The aim-120C5 fin deflection is to low

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AIM-120C-5 Fin Deflection Limit Issue - Current Value Appears Undermodeled

Brief Description

The AIM-120C-5’s current fin deflection limit of 15.1° appears significantly undermodeled based on video evidence from the recent Ghost Bat AMRAAM test. Looking for help finding official sources to support an increase.

What I Found

So I’ve been digging into the AIM-120C-5’s control surfaces because something’s been bugging me about how they perform in-game. The current fin deflection limit is 15.1°, but after watching the Ghost Bat test footage, that number seems way too low.

The Video Evidence

Boeing MQ-28 Ghost Bat AMRAAM Launch Test (December 8, 2025):

  • YouTube: https://www.youtube.com/watch?v=RQ61SO0vh7E
  • This is official footage from the Australian Department of Defense showing a live AMRAAM launch
  • You can clearly see the fins deflecting during launch and flight
  • From what I can see in the video, the deflection looks to be somewhere in the 30-40° range - way more than the 15.1° we have in-game
  • The missile pulls some pretty aggressive maneuvers right after launch, which wouldn’t be possible with only 15.1° of deflection

What the Official Documents Say

I spent some time going through government sources to see what’s actually documented:

Control System Basics:
According to GlobalSecurity.org’s documentation on the AIM-120:

  • The missile uses four independently controlled servo actuators (WCU-11/B control section)
  • Each actuator has a brushless DC motor with a ballscrew system
  • These are connected directly to the fins with “infinite resolution” positioning

The C-5 Specific Hardware:
From Air Force fact sheets and defense documentation:

  • The AIM-120C-5 uses the WCU-28/B control section (this is the “SCAS” - Shortened Control Actuation Section)
  • It’s got compressed electronics and improved ECCM compared to earlier variants
  • Later variants (C-7 and D) got upgraded to VCAS (Value Control Actuation Section), which suggests the C-5’s SCAS was already pretty capable

Performance Requirements:
Here’s where it gets interesting - the missile is rated for 40G overload according to multiple defense sources. There’s no way you’re pulling 40Gs with only 15.1° of fin deflection. The math just doesn’t work out.

Technical Analysis:
There’s this really detailed study called “AIM-120C-5 Performance Assessment for Digital Combat Simulation Enhancement” by Tyrell, Funk, and Marton (2014). They did CFD simulations using only declassified data, and they tested the missile up to 30° angle of attack. At 30° AoA, they found that flow separation starts happening on the fins - meaning that’s the aerodynamic limit, not a mechanical one.

The Problem

Here’s what doesn’t add up:

  1. Video shows way more deflection than 15.1° - it’s pretty obvious in the footage
  2. The missile is rated for 40G - you need serious control authority for that
  3. Technical studies show 30° AoA capability** - you need corresponding fin deflection to achieve that

The current implementation makes the missile feel really sluggish in close-range engagements and doesn’t match what we’re seeing in real test footage.

Sources I Used

Official Government Docs:

  1. U.S. Air Force Air Combat Command Fact Sheets (2020-2022)

  2. Department of Defense FY2015 Selected Acquisition Report

Technical Analysis:
3. “AIM-120C-5 Performance Assessment for Digital Combat Simulation Enhancement” (2014)

Defense References:
4. Designation-Systems.net - AIM-120 page
5. GlobalSecurity.org - AIM-120 Design docs
6. ArmyRecognition.com - AMRAAM specs

Video Evidence:
7. Ghost Bat AMRAAM Test - Australian DoD Official Release

What I’m Suggesting

Based on everything I found, I think the fin deflection should be increased to around 30-35°. Here’s why:

  • The Ghost Bat video clearly shows deflection way beyond 15.1°
  • The technical analysis shows the missile can handle 30° AoA before aerodynamic issues
  • The 40G rating requires much more control authority than what 15.1° provides
  • It would make the different variants more distinct (A/B baseline, C-5 improved with SCAS, C-7/D further improved with VCAS)

The Tricky Part

The exact deflection limits are classified. I couldn’t find a single official document that says “the AIM-120C-5 has X degrees of fin deflection.” But between the video evidence, the performance requirements and the technical analysis it’s pretty clear that 15.1° is way too low.

TL;DR

Watch the Ghost Bat video at https://www.youtube.com/watch?v=RQ61SO0vh7E - the fins are clearly deflecting way more than 15.1°. Combined with the missile’s 40G rating and technical studies showing 30° AoA capability, the current implementation seems significantly undermodeled. I suggest increasing it to 30-35° based on the available evidence.

If anyone has access to other official test footage or declassified technical docs that could help pin this down more precisely, that would be awesome. This is just a summary of what i could find if you have any other options or sources feel free to leave them i want to make sure all the sources i provided are valid before i attempt to bug report it and maybe the community can help brain storm

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