Front view
(early version)
ACES 5 - Next Generation Ejection Seat
ACES 5 NGES
ACES 5 - Next Generation Ejection Seat
ACES 5 NGES
The ACES 5 is the result of a lineage of a branch of ejection seats that began with the Aircrew Common Ejection Seat in the 1970s to produce a more effective,
standard seat for USAF aircraft. The ACES and ACES I seats were prototype/development seats that built on the legacy of the ESCAPAC-series that had been around
for decades before. The ACES 5 builds on the evolution of the ACES II series that went through decades of service with several evolutionary changes on the same
basic structure. The ACES 5 differs in terms of arm restraint and head and neck protection systems that reduce the risk of aircrew injuries during high speed ejections.
The ACES 5 returns to the design roots of the ACES prototype in some ways with a modular structure that allows the seat to be removed in sections, allowing for maintenance without the removal of the canopy. THe segements are also therefore a lower weight reducing risk of strain injury.
Parts commonality with the ACES II series is also high with about 85% of the components used in both seat designs. This minimizes the load on the procurement system and logistics.
Aircrew Protection
The YF-22 and F-22 ACES II introduced an arm net system designed for high speed ejection risk reduction which resembled the F-104 C-2 style nets, with significant improvements. These nets were designed to keep the upper limbs within the width of the seat area, however this required the arms to be captured during the deployment of the nets as part of the pre-ejection sequence. This often was difficult due to arm position, fabric friction, and other factors. The ACES 5 nets use a different concept where intent is to allow the capture to occur more 'naturally'. As the occupant's arms are free to move they are caught in the 'spiderweb' that prevents them from overextending and limits the injury potential. These are deployed on two arms per seat side. The arms are latched into place and deployed by a set of lanyards on either side of the seat. The nets are covered by a fabric cover until deployment.The headrest is designed to catch the helmet of the aircrew by a set of arms on either side of the helmet to prevent windblast from pushing the head away from the support to either side, and a tilting surface prevents the head from forcibly impacting the headrest surface under the effects of windblast. This also limits the effects of helmet lift due to high speed airflow.
Rounding out the aircrew protections are passive leg restraints. These are mounted on the seat bucket and are routed around the leg tunnels under the instrument panel. The ends of these are connected to the floor of the cockpit under the seat. During ejection motion the lines are retracted by the seat motion and pull taut around the aircrew's calves. This helps prevent leg lifing and flail.
The seat shown are in the configuration for a center-pull handle. Note the thigh guards are vented to allow airflow. This is important to prevent capture of airflow which can increase the pressure on the structure during high speed ejections. The arm nets and head restraints are similarly minimalist in terms of drag or pressure increases. Structure and Componants The ACES 5 structure differs primarily from prior versions of the ACES II family in the modularity of the design. With a removable seat pan area and separate structures for the back support and drogue chute pack the system allows for removal from the cockpit without removal and replacement of the canopy. In a way this is returning to the roots of the ACES series where the original concept and tested design was also heavily modular. Removal of the seat bucket requires removal of two bolts and a few connectors which makes it a fairly rapid procedure.The seat back module contains the headrest, seat back section and the arm restraints. Other modules include the drogue chute that no longer uses a controller drogue for faster deployment, the main parachute container, and the modernized ACES seat sequencer. Removal of the seat from the rails requires using a tool to unlatch the seat back from the roller assemblies. The roller assemblies are retained in the seat rails allowing the seat back to be lifted out without having to be rolled to the top of the rails.
The seat bucket section contains the survival kit as normal as well as the STAPAC underseat rocket which is used to limit the pitch of the seat during the propulsion stage of the ejection. This is the same STAPAC as used on the ACES II and other seats.As the seat bucket is designed for handling differently than the previous seats shield covers protect the STAPAC during out of cockpit handling. A Trajectory Divergence Rocket (TDR) is also fitted to the side of the base of the bucket.
The drogue is rocket deployed instead of using the drogue gun of the prior seats. The rocket uses a dual nozzle system giving the mount an oval cross-section. In order to control the deployment at extreme speeds the chute uses a reefing system to limit the opening of the parachute skirt. It also utilizes a drogue line attachment system that uses 'tears' itself out as the drogue is inflating. This acts as a shock absorber on the opening shock of the drogue to prevent the drogue from blowing out. The drogue rocket is inset into a slide slot inside the back of the seat structure.Another modification from the earlier ACES II is the Oxygen handle that was added in order to make it easier for aircrew in cold weather gear to find and actuate the emergency oxygen bottle.
Maintenance Improvements Improvements for the maintenance team include the relocation of the seat initiators to the inside of the seat buckets on the side frames. This required a redesign of the handle pull system. A key requirement of this redesign was to maintain the same pull forces on the seat firing handles. Access to the initiators is made by lifting the seat pan lid, removing the survival kit, if fitted, and opening the internal acces panels. The seat back access has also been improved by redesign to allow for the seat back panel to be removed by about 12 screw (the seat shown is an earlier configuration with a larger number. The screws are captive to prevent them becoming FOD if maintenance is done in the cockpit. The panel removal allows for access to many of the seat componants. The parachute box can also be removed easily due to the addition of seat side release for the new parachute mortar. The maintainer safes the pitots and then can use the release to unlatch the box and remove it.I'd like to thank the Collins Aerospace team that gave me access to the seats, allowed me to take photographs and freely answered questions on the design and operation to the best of their abilities.
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