API v1.3.6

Landing Performance

Calculate landing performance data including approach speeds, required distances, maximum landing weight, and braking requirements.

Calculation Modes

The API supports two calculation modes depending on your use case. The mode is determined by the landingMode parameter.

Dispatch Calculation

Calculate the Maximum Landing Weight (MLW) — the maximum allowable weight for the given conditions.

Use case: Dispatch planning, fuel planning, alternate selection.

How: Set landingMode to "dispatch" (default)

Returns: MLW, limiting factors, required distances

Inflight Calculation

Calculate complete landing data for a specific landing weight.

Use case: Approach preparation, EFB data, pilot briefing.

How: Set landingMode to "inflight" and provide landingWeight

Returns: VREF, VAPP, landing distances, autobrake settings

Request

POST /api

Full Request Structure

JSON

{
  "query": "performance",
  "apiVersion": "1.3.6",
  "data": {
    "requestType": "LANDING",
    "landingMode": "dispatch",
    "units": {
      "weight": "kg",
      "wind": "kt",
      "altitude": "feet",
      "distance": "feet",
      "depth": "mm",
      "pressure": "hpa"
    },
    "aircraft": {
      "file": "737-800W_CFM56-7B26.json",
      "userRegistration": null,
      "virtualAirline": null
    },
    "airport": "EBBR",
    "runway": "25R",
    "weather": {
      "windDirection": 250,
      "windSpeed": 10,
      "headwind": null,
      "temperature": 15,
      "qnh": 1013
    },
    "runwayCondition": {
      "state": "DRY",
      "depth": 0
    },
    "configuration": {
      "flap": "OPTIMUM",
      "autobrake": null,
      "antiIce": "OFF",
      "reverser": "ALL",
      "speedbrake": "AUTO",
      "vrefAdditive": 0,
      "nonNormalCondition": null,
      "approachType": null,
      "landingTechnique": null,
      "missedApproachClimbGradient": 2.5
    },
    "weight": {
      "landingWeight": null,
      "cg": null,
      "cgPosition": null
    },
    "inopItems": {
      "mel": [],
      "cdl": []
    },
    "notam": null
  }
}

Units

The API uses standard units by default. You can override any unit by specifying it in the units object. Response values will be returned in the same units.

Standard Units (Default)

Parameter	Standard Unit
`weight`	kg
`wind`	kt (knots)
`altitude`	feet
`distance`	feet
`depth`	mm (millimeters)
`pressure`	hpa (hectopascal)

Custom Units

Override defaults by including the units object:

Parameter	Allowed Values
`weight`	`kg`, `lb`
`wind`	`kt`, `ms` (meters per second)
`altitude`	`feet`, `meter`
`distance`	`feet`, `meter`
`depth`	`mm`, `inches`
`pressure`	`hpa`, `inhg` (inch of mercury)

Parameters

Data Source Requirement

Configuration values (flap, autobrake, antiIce, runwayCondition.state, etc.) must match the options provided in the aircraft's formData from the Aircraft API. Custom values not present in formData will be rejected.

landingMode

Parameter	Type	Default	Description
`landingMode`	string	"dispatch"	`"dispatch"` — Maximum landing weight calculation. Distances and gradients are calculated differently than inflight. `"inflight"` — Actual landing distances and speeds at a given weight. Requires `landingWeight`.

aircraft Required

Parameter	Type	Description
`file`	string	Required. Aircraft profile filename from Aircraft API
`userRegistration`	string\|null	Custom aircraft registration for personalized profiles
`virtualAirline`	string\|null	Virtual airline identifier for VA-specific aircraft

airport & runway Required

Parameter	Type	Description
`airport`	string	Required. ICAO airport code (e.g., `"EBBR"`)
`runway`	string	Required. Runway identification from the Airports API (e.g., `"25R"`, `"25RI3"` intersection, `"25RN1"` notam)

weather

Parameter	Type	Default	Description
`windDirection`	integer	0	Wind direction in degrees magnetic (0-360)
`windSpeed`	integer	0	Wind speed in knots (or unit specified)
`headwind`	integer\|null	null	Direct headwind component. Negative = tailwind. Overrides direction/speed if provided.
`temperature`	number	15	Outside Air Temperature (OAT) in °C
`qnh`	number	1013	Altimeter setting. Default unit is hPa; set `pressure` unit to `"inhg"` to provide and receive values in inches of mercury (e.g., `29.92`).

runway_condition

Parameter	Type	Default	Description
`state`	string	"DRY"	Runway condition `value` from the aircraft profile `conditionDispatch` or `conditionEnroute` options.
`depth`	number	0	Contamination depth in mm (or unit specified). Only used when state indicates contamination.

configuration

Parameter	Type	Default	Description
`flap`	string	"OPTIMUM"	`OPTIMUM` (Airbus only) or a specific value from the aircraft profile. Some flap settings include autoland info (e.g., `"30\|AUTOLAND"`).
`autobrake`	string\|null	null	Dispatch: ignored (always OFF). Inflight: `"ALL"` to iterate all settings (Boeing only), or a specific `value` from the aircraft profile `autobrake` options.
`antiIce`	string	"OFF"	`value` from the aircraft profile `ai` options.
`reverser`	string	"ALL"	`value` from the aircraft profile `reversers` options.
`speedbrake`	string	"AUTO"	`value` from the aircraft profile `groundSpoilers` options.
`vrefAdditive`	integer	0	Dispatch: ignored. Inflight: Speed additive above Vref (0–20 kt). Automatically capped. Minimum 5 kt for autoland approaches.
`nonNormalCondition`	string\|null	null	Dispatch: ignored. Inflight: Non-Normal Checklist item from the aircraft profile `nonNormalConf` options. Requires NNC subscription.
`approachType`	string\|null	null	Airbus only. `CAT_II`, `AUTOLAND`, `MANUAL_LDG`
`missedApproachClimbGradient`	number	2.5	Required Missed Approach Climb Gradient (MACG) in percent. Airbus dispatch: sent directly to the performance calculator as a climb gradient constraint (`appClbGrd`). The calculator enforces this limit when computing the regulated landing weight. Boeing dispatch: not sent as a constraint; the calculator returns the actual gradient and the API compares it against this value — an advisory caution is raised if the gradient falls below the required minimum. Inflight: used for the same advisory comparison as Boeing dispatch (no constraint enforced).
`landingTechnique`	string\|null	null	Airbus only. `AUTO_LDG` or `MANUAL`

weight

Parameter	Type	Default	Description
`landingWeight`	number\|null	null	Landing weight in the selected unit. Required when `landingMode` is `"inflight"`. Ignored in dispatch mode.
`cg`	number\|null	null	Center of gravity as % MAC (Boeing)
`cgPosition`	string\|null	null	CG position from the aircraft profile (e.g. `STANDARD`, `FWD`, `AFT`)

notam

NOTAM (Notice to Airmen) runway restrictions. When provided, the landing distances are adjusted to reflect temporary runway modifications. Requires NOTAM in subscription. Pass null or omit when not applicable.

The shortenStart and shortenEnd values reduce the Landing Distance Available (LDA) accordingly.

All distance values use the distance unit from the units section (default: feet).

Parameter	Type	Default	Description
`shortenStart`	number	0	Runway closure distance from the start threshold. Must be ≥ 0.
`shortenEnd`	number	0	Runway closure distance from the end threshold. Must be ≥ 0.

inopItems

Parameter	Type	Default	Description
`mel`	array	[]	Minimum Equipment List items (codes from the aircraft profile)
`cdl`	array	[]	Configuration Deviation List items (codes from the aircraft profile)

Response

Common Response Fields

Field	Type	Description
`calculationPossible`	boolean	`true` if calculation succeeded
`subCalculation`	string	`"LANDING_DISPATCH"` or `"LANDING_INFLIGHT"`
`units`	object	Unit labels for all returned values (weight, distance, altitude, wind, depth)
`caution`	array	Caution and advisory messages (icing, MACG, overweight, brake cooling, etc.)
`error`	string\|array	Error messages when `calculationPossible` is `false`

Performance — General Fields

Returned in both dispatch and inflight modes.

Field	Type	Description
`flap`	string	Selected flap setting
`lda`	integer	Landing Distance Available (may be reduced by NOTAM)
`isNOTAM`	boolean	`true` if a NOTAM runway reduction was applied
`runwayIdent`	string	Active runway designator

Performance — Weight & Time Fields

Field	Type	Description
`landingWeight`	integer	Dispatch: Calculated max landing weight Inflight: User-provided landing weight
`perfLimitedLandingWeight`	integer	Most restrictive performance-limited landing weight, computed as `min(appClimbLimit, fieldLimit, ldgClimbLimit, tireSpeed)`. Excludes structural (MSLW) and quick-turnaround weight. For Airbus dispatch this equals `landingWeight`; for Boeing it may differ when the structural cap is the binding constraint.
`appClimbLimit`	integer	Approach Climb limited weight
`fieldLimit`	integer	Field length limited weight
`ldgClimbLimit`	integer	Landing Climb limited weight
`quickTurnWeight`	integer	Quick turnaround limited weight
`quickTurnTime`	integer	Quick turnaround time (minutes) before next takeoff
`structLandingWeight`	integer	Structural max landing weight (MSLW)
`tireSpeed`	integer	Tire speed limited weight
`limitedBy`	string	Limiting factor code: `STRUCT.`, `MACG`, `FIELD`, `CLIMB`, `QUICK`, `TIRE`
`isOverweightLanding`	boolean	`true` when the actual landing weight (inflight) or the calculated max landing weight (dispatch) exceeds the structural maximum landing weight (`structLandingWeight` / MSLW). When `true`, an overweight landing caution is also added to `cautionMessages` referring to FCTM guidance. Always `false` for dispatch because the dispatch weight is capped at MSLW.

Performance — Balked Landing Procedure (Airbus & Boeing, PRO)

Returned as performance.balkedLandingProcedure for Airbus aircraft (dispatch and inflight modes) and Boeing aircraft (inflight mode). When the active runway's engine-failure procedure (EFP) is non-standard and the user holds a PRO subscription (is_balkedLanding), the API runs a parallel takeoff calculation — DRY runway condition, the same runway at full length, no takeoff weight (regulated maximum, TOGA / no FLEX) — to determine the maximum weight at which a balked landing (go-around) can safely clear obstacles. The go-around takeoff flap is resolved as follows:

Airbus — derived from the selected landing flap: CONF FULL → CONF 3, CONF 3 → CONF 2, any optimum/other selection → CONF 3.
Boeing — a fixed setting from the aircraft profile (landing.goAroundFlap), independent of the selected landing flap. Defaults to 15 for all 737 variants (737NG / 737MAX) and 20 for every other Boeing type when not explicitly configured on the profile.

When the EFP is standard (STD / STANDARD) the procedure is simply "Follow published missed approach." and no takeoff calculation is run.

When a landing enroute non-normal condition (NNC) other than NONE is selected, the balked-landing procedure is not applicable — the aircraft's configuration and performance are altered enough that the predetermined go-around procedure and its takeoff-weight check no longer apply. In this case procedure is "N/A", isCalculationRequired is false, and no takeoff calculation is run (regardless of EFP or subscription).

Field	Type	Description
`procedure`	string	The runway's engine-failure / balked-landing procedure text (formatted per the user's display preferences). When the EFP is standard, this is `"Follow published missed approach."` When a landing enroute NNC other than `NONE` is active, this is `"N/A"`.
`isCalculationRequired`	boolean	`true` when the runway's EFP is non-standard, i.e. a balked-landing takeoff calculation is required. This reflects the logic/warning only and is set regardless of subscription: it is `true` even for non-PRO users when a PRO user would have triggered a calculation. `false` when the EFP is standard.
`userAllowed`	boolean	`true` when the subscription includes the PRO balked-landing feature (`is_balkedLanding`); otherwise `false` and no weights are computed.
`maxLandingWeight`	integer\|null	Maximum takeoff weight (in the request's weight unit) at which a go-around can safely clear obstacles from this runway. `null` when the EFP is standard, the user is not PRO, or the underlying takeoff calculation returned no usable result for this runway.
`margin`	integer\|null	`maxLandingWeight` minus the reference landing weight (in the request's weight unit). The reference weight is the user-provided landing weight when supplied, otherwise the calculated dispatch-limited landing weight. Negative when the reference weight exceeds the maximum. `null` when no max weight was computed.
`goAroundFlaps`	string\|null	Recommended takeoff flap for the balked-landing (go-around) takeoff. For Airbus, derived deterministically from the selected landing flap (e.g. `"CONF 3"`, `"CONF 2"`). For Boeing, a fixed value from the aircraft profile, regardless of the selected landing flap (defaults to `"15"` for 737 variants, `"20"` for every other Boeing type when the profile doesn't override it). This is informational and does not depend on `isCalculationRequired`, subscription, or whether `maxLandingWeight` was computed — it is populated for both standard and non-standard EFP. `null` only when `procedure` is `"N/A"` (landing enroute NNC active), where no balked-landing guidance applies at all.

When the reference landing weight exceeds maxLandingWeight, a caution is added to caution: "In case of balked landing, the aircraft performance at that weight may not be sufficient to safely clear the obstacles. Reduce landing weight, or refer to your operator special procedure."

Performance — Speed Fields

Field	Type	Description
`vRef`	integer	Reference landing speed (knots)
`vFly`	integer	Target approach speed = Vref + additive (knots)
`vApp`	integer	Speed in the approach configuration (knots). Not to be confused with `vFly`, which some terminologies may also refer to as "Vapp".
`vMca`	integer	Minimum control speed approach (knots)
`vrefLabel`	string	Display label for Vref (aircraft-dependent, e.g., `"Vref"`)
`vrefAdditive`	integer	Applied Vref additive (inflight only)

Performance — Distance Fields

Field	Type	Description
`requiredLandingDist`	integer	Required landing distance (dispatch only)
`factoredLandingDistance`	integer\|null	Airbus dispatch only. Factored inflight landing distance at the dispatch landing weight, computed with autobrake OFF and the runway condition converted to its inflight equivalent (e.g. WET → GOOD, SLUSH → MEDIUM-POOR).
`actualLandingDistance`	integer\|null	Airbus dispatch only. Unfactored actual landing distance at the dispatch landing weight, same conditions as `factoredLandingDistance`.

Performance — Go-Around Fields

Field	Type	Description
`ldgGaClimbGrad`	number	Calculated go-around climb gradient (%) at 66% of the go-around altitude
`goAroundAltitude`	integer\|null	Calculated go-around altitude used for the climb gradient calculation. Does not necessarily represent the actual go-around altitude for the procedure being flown.

Performance — Autobrake Results (Inflight Only)

When landingMode is "inflight", the response includes an autobrakeLandingDist array with data for each autobrake setting. Entries are sorted by factoredDistance (shortest first).

Field	Type	Description
`label`	string	Human-readable, customizable autobrake label to display to the user
`autobrakeValue`	string	Autobrake `value` from the aircraft profile `autobrake` options (e.g., `"OFF"`, `"1"`, `"MAX"`)
`airDistance`	integer	Air distance component (flare + ground effect)
`landingDistance`	integer	Actual landing distance
`landingDistanceIsAboveLDA`	boolean	`true` if landing distance exceeds LDA
`factoredDistance`	integer	Landing distance × landing factor (regulatory)
`factoredDistanceIsAboveLDA`	boolean	`true` if factored distance exceeds LDA
`unfactoredDistance`	integer	Actual distance × 0.85 (15% EASA reduction). With NNC: actual distance (no reduction).
`unfactoredDistanceIsAboveLDA`	boolean	`true` if unfactored distance exceeds LDA
`order`	integer	Sort order (0 = shortest factored distance)

Performance — Brake Cooling Schedule

Each autobrake entry may include a brakeCoolingSchedule object when the aircraft supports brake cooling data.

Field	Type	Description
`credit`	string	Reverse thrust credit applied (e.g., `"CREDIT FOR ALL REVERSE"`)
`aerodynamicDrag`	boolean	Whether aerodynamic drag credit is applied
`ground`	string	Cooling time for ground scenario (minutes, `"CAUTION"`, or `"FUSE MELT"`)
`air`	string	Cooling time for air scenario (minutes, `"CAUTION"`, or `"FUSE MELT"`)
`btms`	number	Brake Temperature Monitoring System value
`energy`	number	Adjusted brake energy

Performance — VApp Details (Airbus Only)

Airbus aircraft return a vAppDetails object showing the VApp composition.

Field	Type	Description
`deltaWind`	number	Wind correction component (kt)
`athrOn`	number	Auto-thrust ON additive (5 kt if active, 0 otherwise)
`deltaIceAccretion`	number	Ice accretion correction (5 or 10 kt)
`approachCorrection`	number	APPR_COR = max(athrOn, deltaWind, deltaIceAccretion)
`vPilot`	integer	Pilot additional additive
`totalVrefCorrection`	integer	Total correction applied = APPR_COR + vPilot

Performance — Inflight Extras

Field	Type	Description
`nonNormalCondition`	string\|null	Applied NNC item (inflight only)
`runwayExits`	array	Available runway exit points (inflight only)
`graphic`	object	Generated SVG/PNG/JPG graphics. Inflight: `factored` and `unfactored` sub-objects, each containing `svg`, `png`, `jpg` URLs. Dispatch (Airbus only): additionally exposes a `dispatch` sub-object (single Required Landing Distance chart); `factored` and `unfactored` mirror that same image for backwards compatibility.

Dispatch Response Example

JSON

{
  "apiVersion": "1.3.6",
  "copyright": "Calculated by Virtual Performance Tool",
  "disclaimer": "For entertainment and educational use only.",
  "calculationPossible": true,
  "subCalculation": "LANDING_DISPATCH",
  "units": {
    "weight": "kg",
    "distance": "ft",
    "altitude": "ft",
    "wind": "kt",
    "depth": "mm"
  },
  "performance": {
    "flap": "30",
    "lda": 9800,
    "isNOTAM": false,
    "runwayIdent": "25R",
    "appClimbLimit": 66000,
    "fieldLimit": 65400,
    "landingWeight": 65400,
    "perfLimitedLandingWeight": 65400,
    "ldgClimbLimit": 66500,
    "quickTurnWeight": 63000,
    "structLandingWeight": 66361,
    "tireSpeed": 66361,
    "limitedBy": "FIELD",
    "quickTurnTime": 0,
    "ldgGaClimbGrad": 3.12,
    "goAroundAltitude": 1500,
    "balkedLandingProcedure": {
      "procedure": "STRAIGHT AHEAD TO 3000 FT",
      "isCalculationRequired": true,
      "userAllowed": true,
      "maxLandingWeight": 71200,
      "margin": 5800,
      "goAroundFlaps": "CONF 3"
    },
    "vRef": 138,
    "vFly": 138,
    "vApp": 143,
    "vMca": 115,
    "vrefLabel": "Vref",
    "requiredLandingDist": 5200,
    "graphic": {
      "dispatch": {
        "svg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.svg",
        "png": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.png",
        "jpg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.jpg"
      },
      "factored": {
        "svg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.svg",
        "png": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.png",
        "jpg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.jpg"
      },
      "unfactored": {
        "svg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.svg",
        "png": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.png",
        "jpg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResultAirbusDispatch_1_1775923266.jpg"
      }
    }
  },
  "caution": [],
  "remainingCalculations": 95,
  "extraCalculations": 0
}

Inflight Response Example

JSON

{
  "apiVersion": "1.3.6",
  "copyright": "Calculated by Virtual Performance Tool",
  "disclaimer": "For entertainment and educational use only.",
  "calculationPossible": true,
  "subCalculation": "LANDING_INFLIGHT",
  "performance": {
    "runwayExits": [
      {
        "name": "A6",
        "exitLength": 7696
      },
      {
        "name": "B8",
        "exitLength": 7552
      },
      {
        "name": "B9",
        "exitLength": 7309
      },
      {
        "name": "A5",
        "exitLength": 6092
      },
      {
        "name": "B7",
        "exitLength": 5062
      },
      {
        "name": "A3",
        "exitLength": 4166
      },
      {
        "name": "B5",
        "exitLength": 3996
      },
      {
        "name": "B3",
        "exitLength": 1899
      },
      {
        "name": "B6",
        "exitLength": 4432
      }
    ],
    "nonNormalCondition": null,
    "flap": "30",
    "lda": 10954,
    "isNOTAM": false,
    "runwayIdent": "25R",
    "appClimbLimit": 81311,
    "fieldLimit": 60000,
    "landingWeight": 60000,
    "perfLimitedLandingWeight": 60000,
    "ldgClimbLimit": 86183,
    "quickTurnWeight": 76446,
    "structLandingWeight": 66361,
    "tireSpeed": 86183,
    "limitedBy": "FIELD",
    "quickTurnTime": 55,
    "goAroundAltitude": 1500,
    "ldgGaClimbGrad": 6.5,
    "balkedLandingProcedure": {
      "procedure": "STRAIGHT AHEAD TO 3000 FT",
      "isCalculationRequired": true,
      "userAllowed": true,
      "maxLandingWeight": 71200,
      "margin": 11200,
      "goAroundFlaps": "CONF 3"
    },
    "vApp": 153,
    "vMca": 88,
    "vrefLabel": "Vref",
    "vFly": 142,
    "vRef": 142,
    "requiredLandingDist": 3007,
    "autobrakeLandingDist": [
      {
        "label": "AUTO BRK 3",
        "autobrakeValue": "3",
        "airDistance": 1500,
        "landingDistance": 6404,
        "landingDistanceIsAboveLDA": false,
        "factoredDistance": 6404,
        "factoredDistanceIsAboveLDA": false,
        "unfactoredDistance": 5443,
        "unfactoredDistanceIsAboveLDA": false,
        "brakeCoolingSchedule": {
          "credit": "CREDIT FOR ALL REVERSE",
          "aerodynamicDrag": true,
          "ground": "0",
          "air": "0",
          "btms": 2.3,
          "energy": 14.47
        },
        "order": 0
      }
    ],
    "vrefAdditive": 0,
    "graphic": {
      "factored": {
        "svg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResult_1_factored_1775923266.svg",
        "png": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResult_1_factored_1775923266.png",
        "jpg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResult_1_factored_1775923266.jpg"
      },
      "unfactored": {
        "svg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResult_1_unfactored_1775923266.svg",
        "png": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResult_1_unfactored_1775923266.png",
        "jpg": "https://api.virtualperformancetool.com/flightenvelope/Performance/landingResult_1_unfactored_1775923266.jpg"
      }
    }
  },
  "caution": [],
  "units": {
    "altitude": "feet",
    "distance": "feet",
    "weight": "kg",
    "depth": "mm",
    "pressure": "hpa"
  },
  "remainingCalculations": 597,
  "extraCalculations": 50
}

Dispatch vs Inflight — Quick Reference

Feature	Dispatch	Inflight
Landing weight	Calculated (max)	User-provided (required)
Autobrake	Ignored (OFF)	`"ALL"` or specific value
Vref additive	Ignored (0)	0–20 kt (min 5 for autoland)
NNC	Not available	Optional (subscription required)
MACG	Second request at DRY	From primary response
Icing check	Yes (OAT ≤ 10°C)	No
Autobrake distances	Not returned	Full array with brake cooling
Graphics	SVG/PNG/JPG — single dispatch chart (`dispatch`, `factored`, `unfactored` all mirror same image). Airbus only.	SVG/PNG/JPG factored & unfactored (per autobrake)
MEL/CDL	Accepted	Accepted (dispatch calc only)
NOTAM	Accepted	Optional