Aim-7 behavior with “go now” alignment and STT

[broda]

Hi everyone,

I’m starting to learn the F14 and have 2 Questions related to the Aim-7.

1) If I don’t align the INS properly and use “INS Go Now” it won’t meet alerta launch criteria. Does it effect (and if yes how) the Sparrow performance? On MP I use this sometimes to be in the air as soon as possible. Do I cripple my Aim 7s by doing this?

2) Does it make a difference if the target is locked in PD vs P-STT? I know PD-STT is easier to notch and P-STT weak against ground clutter, but can the Aim-7 track properly in both modes or is it always better to go PD-STT (like with the Aim-54, where P-STT sends it pitbull off the rails)?

Thanks in advance

 

 

[Ivandrov]

1) Depends, INS Go Now is not a thing in the jet per se, it is a command to Jester to finish the alignment immediately regardless of where the progress is at.
So that means depending on when you tell him to "Go Now" you can be in one of four states.
AHRS backup
Coarse alignment
Launch Criteria
Fine alignment

Missiles in the DCS F-14 seem to work fine regardless probably because Heatblur doesn't really have control of the weapon side of things to simulate any kind of degradation in lofting capability for instance. In the DCS F-14, consequences for a bad alignment are navigational. (It can be hell trying to use datalink to figure out where targets are though, the drift becomes immense.)

2)Keep in mind that PD-STT omits use of the MLC filter, so you don't have the notch blind spot that the search modes have. AIM-7 tracks properly in both. 

Edited April 14 by Ivandrov

[broda]

5 hours ago, Ivandrov said:

1) Depends, INS Go Now is not a thing in the jet per se, it is a command to Jester to finish the alignment immediately regardless of where the progress is at.
So that means depending on when you tell him to "Go Now" you can be in one of four states.
AHRS backup
Coarse alignment
Launch Criteria
Fine alignment

Missiles in the DCS F-14 seem to work fine regardless probably because Heatblur doesn't really have control of the weapon side of things to simulate any kind of degradation in lofting capability for instance. In the DCS F-14, consequences for a bad alignment are navigational. (It can be hell trying to use datalink to figure out where targets are though, the drift becomes immense.)

2)Keep in mind that PD-STT omits use of the MLC filter, so you don't have the notch blind spot that the search modes have. AIM-7 tracks properly in both. 

Thanks for the info. Yeah with INS Go Now I meant doing that immediately after engine start. Sometimes there are enemies close to the airfield and I want just to take off and help my team in the air.

Was not sure if and how it effects the Aim-7s performance.

[Ivandrov]

5 hours ago, broda said:

Thanks for the info. Yeah with INS Go Now I meant doing that immediately after engine start. Sometimes there are enemies close to the airfield and I want just to take off and help my team in the air.

Was not sure if and how it effects the Aim-7s performance.

It does not. At least not at the moment.

 

Presumably an accurate altitude difference would be important in determining lofting behavior, but that's a complete guess on my part as I am not even sure that the loft behavior of the sparrows is correct.

Edited April 15 by Ivandrov

[wwWolfcom]

I don't think it's really implemented.

but, there will be minor degrade for AIM-7 guidance even if it's implemented.
Lofting should be degraded or n/a.

1. Without INS, RADAR will be degraded in stabilization, drift compensation(using AHRS).
Maybe, this could result degraded 'english bias' stated here.

On 10/17/2018 at 10:31 PM, GGTharos said:

^^^^

 

That is correct. English bias is the steering command loaded into the missile by the WCS, and it is one of the first things that the missile executes. English bias is removed some time after the missile's seeker locks on (ie. switches to whatever guidance method) or after some other condition is met.

On 11/18/2017 at 4:58 AM, al531246 said:

Taken from an F-15 weapons publication - https://imgur.com/a/C1Yvz

 

  Hide contents

 

 

 

2. Loft could be degraded.

There is no data transfer between aircraft and AIM-7 after airborne, except AIM-7P for guidance correction.
AIM-7 just need CW or PD reflected from target for guidance/navigation while in the air.
 

Edited April 15 by wwWolfcom

[draconus]

https://www.heatblur.se/F-14Manual/general.html#navigation-system

Quote

Although from the crew member’s point of view, the INS is used mostly for navigation, it is also essential for proper operations of other aircraft equipment. For example, the attitude is necessary for the radar. The attitude and the own position are required for some weapon delivery modes, particularly for long shots. Even more distressing to the crew, a complete failure of the INS renders the more advanced modes of weapons such as the AIM-7 and AIM-54 missiles inoperable.