★ PTS mapping: This lesson aligns to FAA-S-8081-20A (Nov 2023), Area of Operation I — Preflight Preparation. It is a Practical Test Standard, so items are Tasks and elements (no ACS K/R/S codes); read the exact Task lettering and tolerances from the current published PTS.
Reading the charts an ATP lives by — hover capability, the H/V curve, and OEI performance classes.
The two hover-performance limits are Hover In Ground Effect (HIGE) and Hover Out of Ground Effect (HOGE). HIGE requires less power because the ground reduces induced flow (Lesson 02); HOGE requires more, so the HOGE ceiling is always lower than the HIGE ceiling at a given weight. The performance charts give a maximum weight or maximum pressure altitude for hover at a given temperature. Read them honestly: a helicopter that can hover IGE on the pad may not be able to hover OGE over an obstacle, a pinnacle, or after climbing into thinner, hotter air. Always determine the HOGE capability for any operation that requires an OGE hover (confined area, external load, pinnacle).
The height-velocity (H/V) diagram — the "dead-man's curve" — maps the combinations of height above the surface and airspeed from which a safe autorotation may not be achievable if power is lost. There are typically two avoid areas: a low-airspeed/high-height region (too high to land before the rotor decays, too slow to convert to autorotative airspeed) and a low-height/high-speed region (too fast and low to flare and stop). The chart is weight- and density-altitude-sensitive — the avoid areas enlarge at higher weight and density altitude. Plan takeoff and approach profiles to transit the curve as quickly as practical and to spend minimum time in the avoid regions.
Density altitude is pressure altitude corrected for nonstandard temperature; high DA = thin air = less rotor thrust, less engine power, and less tail-rotor authority all at once. The chart-driven limits combine these into weight-altitude-temperature (WAT) limits: the maximum gross weight at which the required performance (e.g., a given climb gradient or hover capability) is guaranteed for the ambient altitude and temperature. The ATP routine is: compute DA, enter the performance charts at the actual pressure altitude and temperature, read the limiting weight or available power, and confirm a margin remains for the planned maneuver. Never assume sea-level numbers on a hot day at altitude.
| Input rises → | Effect on performance |
|---|---|
| Pressure altitude ↑ | Less air density → less power & thrust; lower hover ceiling; H/V avoid areas grow |
| Temperature ↑ | Higher density altitude → same degradation as altitude |
| Gross weight ↑ | More power required to hover/climb; reduced margin; larger H/V avoid areas |
| Humidity ↑ | Slightly reduced power (notably for piston engines) |
For multi-engine helicopters, one-engine-inoperative (OEI) capability is described by performance classes: PC1 — capable of continuing the takeoff/flight after an engine failure at the critical point and landing within the cleared area or continuing (no forced landing if a failure occurs after the takeoff decision point); PC2 — generally continued flight assured but a forced landing may be required during a defined early phase; PC3 — a forced landing is required if an engine fails at any point (typical of single-engine helicopters). Related are Category A (engine isolation, OEI takeoff/landing profiles with guaranteed performance, used for Part 29 transport-category and many Part 135 ops) and Category B (no guaranteed OEI capability — a forced landing may be unavoidable). The takeoff/landing decision points (TDP/LDP) and the OEI procedures come from the type's RFM Category-A supplement.
★ Note on OEI framing: Performance-class (PC1/PC2/PC3) and Category A/B terminology derives from ICAO/transport-category (FAA Part 29) concepts. Cover it to the depth the current FAA-S-8081-20A and your actual test aircraft's RFM require; confirm whether Category A/B is examined for the specific test aircraft, and use that aircraft's RFM Category-A supplement for any OEI specifics (no invented numbers).
Curated reference clip — “HV Diagram Episode 2” · Bruce Webb (YouTube), verified via oEmbed. Embedded with the creator's player; we don't host or alter it.
✈️ Your test aircraft: the R-44 fill-in values cover its single-engine, piston, VFR figures — effectively PC3 / Category B, with no OEI performance. The PC1/PC2 and Category A material applies only to a multi-engine ATP test aircraft. ATP-H practical tests are normally flown in a turbine and/or multi-engine, IFR-capable helicopter, so use that aircraft's RFM charts (hover ceilings, H/V, WAT, OEI/Cat-A data) for items marked aircraft-specific.