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Oct 9, 2011

ACES II Ejection Seat

"The ACES II (Advanced Concept Ejection Seat) is considered a smart seat since it senses the conditions of the ejection and selects the proper deployment of the drogue and main parachutes to minimize the forces on the occupant. The seat is a derivative of the Douglas Escapac seat. Removal from the aircraft is by a three part pyrotechnic sequence. A gun catapult provides the initial removal of the seat from the aircraft. A rocket sustainer provides zero/zero capability to the seat. To prevent the seat from tumbling when the aircraft is in a roll maneuver or there is a center of gravity imbalance, another (smaller) rocket called a STAPAC is attached to a gyroscope. This senses the motion and attempts to keep the seat from spinning by automatically providing a correcting force.

F-16 ejection sequences

Once clear of the aircraft, the pitot - static system on the seat measures the conditions and selects one of three operating modes depending on the conditions present at egress."

"Mode 1 - Low speed (<250 knots) and low altitude (<15 000 feet) operation. The main parachute deploys as the seat clears the rails. Drogue parachute remains undeployed to prevent line tangle."

"Mode 2 - Moderate speed (250-650 knots) and low altitude (<15 000 feet) operation. Drogue parachute deploys as the seat leaves the rails. Main parachute deploys 0.8 to 1.0 seconds after the drogue. Drogue chute is then released to prevent line tangle."

"Mode 3 - High speed (250-650 knots) and high altitude (>15 000 feet) operation. Drogue parachute deploys as the seat leaves the rails. The pitot - static system senses the conditions and delays the main parachute until mode 2 conditions are met. Then the main parachute deploys after 0.8 to 1.0 seconds. Drogue chute is then released to prevent line tangle. " /3/

ACES II parts and controls

"The Advanced Concept Ejection Seat (ACES) Was developed to provide a standard Ejection seat to be utilized in all United States Air Force jets from the mid-1970s. It was first flown in a A-10 Thunderbolt II from the Fairchild Republic Co. at the Farmingdale Long Island (N.Y.) plant in April 1978. The driving reasons for the development of the ACES II were to standardize on one type of ejection seat*- this would lead to reduction in training of both mechanics and pilots, also the design was intended to provide better performance in low altitude/adverse attitude conditions as well as to improve high speed seat stablity. It also allowed the government to purchase larger lots of spare parts." /1/

"The ACES-II ejection seat produced by McDonnell Douglas Aerospace is the seat installed in the F-16. The same seat is also used in the F-15, F-22, F-117 and A-10 but has small differences, mainly because the F-16 has the flightstick located at the right side, while the other aircraft have the stick located at the center, between the pilot's legs." /2/

"The ACES-II is a Zero-Zero seat. That means that the seat is still capable of ejecting the pilot at a 0 kts speed. The seat has the following parts: the case itself, the control-electronics, the parachute container that holds the pilot's parachute, the survival kit assembly according to the area of operation, the emergency oxygen assembly and the ejection mechanism itself." /2/

"The seat is installed in the cockpit in a 30 deg. angle. This position allows the pilot a better resistance to pulled G's as the position is not completely vertical." /2/






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