Learning objective: You decide from the subscale whether you are flying altitude AMSL (QNH), height above the field (QFE) or flight level (QNE / 1013.25 hPa) — and you know a higher QNH raises the indication.
60 seconds: You are flying the approach. Tower gives a new QNH, ten hectopascals higher than yours. You wind the Kollsman subscale. The needles climb. Remember: higher QNH = higher indication. Rule of thumb (teaching, not AFM): 1 hPa ≈ 28 ft, so +10 hPa ≈ +280 ft.
The altimeter (Höhenmesser) is an aneroid barometer on the static port. The evacuated capsule expands as outside pressure falls. Glass does the same with a pressure sensor driving the PFD tape. Neither is GPS altitude.
What the needles mean depends only on the subscale:
| Setting | What you read |
|---|---|
| QNH | Altitude AMSL — height above sea level |
| QFE | Height above the aerodrome; 0 ft AGL on touchdown |
| QNE (1013.25 hPa) | Pressure altitude → flight level |
“QFE is true altitude AMSL.” That is wrong. People mix height and altitude. QFE is field datum. Temperature and non-ISA density mean indicated pressure altitude is not true altitude — that is navigation, not “the needles never lie”.
Blocked static: the altimeter freezes at the blockage value. Alternate static per the AFM. No invented transition altitudes as a universal fact — transition altitude lives on the chart / AIP / procedure.
Set QNH before flight from ATIS/tower, update en-route. How often is teaching, not an AFM minute interval.
Exam knowledge
- Altimeter = static + aneroid (or electronic pressure sensor).
- QNH = AMSL. QFE = 0 ft AGL on touchdown. QNE 1013.25 hPa = FL.
- Higher QNH → higher indication.
- 1 hPa ≈ 28 ft is teaching, not AFM.
- Static blocked → ALT frozen. Alternate static = AFM.
- No true altitude without a temperature correction.
Source: typical EASA PPL 020 / 010 Q-code teaching. 28 ft/hPa is school teaching. Transition and setting procedures from chart/AIP/AFM.
Check yourself
1. With the subscale on QFE, the altimeter shows?
- A) Flight level on 1013.25 hPa
- B) Height above the aerodrome; 0 ft AGL on touchdown
- C) True altitude AMSL, temperature-corrected
- D) Always AMSL, whatever the subscale
2. Setting a higher QNH — what happens (lesson rule of thumb)?
- A) Indication falls; 1 hPa ≈ 10 ft
- B) Indication unchanged
- C) It switches to flight level above 1013 hPa
- D) Indication rises; +10 hPa ≈ +280 ft (1 hPa ≈ 28 ft as taught)
- B — QFE is 0 ft AGL on touchdown. AMSL is QNH; FL is QNE.
- D — higher QNH, higher indication. 28 ft/hPa is the lesson rule, not an AFM limit.