Differential cross sections for elastic He scattering at energies in the range of MeV and proton analyzing powers of this process are calculated on the basis of the Glauber diffraction model with allowance for the spin dependence of nucleon–nucleon amplitudes. Explicit expressions are obtained for the first time for all six invariant amplitudes of He scattering for the mechanisms of single, double, and triple incident-proton scattering off target nucleons. Good agreement with experimental data is found both for the cross sections and for spin observables in the forward hemisphere of scattering angles. Also, explicit expressions are obtained for He-scattering amplitudes violating time-reversal ( ) invariance but preserving spatial parity ( ). These expressions can be used in testing invariance in this and other processes.