The performance was similar to that of the PR XI .
The pressurised cockpit meant that this version could stay at altitudes of over 40,000 ft for longer without the exhausting physiological effects experienced by the pilots of unpressurised cockpits .
The performance was similar to that of the PR XI although the pressurised cockpit meant that this version could stay at altitudes of over 40,000 ft for longer without the exhausting physiological effects experienced by the pilots of unpressurised cockpits .