Air Safety

Perhaps there is no single, optimum way of landing an aeroplane. But let’s look at the problem in a different way. What are we trying to achieve? What are the objectives?

Ultimately, the objective of the landing is to bring the aircraft to a stop, on the runway, with some room to spare, having not strained the braking system or exceeded the limits of the aircraft in any way. Further, the passengers or cargo should not have been damaged, bruised on even discomforted by the experience.

To achieve this, the aircraft must have touched down reasonably gently and at a speed that was within the energy-absorbing capacity of the aerodynamic and mechanical braking systems. For it to be gentle, the touchdown requires a degree of control by the pilot which is derived from the stability and control characteristics of the aircraft and the environmental conditions at the time. This requires a level of skill and judgement from the pilot to establish control, to achieve the optimum speed, to judge the flare, to assess the conditions and to correctly decide on the suitability of the conditions for that aircraft to land on that runway, at that time. This skill and judgement comes as a result of training and experience but also depends on day-to-day factors such as currency, fatigue and stress.

To achieve a smooth and progressive flare to touchdown also requires that the pilot correctly assesses the conditions. The safety and smoothness of the landing results from the pilot flying a final approach within limits of speed, glide path, bank angle, sideslip angle and as a result of fine control of attitude, configuration and power setting.

To achieve this approach the pilot has to anticipate and establish accurately his ‘targets’ for the approach and then to assess the control requirements needed to achieve those targets. The pilot also has to determine the tolerances that he or she will accept as the basis for a decision to continue the approach or to go round.

Every pilot does this on every approach- don’t we?

There are three main elements to each approach: decisions, application and technique (which if it all turns to worms, includes escape routes).

Decisions

There are three aspects to the pre-approach decision-making:

• gathering of information about the strip and the conditions,

• assessing that information in relation to the capabilities of the aircraft; and

• assessing that information in relation to our own capabilities (and I am referring to our capabilities in that aircraft, on that day in those conditions).

During the initial stages of joining the circuit, the pilot needs to gather information regarding the strip and the weather conditions in terms of: length; surface; slope; obstructions; underruns and overruns; surface wind; mechanical turbulence and wind shear particularly near the threshold; and visibility, particularly near dawn and dusk.

Then the pilot needs to make the first decision in relation to the aircraft and its ability to cope with that strip in those conditions and including crosswind limits; weight in terms of threshold speed and required strip length and the possibility of a safe ground; and the landing configuration for the conditions such as use of full flap.

For example, it may be that a longer strip with a crosswind may be safer than one that is aligned into wind but is of marginal length.

Finally, the pilot needs to consider and decide on his or her own capabilities in terms of:

• currency, experience and confidence in that aircraft, in those conditions; and

• confidence and control in achieving the planned threshold speed and touchdown point.

These decisions should be absolute-if there is any doubt we must go round or go elsewhere.

Application

The pilot having made the decisions, then needs to put them into effect. There are three elements to this:

Procedures: the circuit and approach rely on standard procedures as a means of fitting in with other traffic, to give ourselves time to ‘read’ the conditions and to ensure that the final approach is begun from a consistent point.

Checks: each aircraft has certain checks and double-checks to be carried out before each approach and landing. It’s a good idea to have a ‘final’ check as well as the normal pre-landing check.

Standards: the standards that we set ourselves to determine the accuracy, consistency and safety of our approach. They require knowledge of the aircraft, motivation and self-discipline to actually strive for the standards we set.

Technique

The technique for landing an aircraft is one of the most argued topics in the aero club. The technique includes the visual references that a pilot uses as the basis for judging the approach as well as the actual control inputs a pilot makes to achieve a desired aircraft attitude or approach path. I would make three points:

• it is important to start each approach from a consistent base point

• it is important to use the correct references for judging the approach and landing

• it is important to trim the aircraft for the configuration and airspeed.

As a basis for discussion, let me describe the way I fly an approach and landing: Let’s assume we have made our inbound call, checked the aerodrome diagrams and mentally plotted the position of other traffic. From the forecast wind we anticipate the runway direction and offset our arrival to join on the dead side at 500 feet above circuit height and so as to keep the windsock in sight.

This initial arrival stage includes a combination of procedures, checks and standards.

Next comes the assessment of the strip and the weather conditions. We let down on the dead side to circuit height and join crosswind.

Crosswind is the time to have a closer look at the approaches and overshoot area. A double-check of the windsock is also good value.

Downwind is the critical time for checks (particularly the gear) and for establishing the approach goals in terms of touchdown point and threshold speed. These give us the references for the approach – the desired aircraft attitude and the aim point on the runway.

Now to technique – I try to fly an accurate, parallel downwind leg to assess the drift and to achieve the consistent base turn point. Then I take another look at the windsock to check the. Consistency of the wind-the gustiness and the interaction with any trees or buildings on short final. We are making a prediction about the probability and severity of wind shear and therefore anticipating possible control difficulties on final.

Procedures the base call and a look for traffic. The base turn is the basis for the approach and I initiate the descent after configuring the aircraft for the approach. I put down about half the flap at this point, adjust the power, set the attitude which I know will result in the correct airspeed or close to it and then I carefully trim the aeroplane.

Having stabilised the aircraft in the approach configuration, there is time on base leg to reassess the wind and anticipate its effect for the turn onto finals. A tailwind on base which causes a tightening turn onto final is a major risk area for a stall. If there is a tailwind it is better to start the turn earlier than normal and reduce bank as I go rather than be caught flying through the centreline and having to ‘rack it around’.

Final is the critical stage. Firstly I check-PUF double- check the gear is down, that the prop is ready for high power and then I make my ‘final’ decision before selecting full flap.

This decision relates to a self-assessment. How am I going? How well am I coping with the conditions? Am I absolutely sure that I can achieve the planned threshold speed? Am I absolutely sure that I will achieve the planned touchdown point? Is there an escape route? Once the decision is made to continue the approach, I select full flap, adjust the attitude and re-trim the aeroplane.

Now I aim to fly a stable, nominally constant attitude approach. I peg the attitude and set the power and the speed will stabilise close to where I want it. Check the aim point- is it stable in the windscreen?. Cross check – aim point, attitude and airspeed- aim point, attitude, airspeed.

I fly a constant approach path by trying to fly my eyeballs to the aim point- the piano keys if there are any. I do whatever is necessary to the power and the attitude to keep my eyes on a constant path to the threshold. A small correction to the aim point requires only a power adjustment whereas a larger correction may need both a power and attitude change – I work at it to achieve it. Small, early and continuous corrections.

Now to the ‘crunch. As I cross the threshold, the aim point serves no further useful purpose. As soon as I am sure that the aircraft’s momentum will carry me to the aim point I transfer my attention to the centre of the far end of the strip.

The reasons I use this reference are: it gives an attitude reference throughout the flare it gives the best directional information during the landing it gives the best distance-to-go information

it gives the best drift information it gives the most stable flight path information.

But I don’t just look at it. I close the throttle and fly the aircraft so that my eyes track down the centreline and I actually try to reach the other end of the runway- I can’t of course, because of reducing airspeed but I have a continuous and easy-to-use reference for control of the aircraft during the flare and the aircraft actually lands itself.

This technique ensures that the aircraft does not touch down prematurely and that I don’t overcorrect. By using the far end as a reference and actually trying to reach it, I naturally damp out any overcorrections and it avoids the tendency to force the aircraft onto the ground prematurely, to freeze on the controls or to touch down the nosewheel first. It is also self-compensating for runway length.

Align the aircraft with the centreline before I feel it is about to touchdown and I lower the into-wind wing progressively if I need to.

In a taildragger or a landing with less than full flap, the far end of the runway will disappear from view as you flare – as will any other reference. I find that with a little practice, I can imagine the position of the centre of the other end of the runway by pretending that the nose of the aircraft is transparent. There are sufficient visual cues to make this estimation quite accurately. Perhaps this is how we have always landed an aircraft without realising it.

The technique still requires an accurate threshold speed and achievement of the aim point but when I approach it in this way, I find I usually do. It really helps with consistency.

Try it with your instructor some time. The important point is to actually try and fly to reach the centre of the far end of the runway – don’t just look at it – go for it.

Happy landings.