If you could design your own rotorcraft...

[Whimlew]

If you could design your own rotorcraft...

-- How many blades would it have?
-- What would its maximum range be?
-- What would be its maximum speed?
-- What engine would it have?
-- What type of tail rotor would it have?
-- What color would it be?

Further considerations:

Payload
Critical hover or vertical climb condition
Maximum maneuver load factor
Maximum disc loading
Maximum physical size
Maximum noise level
Minimum one-engine-out performance
Minimum autorotative landing capability

[roscoe1]

Scaled down Sky Crane. Removable passenger/cargo pod (in minutes), no extra crap that pilots don't need. Super reliable engines and built like a tank, only better. Just a bit bigger than the KA-26. Co-axial rotors.

[Lama Bear]

Solar powered. It could only fly on bright sunny days with enough range to fly from bar to bar.

[krypton_john]

5.
260nm.
135kt.
RR250C20
2 Bladed
Black.

Oh, it was already designed... in 1963!

[Aluminium Mallard]

As above except with a slightly bigger rear cabin for pax and blades that a pilot can fold it so you can get more that two in a hanger that can fit 10 jetties.

[riff_raff]

I'd prefer something close to the AW609, but with a fully autonomous flight control system. And maybe engines a bit more current than PT6's.

[noflynomore]

Krypton John's H500(E) would be right up there on my list though I might go for a Notar for the safety and less concern about the back end. Disadvantages are absence of luggage space and horrible back seats. Gazelle ticks all boxes & would be hard to beat with a quieter engine - fast, spacious, low slung for easy access, still one of the best looking helos out there, fenestron for safety and above all a clutched rotor for loading/unloading disengaged with engine running, a very big advantage.
If I needed family transport then a 206L3 on low skids would be ideal.

Riff raff, "fully autonomous control system". You want a pilotless self-flying helicopter? Where's the fun in that, except it'll take you home pissed at night!

[cattletruck]

It's already been built - it's called the Fairey Rotordyne - lots of room, big payload, and lets everyone know you're coming.

Colour - gun metal grey.

[Hughes500]

A tail rotored MD 600 would fit my needs nicely, especially if you could buy a second hand one at the same price has a Notar one ( 1200hrs TT for $ 700 !! )

[ShyTorque]

It's already been built - it's called the Fairey Rotordyne - lots of room, big payload, and lets everyone know you're coming.

Colour - gun metal grey.
Yes, a great opportunity missed*, an amazing aircraft far in advance of its time (*or rather, thrown away).

But only one 'R' in the name Rotodyne.

[MOSTAFA]

Rotodyne!!!

Did it actually have anything going for it? Wasn't it finally scuppered by the Andover and the fact Westland's took it over and everybody cancelled their orders, including the MOD. Nostalgic maybe but thats about it!

Surely the opener of this thread missed the most important question off his spec list - what do you want to do with it!

[John R81]

As a private / simple charter ship, the EC120 with EC130 engine, gearbox, rotors and tail. Best cabin of any light helicopter, but would benefit from more oomph!

[PDR1]

Yes, a great opportunity missed*, an amazing aircraft far in advance of its time (*or rather, thrown away).


Yes, a missed opportunity to combat discrimination by rendering the entire population of the known universe completely deaf.

It was a flawed concept that was continued long after its fundamental faults were known to be insurmountable - something that epitomises what was wrong with the UK aircraft industry at the time (cf TSR2, princess flying boats etc etc).

PDR

[ShyTorque]

PDR,

I did say that the Rotodyne was far ahead of its time. Don't forget that the aircraft was designed and flying almost sixty years ago!

It is generally agreed that the rotor tip jets were very noisy, but in truth were only lit for takeoff and landing. Modern technology could no doubt considerably reduce their noise footprint, as it has with other aircraft engines, bearing in mind that the similarly noisy turbojet engines of that time would not pass muster today, by a very long way. Same with the noise of the thrust engines and their propellors.

The Rotodyne had an incredible payload/APS weight ratio compared to any helicopter, even by today's standards, because it lacked a main rotor transmission system and had no tail rotor. It could also fly at speeds that would still be seen as highly respectable today.

[PDR1]

It is generally agreed that the rotor tip jets were very noisy, but in truth were only lit for takeoff and landing.


...which is (of course) the point in the mission profile where noise is of the biggest concern.


Modern technology could no doubt considerably reduce their noise footprint, as it has with other aircraft engines,


I seriously doubt it. If they remained as ramjets they would remain noisy. The onlt real alternative would be to replace them with turbojets or even turbofans, but there's a long list of reasons why that would be a bad idea (even if you overlooked the cost aspect).


bearing in mind that the similarly noisy turbojet engines of that time would not pass muster today, by a very long way. Same with the noise of the thrust engines and their propellors.


That rather proves the point - turbojets never could be adequately muffled, and so have become a "dead" technology for most civil aviation purposes.


The Rotodyne had an incredible payload/APS weight ratio compared to any helicopter, even by today's standards, because it lacked a main rotor transmission system and had no tail rotor. It could also fly at speeds that would still be seen as highly respectable today.

It's essentially a compound helicopter. We could do much the same today by extracting power from the "thrust" engines to drive the rotor. The weight of the gearbox would be offset by losing the instrinsic and consequent (structure) weight of four turbofans at the rotor tips. The rotor torque coul;d effectively be opposed using differential thrust on the propulsion engines (the same mechanism as used by the rotodyne for yaw control at rotor-borne speeds).

The tip-jet noise issue was identified very early on in the rotodyne programme, but was never the focus of any significant effort while they pressed on with the design. It should have been identified as the potential show-stopper that it was and the remainder of the project put on hold while they tried to find a cure or an alternative. But they didn't, they just birned through money in the vague hope that they'd be able to bluff it out.

It's the same as the TSR2 project where the whole weapn concept depended on an extremely complex integrated sensor/navigation/weapon system of a kind never previously seen. Without it the aeroplane was just airshow-fodder for plane-spotters. So the project SHOULD have focused on de-risking the integrated avionics concept to show it to be achievable (which with the available technology it ultimately wasn't, of course) before continuing with the simple bit (the airframe).

The british aircraft industry has always been rubbish at identifying the key issues and focusing on fixing them in any systematic manner. If the British Aircraft Industry had been Mark Watney they'd have been focussing all their efforts on lightening the second MAV only to die long before they reached it hbecause no one focussed on how toi avoid starving for the next 3 years...

PDR

[SASless]

It would not have a Bell Helicopter Pilot Seat I can promise you that!

[ShyTorque]

PDR, You had best get your pencil sharpened and drawing board out. Can you provide details of any helicopter of that era with a payload well over its own empty weight? The obvious answer is the early CH-47, but it wasn't anywhere near as good as the Rotodyne.

Anyhow, I'd still want to fly the latter; although I have flown the former in the guise of the Chinook HC-1.

[cattletruck]

I've always thought that with the Fairey Rotodyne concept it could have further been developed to allow the gases from the turboprop engines, with some half decent plumbing, to be squirted out the tips of the rotor blades much like that of a water sprinkler.

[yellowbird135]

That's easy.....subcontract crewseat design to Recaro.

[500 Fan]

MDHC flew a 520N with a six-blade rotorhead back in the early 1990's. That might have been a nice machine to fly. At the moment, a lightly-loaded MH-6M MELB is probably as good as it gets.


500 Fan.

[SASless]

The Mad Dawg's are a hoot aren't they!



MDHC flew a 520N with a six-blade rotorhead back in the early 1990's. That might have been a nice machine to fly. At the moment, a lightly-loaded MH-6M MELB is probably as good as it gets.


500 Fan.

[ShyTorque]

I've always thought that with the Fairey Rotodyne concept it could have further been developed to allow the gases from the turboprop engines, with some half decent plumbing, to be squirted out the tips of the rotor blades much like that of a water sprinkler.
CT,

It's already been done and more research is being done on similar systems.

[R22 HEAVY]

Two engines, two blades up top and on the tail, chaff and flare, retractable gun pods on sponsons. Retractable undercarriage, colour black on top white underneath.

[Kewbick]

If I could design my own rotor-craft, it might look like this:

http://i1047.photobucket.com/albums/b477/gumpjr_bucket/AVX509.jpg

[cattletruck]

Actually, I've always thought you could turn the tail rotor of any run-of-the-mill helicopter into a pusher-prop that can reverse pitch its blades on one side during the hover to counteract the torque. That is, it can induce a turning moment around the tail rotor gearbox which can be balanced with cyclic.

[PDR1]

The mechanical advantage (leverage) of such a system is minimal, so the stresses in the blade roots and shaft would be huge.

PDR

[IFMU]

Years ago I believe Sikorsky had a pivoting tail rotor which swiveled to provide thrust in forward flight, using the vertical tail for anti torque at high speed. The experiment must not have warranted pursuing the technology, as the concept has disappeared. I believe there were a lot of vibe issues. If I was to design my own rotorcraft it would look a lot like the X2.

[SASless]

I would like to see this all dolled up into a nice Corporate style paint scheme and interior.



https://s-media-cache-ak0.pinimg.com/736x/d9/17/91/d917918cb8012530599992f1b0bd4e77.jpg

[Cpt_Pugwash]

A highly developed Gazelle... :)



http://upload.wikimedia.org/wikipedia/en/thumb/4/4d/Oblivion_BubbleShip.jpg/500px-Oblivion_BubbleShip.jpg

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjr3IPzp5jSAhWnDMAKHQRoB88QjRwIBw&url=http%3A%2F%2Ffpvlab.com%2Fforums%2Farchive%2Findex.php%2 Ft-8293-p-4.html&psig=AFQjCNFU9-nM3lTkaWBZ4ZBxIy3fuyB_ug&ust=1487461276610225

[JohnDixson]

Cattletruck: Here you are:

http://www.sikorskyarchives.com/images/image%20s-66%20AAFS/S-66%20X%205.jpg

[SASless]

I did not know the SK Engineering Department used mind altering substances to that degree!:uhoh:

[JohnDixson]

Right, SAS! Someone cut off their supply as you'll notice we did not pursue this approach.

Noticed also that so far, no poster has mentioned a desire for a rotor that the pilot stops in flight, after which it behaves like a four bladed X-Wing which utilizes boundary layer control ( the RSRA/X-Wing design ). That was going to demand an Act of Faith on the part of the test pilot who pushed the ROTOR STOP button the first time up at speed.

( Thanks to Senior Pilot for putting up the pics in place of the link )

[cattletruck]

Awesome pics folks, first time I've seen them, thanks.

A pusher prop would also negate the need for using more forward cyclic at full speed and keep the airframe flatter with the airflow.

Seems like autorotations could get interesting with such a configuration especially the end bit, however I guess if you had enough height you could use the windmilling effect of the pusher prop to drive the MR-RPM back up again if it got too low.

[JohnDixson]

"You could use the windmilling effect of the pusher prop to drive the MR-RPM backup again.."

Not sure about that. You may recall the Lockheed AH-56 Cheyenne, which had both a tail rotor AND a pusher prop. Had a single GE T-64 engine. If I recall, there was an auto feather device for the pusher prop in the event of an engine failure. Perhaps someone from Lockheed can comment.

[JohnDixson]

Catlletruck, I found this AH-56 Flight Test Evaluation by the US Army Engr Flight Activity troops:
http://www.dtic.mil/dtic/tr/fulltext/u2/771914.pdf

Page 28 has some info re engine failure characteristics. For everyone else, it provides a glimpse into the AH-56 flying qualities and flight envelope limitations. This same group did an evaluation of the S-67 a few years later. The 67 had two engines.

[NutLoose]

JohnDixson

Already been tried as such

https://www.gizmodo.com.au/2013/11/this-wacky-sci-fi-plane-copter-hybrid-was-totally-almost-a-thing/

In films there was the one in The 6th Day that converted to a normal wing config in flight.

http://stargazer2006.online.fr/various/pages/whispercraft.htm

[JohnDixson]

NL, I noticed as to the second link:

" The movie's flying sequences were all done using computer graphics. " Indeed!

As to the first link, I must admit to never hearing mention of it, at least from 1966 to 2005, but perhaps Nick Lappos has. The possibility ( probability?? ) of a dynamics issue or two ( pun intended ) automatically come to mind.

[NutLoose]

Anyone mentioned the ejection seat? The US during Vietnam were attempting to develop a bang seat that would deeply rotors and be then flown by the ejectee away from te crash site.

[JohnDixson]

Like this?

https://m.youtube.com/watch?v=jLhZN7fTwQQ

jLhZN7fTwQQ

[SASless]

Dixson....you SOB!

You owe me a new Keyboard!

I watched that video and found early parts of of the narrative a bit funny.....but when the Guy said.....for purposes of this Test the Seats were occupied by Dummies....I formed a Mental Image of what it would look like if the Rotor Separation and Ejection system was ever tested in flight.....Well....I just wasted some very good Single Malt Whisky cleaning the iMac Screen and doing a deep soak of what I hope is liquid proof Keyboard. Dang...but that stuff burns coming out the nostrils!:ok:

Somehow "Dummies" just seemed so right somehow!

Perhaps I really was not cut out to be a Sikorsky Test Pilot!

[IFMU]

I did not know the SK Engineering Department used mind altering substances to that degree!
Even a bad idea, brought to flight test, is an awesome way to develop engineers. These guys went on to develop the Blackhawk later. What is more troubling is when management outsources the wacky ideas. Then not only do you not have a viable machine, your engineers are also no better.

[Margins]

A highly developed Gazelle...

A highly stupid developed Gazelle! What the reason for the fenestron?

[JohnDixson]

SAS: " but that stuff burns coming out the nostrils!"

You would have been hired-no doubts. Snorting single malt was one of the SA Pilot Office interview questions.

IFMU: Looking at the stowed rotor design info in the SA Archives, I saw the name on the drawing and am pretty certain that person had nothing to do with the S-67 design. Just nit picking here-concur with the point you were making.

[SASless]

Good money, time, and other resources spent on bad ideas is taken from other valid concepts that might prove far more beneficial.

The key is to be able to have the wisdom to decide what gets the attention.

[Cpt_Pugwash]

Margins,
I got a thump in the side from my partner for asking that very question during the film! It's only a film, so I guess it doesn't have to make sense.

Full details here Oblivion ? The Bubbleship | danielsimon (http://danielsimon.com/oblivion-bubbleship/)

[Tickle]

I thought it was for yaw control, since the thrust jets seem to be for propulsion.

Was amusing to see a "fan" mixed with such advanced tech, though. But it helped link it back to a helicopter.

[IFMU]

IFMU: Looking at the stowed rotor design info in the SA Archives, I saw the name on the drawing and am pretty certain that person had nothing to do with the S-67 design. Just nit picking here-concur with the point you were making.

I was more thinking of the bongo-tail pictures than the stowed rotor one. But, the same may be true.

[CertGuy]

One time in Louisiana, someone told me,
"If an OEM just realizes these are pickup trucks, and make the useful load 50% of max gross, no matter the size, it will sell."
He said it a bit more cajun flair.

[JohnDixson]

Wish that were true, CertGuy.Both the CH-54A/E and the CH-54B/F met that criteria and total Skycrane sales were 99, I believe.

[NickLappos]

It is fun reading all the wishes, especially having participated in the design of perhaps 15 aircraft. The real issue for us all it to recognize the physics of the situation. Making metal fly is not for the faint of heart, and certainly subject to laws that cant be appealed.
First among them is the recognize that all designs must balance, they cannot have too much of anything, or else they will have too little of something else. A design is like a soccer ball, with a field of pentagonal panels. On each panel we can write an attribute: Excess power, hover ceiling, fuel quantity, passengers, crash load limits, load factor strength, landing sink speed, OEI landing distance, etc, etc. Once we achieve a balance (where the aircraft actually meets its design levels of each attribute) we then want to add a bit more of one (more hover ceiling, for example) pilots have a great deal of difficulty realizing that we have to pull out that particular panel, but allow a few other panels to creep inward and lose some value. If we make the hover ceiling higher, we probably made the engine more powerful, which made it heavier, and eat more fuel, so the range and payload all dropped a bit. The design is balanced when the volume of that soccer ball stayed constant as the various panels are adjusted.


For example, I chuckle when someone decrees that the empty weight must be 50% of the MGW! Nice, but of course, if you want a lighter structure, you want a weaker structure. How weak, and where is it weak? Just let us know and we'll be glad to build to suit!

[JohnDixson]

Nick is this thread an appropriate venue to re-propose your project that would arm every new machine with bar coded ( or bonded transponder ) fatigue loaded parts etc etc?

[riff_raff]

"First among them is the recognize that all designs must balance, they cannot have too much of anything, or else they will have too little of something else."

Having worked on a few aircraft programs myself, this comment reminds me of the old engineering joke about design requirements - "A) Lightweight. B) High reliability. C) Low cost...... Pick any two."

[CRAN]

As a private pilot I'd like a machine that has 3-blades, runs on JET A1, carries four normal people, bags and 3.5hrs of fuel at 120kts and costs £25K per year to operate based on 75hrs/year flying.

Needs to be pretty too!

[Mac the Knife]

I have a vague memory of seeing a RotoDyne take off from Battersea Airport as a kid with my dad. I have a recall of it being noisy, but all aircraft were noisy in those days, it was part of the fun!

Seriously though, are the problems THAT insurmountable that no-one wants to revisit the concept? The advantages are obvious and engine design and aerodynamics are a lot further along than 60 years ago!

Those little Eland engines would hardly do for an APU these days, and with lightweight composites and maybe non-combusting tip-jets or better noise suppression, it would almost certainly be no more noisy than an Osprey and a great deal cheaper!

Or is a a question of "Been there. Done that. Didn't work. Next!"

Mac (just asking)

[PDR1]

Much has changed since then, but unfortunately the laws physics and thermodynamics remain the same. If you had "non-combusting" tip thrusters then you'd need a much higher mass flow (due to depending soley on gas energy rather than converting temperature energy into gas energy in the nozzles). And this mass flow would have to come from the hub, piped inside the blades.

So you need ducting large enough to carry the mass flow and strong enough to take the pressure, and some way of getting all this high-pressure gas from the static part of the hub to the rotating part without any leaks.

Solutions invited...

PDR

[riff_raff]

If you want to provide some design input for an Airbus rotorcraft project (https://vahana.aero/), go to this website. (https://github.com/VahanaOpenSource/vahanaTradeStudy) The vehicle is a single person, autonomous, tilt-wing VTOL rotorcraft, using battery-electric propulsion. The engineering team has posted their design models for public review and wants to hear what people think about their approach.

[Viper 7]

Make the dimensions such that it could be slid into the belly of a C130 with little to no maintenance.


Then we could deploy a rotary rescue asset to the Arctic (3-4 hours) in a fraction of the time it takes to fly a Cormorant up there (12-14 hours)...

[JohnDixson]

A very good idea, Viper, until you look at the cabin height of the 130 and balance that against the existing air vehicles that make decent Medevac machines.

Was there ever any thought about an air refueling capability for the EH-101? It wasn't in the requirements list for the S-92 as I recall. That's one way of extending the reasonable coverage for a rescue fleet of limited size. I've flown on both sides of the Canadian Arctic: Inuvik area and from Resolute down to Frobisher Bay, and I appreciate the point of your comment.

[dangermouse]

The 101 has an AAR capability, tested on a company machine in 2007 and fully qualified (including NVG ops) for the Italian airforce last year.

I guess the Canucks just have to ask (and pay) for the capability and have some tankers available (KC130J I believe)

DM