G-Groups

Updated at: 2026-01-31 10:59
G-Groups are a commonly taught set of aviation Q-codes and altimeter settings used to request or convey direction information (QDM, QDR) and pressure references for altitude/height indication (QFE, QNH).

Term definition

In aviation radio navigation and pressure setting context, “G-Groups” is an informal training label used to group together several high-utility Q-codes and related settings that student pilots frequently encounter.
The specific items in this group are: QDM, QDR, QFE, and QNH. QDM and QDR relate to bearings to/from a station. QFE and QNH relate to pressure settings used to reference height or altitude.

Purpose

The purpose of teaching these items together is practical: they are short, standardized, and reduce ambiguity when pilots and air traffic services discuss navigation guidance and pressure references.
In basic terms: QDM and QDR help you point the aircraft correctly relative to a navigation aid or direction-finding (DF) service, while QFE and QNH ensure that altitude or height indications are referenced to the intended datum.

Use in aviation

QDM

QDM is the magnetic bearing to a station (or to the aircraft from the station, depending on the service), commonly taught as “the magnetic heading to steer to reach the station” when provided by a direction-finding service.
Operationally, QDM is used when you want a clear, steerable direction to fly toward a facility or position. In training, it is often associated with “homing” guidance (fly the given heading) rather than tracking a course with wind correction.

QDR

QDR is the magnetic bearing from a station to the aircraft (a “bearing of the aircraft from the station”). It is commonly treated as the reciprocal concept to QDM.
Operationally, QDR is useful for position reporting and situational awareness: if you know your distance (for example from DME) and the QDR, you can describe your position relative to the station as a radial and distance.

QFE

QFE is the pressure setting that makes an altimeter read zero when the aircraft is on the reference datum, typically the aerodrome elevation (field elevation). The resulting indication in flight is a height above the aerodrome (often called “height” rather than “altitude”).
QFE is used in some states and operations to reference circuit (traffic pattern) height and approach minima as height above the aerodrome. Where used, it can simplify “height above field” thinking during local operations.

QNH

QNH is the pressure setting that makes an altimeter indicate the aircraft’s altitude above mean sea level (MSL) when operating near the aerodrome, assuming standard atmosphere corrections used in altimeter calibration conventions.
QNH is widely used for en route and terminal operations because it aligns the altimeter indication with charted altitudes, terrain elevations, and obstacle elevations referenced to mean sea level.
Altimeter subscale showing pressure setting window (QNH/QFE concept)

Operational considerations

Bearings (QDM/QDR): what can go wrong

When using QDM and QDR, the main operational risks are misunderstanding the reference and applying the value incorrectly.
  1. Confirm magnetic vs true. In most operational radio use, QDM/QDR are magnetic, but local procedures may specify otherwise.
  2. Confirm “to” vs “from”. QDM is used as “to the station,” QDR as “from the station.” Confusing them produces an approximate 180° error.
  3. Do not confuse “heading to steer” with “track to maintain”. A DF-provided steer may not account for wind; maintaining a desired track generally requires wind correction.
  4. State your needs clearly. If you are requesting help, specify whether you need a bearing to a station, a bearing from a station, or a general position fix.

Pressure settings (QFE/QNH): what can go wrong

Altimeter setting errors directly affect vertical separation from terrain and obstacles. The key operational consideration is using the correct reference for the phase of flight and the local rules.
  1. Know what your altimeter is indicating. On QNH the indication is altitude above mean sea level. On QFE the indication is height above the aerodrome reference datum.
  2. Expect different minima references. Published procedure minima and traffic pattern altitudes may be given as altitude (MSL) or height (above threshold/aerodrome). Match the pressure setting to the reference used.
  3. Transition awareness. When climbing to flight levels, standard pressure (often 1013.25 hPa / 29.92 inHg) is used above the transition altitude; descending uses QNH below the transition level. QFE, if used, is typically a local aerodrome operation choice rather than an en route reference.
  4. Cross-check with known elevations. After setting QNH on the ground, the indicated altitude should be close to the aerodrome elevation (within instrument and pressure tolerance). After setting QFE, it should read near zero on the reference datum.

Examples

QDM example (direction-finding assistance)

A pilot uncertain of position requests a QDM from a DF-capable unit; the unit provides a magnetic heading to steer toward the station, and the pilot uses it to regain situational awareness and proceed toward known airspace.

QDR example (position description)

A pilot reports position as a bearing and distance from a VOR: the QDR corresponds to the radial the aircraft is on (bearing from the station), and the distance comes from DME or another source.

QFE example (local circuit height)

At an aerodrome where QFE is used for local operations, a pilot sets QFE before entering the traffic pattern so that the downwind height indication corresponds directly to height above the aerodrome.

QNH example (terrain-referenced operations)

A pilot sets QNH for departure and en route flight so the altimeter matches charted altitudes and terrain elevations referenced to mean sea level, supporting obstacle clearance and ATC altitude assignments.