  We solve the minimum-thrust optimal trajectory generation problem for the
transition of a tiltwing Vertical Take-Off and Landing (VTOL) aircraft using
convex optimisation. The method is based on a change of differential operator
that allows us to express the simplified point-mass dynamics along a prescribed
path and formulate the original nonlinear problem in terms of a pair of convex
programs. A case study involving the Airbus A3 Vahana VTOL aircraft is
considered for forward and backward transitions. The presented approach
provides a fast method to generate a safe optimal transition for a tiltwing
VTOL aircraft that can further be leveraged online for control, and guidance
purposes.
