Within limit
Caution — in temporary-tolerance band (AMM Table 7/8)
Exceeded — beyond limit / > NSA 307110 class 9
No data
RESAMPLE sample older than 3 years (program interval)
Permitted limits — AMM 12-32-29-281-801-A (in-service hydraulic fluid)
Particle counts per NSA 307110: Class 8 = intermediate caution level, Class 9 = max in-service limit (per 100 mL). Caution band = between Class 8 and Class 9. Note: AMM 12-32-29-281-801-A also lists a Class 7 limit, but that applies to fresh/topping-up fluid and ground-cart reservoirs (initial condition) — not to in-service aircraft samples — so it is shown for reference only and does not drive this dashboard's status. TAN caution band 1.0–2.5 mg KOH/g (AMM Table 8, graded fluid-replacement); >2.5 requires immediate action. Density & conductivity out-of-range carry a 600 FH temporary authorization (shown as caution).
Temporary authorizations & grace periods — AMM 12-32-29-281-801-A
Table 7 — Chemical contamination (tolerance & permitted period)
| Property | In-service limit | Tolerance | Permitted period |
|---|
| Acid number (TAN) | max 1 mg KOH/g | 1 – 3.5 mg KOH/g | see Table 8 → |
| Density (at 23 ±3 °C) | 970 – 1066 kg/m³ | not applicable | 600 FH |
| Water content | 0.5% recommended
max 0.8% | 0.8% – 1% | 600 FH |
| 1% – 1.5% | 7 operational days |
| Viscosity (at 38 °C) | 6 – 12.5 cSt | 5.5 – 6 cSt | 10 op. days or 150 FH |
| Chlorine content | max 200 ppm | 200 – 300 ppm | 10 op. days or 150 FH |
| Electrical conductivity | min 0.30 µS/cm | below 0.30 µS/cm | 600 FH |
Corrective action starts immediately on finding contamination; the permitted period is the max operating time before the applicable AMM task is done. Water/chlorine → purifier or fluid replacement; density/viscosity/conductivity → fluid replacement; then new sample within 1–5 flight cycles.
Table 8 — Acid contamination (TAN grace periods)
| Acidity level | Grace period | Procedure |
|---|
| TAN ≤ 1.0 | n/a | No action — next MPD check |
| 1.0 < TAN ≤ 1.2 | 30 days | Replace reservoir fluid 2× |
| 1.2 < TAN ≤ 1.5 | 30 days | Replace reservoir fluid 3× |
| 1.5 < TAN ≤ 1.8 | 14 days | Replace reservoir fluid 4× |
| 1.8 < TAN ≤ 2.2 | 14 days | Replace reservoir fluid 5× |
| 2.2 < TAN ≤ 2.5 | 14 days | Replace reservoir fluid 6× |
| 2.5 < TAN ≤ 3.5 | 3 flight cycles | Replace hydraulic-system fluid (no grace if contamination in >1 system) |
After reservoir replacements: operate flight controls or ≥1 flight cycle between each; new sample after ≥1 flight cycle, within 1 week; result within 30 days. Particles > Class 9: stop hydraulic tests, do a recovery procedure (AMM 12-32-29-281-802); temporary release max 2 days / 36 FH if only one system affected and flight-control tests done; release max 30 days while waiting for lab results.