AIM-54 not going active on tail aspect

[Noctrach]

We were testing AIM-54 kinematics tonight and noticed that the AWG-9 refuses to send an active command to the Phoenix on running targets in certain situations. We excluded the possibility of the target hitting the MLC or ZDF filters and played around with the target size and aspect switches to no effect.

 

One AIM-54Amk60 actually passed pretty much through my jet at almost a full mach of closure while supported in TWS-A (solid track), but missile timed out to -2 without going active.

 

We'll be testing this futher later down the week, but is there something obvious that we're missing here?

[Noctrach]

Also @Naquaii PD-STT is still losing track when combined antenna elevation and antenna train angle exceed 55 even though both are still individually WELL within gimbal limits...

Also still generating false tracks while doing so.

Any estimation on when this might be fixed?
Considering how much better PD-STT is at holding locks, our RIOs are quite anxious to see this resolved

[Naquaii]

The missile not going active at tail aspect targets is new to me but the one about loosing track within gimbal limits did exist but I thought that fixed.

 

I'd have to refer you to @IronMike so he can try and have our testers reproduce.

[SgtPappy]

@Noctrach @Naquaii, I also noticed something similar (maybe the same) when testing vs both AI and humans... Even at ~5nm, a Phoenix can be spoofed by chaff with the cold (human) bandit doing hard S-turns while in burner (doesn't look like the angle is enough to notch).  Against the AI, it's even easier as I see Pheonixes pass by me harmlessly while I was cold and turning side to side when launched by AI. I'll work on getting a few tracks when my friends and I have the time. 

 

I thought this was also the MLC and Doppler filters kicking in but then I realized, the AIM-54 is closing ~300+ kn to the target and only the AWG-9 would be vulnerable to this +/-100 kn closure speed. 

 

Do I misunderstand something? Would like your thoughts.

[Noctrach]

On 9/28/2021 at 9:47 PM, Naquaii said:

The missile not going active at tail aspect targets is new to me but the one about loosing track within gimbal limits did exist but I thought that fixed.

 

I'd have to refer you to @IronMike so he can try and have our testers reproduce.

Yeah I've tested it some more and it's absolutely still happening. @IronMike It's easy to reproduce:

• At >35 degrees ATA, pitch down 20 degrees
• At >15 degrees ATA, roll 45 degrees

Both cases will cause loss of lock.

 

@Naquaii What are the AWG-9 elevation limits? I'm losing a head-on targets from PD-STT at 45 degree antenna elevation

I'm starting to think this is more closely connected to antenna elevation, because I'm seeing behaviour that makes little sense.

 

Edited September 30, 2021 by Noctrach

[IronMike]

14 minutes ago, Noctrach said:

Yeah I've tested it some more and it's absolutely still happening. @IronMike It's easy to reproduce:

• At >35 degrees ATA, pitch down 20 degrees
• At >15 degrees ATA, roll 45 degrees

Both cases will cause loss of lock.

 

@Naquaii What are the AWG-9 elevation limits? I'm losing a head-on targets from PD-STT at 45 degree antenna elevation

I'm starting to think this is more closely connected to antenna elevation, because I'm seeing behaviour that makes little sense.

 

 

 

Thank you, we are investigating it.

[Noctrach]

9 hours ago, SgtPappy said:

@Noctrach @Naquaii, I also noticed something similar (maybe the same) when testing vs both AI and humans... Even at ~5nm, a Phoenix can be spoofed by chaff with the cold (human) bandit doing hard S-turns while in burner (doesn't look like the angle is enough to notch).  Against the AI, it's even easier as I see Pheonixes pass by me harmlessly while I was cold and turning side to side when launched by AI. I'll work on getting a few tracks when my friends and I have the time. 

 

I thought this was also the MLC and Doppler filters kicking in but then I realized, the AIM-54 is closing ~300+ kn to the target and only the AWG-9 would be vulnerable to this +/-100 kn closure speed. 

 

Do I misunderstand something? Would like your thoughts.

Our defense was a human defender doing a steady Mach 1.1 slice-back. Altitude delta was ~5000 feet and speed was maintained. This means shot aspect rotates all the way from front to tail aspect. F-14 attacker accelerated to keep the target outside of the ZDF (we maintained ~250 knots closure). AIM-54 seemed to track but there was no RWR warning and the missile ended up intercepting a point well behind the attacker (passed through my contrails and then proceeded to overtake at around Mach 2). Timeout never flashed and just proceeded to count down to -2, at which point a new track was created.

 

Do take care on hard S-turns that the Phoenix aerodynamic limit seems to be around Mach 1.5 for hard manoeuvring targets.

Also for the ZDF, realise that the real closure is a bit behind the closure on the DDD because it's measured between pulses, we often seemed to be at >100 knots (outside ZDF) but Tacview showed us dipping to <100 knots (inside ZDF) for about 3-5 sweeps.

 

The AI also seems to use a different AIM-54 and guidance model so I'm not sure how they compare.

Edited September 30, 2021 by Noctrach

[Naquaii]

5 hours ago, Noctrach said:

Yeah I've tested it some more and it's absolutely still happening. @IronMike It's easy to reproduce:

• At >35 degrees ATA, pitch down 20 degrees
• At >15 degrees ATA, roll 45 degrees

Both cases will cause loss of lock.

 

@Naquaii What are the AWG-9 elevation limits? I'm losing a head-on targets from PD-STT at 45 degree antenna elevation

I'm starting to think this is more closely connected to antenna elevation, because I'm seeing behaviour that makes little sense.

 

 

 

The vertical limits should be 59 degrees up and 81 degrees down. Depending on azimuth and roll they might become less though.

[Noctrach]

2 hours ago, Naquaii said:

 

The vertical limits should be 59 degrees up and 81 degrees down. Depending on azimuth and roll they might become less though.\

Just for my understanding:

Considering there's no roll gimbal, the gimbal limits on the AWG-9 would work as the top diagram in the following scenario, correct?

If the mechanism works like the bottom diagram then the effective gimbal limits would be much narrower, which could cause this weirdness..

 

Adding roll in the top scenario would "rotate" the box, therefore transposing some antenna elevation onto the antenna azimuth causing the target to drop off scope. I feel this is what happens in the sim only it starts much sooner and much more aggressive (adding them together 1:1).

Edited September 30, 2021 by Noctrach