H145 New Comfort Experience: Upgrading From Four-Bladed HMR To Five-Bladed BMR

Abstract

In 2020, Airbus Helicopters achieved EASA type certification of the BK117 D-3 (branding name H145), which is the latest variant of the BK117 family. It entails a significant upgrade from the BK117 D-2. The major change, a new five bladed main rotor, required extensive investigations with respect to dynamics. This paper gives a short overview of the history of the BK117 family development from its beginnings up to now and on the investigations performed in the fields of structural dynamics, aeromechanics stability and equipment integration for its latest variant. A development and certification methodology, relying on the use of numerical tools validated by using the results of extensive laboratory, ground and flight testing was applied. It is shown that the upgrade of the H145 with the five bladed rotor allowed to reduce the helicopter's empty weight by omitting landing gear dampers and anti-vibration measures as well as thanks to the reduced weight of the rotor system itself.

Fibre-optic measurement of strain and shape on a helicopter rotor blade during a ground run: 1. Measurement of strain

“…The identification of the natural frequencies of a non-rotating BMR rotor blade via analysis of data recorded by FBG and DFOSS sensors during ground vibration tests undertaken in a laboratory was reported in [18,19]. In the case of the data reported here, recorded with the blade rotating, the blade's stiffness changes resulting from the centrifugal forces and aeroelastic loading would be expected to alter the blade vibration frequencies [37]. Thus the sources of the observed frequency components are not discussed here, but their identification is the subject of on-going work.…”

Fibre-optic measurement of strain and shape on a helicopter rotor blade during a ground run: 2. Measurement of shape

“…Here, it can be seen that in general DFOSS more clearly resolves the natural modes and that simple strain sensing does lack the directional knowledge demonstrated here. Furthermore, it can be seen that by mapping the transitions of the blade vibration frequencies as a function of the helicopter rotation rate, especially visible during wind-down starting at 360 s, it should be possible to acquire the complete Campbell diagram [36] of the helicopter blade, even including weakly excited higher order blade vibration modes. Such analysis could provide useful information for blade characterisation and health monitoring if routinely used.…”