I stumbled on this picture on the internet somewhere. It's a shot of an F-4 Phantom in full afterburner chained down to the tarmack. When I was 18 years old and just a few months in the service, I stood in this same spot.
There are 4 little Schrader valves ( like on your valve stem of your bike tire) that are connected to each of the Fuel Boost pumps located in a little access door on the belly of the plane- so you can check the pump output pressures.
The plane we were troubleshooting was chained down by the tail hook in the Hush House on the flightline at Spangdahlem. The Hush House is a hanger that has a giant muffler on the ass end of it that we park the plane in and run it without pissing off the locals with all the noise. Armed only with a pressure gage and double hearing protection, I waited for the crew chief in the cock pit to give me the thumbs up and I approached the plane at a 90 degree angle from the side, just behind the intake. The whole world is shaking. I could see the multiple blue rings of the afterburner stages, not 20 feet away from me to the left, and the cold, high pitch screech of the air being sucked into the intake about 6 feet to my right. I have only about 15 seconds to get in there, take the pressures, remember each of them, and get the fuck out the same way I came in. If you stand under there too long you could get vertigo from the sound. No time to fuck around. No margin for error.