Build 1706: BVR logic error with SARH missiles in "Crank"-Mode (AIM-7M / F-15C illumination issue)

[Uzabit]

Bug Report
Game Version: 1.08 – Build 1706
Database Version: DB3K v512
Severity: Medium

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Subject
BVR logic error with SARH missiles in "Crank"-Mode (AIM-7M / F-15C illumination issue)

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Description
When firing AIM-7M Sparrow missiles, the F-15C frequently loses radar illumination of the target during a crank maneuver. The missile then self-destructs after a few seconds because the radar is no longer able to provide continuous illumination.

The issue seems to be linked to how the crank maneuver is initiated:

Immediately after launch, the F-15C appears to crank according to the search radar arc of the AN/APG-70.

Shortly afterward, the radar switches to illumination mode for the SARH missile, which uses a much narrower arc.

At that point, the crank geometry no longer supports illumination, and the missile loses lock.

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Radar ARCs_ANAPG-70.png (91.21 KiB) Viewed 577 times

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This behavior leads to a very high number of failed AIM-7M shots in engagements. By comparison, using the “Straight In” BVR logic avoids the problem almost entirely. The bug does not appear to affect all aircraft, since other platforms have illumination arcs that are wider and closer to their search arcs.

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Frequency
Often (especially at the start of engagements; not every single launch but reproducible in most cases)

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Steps to Reproduce

1. Load the attached F-15C Illumination+Crank Test.scen.
2. Assign the F-15C to fire AIM-7Ms in BVR mode with crank logic enabled.
3. Observe that shortly after launch the aircraft begins its crank, loses illumination once the radar switches to narrow-beam guidance, and the missile self-destructs.
4. Repeat using “Straight In” BVR logic for comparison—the AIM-7M illumination is maintained and hits occur as expected.

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Attached Files
• Radar ARCs_ANAPG-70.PNG (illustration of radar arcs)
• F-15C Illumination+Crank Test.scen

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Proposed Solution
Crank maneuvers for aircraft employing SARH missiles should be calculated based on the illumination arc of the fire-control radar, not the wider search arc. This would ensure continuous illumination throughout the missile’s flight.

[Knightpawn]

That is a very acute observation, and I believe you are correct. Considering that I am a Crank and Drag (not only Crank) player, I have to muster a lot of courage to set behavior to "straight in"

[boogabooga]

I thought that it was weird that this is being noticed just now, so I checked earlier databases. In 503 for example, all of the F-15s APG-63 and 70 have the arcs reversed from what you are showing here- the illumination arc was previously wider than detection arc. Which makes more sense.

I think that you should report this as a database error. The game engine's behavior itself seems reasonable.

[Uzabit]

I can open an issue on the GitHub tracker if the developers confirm that the AN/APG-63 or AN/APG-70 is incorrectly configured for SARH missiles. Since I’m not an expert on these radars, I would need supporting information to substantiate the claim.

[Dimitris]

Hi,

Yes, it seems that for some reason the search/track and illuminate arc values have been reversed. Please submit this as a ticket on the DB Github tracker. Thanks!

(Also: Another first-class report! Everyone else please take note)

[Uzabit]

I think the excessive cranking has improved with the latest build. I'll still report the radar arc issue as a database bug.

[Nikel]

I think the excessive cranking has improved with the latest build. I'll still report the radar arc issue as a database bug.

Indeed, must be this line.

FIXED: #16858: Missiles go blind due to excessive crank angle

[Uzabit]

According to PygmalionOfCyprus, the db issue has been fixed and will be included in the upcoming DB3k v515 release.