What is the point of the delay between trigger pull and missile release?

[MobiSev]

I don't understand the point of the 3 sec delay. Is it just implemented incorrectly, and you should have to hold the trigger down instead of just tapping it? Because if that was the case, it would be more understandable as it would be kind of a makeshift safety feature.

[DD_Fenrir]

There are posts covering this aspect already Mob, but to reiterate,

 

1. partially to prevent inadvertent trgger activation; the F-15 for example requires a 1-2 second depress to launch AIM-120.

2. it takes time to data dump all the targeting info to the missiles, then the missile presumably does some confirmation of data received back to the TWS

3. then coolant umbilical's and data cables need to be severed

4. and after that the release mechanism needs to fire.

5. The missile must then drop a safe distance from the a/c before rocket ignition.

 

Add to all that 60s/70s era technology and bandwidth restrictions on data transfer, I can well believe it takes 3 seconds from a trigger pull to launch.

[yngvef]

I guess it's a combination of safety and technical limitations. Never forget at we're dealing with 50 year old electronics here. Things don't happen quickly as we are used to in the digital era of the 21st century.

[MobiSev]

There are posts covering this aspect already Mob, but to reiterate,

 

1. partially to prevent inadvertent trgger activation; the F-15 for example requires a 1-2 second depress to launch AIM-120.

2. it takes time to data dump all the targeting info to the missiles, then the missile presumably does some confirmation of data received back to the TWS

3. then coolant umbilical's and data cables need to be severed

4. and after that the release mechanism needs to fire.

5. The missile must then drop a safe distance from the a/c before rocket ignition.

 

Add to all that 60s/70s era technology and bandwidth restrictions on data transfer, I can well believe it takes 3 seconds from a trigger pull to launch.

 

So, you should have to hold the trigger down instead of just tap it? Because you only need to tap it right now.

[viper2097]

Yes, it is intend to be holden down for 3 sec., otherwise the missile won't get off rails.

Need to check if there is a bug at the moment.

[near_blind]

Yes, it is intend to be holden down for 3 sec., otherwise the missile won't get off rails.

Need to check if there is a bug at the moment.

 

The three seconds between trigger pull and launch are an electro mechanical process of transferring target data from the AWG-9 to the missile, synchronizing the seeker with the current radar configuration, and physically severing coolant, data and power umbilicals.

 

If it were a safety feature, that would imply that either it is not a three second launch cycle, but a six second launch cycle (three for the safety, three for the launch prep), or that failing to keep the trigger depressed for the full three seconds would effectively dud the missile. You can't re-attach a coolant hose or power cord mid flight.

 

I'm far more inclined to believe that the delay is of a mechanical limitation, probably pertaining to how the original AIM-54A was mechanized, than an intentional safety limitation.

 

FWIW Here's a documentary from the early 70s about the system showing missile launches. There's no guarantee the cockpit footage was from an aircraft in flight launching actual missiles, but the RIO is not depressing the button for longer than a second

 

[Bearfoot]

https://forums.eagle.ru/showpost.php?p=4065763&postcount=4

 

In ACM/Boresight mode, the WCS initiates a data dump of true air speed, range, seeker angle, English bias (guidance directive for where to head off the pylon), and a quick simulated Doppler injection to tell it for what to look for on return from the signal of the flood horn- that is, the normal radar isn't illuminating the target. This is dumped in less than a second, and the missile is on the way.

 

In the normal shot, the missile is being fed with a better Doppler command, which, depending on the missile type and selected mode, is used with FM ranging as well as recieved power difference between the rear antenna and the seeker antenna to discern the target over a greater range and against jamming. This extra information takes the greater amount of time.