Ground Rush. (Part Four) Landing an Aeroplane. An Aviation Training Blog by Owen Zupp.

Owen Zupp - Friday, June 29, 2012

 

 

Ground Rush. (Part Four)

 

 

Hit the Spot.

 

As we fly down our final approach we are always assessing our aim point. That imaginary spot on the runway where we project our flight path will lead us to connect with the runway. A stable approach sees that aim point sitting steadily upon the same point in our windscreen as we drive towards it at the nominated approach speed. Unfortunately, that spot can sometimes wander up and down the windscreen.

 

‘Nailing’ that aim point is more commonly referred to as aim point retention. A frequent scenario sees the aim point move further down the runway in the latter stages of the approach. Sometimes this is because in the heat of battle the pilot loses a degree of discipline in focussing on the specific point, lost in the looming runway. Occasionally, it results from trepidation on the part of the pilot manifesting in unwarranted back pressure on the control column, raising the nose. In either case, the touchdown point will occur much further down the runway, just as if excessive speed had been carried into the flare.

 

Equally, ‘target fascination’ with the aim point can result in the pilot arriving at the correct point, but driving it into that point rather than flaring. In the worst case the nosewheel can actually touchdown first, causing damage or a potential ‘wheel-barrowing’ situation; neither are advisable. This issue can be particularly significant at night as the landing lights illuminating the runway almost transfix the pilot’s line of sight to the tarmac at the very time that the eyes should start to look ahead. The goal is to retain the aim point until we arrive at that wonderfully vague point in space where flight down to the runway transforms into the landing manoeuvre known as the flare. Hold onto the aim point for too long and the aircraft will most certainly make an arrival rather than a landing.

 

Just as with speed, aim point retention or lack thereof, can be a contributing factor in the ‘where’ and ‘how’ of an aircraft’s landing. Often aim points can wander or become hypnotic when pilots are tired and the end of a long day, or a session of circuits. Be aware of where you are looking and work at flying there, but also be ready to release the point when the flare dictates.

 

Showing Some Flare.

 

The flare is undoubtedly one place where aviation science and art frequently speak a different language. Even for the most experienced pilot, the timing of when to transition into the landing manoeuvre can be misjudged. It is a skill that comes with practise and a right of passage that all students must endure along their journey. However, just as precision in parking a car improves with time and familiarity, the visual cues will begin to establish themselves in the pilot’s mind’s eye with greater exposure.

 

 

 

 

 

At that point when the approach becomes the landing, the pilot’s eyes should release the aim point and rise towards the runways end. At this point the ground will rise in the peripheral vision and assist in judging the rate of closure while the focal point ahead will offer cues for maintaining directional control. The pilot is now endeavouring to bleed the energy from the aircraft by reducing power and increasing the angle of attack with back pressure. Lift is still being generated, but without adequate energy, level flight is replaced by a controlled descent to the runway. Occasionally, the reduction in power is not complete and the aircraft may elect to continue flying in ground effect, so make sure that when it is time to land, the thrust is reduced fully.

 

 

Playing it Straight.


The need to be aligned with the runway at touchdown has been previously emphasised. It avoids directional control issues during the ground roll and undue trauma to the undercarriage. The most obvious challenge to this objective is the crosswind and instructors and students continue to battle this fiend using a variety of techniques from the ‘side-slip’ to the ‘crabbed’ approach where the aircraft is aligned in the flare.

 

Yet at times, the wind does not need to be abeam for runway alignment to wander. On final, pilots develop a ‘wing walk’ where they oscillate aileron, or occasionally rudder, inputs with a resultant rolling or yawing motion. Presenting as gentle S-Turns as the pilot chases the centreline, it is often merely a case of P-I-O; (Pilot Induced Oscillation). PIO can occur with the use of elevator as well and results in a lot of effort for no benefit. If centreline management is proving a struggle on final, then relax all control inputs and see if the aircraft is actually trimmed and flying well. The problem may simply be over-controlling, which if carried into the flare can cause all sorts of confusion.

 

A Thought on Short.

 


A short field landing is achieved by flying a standard approach at a slightly lower speed and achieving the desired touchdown point with precision. It is NOT achieved by a very low speed/high thrust undershoot approach, dropped onto the near end of the runway and followed by excessive braking. This latter technique has more holes in it than Swiss cheese as it doesn’t account for obstacles on approach, avail adequate thrust and airspeed to conduct a missed approach and runs a high risk of flat-spotting a tyre. And yet you will see it time and again.

 

Short field landings are more than ever about a stable approach, flown at a minimum safe margin speed over the stall. The standard approach perspective means that no major adjustments in technique are called for and those trees on final are not a threat. Aim point retention is doubly important as these approaches are generally necessitated by length critical airstrips. At a lower speed, there will be less energy to dissipate, so the landing flare is initiated a fraction later. This assists in achieving the aim point and avoiding an unwanted float down the runway. Fly the book figures as they appear in the Flight Manual and always verify the field length is adequate from the ‘P-Charts’. And check that adequate length exists to depart again before committing to a landing is always well advised.

 

Airmanship and Away!

 


In all landings, AVIATE-NAVIGATE-COMMUNICATE. In a tight traffic environment, don’t succumb to subtle pressure from ATC to expedite clearance of the runway. As an aviator, airmanship dictates that you won’t dawdle unnecessarily on the runway after landing. Jumping on the brakes and blowing a tyre or snapping a nose-gear won’t help anybody. You are the pilot in command, fly the aircraft to the best of your ability and if inadequate separation has been provided with the following aircraft then they can go-around. Similarly, these requests can be made as the aircraft is rolling out and should not be acknowledged unless the aircraft is well and truly decelerated and under control.

 

In all cases, on approach, in the flare, or after a bounce, if the pilot is not happy with the situation then conduct a missed approach. As the saying goes, “If in doubt. BUG OUT!” Generally, the earlier a poor situation is abandoned, the simpler the extraction. Time affords a more organised abandonment of the approach in an unrushed manner. For this reason, the go-around should be practised at various stages of the approach and landing throughout a pilot’s career. It is a manoeuvre that can be called for at any time and requires the correct sequence of actions and the management of trim that can prove awkward. A prudent, competent missed approach is a strong weapon in a pilot’s arsenal.

 

For all of the variables that the aircraft and environment can provide, it will always be impossible to detail them all in the written word. Similarly, nothing can substitute the positive input from a proficient instructor for both the student pilot and the qualified aviator who is lacking currency. What the 'Ground Rush' has sought to emphasise is the common traps that plague the landing phase and to reassure one and all that the landing is not the ‘make or break’ of a pilot.

 

The landing is merely the arrival at the end of a flight that has called for all manner of skills enroute. Highly rated and unfairly judged, the landing will continue to be the secret nemesis of many pilots. However, in its most basic components it is about being on speed, on aim point, on slope and aligned with the runway. When the ground rush is sensed and the earth moves up to meet the wheels, it is all about safety........finesse will come with time.

 

 

 

Missed the story so far?

CLICK HERE to begin 'Ground Rush' at PART ONE.

 

Ground Rush. (Part Three) Showing Some Flare. An Aviation Training Blog by Owen Zupp.

Owen Zupp - Sunday, June 24, 2012

 

Ground Rush. (Part 3)

 

 Showing Some Flare.

 

By Owen Zupp

 

 

As we saw in the last blog of ‘Ground Rush’, a good landing is often intrinsically linked to a good approach. An unrushed stable approach, flown in a consistent manner delivers the aircraft across the threshold in a positive state, ready to return to the earth. Even so, things can go awry. However, the good news is that the problem often lies with some sneaky repeat offenders that can be readily put in their place.

 

 

Was it really that bad?

 

Ultimately, a poor landing is merely the symptom of a root cause. Identify the problem and it can be fixed; no drama. So let’s not allow the dread of a bad landing crawl into our finite mind space and further erode our performance. Firstly, review why the landing was ‘bad’ in your opinion. If it was in the ball park of aim-point, airspeed, approach profile and runway alignment, then it’s quite possible it wasn’t really a bad landing. Perhaps the arrival was not subtle, BUT IT WAS SAFE!

 

If there were symptoms such as a bounce, a prolonged float or directional control issues on touchdown then we assess them for what they are and address the contributing factor or factors. Either way, there is no place or need for self-loathing or depression. If you drop the football, pick it up, move on and try a bit harder next time; you haven’t lost the game. Flying will always present challenges and in part, that is the fun. Very few are endowed with a mastery of any art, it is better in this business to be honest and consistent because that equates to safety. So let’s look at some of the culprits that endeavour to sneak under our guard as the wheels move to meet the runway.

 

 

On the Numbers.

 

At the optimum speed, the aircraft is endeavouring to arrive with a safe margin over the stall speed while touching down slow enough to minimise the ground roll and reduce wear on the undercarriage and airframe. Two of the most common complaints relate to long landings and hard landings. Often both can be traced back to the same issue of airspeed. Long landings can result from carrying excessive airspeed into the flare, whereas a hard landing can result when speed is on the low side.

 

 

 

Long landings can absorb copious amounts of runway very quickly. As an aircraft floats down the runway, the chance of an overrun is increased, while extra stress on the undercarriage and brakes often result as they are wrongly used to compensate for the wasted runway in the flare.  Airspeed above that recommended, or calculated for a given weight, equates to additional energy. The additional airflow over the wing results in the aerofoil continuing to provide lift when the task at hand is reduce lift and land the aircraft. This aircraft's resistance to landing can be further exacerbated by the thicker air immediate to the surface known as ‘ground effect’.  Furthermore, a higher airspeed results in more control responsiveness and that subtle flare manoeuvre may now result in the aircraft flying away from the runway.

 

At the other end of the spectrum, should we lose too much speed and energy in the flare, the aircraft, not you, will decide when it is going to land and gravity will play a far greater role than inertia. With low airspeed the controls can feel less responsive and the control column can seemingly be at its aft limit with nothing to left to offer in terms of elevator control. There is no flaring left to be done and the aircraft will simply arrive firmly on the runway; unless we have fortunately timed these events with such precision that they occur just as the wheels touch. Generally though, the aircraft will fall from its flare height to the surface with a thud, if not a bounce.

 

So speed is premium to maintain control effectiveness into the flare and achieve the anticipated responses from our inputs and achieve the desired landing performance. Again, a stable approach to land is one of the best means to the correct airspeed on entering the flare. Configure the aircraft to land and get used to the attitude and feel nice and early. Turbulent conditions and hot days will present a challenge as the airspeed needle flickers, but aim to keep a constant attitude out the front. As the runway looms near, most pilots sneak a ‘last look’ at the airspeed; just a glance, nothing more. Accordingly, the airspeed can be noted as high or low resulting in a slightly earlier reduction in thrust, or perhaps the need to carry it later into the flare to prevent the energy washing off totally.

 

And don’t underestimate that sixth sense in the flare. If it feels like your backside is falling out from under you, trust your instinct and increase the power to arrest the sink. Energy and speed are critical elements in landing, yet long and hard landings are not solely the fault of inadequate speed control. That would be too easy!

 

           Check back soon for Part Four of Ground Rush!

 

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