Runway Analysis Page Structure

The example screenshots below are from the Takeoff Analysis page for a 560 Citation XLS+; however, the Landing Analysis page and other aircraft types follow the same overall structure, though the details may vary. Every blue value is user-adjustable.

Runway Analysis Takeoff Outputs

NOTE: All takeoff performance outputs are predicated on an engine failure just prior to reaching V1.

Takeoff Thrust (N1, EPR)	Aircraft dependent, but typically the static takeoff thrust setting for the given conditions
V1	Takeoff decision speed; where the “go” or “stop” action occurs after deciding to fly or stop
VR	Rotate speed; where rotation is initiated
V2	Takeoff safety speed; speed attained 35 ft above runway surface with one engine inoperative; also target climb speed after engine failure to maintain during 1st and 2nd segments until level-off altitude is reached
VFTO	Final takeoff speed; target climb speed during Final segment
VENR	Enroute speed, after clearing all obstacles
TOFL	Takeoff Field Length; takeoff distance per AFM definition for the aircraft
Accelerate-Stop	Accelerate-Stop distance; distance from brake release through V1 plus stopping distance form V1 through full stop during a rejected takeoff
Accelerate-Go	Accelerate-Go distance; distance from brake release through V1 plus distance from V1 through rotation until 35 ft above runway surface is reached
1st/2nd Gradient	Climb gradient for the indicated climb segment
Level-Off MSL / Level-Off Alt	Target level -off altitude (in MSL) to clear all obstacles during a one-engine inoperative takeoff

 

Runway Analysis Landing Outputs

VAPP	Approach speed; a target speed flown during the approach phase of the landing, typically at approach flap setting and gear up.
VREF	Reference speed; a target speed slower than VAPP flown at landing flap settings and gear down to be achieved by 50 ft height and when crossing the landing threshold.
Actual Distance	Actual landing distance provided by the AFM for the given surface condition.
Factored Distance	Actual landing distance increased by a factor multiplier, such as 1.67 for the 60% Dry runway dispatch requirement.
Approach/Landing Gradient	Approach or Landing climb gradient for the AFM defined aircraft configuration

 

Runway Analysis FAQs

 

Q: What is Runway Analysis?

A: Runway Analysis answers this simple question for a pilot:

What is the highest takeoff or landing weight I can safely operate out of or into an airport? 

From a pilot’s perspective, Runway Analysis provides a single maximum takeoff or landing weight at which safe takeoff or landing is possible. The analysis of this maximum weight compares the available aircraft performance for given meteorological conditions and pilot selected aircraft configuration against multiple constraints, such as available runway length, terrain and obstacle considerations.

The available aircraft performance is provided by the aircraft manufacturer’s Airplane Flight Manual (AFM). The AFM includes data on how the aircraft performs under specific conditions, but also its limitations, such as climb capability limits, brake energy limits, etc. In addition to these aircraft specific constraints, environmental constraints such as runway length and slope, as well as terrain and obstacles surrounding the airport are considered in the analysis. 

If any one constraint cannot be met at the current takeoff or landing weight, the weight is reduced during the analysis, until a takeoff or landing weight is found, which satisfies all constraints, or takeoff/landing is deemed not possible at any weight.

Q: As a Part 135 operator, does your Runway Analysis solution comply with Part 135.379?

Yes. 14 CFR Part 135.379 (Large transport category airplanes: Turbine engine powered: Takeoff limitations) defines takeoff limitations for Part 135 operations that must be met. Our Runway Analysis solution complies with these requirements.

Q: How does Runway Analysis apply specifically to takeoff and landing?

A: For takeoff, an engine failure is always assumed during the takeoff run. The analysis provides the pilot a critical decision speed (V1) to establish a point during the takeoff run at which a stop/go decision can be made. If a rejected takeoff (stop) is chosen, the maximum takeoff weight (MTOW) solution ensures sufficient stopping distance for the available runway exists, while also respecting other stopping constraints, such as brake energy limits. If the pilot elects to fly with one engine inoperative (OEI), the same analysis provided MTOW ensures sufficient climb capability, as well as terrain and obstacle clearance, exists along a provided flight path called the engine out procedure (EOP).

For landing, the main goals with runway analysis are to provide a maximum landing weight (MLW) that ensures sufficient climb capability in case of an OEI go-around maneuver and to prevent runway excursion during landing and stopping for a given runway surface condition. As with takeoff, additional aircraft specific limitation are also checked. 

Q: What specific takeoff information is provided for an OEI takeoff?

A: Besides providing a MTOW and limiting reason for the analysis, the solution provides the typical V speeds (V1, VR, V2, VFTO, VENR) as well as the AFM published distance (either a single takeoff field length or accelerate-go and accelerate-stop distance for unbalanced field length solutions; depends on the aircraft).

After the selection of a departure runway and a planned OEI custom departure procedure, the analysis performs the 1st, 2nd and 3rd/acceleration segments for the climb analysis (some aircraft support a Final segment climb as well). An OEI acceleration level-off altitude is provided as an altitude target when clear of all obstacles and terrain or when the minimum required level-off height has been reached. 

Q: How does Runway Analysis differ from ForeFlight’s Takeoff & Landing Performance feature?

A: Takeoff & Landing Performance calculation was introduced by ForeFlight in June 2019 for hundreds of mostly single engine piston aircraft. The Runway Analysis capability builds on top of that, and is focused on multi engine turbine and turboprop aircraft, which are certified to provide OEI performance data. Runway Analysis is not available for single engine aircraft and most twin engine piston aircraft simply due to the certification method used for such aircraft.

Q: Does the Runway Analysis tell me what the limiting reason is?

A: Yes. With each analysis, the performance limiting reason is provided along with the maximum weight. When not limited by any constraint, the aircraft’s structural weight limit becomes the limiting constraint. This is visible in the takeoff or landing view header. 

Runway Analysis supports many constraints and limiting types, including climb capability, obstacle clearance, available runway length, brake energy and tire speed limits, minimum control speed and more. Each list of constraints possible is set by the AFM.

Q: What is an Engine Out Procedure (EOP)?

A: An engine out procedure is a custom designed, lateral flight path “escape route” to provide a climb departure designed to minimize obstacle and terrain constraints. The EOP is designed to be used only in cases where an engine failed during the takeoff runway. The EOP is not a Standard Instrument Departure (SID), which is designed for the normal, all engine operating (AEO) scenario. While an EOP may initially follow a SID path, this is not always the case, especially if terrain requirements dictate otherwise. 

When selecting an airport and a runway, most runways will offer a default straight-out option (”fly runway heading”). Terrain and obstacles along the runway heading path are used in the runway analysis to determine a MTOW that ensures clearing all terrain and obstacles along this path. Since the straight-out is a non-optimized flight path, it typically results in the lowest MTOW solution. 

Beyond the straight-out option, many runways include one or more custom designed RNAV EOPs with the goal of maximizing takeoff weight for an OEI climb. These EOPs are designed to minimize terrain and obstacle constraints, while also keeping flyability and pilot workload in mind.

RNAV EOPs are designed by ForeFlight and make use of various navigation aids, including GPS waypoints. The RNAV EOPs will typically provide the highest MTOW solution as they are purpose built to minimize climb constraints. When possible, they will also follow initial SID procedures to simplify a pilot’s workload, which may already have that SID loaded in the FMS.

When viewing the list of available straight-out and EOPs, the MTOW is calculated and displayed for each EOP, allowing quick and convenient comparison of expected performance for each EOP.

Q: How does Runway Analysis ensure obstacle and terrain clearance?

A: The FAA has published AC 120-91A, “Airport Obstacle Analysis”, which provides acceptable methods and guidelines for takeoff and climb obstacle analysis. ICAO has a similar publication which closely mirrors the AC 120-91A guidelines, but does include slight variations, such as the width of the obstacle corridor considered. These publications and their methods are used in the obstacle analysis evaluation for each takeoff. 

Note that the ability exists to set which obstacle corridor is considered in the obstacle analysis. Navigate to More > Aircraft > Your aircraft > Field Performance and in the Takeoff group select your Obstacle Corridor for your aircraft and operation. 

Q: What obstacle database sources are used in ForeFlight’s Runway Analysis?

A: AC 120-91A and the ICAO equivalent do not limit obstacle consideration to a specific set. Instead it is encouraged to consider all obstacle data sources available. ForeFlight considers and continually updates obstacles included in the analysis. This includes close-in obstacles found near the airport and runway environment. In addition, the user has the ability to add obstacles manually, which is useful for temporary obstacle consideration provided via NOTAM.

Q: Why can I disable obstacle analysis? When would I ever need to do that?

A: In short, never. Obstacle analysis should always occur with each takeoff calculation, even when no mountain or tower is in sight. Often, low, close-in obstacles in the immediate airport and runway environment can negatively affect MTOW with an OEI takeoff. We strongly discourage switching off obstacle analysis and clearly warn when the user elects to do this.

Is there ever a scenario to turn off obstacle analysis? While it’s never a good idea, some operators apparently have reasons to do this in select few circumstances, such as a departure over a large body of water in VMC conditions. 

Q: Does Runway Analysis computation work offline?

A: Yes.

Q: Does ForeFlight provide a printable summary sheet with my takeoff and landing computations?

A: Yes. After calculating takeoff and landing performance, tapping the Summary button displays a summary page for your exact conditions and computed results, as well as a runway matrix for the departure and destination airports, showing MTOW for each runway and at various OAT and wind conditions. 

Q: Is Emergency Return supported in the takeoff analysis?

A: Yes. In the takeoff workflow, it is possible to evaluate the emergency return landing performance to the takeoff airport. For this scenario only, overweight landing performance calculations are possible, but a warning of this is displayed to remind the pilot that an overweight landing is attempted. 

Q: Are Runway Analysis takeoff and landing weight calculations integrated with flight planning weight requirements?

A: Yes. After planning a flight and payload and fuel loads have been established, the planned takeoff and landing weights are automatically checked against MTOW and MLW requirements for the defined departure and destination airports. If the MTOW or MLW are more limiting than the planned takeoff and landing weights, the fuel load is adjusted to attempt flight planning within the provided weight constraints, while ensuring sufficient fuel load exists for the flight itself. If this is not possible, the user can manually adjust items as needed. 

Q: Are contaminated runways supported?

A: While it depends on each aircraft, if the AFM provides contaminated runway performance data, we include it in the aircraft performance model. Note that for FAA operations, these contaminated data are generally advisory only, not approved. Consult your aircraft’s AFM for full details.

Q: Are landing distance factors supported?

A: Yes. Performance calculations for the AFM provided surface conditions are available. Generally, these include actual distance for dry, wet and contaminated runway surfaces, but this depends on each aircraft and its AFM.

Additionally, the landing performance view includes a Landing Factor input. This is a landing distance multiplier of 1.0 or greater. Depending on the operation type, a landing at the intended destination (and alternates) must be shown to be possible with forecasted weather conditions and the use of a landing factor, which increases the actual landing distance to provide a safety buffer. The landing factor use is designed to ensure a successful stop on a portion of the available landing distance (LDA).

Part 135 operators must show landing and stopping ability using the 60% or 80% distance factors depending on their operation, meaning the aircraft must be able to land and stop on 60% or 80% of the available LDA for predicted weather conditions at time of arrival. For a predicted dry runway condition the AFM dry distance is factored (multiplied) by 1.67 to achieve the 60% Dry factored landing distance. This longer distance is compared to LDA. The process is identical for a wet runway condition, but the 60% Wet factor is now 1.92 times the dry AFM distance, which is 1.67 increased by 15%. 

Part 91K and some approved 135 operators use 80% distance factors, which are 1.25 for dry and 1.44 for wet runway conditions.

The landing factor selector includes these four common factors, as well as the ability to set a custom factor. 

IMPORTANT: If you always use the same landing distance factor, you can set it as the default per aircraft in More > Aircraft > Field Performance. If you are a ForeFlight Business account admin then you can update this setting for published aircraft in ForeFlight Web > Aircraft > Performance > Field Performance > View Defaults.

Q: Are Runway Condition Code (RCC) landing distances available for the upcoming ICAO Global Reporting Format (GRF) launching in November 2021?

A: This depends on each aircraft. If the aircraft manufacturer has published landing distance data for the various RCC values, we will include these options. If these data are not yet available, the aircraft will not support RCC based landing distances.

Q: Where can I learn more on Runway Analysis topics?

A: The FAA provides four excellent videos on runway analysis topics:

• - Planning for takeoff obstacle clearance
• - Declared Distances
• - Wet Runway Takeoff Performance
• - Landing Distance Assessment