More Navigation Questions

[BBQ]

Thought I'd create a new thread on this--so everyone doesn't have to see my questions!

 

I've re-watched the ABRIS video and the Navigation video (multiple times!)--and wondered, again--in the beginning of the NAV video, Matt talks about the NDB's (non-directional beacons) as part of the radio navigation. He had a bunch of presets for airfields, I think six, available--and as he switched through them, the HSI RMI needle was spinning--he had tested it. Now--lets say I'm on preset airfield #1 on the NDB system. My HSI guides me to airfield #1, per this preset. Now--forget about the ABRIS--what if I choose airfield #2 in the INS system, using "airfield" button, then choosing #2?

 

Which airfield will my HSI direct me to?

 

Also, I know the shkval sensor is tied to the INS system, since when you uncage the sensor, you can update the reference point the INS uses for updates. However, I didn't think the INS system was linked with the ABRIS, at all. But when Matt chose "target" mode on the INS, and chose #2, the ABRIS all of the sudden had the #2 target box chosen, and blinking at the top of the screen.

 

Where is the HSI directing me to now? Remember the NDB system is still set to airfield preset #1.

 

Also, how does the shkval sensor, simply by being uncaged, automatcially point at the reference point? Is that because it's set by default to the active waypoint in ABRIS, which was right next to the reference point?

 

Finally, Matt said you can have up to 10 target points in the INS system--but only 6 waypoints. I thought that was a little strange--if you could have 10 target points--why not 10 nav points?

 

Whew.

 

I'm trying, by way of pure annoyance, to get the manual released early ;)

[Steve Davies]

This is all visible in the video, so I hope that Matt won't mind me answering...

 

1) The radio nav aids and ADF are unrelated to the PVI-800 INS nav system, so you could select whatever you wanted on the PVI-800 without losing your ADF steering on the HSI. Since the HSI actually gives you an RMI needle for NDB approaches/nav and a separate sterring caret for the PVI-800, you can reference both simultaneously.

 

2) The ABRIS takes certain data from certain onboard sensors, including the PVI-800. As a position keeping device, it doesn't care where the PVI-800 says you are - it uses satelites for position keeping and does not use the INS. However, ABRIS will overlay targeting data and sensor line of sight/footprint data from the Shkval, and that is what you are seeing in Matt's video.

 

3) The HSI provides steering cues from the PVI-800 and ADF simultaneously (see above)

 

4) Shkval uses the PVI-800 to know where to look...it does not take any reference from ABRIS. that's why on a longer mission it's important to be able to execute an INS update prior to entering the target area in order to zero out errors in the system.

 

5) I suspect that the limitation of 6 steerpoints is related to real life limitations in memory available to the PVI-800. If you think about it, it's better to use 6 steerpoints to get you to and from the FEBA, and 10 more target steerpoints to help narrow in on specific areas of interest.

[BBQ]

thanks for replies--makes sense, wish I could have gleaned that myself.

[Wags]

Right on Steve. You are picking up the systems very quickly! ;)