DH, MDA, RADIO, and BARO on Airbus: Setting Approach Minimums in the Sim

On final approach, the Airbus PFD shows a cyan minimums bug and the crew must know whether that reference comes from the radio altimeter (height above the ground directly beneath the aircraft) or the barometric altimeter (pressure altitude corrected with QNH). Confusing DH, MDA, RADIO, and BARO is a common sim mistake: the approach looks perfect until you reach the wrong height, miss the decision call, or go around late because the FCU was set to the wrong source. This guide explains each term, how to set them on Airbus FCU and MCDU when you have the airport approach chart, and what to use when you only know whether the runway has ILS or not.

Definitions in plain language

DH — Decision Height is a radio-altimeter height above the runway threshold (or designated height reference on the chart). At DH you must decide: land with required visual references or go around. DH is used on precision approaches with vertical guidance — typically ILS, GLS, or PAR — when the published minima are expressed as a height.

DA — Decision Altitude is the barometric equivalent: the altitude you read on the altimeter when you reach the decision point. Charts often publish both together as DA(H), for example DA 250 ft (DH 237 ft). The small number in brackets is the approximate radio height; the larger value is what you set if using BARO minimums.

MDA — Minimum Descent Altitude is the lowest barometric altitude you may fly during the missed-approach segment of a non-precision approach (VOR, NDB, LOC without glideslope, LNAV, circling, etc.). You level at MDA and may not descend below it unless you have the required runway or approach lights in sight. Unlike DH on an ILS, there is no “slide down to touch” — you stay at MDA until visual or you go around at the missed approach point.

RADIO on the Airbus FCU (or EFIS control panel) tells the flight guidance and PFD to annunciate minimums based on the radio altimeter — you enter a DH value.

BARO tells the system to use the barometric altimeter for the minimums bug — you enter a DA or MDA value, and destination QNH must be correct.

ILS versus non-ILS: which source to pick

Approach type	Typical minimum	FCU source	What you enter
ILS with glideslope (Cat I)	DH or DA(H)	RADIO if chart gives DH; BARO if only DA published	Chart DH (e.g. 200 ft) or DA (e.g. 650 ft)
LOC / LDA (no GS)	MDA	BARO	Chart MDA (e.g. 580 ft)
VOR, NDB, RNAV LNAV	MDA	BARO	Chart MDA at missed approach fix
RNAV LPV (simulated)	DA/DH like precision	RADIO or BARO per chart	As published
Circling	MDA (circling column)	BARO	Higher circling MDA from chart

Rule of thumb in the sim: if the approach has a live glideslope needle captured in GS mode, treat it like precision — use chart DH or DA(H) with RADIO or BARO as the chart header specifies. If you are flying a localizer-only, VOR, or step-down RNAV approach without vertical guidance to the runway, use BARO and the published MDA.

When you have the airport approach chart

1. Open the minima table for your aircraft category (often A or B in light sim jets).
2. Find the row for your approach (e.g. ILS RWY 27L).
3. Note whether the column says DA(H), DH, or MDA.
4. Confirm threshold elevation and any note (e.g. “RA not authorized” — then you must use BARO DA only).
5. Set destination QNH on the FCU before entering BARO minimums — wrong QNH makes DA/MDA meaningless.

Example: chart shows ILS 27L: DA 687 (677) with threshold elevation 650 ft. You may set BARO 687 ft on the FCU or RADIO 677 ft if your operator/sim uses DH. Both should trigger the decision at roughly the same geometric point if QNH is correct.

For MDA 940 on an RNAV approach, set FCU to BARO and enter 940. Brief the missed approach fix and how long you may fly at MDA looking for the runway.

Where to set minimums on Airbus

• FCU — MINIMUMS rotary or pushbutton cycles RADIO / BARO / OFF (wording varies by sim add-on).
• FCU — metric altitude window — enter DH when RADIO selected, DA or MDA when BARO selected.
• MCDU PERF APPR — landing runway, baro, and sometimes DH for autoland and APPR mode logic.
• PFD — cyan bug labeled DA or DH; “minimums” call at decision.
• Radio altimeter — displays height; compare with DH when using RADIO.

In FBW, ToLiss, or Fenix A320 models, enter values in the same order as your checklist: QNH set → minimums source → value → cross-check standby altimeter if BARO.

When you do not have the chart (general sim briefing)

NG ROUTE gives you METAR, runway, and route — not approach plate minima. Use conservative training defaults:

• ILS to a runway with working GS in the sim: RADIO DH 200 ft (Cat I training default) or BARO DA ≈ threshold elevation + 200 ft if you know field elevation from the sim map.
• LOC or visual approach with localizer only: BARO MDA 500–600 ft above airport elevation for flat terrain; add margin for mountains.
• VOR/NDB/non-precision: BARO MDA at least 400 ft above runway elevation until you practice a specific plate.
• Circling: never use ILS DH; use a higher BARO MDA (often +300–500 ft above straight-in minima in real charts — in the sim, brief at least 1,000 ft AGL equivalent unless you have the circling table).

These defaults are for simulation habit-building, not operational minima. When you download a chart pack (Navigraph, etc.), replace defaults with published numbers.

Decision call and go-around

At minimums (DH/DA/MDA per SOP):

• If required visual references are in sight — continue to land.
• If not — TOGA immediately; do not descend below DH on ILS; do not leave MDA on non-precision without visuals.

On Airbus, the call is often “MINIMUMS — runway in sight” or “MINIMUMS — go-around.” Autoland must disconnect by DH unless certified otherwise. In the sim, practice the call ten times until RADIO versus BARO no longer requires conscious thought.

Common sim errors

• BARO DA entered while FCU still shows STD from cruise
• MDA entered with RADIO selected — bug behaves incorrectly
• ILS DH set to 200 ft on a runway whose chart DA is 650 ft — you go around miles early or land without a decision
• Using ILS minima on a LOC approach — LOC MDA is usually much higher
• Forgetting circling requires a separate, higher MDA

Practice with NG ROUTE

Plan an arrival with NG ROUTE, read destination METAR QNH, and fly two approaches to the same runway: one full ILS with RADIO DH, one LOC-only or vector-to-final with BARO MDA. Note how the cyan bug moves relative to the radio altimeter and baro altimeter. Goal: correct source and value before every final, whether or not you have the paper chart in the sim.

Minimums and approach authorization vary by state, operator, and aircraft certification. Real-world flight uses only approved charts and SOPs. Simulation training only.