A Balancing Tour
The Simple Facts
balancing does not correct or mask other engine problems.
- Prop balancing is not engine
balancing, rather it is a finely tuned marriage of the prop to the
engine under normal operating conditions.
- Pilots will
grow accustomed to almost any vibration level over time.
- 4 out of 5
pilots believe their engines are running smoothly immediately after overhaul.
This is normally only a 'perceptual' improvement as new 'Lord' mounts
function exceptionally well, isolating prop unbalance vibration to the
engine where it can nonetheless undermine reliability.
- 4 out of 5 props
require 20-40 grams to reduce unbalance and vibration to zero after
- A 30 gram static
unbalance becomes a 75 pound oscillating side-load at the front
engine bearing at 2400 rpm.
- A one mil 'installation error' between
the centerline/interface of a perfectly balanced prop and the engine
crank flange results in ~.3 ips/50 lb side-load at the front engine
- 90% of prop/engine installations are
off centerline by at least 1 Mil. The weight/gravity alone of the prop
hanging on the prop bolts as they are torqued guarantees at least some
causes work hardening/metal fatigue which leads to cracks over time.
and avionics are sensitive to vibration damage which is often
expensive to repair.
unbalance and the resulting vibration amounts to wasted energy.
exacerbates pilot fatigue and can cause passenger concerns.
- Years of
experience, skill and digital equipment are prerequisite to spin
balancing a prop to within ± 1/10th gram.