Odd prop governor issue

robin ardoin

robin ardoin

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PoA Supporter
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Mar 23, 2022
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Location
Lafayette, LA
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Robard
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KOPL
The engine is a TSIO-520R, T210N, Hartzell Scimitar prop. Lately, on takeoff, the RPM hit 2650 the came back to 2600 in the roll. Nothing detectable in the climb performance while lightly loaded. Yesterday, I was moving my AOG plane (alternator issue) back to my home field and the RPM rolled back about 30 or so revs in the initial climb just before pulling power to my usual 35/2500 cruise climb. Manifold pressure at 36.5, FF 31-32gph so making boost and getting fuel. Today I did some high speed taxi runs to full power and the RPM would surge up to 2650 at full power application before airspeed built then the governor pulled the RPM to 2455-60 and did not change up to 60kts. I made three runs with the same result. It appears the the prop is hitting the low pitch stops at the right speed but the governor has other plans. It should run up to 2700rpm in the roll. I noticed that the governor arm is not against the high speed stop with the speed control fully in. I did have the motor mounts changed at annual in April and this seems to be getting worse since then. I’m suspecting a linkage issue. Hopefully not an engine issue. Thoughts, taunts, jokes??? All welcome….thoughts on potential causes more welcome. ;)
 
Ed Haywood said:
Adjust your cable for full travel of the governor arm.
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I assume if the arm is up against the high speed stop when the cable is fully firewalled, the governor, if functioning correctly, will not step in pull the blades off the low pitch stop. Am I thinking correctly? Hopefully I can get a mechanic to look at it this week. I’m going back to the hangar tomorrow and look behind the panel and see if any is amiss between the firewall and the mount at the lower panel. I also had the main panels pulled for avionics work and perhaps that also could have disturbed the cable. Hopefully that simple. Getting to the cable between the firewall and the governor is another matter.
 
Dan Thomas said:
Probably that simple. The cable housing clamp to the engine might also be loose, letting the housing shift back and forth and messing up the rigging.
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CORRECT! Bob, tell him what he’s won.

Bingo, Dan. The clamp near cylinder 6 had loosened and the cable could not move the governor arm against the high speed stop. I was losing over 200 rpm and only getting 91% power (282 out of 310hp). I ordered a new cable from McFarlane since that one was looking a little like it was ridden hard and put up wet.
 
Not the same issue, but you got my attention. I was adjusting my Hartzell Scimitar prop yesterday on my 182. They say if you want 2600 max, set it to 2550 static. Nope, didn't work. At 2550 static, when taking off, it would go right up to and beyond 2600. Anyway, after many, many adjustments, finally got it nailed.
 
Lowflynjack said:
Not the same issue, but you got my attention. I was adjusting my Hartzell Scimitar prop yesterday on my 182. They say if you want 2600 max, set it to 2550 static. Nope, didn't work. At 2550 static, when taking off, it would go right up to and beyond 2600. Anyway, after many, many adjustments, finally got it nailed.
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Sounds like the high speed stop needed to be set properly. I was told, upon takeoff roll, to dial back the prop control until the rpm is at the target number, leave the control untouched, shut down then adjust the HS stop until it touches the governor arm. That’s what we did and they had it dialed in.
 
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