Take Off & Landing Performance

This tutorial has been prepared to assist in understanding of the performance of Jabiru aircraft under different conditions.

We'll be specifically looking at the criteria as applied to the Jabiru 160C, but the same techniques apply to other Jabiru models. Please note that the method used is specific to Jabiru, and does not apply to other makes of aircraft. The source of data is the Pilot Operating Handbook.

The following information is extracted from the Jabiru 160C POH, but you should always go to the specific aircraft POH when sourcing data for an actual flight.

DO NOT ATTEMPT TO TAKE OFF ON THE GRASS RWY 04/22 AT ORANGE ON HOT DAYS (30 DEG +) UNLESS THERE IS AT LEAST 10 KT HEADWIND. 

Take Off Performance

takeoff

Notice from the table, we need to know the Pressure Altitude (or Pressure Height - same thing), and the temperature, to be able to work out the Take Off distance at maximum take off weight (MTOW). If you're not sure about Pressure Altitude, have a look at the tutorial on Altimetry!

Once we have the Pressure Height, we can read off the take off distance required against the Outside Air Temperature (OAT), however this only applies when we're taking off on a level bitumin surface, such as runway 11 or 29 at Orange. If we need to use the grass cross strip, or a grassed or gravel strip an another aerodrome, we have to increase the distance required by 7% (multiply by 1.07).

If there is a consistent head wind, or head wind component, we CAN reduce the take off distance required by 11 metres for each knot of head wind (don't have to!), but if there's a tail wind, we MUST add 16 metres for each knot of tail wind. As a general rule, always take off into wind.

Example

What take off distance is required in the Jabiru 5022 to take off on RWY 22 with a short dry grass surface, when the wind is 250/10kt, QNH is 1013 and the air temperature is 28C?

When QNH is 1013, the aerodrome elevation is also the pressure altitude, so at Orange, elevation 3,100ft AMSL, the Pressure Altitude is also 3,100ft, and we'll round that down to 3,000 ft.
There's no pressure altitude in the table above for 3,000ft, but it's OK to interpolate values within the table, so we can say it will be half way between the 2,000ft and the 4,000ft distances. Similarly, we can interpolate temperatures, but at 28C, we'll play safe and use the figure for 30C.

The distance required from the table is half way between 553 and 630 metres, which is pretty close to 592 metres.

However, this is in nil wind conditions on bitumen! We must increase this distance by 7% to account for the "slower" short, dry grass surface. 592x1.07=633 metres.

Now we can allow for the headwind component. Don't have to, but for the exercise, the wind at 250/10 is 30 degrees off the nose of the aircraft, so the headwind component is 8 to 9 knots - lets again play safe and call it 8 knots. we can reduce the 633 metres reuired by 11 metres for each knot of headwind component, so 8x11=88 metres and 633-88=545 metres. Answer: 545 metres.

Landing Performance

landingThe Jabiru's landing performance is calculated in exactly the same way as the take off performance, except that no correction figures are provided for the runway surface. The notes say that distances will be increased for a wet or slippery level bitumen surface, but soft ground or grassed surface actually improve the landing performance, because they provide a greater retarding force during the roll out phase of the landing.

Further, you have been/will be taught to land using a "constant attitude" approach, which is a powered approach. This, coupled with variations to the approach caused by turbulence, wind shear, less than perfect control of power and airspeed, mean that the figures should be regarded as an absolute minimum. You should always expect to use a lot more runway than shown in the table, especially whilst learning.

You should also avoid using maximum braking where possible, especially on the grass or other rough surfaces. Brake as necessary and accept a longer backtrack.