JT — Weapon Ordnance Definition (.JT)

FA_2.LIB contains 135 .JT files. Each defines one weapon/ordnance type (missiles, bombs, guns, rockets). BRF plain text (NOT a Win32 PE DLL); decompressed sizes vary (e.g. AIM9M.JT = 2775 bytes). Loaded at runtime by the FA object system.

Tools

fx

fx jt info   <file.JT>               # human-readable field dump
fx jt unpack <file.JT> [-o out.txt]  # editable text
fx jt pack   <in.txt>  -o out.JT     # write back (byte-identical)

File Layout

Plain text; BRF syntax (see BRF.md). Two-section structure: OBJ_TYPE (physical object base) followed by PROJ_TYPE (projectile/seeker).

Section 1: OBJ_TYPE

[brent's_relocatable_format]

;---------------- START OF OBJ_TYPE ----------------
;---------------- general info ----------------

    byte 7                  ; object category (7 = projectile)
    word 315                ; hitpoints
    word 52                 ; object subtype ID
    ptr ot_names
    dword $6                ; capability flags
    word $80                ; flags2
    ptr shape               ; 3D model reference
    dword 0                 ; (12 reserved dword/word fields)
    ...
    dword 1983              ; year introduced
    word 59                 ; (additional physics params)
    word 0
    word 100 ... word 100   ; (performance percentages)
    byte 30                 ; (more params)
    byte 3
    dword 190
    word 0

;---------------- movement info ----------------

    word 0 ... (speed/accel/maneuver params)
    symbol _PROJProc        ; utilProc (projectile physics callback)

;---------------- sound info ----------------

    ptr loopSound
    dword 0 ... (sound attenuation params)
    (word values for sound range/falloff)

Section 2: PROJ_TYPE

;---------------- START OF PROJ_TYPE ----------------

    dword $1204f            ; warhead/capability flags
    word 1                  ; warhead count
    byte 10                 ; seeker type
    ptr si_names
    word 0                  ; seeker flags
    byte $0                 ; sub-type
    byte 2                  ; seeker mode (0=unguided, 1=radar, 2=IR, etc.)
    byte $0
    byte 0 ... (8 bytes target-selection params)
    ; Seeker lobe 1 (primary):
    word 8190               ; azimuth half-angle
    word 8190               ; elevation half-angle
    dword ^0                ; min range
    dword ^50000            ; max range
    dword $80000000         ; min heading error
    dword $7fffffff         ; max heading error
    ; Seeker lobe 2 (secondary):
    word 8190
    word 8190
    dword ^4000
    dword ^24000
    dword $80000000
    dword $7fffffff
    ; Warhead/agility params (many byte values):
    byte 50 ... byte 85
    ; Fire params:
    word 546 word 1 word 16
    byte 100 ... byte 34
    ptr fireSound
    word 6000 word 0 word 750 word 35

Labels Section

:ot_names
    string "AIM-9M"                ; short display name
    string "AIM-9M Sidewinder"     ; long display name
    string "AIM9M.JT"              ; filename (self-reference)
:shape
    string "sidem.SH"              ; 3D shape file
:loopSound
    string "&missile.11k"          ; looping motor sound
:si_names
    string "AIM-9M"                ; (duplicate of ot_names)
    string "AIM-9M Sidewinder"
    string "AIM9M.JT"
:fireSound
    string "&ltmiss.11k"           ; launch sound
    end

Notes:

• Gun rounds (e.g. GAU8.JT) use seeker mode byte=0 (unguided), wide cone angles (word 16380), and short ranges.
• Missiles use narrow cones and long ranges.
• The ~ prefix (e.g. ~BLDR.JT, ~MOOSE.JT, ~MOTHB.JT, ~VOMIT.JT) indicates theater-specific or campaign-specific weapon variants.

Warhead capability flags (dword)

Confirmed flags from cross-referencing weapon types:

Weapon	dword value	Role
AIM-9M/X, AIM-120	$1204f	Air-to-air missile
AGM-65G, AGM-84A	$2a06f	Air-to-ground missile
MK-82	$22012	Unguided bomb (AG)
20mm cannon round	$0348c4	Gun (AA + AG)

The flags dword is loaded as-is into the runtime missile entity at missile+0xa6. At launch, the engine OR-assigns runtime state bits into the same field: - $1204f (AIM-9M, AIM-120): bit 16 set → starts in search mode, transitions to 0x20000 on acquisition - $2a06f (AGM-65G): bit 17 set → starts in track mode (fire-and-forget, locked before launch)

Confirmed bit roles from _PROJLock@24 (0x004c2f20), _PROJHitChance@28 (0x004c3380), @HARDFindJammer@4, _DAMAGEDoHit@12 (0x0040f970), _PROJMoveProc (0x4c11b0), and _PROJAdd_40:

Bit	Hex	Meaning	Evidence
0	0x000001	Guided missile / rocket marker	_DAMAGEDoHit@12: bit 7=0 AND bit 0=1 → play missile-hit sound; AIM-9M 0x4f has bit 0=1 ✓
1	0x000002	Precision/CEP control: if set, 75% chance no scatter at launch; if clear, scatter always applied	_PROJAdd_40: (flags & 2) == 0 \|\| !_Percent_4(75%) → randomize bomb impact point; missiles have bit set (low CEP), unguided bombs clear (always scatter)
4	0x000010	Pk modifier gate	_PROJLock@24 range-based Pk calc
5	0x000020	Guidance algorithm selector: 0 → FUN_004c1630 (standard pursuit), 1 → FUN_004c1660 (alternate)	_PROJMoveProc: if ((flags & 0x20) == 0) FUN_004c1630() else FUN_004c1660()
6	0x000040	Engine/propulsion tracking: when set, _PROJEngineState_0() runs each tick and adjusts thrust speed per phase (boost/cruise/coast)	_PROJMoveProc: if ((flags & 0x40) != 0) { engine_state → speed update }
7	0x000080	Cannon / gun-round marker	_DAMAGEDoHit@12: bit 7=1 → play gun-hit sound; 20mm 0xc4 has bit 7=1 ✓
9	0x000200	Dual-lobe seeker lock processing	gates search/track lobe dispatch in _PROJLock@24
10	0x000400	Active-radar / special guidance mode	gates PushCurObj + HARDBestSeeker in _PROJLock@24
12	0x001000	Seeker re-acquisition far-range bias: when set, initial CF70 (re-acq distance) set at 75–100% of launch distance (90% roll)	_PROJAdd_40: (flags & 0x1000) != 0 && _Percent_4(90%) → CF70 = rand[75%, 100%] × launch_dist
13	0x002000	Seeker re-acquisition near-range bias: when set (bit 12 check failed), initial CF70 set at 0–25% of launch distance	_PROJAdd_40: (flags & 0x2000) != 0 && _Percent_4(90%) → CF70 = rand[0%, 25%] × launch_dist
16	0x010000	Air-to-air capable / search-mode init	AA missiles and 20mm; @HARDFindJammer@4
17	0x020000	Air-to-ground capable / track-mode init	AG missiles, bombs, and 20mm
21	0x200000	Lock-count reduction modifier	_PROJHitChance@28

Hit-sound dispatch (_DAMAGEDoHit@12 projectile-type case):

if ((warhead_flags & 0x80) != 0)      → gun-hit sound    (20mm: 0xc4 has bit 7)
else if ((warhead_flags & 0x01) != 0) → missile-hit sound (AIM-9M: 0x4f has bit 0)
else                                  → bomb-hit sound   (MK-82: 0x12 has neither)

Bits 2–3 of the lower byte are present in consistent category-level patterns across all 135 .JT files but no function in the full the game executable decompile or any analyzed overlay DLL tests them individually. Remaining inferred assignments:

Bit	Hex	Inferred pattern	Notes
2	0x000004	Set for missiles, rockets, and gun rounds; clear for gravity bombs	Possible "active ordnance" marker
3	0x000008	Set for guided missiles and gun rounds; clear for most unguided weapons	Possible "terminal-guidance capable" marker

Bits 1, 5, and 6 were previously listed as inferred — all three are now confirmed from _PROJMoveProc / _PROJAdd_40 decompile and moved to the confirmed table above.

Seeker mode byte — confirmed

Matches the SEE seeker type byte:

byte	Guidance	Confirmed weapon
0	Unguided	MK-82.JT, 20MM_4.JT
1	Laser-guided	(see *L.SEE laser files)
2	IR / EO homing	AIM9M.JT, AIM9X.JT, AGM65G.JT
3	Radar (semi-active / active)	AIM120.JT, AGM84A.JT

Range unit in PROJ_TYPE

The ^ range values in PROJ_TYPE seeker lobes use the same 1-foot unit as SEE files. Confirmed data points: - AIM9X lobe 1 max ^50000 = 8.2 nm; AIM-9X ~8 nm ✓ - AIM120 lobe 1 max ^144000 = 23.7 nm; AIM-120A ~25 nm ✓ - AGM84A lobe 1 max ^360000 = 59.3 nm; Harpoon ~60 nm ✓

Agility / hit-probability bytes

The PROJ_TYPE section base is at missile+0xa6 in the runtime entity (confirmed entity base at cjt in the FA scratchpad; PROJ_TYPE base at DAT_0050d30e). Confirmed reads from _PROJHitChance@28 (0x004c3380), FUN_004c3960 (proximity fuze check), _PROJMoveProc (0x4c11b0), _PROJEngineState_0 (0x4c1170), FUN_004c17a0, and FUN_004c1660:

PROJ_TYPE offset	Global addr	Role (confirmed)	Source
+0x4F	DAT_0050d35d	Proximity fuze range (byte) — fuze triggers when target_arm_size ≥ this; below 50% = miss	FUN_004c3960
+0x55	DAT_0050d363	Min maneuver rate (short) — lower clamp in PROJSpeed velocity computation	PROJSpeed
+0x57	DAT_0050d365	Coast/glide speed — target speed during engine state 2 (coast phase, motor off)	_PROJMoveProc + _PROJEngineState_0
+0x59	DAT_0050d367	Boost phase end (ticks after launch) — transition from state 0 (boost) to state 1 (cruise)	_PROJEngineState_0
+0x5B	DAT_0050d369	Motor burnout threshold (ticks after launch) — transition from state 1 (cruise) to state 2 (coast)	_PROJEngineState_0
+0x5D	DAT_0050d36b	Max flight time / missile TTL (ticks) — missile self-destructs when elapsed ≥ this	_PROJMoveProc
+0x65	DAT_0050d373	Alt-guidance inner range threshold (byte) — if dist>>16 ≥ PROJ_TYPE+0x67 but < this, use inner speed	FUN_004c1660 (warhead bit 5=1)
+0x66	DAT_0050d374	Alt-guidance inner range speed (byte) — _CreateMove_52 speed at close range	FUN_004c1660
+0x67	DAT_0050d375	Alt-guidance outer range threshold (byte) — min distance for alt-guidance mode activation	FUN_004c1660
+0x68	DAT_0050d376	Alt-guidance outer range speed (byte) — _CreateMove_52 speed at far range	FUN_004c1660
+0x69	DAT_0050d377	Seeker search angular spread half-width (angle units) — used in _Rand_4 for scan jitter	FUN_004c17a0
+0x6B	DAT_0050d379	Search reacquisition interval (ticks) — added to _currentTime to set next scan-angle update	FUN_004c17a0
+0x6D	DAT_0050d37b	Active search window duration (ticks; 0 = disabled) — while elapsed < this, missile scans via random angles	_PROJMoveProc
+0x6F	DAT_0050d37d	Maneuver rate percentage (byte) — (this × input_rate) / 100; upper bound in PROJSpeed	PROJSpeed
+0x70	DAT_0050d37e	Smoke trail flags (bits 0–6 = trail count; bit 7 = continuous smoke flag)	_PROJMoveProc
+0x71	DAT_0050d37f	Smoke trail param 1 (passed to _GRAPHICAddSmokeAdder_40)	_PROJMoveProc
+0x72	DAT_0050d380	Smoke trail param 2	_PROJMoveProc
+0x73	DAT_0050d381	Smoke trail param 3	_PROJMoveProc
+0x74	DAT_0050d382	Smoke trail param 4	_PROJMoveProc
+0x75	DAT_0050d383	Pk at 0–25% of engagement range (byte) — Pk quartile table entry 0, read by FUN_004c3890	_PROJHitChance@28
+0x76	DAT_0050d384	Pk at 25–50% of engagement range (byte) — Pk quartile table entry 1	_PROJHitChance@28
+0x77	DAT_0050d385	Pk at 50–75% of engagement range (byte) — Pk quartile table entry 2	_PROJHitChance@28
+0x78	DAT_0050d386	Pk at 75–100% of engagement range (byte) — Pk quartile table entry 3	_PROJHitChance@28
+0x79	DAT_0050d387	Approach angle tolerance byte	_PROJHitChance@28
+0x7A	DAT_0050d388	Approach angle weight byte	_PROJHitChance@28
+0x7B	DAT_0050d389	Angular error weight byte (left-shifted 3 for angle table lookup)	_PROJHitChance@28
+0x7C	DAT_0050d38a	Counter-maneuver jam Pk reduction byte — lowers Pk by this %	_PROJHitChance@28
+0x7D	DAT_0050d38b	Altitude/range modifier weight byte	_PROJHitChance@28
+0x7E	DAT_0050d38c	Range gap modifier byte	_PROJHitChance@28
+0x7F	DAT_0050d38d	Pk adjustment byte (applied as signed % of base Pk)	_PROJHitChance@28
+0x80	DAT_0050d38e	Maneuver agility Pk bonus (ushort)	_PROJHitChance@28

File Inventory

Category	Examples
Missiles (IR/radar)	AIM-9M/X, AA-10/11/12, AM-39, R-530/550, MICA, HQ-61
Bombs	MK-82/84, GBU-10/28/29/30, FAB-250/500, PAVEWAY, CBU-87/89
Guns	GAU8, GAU12, GSH-23/30, M61, DEFA, ADEN, BK27
Rockets	LAU-10/61, B8, B13
SAM rounds	SA-2/3/6/7/9/13-16/19
Naval weapons	SSN-9, SEA_SPAR, ASROC
Campaign variants	~BLDR, ~MOOSE, ~MOTHB, ~VOMIT

All 135 live in FA_2.LIB.

Engine Notes

Engine state machine (_PROJEngineState_0 @ 0x4c1170, called from _PROJMoveProc when warhead bit 6 is set):

// Returns: 0 = boost, 1 = cruise (motor on), 2 = coast (motor off)
if (elapsed < PROJ_TYPE[+0x59]) return 0;   // boost phase
if (elapsed < PROJ_TYPE[+0x5B]) return 1;   // cruise phase
return 2;                                    // coast phase
// elapsed = _currentT − launch_time (ticks)
// PROJ_TYPE[+0x57] = coast speed target (used when state == 2)
// PROJ_TYPE[+0x5D] = TTL: missile removed when elapsed ≥ this

Seeker scan mode (enabled when PROJ_TYPE[+0x6D] != 0 and target entity type == aircraft): the missile enters a search scan phase while elapsed flight time < PROJ_TYPE[+0x6D]. Each PROJ_TYPE[+0x6B] ticks, FUN_004c17a0 generates a new random scan angle within ±PROJ_TYPE[+0x69] and applies it via _ObjPlusAngleParm_8. When elapsed ≥ +0x6D, scan angles are zeroed (passive flight until seeker acquires or TTL).

FUN_004c3890 (called by _PROJHitChance@28) is the Pk range-interpolation function. It reads the engagement range reference at PROJ_TYPE+0x31 (secondary lobe max range), divides it into quartiles, and linearly interpolates between the four Pk bytes at +0x75–0x78.

PROJSpeed is the velocity-clamp function: applies PROJ_TYPE+0x6F % to an input angular rate, clamps between PROJ_TYPE+0x55 minimum and OBJ_TYPE speed-limit fields at entity+0x67/+0x6b.

_PROJProc dispatch (confirmed via dumpAtForced):

// _PROJProc @ 0x4c1f50
undefined1 * _PROJProc(undefined1 param_1) {
    switch(param_1) {
    case 1: return &LAB_004c1f90;               // init/startup handler
    case 2: return &_PROJMoveProc;              // movement / physics update  (0x4c11b0)
    case 3: return &_PROJEventProc;             // event handler
    case 4: return &_PROJDamageProc;            // damage processing
    default: return NULL;
    }
}

Alternate guidance algorithm (FUN_004c1660 @ 0x4c1660, selected when warhead bit 5=1): reads the target entity position, computes distance, then selects guidance speed from a two-tier distance table (+0x65/+0x66 inner range, +0x67/+0x68 outer range) before calling _CreateMove_52 in positional mode. Falls through to FUN_004c1630 (standard pursuit mode) when distance is below the outer range threshold.

Physics scratchpad (0x50CE80–0x50D267): a separate fixed-address block preceding the entity struct (cjt base 0x50D268) holds per-tick missile motion state. Key globals confirmed from _PROJMoveProc full decompile:

Global	Role
DAT_0050ce91	Missile world position (passed as &pos to _DistToObj@8, _GRAPHICAddExp)
DAT_0050ce95	Remaining range accumulator — decremented by motor deceleration each tick
DAT_0050cf5e	Runtime state flags (bit 1 = acquired, bit 2 = fired, bit 3 = skip guidance, bit 4 = alt-guidance, bit 8 = seeker override)
DAT_0050cf62	Warhead sub-parameter (passed to _PROJLock@24, _PROJSendCollateralDamages)
DAT_0050cf64	Target entity slot ID (0 = no target; indexes _objPtrs[])
DAT_0050cf68	Phase timing reference — _currentT − this = elapsed ticks since phase start
DAT_0050cf70	Max seeker engagement distance (compared to iVar6 = _DistToObj result)
ram0x0050cf80	Motor deceleration accumulator (capped at 0x5000, subtracted from ce95 when bit 6 set)
ram0x0050cf82	Seeker scan azimuth angle (passed to @ObjPlusAngleParm@8)
DAT_0050cf84	Seeker scan elevation angle (passed to @ObjPlusAngleParm@8)
DAT_0050cf86	Guidance update timer — next scheduled scan angle update (compared to _currentT)

Sub-functions checked (all are one-liners, no gap field reads):

Function	Address	Body
FUN_004c1630	0x4c1630	_CreateMove@52(&DAT_0050ceb8, 0, 4, target_slot, 4, 0, 1, 0, 1, 0, 8, 0x10, 0x7fff) — standard pursuit, fixed params
FUN_004c17f0	0x4c17f0	Seeker acquisition eligibility: checks atmosphere layer bit 3 + sun/heading angle constraints; no PROJ_TYPE reads
FUN_004c1720	0x4c1720	_CreateMove@52(&DAT_0050ceb8, 0, 1, heading, 1, pitch, 1, roll, 1, 0, 8, 0x10, 0x7fff) — lock handler, uses missile own angles
FUN_004c1760	0x4c1760	_CreateMove@52(&DAT_0050ceb8, 0, 1, _sunAngle, 1, az, 1, roll, 1, 0, 8, 0x10, 0x7fff) — acquisition, sun-angle homing

Confirmed entity offsets 0xF0–0x16F (from DumpPROJDispatch run): the entity-relative offsets around the PROJ_TYPE base (missile+0xa6) were confirmed by scanning entity+0xF0–0x114:

Runtime offset	Role (confirmed)
entity+0xF0	Target ptr / target ID
entity+0xF4	Reaction param 0
entity+0xF6	Reaction param 1
entity+0xF8	Reaction param 2
entity+0xFA	Mode byte
entity+0x100	Primary per-frame state byte — most-polled field in the entity update loop
entity+0x101	Timeout / tick timer
entity+0x10C	Campaign context reference
entity+0x114	Init handle
entity+0x16F	HUD state flags (also DAT_0050cfef = player entity + 0x16F per HUD.md)

Open Questions

1. PROJ_TYPE bytes with zero the game executable xrefs

Full exhaustive search (Ghidra GUI): all four PROJ proc types decompiled (_PROJMoveProc, _PROJEventProc, _PROJDamageProc, guidance proc at LAB_004c1f90), all reachable sub-functions checked, and Ghidra xref on each gap global address — all returned zero references:

PROJ_TYPE offset	Global addr	Status
+0x50	DAT_0050d35e	Zero xrefs in the game executable
+0x51	DAT_0050d35f	Zero xrefs in the game executable
+0x52	DAT_0050d360	Zero xrefs in the game executable
+0x53	DAT_0050d361	Zero xrefs in the game executable
+0x54	DAT_0050d362	Not in _PROJMoveProc
+0x56	DAT_0050d364	Not in _PROJMoveProc — may be high byte of +0x55 (short)
+0x58	DAT_0050d366	Not in _PROJMoveProc — may be high byte of +0x57 (short)
+0x5A	DAT_0050d368	Not in _PROJMoveProc — may be high byte of +0x59 (short)
+0x5C	DAT_0050d36a	Not in _PROJMoveProc — may be high byte of +0x5B (short)
+0x5E–+0x64	DAT_0050d36c–DAT_0050d372	Not in _PROJMoveProc — check FUN_004c1630

The scattered gap bytes +0x56/+0x58/+0x5A/+0x5C are the high bytes of the confirmed short fields immediately preceding them (+0x55/+0x57/ +0x59/+0x5B) — not independent fields. The block +0x50–+0x54 and isolated range +0x5E–+0x64 have zero xrefs in all of the game executable — no missile code, no BRF code, no generic entity loop touches them. These bytes are either dead/unused fields from an earlier engine version, or are read exclusively by overlay DLLs. Closing this requires scanning the overlay DLL corpus for readers.

Status: open — re-static (#54)

Related

Formats: BRF — family grammar; SH — 3D shapes; SEE — seeker definitions referenced in PROJ_TYPE; NT — NPC vehicles that carry weapons; OT — static objects.