INS drift corrections

[sobe]

Could some one explain the methods for manually correcting INS drift when the EGI is not functioning.

[KlarSnow]

To manually correct INS drift while the EGI is not functioning you have a couple of different things you need to do.

the simplest thing is to correct positional drift via a position update. You can perform this by selecting the “Update” cursor function on the A/G radar or Target pod.

You will need to have a steerpoint that you know the location of in PB17 in the target pod or radar, put the cursors on the steerpoints position in the real world, and command update via TDC press in the front cockpit or in the rear cockpit trigger full action. 
This will update your INS position based on where your cursor is. If you have your cursors over the wrong point on the ground you can induce more error and make your positional error even greater. So be careful.

Not implemented currently is the overfly update or HUD updates that can be used to do the same thing visually.

To help reduce how much the INS drifts you can perform an INS PVU or precision velocity update. this will “calibrate” the INS via the radar and will reduce the rate at which it drifts. it cannot permanently remove the drift over the course of a flight, but it will reduce the magnitude of the drift.

To perform an INS PVU be in command of the A/G radar in RBM and press auto acq down. This will switch to the PVU page. MN PVU is selected by default, this will only really help with radar maps being cleaner currently since there is no mission Nav (MN) implemented currently, so I will leave this one for later.

along the bottom of the PVU display select INS. Wait a moment as it begins measuring velocities. As soon as you see values populate press the TDC to begin the PVU. The lower values will go away and you will see a single value which represents the total remaining drift. Let it sit and cook and perform some gentle turns and climbs/descents and you will see it quickly start to reduce. Once it is low enough that you like (0.2-0.1 is achievable pretty quickly) press auto acq down to accept the update and return to the radar. Drift will continue to build up after this but it will be at a much lower rate than prior to the update.

You should only have to perform this INS PVU once per flight, multiple PVUs are not really going to help much but one INS PVU will significantly reduce the drift rate.

Of note, there is a land/sea option in the PVU screen, make sure to select the correct one for what you are flying over/your radar is pointing at. If you perform a INS PVU with land selected but your radar is measuring mostly water, the movement of the water can significantly mess up the PVU. Same thing can occur if you set it to SEA and perform a PVU over land, it will compensate for non existent water movement introducing error. 
 

Normal process for this would be to perform the INS PVU early in the flight or prior to fencing in, once accomplished perform an update on a well known point, and then your system should both be fairly accurate and have minimized drift for the tactical portion of the flight.

Have several steerpoints or aimpoints/offsets on easily identifiable features in your planned AOR, so that if you notice drift starting to become an issue you can easily map or cue the targetting pod to one of them and update your system.