Lets make a helicopter
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Lets make a helicopter
There was an item on rotorheads a day or so ago suggesting pruners got together and designed or built a helicopter. It would be interesting to hear answers to the following. What engine size.? What make of engine.? What max weight.? Number of seats reqrd.? Total maximum cost.allowable.? Ammount of inertia required (give it in seconds a la Robinson) Number of blades.? Any other requirement in order to better the R22.
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Just an thought.
bugdevheli,
As an initial step, what about developing an acceptable list of the desired uses for this helicopter?
Here is a list that was developed from a previous request on PPRuNe. The web page relates to a specific craft but it may provide suggestions for this project; Uses for UniCopter
As an initial step, what about developing an acceptable list of the desired uses for this helicopter?
Here is a list that was developed from a previous request on PPRuNe. The web page relates to a specific craft but it may provide suggestions for this project; Uses for UniCopter
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1, Run on jeta1 (Diesel engine)
2, 2 comfortable sized seat
3, High enertia rotor
4, 2 blades or folding blades for small hangar
5, enough bagage for golf clubs or similar
6, no calander timed life parts
7, affordable enough to buy
Oh and how about a net to catch all those flying pigs that will be up there 1st!
2, 2 comfortable sized seat
3, High enertia rotor
4, 2 blades or folding blades for small hangar
5, enough bagage for golf clubs or similar
6, no calander timed life parts
7, affordable enough to buy
Oh and how about a net to catch all those flying pigs that will be up there 1st!
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I was going to ask for tandem seating (a la AH64) simply for the superb view (to identify hazards / other aircraft) but I suppose that would probably play havoc with the CoG in a light machine.
Solo from front? Yes, unless pilot weight > 70kg and fuel less than 65% or maximum gust forecast greater than 35% of mean wind speed and Skywatch installed...
Solo from front? Yes, unless pilot weight > 70kg and fuel less than 65% or maximum gust forecast greater than 35% of mean wind speed and Skywatch installed...
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- Supercharged 2-stroke diesel (Jet-A) - possibly a Dyna-Cam?
- rigid 4-bladed rotor system w/folding option
- fenestron anti-torque
- detatchable belly-mounted cargo pod
- skid gear
- two seats plus small cargo area behind seats
- 900-lb useful load
- 250nm range with 20-min reserve
- 100-kt cruise speed
- $300,000 USD fully equipped as an IFR trainer
Last edited by Flingwing207; 17th Nov 2004 at 22:37.
CONCEPT CRAN
It was me that made the original suggestion on the BCAR regulations thread regarding building our own machine. In response to bugdevheli's initial questions about the nature of the machine, one must first decide if it is to be a kit or is it to be a entry-level commercial helicopter, such as the R22. It is important to get this straight because the requirements and potential markets for the two machines are very different as are the technology strategies that you would employ.
Let’s assume we are talking kits...as was my initial intention...
The priorities for such a machine are very simple:
(1) RELIABILITY & SAFETY
----------------------------
The machine should be mechanically reliable and DESIGNED to the same standards as are required for fully certified light helicopter. The aircraft should be designed with low-time, inexperienced, low-ability pilots in mind. The handling qualities should be optimised to be docile, benign and to give the pilot the maximum time to react to any given situation either power on or off. The key points here are:
(a) High Inertia Rotor System (4 seconds pilot delay in cruise)
(b) De-rated, fuel-injected aircraft quality engine
(c) Adequate power (P/W = 0.23 hp/kg)
(b) Docile controls
(c) Benign reaction to low-g flight - careful optimisation of tail rotor thrust line.
(2) CRASHWORTHY AIRFRAME
---------------------------------
It doesn't matter what is done in terms of making the aircraft easy to fly and benign, entry-level helicopters will be crashed and will be crashed frequently, due to pilot error. Therefore, any engineer designing a new machine for this end of the market needs to accept 'mammoth crashworthiness' as a requirement for the machine. Crashworthiness means two things, the occupant volume must remain intact with the occupants safely secured within it and the surrounding airframe must be designed to absorb as much energy as possible. In addition, the fuel tanks must be rupture resistant to limit the well known fire risk.
(3) LOW, LOW COST
----------------------
The machine must be a minimum cost machine, though not at the expense of safety. Hourly cost accounting is somewhat different for kit helicopters as they rarely if ever fly enough hours to reach overhaul since they are entirely private machines, so much of the savings can be obtained here. Based on UK prices the hourly operating cost for a kit helicopter should be £45-£50/hour. [NOTE: Fuel is very expensive in the UK and accounts for about £30/hr] The target kit-price for the machine should be £45-50K, including engine and basic instruments and excluding taxes.
(4) SIMPLE LOW MAINTAINANCE REQUIREMENTS
----------------------------------------------------
One key design requirement is that the machine must require very little maintenance and what it does require must be easy to achieve. The machine must be designed with easy access to key components in mind and simple maintenance procedures. The machine should employ a 4000hr global retirement schedule, with no calendar time limit, rather components should be on-condition if they are not fight-time expired. Engine would be exchanged at 2000hrs as per manufacturers requirements.
(5) PERFORMANCE
--------------------
The aircraft should be designed to provide 'acceptable' performance. By this I mean, approx. 100kt cruise and 120kt max level flight speed. Range of 300nm @ 100kt, and the ability to achieve this while carrying two 16st [224lb] passengers and three hours of fuel, with acceptable power margins. Performance at altitude to be no worse than the existing R22 Beta II, though my inclination would be to improve it somewhat perhaps offering the turbo-normalised engine as an option.
(6) APPEARANCE & FIXTURES
--------------------------------
The aircraft should be drop-dead gorgeous, have doors that fit and have conventional dual controls. The interior should look like that of a modern car rather than a sit-on lawn mower.
ADDITIONAL INFORMATION
-----------------------------
The aircraft would be powered by a Superior Air Parts XP-IO-360 engine (or XP-TNIO-360 for high altitude operators), de-rated in speed and power to 160hp (5 mins) and 140 hp continuously. 100% of the parts are FAA certified (though it’s not a certified engine) and Superior has spent the last 30 years tweaking Lycomings design to improve both performance and reliability. The fuel injection eliminates carb icing and the engine can also be run on unleaded automotive fuel with no loss of performance. While I see the attraction of a diesel, no suitable engines exist for a 2-seat helicopter of this type, so we will stick with our bullet-proof big-bore flat fours!
An electronic rotor-speed govenor would be standard equipment.
The fuselage would be a hybrid construction, with a crashworthy composite cabin, steel-tube mid section and either aluminium or composite tail section.
The Rotor System would be a conventional high-inertia, two-blade teetering system, with either sealed rolling element feathering bearings or elastomeric feathering bearings ~ either way, low maintenance. Particular care would be paid to the aerodynamic design of the rotor system using the latest generation of rotor aerofoils, (multiple profiles across the span) for best possible performance. Blades would be composite construction.
The tail rotor would be a conventional 2-bladed open tail rotor, though it too would benefit from modern aerofoils and bearings.
There would also be a large internal volume for baggage (within the prescribed weight limits) and the option of cargo pods.
The cabin configuration is an interesting question. Initially my layouts had been for a side-by-side configuration as it is better for training and communicating with passengers. However a tandem arrangement as in the Apache is an all round better configuration from a technical standpoint. Contrary to Hilco's thoughts the tandem configuration will IMPROVE the CG over a sided-by side layout if designed correctly. In addition it provides major aerodynamic benefits that will lead to a higher cruise speed, not to mention the improved field of view for both parties and bigger feel to the cockpit.
If I had my way it would be a tandem seating arrangement, but i'm not sure that is what the market wants.
I hope this gives our group more of an understanding of what I have in mind and what is possible today!
CRAN
Let’s assume we are talking kits...as was my initial intention...
The priorities for such a machine are very simple:
(1) RELIABILITY & SAFETY
----------------------------
The machine should be mechanically reliable and DESIGNED to the same standards as are required for fully certified light helicopter. The aircraft should be designed with low-time, inexperienced, low-ability pilots in mind. The handling qualities should be optimised to be docile, benign and to give the pilot the maximum time to react to any given situation either power on or off. The key points here are:
(a) High Inertia Rotor System (4 seconds pilot delay in cruise)
(b) De-rated, fuel-injected aircraft quality engine
(c) Adequate power (P/W = 0.23 hp/kg)
(b) Docile controls
(c) Benign reaction to low-g flight - careful optimisation of tail rotor thrust line.
(2) CRASHWORTHY AIRFRAME
---------------------------------
It doesn't matter what is done in terms of making the aircraft easy to fly and benign, entry-level helicopters will be crashed and will be crashed frequently, due to pilot error. Therefore, any engineer designing a new machine for this end of the market needs to accept 'mammoth crashworthiness' as a requirement for the machine. Crashworthiness means two things, the occupant volume must remain intact with the occupants safely secured within it and the surrounding airframe must be designed to absorb as much energy as possible. In addition, the fuel tanks must be rupture resistant to limit the well known fire risk.
(3) LOW, LOW COST
----------------------
The machine must be a minimum cost machine, though not at the expense of safety. Hourly cost accounting is somewhat different for kit helicopters as they rarely if ever fly enough hours to reach overhaul since they are entirely private machines, so much of the savings can be obtained here. Based on UK prices the hourly operating cost for a kit helicopter should be £45-£50/hour. [NOTE: Fuel is very expensive in the UK and accounts for about £30/hr] The target kit-price for the machine should be £45-50K, including engine and basic instruments and excluding taxes.
(4) SIMPLE LOW MAINTAINANCE REQUIREMENTS
----------------------------------------------------
One key design requirement is that the machine must require very little maintenance and what it does require must be easy to achieve. The machine must be designed with easy access to key components in mind and simple maintenance procedures. The machine should employ a 4000hr global retirement schedule, with no calendar time limit, rather components should be on-condition if they are not fight-time expired. Engine would be exchanged at 2000hrs as per manufacturers requirements.
(5) PERFORMANCE
--------------------
The aircraft should be designed to provide 'acceptable' performance. By this I mean, approx. 100kt cruise and 120kt max level flight speed. Range of 300nm @ 100kt, and the ability to achieve this while carrying two 16st [224lb] passengers and three hours of fuel, with acceptable power margins. Performance at altitude to be no worse than the existing R22 Beta II, though my inclination would be to improve it somewhat perhaps offering the turbo-normalised engine as an option.
(6) APPEARANCE & FIXTURES
--------------------------------
The aircraft should be drop-dead gorgeous, have doors that fit and have conventional dual controls. The interior should look like that of a modern car rather than a sit-on lawn mower.
ADDITIONAL INFORMATION
-----------------------------
The aircraft would be powered by a Superior Air Parts XP-IO-360 engine (or XP-TNIO-360 for high altitude operators), de-rated in speed and power to 160hp (5 mins) and 140 hp continuously. 100% of the parts are FAA certified (though it’s not a certified engine) and Superior has spent the last 30 years tweaking Lycomings design to improve both performance and reliability. The fuel injection eliminates carb icing and the engine can also be run on unleaded automotive fuel with no loss of performance. While I see the attraction of a diesel, no suitable engines exist for a 2-seat helicopter of this type, so we will stick with our bullet-proof big-bore flat fours!
An electronic rotor-speed govenor would be standard equipment.
The fuselage would be a hybrid construction, with a crashworthy composite cabin, steel-tube mid section and either aluminium or composite tail section.
The Rotor System would be a conventional high-inertia, two-blade teetering system, with either sealed rolling element feathering bearings or elastomeric feathering bearings ~ either way, low maintenance. Particular care would be paid to the aerodynamic design of the rotor system using the latest generation of rotor aerofoils, (multiple profiles across the span) for best possible performance. Blades would be composite construction.
The tail rotor would be a conventional 2-bladed open tail rotor, though it too would benefit from modern aerofoils and bearings.
There would also be a large internal volume for baggage (within the prescribed weight limits) and the option of cargo pods.
The cabin configuration is an interesting question. Initially my layouts had been for a side-by-side configuration as it is better for training and communicating with passengers. However a tandem arrangement as in the Apache is an all round better configuration from a technical standpoint. Contrary to Hilco's thoughts the tandem configuration will IMPROVE the CG over a sided-by side layout if designed correctly. In addition it provides major aerodynamic benefits that will lead to a higher cruise speed, not to mention the improved field of view for both parties and bigger feel to the cockpit.
If I had my way it would be a tandem seating arrangement, but i'm not sure that is what the market wants.
I hope this gives our group more of an understanding of what I have in mind and what is possible today!
CRAN
Last edited by CRAN; 17th Nov 2004 at 22:43.
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Cran,
I do like the Tandam possibility, perhaps some sort of market reserch on this Rotorheads forum may show whether it would be acceptable by other pilots!
PeterR-B
I do like the Tandam possibility, perhaps some sort of market reserch on this Rotorheads forum may show whether it would be acceptable by other pilots!
PeterR-B
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Check this out
http://www.lafhelicopters.com/english/index_en.htm
A shame that they have run out of money for the moment
http://www.lafhelicopters.com/english/index_en.htm
A shame that they have run out of money for the moment
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The Lafhelicopters tandem design is so different to all other design concepts that to now fail due to funds is a loss to the rotorwing business.
Sure there will be many modifications to the design before it becomes commercial.
Sadly I do not have the required funds but somewhere there ought to be.
Here in the UK we sadly lack any enthusiasm for risk BUT have the Lafhelicopter team tried here in UK.
Such an idea should be persued to prove or otherwise the feasability of such a design to provide safe, easy to fly and relatively cost effective rotory flight. And yes get rid of the automotive engine and go for a single diesel or cosider a twin engine concept.
Sure there will be many modifications to the design before it becomes commercial.
Sadly I do not have the required funds but somewhere there ought to be.
Here in the UK we sadly lack any enthusiasm for risk BUT have the Lafhelicopter team tried here in UK.
Such an idea should be persued to prove or otherwise the feasability of such a design to provide safe, easy to fly and relatively cost effective rotory flight. And yes get rid of the automotive engine and go for a single diesel or cosider a twin engine concept.
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If you are really, really, going to do it...
Many of the fixed-wing kits (especially amphibians) are being produced with the intention of becoming certificated aircraft in the future. Cost, time, cost, regulations, cost and other factors (such as money - in case I haven't mentioned it) make it prohibitive to begin with certification as the initial goal. The R22 made it in before the new certification standards went into effect.
To be realistic, consider starting with a kit... but have the fore-site to plan for future certification (this WILL affect the business process and design). Oh, and who is going to manage the shares of private stock for investment? Flying Lawyer, care to opine on the legal apects if based in the U.K?
To be realistic, consider starting with a kit... but have the fore-site to plan for future certification (this WILL affect the business process and design). Oh, and who is going to manage the shares of private stock for investment? Flying Lawyer, care to opine on the legal apects if based in the U.K?
Precisely!
RD,
As I suggested in my initial post, the reason why we have such a great opportunity at the moment is that there is a raft of new regulations that for once have made things a little easier on the start-up manufacturer.
You are absolutely correct that the machine must be designed to meet the fully certified regulations as I stated above, but initially not manufactured by an 'approved' organisation or tested to the same extremes. In the UK for example (and the rest of the EASA/JAR member countries) this would be done using the BCAR VLH (or similar) kit regulations initially, though the machine would meet EASA-VLR ~ which offers a fully public transport CoA for rotorcraft under 750kg but makes use of the unique simplicity of small helicopters to reduce the certification burden. I have figures direct from the CAA on how much this is likely to cost and it's not unrealistic.
In the US, which lets face it has the biggest kit market, the aircraft are essentially unregulated in the experimental sector so the aircraft could steam straight in there and they are moving to develop the Primary Category Rotorcraft regulations which are based on EASA-VLR for simple and light weight certificated machines…again good news.
With this in mind any design for a potential light rotorcraft must be a sensible configuration and designed in such a way at to provide an easy (or as easy as it can be) ride through these various regulations as it progresses from ‘Superkit’ to ‘Certified’ status over a number of years. My proposal does this.
CRAN
As I suggested in my initial post, the reason why we have such a great opportunity at the moment is that there is a raft of new regulations that for once have made things a little easier on the start-up manufacturer.
You are absolutely correct that the machine must be designed to meet the fully certified regulations as I stated above, but initially not manufactured by an 'approved' organisation or tested to the same extremes. In the UK for example (and the rest of the EASA/JAR member countries) this would be done using the BCAR VLH (or similar) kit regulations initially, though the machine would meet EASA-VLR ~ which offers a fully public transport CoA for rotorcraft under 750kg but makes use of the unique simplicity of small helicopters to reduce the certification burden. I have figures direct from the CAA on how much this is likely to cost and it's not unrealistic.
In the US, which lets face it has the biggest kit market, the aircraft are essentially unregulated in the experimental sector so the aircraft could steam straight in there and they are moving to develop the Primary Category Rotorcraft regulations which are based on EASA-VLR for simple and light weight certificated machines…again good news.
With this in mind any design for a potential light rotorcraft must be a sensible configuration and designed in such a way at to provide an easy (or as easy as it can be) ride through these various regulations as it progresses from ‘Superkit’ to ‘Certified’ status over a number of years. My proposal does this.
CRAN
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What do you set as the craft's GW?
Regulations;
European ~ JAR Very Light Rotorcraft ~ Maximum weight 600 kg.
British ~ Very Light Helicopter ~ Maximum weight 750 kg
US ~ FAA - Light Sport Aircraft (potential for helicopter) ~ Maximum weight 560 kg
US ~ FAA - Ultralight (no pilot's license req'd) ~ Maximum Weight 115 kg, 143 kg w/ ballistic floats
Regulations;
European ~ JAR Very Light Rotorcraft ~ Maximum weight 600 kg.
British ~ Very Light Helicopter ~ Maximum weight 750 kg
US ~ FAA - Light Sport Aircraft (potential for helicopter) ~ Maximum weight 560 kg
US ~ FAA - Ultralight (no pilot's license req'd) ~ Maximum Weight 115 kg, 143 kg w/ ballistic floats
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For the rotorhub ~
May I suggest a 3-blade constant velocity rotor with hub spring?
This head is currently being developed for the US Ultralight category. Full information on this project can be seen here. The intent is to start producing the components for the hub in three or four weeks.
Should the initial testing of the prototype show it to have the desired advantages and no disadvantages, the PPRuNe group could develop a second larger one (presumably for one main rotor
) . The development and testing of the two different sizes (250 / 2rotors = 125 kg) and (700 kg) should be mutual advantageous.
This head is currently being developed for the US Ultralight category. Full information on this project can be seen here. The intent is to start producing the components for the hub in three or four weeks.
Should the initial testing of the prototype show it to have the desired advantages and no disadvantages, the PPRuNe group could develop a second larger one (presumably for one main rotor
) . The development and testing of the two different sizes (250 / 2rotors = 125 kg) and (700 kg) should be mutual advantageous.
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Just thinking about your post Cran,
"RELIABILITY & SAFETY"
Yup.
"CRASHWORTHY AIRFRAME"
Yup.
"LOW, LOW COST"
Yup - absolutely!
"SIMPLE LOW MAINTAINANCE REQUIREMENTS"
Yup.
"PERFORMANCE"
Not so critical, since just getting up there is good enough for me.
"APPEARANCE & FIXTURES"
Well...
"ADDITIONAL INFORMATION"
Engine makes sense, but is not light or cheap.
"The fuselage would be a hybrid construction, with a crashworthy composite cabin, steel-tube mid section and either aluminium or composite tail section."
Hmmm, cost is starting to mount. Whats wrong with steel tube? And yes you gan get it to absorb energy in a crash...
"The Rotor System would be a conventional high-inertia, two-blade teetering system"
Yuk! Gotta be 3-blade rigid, cos chaps like me can't afford all the hours required getting aquanted with the dynamics of teetering rotors. If there is already electronics for RRPM control, why not go "trim by wire" to give rigid rotors nice characteristics in forwards flight? I'm actually a great fan of the original Lockheed spring/gyro control system.
"The tail rotor would be a conventional 2-bladed open tail rotor, though it too would benefit from modern aerofoils and bearings."
I've never been sure about tail rotors, they seem to have all sorts of interesting dynamics of their own. If the design is advanced aerodynamics, why not investigate stator downwash correction for anti-torque. Better still make the thing symmetrical, so idiots like me don't get left and right confused...
"The cabin configuration is an interesting question."
Oh thats easy, just me and the bloke behind me that utters those famous words: "Er - I have control!"
Mart
"RELIABILITY & SAFETY"
Yup.
"CRASHWORTHY AIRFRAME"
Yup.
"LOW, LOW COST"
Yup - absolutely!
"SIMPLE LOW MAINTAINANCE REQUIREMENTS"
Yup.
"PERFORMANCE"
Not so critical, since just getting up there is good enough for me.
"APPEARANCE & FIXTURES"
Well...
"ADDITIONAL INFORMATION"
Engine makes sense, but is not light or cheap.
"The fuselage would be a hybrid construction, with a crashworthy composite cabin, steel-tube mid section and either aluminium or composite tail section."
Hmmm, cost is starting to mount. Whats wrong with steel tube? And yes you gan get it to absorb energy in a crash...
"The Rotor System would be a conventional high-inertia, two-blade teetering system"
Yuk! Gotta be 3-blade rigid, cos chaps like me can't afford all the hours required getting aquanted with the dynamics of teetering rotors. If there is already electronics for RRPM control, why not go "trim by wire" to give rigid rotors nice characteristics in forwards flight? I'm actually a great fan of the original Lockheed spring/gyro control system.
"The tail rotor would be a conventional 2-bladed open tail rotor, though it too would benefit from modern aerofoils and bearings."
I've never been sure about tail rotors, they seem to have all sorts of interesting dynamics of their own. If the design is advanced aerodynamics, why not investigate stator downwash correction for anti-torque. Better still make the thing symmetrical, so idiots like me don't get left and right confused...
"The cabin configuration is an interesting question."
Oh thats easy, just me and the bloke behind me that utters those famous words: "Er - I have control!"
Mart
Mart,
Thanks for the constructive post. A few follow-up posts if I may:
ENGINE:
---------
As you have clearly picked up, the XP-IO-360 is the best compromise, out of a pretty dire set of alternatives. Not cheap and not light...tell me about it. Unfortunately, I am yet to discover a better solution. In the past I have studied a number of potential powerplant options and have consistently failed to satisfy all of my criteria. People often suggest using modern automotive engines, with their high level of technology and apparent reliability. Unfortunately to get a power-to-weight ratio out of a modern automotive engine that can come anywhere near a Lycoming you would have to run them so hard that I have grave reservations about their reliability and life expectancy. Indeed this is my major reservation about the Lafamme project referenced earlier in this thread. The interested readers can have a look at what the maximum continous power ratings are for some of ford’s automotive engines in INDUSTRIAL applications: www.fordpowerproducts.com
Another option is the use of a surplus APU or de-rated surplus turbo-shaft engines. Nonsense, not even going to discuss that!
Modern 2-stroke Engines; light, cheap...but unreliable.
Motorcycle engines? Again you would need to thrash them, so reliability and longevity is a problem.
Modern aero-diesels? None of an appropriate size, generally heavier, very expensive to buy and unproven reliability.
How about a VW-derivative as used by drag/street racers and fixed wing guys? Possible and definitely cheap, but I have serious reservations about the reliability. Have a look at: www.altimizer.com and www.scatenterprises.com/vwcatalog.html
How about a radial engine made out of VW-parts? Again proving the reliability is the issue.
How about a design from scratch, using as much automotive hardware as possible? This is definitely a good idea, but the time and cost of such an undertaking renders it economically unachievable for a kit helicopter project.
The bottom line about engines for helicopters is this...Helicopters are one of the most demanding duty-cycles conceivable for engines of any description. In addition, helicopters require an engine that is super-light and super-reliable and those two properties do not go hand-in-hand. Therefore, in any helicopter project the choice of the engine is by far the most important one and reliability must be the key driver of the selection.
I have selected the XP-IO-360 because it is a known quantity, installed properly, i.e. de-rated, it will provide reliable trouble-free power and inspire confidence in the pilots. We are able to make cost savings elsewhere in the aircraft (simple conventional design) and my proposal trades off these savings against using a good engine, rather than reducing the purchase price further still by using a lesser engine.
Remember, there is no free lunch and you certainly get what you pay for.
So I say again, for a KIT helicopter the only practical choice is the XP-IO-360. However, if I were designing a replacement R22, then I would definitely start with the development of a better engine...but what type, well, that would be telling.
FUSELAGE CONSTRUCTION:
------------------------------
What's wrong with steel tube? W E I G H T ! ! ! By the time you have a crashworthy, robust aircraft with sufficient fatigue strength and have faired it in nice fibre-glass clothing you have got yourself a hefty lump to lift. Remember, helicopters (especially ones that have to carry around heavy piston engines) are extremely sensitive to airframe weight. Unlike fixed wing aircraft every kilogram of extra weight you weld into the airframe, is a kilo of payload lost. The composites I had in mind for the cabin do not involve wall-to-wall exquisite space-age materials, as you rightly point out this would cost far too much, rather the careful application of fibreglass, with carbon and/or kevlar only where necessary. Not nearly as expensive as you might think! Infact it’s rather cost-effective in the volumes we’re talking about.
ROTOR SYSTEM(S):
---------------------
When you said rigid, did you really mean rigid or articulated or really rigid like the BO-105? There is a very strong case to be made for using a 3-bladed articulated hub but in my mind it is not the way to go.
You put three blades on and what do you get? More control power, more damping and hence better handling qualities and improved handling in low-g flight. Nobody would argue with this... But what about the substantial additional cost, weight and complexity. What about ground resonance? What about the additional dampers required in the undercarriage? What about the additional space required to hangar the beast or the cost and complexity of a blade fold mechanism? None of these items are really in line with our goal of designing a cheap and reliable helicopter are they?
I'm also not sure I agree with your sweeping generalisation regarding teetering machines. Have you flown a Bell 47 or a Hiller? Jet Ranger? The 'skittish' behaviour of the R22 is due to a variety of factors regarding its design and configuration and not because it uses a teetering rotor system. I don't believe that you would need 'all the hours to get acquainted with a teetering system' and even if you did ~ it would still be about a third the price of the same time in an R22, nearer a quarter in a S300!
With a project like this the most important thing is to take on something that is achievable with the resources available and it is for the reason that I discounted 'novel' configurations. By using a reliable engine and a simple 2-bladed teetering main and tail rotor we have an engineering task that is viable with limited resources. While I would certainly consider sculpting the tail boom to off-load the tail rotor in a passive manner in the hover two major issues spring to mind:
(1) The main rotor will be lightly loaded and so the downwash will be much slower than that of the MD900 for example (less than 40% in fact), therefore the area and indeed weight of such devices would present a significant design problem.
(2) With a passive device to 'assist' the tail rotor, invariably what would happen would be what was a helpful effect in one flight regime would be harmful in another, the net result being nothing special.
SEATING CONFIGURATION:
-----------------------------
I'm glad you like the tandem concept as there are some serious technical benefits for a two seater in this configuration!
GENERAL REMARKS:
----------------------
If a project such as this is to succeed then the technical task must be realistic and the resulting machine must meet the agreed specification. Mart and Dave have both highlight elements of the proposal that could be 'sexed-up' with novel, high-tech or more sophisticated systems that potential offer big advantages. Sadly, the reality of a project like this is that if it were ever to get of the ground it would receive the minimum funding imaginable and those that had invested hard-earned pennies would want results...and quickly. The configuration I have laid out for our machine is simple and achievable. All of the technologies employed have been done-to-death either in the aircraft sector or other sectors and only need to be 'embodied' in the aircraft. If there were technical problems along the way, there is plenty of experience in our group and the wider community that would be able to shed some light on it and get us moving again quickly.
As Nick said in his Pilot Magazine interview; 'This is Dan's all you can eat restaurant and that's all you can eat!' Keep it simple and to an agreed specification and we can succeed, over complicate it and we will certainly fail. I spent many years doing 'blue-skies' research and applied research in the helicopter industry (aerodynamics) and i'll tell you now, novelty will get us nowhere fast.
IMHO if it was going to be done then the design should be an exceptionally-crafted embodiment of proven and reliable technologies that will serve us all safely, until we are all sick of fly helicopters.
We can always add clever things to it later...
Once again, thanks for the input Mart (and everyone else) it's very much appreciated, keep it coming.
CRAN
Thanks for the constructive post. A few follow-up posts if I may:
ENGINE:
---------
As you have clearly picked up, the XP-IO-360 is the best compromise, out of a pretty dire set of alternatives. Not cheap and not light...tell me about it. Unfortunately, I am yet to discover a better solution. In the past I have studied a number of potential powerplant options and have consistently failed to satisfy all of my criteria. People often suggest using modern automotive engines, with their high level of technology and apparent reliability. Unfortunately to get a power-to-weight ratio out of a modern automotive engine that can come anywhere near a Lycoming you would have to run them so hard that I have grave reservations about their reliability and life expectancy. Indeed this is my major reservation about the Lafamme project referenced earlier in this thread. The interested readers can have a look at what the maximum continous power ratings are for some of ford’s automotive engines in INDUSTRIAL applications: www.fordpowerproducts.com
Another option is the use of a surplus APU or de-rated surplus turbo-shaft engines. Nonsense, not even going to discuss that!
Modern 2-stroke Engines; light, cheap...but unreliable.
Motorcycle engines? Again you would need to thrash them, so reliability and longevity is a problem.
Modern aero-diesels? None of an appropriate size, generally heavier, very expensive to buy and unproven reliability.
How about a VW-derivative as used by drag/street racers and fixed wing guys? Possible and definitely cheap, but I have serious reservations about the reliability. Have a look at: www.altimizer.com and www.scatenterprises.com/vwcatalog.html
How about a radial engine made out of VW-parts? Again proving the reliability is the issue.
How about a design from scratch, using as much automotive hardware as possible? This is definitely a good idea, but the time and cost of such an undertaking renders it economically unachievable for a kit helicopter project.
The bottom line about engines for helicopters is this...Helicopters are one of the most demanding duty-cycles conceivable for engines of any description. In addition, helicopters require an engine that is super-light and super-reliable and those two properties do not go hand-in-hand. Therefore, in any helicopter project the choice of the engine is by far the most important one and reliability must be the key driver of the selection.
I have selected the XP-IO-360 because it is a known quantity, installed properly, i.e. de-rated, it will provide reliable trouble-free power and inspire confidence in the pilots. We are able to make cost savings elsewhere in the aircraft (simple conventional design) and my proposal trades off these savings against using a good engine, rather than reducing the purchase price further still by using a lesser engine.
Remember, there is no free lunch and you certainly get what you pay for.
So I say again, for a KIT helicopter the only practical choice is the XP-IO-360. However, if I were designing a replacement R22, then I would definitely start with the development of a better engine...but what type, well, that would be telling.
FUSELAGE CONSTRUCTION:
------------------------------
What's wrong with steel tube? W E I G H T ! ! ! By the time you have a crashworthy, robust aircraft with sufficient fatigue strength and have faired it in nice fibre-glass clothing you have got yourself a hefty lump to lift. Remember, helicopters (especially ones that have to carry around heavy piston engines) are extremely sensitive to airframe weight. Unlike fixed wing aircraft every kilogram of extra weight you weld into the airframe, is a kilo of payload lost. The composites I had in mind for the cabin do not involve wall-to-wall exquisite space-age materials, as you rightly point out this would cost far too much, rather the careful application of fibreglass, with carbon and/or kevlar only where necessary. Not nearly as expensive as you might think! Infact it’s rather cost-effective in the volumes we’re talking about.
ROTOR SYSTEM(S):
---------------------
When you said rigid, did you really mean rigid or articulated or really rigid like the BO-105? There is a very strong case to be made for using a 3-bladed articulated hub but in my mind it is not the way to go.
You put three blades on and what do you get? More control power, more damping and hence better handling qualities and improved handling in low-g flight. Nobody would argue with this... But what about the substantial additional cost, weight and complexity. What about ground resonance? What about the additional dampers required in the undercarriage? What about the additional space required to hangar the beast or the cost and complexity of a blade fold mechanism? None of these items are really in line with our goal of designing a cheap and reliable helicopter are they?
I'm also not sure I agree with your sweeping generalisation regarding teetering machines. Have you flown a Bell 47 or a Hiller? Jet Ranger? The 'skittish' behaviour of the R22 is due to a variety of factors regarding its design and configuration and not because it uses a teetering rotor system. I don't believe that you would need 'all the hours to get acquainted with a teetering system' and even if you did ~ it would still be about a third the price of the same time in an R22, nearer a quarter in a S300!
With a project like this the most important thing is to take on something that is achievable with the resources available and it is for the reason that I discounted 'novel' configurations. By using a reliable engine and a simple 2-bladed teetering main and tail rotor we have an engineering task that is viable with limited resources. While I would certainly consider sculpting the tail boom to off-load the tail rotor in a passive manner in the hover two major issues spring to mind:
(1) The main rotor will be lightly loaded and so the downwash will be much slower than that of the MD900 for example (less than 40% in fact), therefore the area and indeed weight of such devices would present a significant design problem.
(2) With a passive device to 'assist' the tail rotor, invariably what would happen would be what was a helpful effect in one flight regime would be harmful in another, the net result being nothing special.
SEATING CONFIGURATION:
-----------------------------
I'm glad you like the tandem concept as there are some serious technical benefits for a two seater in this configuration!GENERAL REMARKS:
----------------------
If a project such as this is to succeed then the technical task must be realistic and the resulting machine must meet the agreed specification. Mart and Dave have both highlight elements of the proposal that could be 'sexed-up' with novel, high-tech or more sophisticated systems that potential offer big advantages. Sadly, the reality of a project like this is that if it were ever to get of the ground it would receive the minimum funding imaginable and those that had invested hard-earned pennies would want results...and quickly. The configuration I have laid out for our machine is simple and achievable. All of the technologies employed have been done-to-death either in the aircraft sector or other sectors and only need to be 'embodied' in the aircraft. If there were technical problems along the way, there is plenty of experience in our group and the wider community that would be able to shed some light on it and get us moving again quickly.
As Nick said in his Pilot Magazine interview; 'This is Dan's all you can eat restaurant and that's all you can eat!' Keep it simple and to an agreed specification and we can succeed, over complicate it and we will certainly fail. I spent many years doing 'blue-skies' research and applied research in the helicopter industry (aerodynamics) and i'll tell you now, novelty will get us nowhere fast.
IMHO if it was going to be done then the design should be an exceptionally-crafted embodiment of proven and reliable technologies that will serve us all safely, until we are all sick of fly helicopters.
We can always add clever things to it later...
Once again, thanks for the input Mart (and everyone else) it's very much appreciated, keep it coming.
CRAN
Last edited by CRAN; 19th Nov 2004 at 21:56.
Join Date: Oct 2004
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Hi cran, just my opinion for the litle it is worth...
ENGINE:
---------
People often suggest using modern automotive engines, with their high level of technology and apparent reliability.
>>>> now most of the common jap engines (even small ones) can get over 200 000 km without any big problem.
Another option is the use of a surplus APU or de-rated surplus turbo-shaft engines. Nonsense, not even going to discuss that!
>>>> apu are available and quite cheap, who is going to overhaul them ? COSTY operators. cheap parts ? no, available "old series" parts ? no, unless you can really operate a recent apu, i would forget that. btw gearing is heavy and costy and R&D hungry.
Modern 2-stroke Engines; light, cheap...but unreliable.
>>>> a FAA certified 2 stroke, could be as reliable as a lyco, but 2 strokes are nor FAA aproved, because no one would certify a such endless gas pit.
Motorcycle engines? Again you would need to thrash them, so reliability and longevity is a problem.
>>>> wrong, the suzuki bandit is well known for its reliability and availability, you told about using automotive parts ? it is a good example.
Modern aero-diesels? None of an appropriate size, generally heavier, very expensive to buy and unproven reliability.
>>> the dieselis i heavier, but lowers the costs in a significant way over time, not for recreationnal local flights, BTW it has a huge torque.
How about a VW-derivative as used by drag/street racers and fixed wing guys? Possible and definitely cheap, but I have serious reservations about the reliability.
>>>> cheap if bare ! costy and unreliable if custom prepared.
How about a radial engine made out of VW-parts? Again proving the reliability is the issue.
>>>> R&D it..
FUSELAGE CONSTRUCTION:
------------------------------
i agree for composites, but not single skin hulls > heavier and costy than tubes, but nicer.
why didnt anyone had the idea of cheap honeycomb ? light, stiff, easy to assemble.
ROTOR SYSTEM(S):
---------------------
When you said rigid, did you really mean rigid or articulated or really rigid like the BO-105?
>>>> th BO105 is called rigid but behaves like a semi-rigid. the blades endure bending.
3-bladed articulated hub but in my mind it is not the way to go.
But what about the substantial additional cost, weight and complexity.
>>> i disagree, the ecureil proved the 3 bladed design can be 40 % lighter, 40 % cheaper and 40 % simpler
What about ground resonance?
>>> the same as in an articulated, with less risk due to semi-rigid setup.
SEATING CONFIGURATION:
-----------------------------
I'm glad you like the tandem concept as there are some serious technical benefits for a two seater in this configuration!
>>> i love this config but instructors will stay away from this as thay like to have their students aside, that would mean double instruments panel.
GENERAL REMARKS:
----------------------
classicism vs innovation is a bad struggle.
accordding to ones, nothing can be done better than existing...
and others just dump everything old going in fully-rigid-innovating-over-engineering-thinking.
i m not an engineer, just giving an arrogant opinion
thanks
ENGINE:
---------
People often suggest using modern automotive engines, with their high level of technology and apparent reliability.
>>>> now most of the common jap engines (even small ones) can get over 200 000 km without any big problem.
Another option is the use of a surplus APU or de-rated surplus turbo-shaft engines. Nonsense, not even going to discuss that!
>>>> apu are available and quite cheap, who is going to overhaul them ? COSTY operators. cheap parts ? no, available "old series" parts ? no, unless you can really operate a recent apu, i would forget that. btw gearing is heavy and costy and R&D hungry.
Modern 2-stroke Engines; light, cheap...but unreliable.
>>>> a FAA certified 2 stroke, could be as reliable as a lyco, but 2 strokes are nor FAA aproved, because no one would certify a such endless gas pit.
Motorcycle engines? Again you would need to thrash them, so reliability and longevity is a problem.
>>>> wrong, the suzuki bandit is well known for its reliability and availability, you told about using automotive parts ? it is a good example.
Modern aero-diesels? None of an appropriate size, generally heavier, very expensive to buy and unproven reliability.
>>> the dieselis i heavier, but lowers the costs in a significant way over time, not for recreationnal local flights, BTW it has a huge torque.
How about a VW-derivative as used by drag/street racers and fixed wing guys? Possible and definitely cheap, but I have serious reservations about the reliability.
>>>> cheap if bare ! costy and unreliable if custom prepared.
How about a radial engine made out of VW-parts? Again proving the reliability is the issue.
>>>> R&D it..
FUSELAGE CONSTRUCTION:
------------------------------
i agree for composites, but not single skin hulls > heavier and costy than tubes, but nicer.
why didnt anyone had the idea of cheap honeycomb ? light, stiff, easy to assemble.
ROTOR SYSTEM(S):
---------------------
When you said rigid, did you really mean rigid or articulated or really rigid like the BO-105?
>>>> th BO105 is called rigid but behaves like a semi-rigid. the blades endure bending.
3-bladed articulated hub but in my mind it is not the way to go.
But what about the substantial additional cost, weight and complexity.
>>> i disagree, the ecureil proved the 3 bladed design can be 40 % lighter, 40 % cheaper and 40 % simpler
What about ground resonance?
>>> the same as in an articulated, with less risk due to semi-rigid setup.
SEATING CONFIGURATION:
-----------------------------
I'm glad you like the tandem concept as there are some serious technical benefits for a two seater in this configuration!
>>> i love this config but instructors will stay away from this as thay like to have their students aside, that would mean double instruments panel.
GENERAL REMARKS:
----------------------
classicism vs innovation is a bad struggle.
accordding to ones, nothing can be done better than existing...
and others just dump everything old going in fully-rigid-innovating-over-engineering-thinking.
i m not an engineer, just giving an arrogant opinion
thanks
Thanks Zeeoo,
That’s not an arrogant opinion, it's a useful one!
With regards your remarks on the use of composite; I had taken the word 'composite' to include all of the common implementations including sandwich panels - sorry if this was misleading.
I disagree with your remarks about automotive engines, those 200,000 km are all at a very low power settings with only short duration bursts of high revs and high power, a helicopter application would require that the engine (either automotive or motorcycle) be used close to maximum continuous power for the vast majority of the time and would lead to serious reliability problems.
The Star-flex rotor system was a great success for Aerospatiale, however the 40% cheaper, lighter and simpler is relative to a traditional articulated hub of the same size, NOT a two blade teetering system, the teetering system can be almost an order of magnitude cheaper! Both the starflex hubs and the more recent spheriflex hubs are excellent pieces of engineering, but i'm not convinced they are appropriate for a bargain-basement kit helicopter.
I don't think the struggle between tradition and innovation is quite as big a deal as you make out. One must innovate to succeed when there is strong competition and the product must have that extra 'x-factor' to win the business. However, this is not the current situation for the kit helicopter market. To gain a 95% market share all you would need to do is have a competitively priced machine, that was well engineered, safe, reliable and attractive and you simply don't need risky technologies to achieve that.
Keep the comments coming guys, this is all good stuff!
CRAN
That’s not an arrogant opinion, it's a useful one!
With regards your remarks on the use of composite; I had taken the word 'composite' to include all of the common implementations including sandwich panels - sorry if this was misleading.
I disagree with your remarks about automotive engines, those 200,000 km are all at a very low power settings with only short duration bursts of high revs and high power, a helicopter application would require that the engine (either automotive or motorcycle) be used close to maximum continuous power for the vast majority of the time and would lead to serious reliability problems.
The Star-flex rotor system was a great success for Aerospatiale, however the 40% cheaper, lighter and simpler is relative to a traditional articulated hub of the same size, NOT a two blade teetering system, the teetering system can be almost an order of magnitude cheaper! Both the starflex hubs and the more recent spheriflex hubs are excellent pieces of engineering, but i'm not convinced they are appropriate for a bargain-basement kit helicopter.
I don't think the struggle between tradition and innovation is quite as big a deal as you make out. One must innovate to succeed when there is strong competition and the product must have that extra 'x-factor' to win the business. However, this is not the current situation for the kit helicopter market. To gain a 95% market share all you would need to do is have a competitively priced machine, that was well engineered, safe, reliable and attractive and you simply don't need risky technologies to achieve that.
Keep the comments coming guys, this is all good stuff!
CRAN