STENCEL SJU-8/ A EJECTION SEAT
Learning Objective: Recognize the components, parachute and seat separation operations, seat subsystems, component maintenance, corrosion control, and lubrication and emergency cleaning procedures for the Stencil SJU-8/ A ejection seat.
The Stencel SJU-8/ A ejection seat is used in the A-7E aircraft. It uses thrust from a ballistic catapult and two seat-back rockets to propel it from the aircraft. (See figures 6-29, 6-30, and 6-31.) The seat provides escape capabilities during takeoff and landing emergencies from zero speed and zero altitude to speeds and altitudes of 600 knots and 50,000 feet. The system incorporates a seat-mounted, environmentally protected parachute, survival package with raft, emergency oxygen supply, and emergency locator beacon. The parachute is stored in a non-adjustable headrest. The front surface of the seat bucket provides a buffer for the calves of the legs, which are automatically restrained by straps to prevent flailing during ejection. The sides of the bucket extend upward and forward from the seat to protect the legs during canopy penetration.
Figure 6-29.- SJU-8/ A ejection seat assembly.
Figure 6-30.- SJU-8/ A ejection seat assembly (front view).
Figure 6-31..- SJU-8/ A ejection seat assembly (back view).
The Stencel system has four modes of operation. As you read the material in the following paragraphs, carefully note the differences between these modes. The material describing the sub-systems and components will amplify the modes of operation by explaining how and when each mode is activated. The remainder of this section will address the test equipment and test procedures used in the maintenance of the system.
The ejection sequence is initiated by pulling upward on the ejection control handle, which is located on the front panel of the seat bucket. Pulling the ejection control handle requires a force of 15 to 25 pounds through a distance of less than 4 inches. Pulling the control handle fires two M99 ejection initiators, which release hot, high-pressure gas to the ballistic signal transmission system (BSTS). Figure 6-32 is a schematic of the BSTS. The right M99 ejection initiator supplies gas pressure to the right side of the catapult cartridge igniter and the inertia reel gas-generating initiator. The left M99 ejection initiator supplies gas pressure to the left side of the catapult cartridge igniter, thereby
Figure 6-32.- SJU-8/ A ballistic signal transmission system.
providing redundant ignition to the catapult cartridge. As the seat catapult fires, the gas pres-sure forces locking pistons in the catapult tubes to disengage the locking balls, which unlock the inner -and outer catapult tubes. As the seat and outer catapult tubes move upward, the pilot's legs are drawn against the front of the seat by the leg restraint mechanism. Simultaneously, the quick-disconnect fittings for pilot services are separated, and a lanyard on the catapult manifold activates the emergency oxygen bottle, IFF, and AN/ URT-33 emergency radio beacon.
After approximately 16 inches of seat travel, gas pressure is applied to the drogue gun pistons housed in the catapult tubes. These pistons forcibly expel the drogue parachute container for quick drogue parachute deployment. The drogue parachute provides seat stability and aids in withdrawing the main parachute.
After approximately 31 inches of seat travel, gas pressure is ported to a thruster (pin puller), a 3-second time-delay initiator, a multiple time-delay (0.1-and 1.3-seconds) initiator, and the igniters of the two seat-back rocket (SBR) motors. The SBRs produce the thrust necessary for the seat and pilot to attain sufficient terrain and aircraft tail clearance to permit parachute deployment. The necessary thrust is available even at zero airspeed and zero altitude.
Upon ejection, the seat is stabilized by a Directional Automatic Realignment of Trajectory (DART) system. Two lanyards, attached to the aircraft and feeding through tension brake assemblies beneath the seat, counteract excessive pitch and roll.
The post-ejection sequencing system for deploying the Wind Oriented Rocket Deployment (WORD) motor and drogue release mechanism follows one of four automatic ejection modes, depending on the aircraft's airspeed and altitude. These modes of operation will be discussed later in this chapter. Depending on the mode of operation, the time-delay initiators fire, directing gas pressure to actuate the WORD motor and drogue release mechanism, and arm the aneroid-actuated initiator.
Upon actuation, the WORD motor/ drogue release disconnects the WORD rocket motor. This allows the wind resistance on the drogue chute to withdraw the WORD motor from the seat. When the WORD rocket motor arming cable is withdrawn, it releases the firing pin and ignites the rocket. Depending on the mode of operation, the aneroid actuated initiator fires. This activates the personnel parachute container opener, releasing the personnel parachute. The parachute will be withdrawn by either the WORD rocket motor, drogue parachute, or internal pilot chute.
When the personnel parachute suspension lines and risers become taut, a firing lanyard attached to a ballistic spreading gun extracts the spreading gun firing pin sear. The re-leased firing pin strikes and activates a spreading-gun ballistic charge, which expels metal slugs in a 360-degree pattern. The slugs, attached to parachute suspension lines, rapidly inflate the canopy during very low-speed ejection. During high-speed ejection, the air-stream energy far exceeds that of the spreading gun. Therefore, the gun has little effect on parachute inflation time. As wind resistance acts on the personnel parachute, tension on the seat and man release lanyards actuates the seat and man separation initiator to produce gas pressure directed to the guillotine. The guillotine severs both inertia reel straps and releases the pilot's upper torso. Simultaneous actuation of seat and man separation mechanical linkage by the lanyards releases the survival kit assembly and pilot from the ejection seat.
The pilot may release the survival package in the survival kit by pulling a handle located near his right hip. After the package drops 12 feet, a snubbing lanyard initiates inflation of the life raft. The remainder of the survival package drops an additional 13 feet and hangs below the life raft to stabilize it during descent.
Ejection Mode Sequences
The Stencel seat is equipped with a mode sequencing system that controls four automatic ejection modes. The system includes a parachute container opener that is activated by gas pressure from the 7,000-or 14,000-foot aneroid initiators, or the seat and man separation initiator. The WORD rocket is also part of the system. The WORD rocket, mounted on the back of the seat, is connected to the drogue bridle assembly on one end and to the parachute WORD bridle on the other end. The WORD rocket motor is released from the seat and fired by a lanyard as it falls away from the seat during low-speed ejections or by the pull of the drogue during high-speed ejections. The ejection sequence follows one of four modes, depending on aircraft airspeed and altitude. Mode 1 includes ejections where the air-craft is operating below 7,000 feet and at a speed less than 225 knots. Mode 2 includes an altitude below 7,000 feet, but at a speed greater than 225 knots. Mode 3 occurs above 7,000 feet, but below 14,000 feet, at any airspeed. Mode 4 occurs above 14,000 feet at any airspeed. Figure 6-33 presents a comparison of the various modes.
MODE I.- Mode 1 (fig. 6- 34) is for a low-speed, low-altitude ejection. After the catapult outer tube assemblies have travelled upward a distance of approximately 31 inches, ballistic gases are ported through the inner trombone assemblies to actuate the 0.1-and 1.3-second time delays in the multiple delay initiator and the 3-second delay initiator. Gases from the 0.1-second delay actuate the drogue and WORD release and arm the 14,000-foot aneroid initiator. Below 14,000 feet, the initiator immediately actuates and gases pass through the right trombone to actuate the parachute container opener. Upon actuation of the WORD motor and drogue release assembly, the aerodynamic drag of the drogue parachute
Figure 6-33.- SJU-8/ A mode of operation.
pulls the WORD motor away from the seat back are attached to alternate suspension lines on This action extracts the firing lanyard from the parachute canopy skirt in a 360-degree motor and ignites the WORD motor. This opens the parachute and allows the canopy to fill quickly. If the spreading gun fails When the WORD rocket is fired, it extracts to fire, a fail-safe collar releases the slugs and the parachute from its container. The parachute allows normal parachute inflation. If mode 1 fails, drag pulls a lanyard that fires the ballistic mode 2 will automatically provide the ejection spreading gun. The gun expels metal slugs, which sequence.
Figure 6-34.- Mode 1: low speed/ low altitude.
MODE 2.- Mode 2 (fig. 6-35) is for a airspeed is above 225 knots. The flow of gases high-speed, low-altitude ejection. The primary is delayed until the 1.3-second delay initiator fires. initiation of the mode 2 sequence is identical to This delay reduces the parachute's opening shock. that of mode 1. To reduce parachute opening When the 1.3-second delay initiator fires, the loads, the drogue decelerates and stabilizes the ballistic gases are directed to the 7,000-foot seat before the parachute opens. In mode 2, the aneroid-actuated initiator. Since the altitude is output of the 0.1-second initiator is blocked by below 7,000 feet, the initiator fires. This actuates the low-speed selector valve (LSSV) because the WORD motor and drogue release assembly
Figure 6-35.- Mode 2: high speed/ low altitude.
and operates the parachute container opener 14,000 feet) ejection, which may occur at any assembly. The remainder of the mode 2 sequence airspeed. The primary initiation of the mode 3 is identical to the mode 1 sequence. If the mode sequence is identical to that of mode 1. At 2 sequence should fail, then the mode 3 sequence ejection, the airspeed and altitude sensors and automatically provides the ejection sequence. low-speed selector valve (LSSV) block the gases from the 0. l-second delay initiator. The MODE 3.- Mode 3 (fig. 6-36) is an 1.3-second delay initiator fires and arms the intermediate altitude (above 7,000 feet and below 7,000-foot aneroid initiator, which is delayed
Figure 6-36.- Mode 3: intermediate altitude.
because ejection occurs above 7,000 feet. When mode 3 fails, then mode 4 automatically provides the 3-second delay initiator fires, its gases actuate the ejection sequence, the drogue and WORD release and arm the 14,000-foot aneroid initiator. MODE 4.- Mode 4 (fig. 6-37) is an ejection occurs below 14,000 feet, the initiator fires above 14,000 feet at any airspeed. The primary immediately through the right trombone to initiation of the mode 4 sequence is identical to operate the parachute container opener. The that of mode 1. At ejection, the ballistic gases remainder of mode 3 is identical to mode 1. If from the 3-second delay initiator actuate the
Figure 6-37.- Mode 4: high speed/ high altitude.
WORD motor and drogue release assembly and arm the 14,000-foot aneroid-actuated initiator. Meanwhile, the 1.3-second delay initiator arms the 7,000-foot aneroid-actuated initiator, which acts as a backup. The seat and pilot, which are stabilized by the drogue parachute, descend to 14,000 feet pressure altitude. At that point, the 14,000-foot aneroid-actuated initiator fires, actuating the personnel parachute container opener assembly. The personnel parachute assembly is then deployed by the aerodynamic forces acting on the drogue parachute assembly. Should either the 3-second delay initiator or the 14,000-foot aneroid-actuated initiator fail, the sequence would proceed as described above, except that free fall would continue to 7,000 feet pressure altitude. There, the 7,000-foot aneroid-actuated initiator would actuate the personnel parachute container opener assembly. The personnel parachute assembly would then be deployed by the drogue parachute assembly.
Emergency Parachute Operation and Seat Separation
If all automatic modes fail after the seat is ejected, the emergency release handle may be used for parachute deployment or seat and pilot separation. Operation of the emergency release handle overrides all automatic modes, but it should not normally be used above 14,000 feet. Upon actuation, mechanical linkage fires the seat and man separation initiator directing ballistic gas to the inertia reel strap guillotine. The guillotine severs two straps and releases the pilot's upper torso restraint. Ballistic gas also actuates both the WORD motor and drogue release assembly and the parachute container opener assembly. The personnel parachute assembly is then deployed by the drogue and the WORD motor, depending upon airspeed at the time of manual override initiation.
Figure 6-38.- Safe/ arm control assembly and link.
There are several functional subsystems of the Stencel SJU-8/ A ejection seat. The subsystems are described in the approximate order in which they operate in the ejection sequence.
Safe/ Arm Control Assembly and Link Subsystem
The safe/ arm control assembly and link sub-system (fig. 6-38) places the seat in either a safe or an armed condition. The subsystem safeties three mechanically actuated M99 initiators when the seat is not occupied or when it needs to be kept in the safe condition. For the safe position, you should pull the knob on the handle to disengage the lock. Then move the handle to the full UP position. The seat is made safe by mechanically positioning a link and plunger, which prevents rotation of the initiation subsystem rotors. It also safeties the linkage that actuates the seat/ man separation initiator. For the armed position, you should pull the knob on the handle and move the handle to the full DOWN position.
Figure 6-39.- Ejection initiation system.
Ejection Initiation Subsystem
The ejection initiation subsystem (fig. 6-39) consists of an ejection control handle, mechanical linkage, and two ejection initiators. Actuation of the ejection control handle, located on the front panel of the seat bucket, mechanically pulls the firing cable, rotating the initiation subsystem rotors, which, in turn, extract a firing pin from each of the two M99 ejection initiators. The out-put gas pressure from either or both of the initiators is transmitted to two igniters, one on each side of the catapult cartridge, the inertia reel gas-generating initiator, the multiple time-delay initiator, and the thruster. The two catapult cartridge igniters provide catapult ignition redundancy.
The catapult subsystem (fig. 6-40) provides seat propulsion throughout the catapult stroke and applies pressure to the drogue pistons that project the drogue parachute and its container up-ward into the air stream. It also provides ballistic gas to initiate seat-back rocket ignition and post-election sequencing operations. This subsystem may be divided into five major parts. These parts are described in the following paragraphs.
CATAPULT CARTRIDGE.- The catapult cartridge provides ballistic gas pressure to boost the seat and pilot out of the cockpit and to expel the drogue container and chute from the seat. The catapult cartridge also initiates ignition of two SBR motors and initiates the post-ejection sequencing subsystem (fig. 6-41).
Figure 6-40.- Catapult system.
CATAPULT TUBE ASSEMBLIES.- The catapult tube assemblies house the catapult lock and unlock mechanism, provide physical support for the seat bucket via the seat height adjustment actuator and slipper assemblies, and support the trombone assemblies. They also support a headrest and personnel parachute container assembly, drogue parachute and container assemblies, and associated interconnecting hardware. The catapult tube assemblies also provide several other functions. First, they provide the energy and movement for the canopy piercers and breakers to penetrate the aircraft canopy. They also route and apply ballistic gas pressure to eject the drogue container and parachute. They route and apply ballistic gas pressure to initiate the seat-back rocket motors. Finally, they route and apply ballistic gas pressure to initiate the gas-operated components of the post-ejection sequencing subsystem (fig. 6-41).
Figure 6-41.- Catapult cartridge and tube assemblies.
CATAPULT LOCK AND UNLOCK MECHANISM.- The catapult lock consists of a lock-ing piston and six locking balls set between the inner and outer catapult tubes. The catapult lock retains the seat in the cockpit during inverted flight. Upon seat ejection, the lock is released by gas pressure from the catapult cartridge. Catapult cartridge gases move the locking piston upward and permit the locking balls to disengage from the groove in the outer catapult tube. This action removes all connection between the inner and outer catapult tubes.
DROGUE CHUTE AND CONTAINER PROJECTION.- When the outer catapult tubes have moved upward approximately 16 inches on the inner tubes, gas pressure is applied to the pistons attached to the drogue container. There is one piston in each outer tube. When the pistons exit the top of the outer catapult tubes, the drogue container and parachute move up and aft of the seat. Then, aerodynamic pressure is applied to the container. This causes stretching of the drogue bridle and loosening of the drogue container flaps. The drogue suspension lines and canopy then emerge while the container and associated hard-ware are jettisoned (fig. 6-42).
TROMBONE ASSEMBLIES.- Two pairs of trombone assemblies are associated with the catapult. The outer trombone assemblies route ballistic gas from two M99 ejection initiators to the catapult cartridge igniters. The inner trombone assemblies route ballistic gas pressure from the catapult tube assemblies to components of the post-ejection sequencing sub-systems and to both seat-back rockets (SBR). They also route ballistic gas pressure from the 7,000-and 14,000-foot aneroid-actuated initiators to the parachute container opener (fig. 6-40).
Sustainer Thrust Subsystem
During either mode 1 or mode 2 operation, two SBR motors provide the thrust necessary to propel the seat and pilot to an altitude sufficient to attain terrain and aircraft tail clearance and to allow personnel parachute deployment and inflation. Each SBR has dual-ignition inlet ports. Ballistic gas pressure from both catapult tube assemblies is ported into both SBRs to provide redundant ignition. This pressure fires internal SBR igniters, which ignite the propellant grain for a burn time of approximately 0.25 second (fig. 6-40).
DART Stabilization Subsystem
The directional automatic realignment of trajectory (DART) stabilization subsystem, com-posed of a bridle, a brake assembly, and two nylon slip lines, provides stabilization for the seat and pilot during low-speed ejections. Stabilization is accomplished by correcting any misalignment of the seat and pilot centre of gravity relative to the SBR thrust centre line. One end of the bridle is permanently attached to the under side of the seat bucket. It acts as a hinge during DART operation. Cables attached to the other end of the bridle restrict the arc of the bridle to a predetermined angle. This ensures optimum operation. Part of each slip line is stowed in a protective fabric housing routed through the brake assembly. The remainder of the two slip lines is stowed in a second protective fabric housing after being routed through fairleads on the bridle aft side. Free ends of the slip lines are attached to the catapult cartridge manifolds of the ejection seat. Slack in the slip line permits the seat to travel through seat tip-off and initial rotation, which results from centre of gravity and thrust centre line misalignment. Tension developed in the slip lines by the brake assembly imparts a correcting moment to the seat and pilot. This is necessary to counteract excessive seat and pilot pitch rotation and also to provide trajectory control.
Post-ejection Sequencing Subsystem
The post-ejection sequencing subsystem includes all gas-operated and cartridge-actuated devices required to initiate operational mode sequencing functions. It also includes the WORD rocket motor, the primary means for personnel parachute deployment in the inertia-WORD (I-WORD) rocket motor deployment sequence of mode 1, and the backup means for the drogue-WORD deployment sequence of modes 2, 3, and 4.
Personnel Parachute Subsystem
Figure 6-42.- Headrest and drogue container assemblies.
The personnel parachute subsystem includes a WORD bridle assembly, riser assemblies with lanyards, spring-loaded internal pilot parachute assembly, main canopy assembly, ballistic spreading-gun assembly, and an override and disconnect assembly. The riser assemblies with lanyards initiate the spreading gun and the seat and man separation. When the parachute container opener is actuated, either one of the two locking clips will disengage and release a ball fitting on the end of a restraining cable. This action allows the container to open and the main canopy assembly to deploy. The canopy assembly is propelled by the WORD bridle, which is acted upon by the force of the drogue and WORD motor. Should the WORD bridle fail, the internal pilot parachute functions as a backup system. When the main canopy and suspension lines are fully deployed, the spreading-gun firing lanyard exerts tension on a spring-loaded firing pin in the ballistic spreading-gun assembly. This pin is withdrawn until the pin-locking balls slip into a groove in the gun housing. Then, the firing pin, driven by spring force, releases, strikes, and fires dual primers that ignite the spreading gun cartridge. Cartridge energy drives 14 pistons (attached to alternate suspension lines), which expel 14 slugs in a 360-degree pattern and spread the main canopy. Should the spreading gun cartridge fail to fire, continued tension on the firing lanyard removes a piston retaining band. This frees the slugs from the spreading-gun housing to allow conventional canopy inflation. During main canopy deployment, tension is exerted on the pilot chute and main canopy by the WORD bridle. Also, during this time, the override and disconnect will secure the WORD bridle to the parachute. If there is no tension on the WORD bridle and the chute has over 10 pounds of drag, the override and disconnect will function to jettison the drogue chute, drogue bridle, WORD motor, and WORD bridle.
Seat/ Man and Survival Kit Release Sequencing Subsystem
The seat/ man and survival kit release sequencing subsystem has four functions. These functions are described in the following paragraphs.
AUTOMATIC RELEASE.- As the person-nel parachute inflates during the ejection sequence, the parachute risers pull on the seat/ man release lanyards. The lanyards rotate the seat pan release rod and fire the seat/ man separation initiator. Gas pressure from the initiator then actuates the inertia reel strap guillotine. Gas is also transmitted to the WORD motor and drogue release assembly and parachute container opener, but these devices will have previously operated. Rotation of the seat release shaft releases the seat pan with the attached survival kit.
MANUAL OVERRIDE RELEASE.- The pilot can override any of the post-ejection sequences by actuating the emergency release control. When it is actuated, a mechanical linkage fires the seat and man separation initiator. This directs ballistic gas to the inertia reel strap guillotine, which severs the two straps. With the straps severed, the pilot's upper torso restraint is released. Ballistic gas also shuttles the WORD motor, drogue release assembly, and the parachute container opener assembly. The personnel parachute assembly is then deployed by the drogue or the WORD motor, depending upon the airspeed at the time of manual override initiation.
GROUND EMERGENCY EGRESS.- When the emergency release control is pulled, it rotates the seat release shaft and releases the seat pan with attached survival gear from the seat. The control also operates the linkage that fires the seat and man separation initiator. Initiator gases actuate the inertia reel strap guillotine, which severs the straps that are sewn to the personnel parachute risers. The pilot can then remove the shoulder harness, stand, and exit from the aircraft without parachute hang-up. As the pilot stands, the seat pan moves unrestrained and personnel service leads pull free from their connections. Also, activation of the seat/ man separation initiator ballistically releases the WORD and drogue release and parachute container opener.
ROUTINE MAINTENANCE.- With the safe and arm control in the UP position and maintenance safety streamer safety pins installed, you must pull the emergency release control to remove the survival kit from the seat for replacement or maintenance.
The survival kit (fig. 6-43) is a post-ejection life support unit that also serves as a structural portion of the ejection seat. There are three distinct components in the kit: the seat pan, survival package, and emergency oxygen supply.
The seat pan, constructed of a honeycomb core with aluminium alloy face sheets, performs a dual function. First, it provides a base for attaching post-ejection life support equipment. Secondly, as the pilots seat in the aircraft, it provides a structurally secure attachment for the pilot's lower torso restraint belts.
The survival package is attached to the seat pan through a lanyard system. This allows the package to fall free of the seat pan and still remain near the pilot. Upon manual release, the survival package falls approximately 12 feet. It is then snubbbed by a lanyard, which inflates the life raft. The package then falls 13 feet below the raft. This stabilizes the raft during parachute descent. The survival package contains a life raft,
Figure 6-43.- Survival kit assembly.
signal devices, medical aids, and miscellaneous survival aids. The emergency oxygen supply, attached to the seat pan bottom, is a self-contained unit that can provide 50 cubic inches of breathing oxygen. It can be operated either automatically (during ejection) or manually. Automatic emergency oxygen control is provided by a lanyard assembly located on the underside of the seat pan left thigh support and is connected to the catapult cartridge manifold. During ejection, upward movement of the seat provides automatic actuation. Manual emergency oxygen control is provided by a handle and pull ring located on the inboard side of the seat pan left thigh support. An upward pull on the handle provides emergency oxygen to the pilot should the aircraft's main oxygen system fail. A pressure gauge, visible through a cutout on the forward left-hand side of the survival kit assembly, should indicate 1,800 psi (needle in the black area) with a full bottle. The emergency oxygen supply should last approximately 15 minutes, depending upon altitude and pilot demand. The higher the altitude, the shorter the duration, because oxygen is delivered by the mask regulator under pressure upon demand.
NOTE: Automatic actuation of the emergency oxygen supply also provides automatic actuation of the emergency locator beacon.
COMPONENT MAINTENANCE Since the seat assembly is designed for "one-shot" operation, it cannot be operationally checked as a unit. However, various components that contribute to the successful functioning of the seat assembly must be operationally checked and tested. It is your responsibility to check, test, and adjust ejection seat components as well as remove and replace cartridges. By using the applicable MIMs that contain the procedures for testing, adjusting, and checking components, along with diagrams, drawings, and trouble-shooting charts, you will be able to maintain the ejection seat properly and safely.
NOTE: The following material contains only typical maintenance practices and must not be used during actual component repair and tests. Use only the information contained in the applicable MIM. There are several procedural checks that may be performed on the Stencel ejection seat. For each of these checks, you should ensure that the safe/ arm control is in the SAFE (up and locked) position and that all three maintenance safety streamer safety pins are installed prior to beginning the tests. Most of the checks require that you remove the survival kit and wedge assemblies prior to starting the test and reinstall them at the completion of the test. This is not required for the height adjustment actuator check-out. When you are performing several checks in succession, you do not need to remove and reinstall the survival kit and wedge assemblies between each test.
Safe/ Arm Control Assembly Check-out
The individual actions required to check-out the safe/ arm control assembly may be grouped' into 11 major steps.
1. Install the initiator pull test tool set, as shown in figure 6-44.
2. Manually release the safe/ arm control assembly release. You should ensure that spring tension is evident in the release knob. Then, you should lower the safe/ arm control to the full DOWN position.
3. Attach a push-pull gauge to the safe/ arm control assembly and then pull upward. The handle should move upward and lock in the SAFE (full up) position with a maximum force of 10 pounds with no evidence of binding. You should observe the outboard bell crank rotate downward, disengaging the upper and lower connect and disconnect sears. Also observe that the inboard bell crank rotates upward to fully engage, the safety plunger between the initiator rotors.
4. Raise the emergency release handle to the UP and LOCKED position. You should not see movement of the upper connect and disconnect sear; however, the lower connect and disconnect sear should move down. You should check to see that the T-bar blocks the initiation rotors.
5. Lower the emergency release handle to the full DOWN position: You should see the bell crank connected to the lower sear rotating up-ward, the initiation subsystem rotors not moving, and the T-bar moving, down.
6. Observe that the initiation rotors do not move when you pull on the ejection control handle.
7. Lower the safe/ arm control assembly to the full DOWN position. You should ensure the safe/ arm control moves to the DOWN position with no evidence of binding, and the inboard bell crank moves downward and completely disengages the safety plunger from the rotors.
8. Raise the safe/ arm control assembly to the full UP position. You should ensure that the safe/ arm control is locked into position.
9. Lower the safe/ arm control assembly to the full DOWN position. The emergency release handle is raised to the UP and LOCKED position. You should observe that the upper sear moves down and the pull-test tool extends to the RELAXED position.
Figure 6-44.- Initiation pull-test tools installation.
10. Lower the emergency release handle to the control to the full UP position. Then, you remove DOWN and LOCKED position. When you pull the initiation pull-test tool set. up on the ejection control handle, you can observe that the initiation rotors move and the pull-test tool extends to the relaxed position.
11. Stow the ejection control and reset the
Emergency Release Handle Assembly Check-Out
The emergency release handle assembly check-pull-test tools. You should raise the safe/ arm out may be divided into nine major steps. Portions of the test are shown in figures 6-45 and 6-46. 1. Install the initiation pull-test tool set. Lower the emergency release handle and the safe/ arm control to the DOWN and LOCKED position. Position the push-pull gauge against the top of the emergency release handle and press down on the latch. You should be able to retract the latch with a maximum of 15 pounds of force. 2. Depress the locking latch and raise the emergency release handle one-fourth inch. Attach a push-pull gauge and lanyard to the emergency release handle and pull up and aft. The handle should rotate fully with a maximum force of 40 pounds. You should also notice that seat release shaft rotation actuates the seat and man separa-tion sear, and the pull-test tool extends to the relaxed position. Check to see that the T-bar blocks the firing control rotors, and the emergency
3. Lower the emergency release handle to the full DOWN and LOCKED position. Watch the seat and man separation sear return to the ARM position and the T-bar disengage from the firing control rotors. 4. Raise the safe/ arm control to the full UP and LOCKED position. Squeeze the emergency release handle and slowly pull up and aft. Notice that the connect and disconnect upper sear does not move. Lower the emergency release handle to the full DOWN and LOCKED position.
5. Grasp the emergency release handle and, without squeezing the handle or releasing the lock-ing latch, pull up on the handle. The handle should not move.
6. Remove the clevis from the fork at the connect and disconnect sear. Remove the top screws and loosen the bottom screws on the lanyard retainer assemblies. Rotate the retainers release handle is locked in the UP position. forward.
Figure 6-45.- Emergency release handle assembly check-out.
7. Lower the safe/ arm control to the DOWN and LOCKED position. Simulate a seat/ man separation by unlocking the emergency release handle. Pull upon both the seat and man separation lanyards. Observe that the seat release shaft rotates to the released position and the seat/ man separation upper sear moves downward. You should also notice that the seat/ man separation lanyards release from the bell cranks.
8. Attach the seat release lanyards to the seat release lanyard bell cranks. At this point, make sure that the seat release lanyards are not pinched between the seat release lanyard bell cranks and the slots in the lanyard retainer assemblies. Rotate the seat release lanyard bell cranks down below the shear pins in the lanyard retainer assemblies. You should ensure that the lanyards remain attached to the bell cranks. Rotate the lanyard retainer assemblies up and aft and install the top screws and washers. Tighten the bottom screws in the lanyard assemblies. When you apply light hand pressure, you should observe freedom of movement in the bell cranks.
9. Lower the emergency release handle to the DOWN and LOCKED position. Remove the initiation pull-test tool set.
Figure 6-46.- Separation lanyard retainer assemblies.
Ejection Control Assembly Check-out
Checking the ejection control assembly is a four part procedure. The first part of the procedures shown in figure 6-47.
1. Install the initiation pull-test tool set. Ensure the ejection initiator pull-test tools are not preloaded. Position the safe/ arm control to the full UP position. Attach a push-pull gauge to the ejection control assembly. Pull upward and record the breakout force. The breakout force should be 15 to 25 pounds.
2. Lower the safe/ arm control to the full DOWN position. Continue pulling upward on the ejection control assembly until the pull-test tools extend to the relaxed position. The force required to accomplish this task should be 15 to 40 pounds. You should ensure that the ejection control assembly does not separate from the seat. You should also observe the initiation rotors rotating past the safety plunger.
3. Stow the ejection control assembly while manually returning the initiation subsystem rotors to the ARMED position. Then install the initiation pull-test tool to the upper connect and disconnect sear. At this point you can simulate automatic seat/ man separation by rotating the emergency release handle to the full UP position. Notice that the upper connect and disconnect sear moves down, and the pull-test tool extends to the relaxed position. Check to see that the T-bar is
Figure 6-47.- Ejection control assembly check-out.
in the full UP position, and that it is blocking the initiation rotors.
4. Raise the safe/ arm control to the UP and LOCKED position. Lower the emergency release handle to the DOWN and LOCKED position. Remove the initiation pull-test tool set.
Inertia Reel Assembly Check-out
The inertia reel check-out may be grouped into seven steps. The test is shown in figure 6-48.
1. Insert the bridle rod through both the parachute riser loops. Position the inertia reel manual control to UNLOCK. Then grasp the centre of the bridle rod and extend the risers to mid position. Hold the risers extended and position the inertia reel manual control lever to LOCK. When you pull firmly on the centre of the bridle rod, the risers should not extend.
2. Slowly allow the risers to retract. The risers retracting and ratcheting action should be audible during retraction. The inertia reel control lever should not snap into position, or the test results will not be valid.
3. Slowly position the inertia reel manual control lever to UNLOCK. Grasp the centre of the bridle rod and extend both risers to the mid position. Exert a sharp pull on the bridle rod. The inertia reel should lock and the risers should not extend when a firm pull is applied. Slowly allow the risers to fully retract, and then pull the risers again. You should not be able to extend the risers.
4. Position the lever to LOCK, and then UNLOCK and extend and retract the risers. The risers should extend and retract freely.
5. Attach a push-pull gauge to the bridle rod. Pull the gauge straight and extend the risers. You should record the force required to extend them. Repeat the step three to five times. The risers should extend with a force of 5 to 15 pounds. Allow the riser to retract slowly.
6. Position a 24-inch steel rule against the for-ward edge of the yoke and perpendicular to the catapult tubes. Without extending the inertia reel straps, lift the bridle rod and measure the normal extension of the risers. You should record this measurement. Pull on the bridle rod and measure the full extension of the risers. Again, record the measurement. Allow the risers to retract slowly. At full extension, you should observe a minimum of 18 inches. Then, subtract the normal measurement from the extended measurement. The difference between the
Figure 6-48.- Inertia reel assembly check-out.
measurements should be a minimum of 11 inches with a maximum of 25 pounds of force. Allow of total riser travel. the risers to completely retract and remove the spring scale and bridle rod.
7. Position the inertia reel control to LOCK. Attach a spring scale to the centre of the bridle rod. Position a push-pull gauge against the forward edge of the control knob parallel to the seat side panel. Apply a 50-pound pull to the bridle rod and maintain this tension while applying a push force to the should move, without binding, to the aft position control knob. The control knob
Seat Height Adjustment Actuator Check-out
Removal of the wedge and survival kit assemblies is. not required to complete the five steps of the seat' height adjustment actuator
Figure 6-49.- Seat height adjustment actuator check-out.
Figure 6-50.- Airspeed/ altitude sensor functional check setup.
check-out. Portions of this test are shown in figure 6-49.
1. Attach a control tester to the plocket on the left side of the seat. You should ensure that the tester power switch is OFF and the raise-lower switch is in the mid position. Connect the tester electrical plug to a 115-volt ac, 60 Hz, single-phase power source and position the power switch to ON.
CAUTION To prevent damage to the height adjustment actuator motor because of overheating, the operating time limit of 30 seconds on and 1 minute off must be observed.
2. Position the raise-lower switch to RAISE and hold it in that position. You should observe the current indicated on the control tester ammeter while the seat travels to the full UP position. The maximum start current should be 15 amps and the maximum run current should be 5 amps.
3. Release the raise-lower switch and place a pencil mark on the actuator shaft at the locking collar. Now, move the raise-lower switch to LOWER and hold it in that position. Again, you should observe the current indicated on the control tester ammeter while the seat travels to the full DOWN position. You should notice no binding while the seat is travelling. The start and run current requirements are the same as in the previous step.
4. Release the raise-lower switch. At this time, you should measure and record the distance from the pencil mark on the actuator shaft to the upper edge of the locking collar. For the test results to be acceptable, the difference between the measurements should be 4.93 to 5.06 inches of total actuator shaft travel.
5. Raise the seat bucket to the mid-travel position. Position the power switch to OFF. Disconnect the tester electrical plug from the power source and disconnect the tester electrical plocket from the seat.
Airspeed/ Altitude Sensor Check-out
The airspeed/ altitude sensor (A/ AS) must be removed from the aircraft to perform the check-out procedure. The following paragraphs describe the steps of the test procedure. Figures 6-50 and 6-51 show portions of the test. 1. Place the A/ AS in the mounting fixture and secure it to the workbench. Screw the pitot
Figure 6-51.- Airspeed/ altitude sensor function check.
hose from the manifold assembly onto the pressure port of the A/ AS. After you remove the static port filter, screw the altitude hose from the manifold assembly into the static port of the A/ AS. Then connect the pitot pressure hose of the test set to the airspeed port of the manifold assembly. Set the pressure temperature test set controls to the positions listed in table 6-1.
WARNING The TTU-205-C/ E test set must be properly grounded to prevent injury to personnel.
2. Connect the test set electrical plug to a 115-volt ac, 400 Hz, single-phase power source. Set the test set power switch to ON. When the pressure stabilizes, the static pressure ready light and the pitot pressure ready light will illuminate. Rotate the static pressure vent and pitot pressure vent controls full clockwise. Position the airspeed knots control to 500. Vary the airspeed trim control as necessary to obtain 500 on the airspeed knots indicator. It will take a few minutes for the airspeed knots indication to increase to 500.
3. Position the airspeed leak test switch to ON. Allow the pitot pressure to stabilize. At this point, you should ensure that the pitot pressure light goes out and that the leak rate is not more than 15 knots in 5 minutes. Position the airspeed leak test switch to OFF. The pitot pressure light should illuminate and the airspeed knots should return to 500. Position the airspeed knots control to 280. Vary the airspeed trim control to obtain 280 on the airspeed knots indicator.
WARNING To prevent injury, make sure personnel are clear of the A/ AS plunger during actuation.
4. Attach a 0-to 150-pound spring scale to the arming key. Apply a straight pull on the scale and remove the sensor arming key. The arming key should release between 6 to 16 pounds of force and the sensor plunger should remain extended.
5. Extend the plunger with the pull tool and reinstall the arming key. Position the airspeed knots control to 250 and vary the airspeed trim control to obtain 250 on the airspeed knots indicator. Remove the A/ AS arming key and observe the A/ AS plunger retract. Again, use the pull tool to extend the plunger and reinstall the arming key.
6. Position the airspeed knots control to 50. After the airspeed knots indication decreases to the set value, position the test set power switch to OFF. Rotate the static pressure vent and pitot pressure vent controls full counter clockwise. Disconnect the test set pitot hose from the manifold and test set. Remove the pitot hose assembly from the airspeed port of the manifold and connect it to the altitude port of the manifold assembly. Plug the airspeed port of the manifold.
7. Rotate the static pressure vent and pitot pressure vent controls full clockwise. Position the
Table 6-1.- TTU-205-C/ E Tester Control Settings
test set power switch to ON. Position the ALTITUDE x 1000 FEET control between 7 and 8. The altitude feet indication should increase to approximately 7750. You may have to vary the altitude trim control to obtain 7750 on the altitude feet indicator. Remove the A/ AS arming key. The A/ AS plunger should remain extended.
8. Use the pull tool to extend the plunger and install the arming key. Set the ALTITUDE x 1000 FEET control between 6 and 7. Vary the altitude trim control to obtain 6250 on the altitude feet indicator. The arming key should release with a pull of 6 to 16 pounds of force and the A/ AS plunger should retract.
9. Again, you should use the pull tool to extend the plunger and reinstall the arming key. Position the altitude control to zero. After the altitude feet indication decreases to the set value, position the test set power switch to OFF. Rotate the static pressure vent and pitot pressure vent controls full counter clockwise.
10. Remove the manifold assembly from the A/ AS and disconnect it from the test set. Disconnect the static pressure hose from the test set. Disconnect the power source and remove the test set.
If the A/ AS passes the functional check, you may install it on the seat. If the A/ AS is faulty, you should forward it to depot-level maintenance for repair.
The manufacturers of the Stencel ejection seat have stated that the seat is corrosion resistant. Therefore, on the special 40-day corrosion inspection, the SJU-8/ A ejection seat has no inspection requirements. But we know that during shipboard operation, the seat will come in contact with salt spray, jet exhausts, stack gases, and various other debris. Although the seat is not addressed in the 40-day MRCs, it should be maintained in accordance with the NA 01-lA-509 and local squadron instructions. The NA 01-l A-509 states that ejection seats should have a 7-day inspection performed while at sea and a 14-day inspection when ashore.
You should ensure that oils, greases, preservatives, cleaning solutions, and solvents do not enter enclosed mechanisms, cartridge chambers, and ballistic hose and tube assemblies or come in contact with cartridges or initiators. You should cap all open ports during corrosion maintenance. All lubricants must be applied sparingly, and you must exercise care to protect nylon and cotton fabrics from contamination. Indiscriminate use of paint and preservatives that dry and build up with repeated or excessive application will often result in restricted movement of parts. This can easily render affected seats useless for ejection purposes. The following lubricants and procedures should be used on the Stencel ejection seat as stated in the NA 01-lA-509.
1. Lubricating oil, VV-L-800, should be applied to all parts that rotate, such as bell cranks, levers, pins, rollers, and similar components.
2. Grease, MIL-G-81322 or MIL-G-23827, should be applied to all parts that slide and should also be used as a corrosion preventive for all bright metal parts.
3. Apply MIL-C-85054 by brush or swab to all unpainted, non-moving parts, such as nuts and bolts, that do not require lubrication.
4. Cleaning solvent and lubricants may be applied with brush or cloth providing adequate care is taken to prevent entry into closed mechanisms.
5. Surface contaminants such as dried lubricants, dirt, grit, or corrosion products can be removed from intricate bell cranks and levers by scrubbing with a small nylon bristle brush using P-D-680, Type II, cleaning solvent. Follow the cleaning solvent with a light coat of VV-L-800 oil to the entire component or assembly.
The following emergency cleaning procedures should be used for cleaning ejection seats exposed to gross amounts of salt water or fire-extinguishing agents. The procedures described are normally used only to prevent further damage and will usually require further treatment at a higher level of maintenance.
Disarm ejection seat mechanisms before cleaning. Only authorized personnel should disarm seats and perform cleaning operations.
1. Remove parachutes, drogue parachutes where applicable, and seat pans. These items should be returned to local work centres for cleaning or replacement.
2. Remove ejection seats according to the applicable MIM.
3. Remove the CADs, rockets, and inertia reels from the seats. Cap all gas lines and ports. Then, wipe down these components with fresh water.
4. Rinse the seat thoroughly with fresh water. Continue washing while directing the water into crevices and close fitting parts until the contaminants are removed.
5. Blow as much water as possible from equipment with low pressure, clean, dry air.
6. Dry excess water deposits with a clean cloth, clean paper towels, or remnant cloths.
7. Apply the water displacing preservative MIL-C-81309, Type II, by spray or brush to critical metal surfaces and to recess areas that may not be completely dry. Water displacing preservative protects equipment during necessary inspection or inquiry, and during transfer to the repair custodian.
8. Wash all survival gear and pilot safety equipment with fresh water and dry thoroughly. You should refer to NAVAIR 13-l-6-X for detailed preservation procedures. Lubricate and control corrosion in accordance with maintenance requirements cards.
9. You should comply with all special inspection requirements before reinstallation. Reassemble ejection seats in accordance with the MIMs.
10. If necessary, send the ejection seat to the next higher level of maintenance.
11. Aircraft-mounted escape system components (mechanically activated CADs) should be wiped with fresh water, a cloth, and dried. If external contamination is suspected, these components should be removed and replaced.
The existing MIMs and MRCs for most ejection seat systems do not provide sufficient or explicit instruction for corrosion control and lubrication. The Aircraft Weapons System Cleaning and Corrosion Control Manual, NA 01-lA-509, and COMNAVAIRPAC/ COM-NAVAIRLANT INSTRUCTION 4750.2 (series) contain more information on corrosion control. These publications should be on your required reading list. The Aviation Maintenance Ratings (AMR) Fundamentals, NAVEDTRA 10342-3, and Aviation Maintenance Ratings (AMR) Supervisor, NAVEDTRA 10343-A1, also contain information regarding corrosion control. If needed, commands may develop local MRCs or local maintenance instructions to help eliminate corrosion of ejection seats. The following general information pertains to most ejection seats. Steps must be taken to prevent corrosion before it occurs. Correct procedures for repair of components and systems after corrosion has been treated must be used to ensure that corrosion does not return. The performance of the 210-and 364-day inspections, the 7-day inspections while at sea, and the 14-day inspections while ashore should be conducted according to the applicable MIMs and MRCs. Preventive maintenance on seat components, including procedures for cleaning and lubrication, is discussed in the following paragraphs.
Seat Structure and Components
Command philosophy varies regarding the painted parts of a seat structure. Some squadrons strip and paint at each 210-and 364-day inspection. Some leave the original anodized finish unpainted. Some touch-up chipped paint. Some do nothing. Each of these philosophies has some merit depending upon local conditions. The seat bucket and beam structure should be wiped with VV-L-800 general-purpose oil. You should allow the oil to soak into crevices, around rivets, and then wipe dry. Clean metal components with P-D-680, Type II, dry-cleaning solvent, and then inspect them for surface damage and corrosion. Do not attempt to remove light corrosion or discoloration of the cadmium-plated parts. Parts showing rust or pitting of the base metal or more than one area of plating loss should be replaced. Remove light corrosion, except for cadmium plated parts, by using a fine Scotchbrite abrasive mat or 500/ 600 aluminium oxide abrasive cloth. Lubricate moving parts, such as springs, linkage, and pivot areas, with MIL-G-81322 general-purpose grease. Lubricate firing pins and rollers with VV-L-800 oil. When using VV-L-800 oil, you should apply it with a clean, lint-free cloth such as MIL-C- 85043. Indiscriminate use of paint, preservatives, or other materials that dry and build up following application can prevent or restrict proper motion of movable parts. These materials must only be used where specified on non-moving parts. Paint touch-ups of seats installed on the aircraft should be done with a brush.
The following paragraphs provide guidelines for removal of corrosion products without damaging the structure. Removal of corrosion that has propagated beyond these limits requires replacement of the part.
CADMIUM-PLATED PARTS.- On cadmium-plated parts, corrosion will be evident as mottling of the plated surface with colour ranging from light gray to black. This is a function of the cadmium plating to protect the underlying base metal, and no attempt should be made to remove the discoloration. The presence of exposed base metal in a localized area is acceptable and should be protected. The appearance of red rust is cause for part replacement.
CHROMIUM AND NICKEL-PLATED PARTS.- You should polish bright plated parts with a fine Scotchbrite abrasive mat or 500/ 600 aluminium oxide abrasive cloth. Do not penetrate to the base material. If base material is exposed, it is cause to remove and replace the affected part.
ALUMINIUM FORGINGS AND CASTINGS.- Metal removal should not exceed 0.005 inch in depth. You should apply chemical conversion coating (alodine) to bare surfaces and repaint them as required.
RESTORATION OF FINISH
Abrasions and isolated damage areas may be restored using the following procedures: First, mask the area to be treated. You should feather sand the area around the damage with abrasive paper or Scotchbrite mat. Next, apply paint remover or methyl ethyl ketone and wipe the area dry with cheesecloth before the solvent evaporates. At this point, if bare metal is showing, you should apply alodine and allow it to dry. Finally, apply one coat of primer and two coats of paint. Special attention should be paid to the use of primers, polyurethane paints, paint removers, and methyl ethyl ketone. They are all flammable and toxic. Do not use them near open flames or sparks. Do not allow them to come in contact with your skin or eyes. Their use should be restricted to a well-ventilated area.
Safety precautions must be strictly observed when working around aircraft equipped with an ejection seat. These safety precautions cannot be overemphasized. Each ejection seat has several ground safety pins. These safety pins are provided on red-flagged lanyards for use at every point of potential danger. They must be installed whenever the aircraft is on the ground or deck, and they must never be removed until the aircraft is ready for flight. The following general precautions should always be kept in mind:
1. Ejection seats must be treated with the same respect as a loaded gun. 2. Always consider an ejection seat system as loaded and armed. 3. Before you enter a cockpit, know where the ejection seat safety pins are located and make certain of their installation. 4. Only authorized personnel may work on, remove, or install ejection seats and components, and only in authorized areas.
Supervisors take note. It has been said that nothing is foolproof because fools are so ingenious. Personal safety for those who work around ejection seats cannot be guaranteed; however, a high level of safety can be achieved if personnel have the proper attitude, under-standing training, and adequate supervision. Unless proper maintenance procedures are followed explicitly, even the most routine ejection seat maintenance tasks can grow drastically out of proportion and bring about an accident or injury. Education of the workers involved is the best assurance for personnel safety. The workers should be made aware of potential hazards and the proper means of protecting themselves. Workers should be assigned according to their capabilities.
Many thanks to Mr J. Wendle Spanwick III of Knoxville, Alabama USA for donating the above article.