| Spn1MLxb1 | Blade 1 local edgewise moment at span station 1 | About the local xb1-axis | (kN-m) |
| Spn1MLyb1 | Blade 1 local flapwise moment at span station 1 | About the local yb1-axis | (kN-m) |
| Spn1MLzb1 | Blade 1 local pitching moment at span station 1 | About the local zb1-axis | (kN-m) |
| | | | |
| Spn1FLxb1 | Blade 1 local flapwise shear force at span station 1 | Directed along the local xb1-axis | (kN) |
| Spn1FLyb1 | Blade 1 local edgewise shear force at span station 1 | Directed along the local yb1-axis | (kN) |
| Spn1FLzb1 | Blade 1 local axial force at span station 1 | Directed along the local zb1-axis | (kN) |
| | | | |
| bladed | | | |
| Bladed 1 Mx | Principal axes | | (N-m) |
| Bladed 1 My | Principal axes | | (N-m) |
| Bladed 1 Mxyz | Principal axes | | (N-m) |
| | | | |
| Bladed 1 Fx | Principal axes | | (kN) |
| Bladed 1 Fy | Principal axes | | (kN) |
| Bladed 1 Fxyz | Principal axes | | (kN) |
Principal axes: The positive z-axis follows the local deflected neutral axis at each blade station towards the blade tip. The positive y axis is defined by the principal axis orientation. The positive x axis is orthogonal to the y and z and follows the right hand rule. For output loads, the origin of the axes is on the neutral axis at each local deflected blade station. (see diagram below)
![[Pasted image 20250610111507.png]]Blade principal axes coordinate system
Note that there is a subtle difference between the “principal axis” frame and the “blade local element frame”.
The “blade local element frame” is orientated so that the X vector in this coordinate system points directly between adjacent nodes on the blade. The other two coordinate system vector directions are determined by the “principal axis twist” angle. This is explained in more detail in DNV GL technical note UKBR-110052-T-31-A
The “principal axis” frame is used for load output in Bladed. The principal axis orientation is calculated by taking the average orientation of the two blade elements at the node where the elements join. This is illustrated below. The two adjoining local element frames are shown in green and red. The principal axes output frame is shown in blue.
Note that the element local coordinate system has its x direction along the element, unlike the “principal axes” coordinate system which has z along the element axis.
Relationship between blade "local element axes" and "principal axes coordinates"
Root axes: The orientation of the axes is fixed to the blade root and does not rotate with either twist or blade deflection. The axis set does rotate about the z axis with pitch. For output loads, the origin of the axes is on the neutral axis at each local deflected blade station.
