Collapses.
They earn an inordinate amount of attention from novice pilots, attention that has a flavouring of fear.
As previously discussed (see
'Fear Factor'), fear is a useful tool if harnessed correctly. It helps identify that which we do not yet understand.
Collapses, for the most part, are an angle of attack (AoA) issue. A low angle of attack can disrupt the airflow pressurizing the wing, causing some portion of the leading edge to fold. This fold, either span or chord wise, and loss of rigidity in the wing is the collapse. Collapses are not to be confused with stalls, the byproduct of too high an AoA.
Recovery from collapses may be automatic via design (as is expected of EN A and B wings) or may require pilot input (as is sometimes the case in EN C and D wings).
The identification, management, and recovery from collapses should only be learned under the guidance of a qualified instructor.
Collapses are important for the novice.
A collapse occurs because of an (in)action on the part of the pilot, allowing the wing to achieve an AoA that disrupts the airflow into it.
Knowing that the collapse is a byproduct of the pilot, the collapse can become a learning mechanism. Every collapse is the result of a mistake (though not every mistake results in a collapse). Accepting this means we can:
- Begin to dissect the situation that set up the collapse.
- Identify the sensations in the wing and harness just before and during the collapse.
- Test the results of our actions as we attempt to mitigate and resolve (and ultimately try to prevent) the collapse.
A case study from personal experience:
Early February. West Launch, Mt.Borah, Manilla, Australia.
The record setting rains had passed the week earlier, allowing the ground to finally dry out. The promise of a proper summer flying day in Australia. Upper winds were light from the west, the cloud base high and the air active. Heat collecting on the vast plain below launch was continuously rolling its way up and triggering off various points of this relatively flat top hill. What was affectionately known as 'idiot lift' was clearly abundant.
I had had a couple of great flights in the mild days preceding, being able to take advantage of being 15 kg under weight on my high end EN-B to hook the relatively weak thermals and climb out. One flight over the back had set a personal best in both distance and duration, so I was eager to get flying and push further.
Boating around to the WSW of launch, I find and hook a thermal. While in absolute terms the thermal was not particularly strong, my limited experience leaves me with the impression of being on an express elevator to low Earth orbit.
The elevator drifts back, over launch, to meet up with other elevators that had popped off along the flat top hill. The wing begins to move around in this mixing air. I decide this is getting a bit much, exit my climb and begin to push north.
Without warning the left side of the harness drops.
WHACK!
Any thought of pushing north is forgotten. I am now above and behind launch and have no desire of going back into that mixing pot to try for the bail out LZ. The campground LZ a few km's behind launch looks inviting. I turn towards it, failing to connect the dots that the thermal I am still in is connected to the cloud 3000m above said camp ground. Long story, short - I end up smashing my personal best distance wise, scratching out 20 km total from the altitude gained in that single thermal.
The earlier collapse? A distant memory.
Dissection.
The conditions:
Solar energy was no longer being wasted in drying out of the ground. All of this available energy when coupled with the high lapse rate made the air more active than previous days.
The wing:
A high end EN-B that was acquired in late summer the year prior. This new higher performance wing would react to the air much quicker than it's EN-A predecessor.
15 kg under max weight for this wing, meaning the wing would be less loaded and more prone to collapse.
The site:
The western side of Mt. Borah is more or less a table top ridge. Thermals from the valley below work their way up this ridge and trigger from a variety of points along the front of launch. This thermic air then churns as it combines until it settles into a new aggregate core extending to cloud base.
The pilot:
Novice rated with approximately 70 flights. Thermalling experience extremely limited with most active flying skills coming from a pair of SIV courses. Active flying technique limited to weight shift responses. Flying with basic toggle grip.
Action.
Following the trip, a number of changes were made.
- A wing with a lower upper weight range was acquired. The wing used during the trip was relegated to mild day use only.
- More attention was given to the employment of ballast.
- Basic toggle grip technique was replaced by use of a half wrap to better feel changes in wing pressure.
- Coaching was sought out to improve thermalling technique.
- Adjustment to flying style made to keep wing loaded in strong lift (open carve to leave lift rather than fly straight out).
- Better attention paid to changes in atmospheric conditions and the role of ground moisture.
Any significant collapse should be dissected afterwards to determine the causes and needed corrective actions moving forward. To simply brush the collapse off as a random occurrence out of our control is to waste a valuable learning experience.
Collapses should be unacceptable to the experienced.
Collapses away from terrain are a necessary part of learning to fly in thermic conditions. They teach us novices the boundaries of our judgement and skill. Knowing where these boundaries are means we can focus effort on correcting the issues that lead to a collapse in the first place and become more proficient pilots.
For an experienced pilot, on the other hand, a collapse should not be a welcome or even acceptable occurrence. The experienced pilot should already be in tune with their wing, knowledgable in both macro and micro meteorology, and be able to provide an honest self assessment of their current flying state. The experienced pilot should already know their boundaries and be working on increasing them in a controlled manner, as opposed to the floundering of the novice.
In the air the experienced pilot should have a sphere of awareness that extends well beyond their immediate world framed by the risers. The wider this sphere, the more information the pilot is able to process in adjusting their cross country flight to changing conditions. A collapse shrinks this sphere of awareness to the immediate problem at hand, distracting the pilot (not to mention the time and altitude lost). This distraction can linger and influence the pilots mindset for the remainder of the flight if the collapse is particularly energetic. Anything that can influence this mental state should not be underestimated as it plays a huge role in the success of a cross country flight. The fewer the distractions stealing mental capacity, the greater the sphere of awareness of the pilot and the more successful the flight.
