The D-ring at the front center of the seat is cable connected to an initiator under the seat pan. The cable is spring mounted to prevent injuries after ejection and prior to seat separation at which time the cable is severed. When pulled, the initator gas is routed to the inertia reels to retract the crewman back upright. It is also routed to the foot restraint reels and via a quick disconnect fitting to the canopy removal system. As the canopy is jettisoned, an initiator in the canopy system is actuated and gas from it is directed back into the seat via another quick disconnect to actuate the gas-operated sequencing system, and to fire the catapult after a 0.3 second delay to allow the canopy to clear the area.

The Drogue chute is mounted in the headrest with the drogue gun mounted in the center of the rails behind it. It is fired 0.2 seconds after the gas from the canopy system begins the sequencing, at about the same time as the seat clears the aircraft rails. At that time, the rocket section of the rocket/catapult (ROCAT) is being ignited by gas from the catapult portion. Other portions of the seat system actuated by the canopy initiator include the arming of the pyrotechnic aneroids which sense altitude by air pressure and continue the seat sequencing when the seat is below 15,000 feet. Also, gas arms the lower drogue attach point cutters which will sever the lower riser lines 10.0 seconds later. This will allow the seat to decellerate, then the cutters will allow the seat to swing down under the 6.2 foot drogue decending in a controlled fashion until the aneroids fire at 15,000 feet.

When the aneroid units continue the seat separation, the following events happen:

• Inertia reel straps are severed
• Inertia reel is unlatched to allow the straps to unspool if the severance cutters failed
• Lap belt is released at the seat attach points
• Foot restraint cables are severed
• D-ring handle cable is severed
• Seat separation reel is gas actuated
• Parachute lanyard is pulled as the man and seat separate
• Drogue upper riser cutters are armed via a 0.3 second delay

After separation, the survival kit is retained by straps connected to the crewman's harness on each hip. It is manually deployed by pulling the curved yellow handle inboard on the right side of the seat pan. The yellow and black striped handle barely visible under the oxygen connections in this picture is the manual scramble handle which mechanically and pyrotechnically executes most of the seat separation functions to allow the crewman to either egress the aircraft on the ground, manually bailout from the aircraft, or manually separate from the seat in case of a seat separation failure. The scramble handle disconnects the lanyard on the parachute so that it must be manually actuated by the D-ring on the left riser if the parachute is needed.

The yellow cover barely visible on the left of the seat bucket protects the secondary catapult T handle. This handle is used if there is a failure of the seat to fire normally. The canopy must be jettisoned prior to using this handle as the seat will fire immediately on pulling the T handle. To prevent the T handle from being used as the primary handle, the D-ring must be pulled first to arm the T handle.

The yellow pyrotechnic hose visible on the left side of the seat near the headrest is the Rocket Catapult connection. In case of a crash, the crash rescue crew would sever that line with bolt cutters to prevent accidental firing of the rocket while rescuing the crewman.

The SR-1 seat has a few known variants, the most common of which is the seat used in the later model U-2 aircraft including the U-2R, TR-1, and ER-1 That variant is know by the designation RQ201. The main modifications for the RQ201 are the secondary ejection handle has been relocated to the left side, and the double-d ring is replaced with a single loop d-ring. A SR-1 variant was also used in the Enterprise and Columbia Space shuttles. The Shuttle seats were fitted for the landing tests at Edwards AFB, and for the first four flights (STS-1, STS-2, STS-3, and STS-4) in orbit. The Shuttle version had a tilting back to position the pilots closer to the instrument panel while the shuttle was on the pad. This seat, with the necessary pressure suit (the shuttle astronauts, SR-71, and U-2 pilots all use David C. Clark suits) is the highest altitude/ highest airspeed rating in current United States service. Even though the seats are rated for high speed, they are not High Dynamic Pressure seats. High dynamic pressure (High-Q) is a function of air density as well as speed. The SR-71 flys at high altitudes where the air pressure is significantly lower, lowering the dynamic pressure. The SR-71 flying at 2000mph at near 80,000 feet is actually experiencing wind force more equivalent to about 460 MPH (400 Knots Equivalent Air Speed {KEAS}). Aircraft such as the FB-111 were designed for higher speeds down in the thicker atmosphere, and thus experience a much higher 'Q' or dynamic pressure.