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Spinner design!


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while surinf the interweb thingo we have here, i cam across this beautiful aircraft.




apart from the looks, i am very intrigued by the design of the spinner!!






from what i can guess, the small fins on the spinner are obviously an


aerodynamic air, and work similar to a strake in front of the leading


edge of a wing or horizontal stabiliser.


is it designed to improve low forward speed and high prop RPM or course


pitch situations, or aid in high speed performance????? and if


that be the case, why do the smaller fins appear to work in the


opposite direction to the prob blades themselves??


i think its interesting indeed.... what do other think?





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Hi Rob,


In the bottom pic it appears to me that the thingamejig on front of the spinner is not rotating as the prop spins, but maybe is driven by air passing over it, wind milling like the gadgets in the background do. Like you I am now very curious, hope someone has an answer.Perhaps a RAT ;).gif.





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i have also noted the design of the cowlings, as you can probably


tell, its powered by a Jabiru 2200, but the cooling setup is


interesting! there doesnt appear to be an opening at the bottom


of the nose apart from engine combustion exhausts, and it looks


like the ram air cooling exits via the vanes on the top surface of the




if the spinner blades are a RAT or similar, then wouldnt the nose


section of the spinner spin the opposite direction to the prop spinner




come to think of it, this could be used to provide elctrical


power, and the rate of spin of the 2 parts of the spinner would make an


efficient generator??? hmmmmm now im intrigued....




I found a little more ont he spinner design...




The finned part of the


spinner spins independantly from the aft protion. It's a control for


the constant speed - its spinning is a function of the airplane's


speed. As the airplane speeds up it spins faster. This is then coupled


to a prop hub mechanism which controls the blade angle and as such,


this is how you get a self contained constant speed prop - no cockpit


controls. Avia manufacures a similar unit for certified aircraft. The


system can be electric or hydraulic - I'm not sure which one this is





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Guest Prometheus

I'm not sure I like the fact there's no RPM control in the cockpit! smiley5.gif


Other than that it's a beautiful lloking aircraft. Nice clean lines and the wing looks as though it was inspired by Supermarine's hey days!


Nice, now if only it was a two seater! Prometheus



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Guest malarcon

As an avid reader of german flying magazines I just read an article on that prop. The website of the manufacturer is:




The spinner cap rotates against the prop rotation as the airflow


windmills it. This gives feedback about the airspeed as well as


generating the electricity for a small electronics unit that controls


the propeller blade pitch. So as mentioned by Ultralights it is


self contained. The manufacturers have preprogrammed 16 pitch/airspeed


curves of which you can choose one (on ground) that best suites the


aircraft. They seem to be very helpfull when setting up the prop for


the individual needs of specific airframes. In low throttle the pitch


does go to fine,


which helps in steeper descends but not with long "feathered" glides.


The article did gush quite a bit and the very interesting part is that


the prop offers constant speed performance at a weight bellow your


average wood fixed pitch as the blades are carbon fibre. If you ask me


the price is quite fine too but I have lent the mag and can't


remember the exact figure. The prop is available for the Jab engines


and they are working on the Rotaxes. If I was "in the market" I'd


consider it a very interesting choice.


As far as no RPM control goes. Your average 747-400 does not have one


(vane pitch in their case, which is variable) and they seem to manage


fine. There is a strong trend to "one lever power" (Cirrus, Dimond


Star...), which is sensible in my opinion as any FADEC can do a much


better job at setting up the engine and prop than most pilots.


I'm not affiliated with the folks, just repeating the article and my opinion. :)





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A system like this using the front part of a spinner to supply power to a variable prop was used during WWII by the Germans on various aircraft, usually powered by an Argus engine.


I'm not sure of the exact history, but after the war, this system was available from the AVIA company in Czechoslovakia.


This system used the front vane to drive a small hydraulic pump to automatically adjust the pitch.


It can be found on WWII planes like the Me 108, the Feisler Storch and FW 189.


After the war it was popular on Eastern Block aircraft using the Lom engines from manufacturers like Zlin, Meta-Sokal and Avia.





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Guest Prometheus
...As far as no RPM control goes. Your average 747-400 does not have one (vane pitch in their case, which is variable) and they seem to manage fine. There is a strong trend to "one lever power" (Cirrus, Dimond Star...), which is sensible in my opinion as any FADEC can do a much better job at setting up the engine and prop than most pilots.

I'm not affiliated with the folks, just repeating the article and my opinion. :)

Excuse my ignorance with thissmiley9.gif... so rather than having a throttle as such, the one control would be to vary the pitch. The spinner would then increase or decreace power as required... Have I got it right?



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Guest malarcon

In this particular design you just have the engine throttle. The


propeller pitch is set by the electronics within the spinner. No cable,


nor wireless connection exists between the spinner and the outside


world, thus the weight benefit. When I get the magazine back I can scan


some pictures of the disassambled spinner and post them if someone


wishes. I have heared that the designers of this system worked on




an Me108 that is owned by Lufthansa and they got the idea there.


In the case of the Cirrus or the Diamond Star, they are equiped


with standard hydraulic constant speed props, but you get no


lever for the RPM. An electronic unit selects the RPM according to the


manifold pressure and throttle lever position (full forward = finest


pitch for take off and go around, bellow hat cruise pitch settings and


if I remember correctly finest pitch on low throttle settings again)


The vanes on a modern turbofan are also controled electronically


acording to throttle position but if I remember correctly a great heap


of other engine parameters are taken into account here.


The basic idea is the same as an automatic car, you use the throttle


the car finds its own gear, the airplane the prop pitch. Now in an


airplane this makes much more sense than in a car as you don't have


changing slopes (you get to choose your slope and usually keep it


steady), starting and stopping at trafic lights and simmilar problems


and you don't have to worry about the clutch. For a certain


aircraft/engine/prop combo there is an ideal pitch setting for every


manifold pressure and the electronics take care of matching these.


I hope this answers your question Dave. ;)


Another nice system for ULs is the woodcomp VARIA (Chech Republic)


mounted on the airplane you can see on my "avatar" it is a very simple


mechanic pitch change that is very light and much more maintenance


friendly than any hydraulic or external elecric system I've seen. The


only problem is that the handling is not so straight foward as the RPM


change with your flight situation as they do with fixed pitch prop and


the pitch change have an effect on your manifold pressure. So you have


to keep the plane steady to adjust the RPM. And then there is a nice


little dance of throttle adjustment, pitch then a bit of throttle again


maybe a hint of pitch, back to the throttle :confused:..... After a while you get a hang of it and you don't need so much playing. The performance is great though.



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I always thought that the prop pitch should be such as to keep the R.P.M. low and throttle at max manifold pressure for cruise and descent to reduce fuel consumption. For takeoff you need max R.P.M. to get max power and throttle usually has to be reduced before R.P.M. to avoid overboosting which is like driving a car too slow in a high gear. For landing it would be best to have min R.P.M. but the risk of needing full power for a go around is the reason for using full fine pitch.


Another reason for using coarse pitch when possible is to reduce noise.



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Guest malarcon

The idea for economical cruise is to get the most power of the engine and turn that into thrust.


For example Rotax recomends the following pairs for the 914:


31inHg and 5000RPM = 75% power


29inHg and 4800RPM = 65% power


28inHg and 4300RPM = 55% power


Now of course the airframe and propeller will have an impact on the


best combination and on the fuel flow result, but these handbook values


are a good reference to start working with.


Basically a higher pitch will allow a more economical flight but there


is an optimal point and very low RPM combined with high manifold


pressure is a sure fire way of ruining an engine and is not economical


as the engine does not run in an optimal state. That is why you


should always lower throttle first and just then lower pitch and always


turn pitch to fine and then increase throttle.


PHEW I guess there is a reason the yanks call these "complex aircraft" and want in-flight adjustable props out of LSAs.;)


Now a self adjusting system could even make the hardest rule maker


soften up..... Oh wait actually "one levers" are not allowed for twin


engine endorsement training in the US as it is too simple and won't


have students sweating enough. I guess you can't get it right.:)



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