AvFlyGuy
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- Joined
- Apr 27, 2012
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I'm having a very unusual situation that seems to defy finding an explanation thusfar.
After a recent engine rebuild (Overhaul) on the A-65, the following external components were also replaced. New Engine Mount, all new rubber mounts, bolts, washers, nuts etc. A new prop (McCauley CM7443 - same prop as before) prop bolts, spacers, nuts, and spinner. The engine was professionally overhauled and crank and rods balanced. All mounting hardware is new. Installation Torque values have been checked and double checked.
So, here's whats happening. When making a steep turn to the left ~ 30* bank or more - with around ~1.5 G's there is a very noticeable high frequency vibration felt in the rudder pedals (more on the left pedal than the right) and the stick and maybe a little in the seat frame. The same steep turn to the right there is no vibration, nor in any other phase of flight. Only in a steep left turn. Airspeed is not a factor as its's been flown on the low end (safe) speed for the steep bank angle and at higher speeds (haven't exceeded 100MPH indicated). Neither frequency or amplitude changes based on indicated airspeed. Vibration is not felt on any other parts of the airframe or if so, it isn't significant enough to be felt. I would liken the vibration (for simplicity) to say a kitchen blender running on low and your hands can "feel" that harmonic effect, but with much less amplitude than that of the blender analogy. Or another (kind of analogy) would be a car engine at mid to high RPM with no harmonic balancer on it.
Going a step further, making same turns both to the left and right and applying intentional slip then skid during the turn neither lessens or intensives the effect....vibration remains in the left hand turn only. The only other variable is engine RPM. When RPM is reduced from cruise 2150, in 200 RPM increments the vibration is still present but the 'frequency' lessens but amplitude remains constant. Airspeed remains constant by pitch adjustments as RPM's are decreased. Not until the engine is at or near idle (1000-1200) RPM with airspeed constant (75mph indicated) does the vibration go away.
As discussions about this phenomenon with AP/IA's and a number of other high time pilots in my circle of hangar buddies the ideas and speculation are rampant. One constant which all seem to agree on is that the engine knows no difference between level flight or turning, inverted or any other aspect. It's just doing it's job of producing thrust via the propeller.
Anybody else experienced this of have clues what's causing it - and how to fix it?
After a recent engine rebuild (Overhaul) on the A-65, the following external components were also replaced. New Engine Mount, all new rubber mounts, bolts, washers, nuts etc. A new prop (McCauley CM7443 - same prop as before) prop bolts, spacers, nuts, and spinner. The engine was professionally overhauled and crank and rods balanced. All mounting hardware is new. Installation Torque values have been checked and double checked.
So, here's whats happening. When making a steep turn to the left ~ 30* bank or more - with around ~1.5 G's there is a very noticeable high frequency vibration felt in the rudder pedals (more on the left pedal than the right) and the stick and maybe a little in the seat frame. The same steep turn to the right there is no vibration, nor in any other phase of flight. Only in a steep left turn. Airspeed is not a factor as its's been flown on the low end (safe) speed for the steep bank angle and at higher speeds (haven't exceeded 100MPH indicated). Neither frequency or amplitude changes based on indicated airspeed. Vibration is not felt on any other parts of the airframe or if so, it isn't significant enough to be felt. I would liken the vibration (for simplicity) to say a kitchen blender running on low and your hands can "feel" that harmonic effect, but with much less amplitude than that of the blender analogy. Or another (kind of analogy) would be a car engine at mid to high RPM with no harmonic balancer on it.
Going a step further, making same turns both to the left and right and applying intentional slip then skid during the turn neither lessens or intensives the effect....vibration remains in the left hand turn only. The only other variable is engine RPM. When RPM is reduced from cruise 2150, in 200 RPM increments the vibration is still present but the 'frequency' lessens but amplitude remains constant. Airspeed remains constant by pitch adjustments as RPM's are decreased. Not until the engine is at or near idle (1000-1200) RPM with airspeed constant (75mph indicated) does the vibration go away.
As discussions about this phenomenon with AP/IA's and a number of other high time pilots in my circle of hangar buddies the ideas and speculation are rampant. One constant which all seem to agree on is that the engine knows no difference between level flight or turning, inverted or any other aspect. It's just doing it's job of producing thrust via the propeller.
Anybody else experienced this of have clues what's causing it - and how to fix it?
