Holdover time

Holdover time: estimated time an application of fluid keeps frost, ice, or snow from adhering to treated surfaces (TC AIM AIR 2.12.2).

• Counted from start of final application.
• Expires when fluid stops being effective.
• Estimate, not guarantee: More than 30 factors affect it, including temperature, wind, aircraft surface temperature, precipitation type and rate (TC AIM AIR 2.12.2; TP 10643, para 24).

Holdover exceeded (TP 10643, paras 83, 85): take-off only after either:

• Pre-takeoff contamination inspection.
• De-icing/anti-icing again.

Take-off not started within 5 minutes of inspection: de-ice/anti-ice again (TP 10643, para 87).

Reading the HOT range (TP 10643, para 29):

1. Precipitation type and rate.
2. Fluid type and manufacturer.
3. Fluid dilution.
4. OAT.
5. Enter matching guideline; find cell with full range of times.

Trap: treating holdover as a fixed clock. It is an estimate; once exceeded, take-off needs inspection or re-treatment.

Practice