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Grayson

Joined: 10 Aug 2008
Posts: 7

Posted: Mon Sep 12, 2011 5:21 pm Post subject: Yak 52 Questions

Any input is appreciated,



First, is there any consensus for V speeds on the Yak 52. I know there can be a bit of confusion since they come in 3 flavors (mph, knots, km/h) but it seems like every site I visit has a different number. I've seen Vne from 226mph to about 275mph, and stall clean from about 60 mph up to 75 mph and dirty from about 60 mph to 70 mph. The stall numbers are what I'm most interested in. My 'POH' has clean at 69mph and dirty at 63mph (my indicator is mph) I believe. But the my POH isn't even the original.



Also, I'm doing a long cross-country soon. Is there any problem with filling the oil reservoir all the up to 16L so I don't have to add oil as often? I know not to turn it upside down like this as a lot will come out.

But you don't get a higher oil burn rate because you have the reservoir filled do you?



And..

Any consensus on the best throttle and prop setting for max range? 60 units throttle and 60% prop? Oversquare 65 throttle, 60% prop? Any limit to how much is safe to oversquare by? And is the reason for oversquaring because a higher rpm results in higher fuel consumption more so than a high manifold setting?



Thanks,

Grayson

ldakos(at)bigpond.net.au
Guest

Posted: Mon Sep 12, 2011 6:25 pm Post subject: Yak 52 Questions

Grayson



If you fill oil to max when cold it will be over full when hot and will

overflow.



Lou



--

Grayson

Joined: 10 Aug 2008
Posts: 7

Posted: Mon Sep 12, 2011 6:54 pm Post subject: Re: Yak 52 Questions

Ok, thanks.

Didn't think about that

Rob Rowe

Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK

Posted: Tue Sep 13, 2011 2:26 am Post subject: Re: Yak 52 Questions

 	  Grayson wrote: 	
		  

First, is there any consensus for V speeds on the Yak 52. 

...

Any consensus on the best throttle and prop setting for max range? 	




Hi Grayson,



FWIW the attached (partially translated) document from the Russian Ministry of Transport is dated 1990 and is the latest I've been able to find. 



It appears to supersede figures for all YAK-52s, not just later built ones.



The stall speeds have been revised as follows (power off / max weight);

In a landing configuration - 110 km/h (Vs0)

In direct flight - 120 km/h (Vs1)

In inverted flight - 150 km/h (previously 140 km/h)



As always treat these as theoretical, from my own 1991 aircraft last (triennial) flight test gave a Vs0 of 105 km/h & Vs1 of 114 km/h ... yours may (will) vary.



Interesting the inverted stall has been revised up  ... recall the aerobats amongst us commenting a while back on the list that the original 140 km/h was understated. 



Also note the widely mis-quoted stall speed of 100km/h (landing configuration at NOMINAL 1 power - short field?) has been deleted entirely from this 1990 document. 



As to range even in this document there are minor discrepancies ... so caution advised. Section 1.2.2 quotes fuel range calculation based on 120 litres is 465km, yet table 3 uses 118 litres & 460km ... both look generous, literally YMMV.



The max range calculation is based on flying at 190 km/h IAS (195 km/h CAS) at an altitude of 500 metres, using 55% RPM and manifold as required to produce the stated IAS.



It allows for 118 litres of fuel available at take-off (so after start, taxi , power check) ... again generous, but maybe DOSAAF usage assumes a ground crew has warmed oil etc.



From this 118 litres a 10% reserve (not 'unusable' as often mis-quoted) of 12 litres is subtracted plus another 7 litres for take-off, climb to 500 metres and for a circuit to land (from their own figures in table 2 another 0.5 litre should have been added for the descent phase); leaving 99 litres available for en-route fuel.



Using the stated power / CAS apparently gives a fuel burn of 42.51 litres/h giving an en-route range of 454 km, plus another 5.5 km in the circuit (from table 2) to give (rounded up) a 460 km distance travelled. Enabling an en-route flight time of 2h 20mins and total flight time (including circuit) of 2h 30min (although table 2 suggests this should be 2h 28min).



So while these purport to be the official (theoretical) figures they look rather generous from a practical perspective. So advisable to supplant your aircraft's data (based on experience) into this calculation and then factor a personal additional safety margin on top ... as stated above YMMV!



FYI - my comments in green were from submitting this to the UK CAA in May 2010 requesting clarification on Permit to Fly limitations and flight manuals in circulation ... I'm still awaiting a response (gentle hint).



brgds, Rob R

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cjpilot710(at)aol.com
Guest

Posted: Tue Sep 13, 2011 5:06 am Post subject: Yak 52 Questions

I can only add one thing to Brain's post.  Keeping an engine 'over  square' can help with the longevity of the engine.  You want the engine to  be driving the prop - not the prop driving the engine.  This is known as  "back loading" for which the bearings and such in the engine are not really  design for.  This is particularly bad for bigger engines (W1820 &  PW1830).  The HS6a and M14p are somewhat "beef-e-er" for their size/hp so  they are not quite as critical for the occasional backloading.  A few  cycles in an 1830 and you'll be changing an engine way before that 1,000 hours  mark.

  

 As Brain pointed out the IAS at stall is what it is.  It is the  instrument you will be using for reference.  It can read in any units of  valve of what ever you want to call them.  And they are only good in your  airplane.  There are a great many errors from the real TAS at stall to that  of ASI simply because of system design.  You can even see this in a Cessna  or Piper.  Have you ever seen an ASI with one (1) kt/mph increments?   Also remember that a stall is really defined by the critical angle of attack of  that particular airfoil not a speed.

  

 Jim "Pappy" Goolsby

  

  In a message dated 9/13/2011 1:25:52 A.M. Eastern Daylight Time,  brian(at)lloyd.com writes:

  	  Quote: 	
		  



   On Mon, Sep 12, 2011 at 6:21 PM, Grayson <grayson50(at)hotmail.com (grayson50(at)hotmail.com)>    wrote:

    	  Quote: 	
		  --> Yak-List message posted by: "Grayson" <grayson50(at)hotmail.com (grayson50(at)hotmail.com)>



Any      input is appreciated,



First, is there any consensus for V speeds on      the Yak 52. I know there can be a bit of confusion since they come in 3      flavors (mph, knots, km/h) but it seems like every site I visit has a      different number. I've seen Vne from 226mph to about 275mph, and stall clean      from about 60 mph up to 75 mph and dirty from about 60 mph to 70 mph. The      stall numbers are what I'm most interested in. My 'POH' has clean at 69mph      and dirty at 63mph (my indicator is mph) I believe. But the my POH isn't      even the original.

	
   



   Go out and find out for yourself. Here:

           Calibrate your airspeed indicator. I have a spreadsheet that uses three      GPS track and groundspeed pairs to calculate TAS and winds aloft. I then use      pressure altitude and temperature to convert TAS to CAS. From that you can      build your own airspeed indicator calibration card.      
Load the airplane to the gross weight you want to use.      
Go out and carefully fly a stall series. Use very slow deceleration so      you can carefully read the IAS when the break occurs.   Now you know the real stall speed, not some number that someone else    wrote down that may or may not be correct.



   



   BTW, once you know the stall speed, you can properly calculate    maneuvering/cornering speed for your airplane. Take the square-root of the    maximum load factor, 7 G's in the case of the Yak-52 (2.65), and multiply it    by the stall speed. The result is Va.

   



   Unfortunately, you have to get Vne from the designer.

   



    

    	  Quote: 	
		  Also, I'm doing a long cross-country soon. Is there any      problem with filling the oil reservoir all the up to 16L so I don't have to      add oil as often? I know not to turn it upside down like this as a lot will      come out.

But you don't get a higher oil burn rate because you have the      reservoir filled do you?

	
   



   You can do that but you need to know how much drains back into the engine    sump when the aircraft is sitting. Once you get going, the engine sump oil    pump will keep the sump scavenged and will raise the level of oil in the tank.    The best way to know what your maximum fill point is is to check the level    cold, fly a very short hop, and then immediately check the oil level on    landing. 

    

    	  Quote: 	
		  

And..

Any consensus on the best throttle and prop      setting for max range? 60 units throttle and 60% prop? Oversquare 65      throttle, 60% prop? Any limit to how much is safe to oversquare by? And is      the reason for oversquaring because a higher rpm results in higher fuel      consumption more so than a high manifold setting?

	
   



   Generally speaking, running "over square" is not going to hurt an engine    that is not boosted (turbocharged or supercharged). But the M14P does have a    supercharger. The boost used in the standard 360hp motor is not all that great    but there MAY be a maximum MAP for a lower RPM in the PF. You need to get that    info from the engine manufacturer.

   



   As for fuel consumption, lower RPMs result in lower frictional losses in    the engine. So if you reduce RPM and increase MAP to get the same hp out of    the engine, you will have lower frictional losses and thus slightly lower fuel    burn.

   



   If you want to get carried away (and I usually do) there is one more    thing to think about and that is the RPM, torque (proportional to MAP) and TAS    for maximum prop efficiency. Prop blades have twist because the velocity of    the tips is greater than the velocity near the hub. So the angle of attack of    the prop blades is changing from hub to tip. There is an optimal combination    that will result in the maximum conversion of hp into IAS.

   



   Frankly, I doubt anyone has done the flight testing to determine the most    efficient operating point for the Yak-52. I did a lot of this kind of work    with the CJ6A and determined how to safely get 400+nm legs on the stock 42gal    fuel. (I made a couple of cross-country cross-countries in the CJ6A and wanted    to be able to save gas, save time, AND save gas stops. I routinely flew 450nm    legs when I had a 10kt or greater tailwind and still landed with legal    reserves.) You can do it in the Yak-52 but it will take flights at different    altitudes and power settings to determine what works best. If you are planning    a long cross country you can use the trip to try different altitudes and power    settings to determine the effect on fuel efficiency.

   



   But generally speaking, altitude is your friend when it comes to    efficiency. If you need to reduce MAP, do it by climbing, not by pulling the    throttle back. Take an O2 bottle with you and see how the airplane works at    13,000-16,000 feet. I think you will be pleasantly surprised. Hopefully you    have an aux tank so you can spend more time at altitude and less time climbing    and descending.

   



   So don't worry that you don't have a POH with this information. Go figure    it out for yourself. You will be happy you did because you will KNOW that the    numbers are accurate.

   

-- 

Brian Lloyd, WB6RQN/J79BPL

3191 Western    Dr.

Cameron Park, CA 95682

brian(at)lloyd.com (brian(at)lloyd.com)

+1.767.617.1365    (Dominica)

+1.916.877.5067 (USA)



 	  Quote: 	
		  



="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List

s.matronics.com/">http://forums.matronics.com

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 [quote][b]

czech6(at)mesanetworks.ne
Guest

Posted: Tue Sep 13, 2011 5:38 am Post subject: Yak 52 Questions

Brian,

Why do you fill it to gross weight?



Bill



On Sep 13, 2011, at 8:02 AM, cjpilot710(at)aol.com (cjpilot710(at)aol.com) wrote:



[quote]  I can only add one thing to Brain's post.  Keeping an engine 'over  square' can help with the longevity of the engine.  You want the engine to  be driving the prop - not the prop driving the engine.  This is known as  "back loading" for which the bearings and such in the engine are not really  design for.  This is particularly bad for bigger engines (W1820 &  PW1830).  The HS6a and M14p are somewhat "beef-e-er" for their size/hp so  they are not quite as critical for the occasional backloading.  A few  cycles in an 1830 and you'll be changing an engine way before that 1,000 hours  mark.

  

 As Brain pointed out the IAS at stall is what it is.  It is the  instrument you will be using for reference.  It can read in any units of  valve of what ever you want to call them.  And they are only good in your  airplane.  There are a great many errors from the real TAS at stall to that  of ASI simply because of system design.  You can even see this in a Cessna  or Piper.  Have you ever seen an ASI with one (1) kt/mph increments?   Also remember that a stall is really defined by the critical angle of attack of  that particular airfoil not a speed.

  

 Jim "Pappy" Goolsby

  

  In a message dated 9/13/2011 1:25:52 A.M. Eastern Daylight Time,  brian(at)lloyd.com (brian(at)lloyd.com) writes:

  	  Quote: 	
		  



   On Mon, Sep 12, 2011 at 6:21 PM, Grayson <[url=mailto:grayson50(at)hotmail.com]grayson50(at)hotmail.com (grayson50(at)hotmail.com)[/url]>    wrote:

    	  Quote: 	
		  --> Yak-List message posted by: "Grayson" <[url=mailto:grayson50(at)hotmail.com]grayson50(at)hotmail.com (grayson50(at)hotmail.com)[/url]>



Any      input is appreciated,



First, is there any consensus for V speeds on      the Yak 52. I know there can be a bit of confusion since they come in 3      flavors (mph, knots, km/h) but it seems like every site I visit has a      different number. I've seen Vne from 226mph to about 275mph, and stall clean      from about 60 mph up to 75 mph and dirty from about 60 mph to 70 mph. The      stall numbers are what I'm most interested in. My 'POH' has clean at 69mph      and dirty at 63mph (my indicator is mph) I believe. But the my POH isn't      even the original.

	
   



   Go out and find out for yourself. Here:

           Calibrate your airspeed indicator. I have a spreadsheet that uses three      GPS track and groundspeed pairs to calculate TAS and winds aloft. I then use      pressure altitude and temperature to convert TAS to CAS. From that you can      build your own airspeed indicator calibration card.      
Load the airplane to the gross weight you want to use.      
Go out and carefully fly a stall series. Use very slow deceleration so      you can carefully read the IAS when the break occurs.   Now you know the real stall speed, not some number that someone else    wrote down that may or may not be correct.



   



   BTW, once you know the stall speed, you can properly calculate    maneuvering/cornering speed for your airplane. Take the square-root of the    maximum load factor, 7 G's in the case of the Yak-52 (2.65), and multiply it    by the stall speed. The result is Va.

   



   Unfortunately, you have to get Vne from the designer.

   



    

    	  Quote: 	
		  Also, I'm doing a long cross-country soon. Is there any      problem with filling the oil reservoir all the up to 16L so I don't have to      add oil as often? I know not to turn it upside down like this as a lot will      come out.

But you don't get a higher oil burn rate because you have the      reservoir filled do you?

	
   



   You can do that but you need to know how much drains back into the engine    sump when the aircraft is sitting. Once you get going, the engine sump oil    pump will keep the sump scavenged and will raise the level of oil in the tank.    The best way to know what your maximum fill point is is to check the level    cold, fly a very short hop, and then immediately check the oil level on    landing. 

    

    	  Quote: 	
		  

And..

Any consensus on the best throttle and prop      setting for max range? 60 units throttle and 60% prop? Oversquare 65      throttle, 60% prop? Any limit to how much is safe to oversquare by? And is      the reason for oversquaring because a higher rpm results in higher fuel      consumption more so than a high manifold setting?

	
   



   Generally speaking, running "over square" is not going to hurt an engine    that is not boosted (turbocharged or supercharged). But the M14P does have a    supercharger. The boost used in the standard 360hp motor is not all that great    but there MAY be a maximum MAP for a lower RPM in the PF. You need to get that    info from the engine manufacturer.

   



   As for fuel consumption, lower RPMs result in lower frictional losses in    the engine. So if you reduce RPM and increase MAP to get the same hp out of    the engine, you will have lower frictional losses and thus slightly lower fuel    burn.

   



   If you want to get carried away (and I usually do) there is one more    thing to think about and that is the RPM, torque (proportional to MAP) and TAS    for maximum prop efficiency. Prop blades have twist because the velocity of    the tips is greater than the velocity near the hub. So the angle of attack of    the prop blades is changing from hub to tip. There is an optimal combination    that will result in the maximum conversion of hp into IAS.

   



   Frankly, I doubt anyone has done the flight testing to determine the most    efficient operating point for the Yak-52. I did a lot of this kind of work    with the CJ6A and determined how to safely get 400+nm legs on the stock 42gal    fuel. (I made a couple of cross-country cross-countries in the CJ6A and wanted    to be able to save gas, save time, AND save gas stops. I routinely flew 450nm    legs when I had a 10kt or greater tailwind and still landed with legal    reserves.) You can do it in the Yak-52 but it will take flights at different    altitudes and power settings to determine what works best. If you are planning    a long cross country you can use the trip to try different altitudes and power    settings to determine the effect on fuel efficiency.

   



   But generally speaking, altitude is your friend when it comes to    efficiency. If you need to reduce MAP, do it by climbing, not by pulling the    throttle back. Take an O2 bottle with you and see how the airplane works at    13,000-16,000 feet. I think you will be pleasantly surprised. Hopefully you    have an aux tank so you can spend more time at altitude and less time climbing    and descending.

   



   So don't worry that you don't have a POH with this information. Go figure    it out for yourself. You will be happy you did because you will KNOW that the    numbers are accurate.

   

-- 

Brian Lloyd, WB6RQN/J79BPL

3191 Western    Dr.

Cameron Park, CA 95682

[url=mailto:brian(at)lloyd.com]brian(at)lloyd.com (brian(at)lloyd.com)[/url]

+1.767.617.1365    (Dominica)

+1.916.877.5067 (USA)



 	  Quote: 	
		  



="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List

s.matronics.com/">http://forums.matronics.com

p://www.matronics.com/contribution">http://www.matronics.com/contribution



	
	


  	  Quote: 	
		  

	


[b]

tjyak50

Joined: 31 May 2007
Posts: 81
Location: Phoenix, AZ

Posted: Tue Sep 13, 2011 6:10 am Post subject: Re: Yak 52 Questions

Grayson is this a new airplane for you?



Hopefully you have done some 1 hour X-crountry legs first to get an idea on where oil consumption will be and how well the rest of the airplane works.  The oil returned to the tank gets to sit there for a minute and de-bubble some more so I never felt good about overfilling.



With an unknown Yak I find an hour leg is a good place to start, then you can expand from there.  Typically the things that become problems are fuel tanks not feeding right, air not working right and mag coil surging.  These problems help take your mind off the issue of adding oil at the next stop.



In the past I found that some RPM between 66 and 73 will feel smoothest depending on the prop and balance.  Put the throttle adjacent to the Prop lever and thats usually a pretty decent setting.



Higher is better when seeking "Maximum efficiency" in a Yak 52.



Tom Johnson

Yak 50

Phoenix, AZ

www.airpowerinsurance.com

rick(at)rvairshows.com
Guest

Posted: Tue Sep 13, 2011 9:34 am Post subject: Yak 52 Questions

Also worth testing stall speed with prop stopped and in the coarse prop condition your plane returns to with mags off. With the MTV 9-29-260'cm prop on my SU26, stall speed with mags off ( zero oil pressure) gives me a stall speed about  15km an hour  less than book value. 

Rick VOLKER



Sent from my iPhone



On Sep 13, 2011, at 12:03 PM, Brian Lloyd <brian(at)lloyd.com (brian(at)lloyd.com)> wrote:



[quote]



On Tue, Sep 13, 2011 at 6:35 AM, Bill Geipel <[url=mailto:czech6(at)mesanetworks.net]czech6(at)mesanetworks.net (czech6(at)mesanetworks.net)[/url]> wrote:

 	  Quote: 	
		   Brian,

Why do you fill it to gross weight?

	




Well Bill, every airplane ALWAYS flys at gross weight. That is the definition. But we change the gross weight depending on what we take with us. (Or what we had for breakfast -- BURP.  Or were you asking about maximum gross weight? Most manufacturers specify stall speed at max gross weight for the airframe. But we rarely fly our airplanes at max gross weight. So doesn't it make sense to find the stall speed at the weights we normally use?

 



Stall speed varies with loading. As you increase the gross weight, static loading increases, and so does stall speed. (You need a greater airspeed to produce more lift at the critical angle of attack.)

 

So, when you want to find the stall speed under static load conditions, you have to specify AND test at a particular gross weight. In fact, it might be worthwhile to do the testing under typical conditions, e.g.:

 me,
me and Fred,
me and Fred with our chutes,
me and Fred after a big lunch,
me and Fred after a big lunch, wearing chutes, carrying all the crap we will need at Oshkosh. I don't know about you guys but I find flight testing to be pretty fun. I have also found that it is easy to do and quickly shows up the errors in the POH. It also gives you a much greater feeling for the characteristics of your particular airplane. 

 

I had a student that decided to buy his own airplane not long after we started his primary training. He wanted a Comanche 250 and I offered him mine. He declined because I wanted too much money so he went out and found one that was a "good deal". When we went out to fly it the first time the speeds seemed wrong. I assumed that the pitot-static system was leaking but I did what I usually do with a new airplane -- I built an airspeed calibration table as I mentioned in my earlier post.

 



Turns out that the airspeed indicator was dead-nuts accurate. The airplane was actually stalling at the wrong speed. This prompted me to suggest that the plane go into the shop for a look-over. 

 



Turns out that the airplane had been wrecked. (Now we know why he got such a good deal.) Someone had put different wings on the plane and the wings had broken ribs. So not only was the wing rigged wrong, it wasn't holding its design airfoil shape under air loads. In the end it cost him WAY more to fix his "good deal" than it would have to have purchased my plane in the first place. (heh)

 



But the key is that some simple flight testing quickly showed up the characteristics of that particular airplane. This is the kind of thing that every pilot should do when he/she first contemplates acquiring an airplane. Just because it goes up and comes back down again without killing you doesn't necessarily mean it is a good deal. 

 

-- 

Brian Lloyd, WB6RQN/J79BPL

3191 Western Dr.

Cameron Park, CA 95682

[url=mailto:brian(at)lloyd.com]brian(at)lloyd.com (brian(at)lloyd.com)[/url]

+1.767.617.1365 (Dominica)

+1.916.877.5067 (USA)

 

   	  Quote: 	
		  

	


[b]

rick(at)rvairshows.com
Guest

Posted: Tue Sep 13, 2011 12:46 pm Post subject: Yak 52 Questions

The problem with the air show only prop that I use is that, even at 82%rpm, the blades are so flat that with manifold pressure at idle, it disturbs airflow over the wing and tail. Losing oil pressure, It goes to your coarse stop and changes the airflow over the inner third of the wing. Flip the mags off on short final at normal approach speed and you will float at least 500 feet without the prop to break you combined with lower stall speed.  The flat prop also shields the rudder on roll out enough to make it require the use of brakes for directional control, unless the prop is pulled way back. Idle Glide ratio at max rpm is 2.5 :1 which feels like someone threw out a drag chute during the flare. This is useful for carrier approaches and short field landings.

    I also leave at full power for all spin and tumble exits, given much Quicker and more benign recoveries. I would not suggest this practice with a yak 52 .

Rick VOLKER



Sent from my iPhone 



On Sep 13, 2011, at 4:11 PM, Brian Lloyd <brian(at)lloyd.com (brian(at)lloyd.com)> wrote:



[quote]



On Tue, Sep 13, 2011 at 10:29 AM, RICHARD VOLKER <[url=mailto:rick(at)rvairshows.com]rick(at)rvairshows.com (rick(at)rvairshows.com)[/url]> wrote:

 	  Quote: 	
		   Also worth testing stall speed with prop stopped and in the coarse prop condition your plane returns to with mags off. With the MTV 9-29-260'cm prop on my SU26, stall speed with mags off ( zero oil pressure) gives me a stall speed about  15km an hour  less than book value. 

 

	




Now that surprises me. I wouldn't have thought that stall speed would be much affected by the drag of a windmilling prop. Did you get the aircraft into a steady-state descent and then very slowly increase AoA until it stalled?

 

-- 

Brian Lloyd, WB6RQN/J79BPL

3191 Western Dr.

Cameron Park, CA 95682

[url=mailto:brian(at)lloyd.com]brian(at)lloyd.com (brian(at)lloyd.com)[/url]

+1.767.617.1365 (Dominica)

+1.916.877.5067 (USA)

 

   	  Quote: 	
		  



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[b]

CD 2.0

Joined: 21 Feb 2011
Posts: 43

Posted: Tue Sep 13, 2011 6:01 pm Post subject: Re: Yak 52 Questions

Grayson,  



Adding to what Tom said, if you have the stock fuel system, you should definitely not go beyond a 1.5 hour maximum leg until you have flown enough to determine how much fuel is left after this.  



Another thing to consider is that itâ€™s important to have a good understanding of how the pneumatic design works on these airplanes. In a long cross country flight, you might want to carry an extra bottle of compressed air and the appropriate fittings to recharge the airplane's bottle.... Otherwise if you manage to lose air, you won't be able to start the engine and you donâ€™t want to put yourself in the position of not finding anyone able to help at an airport along your route. You might want to bring along your own metric tools as well for that same reason.



Carl



 	  tjyak50 wrote: 	
		  Grayson is this a new airplane for you?



Hopefully you have done some 1 hour X-crountry legs first to get an idea on where oil consumption will be and how well the rest of the airplane works.  The oil returned to the tank gets to sit there for a minute and de-bubble some more so I never felt good about overfilling.



With an unknown Yak I find an hour leg is a good place to start, then you can expand from there.  Typically the things that become problems are fuel tanks not feeding right, air not working right and mag coil surging.  These problems help take your mind off the issue of adding oil at the next stop.



In the past I found that some RPM between 66 and 73 will feel smoothest depending on the prop and balance.  Put the throttle adjacent to the Prop lever and thats usually a pretty decent setting.



Higher is better when seeking "Maximum efficiency" in a Yak 52.



Tom Johnson

Yak 50

Phoenix, AZ

www.airpowerinsurance.com

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