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Prop RPM Issue.

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NebraskaYak

Joined: 02 Sep 2008
Posts: 31
Location: Nebraska

Posted: Wed Sep 03, 2008 10:45 am Post subject: Prop RPM Issue.

Greetings, I am fairly new to the Yak world. I'm having an issue with prop rpm. I cannot achieve less then about 80% inflight. Prop checks fine on the ground down to 40ish%. I have the 2 blade V530 prop. Swapped governors and still seeing the same issue. Takeoff rpm is perfect at  100% at the stops. Any ideas? Blade angels look to be right around 14.5 degrees and counterweights at around 25 degrees. I saw some old threads about this, but no answers. Thanks in advance for the help.



Andrew

mark.bitterlich(at)navy.m
Guest

Posted: Wed Sep 03, 2008 11:51 am Post subject: Prop RPM Issue.

Can you give more details?  Are you keeping the throttle at 100% when

you try to achieve less than 80% on the engine?  Where is the manifold

pressure?  Have you reduced the manifold pressure to about 70 mb and see

what it does then?  



Have you adjust the low stop on the gov?  



I am not an expert on this subject, but am just curious about the above

questions.  Dennis or Doug can give you better ideas. 



Mark

 



--

randmyak52(at)bellsouth.n
Guest

Posted: Wed Sep 03, 2008 12:49 pm Post subject: Prop RPM Issue.

Are certain that the tact generator is functioning properly? The 40ish is 

too low, should come back to some 52-53%.

---

NebraskaYak

Joined: 02 Sep 2008
Posts: 31
Location: Nebraska

Posted: Wed Sep 03, 2008 4:47 pm Post subject: Re: Prop RPM Issue.

I am sure the tach gen is working fine, we checked it out. It is obvious, through noise and feeling, that the prop isn't coming back like it should be. I have also tried bringing the throttle back and no change is noted till below 400mb. As far as the low pitch stop on the gov goes, there is plenty of travel left on the prop lever and correspondingly on the front of the governor before it hits the stops, it is just that nothing is happening from midway through the prop lever/prop governor movement all the way back to the stops, rpm stays at 80%. Weird part is that everything works as it should on the ground run up, I see 100% and I can bring the prop rpm back as needed. I just can't do it in flight.

talew(at)bellsouth.net
Guest

Posted: Wed Sep 03, 2008 5:13 pm Post subject: Prop RPM Issue.

Hi ,

I had a similar problem with a CJ . I found that the sleeve that contained 

the control cable for the prop governor was not secure and would allow the 

tube to slip when I tried to reduce the RPM.

Terry Lewis

---

randmyak52(at)bellsouth.n
Guest

Posted: Wed Sep 03, 2008 6:22 pm Post subject: Prop RPM Issue.

Have you pulled the cylinder out of the prop hub and moved the blades to 

assure that they are moving freely? Each blade should move with ease once 

the cylinder is out. If not the prop should be dissembled, checked and 

lubricated if no damage is found.

---

dsavarese0812(at)bellsout
Guest

Posted: Thu Sep 04, 2008 2:32 am Post subject: Prop RPM Issue.

Robert is correct.  When doing the run up prior to take off at 70%, the prop 

check should cycle back to 54-53%.  Not 40 ish percent.  The initial set up, 

(not just the stops on the stop plate) may be incorrect.  In other words, 

the position of the arm on the shaft of the prop gov. may be incorrect. 

You may want to use the M14P manual to correctly set the prop governor.



One other area to check.  The cable assembly going to the prop governor.  Be 

absolutely certain the copper sleeve is 100% secure in the clamps all the 

way back to the control lever in the cockpit.  Should the sleeve be slipping 

during flight, the prop governor will not function properly.  Grab the cable 

sleeve and push/pull hard on it forward of the cylinders, then behind the 

cylinders but forward of the firewall, and finally inside the fuselage 

between the firewall and the clamp which is forward of the left console. 

All clamps must be tightly secured against the cable sleeve.

Dennis



---

NebraskaYak

Joined: 02 Sep 2008
Posts: 31
Location: Nebraska

Posted: Thu Sep 04, 2008 10:33 am Post subject: Re: Prop RPM Issue.

Thanks for the advice guys. I will try all those and let you know how they worked.

mark.bitterlich(at)navy.m
Guest

Posted: Thu Sep 04, 2008 11:58 am Post subject: Prop RPM Issue.

Very very strange.   One person suggested that the cable sleeve might be

moving.  That is a very good suggestion and easily could cause your

issue.  You need to figure out a way to make ABSOLUTELY SURE that the

gov. lever is being moved all the way back to the stop IN FLIGHT!   We

know it is on the deck, but you need to make sure it is doing it in the

AIR.  



After that, I have one question.... Has the nose case been off this

engine anytime recently? 



Mark Bitterlich

--

NebraskaYak

Joined: 02 Sep 2008
Posts: 31
Location: Nebraska

Posted: Sun Sep 21, 2008 6:15 pm Post subject: Re: Prop RPM Issue.

Just wanted to let you all know how the prop rpm problem is going. It turned out that the blade angles were actually off by a few degrees. We checked, double checked and reset them to the 14.5 degree setting and everything works perfect. Thanks for the help. It doesn't take them to be off by much to affect your rpm. 3-4 degrees will do it.

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