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Overspeed C/S propeller

Rosie

Rosie

Well Known Member
Yesterday, Tuppergal and I took off for an quick overnight to the Lake Tahoe area. Runup was normal with 2 prop cycles...

Just after rotation on climb out, I noticed the plane seemed to have more 'pep' on climbing out. A quick scan showed the prop running about 3000 rpm, yikes!!!! Those Lightspeed headsets sure do their job...

I first pulled the prop back but nothing happened so then gently pulled throttle back to about 24" and the prop rpm followed it (to about 2500). Never made it out of the pattern, landed uneventfully and pulled the cowl.

Of course, the governor was suspect, and I called the local prop shop to bounce it off them.

They recommended before pulling the governor to place the prop horizontal and pull the 2 bottom zirk grease fittings. Poke around inside with a tie-wrap to check/see if any engine oil comes out (bad). Ours was all grease.

Pulled the Woodward governor, and Mercedes flew me to the Johnson Prop Shop at Shafter (MIT). They'll have it ready for us on Monday.

The governor had about 1500 hours since new, and the shop owner was surprised it failed since the Woodward governors are like the Energizer Bunny.... they keep going and going...

I wanted to share the 'horizontal' prop tip that is obvious (now) but I hadn't thought of it before :) Rosie
 
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Rosie said:
I first pulled the prop back but nothing happened so then gently pulled throttle back to about 2400 rpm and the prop rpm followed it. Never made it out of the pattern, landed uneventfully and pulled the cowl.
Click to expand...

Huh......? Do your engine RPM and prop RPM sometimes differ?
 
Rosie said:
Yesterday, Tuppergal and I took off for an quick overnight to the Lake Tahoe area. Runup was normal with 2 prop cycles...

Just after rotation on climb out, I noticed the plane seemed to have more 'pep' on climbing out. A quick scan showed the prop running about 3000 rpm, yikes!!!! Those Lightspeed headsets sure do their job...

I first pulled the prop back but nothing happened so then gently pulled throttle back to about 2400 rpm and the prop rpm followed it. Never made it out of the pattern, landed uneventfully and pulled the cowl.

Of course, the governor was suspect, and I called the local prop shop to bounce it off them.

They recommended before pulling the governor to place the prop horizontal and pull the 2 bottom zirk grease fittings. Poke around inside with a tie-wrap to check/see if any engine oil comes out (bad). Ours was all grease.

Pulled the Woodward governor, and Mercedes flew me to the Johnson Prop Shop at Shafter (MIT). They'll have it ready for us on Monday.

The governor had about 1500 hours since new, and the shop owner was surprised it failed since the Woodward governors are like the Energizer Bunny.... they keep going and going...

I wanted to share the 'horizontal' prop tip that is obvious (now) but I hadn't thought of it before :) Rosie
Click to expand...

Paul,

I had the same thing happen last summer one day when it was 90F, with the MT electric prop.

What the pilot ends up with is a fixed pitch prop at the fine pitch stop. My engine went to 6000 rpm with the prop at 3000 rpm right after take off. I immediately pulled the throttle back and it came down to 5400/2700 respectively, I fugure it was up there about 10 seconds and fortunately when going to the MT over speed chart, it was not an overhaul item. But staying in flight was a challenge as there is very little thrust at the fine pitch stop with the airplane trying to maintain 100 knots. I landed OK but it was dumb not seeing the increase in rpm on the runway. I've since changed my take off procedure so that won't happen again. If the rpm starts up dramatically as air speed builds, something ain't right. :)
 
During the test period

Took off steep climbout upon reaching 2000ft the prop ran away and the "blue knob" was useless. I pulled the throttle back with both hands and got it back to the high two thousands. I observed very small streamers on the left corner of the wind shield. I told the tower at Chino I would have to return to the airport. The engine seized on the landing roll. Careful review of the Hartzell requirements determined that the prop would have to be inspected by a prop shop but the overhaul was not required (it was time at rpm level criteria). Many thousands of dollars later I know the risk of installing fittings by hand to assure you don't get something in them in a current activity. When you install them go all the way because you may forget to go back and tighten them properly at a later time.

Rosie, having gone through a prop runaway in flight I am very interested in the cause of this malfunction in as much detail as you can supply.

Bob Axsom
 
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No, not what he said

captainron said:
Huh......? Do your engine RPM and prop RPM sometimes differ?
Click to expand...
Iron man that is not what he said. With c/s prop if you pull the throttle back with a constant speed prop, usually the RPM stays the same if the Gov is working**. :D

** The exception is ground taxi and final approach at low power and airspeed, the Gov no longer can to a get finer pitch; therefore throttle affects RPM, other wise THROTTLE is just manifold pressure. The BLUE knob is RPM.
 
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gmcjetpilot said:
Iron man that is not what he said. With c/s prop if you pull the throttle back with a constant speed prop, usually the RPM stays the same if the Gov is working**. :D

** The exception is ground taxi and final approach at low power and airspeed, the Gov no longer can to a get finer pitch; therefore throttle affects RPM, other wise THROTTLE is just manifold pressure. The BLUE knob is RPM.
Click to expand...

It's not what was said, but what was written: "pulled throttle back to about 2400 rpm and the prop rpm followed it". I know what Paul was implying, but it was too easily infered as that the prop was catching-up with the engine.:)
George, you still believe that pitch controls airspeed and power controls altitude?:D

BTW, shouldn't the low pitch stops keep the RPMs at a safe level even if the governor falls off the airplane?
 
captainron said:
BTW, shouldn't the low pitch stops keep the RPMs at a safe level even if the governor falls off the airplane?
Click to expand...

The LOW PITCH STOPS are set (or should be) for max RPM when stopped and no forward speed. Add some forward speed and then it is not loaded and can then go over RPM if the governor is not working.
 
RV6_flyer said:
The LOW PITCH STOPS are set (or should be) for max RPM when stopped and no forward speed. Add some forward speed and then it is not loaded and can then go over RPM if the governor is not working.
Click to expand...

Sounds right! Every once in a while I'll hear some guy on a downwind leg and the engine will really wind-up, just because years ago some instructor told him to go high rpm at that point in the pattern.
 
Runaway prop

Gary LeGare, a former member and DAR from my EAA chapter had a runaway prop when testing for whirlwind. He was one of the beta testers, for lack of a better description of it. If memory serves me right his governor was not the failure, but rather excessive play on a bearing on the crankshaft. I think he was calling it runout and it was excessive even though his engine only had a few hundred hours on it. (Is this what the prop shop had you testing for with the horizontal prop and pulling the bottom grease fittings?) Rosie, I'm pretty sure you know Gary because he used to mention you and Laird long before I had ever met the two of you. He went by Casper for a call sign. Give him a call if the governor doesn't fix your problem because he went to great lengths to figure out his problem.

Sorry to read about your problem, but glad you and Victoria are safe. Good job buddy.
 
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Paul,

Cut open your filter!!!! Immediately!!!

The shaft seal in your governor will fail if there is metal in the oil. I know of a Corsair that was lost in TX a few years ago because the prop was surging and the owner had to put it down in a field. The engine quit because of a mechanical failure, but the prop surging was an early warning sign of metal in the oil.
 
captainron said:
BTW, shouldn't the low pitch stops keep the RPMs at a safe level even if the governor falls off the airplane?
Click to expand...

Ron,
You make a great point. I have personally experienced a governor failure on a non-RV with an alternative powerplant (Chevy V-8) with a custom propellor (MT made it for us to spec) that rendered the aircraft a glider.
I made it back to the airport, but we learned the manufacturer set the fine pitch stops to a position that would not make enough thrust to fly the airplane. The mechanic adjusted the prop and we tested it thoroughly with and without the governor.

Moral of the story - Props that are designed for RVs should be set appropriately at the factory, but I would(will) verify before installation.
 
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