DH, MDA, RADIO, and BARO on Boeing: Approach Minimums for Simulator Pilots

Boeing flight decks annunciate approach minimums on the PFD as a cyan altitude bug or “minimums” marker. Whether that reference comes from the radio altimeter or the barometric altimeter is your choice on the MCP — and it must match what the approach chart publishes. Mixing up DH, MDA, RADIO, and BARO produces the classic sim failure: a perfect NG ROUTE arrival until you silently pass decision height without a call, or go around at 800 ft because the MCP was set to RADIO while the approach was a non-precision BARO MDA. This article defines each term, shows where to set values on Boeing MCP and CDU, and gives chart-based versus general rules for ILS and non-ILS approaches.

What each term means

DH — Decision Height is height above the runway threshold (or chart datum) measured by the radio altimeter. On a precision approach with vertical guidance, reaching DH is the decision point: land with required visuals or execute missed approach immediately.

DA — Decision Altitude is the barometric altitude read on the altimeter at that same decision point. Approach plates often show DA(H) together — e.g. DA 452 (440) means 452 ft on the altimeter with QNH set, approximately 440 ft radio height.

MDA — Minimum Descent Altitude is the lowest barometric altitude permitted during the final segment of a non-precision approach until you have visual references. You fly level at MDA to the missed approach point; you do not “follow a glide path” to the runway unless you have visual segment cues. LOC without glideslope, VOR, NDB, and many RNAV LNAV procedures use MDA.

RADIO on the MCP minimums selector uses the radio altimeter as the reference — enter DH.

BARO uses the barometric altimeter — enter DA (precision) or MDA (non-precision).

ILS versus non-ILS: quick selection guide

Approach	Published minimum	MCP setting	Value to enter
ILS with GS captured	DA(H) or DH	RADIO for DH; BARO for DA	From chart minima line
LOC / LDA (no GS)	MDA	BARO	Chart MDA
VOR / NDB / TACAN	MDA	BARO	Chart MDA at MAP
RNAV (LNAV, no LPV)	MDA	BARO	Chart MDA
RNAV LPV / ILS-like	DA/DH	Per chart notes	DA(H) as published
Circling	MDA (circling)	BARO	Circling column only

Simulator shortcut: glideslope needle alive and captured on an ILS → precision logic, DH or DA from chart. No glideslope, step-down fixes, or lateral-only guidance → BARO and MDA. When in doubt, BARO MDA is safer than inventing a DH.

Using real approach charts

1. Find the inbound minimums block for your approach name and aircraft category.
2. Read the landing minima row — not always the same as the approach minimums at the FAF.
3. Check notes: “RADAR REQUIRED”, “DME REQUIRED”, or “RA NA” (radio altimeter not authorized — use BARO DA only).
4. Set destination QNH on both MCP BARO knobs before relying on BARO DA or MDA.
5. Enter the value on MCP; cross-check on CDU APPROACH REF or LANDING REF page if your add-on duplicates it.

Example: ILS 08R DA 603 (593) with threshold 433 ft MSL. With QNH set, BARO 603 should match decision; RADIO 593 ft DH should match radio altimeter at decision. If METAR QNH is wrong, BARO DA will lie; RADIO DH still measures height above ground — another reason some crews prefer RADIO on ILS when authorized.

Where to set minimums on Boeing

• MCP — MINIMUMS switch: RADIO / BARO (737 NG, 777, 787 layouts similar in concept).
• MCP — altitude window — DH when RADIO; DA or MDA when BARO.
• PFD — decision altitude/height bug; compare with radio altimeter display on approach.
• CDU APPROACH REF (PMDG/iFly etc.) — runway length, flap, wind, and sometimes DA for VNAV approach logic.
• EFIS control panel on some fleets — duplicates minimums source selection.

Both sides should agree: captain and first officer MCP minimums and bugs matched before final approach fix.

No chart available: practical sim defaults

When NG ROUTE gives you runway and METAR but no plate:

• ILS with GS in sim: MCP RADIO, DH 200 ft (common Cat I training value), or BARO DA ≈ runway elevation + 200 ft from airport info.
• Visual or LOC-only final: MCP BARO, MDA 500–600 ft above field elevation in flat areas.
• Non-precision generic: BARO MDA at least 400 ft above runway until you use real minima.
• Circling: use BARO MDA well above straight-in values; never use ILS DH for a circling maneuver.

Replace these defaults when you load Navigraph or other chart data into the sim. They exist so you still brief a decision point every approach.

VNAV and BARO minimums

On 737/777/787 with VNAV PATH on a STAR or RNAV approach, baro errors affect fix crossing altitudes as well as MDA. Wrong QNH can bust step-downs before you reach final. If VNAV guides you to an MDA, the MCP BARO MDA bug should match the chart; at MDA, transition to level flight and look for visuals — VNAV does not give ILS-style slide path to touchdown on a plain LNAV approach.

On ILS with glideslope, flight director and A/T track the beam; minimums still come from MCP RADIO/BARO setting, not from the glideslope angle alone.

Decision procedure

At the bug:

• “Minimums — continuing” if required runway environment in sight.
• “Minimums — go-around” if not — press TO/GA, follow missed approach.

Do not descend below DH on precision approaches without visuals. Do not descend below MDA on non-precision without visuals. In PMDG and similar models, pre-brief whether your session uses RADIO or BARO so the PM call matches the bug.

Frequent mistakes in Boeing sims

• Leaving minimums at landing airport elevation from a previous leg
• RADIO DH on a VOR approach that publishes only MDA
• BARO DA with STD still set on MCP from cruise
• Using straight-in ILS minima while flying a circling approach
• MCP bug at 200 ft DH while chart DA is 650 ft — decision call makes no sense

NG ROUTE training pairing

Fly the same NG ROUTE-planned arrival twice: once ILS with MCP RADIO DH, once with vectors to a non-precision final using BARO MDA. Read QNH from the NG ROUTE METAR card each time. The goal is to set source and value before the final approach fix on every leg, chart or no chart.

Approach minimums and operating minima are regulatory and operator-specific. This article supports flight simulation only — not real-world dispatch or instrument procedure design.