Exceptional sequences of line bundles on projective bundles

For a vector bundle $\mathcal E \to \mathbb P^\ell$ we investigate exceptional sequences of line bundles on the total space of the projectivisation $X = \mathbb P(\mathcal E)$. In particular, we consider the case of the cotangent bundle of $\mathbb P^\ell$. If $\ell = 2$, we completely classify the (strong) exceptional sequences and show that any maximal exceptional sequence is full. For general $\ell$, we prove that the Rouquier dimension of $\mathcal D(X)$ equals $\dim X$, thereby confirming a conjecture of Orlov.