Ideal Private Helicopter
 

In recent times there has been a number of efforts to reduce the cost associated with recreational flying and improve access to GA around the world. Efforts include the introduction of light sport aircraft as an alternative to the aging existing fleet, however these small aircraft in general have been met with a poor uptake, due mainly to limited capability. It seems the appetite for these small lightweight machines is simply not there as you simply can’t do enough with them.

Robinson has often been quoted stating that there is very little difference in cost in manufacturing the R22 & R44 and in recent years the R44 has far our sold the R22 despite its much higher cost.

This got me thinking, if you were to set off to design the perfect helicopter for personal ownership and private flying would it be a 2-seater or a 4-seater?

Assuming that development budget and investment in appropriate modern manufacturing methods are not limiting factors, I have hypothetically created and costed two machines based on current state-of-art for piston aircraft.


http://i1248.photobucket.com/albums/...psldgdsnig.png

So question is, which one would you buy and why?

CRAN
:ok:

Would depend a lot on type of personal flying done, it you are mostly bashing out circuit type stuff by yourself or the odd friend - you would be foolish to blow $60K = $4.5K extra.

If you are taking the Mrs or a mate or 2 camping or fishing - the 4 is obvious way to go.

If you got a family!

Go the JetBox.......safe, reliable, proven!

Perhaps we might start with a helo whose purchase cost reflected it's manufacturing cost.

That statement is either a clumsy misquote or a shocking revelation by Crapinson that they are blatantly profiteering with the R44.

Doesn't make sense. The R44 is more complicated with its hydraulic system and bigger engine.

Not a great deal of price difference between a new Lyco 4 & 6 cylinder engine - I would guess $7-10K. Component costs and installation (during manufacture) time would not necessarily cost more than manual system.

So why the much higher purchase price?

I would say the extra liability premium for 2 extra seats would be the main factor.

To list but a few - insurance risk increase by # pax.

Robinson Helicopter Company in Torrance subject of wrongful death lawsuit


https://www.baumhedlundlaw.com/fatal...helicopter-co/

Bit of thread drift here. The idea wasn't to illicit more Robinson bashing, but to understand whether your typical private pilot and would-be owner would choose a marginally lower cost 2 seat machine over a more capable and flexible four seater, albeit with slightly higher cost.

Thanks for the posts so far guys.
CRAN

CRAN, you beat me to it: how on earth your throwaway line about R22/R44 has turned into a Robinson discussion just shows the narrow focus of some Rotorheads.

Without a doubt the concept of a 4 seater being only 30% more than a two seater would significantly influence a buyers decision, but your projected baggage limit is woefully small. 2.5kg per pax, without accounting for passengers weights?

Why would two seater weights be 95kg each, but 4 seater only allows average of 85kg each? I'd suggest a drastic rethink of the payload would be in order for this proposal to be attractive to the private market.

Hi John,

Thanks. The problem as always is the availability of a sufficient engine for the four seater. There are some convienient options for a high powered 2-seater that improve the per-seat payload. At 1250kg, you a right up against the power limit for a naturally aspirated conventional piston engine. You could solve it with a turbo engine, but they are ALOT more expensive.

The turbo engine would get you another 150kg of AUW, but cost another $50K and burn more fuel. Is it worth it? My original design point was attempting to keep purchase and operating costs as reasonable as possible.

Thoughts welcome?

CRAN

Try K1

NEW MODEL KISS 216

Turbine engined

That K1 is interesting, with the hybrid drive giving an extra 50hp in low power flight, or to assist in autorotation.

At those prices and the design criteria you have it probably won't have a Type Certificate.

3 things that possibly miss the mark in your "hypothesis".

3 blade "high inertia" rotor

Piston engine

Payload

Pick 2. :confused:

This is not the case; it just requires proper engineering. Guimbal has all three and the performance metrics I've outlined are within those used on the Guimbal and Robinson Products.

A piston engine doesn't mean you can't have high inertia or payload, it just means that for a given payload and inertia your all up weight will be higher.

As demonstrated by the performance difference between R22 and G2.

G2 is made from contemporary high performance materials and the 22 is made from tin and steel yet outperforms the G2 in IGE/OGE hover by a factor of nearly 2 with the same engine?

If it was all that simple!! :D

It comes down to what design mission is required. It would have been easy to install a higher powered variant of the O-360 in the G2 and increase all the performance parameters, but this would of led to higher fuel burn. However it's mission is training and minimal operating costs; hence the current trade off is to let the altitude performance go and keep the low fuel burn.

I've had heard rumours that there is a 165hp version of the engine in the works, for those wanting higher altitude performance and cruise speed.

We're drifting again!

Not if you read the Lycoming manufacturers data.

The SFC on the "higher powered" injected models for the same HP is lower.

The O360 J2A is "derated" only with the line on the MAP gauge and the MGB limitations.

Read Ray Prouty's sections on "design tradeoffs" - they are a lot different to what you portray as the issue.

Its all about picking yourself up by your shoelaces!!

4 seat every time
 

The extra seats well worth the extra money for me.

I think a serious investigation into diesel engines would be worthwhile. Lower fuel flow, great torque spread, and the later gen engines are much lighter than previous ones - twin turbo units easily producing 300shp, which is equivalent to the RR turbine in the R66.

I believe RHC have already installed a diesel unit into an R44.

As a petrolhead, I'm always amazed by how low-tech the Lycomings are compared to the automotive market offerings, and think even with petrol engines, there are some huge gains in power and torque vs mass to be made. This change in itself would dramatically increase the envelope of operations for a machine like those you've suggested.

You can't compare automotive and aero engine designs. A 350bhp road car engine will be producing 350bhp for a few seconds at a time, and for >95% of the time will only be running at 50bhp or lower (the "cruise" power requirement of a saloon car on a motorway). A 350bhp aero engine will usually need to run at nearly 200bhp for >80% of its use, and will need to be able to do 350bhp for five minutes at a time (or more).

The 900bhp of an F1 turbo-hybrid engine comes with a TBO of no more than 15hours.

The reliability and integrity requirements for an aero engine don't allow some of the design trade-offs used in automotive engines. Aero-engines can't use belt or chain-driven cams; they must be gear driven to provide a graceful failure mode. The backlash in gear-driven cams prevents some of the more extreme valve timings being used, and they would risk valve and piston collisions.

Aero engine crankcases must usually accomodate thrust and gyroscopic propeller loads, where a car engine crankcase (outside of a few single0-seat racer applications) only carries torque loads.

Finally - much of the power & flexibility of modern car engines is achieved using electronic injection/ignition/management systems which are difficult to certify for aero use. The one time something like this was seriously attempted was the Porsche PFM 3200 (a varient of the 911 flat six) of the 80s, and whilst that did make it into production there was a lot of hassle over its electronic control systems, and the on-going cost of that was one of the larger factors in its demise. It has to be said that *some* of the resistance to the electronic systems was just typical american "not invented here-ness" lobbying to protect US industry against the European competition, but not all of it. The general downturn in light aviation in the 80s due to product liability and the mind-bogglingly stupid excesses of the american legal system was also a contributory factor.

PDR

Hello CRAN :)

Without a doubt, 4 seats for the reasons which you evoke.
.

But PDR you put a big automotive engine in then, so your 350 hp engine has to power say a 300 which has a 190 hp engine which quite frankly doesn't use anything like 190 in a cruise.
This is where the ridiculous certification requirements miss the point. Lets face it is it correct that a Lycoming only has an oil consumption problem when it gets to a US quart an hour :eek: