DCS F-18 - Automatic Flight Control System (AFCS)

[VBF-12 Gosling]

So, there are no stupid questions in aviation...

Here is one. How do I disengage the AFCS?

Answer. Use the AFCS Disengage paddle switch (it's the one we use ALL the time to line up - ie the NWS disengage switch) - WOW DERRRR

So, that and Whitey realising that A2A Refueling is SOOO much easier having engaged and disengaged the AFCS :BALT Hold.

It was time to read the book again....

Now this is quite a subject (probably the reason I haven't tackled it until now) so will be in small chunks in a few posts, so please do NOT reply here, just yet.

Also, Note that this should be read in conjunction with the Auto Throttle Control thread (yet to be written).

[VBF-12 Gosling]

AUTOMATIC FLIGHT CONTROL SYSTEM (AFCS)

From the Book - Aircraft Manual - info.publicintelligence.net/F18-ABCD-000.pdf
AFCS = Part I, Paragraph 2.9

MODES
The automatic flight control system (autopilot) has two basic modes: Pilot Relief and Data Link.
- The DCS F-18 has yet to get the Data Link mode which drive the Automatic Carrier Landing System (ACLS).

What We Have:
The current F/A-18C pre-release has:

• Control Stick Steering (CSS) - Basic
• Attitude Hold - :ATTH
• Heading Hold - :HSEL
• Barometric Altimeter Hold - :BALT
• Radar Altimeter Hold - :RALT/li]
  

What We DON'T Have:
At this stage (Jul 2020) is:

• Coupled Steering - :CPL, which would have given us:
  • Azimuth Steering Line Couple (ASL) - This would keep us on the selected course (CSE)
  • Bank Angle Control (BNK) - Not sure, but I suspect this assists in maintaining the other selects
  • Coupled Waypoint Steering (WYPT) - This would allow auto flight direct to waypoints
  • Coupled Auto Sequential Steering (SEQ(n)) - This would support following the sequenced waypoints of a flight plan
  • Coupled TACAN Steering (TCN) - This would allow flight direct to a TACAN
• Data Link mode, including:
  • Automatic Carrier Landing (ACL) - Which guides your aircraft on the ACLS
  • Precision Course Direction
  • Vector Approach

CONTROLS

• Up Front Control (UFC)
• Heading Set Switch - HDG
• Course Select Switch - CSE
• Autopilot Disengage / Nose Wheel Steering Switch

LIMITATIONS
To engage any autopilot mode the following limits need to apply:

• Angle of Bank - < 70 Deg
• Pitch - < 45 Deg Nose up or Down

[VBF-12 Gosling]

PILOT RELIEF MODE

This is main mode we can use in the current pre-release.

OPERATION - Engagement
Basic - Pitch Attitude
Aircraft ... Fly to Req'd Pitch Attitude
UFC A/P ... Select + ON
Left DDI ... A/P & AUTO PILOT
Req'd Pitch Attitude ... Maintained
NOTE: If AoB <+/- 5 Deg then current Mag Hdg is also maintained

Attitude
Aircraft ... Fly to Req'd Attitude
UFC A/P ... Select + ON
UFC ATTH ... Select
:ATTH ... Check
Left DDI ... ATTH & AUTO PILOT
Req'd Attitude ... Maintained

Heading
HDG SW ... Set Required Heading
UFC A/P ... Select
UFC HSEL ... Select
:HSEL ... Check
Left DDI ... HSEL & AUTO PILOT
Aircraft 30 Deg AoB Turn ... Check
Req'd HDG ... Check Roll Out on HDG

Barometric Altitude
Aircraft ... Fly to Req'd Altitude
UFC A/P ... Select
UFC BALT ... Select
:BALT ... Check
Left DDI ... BALT & AUTO PILOT
Req'd Attitude ... Maintained

Radar Altitude
Aircraft ... Fly to Req'd Altitude
UFC A/P ... Select
UFC RALT ... Select
:RALT ... Check
Left DDI ... RALT & AUTO PILOT
Req'd Attitude ... Maintained

DDI Advisories are displayed for 10 seconds

OPERATION - Disengagement
Single Mode
UFC Mode ... Select
" : " ... Check decolonised from Mode

All Modes - Intended
Stick Paddle SS ... Press

All Modes - Urgent
Flight Control ... Fly through holds
NOTE: This will cause significant control disturbance and possible Pilot Induced Oscillation (PIO)

[VBF-12 Gosling]

A/P CONTROL

This is the important post of this thread!

BASIC
Once the A/P is engaged (ON) the control at limited by the Control Stick Steering (CSS) and responds slowly, requiring significant flight path anticipation.

Control in Pitch
Pitch attitude can be set between +/- 45 deg by:
Stick - Small control movements to NOT cause an Urgent Disengagement
Trim SW - This will change the pitch at 0.5 degrees / sec

Control in Roll
Roll can be set between +5 and +70 deg
- Roll attitude must exceed 5 degrees, or it will roll back to hold Mag Hdg
Stick - Small control movements to NOT cause an Urgent Disengagement
Trim SW - This will change the pitch at 2.0 deg / sec

Control of Magnetic Heading
Using Roll of less than 5 deg AoB will alter the held Magnetic Heading Reference

UFC MODES
ATTH
Maintains Pitch and Roll Attitude
Pitch - +/- 45 Degrees, changeable at 0.5 deg / sec
Roll - +/- 70 AoB, changeable at 2.0 deg / sec

BALT
Aircraft altitude will be maintained with reference to BarAlt height, between 0 and 70,000 ft
Can be combined with ATTH and HSEL (Also, CPL but not this pre-release)

HSEL
Aircraft will turn to the heading selected using the HDG SW turning the4 shortest way using 30 deg AoB
Pitch Attitude is maintained
Can be combined with ATTH and BALT (Also, CPL but not this pre-release)
Heading can be altered using the HDG SW.
NOTE: Avoid selecting a heading beyond astern as the aircraft will reverse its turn to the shorter direction.

RALT
Aircraft altitude will be maintained with reference to RadAlt height within 0 to 5.000 ft
Magnetic Heading will be maintained if no other hold is engaged
Roll can be controlled by stick or trim up to 45 deg AoB, with automatic turn co-ordination
Can be combined with ATTH and HSEL (Also, CPL but not this pre-release)

Although not stated in the Manual, I suspect selecting RALT whilst :BALT is engaged will disengage BALT and engage :RALT ?

[VBF-12 Gosling]

A/P USE - CASE I

Again another important thread.

So, how do we use this. Let's look at a Case I recovery...

Case I
By 10 nm be at required BarAlt height:
A/P ... ON
BALT ... Select :BALT
IAS ... Set 250kts IAS
ATC ... ON (ATC in HUD)
CSE ... Set BRC

Approaching the carrier:
Consider which Position you will arrive using CSE Line
HDG ... Set Position - 90 deg
EG Position 3:
- Fly t reciprocal of BRC
- HDG SW ... Set Reciprocal - 90

At Arrival Position:
HSEL ... Select :HSEL
30 Deg to go
HDG SW ... Select next 90
Hook ... Down

Signal Charlie:
HDG SW ... Set BRC - 150 for outbound

When rolling out on outbound track:
ATC ... Deselect
Pitch ... Trim Down 5 deg (anticipate as this will take 10 secs)
Accelerate to 350 kts IAS:
ATC ... Select (and adjust throttle to approximate position as out throttles don't move themselves)
At 800 ft:
RALT ... Select :RALT (assuming it will overide :BALT)
At 8 nm DME:
HDG SW ... Select BRC

Inbound:
CSE Line ... Confirm on TRK
At 3 nm, Call "Initials"

At 1.3 nm DME past carrier:
PADDLE SW ... Press
ATC ... OFF
Throttle ... Idle
Fly the pattern to the groove and land.

I have yet to try to use any A/P Modes to help with the 600 ft Onspeed or the final turn etc.

[VBF-12 Gosling]

A/P USE - CASE III

We all know the Case III profile is complicated and tough to fly. A/P can help alot....

Case III

So we are heading to the carrier and Call "Inbound"

Marshal will give us the BRC, Final Bearing, Radial, Range, Altitude and Push Time.
EG 270, 260, 090, 21nm, 6,000, 50

The time now is minute 37.
Fly to the Height ... 6,000 ft (RadAlt always selected at sea, so flashing B)
A/P ... ON
BALT ... Select :BALT (Because RALT only works below 5,000 ft)
CSE SW ... BRC
HDG ... Reciprocal of BRC
Fly to a point just UNDER 20 nm astern of the carrier (Half the range on the 40 nm range scale)

Approaching the 20 nm point.
IAS ... 250 kts
Afterburner Detent ... ON
ATC ... Select (ATC in HUD)
HOOK ... DOWN
HSEL ... Select HSEL (Aircraft turns outbound - Aim to have a spacing of 4 nm right of outbound CSE Line)

Passing 21 nm DME outbound
Cal "Established"
Clock in HUD ... Note time (Eg 41:00)
40 Sec post 21 nm DME
HDG SW ... Left onto BRC (aircraft turns at 30 deg AoB - Diameter is about 4 nm at 250 kts and takes about 1:40)
Inbound to 21 nm
HDG SW ... 5 deg L/R (to get CSE track offset to 0)
Clock ... Check Time (44:00) - (One more time around the hold = 6:00 mins)
HDG SW ... Left onto Reciprocal of BRC
Clock ... Time (45:40)
Off Track Distance ... Check 4 nm
40 Sec Later
HDG SW ... Left onto BRC

Inbound to 21nm
HDG SW ... L/R 5 Deg for Off Track Distance = 0
Approaching 21 nm
Throttle ... IDLE (will cause ATC Cruise Mode disengagement - See ATC)
Pitch Trim ... Down to 8 deg Nose Down (16 seconds!!!)
RoD ... Check 4,000 fpm
250 Kts
ATC ... ON (Engaged ATC Cruise Mode again)
5000 ft, Call "Platform"
Pitch Trim ... Up to 4 deg Nose Down (8 secs)
RoD ... Check 2000 FPM
HDG SW ... Right 10 Deg (10 clicks)
ATC ... OFF
Gear ... Down
220 Kts
Flaps ... HALF
200 Kts
Flaps ... FULL
ICLS Azimuth ... Centre
HDG SW ... 4 Deg Right of Final Bearing (264 Deg)
E Bracket ... Onspeed and Trim - There is an option to use ATC Approach Mode here
Passing 1500 ft
Throttle ... Creep up to level flight path vector (Creep means mov each throttle against the other inching them up left right by tiny amounts)
1200 ft
RALT ... :RALT
HDG SW ... L/R 1-2 deg (Clicks) to maintain ICLS Azimuth
6 nm Glide Path, Say "Needles"

Await glide path to come down to Flight Vector
Throttle ... Creep down to rate of descent about 600 fpm (on glide slope)
IFLORS ... Check Ball
Ship ... Check Amber Stern Light
HDG SW ... L/R 1 deg (click) as required to remain centre
Throttle ... Creep to stay on Glideslope
Trim ... Single click to stay Onspeed

< 1 nm to go
A/P ... OFF (Paddle Switch)
Azimuth ... Slight Roll
Glideslope ... Creep Power
Flight Path Vector ... Right End of Deck / Runway Lights

NOTE: Don't stop trying to keep the IFLORS Centre (Error one up / NOT one down)

THUD

Throttle ... MIL

[VBF-12 Gosling]

A/P USE - AIR TO AIR REFUELING

This is straight forward

Together with all the usual A2A Refuel Checks

Once at the waiting station...
A/P ... Select & ON

No need to select any modes. the CSS will be working and the control rates will be greatly reduced.