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LSAs

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rgf(at)dcn.davis.ca.us
Guest

Posted: Sun Dec 02, 2007 5:53 am Post subject: LSAs

Speaking of LSAs....Chinese or  otherwise...Van's RV-12 got me to thinking.  That doesn't happen often and  when it does, I take advantage of it.

  

 I gotta think that the RV-12 could fly  faster than the LSA speed limit (120 kts) with maybe just a coarser pitched  prop.  If so, would it be legit to:

  

 - build or buy an LSA--say Van's--switch the  prop, and fly it out of the LSA class with your PP-ASEL and current  medical

 - then if you don't want to renew your  medical for some reason, simply switch the prop back again to be below 120  kts

  

 Can the same plane, with a minor alteration,  switch between LSA and not?

  

 Ralph Finch

   [quote][b]

kboatright1(at)comcast.ne
Guest

Posted: Sun Dec 02, 2007 8:07 am Post subject: LSAs

Bigger engine or a different prop, and the RV-12 probably would fly  faster than the LSA limit.  But, it wouldn't be an LSA at that  point.  If it is *ever* registered as nonconforming to the LSA rules, it  can never be put back into LSA.  

  

 Lots of Ercoupes, Aeroncas, etc. were LSA compliant as originally  delivered.  Unfortunately, they were modified with a variety of STC's, some  of which raised their gross weight above the LSA spec's.  And now, those  aircraft can't be recertified as LSA's, even if the owners uninstall the  STC's or decrease the aircraft's gross weight limit to LSA compliant  figures.

  

 It isn't perfectly logical, but that's the FAA and "rules by committee" for  you.

  

 KB

  

  

 [quote]   ---

mike109g6(at)insideconnec
Guest

Posted: Sun Dec 02, 2007 8:10 am Post subject: LSAs

Doesn't that open a can of worms!!!  LOL!  What a selling point  for Van's if applicable - multi-mission aircraft.  But I'm sure that there  are structural considerations in the design of the RV-12 that prevents Van's  from selling/advertising this approach, ie the plug-in wings, etc.   Interesting concept though.

 Mike H 9A/8A

 [quote]   ---

Bob Collins

Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota

Posted: Sun Dec 02, 2007 8:37 am Post subject: LSAs

It's one of those  questions that's fun to pose to Van, himself, just to be entertained by his  reaction. (g)

  

 do not  archive



   From: owner-rv-list-server(at)matronics.com  [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of mike  humphrey

Sent: Sunday, December 02, 2007 10:10 AM

To:  rv-list(at)matronics.com

Subject: Re: LSAs

 

 Doesn't that open a can of worms!!!  LOL!  What a selling point  for Van's if applicable - multi-mission aircraft.  But I'm sure that there  are structural considerations in the design of the RV-12 that prevents Van's  from selling/advertising this approach, ie the plug-in wings, etc.   Interesting concept though.

 Mike H 9A/8A

 [quote]   ---

_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/

tracy(at)rotaryaviation.c
Guest

Posted: Sun Dec 02, 2007 9:52 am Post subject: LSAs

I often hear this approach to speeding up airplanes and wonder where it comes from.  Assuming that the engine is equipped with a prop that does

  not allow the engine over- rev significantly to begin with (I doubt Vans would do this), a coarser pitched prop will only slow the engine down making

  less power and making the plane go slower, not faster.

  

 If this approach worked,  we would all be flying 300 mph RVs.

  

 Tracy Crook

 Rotary powered RV-4

 On Dec 2, 2007 8:49 AM, Ralph Finch <rgf(at)dcn.davis.ca.us (rgf(at)dcn.davis.ca.us)> wrote:

 [quote]  Speaking of LSAs....Chinese or otherwise...Van's RV-12 got me to thinking.  That doesn't happen often and when it does, I take advantage of it.

  

 I gotta think that the RV-12 could fly faster than the LSA speed limit (120 kts) with maybe just a coarser pitched prop.  If so, would it be legit to:

  

 - build or buy an LSA--say Van's--switch the prop, and fly it out of the LSA class with your PP-ASEL and current medical

 - then if you don't want to renew your medical for some reason, simply switch the prop back again to be below 120 kts

  

 Can the same plane, with a minor alteration, switch between LSA and not?

  

 Ralph Finch

 	  Quote: 	
		  

	


[b]

rgf(at)dcn.davis.ca.us
Guest

Posted: Sun Dec 02, 2007 10:36 am Post subject: LSAs

I don't want to start a flame war, but this statement  is not true for many cases...my Alon Aircoupe, for instance, which definitely  gains 6-8 mph with a cruise prop (52") over a climb prop (48").  I have  both and have seen this several times.  If changing pitch didn't help top  or cruise speeds, why have constant speed (variable pitch) props on the  higher performance aircraft.

  

 I'm guessing--and it is a guess at this point--that the  RV-12, like Van's other aircraft, is very low drag and that he's putting on a  relatively flat pitch prop to keep the speed down.  If true this will  translate into a better climb rate.  And if true, a simple prop change  could allow speeds above the LSA limit.  Voila, a dual-mission aircraft for  cheap.  



 [quote]         From: owner-rv-list-server(at)matronics.com    [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Tracy    Crook

Sent: Sunday, December 02, 2007 9:51 AM

To:    rv-list(at)matronics.com

Subject: Re: RV-List:  LSAs

   

   I often hear this approach to speeding up airplanes and wonder where it    comes from.  Assuming that the engine is equipped with a prop that    does

    not allow the engine over- rev significantly to begin    with (I doubt Vans would do this), a coarser pitched prop will only    slow the engine down making

    less power and making the plane go slower, not faster.

    

   If this approach worked,  we would all be flying 300 mph RVs.

    

   Tracy Crook

   Rotary powered RV-4



[b]

tracy(at)rotaryaviation.c
Guest

Posted: Sun Dec 02, 2007 3:01 pm Post subject: LSAs

I Love a good technical discussion and I never perceive disagreement as flame and hope others feel the same.  

  

 My contention was based on the statement "Assuming that the engine is equipped with a prop that does not allow the engine to over- rev significantly to begin with".  

  

  If the speed of an airplane is limited by intentionally installing a lower pitch prop, it will almost invariably overspeed the engine in level flight at full throttle.  Did your Aircoupe do this?  This is sometimes done (to improve climb performance) but it requires the pilot to back off the throttle in level flight to keep the engine below redline.  I don't know the details of the LSA regs but if they allow you meet the top speed requirement by simply backing off the throttle, that would be a loophole big enough fly a 747 through.  I doubt even a government agency could be that daft. 

  

 I should probably have added one other condition, that being "all else being equal".  All else in this case would include prop efficiency.  If you unbolt a lousy or unsuitable prop and install a very good one (I have owned both kind  :>) the increase in performance could be due to that increase in efficiency and not related to to the pitch.  BTW, 48" prop? Wow, I'm not surprised that the 52" outperformed it in almost every way.   Maybe I'm thinking of a different Aircoupe.  (one with C85 engine?)  A 48" prop is way too short for the one I'm familiar with. 



To stretch my credibility even further,  all else being equal, a lower pitch prop will often fly faster than the so-called cruise prop  (if you don't mind over-reving the engine).   Engines will make more HP at higher rpm and it takes HP to go faster.  The tach reading on the Formula planes at Reno would give most pilots a coronary.  If they installed a higher pitch prop to bring revs down, I guarantee you they would go slower.  

  

 More sacred cow slaughter:   Constant Speed props don't make planes go faster.  They just eliminate the compromise between climb and cruise props.   They also allow you to run the engine in it's best efficiency spot for most flight conditions.  If takeoff & climb performance were not a factor, a fixed pitch prop (designed for max speed) would go faster than a CS prop. 

  

 Tracy Crook  (ducking bovine projectiles)

  

  

 On Dec 2, 2007 1:35 PM, Ralph Finch <rgf(at)dcn.davis.ca.us (rgf(at)dcn.davis.ca.us)> wrote:

 [quote]  I don't want to start a flame war, but this statement is not true for many cases...my Alon Aircoupe, for instance, which definitely gains 6-8 mph with a cruise prop (52") over a climb prop (48").  I have both and have seen this several times.  If changing pitch didn't help top or cruise speeds, why have constant speed (variable pitch) props on the higher performance aircraft. 

  

 I'm guessing--and it is a guess at this point--that the RV-12, like Van's other aircraft, is very low drag and that he's putting on a relatively flat pitch prop to keep the speed down.  If true this will translate into a better climb rate.  And if true, a simple prop change could allow speeds above the LSA limit.  Voila, a dual-mission aircraft for cheap.   



  	  Quote: 	
		     From: owner-rv-list-server(at)matronics.com (owner-rv-list-server(at)matronics.com) [mailto: owner-rv-list-server(at)matronics.com (owner-rv-list-server(at)matronics.com)] On Behalf Of Tracy Crook

Sent: Sunday, December 02, 2007 9:51 AM  

To: rv-list(at)matronics.com (rv-list(at)matronics.com)

Subject: Re: LSAs



  

 I often hear this approach to speeding up airplanes and wonder where it comes from.  Assuming that the engine is equipped with a prop that does

  not allow the engine over- rev significantly to begin with (I doubt Vans would do this), a coarser pitched prop will only slow the engine down making

  less power and making the plane go slower, not faster.

  

 If this approach worked,  we would all be flying 300 mph RVs.

  

 Tracy Crook

 Rotary powered RV-4



	


[b]

acepilot(at)bloomer.net
Guest

Posted: Sun Dec 02, 2007 3:11 pm Post subject: LSAs

I believe he was referring to 48" of pitch, not prop diameter 



Scott

http://corbenflyer.tripod.com/

Gotta Fly or Gonna Die

Building RV-4 (Super Slow Build Version)



Tracy Crook wrote:



 	  Quote: 	
		  

  

  BTW, 48" prop? Wow, I'm not surprised that the 52" outperformed it in 

 almost every way.   Maybe I'm thinking of a different Aircoupe.  (one 

 with C85 engine?)  A 48" prop is way too short for the one I'm 

 familiar with.

mrobert569(at)hotmail.com
Guest

Posted: Mon Dec 03, 2007 9:40 am Post subject: LSAs

Ralph,

  

 It depends on which category you certificate it in.  If it is in the experimental amateur-built category then it is no problem.  But if you were able to get it certificated in the Light-sport category then you would have a problem.  In this case I don't think you will have to worry as I don't think it will qualify for the Light-Sport category, just the amateur-built category.

  

 Mike Robertson

 Das Fed



  	  Quote: 	
		    From: rgf(at)dcn.davis.ca.us

To: rv-list(at)matronics.com

Subject: RV-List: LSAs

Date: Sun, 2 Dec 2007 05:49:57 -0800



  Speaking of LSAs....Chinese or otherwise...Van's RV-12 got me to thinking.  That doesn't happen often and when it does, I take advantage of it.

  

 I gotta think that the RV-12 could fly faster than the LSA speed limit (120 kts) with maybe just a coarser pitched prop.  If so, would it be legit to:

  

 - build or buy an LSA--say Van's--switch the prop, and fly it out of the LSA class with your PP-ASEL and current medical

 - then if you don't want to renew your medical for some reason, simply switch the prop back again to be below 120 kts

  

 Can the same plane, with a minor alteration, switch between LSA and not?

  

 Ralph Finch

 	  Quote: 	
		  



blank>http://www.matronics.com/contribution

t=_blank>http://www.matronics.com/Navigator?RV-List

p://forums.matronics.com



	
	
You keep typing, we keep giving. Download Messenger and join the i’m Initiative now. Join in!  [quote][b]

tracy(at)rotaryaviation.c
Guest

Posted: Mon Dec 03, 2007 10:19 am Post subject: LSAs

D'oh,  You're probably right Scott.  I still stand by the rest of my blasphemies though : )

  

 Tracy

 On Dec 2, 2007 6:10 PM, Scott <acepilot(at)bloomer.net (acepilot(at)bloomer.net)> wrote:

 [quote]--> RV-List message posted by: Scott <acepilot(at)bloomer.net (acepilot(at)bloomer.net) >



I believe he was referring to 48" of pitch, not prop diameter 



Scott

http://corbenflyer.tripod.com/

Gotta Fly or Gonna Die 

Building RV-4 (Super Slow Build Version)

 

Tracy Crook wrote:



 	  Quote: 	
		  



  BTW, 48" prop? Wow, I'm not surprised that the 52" outperformed it in

 almost every way.   Maybe I'm thinking of a different Aircoupe.  (one 

 with C85 engine?)  A 48" prop is way too short for the one I'm

 familiar with.






	




  

 



[b]

acepilot(at)bloomer.net
Guest

Posted: Mon Dec 03, 2007 2:20 pm Post subject: LSAs

Not to worry!  I have days like that too!  



Scott

http://corbenflyer.tripod.com/

Gotta Fly or Gonna Die

Building RV-4 (Super Slow Build Version)



Tracy Crook wrote:



 	  Quote: 	
		   D'oh,  You're probably right Scott.  I still stand by the rest of 

 my blasphemies though : )

  

 Tracy



 On Dec 2, 2007 6:10 PM, Scott <acepilot(at)bloomer.net 

 <mailto:acepilot(at)bloomer.net>> wrote:



     

     <mailto:acepilot(at)bloomer.net> >



     I believe he was referring to 48" of pitch, not prop diameter 



     Scott

     http://corbenflyer.tripod.com/

     Gotta Fly or Gonna Die

     Building RV-4 (Super Slow Build Version)



     Tracy Crook wrote:



     >

     >

     >  BTW, 48" prop? Wow, I'm not surprised that the 52" outperformed

     it in

     > almost every way.   Maybe I'm thinking of a different Aircoupe.

      (one

     > with C85 engine?)  A 48" prop is way too short for the one I'm

     > familiar with.

     >

     >

     >

     >

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