  Spin raising and lowering operators for massless field equations constructed
from twistor spinors are considered. Solutions of the spin-$\frac{3}{2}$
massless Rarita-Schwinger equation from source-free Maxwell fields and twistor
spinors are constructed. It is shown that this construction requires Ricci-flat
backgrounds due to the gauge invariance of the massless Rarita-Schwinger
equation. Constraints to construct spin raising and lowering operators for
Rarita-Schwinger fields are found. Symmetry operators for Rarita-Schwinger
fields via twistor spinors are obtained.
