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Prop selection

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scottarden(at)cox.net
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Posted: Tue Mar 11, 2008 7:08 am Post subject: Prop selection

Guys!

I'm getting close to buying a Lightning kit.  I'm not anywhere near being an aeronautical engineer, and am learning a TON from you guys!  I have a question that I haven't seen addressed here.  The lightning website calls for a fixed pitch prop.  Would a cockpit adjustable/constant speed prop be applicable to this airframe and engine.  I know that an oil pressure driven CS will not work with this engine, but there seem to be some good electric alternatives.  I talked to the guys at Ivoprop and they said their inflight adjustable with the constant speed controller would work great for this application.  I know I'm listening to sales-speak, but please educate me.  It seems like a constant speed might give great take-off performance and at the same time give some better top end.

Buz?  Rich? Nick? Jim?

--

Have a blessed day!

Scott C. Arden

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info(at)flylightning.net
Guest

Posted: Tue Mar 11, 2008 8:16 am Post subject: Prop selection

Scott,



I would not go with the IVO, although I have not flown it so maybe I don't

know but I have seen them come apart and have flown the airmaster which is

similar with no luck in this application. The wood 62 FK 58 is a great prop

for the aircraft for all around performance...



Nick



--

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scottarden(at)cox.net
Guest

Posted: Tue Mar 11, 2008 8:44 am Post subject: Prop selection

Thanks, Nick..

Rather than asking about specific products, I'm really inquiring about the concept of a constant speed with this airframe/engine.  I know there are several manufacturers out there who make electric CS props and I  wouldn't use one that doesn't have an impecable safety record (i.e. NO structural failures),  I certainly don't want to suddenly find myself in a glider that used to be a powered airplane!  I don't think that the liklihood of finding a guy like in Jim's video is too promising!!

--

Have a blessed day!

Scott C. Arden



---- flylightning <info(at)flylightning.net> wrote: 

[quote] 

 

 Scott,

 

 I would not go with the IVO, although I have not flown it so maybe I don't

 know but I have seen them come apart and have flown the airmaster which is

 similar with no luck in this application. The wood 62 FK 58 is a great prop

 for the aircraft for all around performance...

 

 Nick

 

 --

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Kayberg(at)aol.com
Guest

Posted: Tue Mar 11, 2008 9:27 am Post subject: Prop selection

In a message dated 3/11/2008 11:09:58 A.M. Eastern Daylight Time,  scottarden(at)cox.net writes:

  	  Quote: 	
		  Guys!

I'm getting close to buying a Lightning kit.  I'm not    anywhere near being an aeronautical engineer, and am learning a TON from you    guys!  I have a question that I haven't seen addressed here.  The    lightning website calls for a fixed pitch prop.  Would a cockpit    adjustable/constant speed prop be applicable to this airframe and    engine.  I know that an oil pressure driven CS will not work with this    engine, but there seem to be some good electric alternatives.  I talked    to the guys at Ivoprop and they said their inflight adjustable with the    constant speed controller would work great for this application.  I know    I'm listening to sales-speak, but please educate me.  It seems like a    constant speed might give great take-off performance and at the same time give    some better top end.

Buz?  Rich? Nick?  Jim?

	


 

  

 I am not one of those 4, but I have worked with IVO props.

  

 I think they work great on Rotax geared engines and can supply high thrust  at low speeds, particularly the 3 blade.   But they dont handle power  pulses real well as in a direct drive.   Also they have a top speed  peak.

  

 The two-blade Sensinich adjustable  has supplied greater speed  in one application I am familiar with, where it replaced a 3 blade IVO  inflight adjust.

  

 The IVO inflight adjust is a decent unit, but only on a geared  Rotax.  The brushes for the blade pitch motor seem to have a short  life.

  

 Given the extra expense for a really decent inflight adjust, I dont think  it is worth it.  The guys at Titan have an electric 4 blade inflight  adjust to go with their geared engines.   If memory serves, that  prop costs about $20,000!!!  The european designs are in the same price  range.

  

 Another consideration is a prop strike.  With a wood prop, it is not  likely to do much damage to the engine in a "gopher hole"  strike.  A thousand bucks or less and you are flying again.  Not  so with an inflight.

  

 For some reason it is becoming increasingly popular to hang every gizmo  possible on the Lightning airframe.  It takes longer to wire up the  TV's, radios and gizmos than it does to assemble the airframe!  Some refuse  to fly with less than two GPS's!!!     Not only does it  increase the cost, weight and complexity, but has a performance price tag  also.   

  

 I suspect Inflight adjust doesn't make a plane go faster, it just lets you  decrease the RPMs for the same speeds.  It can give more ground thrust  because of a flatter bite.   The Lightning gets off the ground and  climbs just fine even with a "cruise" prop.

  

 Just my thoughts

  

 doug koenigsberg



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N1BZRich(at)aol.com
Guest

Posted: Tue Mar 11, 2008 11:11 am Post subject: Prop selection

In a message dated 3/11/2008 11:09:58 A.M. Eastern Daylight Time,  scottarden(at)cox.net writes:

  	  Quote: 	
		  said    their inflight adjustable with the constant speed controller would work great    for this application. 	


 

 Scott,

     Doug pretty much covered my thoughts when he said  that the inflight adjustable is not any faster if you have the right fixed pitch  cruise prop.  With an adjustable prop you may get a slightly  shorter takeoff and slightly more rate of climb, but the cost of that in my book  is not worth it.  If you build your Lightning light the takeoff roll will  be relatively short even with a cruise prop.  Even at gross on a hot day, I  never see a takeoff roll much over 600 to 700 feet and the rate of climb is  still 1000 fpm or better.  Most of my TO rolls are around 500 feet or  less.  If you want to operate out of a short strip with steep  approaches, then don't use a cruise prop.

      Second thought, don't confuse an inflight  adjustable with a constant speed.  They are two different things.  A  true constant speed must have some sort of governor (normally operated by engine  oil) that keeps the engine rpm constant regardless of what you do with the nose  of the airplane.  It is constantly varying the pitch of the prop to achieve  this.  An inflight adjustable only allows you to change the pitch from the  cockpit, and it uses an electric motor to change the pitch.  The prop  blades then stay where you set them until you re-adjust.  So once you set  the pitch it stays there and the rpm will vary as you raise or lower  the nose of the airplane - just like a fixed pitch.  If some company  has an electric governor to make a true constant speed electric prop, then I  suspect it would be very costly and heavy.  I have not seen or read about  this feature.  

     Sensenich has been showing an electric in flight  adjustable hub for the last year or so at OSH and LAL.  Don't know when it  might be available, but I seem to remember that it is a $6,000.00 option.   Not worth it in my book.  

     I also agree completely with Doug's thoughts of  keeping your homebuilt airplane simple.  In the long run you will have  fewer problems and a much cheaper airplane to build and maintain.  Remember  that the cost that you pay for builder's assistance programs is based on the  basic airplane.  When you add complicated systems you greatly add to the  build time and you should expect to pay for that extra time.  Heck, even  fitting wheel pants and gear leg fairings add a lot of time.  It took me  over a week to do mine, but I was kind of doing it the first time.  

     One other thought and I will put down my hammer -  the builders assist programs have certain avionics and equipment that they are  familiar with because they have successfully used those many time.  They  can easily wire them and they will work the first time.  My suggestion is  to go with their suggestion as to which radio, X-ponder, EIS and EFIS  to use if you are going the fancy panel route.  That will make their job  easier and should take less time - therefore less $s for you.  

 Blue Skies,

 Buz Rich





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