I’d like to share a couple of hands-on techniques which I hope pilots will think about and benefit from if they haven’t come across them yet. As far as possible I will keep it simple enough for the layman to understand, but sometimes there is no substitute for going into the finer details.
One thing I detest is using analogies which have no relevance. Reasoning from first principles is almost always the better option. Sometimes it just takes a bit of time to wrap your head around a new idea, so if you do not understand, just be patient, ask questions and play with the notion in your mind until you grasp it better. When I first heard of the mysterious Coriolis force and its effect on wind and weather phenomena such as cyclones, it took me some time to grasp it!
Proper take-off technique. Let’s start with what our objectives are. We want to be in the air quickly, save wear and tear on the propeller/airframe/engine, transition from accelerating to equilibrium flight smoothly and clear obstacles by a safe margin.
Ok, so let’s think of how we can use our surroundings to benefit us the most and keep safety a priority.
- Wind – take off into the wind to reduce ground roll.
- The slope of the runway – downhill will reduce ground roll as gravity assists you with accelerating. Downhill with a slight breeze from behind may be preferable depending on the slope and wind.
- Sun – avoid taking off into the sun as far as possible. On a chilly morning with a slightly fogged windscreen and the sun on it, it can be downright dangerous if you lose sight of where you are going.
- Terrain – do you need to make turns after takeoff to avoid mountains? Oh, let’s not forget nasty downdraughts if you are planning to clear those hills and mountains, rather take off in the other direction if possible.
Ok, now let’s talk about configuration. Depending on your aircraft you would select a certain amount of flap. From the Cessna 210 point of view, we use 10 degrees of flap as per pilots operating handbook (POH). The first 10 degrees of flap increases the surface area of the wing which creates a large amount of lift for a small penalty in drag. We, therefore, become airborne much sooner and it is more beneficial than zero degree flap (with a better lift to drag ratio). Stall speed is now also lower which gives an added safety margin.
In very few cases it makes sense to use more than 10 degrees of flap, such as when you have a very sandy runway and the trade-off of having a worse lift to drag ratio, but more lift meaning you would get airborne quicker and have less friction on the tyres sooner makes sense. This configuration is sometimes wrongly used for clearing obstacles on a short field. A worse lift to drag ratio (using more flap) would create a steep climb angle but not quite as steep as optimum flap setting for Vx (best angle of climb) and maintaining Vx as accurately as possible. This will be stated in your POH and should be followed.
Technique. Release brakes with power on or rolling take off (slingshot)? Most POH’s say that before starting a short field takeoff roll you would add power before releasing the brakes. This is good, as the initial part of your takeoff is very important because you are generating a large amount of thrust at low airspeed. The one thing about this technique is that your propeller will be picking up stones right in front of it and causing some damage. Another technique is (nicknamed the slingshot) to start adding power while you are rolling either from a taxiway or on the turnaround. What I like about this technique is that you have already broken static friction (kinetic friction is much less), and you start with momentum which your propeller will be thankful for picking up fewer stones.
Where should your control column be? Well, it depends. If you have plenty of runway and aren’t heavy, you would gradually release pressure from fully back. With a large amount of thrust, you would be able to keep your nose slightly higher, protecting your propeller from stones. However, if you are on a tarred runway, short runway, heavily loaded, high elevation field or a combination of these, you would keep your elevator neutral in order to be as aerodynamic as possible and accelerate to Vr (rotate) as quickly as possible. On the roll, you would check that your temperatures and pressures are in the green, fuel flow is where you intend it to be (may be higher or lower depending on density altitude), your propeller RPM is where it should be and that your airspeed indicator is indicating an increase in speed (hence the call out – airspeed alive). Should something not sound right, feel right or look right the take-off should be aborted.
With high elevation, long runways, one would opt to rotate slightly later and make use of the runway length. This is done as you would be able to accelerate in a shorter time to the speed you want to climb out at. There is a significant amount of induced drag once you rotate, so this should be done with a smooth force on the control column and trim being set according to all these factors in mind. A good rule of thumb is that you should be at 70% of your rotation speed at or before 50% of the runway. Once you have rotated the next game begins.
Are we climbing to clear obstacles? If so, one would accelerate to Vx and keep it. If you are dealing with high-density altitude, you would keep accelerating in ground effect. If no obstacles are in your way you would start a shallow climb and accelerate all the way to Vy (best rate of climb). This is more common and better for your engine (more airflow = more cooling) and safety. The latter, to get away from the ground in the shortest possible time so that you can deal with any emergency situation that may arise.
After all, the fan in the front is just there to keep the pilot cool!
The information contained in this blog is for general information purposes only. My website assumes no responsibility for errors made from following the advice given. Always consult your flight instructor and pilots operating handbook for information.