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New numbers on HSI, what are they?


Bankler

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You're pretty much right on the money, A is the estimated fuel remaining once you reach the selected navigation point, B is the estimated distance-to-go to begin optimal rate-of-descent.

REAPER 51 | Tholozor
VFA-136 (c.2007): https://www.digitalcombatsimulator.com/en/files/3305981/
Arleigh Burke Destroyer Pack (2020): https://www.digitalcombatsimulator.com/en/files/3313752/

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What are these?

As you guess,

 

(A) Fuel remaining at TACAN station

 

(B) Distance from TACAN station where pilot should begin descent.

 

With Waypoint "boxed" there are similar FPAS numbers for the selected waypoint.

 

I don't understand the descent distance as it's incorrect for an optimum profile (Cruise Mach / 250KIAS) when descending to sea level and in DCS it counts down to 0 ?

 

Source: Flight Manual, 2007, A1-F18AC-NFM-000, p97, 2.3.1.4


Edited by Ramsay

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(B) Distance from TACAN station where pilot should begin descent.

...

I don't understand the descent distance as it's incorrect for an optimum profile (Cruise Mach / 250KIAS) when descending to sea level.

 

Your suggestion seems correct. Question is, "Distance from TACAN station where pilot should begin descent"... to accomplish what? And by what kind of descent?

 

When I started a 250 kts descent at the point the HSI suggested and maintained it, I passed over the TCN at around 8800 feet.


Edited by Bankler
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Just noticed these yesterday.

 

Maybe there is some info on the FPAS page?

 

"A" is the same number as the one under "FUEL REMAIN" under FPAS. So that one I believe we have figured out. "B" is still mysterious imho. Even GB wasn't sure and natops isn't too clear about it either.

 

I think we might need some ED input here?

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I find that when the distance-to-go to begin descent reaches 0, the navigation point is almost exactly at 10° below the horizon, so I go to idle throttle and glide down.

REAPER 51 | Tholozor
VFA-136 (c.2007): https://www.digitalcombatsimulator.com/en/files/3305981/
Arleigh Burke Destroyer Pack (2020): https://www.digitalcombatsimulator.com/en/files/3313752/

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Probably this (about FPAS):

 

2.3.1.4 HSI with Waypoint or TACAN Steering Selected.

If waypoint or TACAN steering is selected on the HSI display, the fuel remaining at arrival and the miles from the waypoint or TACAN station to begin descent are displayed on the HSI display.

When FPAS cannot calculate fuel remaining and the point to begin descent, invalid Xs are displayed for these parameters. If TAS exceeds Mach 0.9, blanks are displayed.

If fuel remaining at the waypoint or TACAN station is less than the TO XXXX LB legend, the WYPT number, the TO XXXX LB legend on the FPAS display and the fuel remaining on both the FPAS and HSI displays is flashed.

HSI.jpg.dded6e983722e24d182b5b6f6887fe02.jpg

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ED? Provide some clarity maybe? :)

 

It seems to be consistent with the following (still need to do more tests):

 

The position in which you start a 10 degrees nose down descent, to fly over the TACAN at around 2,000 feet.

 

Edit: My bad, not consistent at all...


Edited by BarTzi
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I still have no idea. It's not even linear.

 

Tested with the supercarrier tacan.

 

Alt Range Ratio

 

35k' 32.7nm ~1.07

30k' 27.5nm ~1.09

25k' 22.0nm ~1.13

20k' 16.8nm ~1.19

15k' 11.6nm ~1.29

10k' 6.3nm ~1.58

 

Also no idea why ED just can't tell us how it works instead of leaving us guessing here. Is it a secret? Or a WiP thing that was not meant to be shipped (which would be fine, and understandable)? Either way, just tell us?


Edited by Bankler
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