Don't think I caused this problem but I certainly have to deal with it - gear door closed before gear retracted in flight - no accident but could have been if the gear had strongly jammed into retract such that low pressure on extension might not have been sufficient to permit extension; possible prop strike. 

 

Didn't know of this condition until I was safely on the ground - didn't use the emergency gear extension - nor did I flip the gear-pressure-release valve - don't think I changed anything from the careful routines that I have used in dozens of previous flights.  So what might have caused this scenario?  What must be done to prevent it in the future (besides "not flying")?  Thanks for your comments.   Greg Nelson