Switching GAU-8 on causes nose to dip

[alanmc]

Hi all,

 

Here's something I wasn't expecting. I've been leaving my AHCP Gun switch in the Off position until I'm going to use it lately. So I'm flying straight and level trimmed for hands free. When I click the switch to Gun/PAC, the plane immediately goes out of trim and the nose dips.

 

I'm sure there's an explanation. Does anybody know why this happens? I was thinking that when the GAU spins up, some weight transfers to the front.

 

I never noticed it before now because I used to switch the Gun on before take off and leave it on.

[Eddie]

It's pitch SAS adding nose down trim bias when Gun Pac is armed.

[Taproot]

It's pitch SAS adding nose down trim bias when Gun Pac is armed.

 

Interesting.. Should you trim it back?

 

I also feel a nudge in the FFB when I arm the gun. Pretty cool.

[alanmc]

It's pitch SAS adding nose down trim bias when Gun Pac is armed.

 

Ah, that makes sense. It kinda means that you should only be hitting that switch when committing to a gun run.

 

Cool. Thanks.

[Eddie]

Interesting.. Should you trim it back?

 

You "can", but the bias is intended to ensure that there is enough pitch SAS authority to counter the pitch up when firing the gun. The nose down will become neutral trim during your dive before you actually fire the gun anyway.

 

But, if you're flying around for any length of time before you actually employ the gun trimming for level flight again won't hurt as long as you ensure you maintain trim such that SAS always has enough control authority.

[Yellonet]

You can arm the gun without using pac (switch in down position) which is possibly better for aerial engagements, but then it will be more difficult to keep the aim precisely at ground targets.

[WildBillKelsoe]

When she starts screaming, hit that switch to shut her up!