Why can't Jester align the INS before the engines are on?

[Leviathan667]

In all the other planes, INS alignment is possible before the engines are on.

Is there a way to make jester align the INS before spooling the engines?

[near_blind]

From what I remember it wasn't done because of concern that power fluctuations when the generators kicked on after the engines started would cause issues.

[Steel Jaw]

12 minutes ago, near_blind said:

From what I remember it wasn't done because of concern that power fluctuations when the generators kicked on after the engines started would cause issues.

Same with commercial jets on external power, they want to switch to the APU before aligning the IRS and setting up the FMS.

[Bremspropeller]

On 12/11/2022 at 10:56 PM, Steel Jaw said:

Same with commercial jets on external power, they want to switch to the APU before aligning the IRS and setting up the FMS.

Not really - certainly not with the aircraft/ procedures I'm familiar with. All of them have batteries, which will protect against spikes and surges during the process of switching the power-source (which you'll do anyway when switching from APU to ENG GEN). Lots of airports have limitations on APU-usage and it's not uncommon to fire it up just shortly before the push. If it's not MEL'ed, which also happens every once in a while.

The Tomcat doesn't have a bat, which is the reason you don't want to fuxx0r with your power-supply with the INS up and running.

Edited December 13, 2022 by Bremspropeller

[IronMike]

On 12/11/2022 at 9:30 PM, Leviathan667 said:

In all the other planes, INS alignment is possible before the engines are on.

Is there a way to make jester align the INS before spooling the engines?

As explained above. One way this was mitigated, was by powering up the jet, aligning the INS, storing it, and powering it down again to have it ready before actual flight. This is available ofc with the stored heading alignment.

[Nealius]

On 12/12/2022 at 6:56 AM, Steel Jaw said:

Same with commercial jets on external power, they want to switch to the APU before aligning the IRS and setting up the FMS.

As well with the F-16, where real-world procedure is to perform SEC and EPU checks before starting the INS alignment, even though they are listed after (IIRC) in the checklists.

[Leviathan667]

Thank you all for your answers. 
i am preparing a custom land based QRA mission and will follow ironmike’s hint: start the engines then align then stop the engines while keeping ground  power on and then wait for the signal to take-off.

[QuiGon]

On 12/11/2022 at 10:30 PM, Leviathan667 said:

In all the other planes, INS alignment is possible before the engines are on.

Is there a way to make jester align the INS before spooling the engines?

I dunno about Jester, but a human RIO can do so just fine.

[Naquaii]

On 12/17/2022 at 3:23 PM, Leviathan667 said:

Thank you all for your answers. 
i am preparing a custom land based QRA mission and will follow ironmike’s hint: start the engines then align then stop the engines while keeping ground  power on and then wait for the signal to take-off.

If you set the option for SHA (Stored Heading Align) in the ME DCS simulates this having been done before you load in.

1 hour ago, QuiGon said:

I dunno about Jester, but a human RIO can do so just fine.

Jester can’t as he follows procedure.

[Spiceman]

IRL you had to wait until the pilot did the emergency generator test after engine start before turning up the back seat. The test interrupts power on the main AC bus and the interruption risks damaging some of the more sensitive stuff. 

[IronMike]

2 hours ago, Spiceman said:

IRL you had to wait until the pilot did the emergency generator test after engine start before turning up the back seat. The test interrupts power on the main AC bus and the interruption risks damaging some of the more sensitive stuff. 

Thank you, Spice!

[r4y30n]

So how would one setup for an alert 5 on the boat? A stored heading doesn’t seem feasible in that case.

[Naquaii]

10 hours ago, r4y30n said:

So how would one setup for an alert 5 on the boat? A stored heading doesn’t seem feasible in that case.

For the highest alerts that was indeed the case, at least procedurally. As to how good that worked in practice, I'm not sure.

[Spiceman]

On 12/23/2022 at 2:10 AM, r4y30n said:

So how would one setup for an alert 5 on the boat? A stored heading doesn’t seem feasible in that case.

Setting the Alert 5 was done by performing a normal aircraft startup (has to be a full ready-7 alignment), taxiing to the catapult, and then performing a normal shutdown. Now you’ve got a valid potential SHA. The airplane cannot be moved and the boat must remain on that heading, or you can no longer perform a SHA on startup. On an Alert 5 launch, you started the engines, turned up the AWG-9, ran the alignment (you can start the alignment even before the AWG-9 finished booting up) and launched. No tests in the front seat, no OBC, no nothing. Start the engines, get the alignment, and go. 

Edited December 24, 2022 by Spiceman

[r4y30n]

Awesome, thanks for the reply!