Take-off performance is one of the most crucial aspects of planning a flight. We have a legal obligation as pilots to check that the aeroplane will have adequate performance for the proposed flight. Here’s a video sharing that importance.
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I am not a flight instructor, so please consult your relevant manuals, guidance materials and your instructor/flight examiner. This video is purely my experiences and me sharing with you in the hope I could do much better.
We have a legal obligation as pilots to check that the aeroplane will have adequate performance for the proposed flight and whilst it may not of course be necessary before every flight, the CAA [UK Civil Aviation Authority] states a cursory check of performance will do, especially on long runways such as 3000 meters.
But where is the line drawn?
Here’s an example below of a flight that I did weight & balance and take-off performance for at home. But maybe, this should have been done at the airfield again prior to departure to account for some more variables, or peace of mind.
With an outside air temperature of 13° C and a pressure attitude of 0 feet along with a take-off weight of just over 1000kg, which is the usual weight for 2/3rds fuel and two persons combined with a headwind of 10 knots, the take-off roll was reduced to 300 meters. This didn’t account for any gusts which made things a little more interesting.
The important thing to remember with gusts is that whatever airspeed you gain, you eventually loose. When the gusts drop off, you loose airspeed very quickly. It can become quite uncomfortable and I usually brief my passengers prior to departure for a tighter belt.
Where can you find the information?
It is strongly recommended that the appropriate Public Transport Factor is applied. In addition to this, the aeronautical Information circular goes into more detail on the NATS AIP website. Its AIC 127/2006 (Pink 110).
Here you can find all the factors and the know how to get similar and safe results for your flights. You can find all the AICs from the homepage by visiting NATS AIP > Aeronautical Information Circulars (AICs) >
Aeronautical Information Circulars (AIC) are notices containing information that does not qualify for the origination of a NOTAM or for inclusion in the AIP. As a general rule, AICs refer to subjects that are of an administrative rather than an operational nature. In order to facilitate easy selection of AICs they are printed on different coloured paper according to their subject matter as described.
Decision making –
Having decided on the factors and upon reaching the figure of 300 meters, which was based on the flight manual, we then must apply the figure for [Dry grass] = x1.20 and then the [Unfactored Data] = x1.33 to reach our safety net figure for departure. This totals 478.8 [480 meters].
I applied the take-off mass of 1150kg for my calculations. The aircraft was significantly less than that in weight & balance calculations, and the airfield was using the short-field runway for operations. Other aircraft appeared to take advantage of the strong headwind for take-off, making my selection an obvious choice and fitting in with airfield operations.
Runway 10/28 is an unlicensed grass runway at Stapleford Aerodrome and is mainly reserved for landings that would otherwise be too difficult on the usual main runway. Strangely I’ve only ever used it once for landing and once for departure prior to this flight, making it’s condition somewhat brilliant.
Post Analysis –
It’s very clear despite doing calculations in the Aircraft Flight Manual [AFM] and the legal requirements specified as the Public Transport factors, (i.e. Net Performance) that the exact conditions were less than favourable, but we’re within legal recommendations.
Having got airborne by 425meters, we reached 50ft above the runway height at 500 meters. This was GPS data based on raw information provided by SkyDemon which was linked to a Garmin GLO. The Garmin utilises GLONASS satellites for precise position and accuracy.
Despite calculating the variables affecting performance together with factors for non-Public Transport operations and flying the aircraft in accordance with 4A.2 (Airspeeds for normal operating procedures), the take-off roll and climb out performance was far from ideal. These safety figures in the AIC represent the increase to be expected in take-off distance to a height of 50 feet, or the increase in landing distance from 50 feet, and are intended to be carried for easy reference.
During the climb-out phase the stall warner is activated, whilst alarming this is normal for this variant of DA40; most notably during turbulent conditions. Provided a VR of 59KIAS and VY of 66KIAS is observed for a flight mass of 1150kg. This is the correct procedure for the best rate of climb. I opted for on instruments soon after rotation as it allowed me to accurately fly the aircraft in gusty conditions.
The stall speed for take-off flaps and no bank angle is 51KIAS. In the AFM, section 4B.5 it states that control stick should be released slowly after the nose wheel has lifted and allow for an increase in speed at low level, I allowed a more significant increase than usual on clearing the 50ft obstacle due to the localised wind shear coming of the trees.
In hindsight as a result of this experience I decided to release the video to show that even following the flight manual, adding additional net safety figures – actual performance really can differ greatly than anticipated.
I feel it’s important to better myself as pilot in command and that a comprehensive pre-flight planning quick reference sheet comprising of the aircraft flight manual, performance charts and net safety figures can be created to enhance the skills of my piloting in advanced of commencing my Instrument Rating. This would include the 50/70 rule and accelerate-stop distance available (ASDA), EFATO actions, something frequently used in commercial aviation and ATOs across Europe and may have prevented me from considering departure from Runway 10.
In the future it’s essential a more comprehensive departure brief in the aircraft is completed so that any factors and safety requirements are met.
As aforementioned, it’s important to consult your flight manual for specific information. I am not a flight instructor, so please consult your relevant manuals, guidance materials and your instructor/flight examiner.
I hope that by sharing this experience with technical information on YouTube that it raises awareness so that I and others can learn, and encouraging people to routinely do weight and balance and performance checks before each and every flight.
This post has been updated to make it much clearer and provide more technical information.
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