Before a repaired rotor blade is delivered to the customer, it must be balanced in order to adjust the rotor blade in terms of weight distribution according to the factory values. This is important for conformity with the other rotor blades. The better the balance and aerodynamic shape of the rotor blade is adjusted after repair, the fewer flights are needed at the customer to balance the rotor blade set. However, traditional static balancing only considers blade mass centre of gravity measurements and adjustments.
Innovation Track 3: Developing a testing facility to reduce maintenance costs
The purpose of the project is to develop an innovative helicopter rotor blade static testing facility capable of measuring the properties of rotor blades. The facility will measure all the blade properties that are relevant for the blade dynamic behaviour. The aim is to use this information for a blade adjustment advice, prior to the dynamic Rotor Track Balancing (RTB) of the blades. The ultimate goal is to reduce the number of required flights for RTB and thus to reduce helicopter maintenance costs for Defence.
Computer simulations
Computer simulations done by NLR in 2019 have resulted in a ranking of blade parameters that are most significant for efficient Rotor Track & Balance. The ranking is adopted by the Royal Netherlands Air Force (RNLAF) for assessment in a test phase and implementation in a certification trajectory. On the basis of NLR’s findings a precision measuring facility was developed and commissioned by SPECTO.
Measuring facility
The measuring facility consists of balancing equipment with purpose-made precision scales on either end. A 50 kg scale is positioned at the root side of the sub frame and two 35 kg scales are positioned at the tip side of the leading edge and the trailing edge of the sub frame. This allows for three-point measurements to be carried out to determine the centre of gravity of the propeller blade. The scales can only be used correctly after calibration. The calibrated weight needs to be verified before each use and the scales need to be calibrated once a year.
Proven method
The analyses and state-of-the-art measuring facility have proven to support a more efficient Rotor Track & Balance procedure for RNLAF Apache helicopters. Proper balancing of a rotor blade decreases the required number of Rotor Track & Balance (RT&B) flights.
Project status
Runtime: May 2016 – May 2019
Project closed.
Parties involved
More information
For any questions about the project (status) or if interested to collaborate, please contact:
Richard Bakker (NLR) Richard.Bakker@nlr.nl or Marco Brinkman (SPECTO) M.Brinkman@spectoaerospace.com