Typical Cabin Pressurization Schedule for a Fighter
The A7-E has an air-conditioning systems that maintains the cockpit environment at a specified temperature and pressure. The conditioned air enters the cockpit through a flow control valve and is distributed to vents around the canopy and window areas. The cabin pressure is maintained by a cockpit pressure regulator, which releases air into the nose cone of the aircraft to maintain the specified pressure as detailed in the graph shown below (A7E NATOPS Manual Section I - The Aircraft).
This pressurization schedule has the cockpit unpressurized from sea level to 8,000 feet. Above 8,000 feet, and up to 23,000 feet, the cockpit is kept at 8,000 feet. For any altitude above 23,000 feet a 5 psi differential is maintained between the cockpit pressure and the flight altitude pressure.
The cockpit altitude is displayed on a gauge on the forward console.
The cabin pressurization is regulated when the cabin pressurization switch is in the CABIN PRESS position, and will be dumped in the CABIN DUMP position. Essentially, all air to the air conditioning turbine is shut off. There is also an emergency vent air knob for ventilation, that can also be used to reduce cabin pressure.
Regulations required pilots to be on oxygen from start-up to shut-down.
Managing Oxygen & Pressurization
I volunteered to go ashore in Greece to be a liaison between NATO forces there and the USS Nimitz. They were concerned about US aircraft entering Greece airspace to conduct their scheduled missions, while Turkish fighters were also violating the same airspace. I was to be ferried in an S3.
I was in the back seat in the TACCO (tactical officer) position on the right-hand side. We had taken the catapult shot and were climbing out. I was talking with the crew member across from me in the SENSO (sensor operator) seat when he asked me how I felt. "Dizzy," I said. He pinched a fingernail and told me he was going to checkout the pilot and copilot. He came back and said they had lost cabin pressurization, and that we needed to put on our oxygen masks. I had been flying for so many years with the oxygen mask always strapped to my face that I never paid attention to the signs of hypoxia. It always amazed me all the various ways one could get in trouble airborne.