Inconsistent PAC behavior

[eFirehawk]

Hello everyone,

 

I've been doing a bit of target practice and I've noticed that sometimes the gun PAC does an excellent job at holding the gun pipper in place and sometimes it's intervention isn't noticeable, when firing, the nose still goes up and sometimes that causes me to miss the target completely. All of that in the same mission and targets close to each other. I don't know exactly what I should do to keep the PAC at it's best effectiveness at all times.

 

It seems that if I trim the plane to keep the pipper very stable on the target, in a way that it almost feels like the first PAC stage without actually having it triggered, the nose goes up and keeps going up, always. However if I don't trim the plane so precisely and let it dive a little a bit while keeping the pipper on target by compensatng with the stick it works perfectly sometimes only. I have the PAC switch ON at all times, EAC and EGI as well, no issues with them.

 

For the more experienced people around here, is the PAC always effective for you? If so do you know what I could be missing?

 

Thanks

Edited February 26, 2013 by eFirehawk

[KLR Rico]

It sounds like you have a good idea what you're doing, but I'll ask the basic questions anyway. ;)

 

Make sure you're not trying to correct the pipper after engaging PAC-1, it has limited control authority, and if you go outside the limits, it's ineffective. You also want to make sure PAC-1 is engaged for a few seconds before firing, so it has time to stabilize.

 

Also, make sure your controller is setup correctly. What kind of controller are you using? Watch the HUD when you're doing a run, you should see PAC-1 or PAC-2 displayed, make sure it's showing the right one at the right time. PAC-1 on the trigger first stage, PAC-2 during firing.

Edited February 26, 2013 by KLR Rico

[Spetz]

Air brakes deployed? IFAIK PAC doesn't work when deployed. Just wondering...

[eFirehawk]

@ KLR Rico: Yep, I was engaging PAC 1 right when I managed to put the piper reasonably close to the target, then I would carefully place it on top of the target while in PAC 1 and afterwards pull the trigger until the end to fire/PAC2. I did as you suggested as now the PAC seems to work correctly more often, thanks :) However I noticed something else as well, please read below. And yes, all PAC indications on the HUD are displaying correctly. I am using a TM Warthog. :)

 

@ Spetz: No, I don't usually deploy the air brakes during gun runs.

 

===================

 

I noticed a few things that improved how often I get the PAC to work correctly but I still have a few questions though. As KLR Rico said, engaging PAC 1 only after having the pipper right on top of the target an then firing improved PAC behavior indeed, however I found out that my airspeed severely influences PAC. I noticed that if I shoot while faster than 300 IAS it works great every time even if don't give it time to stabilize and just pull the trigger like there's no tomorrow. However, firing below 250 IAS it doesn't work so well as often as 300, and if I fire close to or below 200 it almost never works correctly.

 

I think it makes sense now, less speed = less airflow which means PAC will need more degrees to trim the plane and it's limit is about 10 degrees if I recall. What bothers me though is that I want to fire and break off as far from the target as possible, and adjusting my aim and firing above 300 IAS gets me close a little too soon if I don't have the target right on the spot when I reach the effective gun range. Sometimes I see videos in which the pilot even deploys the airbrakes to go as slow as possible. Not sure if the PAC works well for them this way or not though. :)

 

Do you guys manage to get PAC to work correctly at slow speeds?

 

Thanks

Edited February 26, 2013 by eFirehawk

[Mule]

I flew the Smerch mission the other day and had the exact same thing happen to me. I didn't have time to do any testing but it was something i hadn't experienced before. I will have a go tonight when i get back from work and see what happens.

[GGTharos]

If your plane is relatively well trimmed, then the PAC still has authority.

If your plane is NOT well trimmed (ie. near the authority limits of the PAC) then the PAC cannot help you much.

 

Maybe you're right about the slow speeds.

[Konrad Friedrich]

 

I noticed a few things that improved how often I get the PAC to work correctly but I still have a few questions though. As KLR Rico said, engaging PAC 1 only after having the pipper right on top of the target an then firing improved PAC behavior indeed, however I found out that my airspeed severely influences PAC. I noticed that if I shoot while faster than 300 IAS it works great every time even if don't give it time to stabilize and just pull the trigger like there's no tomorrow. However, firing below 250 IAS it doesn't work so well as often as 300, and if I fire close to or below 200 it almost never works correctly.

 

I think it makes sense now, less speed = less airflow which means PAC will need more degrees to trim the plane and it's limit is about 10 degrees if I recall. What bothers me though is that I want to fire and break off as far from the target as possible, and adjusting my aim and firing above 300 IAS gets me close a little too soon if I don't have the target right on the spot when I reach the effective gun range. Sometimes I see videos in which the pilot even deploys the airbrakes to go as slow as possible. Not sure if the PAC works well for them this way or not though. :)

 

Do you guys manage to get PAC to work correctly at slow speeds?

 

Thanks

 

It's important to know that the gun's recoil forces are able to push the entire plane off target during firing.

The barrels fire in the 9 o'clock position (viewed from front of plane).

That's the reason why the gun is mounted off-center, toward the 3 o'clock position, so that the firing barrel lines up with the center line of the aircraft.

The recoil force of the GAU-8 is about 45 kN.

That's more than the output of one of the planes engines, which produces ca. 40 kN each.

 

So, I think it's plausible that the aircraft remains more stable at higher speeds when firing the gun.

 

GAU-8 Wikipedia: http://en.wikipedia.org/wiki/GAU-8_Avenger

 

As GGTharos mentioned: a well trimmed plane will help the PAC to stabilize.

 

When I'm forced to shoot at low speeds I flip the gun switch on the AHCP to GUN ARM without the PAC.

The dispersal of the gun without the PAC is more linear along the line of direction of flight.

So I put the pipper a few meters in front of the target and let the line of fire wander over the target.

Not very effective against armored targets - but enough for e.g. trucks.

But I won't get slow in the vicinity of armored targets, anyway. Because they tend to be able to defend themselves adequately.

Don't know if this is the correct procedure, but it works for me.

Edited February 26, 2013 by Konrad Friedrich

[WildBillKelsoe]

It should be understood that PAC needs a minimum of 8 seconds to eliminate effects of gust, gas, xwind. equally employed between 0.8 and 1.2 g, with bank angle less than 1 degree.

 

Retrimming will need the whole process to start all over again. Best I could do is 6 seconds from 6000 feet. Target has to be bracketed by time you break dive. EAC causes 2 degree pitch trim (PAC 1a)

 

We are very limited to attacking one, clearly delineated target, with our monitor resolutions.