Question: Difference between Nav Update and INS Position Update

[Home Fries]

I'm trying to determine the difference between the Nav Update function on the Magic breaklock/Nav Update key and the INS Update function on the Target Designate/INS Update function. Specifically, if I want to do either a visual INS update or a radar INS update, how should I use them?

 

Thanks in advance.

[dhevans79]

So, forgive me if I have misinterpreted your question, but I guess you're asking in terms of functional difference as the manual covers how to do them quite well.

 

The main difference seems to be accuracy. With the magic, you can "lock on" to the target, and with the INS it basis the calculation on expected distance in front of the nose. In this case the magic gives nice feedback via the HUD, but to be honest the INS is just good if the nose is ligned up correctly to the actual way point. In both cases, it helps if the way point is over a physical over such as a VOR station or other landmark.

 

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[Frederf]

According to the manual the button on the stick begins the overfly update process (same as pressing REC*) while the button on the throttle begins the radar offset update process. But the manual isn't that accurate (change since publish?) nor clear. Based on what currently happens in the sim:

 

*If an oblique AG designate was previously performed the REC button cancels the update while the Magic Search button instead commands an overfly position capture.

 

Overfly INS Update

NAV mode

Position within 15nm of current waypoint

Press either REC or Magic Search (Stick) to capture current position

VAL button to validate entry as desired

 

Radar Oblique INS Update

NAV mode

Radar emitting

Set radar on oblique by PCA button OBL

AG designate button (throttle) a position by HUD diamond within 15nm of waypoint

VAL button to validate entry as desired

 

Invalid position capture by either method (update distance >15nm) will flash BAD light and VAL light will not be illuminated.

 

Note that nothing about the setup for the radar oblique update precludes an overfly update. At any time during the radar oblique process REC or Magic Search button can be pressed to command an overfly position capture.

 

All of the above is academic at this point as any method of any quality produces the same result, setting the INS position equal to the true position. For example flying 11nm beside the waypoint landmark and doing an overfly update produces a perfectly calibrated INS while in reality the INS would be miscalibrated by that 11nm distance.

 

The numbers produced by the oblique radar update are clearly not correct according to the geometry of the designation. It seems impossible for example to by 10nm away from the waypoint and AG designate a point such that the PCN numbers show a range <2nm of change.

[Robin_Hood]

Yes, the AG designate/Magic Slave/INS Update initiates radar update (recalage oblique), while the Magic Search/Nav Update initiates the overfly update (equivalent to pressing REC button on the PCN).

So whatever type update you want to make, you do not have to take your hands off the HOTAS.

[Home Fries]

Thanks everybody. It is all clear now.