The CRP-5 (Pooley's) and E6B (FAA standard; legacy AN-5835) are mechanical flight computers with two functional sides — the standard for PPL theory and skill-test calculations in Europe.
Side 1: Slide rule
Calculations via two rotating discs (logarithmically scaled):
| Calculation | Use |
|---|---|
| Multiplication / division | Any numbers |
| Time-speed-distance (TSD) | Leg time, distance or GS from two of the three |
| Fuel | Flow × time = quantity, or quantity / flow = endurance |
| TAS from CAS and altitude/temperature | Airspeed window |
| Density altitude correction | With pressure altitude and OAT |
| Unit conversion | Nautical ↔ statute miles, litres ↔ gallons, kg ↔ lb |
Side 2: Wind side
| Calculation | Use |
|---|---|
| Heading from track, TAS, wind | "Correction" |
| Track from heading, TAS, wind | Trip-plan validation |
| Wind from heading, TAS, track, GS | In-flight wind determination |
Skill-test approval
The mechanical CRP-5 / E6B is permitted in EU skill tests. Battery-powered versions (e.g. ASA E6B-Electronic) and smartphone apps (e.g. Sporty's E6B) are accepted by most ATOs/examiners — confirm in advance.
Use tips
- Always carry one (mechanical + digital backup) — batteries can fail.
- Before the skill test, be fluent with your own model: practise the calculations.
- For the NAA theory exam (in Germany: LBA TK exam): only passive aids are allowed; bring your own computer.