I'm not a military person, but I would imagine that the reason the canopy on fighter planes are left up all the time would have more to do with easier ingress in an emergency situation, rather than the life of the bars. The same way that fire trucks are parked in their garage spaces with their doors left open all the time. Besides that, I believe a past post here on the list stated that parking with the doors open would do more damage to the door seal pushing against the T panel, than any benefits that the torsion bar, or the gas struts may recieve. Besides that, if a torsion bar is unavailable for the application, perhaps a torsion spring could possibly replace it. Matter of fact, I'd bet on it! -Robert vin 6585 "X" --- In dmcnews@xxxx, john fredt <hecklerkochgmbh@xxxx> wrote: > > > Yes the temperature changes in normal weather are enough to affect the life of these bars.Simply because they were once cryogenically frozen doesnt exempt them from the normal contracting and expanding with summer heat and winter cold.Ever notice that fighter jets are stored with the canopy open most of the time? <SNIP>