accuracy of the CCIP mode- not a bug

[Harlikwin]

The AV-8B with the 'moving map' (TAMMAC) has DTED (Digital Terrain Elevation Data).

 

 

 

However, AFAIK this :

 

 

 

... looks to be correct, at least for CCIP ?

 

Where

 

• GPS altitude - Radar altitude = Target Elevation.

 

or without GPS

 

• Barometric altitude - Radar altitude = Target Elevation.

 

is used with the HUD/aircraft attitude, Line of Sight angle to calculate a bomb solution.

 

Right, if you are using the ARBS "correctly" it should be fine, put the TDC on/near target and it should have a slant range and HOT. Also it should be possible to do it wrong and select a target point at the wrong altitude and miss (i.e. select mountain top and then bomb in a valley 1000m lower, bombs should land long).

 

I'm mainly wondering about cases when you don't do this in which case the MC should have to use radar alt and a flat earth assumption for the target alt with those inherent issues. But I think I should have to switch on the radar altimeter for that to work?

 

Alternately I could see it working like in the A10 where it has DTED data work from, but there is no documentation of that that I can find. And based on the dates of the two manuals, I would "guess" that the moving map/DTED was probably a 90's era modification (I found a paper from 1998 talking about it) not a post 2002 mod.

Edited February 21, 2019 by Harlikwin

[tom_19d]

I'm late to the discussion and new to the AV-8, but I believe part of this issue and something that might not be currently modeled is the HUD annunciation for the altitude source.

 

I'm working from Volume 1 of the TAC, Change 2 dated Aug 2002. Page 2-56 shows that in CCIP mode, if the ARBS is the altitude source, CCIP will be the HUD annunciation. If RADAR alt is used, it will show RCIP on the HUD, GCIP for GPS derived altitude, and BCIP if baro alt is the source. I'm away from my machine, but I don't believe I have seen this modeled in the DCS aircraft. If this is modeled, it would give us insight to what the aircraft is trying to use to solve the triangle.

[Harlikwin]

Hi Tom,

 

Yeah, as far as I know the symbology isn't correct at the moment. But yes per the tac manual it should read as you state. In terms of alt sources for CIP/Auto I've seen Rauto and Bauto modes (Rauto pops up under 4k AGL IIRC), never seen Gauto which should be the #2 choice behind the ARBS from my reading of the tacman.

 

The other corresponding bit of info is what target alt is displayed on the stores page. I can get that to change using the ARBS or waypoints/bomb points, but I'm not sure it actually is what the computer is using for CCIP hence my first post about if that reads 0 and the target is actually at 3k the bombs should miss by a good margin.

[tom_19d]

Right on, if I am looking at it correctly on page 2-2 of the TAC, I think for a NA Harrier the precedence order for altitude source is ARBS/RADAR ALT/GPS/BARO, but regardless I get what you are saying. Also I seem to remember seeing somewhere that to use GPS it is actually an ODU selection, but I can't source that at the moment.

 

When this trip is over and I am back by my machine I will be doing some testing with the scenario you posed and report back.

[Harlikwin]

Tac:

 

1.12.10.1 Using GPS Altitude. An option to

use GPS altitude to derive the aircraft height

above target has been added when the ALT

option is selected on the UFC. When ALT is

selected, a GPS option is displayed on the ODU

in addition to the BOMB and PUC options. See

Figure 1-175. GPS altitude is considered the

second most accurate source of aircraft altitude

following radar altimeter altitude and ahead of

ADC baro-corrected altitude. If both the BOMB

and GPS options are selected, radar altimeter, if

valid, is used to determine height above target.

The A/G weapon delivery mode legend in the

HUD reflects that GPS altitude is being used by

displaying GCIP in CCIP mode and GAUT in

Auto mode. When using GPS altitude in CCIP mode, the waypoint / waypoint offset

elevation is subtracted from GPS altitude to

derive the height above target. When using GPS

altitude in Auto mode to derive height above

target, the MC uses a two phased approach. In

the first phase, the GPS altitude is used directly;

subtracting waypoint / waypoint offset field

elevation from GPS altitude. In the second phase

that begins at 15,000 feet slant range from the

target, the height above target is computed by

integrating aircraft vertical velocity.

If the GPS vertical error exceeds the threshold

limits at any point during the attack, GPS altitude

is no longer used. The GCIP or GAUT

weapon delivery mode legend changes accordingly

to reflect the new source being used to

derive the aircraft height above target.

 

It would be nice to see but also I don't think its modeled the WRD button on the stores page does this:

 

1.14.5.3.11 Weapon Release Data Option

Pushbutton. Actuating the weapon release data

(WRD) option pushbutton boxes the WRD legend

and enables the weapon release data display.

The weapon release data display shows the

release data at pickle for a CCIP delivery and

release data at the moment the release cue

touches the velocity vector for an AUTO delivery.

See Figure 1-192. The release data for ripple

is calculated for the first bomb in the stick.

The values of the various parameters are

shown as they were during the last weapon

release. The speed values (aircraft airspeed and

wind) are in knots, altitude is in feet MSL, flight

path is in degrees, normal acceleration is in g's,

time-of-fall is in seconds, steering error is in mils

(AUTO mode only), and ranges are in feet. The

X, Y, and Z parameters are defined as follows:

1. Range X - horizontal range in direction of

flight

2. Range Y - cross range in direction of flight

3. Range Z - altitude (AGL) at release

4. Wind X - head/tail wind component

5. Wind Y - crosstrack wind component

Each subsequent release replaces the currently

recorded data. Weapon release data is not

stored in the A/A master mode, backup delivery

modes (DSL, DSL (1), DIRECT), or in a ªhot

gunº condition. Deselecting the weapon release

data option unboxes the WRD legend and

returns the display to the previous stores display.

On Day/Night Attack aircraft, WRD data is

automatically stored in the DSU for each weapon

release. The DSU requires down loading following

the flight to retrieve this data as it is not

stored in a data file.

 

Also, I think the symbology doesn't really update since I pretty much see Bauto/BCIP (that or I'm doing it wrong)

 

2.2.1.6 Day and Night Attack Aircraft. On

these aircraft, height above target determination

and the A/G weapon delivery mode altitude

Figure 2-7. Height-Loop Update

NWP 3-22.5-AV8B, Vol. I

2-7 CHANGE 1

source legends in the HUD are, in order of

precedence: ARBS, radar altimeter, GPS, and

barometric altitude. When tracking is achieved,

the ARBS is the primary source for height above

target information. The ARBS is primary

because it is not subject to barometric inconsistencies,

and it is not affected by changing terrain

features between the aircraft and the target. Use

of the ARBS by the MC in computed weapon

delivery modes is denoted on the HUD by the

AUTO or CCIP legends.

An option to use GPS altitude to derive height

above target is available on the ODU when the

ALT option is selected on the UFC. The GPS

option is displayed in addition to the BOMB and

PUC options on the ODU. The GPS altitude is

used as height above target if the GPS option is

cued and its outputs are valid and ARBS is not

tracking and radar altitude is not valid (BOMB

option not cued). If both the BOMB and GPS

options are selected, radar altimeter, if valid, is

used to determine height above target. The A/G

weapon delivery mode legend in the HUD

reflects that GPS altitude is being used by displaying

GCIP in CCIP mode and GAUT in

AUTO mode.

If the GPS vertical error exceeds the threshold

limits at any point during the attack or if GPS is

deselected, GPS altitude is no longer used. The

GCIP or GAUT weapon delivery mode legend

changes accordingly to reflect the new source

being used to derive the aircraft height above

target.

The radar altimeter is used for height above

target if the BOMB option is cued and the

outputs are valid (i.e., aircraft altitude £ 5,000

feet. AGL). Use of radar altimeter altitude by the

MC in computed weapon delivery modes is

denoted on the HUD by the RAUT or RCIP

legends.

If none of the other sources are used, the

system uses barometrically derived target altitude

(BARO). Use of barometric altitude by the MC in the INS computed bomb delivery modes

is denoted on the HUD by the BCIP or BAUT

legends.

[Nealius]

Something feels weird in CCIP since the last OB update. I used to be able to nail T-90s with a pair of Mk82s, but now I am consistently missing them by 10-30ft.

[Nealius]

Update:

 

This is bizarre. One mission I'll be plinking tanks with CCIP, and the next mission I will be hitting 100' long despite hitting pickle 100' early. With the wind, against the wind, crosswind, same results.

 

Now, what I did notice was that every time I had misses, I was over an urban area where my framerates were a bit lower (30s-40s). When my bomb accuracy was good, I was in desert areas with high framerates.

[Vfa-81 Fix]

Update:

 

This is bizarre. One mission I'll be plinking tanks with CCIP, and the next mission I will be hitting 100' long despite hitting pickle 100' early. With the wind, against the wind, crosswind, same results.

 

"How bizarro is this?"

"Bizarro!?!"

 

Made a quick test dropping some into downown Dubai. 3 times 45DB2, 2 hits, 1 shack. So I´d say all is fine on my end.

My computer isn´t the newest either but I never ever look at my fps.

[Harlikwin]

Update:

 

This is bizarre. One mission I'll be plinking tanks with CCIP, and the next mission I will be hitting 100' long despite hitting pickle 100' early. With the wind, against the wind, crosswind, same results.

 

Now, what I did notice was that every time I had misses, I was over an urban area where my framerates were a bit lower (30s-40s). When my bomb accuracy was good, I was in desert areas with high framerates.

 

Have you noticed wind drift affecting CCIP runs? I.e. full 90 deg crosswind and the bombs either land on target, or miss? And were you using the DMT/ARBS/Tpod for target designation when you did it?

Edited February 25, 2019 by Harlikwin

[Nealius]

Normally the CCIP pipper adjusts for wind, though I only really notice it when using high-drag bombs. I've had mixed results with TPOD designation: one mission I'll have 100% accuracy, the next mission I'll have 0% accuracy. In the past I would have good accuracy regardless of using DMT or not. I find the DMT a pain in the ass to work with (too much zoom, no FLIR, slewing is slow as hell) so I either just DESG the target waypoint or use TPOD.

[johnv2pt0]

I don't even bother using rockets when there's any wind because the CCIP does the behavior you're describing. It'll compensate the wrong direction making your shots double off the opposite...if that makes any sense.

 

 

 

CCIP is bugged...lots of things are coded wrong. It's frustrating and likely will not get fixed any time soon.

[Harlikwin]

Well, in "theory" IRL

 

IF you have Tpod or DMT lock on the actual target...

 

The ARBS should try to compensate at dive angles over some level when it kicks on (20deg (IIRC)) basically calculating both target movement and wind drift using its own understanding of relative target slant range angle change relative to the INS. (plane MC "knows" where the plane is and how its pointed, knows from the ARBS were the target is, "understands" the rate of change of change as "wind" (even if its tgt movement).

 

 

IF not locked on to anything, then CCIP mode has no way of knowing what wind drift is since its not actually "relative" to anything. For CCRP releases it tries to use INS drift data relative to whatever the designated waypoint/bombpoint using similar logic if I recall the tac manual correctly.

[Nealius]

I thought ARBS was always on? I don't recall seeing an ON/OFF switch for it.

[Captain Orso]

How about the SSS - Sensor Selector Switch ;)

[Nealius]

When on bombing runs without the TGP my right display is the EHSD and the left display is STRS.

 

Today I experimented a little and found that I really do need to lock the DMT onto a target to get good CCIP accuracy. The problem is that the DMT slewing is absolute trash. A snail could crawl across my HUD faster than that damn thing.

[Holbeach]

Lock it to the target with fp marker, then fine tune it with the DMT slew.

..

[Nealius]

The DMT isn't in-line with the VV though.

[Harlikwin]

I thought ARBS was always on? I don't recall seeing an ON/OFF switch for it.

 

I guess I need to be more precise with the nomenclature.

 

ARBS is the angle rate bombing system. It uses angle rate changes from the DMT in either TV or laser spot mode to calculate a slant range to the target and then sends that target info to the MC (bombing computer). If the ARBS isn't locked on anything, or locked on the wrong thing, you should get either a wrong or no solution from it to feed to the target computer.

 

Bombing computer (MC) is always on (I think). It takes inputs from the INS (where the plane is and were its going) plus information from the other sensors (ARBS/TPOD/INS waypoints) to calculate a drop solution.

 

For CCIP if there is nothing coming from the sensors it defaults to calulating a flat earth solution and assumes the tgt is at ground level (i.e. radar altimiter). Sometimes it doesn't know where the ground is however (baro alt mode) unless input by the pilot (which you can't do at the moment).

[Harlikwin]

When on bombing runs without the TGP my right display is the EHSD and the left display is STRS.

 

Today I experimented a little and found that I really do need to lock the DMT onto a target to get good CCIP accuracy. The problem is that the DMT slewing is absolute trash. A snail could crawl across my HUD faster than that damn thing.

 

That is good news (at least from my POV). You should have to have a decent DMT lock on target to have good accuracy.

 

I was able to get pretty close hits with DMT lock, and the alt set to zero and the target at 3k and I still almost hit it...

Edited February 26, 2019 by Harlikwin

[Holbeach]

The DMT isn't in-line with the VV though.

 

 

I don't quite know what you mean there, but I get pretty much 100% hits in CCIP without ground lock and at any altitude.

 

 

In a shallow dive, always keep the Flight Marker on the same spot and let the cross walk to the target, you can't miss.

 

I find Low S&L not so accurate.

 

 

If you have ground lock, you can quickly convert to CCRP if required.

 

 

GL..

[Shadow_1stVFW]

I don't quite know what you mean there, but I get pretty much 100% hits in CCIP without ground lock and at any altitude.

 

 

In a shallow dive, always keep the Flight Marker on the same spot and let the cross walk to the target, you can't miss.

 

I find Low S&L not so accurate.

 

 

If you have ground lock, you can quickly convert to CCRP if required.

 

 

GL..

 

From my testing the DMT aligns with the Wind Corrected VV (Ghost VV) You can see this by depressing TDC while in NAV mode with a significant cross wind. In AG mode the VV is wind corrected so you won't see a ghost and you won't have an issue. But in VTOL and NAV modes the VV's are not wind corrected and you can see the DMT clearly locks based on the Ghost VV in NAV mode.

(This is one of the reasons I so badly want the VV fixed, that and in VTOL mode in a turn it's pretty useless.)

[Harlikwin]

I don't quite know what you mean there, but I get pretty much 100% hits in CCIP without ground lock and at any altitude.

 

Yeah, you probably shouldn't be able to do it though.

[Nealius]

I don't quite know what you mean there, but I get pretty much 100% hits in CCIP without ground lock and at any altitude.

 

 

In a shallow dive, always keep the Flight Marker on the same spot and let the cross walk to the target, you can't miss.

 

I find Low S&L not so accurate.

 

 

If you have ground lock, you can quickly convert to CCRP if required.

 

 

GL..

 

30-40 degree dive, Flight Marker on an aim-off point just beyond the target, flying for 1G and 450-460kts. Good CCIP cue, pickle. Bombs fall long, even if I pickle 100' short.

 

Oddly, there was one instance where I scored a direct hit by "putting the thing on the thing", but the CCIP cross was invalid at the time. So I'm missing with valid CCIP solutions and putting bombs in a pickle barrel with invalid CCIP solutions :huh:

[Harlikwin]

:music_whistling:

30-40 degree dive, Flight Marker on an aim-off point just beyond the target, flying for 1G and 450-460kts. Good CCIP cue, pickle. Bombs fall long, even if I pickle 100' short.

 

Oddly, there was one instance where I scored a direct hit by "putting the thing on the thing", but the CCIP cross was invalid at the time. So I'm missing with valid CCIP solutions and putting bombs in a pickle barrel with invalid CCIP solutions :huh:

 

 

 

 

 

But I'm sure someone will send you a sternly worded message with the title "does it matter? I mean really does it matter?"

 

I'm sure the top programmers are on it though :music_whistling:

 

Edited February 27, 2019 by Harlikwin

[Holbeach]

30-40 degree dive, Flight Marker on an aim-off point just beyond the target, flying for 1G and 450-460kts. Good CCIP cue, pickle. Bombs fall long, even if I pickle 100' short.

 

Oddly, there was one instance where I scored a direct hit by "putting the thing on the thing", but the CCIP cross was invalid at the time. So I'm missing with valid CCIP solutions and putting bombs in a pickle barrel with invalid CCIP solutions :huh:

 

 

I checked my videos from yesterday and dives were a max of 25 deg, usually less. Speed 510/550, engine 100%, targets at 500' and 3500' asl and designated. All accurate when the cross was on the dot. CCRP was also accurate when done correctly. (No wind).

 

 

 

At 40 deg. it was much harder to aim and less time to do it, but the result was the same.

 

 

Try a shallow dive, you might get better results.

 

 

GL..

Edited February 27, 2019 by Holbeach