  We investigate the orientation of the magnetic field deflections in
switchbacks (SB) to determine if they are characterised by a possible
preferential orientation. We compute the deflection angles of the magnetic
field relative to the Parker spiral direction for encounters 1 to 9 of the PSP
mission. We first characterize the distribution of these deflection angles for
calm solar wind intervals, and assess the precision of the Parker model as a
function of distance to the Sun. We then assume that the solar wind is composed
of two populations, the background calm solar wind and the population of SB,
characterized by larger fluctuations. We model the total distribution of
deflection angles we observe in the solar wind as a weighed sum of two distinct
normal distributions, each corresponding to one of the populations. We fit the
observed data with our model using a MCMC algorithm and retrieve the most
probable mean vector and covariance matrix coefficients of the two Gaussian
functions, as well as the population proportion. We first observe that the
accuracy of the spiral direction in the ecliptic is a function of radial
distance, in a manner that is consistent with PSP being near the solar wind
acceleration region. We then find that the fitted switchback population
presents a systematic bias in its deflections compared to the calm solar wind
population. This result holds for all encounters but E6, and regardless of the
magnetic field main polarity. This implies a marked preferential orientation of
SB in the clockwise direction in the ecliptic plane, and we discuss this result
and its implications in the context of the existing switchback formation
theories. Finally, we report the observation of a 12-hour patch of SB that
systematically deflect in the same direction, so that the magnetic field vector
tip within the patch deflects and returns to the Parker spiral within a given
plane.
