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more prop test info

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N1BZRich(at)AOL.COM
Guest

Posted: Sun Mar 22, 2009 7:48 pm Post subject: more prop test info

All,

     Some time ago I sent out a report on the  results of the prop testing I have been doing on N31BZ with the Sensenich  62FK60.  (remember BZ has the older solid lifter engine)  Those emails  listed the true airspeeds vs. RPMs that I was seeing.  As a follow up to  that message I have been doing some additional testing the last several days to  come up with some fuel flow numbers with the new prop.  Most of you that  have been on the list for a while know that my cross country technique is to  set a fuel flow (not an rpm) and accept the airspeed and  rpm that the fuel flow gives me at the altitude I am using for the trip.   Since I am planning another trip to SYI early this coming week, I figured I had  better get at least some "ball park" fuel usage numbers before I make this next  trip.

     On cross country flights I normally cruise at an  altitude that does two things for me - I am looking for lowest headwinds  and smooth flight conditions.  If there is a tail wind, I go up high  to take advantage of that, often cruising as high as 14,500 when west bound  (yes, I have a small O2 bottle).  Normally, I seem to end up in the  altitude band between say 6 to 12 thousand feet, so that is where I have  been doing most of the testing the last few days.  Oh, one other thing, the  OATs have been running slightly cooler than a standard day.  For example  density altitude has been about 300 below indicated altitude.  

     Below are the results I have seen during  recent flights over the last few days:

 -Since I normally set 6  gph I did a lot of those test.  As it  turns out, 6 gph seems to give me in the neighborhood of 162 to 165 mph  true airspeed (weight makes a difference).  I should also note  that I tried to do most of the test when I had the tanks full (except for  that burned during climb out) but with only me and approx 30 pounds in  the baggage area (31BZ is probably around a 1200 lb airplane with that  load).  

 -However, I noticed something interesting (with the prop and set up I am  now using) when I pulled the fuel flow back below 6 gph.  It appears  that:

 5.5 gph gives 155 mph, 

 5.0 gph = 150, 

 4.5 gph = 145, 

 4.0 gph = 140,

 and 3.5 gph was right at 135 mph.  I saw no  reason to go slower than that.   

     If these numbers prove fairly accurate during  actual cross country flights, that works out to over a 1000 mile range flying at  135 mph tas - but who wants to go that slow.  

     I just thought the kind of linear relationship of  FF to MPH was interesting.  Of course, the time spend at the various fuel  flows was just long enough to let the mph settle down and things could  be different when I actually make the trip to SYI (probably this Tuesday).   

     Anyway, as normal, I will provide the data  for that flight after I get there and find the time to figure it all out  more accurately.  

 Blue Skies,

 Buz  

 Feeling the pinch at the grocery store?  Make dinner for $10 or less.

  [quote][b]

pennington(at)q.com
Guest

Posted: Mon Mar 23, 2009 4:03 am Post subject: more prop test info

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Good morning Buz

  

 What rpm's were you turning at those TAS?

  

 Thanks for the info. Happy days.

  

 Gary Pennington

 [quote]   ---

N1BZRich(at)aol.com
Guest

Posted: Mon Mar 23, 2009 4:29 am Post subject: more prop test info

Sorry, Gary, I didn't record that data as I had sent that out before and  also I don't fly cross country using the RPM technique.  I just set  the fuel flow I want in the cruise portion of the flight and accept whatever  speed and RPM that gives me.  By doing that I always know how much fuel I  will arrive with (with the current winds)  and can adjust the arrival fuel  by playing with the throttle.  But as I recall, 6 GPH is about 2880 and 162  MPH TAS, and 2750 is about 150.  When I get the time I can look  it up  and send it to you, but busy day today.  Besides getting ready to go to SYI  tomorrow, I am briefing a kinder garden and local school at the airport, and  hopefully getting some interest in aviation for the future.  The kids  really enjoy the pedal planes I have built and also sitting in the Esqual  for photos.  I take one of my old Air Force helmets for them to wear when  sitting in the pedal P-51 and leather helmet and goggles for the pedal  Pitts.  The teachers, kids and Moms love it and it is good publicity for  the local airport.  

 Blue Skies,

 Buz

  

 Feeling the pinch at the grocery store?  Make dinner for $10 or less.

  [quote][b]

pennington(at)q.com
Guest

Posted: Mon Mar 23, 2009 2:21 pm Post subject: more prop test info

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Thank you Buz. Very cool with the kids.

  

 Have a great flight.

 Gary

 [quote]   ---

selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Mon Mar 23, 2009 4:02 pm Post subject: Re: more prop test info

Hi Buz,



I'd really like to see these numbers with RPM and manifold pressure information. With the Bing the only control you have over mixture is via the airflow through the carby, set by the revs, so those numbers help to understand what regieme the engine is operating in.    The manifold pressures help to understand this a little more.



To my mind, the fuel flow figures in isolation are very little help in understanding what is going on in the engine and one needs an appreciation of that to make valid propeller comparisons.



Cheers,  Selwyn

_________________
Cheers, Selwyn
Kit 66 VH-ELZ

N1BZRich(at)AOL.COM
Guest

Posted: Mon Mar 23, 2009 4:37 pm Post subject: more prop test info

In a message dated 3/23/2009 8:05:16 P.M. Eastern Daylight Time,  selwyn(at)ellisworks.com.au writes:

  	  Quote: 	
		  I'd    really like to see these numbers with RPM and manifold pressure    information. 	


 

 OK, Selwyn, I do have manifold pressure (MP), so can eventually get that  for you.  Currently I don't pay that much attention to MP (fixed pitch  prop) and I got it installed too late to be much help during the initial 40 hour  test phase.  I ordered the MP set up early on, but there was a  delay in getting it to me.  I wanted to use it to help with the % horse  power charts, but I was about done with the phase one testing before I got it  installed.  I guess I just have been too busy to do much with it since  then.  But as I said, I will get some info for you if you promise to write  something up about it and the Bing adjustments for the newsletter.  Just  keep bugging me about it until I get it done.

 Buz

 Feeling the pinch at the grocery store?  Make dinner for $10 or less.

  [quote][b]

selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Tue Mar 24, 2009 12:54 am Post subject: Re: more prop test info

Hi Buz,



I'll be interested to see that as I am sure will others.  There is a school of thought going around which says that the coarser pitch props are too coarse and the engine is running at too high a manifold pressure for the revs.  One consequence of that would be that the thing is running on lean mixture at high power settings, not necessarily a good thing.  I appreciate you can't actually do much about it with a fixed pitch prop (except change the prop )  but it would be nice to know so we could operate the thing in the best way available.



Of course, if we had a decent carby with a mixture control then we would be able to do something about it wouldn't we.  That's on my list of possibles once the warranty expires.



I'm getting towards where I can start to at least think about flying mine so I'm keen to gather all the preliminary info possible.  Another two or three months and we may be getting close.

_________________
Cheers, Selwyn
Kit 66 VH-ELZ

pete(at)flylightning.net
Guest

Posted: Tue Mar 24, 2009 5:17 am Post subject: more prop test info

Actually Selwyn, more prop pitch will result in a richer mixture not leaner.



Pete



--

jeynon2

Joined: 25 Oct 2007
Posts: 24
Location: Southern Illinois

Posted: Tue Mar 24, 2009 7:52 am Post subject: Re: more prop test info

So Buz,  if my interpolation skills are up to par, you could shut off your fuel altogether and cruise all day at 100 mph.    



John Eynon

Lightning kit #53

checkpoint2(at)comcast.ne
Guest

Posted: Tue Mar 24, 2009 11:04 am Post subject: more prop test info

I would like to check the manifold pressure also. I will have a manifold pressure gage and will see just how hard my Sensenich  

Ground adjustable prop is working at given airspeeds and rpm. Bob Haas N330BH.  

         

  

From: owner-lightning-list-server(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of N1BZRich(at)aol.com

 Sent: Monday, March 23, 2009 8:37 PM

 To: lightning-list(at)matronics.com

 Subject: Re: Re: more prop test info  

  

       

In a message dated 3/23/2009 8:05:16 P.M. Eastern Daylight Time, selwyn(at)ellisworks.com.au writes:  

   	  Quote: 	
		    

I'd really like to see these numbers with RPM and manifold pressure information.  	
  

    

OK, Selwyn, I do have manifold pressure (MP), so can eventually get that for you.  Currently I don't pay that much attention to MP (fixed pitch prop) and I got it installed too late to be much help during the initial 40 hour test phase.  I ordered the MP set up early on, but there was a delay in getting it to me.  I wanted to use it to help with the % horse power charts, but I was about done with the phase one testing before I got it installed.  I guess I just have been too busy to do much with it since then.  But as I said, I will get some info for you if you promise to write something up about it and the Bing adjustments for the newsletter.  Just keep bugging me about it until I get it done.  

    

Buz  

  

       

  

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checkpoint2(at)comcast.ne
Guest

Posted: Tue Mar 24, 2009 11:17 am Post subject: more prop test info

I concur, but if you have an adjustable prop one can manage the

engine

Some what with the Bing. Bob Haas.



--

selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Tue Mar 24, 2009 4:23 pm Post subject: Re: more prop test info

 	  pete(at)flylightning.net wrote: 	
		  Actually Selwyn, more prop pitch will result in a richer mixture not leaner.



Pete



-- 	




Hi Pete,



Sorry, I don't follow that one.  



My understanding is that what will set the mixture is a combination of throttle opening and engine revs.  Engine revs is the critical thing because it affects the flow through the carby and thence the needle position which is what regulates the mixture.  The profile of the needle has to match the operating rev band.  



From that, if you imagine an engine with a variable pitch prop and you run it with a wide open throttle and the thing is running somewhere near max revs, the needle will be right out and it will be running rich mixture with most of the needle profiles we are likely to use.  If we then start winding in pitch the revs will come back as we load the engine and somewhere a little under 3000 RPM the mixture will start to lean off as the flow through the carby throat decreases and the needle begins to descend.  If we keep winding in pitch we will end up at 2850 cruise revs, wide open throttle and a nice lean cruise mixture, high manifold pressure, probably good cruise performance but an engine waiting to go bang.



That's my theory of how the Bing works.  I would be very pleased to see debate from the experts.

_________________
Cheers, Selwyn
Kit 66 VH-ELZ

pete(at)flylightning.net
Guest

Posted: Wed Mar 25, 2009 5:24 am Post subject: more prop test info

We have not used an in flight adjustable prop but many times have set and

adjusted Sensenich Ground Adjustable props.  The more pitch that we put in

it the richer the resulting mixture.  Don't forget that the vacuum at the

top of the diaphragm is generated upstream from the throttle butterfly.  The

more open the butterfly (throttle) the more vacuum the top side of the

diaphragm will see and the higher the needle will ride causing a richer

mixture.  Two of the other four forces that affect mixture are more directly

related to airflow through the carb.  The other two are related to

atmospheric pressure at the carb.



Pete



--

N1BZRich(at)AOL.COM
Guest

Posted: Wed Mar 25, 2009 6:03 pm Post subject: more prop test info

In a message dated 3/24/2009 11:55:16 A.M. Eastern Daylight Time,  jeynon2(at)verizon.net writes:

  	  Quote: 	
		  So    Buz,  if my interpolation skills are up to par, you could shut off your    fuel altogether and cruise all day at 100 mph. 	


 

 Absolutely brilliant, John.  I wish I had thought of that.  Sure  would lower the cost of flying.  

 Buz

 Feeling the pinch at the grocery store?  Make dinner for $10 or less.

  [quote][b]

N1BZRich(at)aol.com
Guest

Posted: Thu Mar 26, 2009 4:33 am Post subject: more prop test info

Hi Selwyn,

     Just wanted to know if the manifold pressure data  in my last email was helpful.  Let me know what data points you would like  and I will get those to you the next time I take my bird up. 

 Blue Skies,

 Buz

 Feeling the pinch at the grocery store?  Make dinner for $10 or less.

  [quote][b]

selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Thu Mar 26, 2009 4:38 pm Post subject: Re: more prop test info

Hi Buz,



Yes it is, that's exactly the sort of info that I was talking about.  I don't want to turn your life into one long test session but a similar set of numbers at one or two different fuel flows would be the bees knees.



I will provide a similar set for mine when I get it flying, in two or three months (says he hopefully).  I just made the decision to go with a glass cockpit so I'll have the instrumentation to collect the figures.



I really enjoy the other information you include on how you fly your bird.  It is all good stuff to think about.

_________________
Cheers, Selwyn
Kit 66 VH-ELZ

N1BZRich(at)aol.com
Guest

Posted: Thu Mar 26, 2009 6:43 pm Post subject: more prop test info

In a message dated 3/26/2009 8:41:11 P.M. Eastern Daylight Time,  selwyn(at)ellisworks.com.au writes:

  	  Quote: 	
		  a    similar set of numbers at one or two different fuel flows would be the bees    knees 	


 

 OK, Selwyn,

     I will do that probably the next time I fly my  bird.  Right now, Nick and I are heavily involved in running the ASTM test  for light sport, so both of us are flying Arion's airplanes.  I just  hope the weather stays flyable.

 Buz

 Feeling the pinch at the grocery store?  Make dinner for $10 or less.

  [quote][b]

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