Tell your Mom that your young mind is still very pliable. Tell her that if you don't get some science stimulation soon in the way of experimentation, you may reallocate that part of your brain to Gangsta Rap.
Now on to Airplane doors.
Q. How do airplane doors work?
A. There is no easy answer here because there are many different door designs. I'm actually somewhat familiar with them because I used to design machines that loaded cargo into aircraft.
Now since you are becoming a prodigy in Mechanical Engineering, I can run through this pretty fast. Some of the doors are moved with hydraulic cylinders, some are moved with pneumatic cylinders. For the most part latches on aircraft doors (the part that keeps it closed) are purely mechanical (no electric, pneumatic, or hydraulic latch). This way a loss of pneumatic pressure or hydraulic pressure won't cause the door to come open. Doors coming open on airplanes flying 500 miles per hour would be a BAD thing.
The pilot has indicator lights so he can tell if the door is open before he takes off. I don't know this for sure but there are also probably safety interlocks on the doors. Interlocks are cool and sometimes ingenious features that engineers add to complicated machines to help prevent people from being boneheads. They probably have the doors interlocked with the gages in the cockpit so that it does not allow you to open the plane door when you are high in the air or traveling at 500 mph.
Unfortunately you can't build an airplane door in your back yard. You can however, see the inner workings of a similar door. Hop in the car with your Mom and go to 7-11. Let your Mom drive. Buy three Mountain Dews. Now drive to a bank. Your Mom may already know of one that has a vault with glass on the inside of the door. Offer the bank manager one of the three mountain dews if he'll let you look at the back of the door up close.
If he says no, tell him a mechanical engineer told you it was imperative for your brain development.
When you're done looking at the door, bust out the other two Mountain Dews on the way home.
Then carefully drop the hint: we COULD stop by Radio Shack......
— The World’s Best Mechanical Engineer
Also in this series:
• holy hydraulics, batman!
• solenoid spectacular
• springs & things
• the world's best mechanical engineer explains it all for you