Can you make the HSI reference SPI?

[hcf]

While learning, I've found it helpful to set a waypoint from JTAC (manually entered in CDU) and then use HSI dialed like he says for approach vector.

 

 

Anyway, I found it helpful. But the thing I'm curious about is if you can switch the HSI to point you at a vector off SPI or not? I guess you could make a mark point and such, but is there a direct way?

[PFunk1606688187]

Well the HSI only ever points towards a navigational source, which when referencing a SPI would be your steerpoint. A steerpoint can be your SPI.

 

If I understand your notion its to try and have your HSI tell you when you're flying towards your target SPI on the rough heading that the JTAC gives you for your final attack heading.

 

This is very easy, all you have to do is set your target waypoint as steerpoint, ensure steerpoint is SPI, then set the HSI Course dial to the desired final attack heading. The Course Deviation Indicator will then tell you when you're abeam the correct heading to target and you should at that point turn towards the steerpoint.

 

If you don't understand how to read the CDI you should check the manual. Basically in order to be on the chosen course to the steerpoint (or other navigational source) you want the arrow to be unbroken and pointing at your 12 o'clock.

[hcf]

This is what I do now,

 

JTAC calls location, I copy that to a waypoint whether I get SADL from him or not, and set that waypoint as steer point.

 

Dial the HSI to a bearing somewhere in the range he gives.

 

Now like you say, I can use the CDI to inform me when I'm on (or near) that vector. I know in many expert YouTube vids the way it's done is to put eyes on target and steer into it, but I've found it helpful while learning that, when I have trouble with landmarks, or just as an extra reference when I look up on the pitch ladder on the HUD to fix my poor turn (I can see the target, or I can see the HSI - so I always have a reference).

 

It's been helpful while I'm learning spatial relationships, and has gotten my rate of JTAC "ABORT, ABORT, ABORT!" calls down.

 

The only time this breaks down is when JTAC wants you to kill a dozen tanks spread over 5nm. The SPI for each tank will be offset from the steerpoint by some great distance as you get further out from the position he gave.

 

The only thing I can figure is to make mark points on the SPI (when pointed at some tank), and set that as steerpoint, but it's a fair bit more work than just fudging the CDI in your head.

 

Mostly just curious if there's a simpler way.

 

Tho maybe now that I type this out, I wonder if I'm misinterpreting the intent of the bearing. Im thinking it is the bearing I should be on to every target, but it could mean instead the bearing I should be on towards the general area (the point JTAC conveys), deviating left or right to face targets. They do usually give you a range of bearings after all.

[PFunk1606688187]

The only time this breaks down is when JTAC wants you to kill a dozen tanks spread over 5nm. The SPI for each tank will be offset from the steerpoint by some great distance as you get further out from the position he gave.

 

The only thing I can figure is to make mark points on the SPI (when pointed at some tank), and set that as steerpoint, but it's a fair bit more work than just fudging the CDI in your head.

 

Mostly just curious if there's a simpler way.

 

Tho maybe now that I type this out, I wonder if I'm misinterpreting the intent of the bearing. Im thinking it is the bearing I should be on to every target, but it could mean instead the bearing I should be on towards the general area (the point JTAC conveys), deviating left or right to face targets. They do usually give you a range of bearings after all.

 

In reality you're not going to use a specific mark point or waypoint for every target if they're very close together unless you're dropping guided ordnance like JDAMs, and even then this isn't likely to be under the control of a JTAC on a CAS mission but instead as a planned strike.

 

For CAS the JTAC is giving you a window for your final attack heading, so maybe 20 degrees wide or something, and thats supposed to ensure that you run in in such a way that you're not at risk of dropping on friendlies or flying into an enemy threat that can be avoided. Same goes with the egress direction.

 

Even in modern CAS you're basically supposed to roll in and establish visual on your target and flying a tight navigational path to it isn't really part of it, thats why there's a window and not a single bearing-to. You leave the IP towards the target on the correct bearing and as you run in you attempt to establish visual contact and then maneuver to place your aircraft into the release envelope for the given weapon to be employed.

 

Using the HSI to cross check that you're on the right final attack heading is good, but being head down on your attack run really isn't. Not only should you be trying to visually fly onto the target (at this point if you can see the target and you're not on the final attack heading already you're too close to be making a change anyway) but you should also be prepared to visually acquire threats to your aircraft like missile launches.

 

Maybe you guys don't have trackir? With that its so easy to cross check a half dozen instruments in a second and go back to looking out of the cockpit it just becomes a reflex. Without that I can see how you might be more prone to keeping the view fixed to an instrument or cluster of instruments.