Behind the Data of Takeoff & Landing Performance

With ForeFlight’s introduction of Takeoff and Landing Performance in version 11.4, it’s a good time to revisit your Pilot Operating Handbook (POH) and get reacquainted with the runway performance data in it. It’s important to understand that the runway performance results provided by ForeFlight are based on the published data in the POH. ForeFlight’s calculations are only as good as the data provided by your aircraft’s POH.  Since we support aircraft models spanning multiple decades, POH data content and variation is large.

Take, for example, single-engine Cessna pistons. Looking at Section 5 (Performance) of the POH, you will see the takeoff and landing distance tables provided are titled Short Field, meaning the short field takeoff and landing techniques need to be applied to achieve the published distance numbers. This often involves rotating or approaching at a slightly slower airspeed, often with non-zero flap setting.

But many of us take off and land using the Normal procedure, outlined in Section 4 of the POH. The Normal procedure often advises different (faster) speeds and with flaps up. But few POHs provide any guidance on how takeoff or landing distances change when using the Normal procedure vs the Short Field procedure. When using one of these aircraft, it is critical to be aware that you are seeing Short Field distances in the ForeFlight results, which are shorter than what you will experience if you fly the Normal procedure takeoff and landing.

To help you recognize this, ForeFlight adds a “(Short Field)” note after the Flaps setting under Aircraft Configuration when using an aircraft that only provides Short Field distances. You can also review our list of Takeoff & Landing Performance supported aircraft here to see which ones only provide Short Field distances.

short field flaps

Another factor you must consider is the lack of certain corrections. Many piston POHs do not provide runway slope or non-paved runway corrections to the distances. All data are published for paved and level runways, which is what ForeFlight uses. Even though ForeFlight provides a user-adjustable runway slope input, changing this value does not affect the resulting distances. This is because such POHs lacks correction values for the runway slope.

It’s a great time to pull out the POH and study its runway performance section closely, so you know exactly what ForeFlight’s takeoff and landing results mean for your own aircraft’s performance.

A Closer Look at Takeoff & Landing Performance

ForeFlight 11.4 brings an exciting and safety-enhancing feature to Performance Plus subscribers: Takeoff & Landing Performance calculations for piston and single-engine turboprop aircraft. Give our tutorial video a watch and then read on for more details.

Why Takeoff and Landing Performance?

Calculating one’s takeoff and landing performance has always been a task that makes sense to do, but is often not carried out for various reasons. The task typically requires interpolating on tabular data or using graphical runaround charts, or “spaghetti charts”, to find a list of performance parameters for the given conditions. While useful in determining takeoff and landing distances, climb performance, and other critical aircraft performance parameters, the use of such tables and charts are less than appealing to many pilots. It’s also surprisingly easy for human error to sneak into the multi-step process of determining takeoff ground roll or total distance, possibly resulting in a less than safe operation.

Why not let software handle these error-prone tasks accurately, quickly and in a repeatable fashion?

A Fully Integrated Flight Planning Solution

ForeFlight is improving safety of flight by providing a fully integrated takeoff and landing performance solution into the existing flight planning workflow. With version 11.4, you have the ability to accurately and quickly calculate takeoff and landing performance for over 200 popular piston and single-engine turboprop aircraft as part of your flight planning workflow. This powerful combination of accurate runway and flight planning performance calculations provide critical information for your decision making and safety of flight.

For example, a DA40-180 pilot accustomed to flying near sea level knows a fully loaded aircraft on a calm, 95F/35C day can easily take off on a 4000 ft runway, requiring about half of that distance to reach the 50 ft obstacle height point. But if this pilot decides to fly in Denver, Colorado during a trip, it might come as a surprise that the same summer conditions require a full 4000 ft to reach the same 50 ft AGL point.  This is the effect a density altitude change from 2600 ft to 9000 ft has on a piston aircraft — significantly reduced aircraft performance.

With ForeFlight’s Takeoff & Landing Performance solution integrated into your flight planning workflow, you will not be caught by surprise when environmental changes negatively affect your runway performance. Ground or inflight (ADS-B) sourced weather data are used to prefill weather inputs for takeoff and landing times. The pilot can always manually override such prefilled data with the latest information from tower or ATIS. Distance results are compared to the available runway length and the pilot is warned if that is exceeded. If a runway has declared distances, the pilot is given this information and has the option to substitute a declared distance in lieu of the available runway length.

Where does the performance data come from? Your aircraft’s Pilot Operating Handbook. Our aircraft performance data team uses the official published takeoff and landing performance data from the POH to build a performance model for your aircraft. ForeFlight takes the error-prone interpolation and chart reading tasks and does them for you, accurately and quickly, whether online or offline.

Let’s take a detailed look at how this works in ForeFlight.

Walkthrough

It starts with planning your flight on the Flights view, as you currently do. Once you’ve established route, aircraft, ETD, payload and fuel load (important as they determine takeoff and landing weights), you enter the takeoff or landing performance page by tapping on either button presented in the Departure and Destination fields. We’ll calculate our takeoff here, but the landing calculation is nearly identical in workflow and look.

The top section of the takeoff page is where we pick our departure runway. This is currently a pilot’s choice. Tapping the runway selector, all available runways at the departure airport are presented. Wind component along each runway is provided by green (headwind) or red (tailwind) arrows along with the component magnitude. Grey crosswind arrows and magnitude are also displayed. More information on each runway can be obtained by tapping the Details button. Finally, the current METAR, TAF or MOS (if available) derived weather data is presented for your ETD.

   

Selecting a runway triggers the performance calculation sequence. At this point, all inputs — selected runway, environmental conditions, and default aircraft configurations — are used to perform the table interpolations and graphical chart readings to find all relevant takeoff performance results for this condition. Note that aircraft configurations (flaps, cowl flap, anti-ice controls, etc) are currently defaulted to a setting.

Above the runway selector, a header shows the most critical takeoff or landing information, typically a total distance and one or more target V speeds. The full output list is found in the Calculations section at the bottom of the page. The length and content of this list is driven by what runway performance data can be calculated per the aircraft’s POH.

   

To keep the list somewhat consistent, however, the following general output order can be found for every aircraft:

  1. Takeoff speeds and distances
  2. Takeoff climb data
  3. Enroute climb data

And for multi-engine aircraft, one-engine inoperative (OEI) data:

  1. OEI Max Takeoff Weight
  2. OEI Takeoff distances
  3. OEI climb data

Predicted takeoff and landing distances are compared to the available runway length and a warning is provided if the predicted distance exceeds the available length. In the example below, the available runway length input was manually shortened to the runway’s Accelerate-Stop Distance Available (ASDA) declared distance. In this case actual accelerate-stop distance is predicted to slightly exceed the ASDA declared distance. Use of declared distances (versus the physical available runway length) is entirely up to the pilot and any declared distance are provided in the runway section footer.

Final Takeaway

Takeoff and landing performance integration into ForeFlight’s existing flight planning flow is a significant safety improvement for all pilots. Whether calculating the takeoff performance out of a hot/high/short runway or calculating one’s landing and stopping performance just prior to landing using the latest weather information available, this feature can greatly enhance operational safety. Last second runway change? No problem with the fast and accurate offline takeoff and landing performance calculation ability.

It’s important to realize that the Takeoff and Landing performance integration uses your POH performance data. So all assumptions and input parameters, as well as published limitations — temperature, weight, altitude, wind, runway slope ranges — are modeled exactly as they exist in your POH. If a hot temperature condition at a specific pressure altitude is not published, ForeFlight cannot calculate performance for that condition and will not present results. Now is a good time to re-familiarize yourself with your aircraft’s takeoff and landing performance data in your POH, using ForeFlight’s ability to quickly and accurately calculate these results, while learning about the full capabilities of your aircraft.