'locked' cockpit canopies

[rafair]

I have a recollection that, on one of the early photographic reconnaissance aircraft, the pressurisation system dictated that the cockit canopy was locked and could only be opened on the ground.   Am I right or wrong?

[Hagar]

You might be thinking of the high altitude Spitfire Mk VI. I think the canopy could be jettisoned in an emergency. http://www.cybermodeler.com//hobby/kits/tru/kit_tru_2413.shtml

[rafair]

Thank you Hagar.       I knew I'd read it somewhere.