Discrepancy Lifecycle

A discrepancy is the ERP's word for a snag, a write-up, a defect — anything found wrong with the aircraft. It's the fault-lifecycle unit: every physical problem becomes one discrepancy record that's either closed or deferred.

The state machine

                    ┌────────────────┐
   snag             │                │
   reported  ──────▶│   UNRESOLVED   │◀──── revision / extension
                    │                │
                    └────┬───────┬───┘
                         │       │
               resolution│       │ deferral
                         ▼       ▼
                   ┌─────────┐ ┌──────────┐
                   │  RESOL  │ │ DEFERRED │──▶ expiry ──▶ back to UNRESOLVED
                   │  (done) │ │ (fly-on) │
                   └─────────┘ └────┬─────┘
                                    │
                               final resolution
                                    ▼
                              ┌─────────┐
                              │  CLOSED │
                              └─────────┘

The status column in DP_DISCP_DISCREPANCY_DTL that drives this is DISCP_RECORD_STATUS (UNRES, RESOL, CLOSED), plus DISCP_PROCESS_STATUS (NONE, DEFERRED, UNDER_REVIEW, etc.).

The two paths a discrepancy can take

Path A — Resolved

The quick-and-clean path: a defect is found, a fix is applied, someone signs off, the discrepancy is closed. Records in DP_RESLHST_DISC_RESOL_HIST capture each action taken — diagnosis, repair, test, final sign-off. Each action carries an employee, a date, and remedial-action text.

In the database, for hero aircraft 1132: 4,040 resolution-history rows across its 1,919 discrepancies — averaging 2.1 actions per discrepancy before closure.

Path B — Deferred

If the defect can be safely flown with — according to the operator's Minimum Equipment List — it's deferred rather than fixed now. This creates:

A DeferralRecord in DP_DPDEF_DISC_DEFERRAL_DTL, keyed by DPDEF_MAINT_REPORT_NO (the maintenance report number — a human-friendly doc id like MREP-000140-2019)
A deferral limit expressed in one of:
- Calendar time (e.g. "30 days")
- Flight hours (e.g. "100 FH")
- Flight cycles (e.g. "50 FC")
A MEL reference pointing at the specific MEL item that authorises the deferral

Every subsequent extension, revision, or status change on the deferral is captured in DP_DEFHST_DISC_DEFERRAL_HST — the deferral history. The dataset has 2,196 deferral-history rows across seed aircraft.

When a deferral reaches its limit, it automatically reverts to UNRESOLVED and the aircraft can't legally fly until rectified.

Discrepancy classifications

In DP_DISCP_DISCREPANCY_DTL, three columns classify a discrepancy:

DISCP_TYPE — the origin/nature. Common values include MIREP (maintenance report raised by maintenance), MLGEN, DPGEN. See Discrepancy Types and Categories for the full list and rules.
DISCP_CATEGORY — a sub-classification tied to ATA chapter or severity. QC26, ATTRI2, FF77, etc.
DISCP_APPLICABILITY — AIRC (aircraft), COMP (component), ENGN (engine), indicating what the defect is on.

Where discrepancies enter the system

Discrepancies can enter three ways:

Pilot write-up during/after a flight. Captured during the AME package turn. Often starts life as a "snag" row in FLOG_TLGSNG_TECH_LOG_SNAG_DTL before being elevated to a formal discrepancy.
Maintenance finding during a check. Inspector finds something during a scheduled task → raises a discrepancy.
Shop-side finding. During component repair, the shop finds an additional defect — this becomes a SWODiscrepancy against the SWO, not against the aircraft.

The deferral fence

A common operational question: "can I defer this discrepancy or must I fix it now?" The MEL rules encoded at MEL Deferral Rules answer this. The gist:

Category A — must fix before next flight.
Category B — can defer up to 3 days.
Category C — up to 10 days.
Category D — up to 120 days.

Every deferral must reference a specific MEL item. The MEL itself is represented in CFG_CFGMEL_MDL_CONFIG_MEL and CFG_CFGMELC_MEL_CATEGORY.

Usage-parameter tracking

For deferrals limited by usage (flight hours / cycles), the ERP tracks consumption against them in:

DP_MRUSG_USAGE_DEF_PARAM_VAL — the per-deferral usage baseline
DP_PRMSCH_PARAM_SCHEDULE_DTL — scheduled review points
DP_DPPRM_PARAMETER_DETAILS — parameter readings captured when opened

When the aircraft burns more hours/cycles, the system automatically advances the deferral's "used" counter.

The end-of-life of a discrepancy

A discrepancy is closed when either:

Path A completed — fix applied, signed off, status = RESOL → CLOSED.
Path B completed — deferral resolved, the underlying fix done later, signed off, status = CLOSED.

Every action along the way is recorded in the resolution history, creating a full audit trail. Regulators can ask years later why a deferral was granted, what extensions were applied, who signed off the final fix, and what part was used — and the ERP has to produce the answer.