Avidflyer2
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RE: Seneca II with the Hartzell "Top Prop" 3-bladed Propeller Conversion having PN: PHC-C3YF-2CK(L)UF Propellers
It was reported that the left engine would not produce rpm over 1500 and with the engine oil temp normal, but oil pressure was dropping to 10 psi.
Troubleshooting revealed that the problems were twofold: oil cooler "Vernatherm" thermostatic oil bypass valve was causing the higher than normal oil temperature and loss of oil pressure as the engine had to work harder driving the propeller at a to high of a pitch while on the ground; and the propeller was not staying on the low pitch stop during run-up.
Long story short is that the allen-head bolt holding the "Start Latch" or sometimes called "High Pitch Latch" had backed out almost a quarter of an inch inside of the propeller. This bolt can only be seen when the low pitch stop adjuster is removed from the prop dome. The bolt would travel with the pitch change shaft and hit the low pitch stop while preventing the propeller blades from reaching fine pitch at or around 13.2* for the Seneca.
The visual indication from outside of the airplane is that the prop pitch would not change to a lower pitch setting immediately after engine start, and would move to high pitch (low rpm) as engine rpm was increased up to the reported 1500 rpm even with full throttle being applied.
The fix was to remove the propeller and take it to the prop shop where they removed the low pitch stop adjuster and torque tightened the latch bolt. They removed it for inspection and even applied loctite to the threads to prevent this from happening again.
There isn't any rotational force on this latch bolt during operation so it is a bit of a mystery why this happened. It should have been caught during takeoff as it would limit static rpm to less than takeoff and get progressively worse as time went by. I suspect this had gone on for a very long time indeed.
It was reported that the left engine would not produce rpm over 1500 and with the engine oil temp normal, but oil pressure was dropping to 10 psi.
Troubleshooting revealed that the problems were twofold: oil cooler "Vernatherm" thermostatic oil bypass valve was causing the higher than normal oil temperature and loss of oil pressure as the engine had to work harder driving the propeller at a to high of a pitch while on the ground; and the propeller was not staying on the low pitch stop during run-up.
Long story short is that the allen-head bolt holding the "Start Latch" or sometimes called "High Pitch Latch" had backed out almost a quarter of an inch inside of the propeller. This bolt can only be seen when the low pitch stop adjuster is removed from the prop dome. The bolt would travel with the pitch change shaft and hit the low pitch stop while preventing the propeller blades from reaching fine pitch at or around 13.2* for the Seneca.
The visual indication from outside of the airplane is that the prop pitch would not change to a lower pitch setting immediately after engine start, and would move to high pitch (low rpm) as engine rpm was increased up to the reported 1500 rpm even with full throttle being applied.
The fix was to remove the propeller and take it to the prop shop where they removed the low pitch stop adjuster and torque tightened the latch bolt. They removed it for inspection and even applied loctite to the threads to prevent this from happening again.
There isn't any rotational force on this latch bolt during operation so it is a bit of a mystery why this happened. It should have been caught during takeoff as it would limit static rpm to less than takeoff and get progressively worse as time went by. I suspect this had gone on for a very long time indeed.
