Let's face it, the helicopter is the poster child for vibration in
the aviation community. Getting a set of main rotor blades to fly alike
across different aircraft weights, airspeeds and collective position can
be frustrating. Tracking a difficult set of blades can take days, and
the rotor trimming is often left in a less than satisfactory state.
Routine track and balance is well...routine. Most mechanics can manage
routine. JFDynamics can handle routine, but specializes in difficult
rotor issues. Sometimes these
problems fall into training issues with the maintenance staff, and
sometimes they rest with the equipment used to perform the rotor
smoothing, and sometimes they are bona fide rotor issues. Knowing which one is key to prevent burning up engine starts
and aircraft time with no end in sight. Even a difficult rotor should
take no more than half a day before the issue is identified.
Main rotor track and balance procedures and sensor suites
vary, but generally an accelerometer is used in both the vertical and
lateral planes. Rotor tip path corrections are done using either a
Strobe for direct observation, or by using an optical device used to
measure blade relative height. Since there are often large and unexpected changes to other flight regimes when a rotor adjustment is made, it is vital the operator take these into
account. Some operators depend on a coded computer model to
calculate these idiosyncracies. Experience has shown these "intelligent"
programs can be very effective at rotor smoothing, often using
adjustment sets that are outside the traditional concept of what it
takes to smooth the rotor. That's great, but when the aircraft does not
conform to the computer model, the program often cannot smooth the rotor and the operator is left wondering what happened. At that point you need
professional help (no pun intended).
JF Dynamics offers training for helicopter operators.
A one day course includes basic vibration theory, vibration as it
applies to the helicopter (general), and aircraft model specific setup,
operation, and rotor smoothing strategies. On aircraft training is offerred as well, but
generally takes an additional 4-8 hours training time.