Tail cone access
I worked for Trans World Airlines (TWA) in the early 1970s at Kennedy Airport as an Electronics Mechanic. I worked on navigation, communications, control, and entertainment systems. Although I worked on a variety of aircraft, it was the Boeing 707 I worked on most often.
One of the jobs I had to do infrequently was crawl into the tailcone to work on the electronics that controlled the yaw damper. The yaw damper was a servo that moved the rudder in response to an accelerometer or gyroscope that measured yaw rate. It's purpose was to suppress an instability in the 707 called a “Dutch Roll.”
Here's a photo showing the tail cone access with its panel removed. It's the nearly square hole just below the center of the photo. It's barely large enough to allow someone to enter.
I wasn't clostrophobic, but crawling into the tail cone was a worrying experience. There's a story of an aircraft mechanic who was stuck in the tail cone after someone had replaced the access panel without checking to see if anyone were inside. The tailcone is unpressurized. If you were in there while the plane was in-flight, you would die just like those wheel-well stowaways.
You can't remove the access panel from the inside without doing some damage. So, he banged on the fuselage. Nobody heard his banging amidst the noise of the busy JFK airport ramp.
When the aircraft began taxiing, the mechanic got out his wire cutters and cut the safety wire on the electrical connector for the jackscrew motor assembly. When he unplugged the connector, the cockpit crew noticed the “fault” and returned to the gate.
After hearing that story, I hung a bright red ribbon from the opening when I had to work in the tailcone.