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1. 06:24 PM - Yak 52 Questions (Grayson)
2. 07:25 PM - Re: Yak 52 Questions (lOU)
3. 07:57 PM - Re: Yak 52 Questions (Grayson)
4. 10:25 PM - Re: Yak 52 Questions (Brian Lloyd)
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| 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
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352105#352105
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| Subject: | Yak 52 Questions |
Grayson
If you fill oil to max when cold it will be over full when hot and will
overflow.
Lou
-----Original Message-----
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Grayson
Sent: Tuesday, 13 September 2011 11:22 AM
Subject: Yak-List: 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
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352105#352105
Message 3
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| Subject: | Re: Yak 52 Questions |
Ok, thanks.
Didn't think about that
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352111#352111
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| Subject: | Re: Yak 52 Questions |
On Mon, Sep 12, 2011 at 6:21 PM, Grayson <grayson50@hotmail.com> wrote:
>
> 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:
1. 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.
2. Load the airplane to the gross weight you want to use.
3. 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.
> 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.
>
> 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@lloyd.com
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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