View Full Version : Professional Opinions Sought on Experimental Helicopters


nucleus33
12th Apr 2002, 05:44
Recently, an opinion was rendered on the"Sport Helicopter & Pilot Global Information Exchange" http://www.usbusiness.com/helicopter/index.htm regarding the the Rinke Aerospace JAG Experimental Helicopter www.rinke-aerospace.com/ which is supposed to be flying soon...

Donald Hillberg is the designer/builder of the Rotormouse (Rotermouse?) http://www.pra.org/directory/rotormouse.html

I am curious as to all your thoughts about the JAG, the Rotormouse, and the criticism of the JAG. As regards the JAG criticism, in particular I am curious about the apparent tight clearances between the MR and TR, the shortness of the TR boom, the rounded edges leading to random flow separation and "wallowing and oscillating in hover like an Astar", I've heard this about the Astar, true?

All comments appreciated and I hope its okay to hijack your professional pilots forum for some discussion on the experimentals.

Below find the referenced quote. Also for those that are curious here is the link to all the PRA listings for experimental helicopters: http://www.pra.org/helicopter1.htm

Thank You,

Hans Conser


DONALD HILLBERG's
(the father of the Rotermouse)
2 cents on the above helicopter.

I have seen the Mini in Drag, a two place, Allison powered A/C and like Cesear, it gets a thumbs down. I talked to the master  Head cheese and he attacked and defended his baby ,I will list a number of faults in the "Drag Queen" ,And to cover my but, These are my opinions ,(25 years worth)  Now where do I start?

1. Carbon fibre forward cockpit, Once compromised will do nothing to protect the pilots. And
fractured carbon is sharper than sharp ,it will cut you ,stab you, wipe you out.

2. Rounded edges on the tail fan ,Air flow separation / Coannda effect will defect yaw thrust
stability,Increase pilot work load,And  as fat as the attachment is to the tail gear box not good
for flow/noise/use of power.(looks like bow thruster on boat)and as short coupled it will be a
foot full.  (damn it still looks like a bat part)

3.inproper testing of blades (the web site makes no mention of a real test ,pulling the blade up on
a rig is fun to see but its not cyclic load/sympathetic excitement testing used .He makes mention
that he will not have provisions for pallance.Bad bad

4.Engine to Main gear box attachment no give. I can see transient torque loads damaging the
P.T.O. or cracking the engines main gear case, Any twist,bending,or axial misalignment will reduce the service life of the Allison.

5.No fire wall,and any thing in the baggage compartment will wreak of exhaust fumes,Or worse
the composite body or cowl  will light off ,Nothing worse then roasting at 1000 ft,

6.fuel structure said to be molded composite under seat area,I hope its a crash resistant bladder.

7.multi blades to a point is good ,But remember the more blades the more drag in an auto,so like
a 500 or worse the pilot will need a window between his legs to see where hes going. And also the more blades you have the more parts too,and that adds to the cost,and in aerodynamics you will also cost you the unwanted interaction of shed wake vortices rolling under the closely following blade and the increased chance of vortex ring state with so many blades buzzing around above you.

8.Unrealistic performance values,with a steel tube frame,plastic covered body,its not a llama.

9.Nonstandard instrument layout  not good for a pilot too much flash,no function,like a Mini all
show no go.

10. smooth belly ,flow stagnation and random separation points will be hard to hover,like an A
star it will wallow and oscillate  in ground effect.

12. 222 like nacelles drag drag drag  and the rounded edges might induce dutch roll (need
fences)

13.Steel tube frame,Not required for a modern Helicopter.Too heavy for the true designer of
helicopters.( no steel in the 500 or 206 or CH-53 or other high performance Helicopter.)

14.Air flow around engine not uniform might lead to cracking on the hot end or ingestion of
exhaust gases .

15.composite seat area,not a design feature for crash force absourbtion,Once compromised it
will not protest the pilots from injuries,Might even add to the sevarity of injuries sustained.

16.If the hub is machined aluminum and not steel I fear a fretting type failure and blade
separation .(This was just a thought until confirmed by another source.)

17. Untried engine drivetraine combination/surging might be possible ,Ill grant them this one for
now.

18. no room between the rotors and tail boom. I can predict a strike and in flight breakup,Needs
more space.

19.stablizers too big.for desired pitch moment. will nose over in 1st stage of autorotation.adding
to boom strike.

20.Too short coupled needs more length on boom,will not have authority over the torque,

21.My wife (from China) doesn't like it.

So many designers just because they have disposable income think they have the winning
combination and copy a piece of junk and improve on it ,They still have a piece of junk,Its better
to start from scratch and fail then ,succeed with junk that may kill some poor S.O.B. because
good looks can kill.

Don /Rotermouse@<hidden>              These are my opinions.
 

--- DONALD HILLBERG
--- rotermouse@<hidden>



Helinut
12th Apr 2002, 11:59
I am not familiar with the type you mentioned, but in a way this does not matter if you talk about the general issues of kit helicopters. Talking generally and based on some experience with another "kit helicopter" IMHO you need to be very careful about helicopters that have not gone through the "normal" design, construction, flight testing and certification process. As a helicopter pilot, your life is very much in the hands of the engineers and test pilots who have contributed at all stages to the machine you are flying. The full blown certification process is time-consuming, expensive and appears sometimes tedious. However, you can have some faith that if you fly it within the envelope it won't bite or fall apart on you. You just do not know the pedigree of the beast if it is not certified.

The same is true of aeroplanes, but there are just that many more critical moving bits in a helicopter, so the issue is more important.

In the end, it depends how much you think your life is worth.

Dave Jackson
12th Apr 2002, 20:55
nucleus33

In support of Helinut's comments.

Experimental or kit helicopters are in a very different market from that of certified factory built helicopters. This distinction is about to become even greater in the United States. The upcoming intermediate category SportPilot/Aircraft (http://www.sportpilot.org/) is excluding helicopters, due to their complexities.

The Rinke (up to $300.000.00 US) and Rotermouse are competing at the top end of the experimental kit category; a category that starts at the bottom with a $90.00 set of plans. This is a market where many of the purchasers get more pleasure from building the craft then flying it. Therefore, one has to consider the depreciation and resale value of homebuilt aircraft, particularly the high priced ones.
_________________

A couple of comments related to your specific question.

1/ There is nothing wrong with using high strength, lightweight carbon composite in the fuselage, when the laminate includes some Kevlar or fiberglass to minimize any 'shattering' action of the carbon.

17/ At appears that the model of Allison engine to be used in the Rinke is a single shaft turbine. This means that all turbine powered homebuilt rotorcraft are using single shaft turbines or twin shaft that were only intended for intermittent duty.

The Rinke is a very attractive helicopter. Let's hope that its performance and reliability will match its aesthetics.

rotormatic
14th Apr 2002, 03:58
The Jag helicopter has someone with a lot of money for development behind the project....Review of the web site found it has not flown yet.

All of the information is preliminary, pending flight validation.

The allison engine details mentioned are inaccurate...they stated the C-18 engine can produce 420 horsepower...

It's take off rating at sea level during standard day conditions is 317 horsepower....running above that value will cause damage to the turbine...

Also, the allison is a free turbine engine, not a fixed shaft...

The placement of the engine inlet looks like a problem. Not much room for a proper bellmouth or inlet assembly, which may cause performance problems (low power, high engine temp), and vibration problems in the compressor due to improper airflow.

Other engine installation details that are not covered on the site:

a. Type of oil cooling system used. This engine has problems with oil coking in the turbine.

b. The fuel system is requires a minimum fuel flow to the engine driven pump to avoid air being introduced into the system. With the fuel tanks below the engine, a fuel boost system will be needed that will supply between 10 PSI and 25 PSI pressure to the engine driven fuel pump. Without a boosted fuel supply, a small amount of air in the fuel will put the fire out in this engine.

If someone is thinking of investing in this aircraft, they should wait until some good flight history is recorded, and review the installation of the engine before putting good hard money down on the kit.