank is going to be pretty bad and fire of any sort is just going to make it worse.

 

Regarding electric helicopters... The batteries required to power the helicopter under load would be way too heavy counter the benefits of using electricity. Another problem is with the electric motors, the torque of them would increase wear and could increase the chance of a sudden catastrophic failure.

I'm actually quite surprised at the usable energy density of current lithium-based batteries. Electric R/C helicopters have made amazing strides in the past several years compared to their nitromethane/methanol powered bretheren with the advent of high[er] power brushless motors and lithium polymer batteries. While certainly just models, their power to weight ratios are very similar to full size. Models are where many aviation pioneers started, notably Arthur Young among them.

 

Electric storage (via batteries or so-called ultracapacitors) should only be used to supply peak power loads. Normal power demands need to be entirely supplied by a fuel cell energy source. What storage devices don't have even at this point is high overall energy capacity - that's where fuel and fuel cells come in.

 

Electric motor startup torque problems have been solved for some time. The electric power controller simply needs to increase the power/torque output at a rate that doesn't overstress any mechanical components while the inertial loads are high. Once those loads diminish full operational power/torque can be applied. A huge advantage of the coaxial layout is that none of those loads need be transmitted to the overall airframe, the stationary electric motor core being part of the mast structure. Think of fairly large main rotor hub cowlings (ala BH-407, et al); the larger they are the less torque there need be, within reason.

 

There are many very real engineering hurdles to cross before a viable full-sized electric helicopter can be available, not the least of which is the fuel supply - particularly if it is hydrogen. Pilot and/or public concerns, while quite valid and notwithstanding, are lesser problems at this point. As can be seen by my starting and replying to this topic, I'm very excited by the prospects.

 

Bob

Edited March 12, 2008 by relyon

[relyon]

As the Sikorsky X2 technology goes, it's not new, the Army did back in the day, and I honestly couldn't tell you the name of the bird or why it never made it... I just know that it was there. I could probably research it.

Very true - it's not. I believe you're thinking of the NASA/DOD XH-59A Advancing Blade Concept (ABC), also known as the Sikorsky S-69. The only practical difference I see is that the X2 uses a fan for propulsion whereas the XH-59A used jets. I'm sure someone at Sikorsky could add to that, but it's the only thing I see different aside from perhaps size. The X2 is one of the reasons I think some of these developments a long overdue.

 

What does everyone think about the tilt rotors? I could see that getting bigger in the future, especially on shorter hops that the fixed wing, regionals do now. I was on a flight with ETE of 26 minutes from Harrisburg, PA to Philly... Took us that damn long to taxi out to the runway, take off, well you get the picture... Instead of just coming to a hover and going for broke.

I've been a big fan of tiltrotors since I first became aware of the concept. Beginning with the Bell XV-3 and then the Bell XV-15, they've now come to the Bell Boeing V-22 Osprey and the Bell Agusta BA-609. Another good idea very long in coming to fruition. I do think they have their niche but it isn't what most think it is. Tiltrotors are airplanes that can hover for takeoff and landing, not helicopters that can go fast. I think the XV-15 and BA-609 are about the right footprint. The Osprey, like the Space Shuttle, is a series of compromises. Still, I hope it suceeds. The proposed four proprotor transport is the wrong solution for the problem.

 

Before anyone points out the Osprey's crash history and related personnel deaths, I suggest they study the history of helicopter development, notably that of the BV-107/CH-46 among others. While definitely not a high point in vertical flight history, people seem to have had a bigger stomach for aircraft development problems back then.

 

Bob

[SquirrelFlight]

If you're interested in the use battery/fuel cell electric technology in aircraft, it's probably best to watch for development in light fixed-wings. That's where power required is at a minimum, along with more allowance for higher weight.

 

There have been a couple of attempts. I seem to recall one group what was going to build a Lancair (I think) and study electrics in three stages: 1) replace the ICE with an electric motor and a small battery just to show they can produce power needed 2) replace fuel bladders with batteries (lithium-type for wieght reasons) for longer range proof of concept and then 3) see if they can't fit a fuel cell to it for even longer range.

 

Unfortunately, I've lost track of that group (I don't even recall what they called themselves), and haven't found them again.... although a quick Google search found this: http://www.airventure.org/2007/4wed25/sonex.html which looks a little bit promising, anyway.

 

Also, WRT fuel cells - it has been a while since I've looked seriously into them, but there are several types of fuel cells, including ones that don't necessarily need to start with hydrogen - I'll see if I can find a good reference... in fact, if I remember correctly, it might fit in well with the discussion of biofuels that was going a few weeks back (that was here, wasn't it?)

 

EDIT: Here's anothe interesting article I found on electric airplanes: http://www.greencarcongress.com/2008/01/conventional-li.html

Edited March 12, 2008 by SquirrelFlight

[relyon]

If you're interested in the use battery/fuel cell electric technology in aircraft, it's probably best to watch for development in light fixed-wings. That's where power required is at a minimum, along with more allowance for higher weight.

Similar to what's already happened in the modeling world, I anticipate full-sized fixed wing aircraft being the first practical electric aircraft. NASA thought so too, as the could be seen with Helios project. I hope it or a derivative will be revived but question when. One of the reasons I consider helicopters a reasonable place to start is that the duration and range requirements are less than most commercial airplanes plus helicopters are pretty neat anyway. I've got to admit though, the electric Sonex is very cool. I'd love to see an electric R-22 or Schweizer 300 just to prove it can be done to those that say it can't.

 

Also, WRT fuel cells - it has been a while since I've looked seriously into them, but there are several types of fuel cells, including ones that don't necessarily need to start with hydrogen - I'll see if I can find a good reference... in fact, if I remember correctly, it might fit in well with the discussion of biofuels that was going a few weeks back (that was here, wasn't it?)

I do consider fuel cells to be an all but a fundamental requirement of full-sized electric aircraft. While electrical energy storage technology (usually batteries) has made considerable leaps, it's still too heavy and most likely will be for some time to come. The reasons I'm such a proponent of hydrogen-based fuel cells have to do with it's energy content and availability, the wide variety of processes to generate it, and the zero emission qualities of using it. The fact that we continue ever-closer to exhausting our limited supply of oil and natural gas, biofuels notwithstanding, enters into the equation too.

 

Bob

[SquirrelFlight]

I found a series of articles in Kitplanes magazine you might be interested in:

 

Part 1

Part 2

Part 3

[FLHooker]

Bob,

 

Here is a picture of what I was talking about. This is sitting outside the museum at Ft Rucker, AL. The AH-56 Cheyenne, it has a tailrotor and a rotor used for propulsion. It was developed back in Vietnam.

 

Article: http://tri.army.mil/LC/CS/csa/aahist3.htm#AH56

 

 

CHAD

Edited March 16, 2008 by FLHooker

[goromadgo]

Bob,

 

Here is a picture of what I was talking about. This is sitting outside the museum at Ft Rucker, AL. The AH-56 Cheyenne, it has a tailrotor and a rotor used for propulsion. It was developed back in Vietnam.

 

Article: http://tri.army.mil/LC/CS/csa/aahist3.htm#AH56

 

 

CHAD

 

We have one of those sitting outside my building on the flight line back at Fort Polk. Every day on the way to work I can't help but think "That is one UGLY helo!" But then again it is sitting between a Huey and a Cobra...things of beauty!

[Future206Pilot]

I saw something that was kinda chilling last night on "Future Weapons". It was the ULB UAV AH-6J, it was able to pick-up, hover, fly a course, come back to a hover, and land without any human intervention during flight...

 

The "Little Bird" was then paired up as a scout for the AH-64D, and used to clear targets dangerous to the AH-64 prior to its arrival.

 

I'm sure its been mentioned before

 

The AH-6J ULB UAV

[Darkhorse]

Sikorsky used to have a page on this with a much better picture and stats, it makes me drool. The fuselage is bigger than a C130.

 

[SquirrelFlight]

Looks like Boeing has been doing a lot of work on hydrogen fuel cells. An article from AvWeb discussing the fuel-cell powered motorglider they've flown successfully:

 

http://www.avweb.com/eletter/archives/avfl...ull.html#197531

[relyon]

Future206Pilot: UAV's will become more proliferant in all areas, particulary that for which the OH-6 was originally used for in Vietnam: ground reconnaisance and drawing fire. It's good to see how an existing machine can be put to use, but there's a whole lot about the basic OH-6 design that a true UAV has no use for. Design elements that are just for humans are completely unnecessary in an Unmanned Aerial Vehicle by definition.

 

Darkhorse: IIRC, that model represents Sikorsky's entrance in the FTR/HLR/HLVTOL/JHL competitions. While I agree it's an interesting design as are all the entrants I continue to question need, even for military uses. The downwash from such a beast would literally be a small hurricane. Those interested should see http://www.globalsecurity.org/military/sys...ircraft/jhl.htm for more.

 

SquirrelFlight: I came across the Boeing fuel cell powered airplane story too and was going to post it but you beat me to it. Another one I came across is this: HyFish takes to the sky in Germany. Sure, it's an airplane and an R/C airplane at that, but this little zipper tops out around 200km/hr on electric propulsion powered by a hydrogen/oxygen fuel cell. A very interesting application of various technologies.

 

Bob