MECHANICAL PULL INITIATORS
Mechanical Pull Initiators are used to initiate a CFS / TRS and rely on the upward movement of the ejection seat or pulling of an attached cable to pull a shaft(s) or have the seat strike a ‘trip’ lever on a firing pin mechanism to function (fire) the initiator. The initiators can be configured for single or dual firing pin mechanisms and single or dual output. Examples of PacSci EMC designed initiators are shown below.
Dual firing pin mechanisms like the T-38 unit utilize a cross bracket assembly attached to the top of the initiator. This provides the interface with the ejection seat and ensures the firing mechanisms pull equally. The cross bracket can be adjusted to take into account any difference between the mount point of the pull initiator on the rail and the attachment point on the ejection seat. Attachment to the seat occurs without preload. This ensures the safety pin can be removed and installed easily without risk to the individual performing the task.
One of the factors in designing a Mechanical Pull Initiator’s configuration is dependent upon their installation location. For initiators attached to the seat rail, the firing pin pull shafts are attached to the top of the ejection seat by means of a bracket assembly / seat attachment bolt interface. For cockpit attachments the initiator has a protruding lever that is struck by the seat. The basic function of each is the same, single or dual, seat pull or trip. As with the IAFI and EAFI, the upward movement of the seat activates a similar firing pin mechanism, compressing a spring, reaching a release point and expanding the spring to for the firing pin to strike the PP. Below are examples of seat rail and cockpit mounted installations
–65°F to +200°F
1×10-5 cc/sec. Air at 1.1 + 1Atmosphere
Conditioned at -80°F for two hours, –65°F for 70 hours then fired successfully.
Conditioned at +200°F for 50 hours, functioned successfully
MIL-C-83124 paragraph 126.96.36.199: Temperature –80°F & stabilized, then placed in 100°F/90% relative humidity until ice disappears, then –80°F & stabilized then fired at –80°F
Placed in vacuum chamber at 1.32 inches Hg and temperature of –65°F. Conditioned for one hour and functioned with no performance degradation.
MIL-C-82124: Submerged in water tank then tank pressurized to 17.75 psig to simulate 40 feet, then fired.
MIL-STD-810, Method 516, Procedure 1: Peak Amplitude of 30 G for 11 milliseconds; Shock pulse wave form: Terminal peak saw tooth for a total of 18 impacts.
100 cycles between –70°F and +200°F with 55 minute duration at each extreme then units functioned with no adverse effect.
Temperature, Shock, Humidity & Altitude (TSH&A): MIL-C-83124, Paragraph 188.8.131.52 at 70K Feet Altitude
MIL-C-83124, Paragraph 184.108.40.206, Devices lock shut then fired at –65°F and +200°F
MIL-STD-810, Method 514, Procedure I, parts 1-3, Procedure I, & curve z at –65°F, +70°f, and 200°F
MIL-STD-810, Method 509: 5%+1% Sodium Chloride by Weight for 48 Hours plus 48 Hours drying time. Fired at 70°F.
MIL-STD-810 Method 510, Except High Temperature 200°F.
6 Foot Drop
Dropped Firing Mechanism Up, Firing Mechanism Down and Side, then fired
IAW MIL-STD-331A, Test 103.1 Procedure 1 Dropped Firing Mechanism Up, Firing Mechanism Down and Side. Units did not fire and were safe to dispose of.
Per MIL-STD-810 Method 507 Procedure I except relative humidity was 100% and temperature +200°F with no adverse effect.
Platform Use & Heritage
AH-1, C-17, CASA-101, T-38A/N, PC-9, CASA-101, S-3 Viking, NASA T-38A/N, C-17, T-6, Mirage F-1, Alpha Jet, Scorpion, Honda Jet, AW609