Learn what approach-chart minima, DA/MDA, visibility and RVR mean, and how to choose the correct aircraft category from VREF or Vat.
Approach-chart minima are the lowest authorised altitude or height and minimum visibility or RVR for a particular procedure. Use the aircraft’s certified approach category, normally based on VREF or a defined stall-speed multiple at maximum certificated landing mass; use a higher category when the speed or governing operating rule requires it.
In real-world aviation, the minima box is not one universal limit. You must select the row matching the guidance being flown and the column matching the aircraft category, then comply with any notes, equipment requirements and operational adjustments.
What numbers make up approach chart minima?
Approach minima combine an altitude or height limit with a visibility requirement; meeting one does not cancel the other.
| Chart item | What it means | How it is used |
|---|---|---|
| DA/H | Decision altitude or decision height, normally used for an ILS, LPV or another approach providing approved vertical guidance. | At DA/H, continue only if the required visual references and operating conditions exist; otherwise initiate the missed approach. |
| MDA/H | Minimum descent altitude or height, normally used for a non-precision approach or circling manoeuvre. | Do not descend below it until the required visual conditions exist. If they do not, execute the missed approach no later than the missed-approach point. |
| Visibility | The minimum flight or reported visibility, shown in statute miles or metres according to the charting system. | Apply the value from the selected procedure and category column. |
| RVR | Runway visual range measured for a specific runway area. | Use the published RVR requirement and its stated units rather than treating it as ordinary visibility. |
| HAT or HAA | Height above touchdown or height above airport, often printed in parentheses beside an altitude. | This provides height information; it is usually not the barometric altitude entered as the minimum. |
DA and MDA are generally barometric altitudes referenced to mean sea level, while DH, HAT and HAA are heights above a defined reference. Chart conventions vary, so confirm the units and notation rather than assuming every parenthesised number is an altimeter setting. Our explanation of how the plan, profile and minima sections fit together covers the rest of the chart layout.
The minima remain valid only while the aircraft stays within the procedure design assumptions. Correct altimeter setting, navigation equipment, course tracking, temperature corrections, missed-approach performance and chart notes can all affect which published value is available. Minima also do not guarantee adequate landing distance or make an unsuitable runway acceptable.
Which aircraft approach category should I use?
Use the fixed-wing approach category stated or derived from the aircraft’s approved data, not a category guessed from its present weight, cruise speed or aircraft family.
| Category | Reference approach speed |
|---|---|
| A | Less than 91 knots |
| B | 91 knots or more, but less than 121 knots |
| C | 121 knots or more, but less than 141 knots |
| D | 141 knots or more, but less than 166 knots |
| E | 166 knots or more |
These are the standard A–E speed bands used on many instrument charts. A speed of exactly 121 knots is Category C, not Category B; never round down at a boundary.
Under FAA definitions, the category is based on VREF where specified, or 1.3 times VSO at maximum certificated landing weight. ICAO material uses the related threshold speed Vat at maximum certificated landing mass. The precise derivation can depend on the certification standard, so the aircraft flight manual, operating manual or other approved source takes precedence over a calculation made in the cockpit.
An aircraft does not become a lower category simply because it is light that day. If its approved category is C, selecting Category B minima because the indicated speed happens to be below 121 knots is normally incorrect.
What if I fly the approach faster than my category?
If the planned approach or manoeuvring speed exceeds the upper limit for the aircraft’s normal category, use the applicable higher-category minima as required by the governing rules or operating manual.
This matters especially during circling. Category-specific circling minima provide obstacle protection for an assumed manoeuvring speed and protected-area size. Flying faster can take the aircraft outside that area. Use indicated airspeed for the speed limit; a high groundspeed caused only by wind does not change the category, although it can still make the manoeuvre unsafe or unstable.
Using a higher category is conservative and generally permitted. Using a lower one is not. If the chart supplies no minima for the required category, do not borrow the nearest lower column; the procedure may not be authorised for that aircraft or operation.
How do I select the correct minima line?
Select minima by matching the actual approach guidance, aircraft capability, crew authorisation and category—not merely the procedure name in the chart title.
- Confirm the exact procedure. Check the airport, runway, procedure identifier, amendment and effective information. A similarly named chart may have different minima or missed-approach instructions.
- Identify the guidance actually available. For an RNAV approach, use LPV minima only when the equipment annunciates LPV and the operation is authorised. If it provides only LNAV guidance, use the LNAV line. If an ILS glideslope is unavailable, use localiser-only minima only when the chart publishes them. Our comparison of instrument approach types and their guidance explains these distinctions.
- Read all qualifying notes. Equipment failures, an unavailable local altimeter source, remote-altimeter use, missed-approach climb gradients or temperature restrictions can raise the minima or remove an option entirely.
- Determine the aircraft category. Take it from approved aircraft or operator data, then move to a higher column if the planned speed and applicable rules demand it.
- Intersect the row and column. Read both the altitude or height and the associated visibility or RVR. Do not combine an altitude from one row with visibility from another.
- Apply required adjustments. Account for NOTAMs, cold-temperature corrections, operator additions and inoperative-component rules before setting the minimum reference or briefing the missed approach.
A common error we see is selecting the lowest number displayed instead of the line the avionics can actually support. The flight-management system loading the procedure does not prove that LPV, LNAV/VNAV, ILS or other vertical guidance will be available.
Is aircraft Category C the same as ILS CAT III?
Aircraft approach categories A–E and ILS operating categories I–III are unrelated classification systems.
Aircraft categories describe approach-speed bands and determine the appropriate chart column. ILS CAT I, II and III describe the landing system, aircraft equipment, crew qualification, airport facilities and operational approval needed for progressively lower ILS minima. Our explanation of CAT I, II and III capability requirements covers that separate system.
Wake-turbulence categories and aerodrome rescue categories are separate again. None should be used to select an approach-minima column.
What happens at DA or MDA?
At DA, make the continue-or-go-around decision without planning to level off; at MDA, remain at or above the minimum until descent is permitted or the missed approach is required.
For a DA/H procedure, initiate the missed approach if the required visual reference is absent or the aircraft is not in a position to land safely. For an MDA procedure, plan the descent so the aircraft does not dip below MDA while levelling. If going missed before the published missed-approach point, normally continue along the final approach track until the point where the published turns may begin.
The visibility or RVR figure is a separate operating requirement, and rules governing approach commencement or continuation vary by jurisdiction and operation. A visible patch of ground is not enough; the prescribed runway environment or approach-light references must be available under the applicable rules.
Simulator pilots can reproduce the same discipline by using a practical DA, MDA and RVR workflow for flight simulators, including setting the correct barometric or radio-altimeter reference and briefing the missed approach before descent.