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Deutscher Hängegleiterverband e.V.

DHV

Safety checks on 16 paragliders from the LTF-A and B classes

 
Text: Karl Slezak
Videos: Reiner Brunn, Harry Buntz
Photos: Reiner Brunn, Björn Klaassen
Translation: Peter Wild

“Trust in Allah, but tie up your camels”. This Arabic proverb reminds us that even when we trust in God we shouldn't ignore our own common sense. For beginners and low-airtime pilots choosing a new glider is a delicate matter. It is well known that there are some big differences in the expectations of required pilot skill in the “appropriate” LTF-A and LTF-B classes. We wanted to know how large the differences really are, and how well current LTF-A and LTF-B gliders are suited to pilots who don't spend too much time in the air. For the test we chose 16 different glider models and tested them particularly in areas most accidents occur:  collapses, spiral dives and launching characteristics. In addition to this, we checked the use of big-ears and B-stalling for rapid descents. All flight tests were conducted by our DHV test pilots Harry Buntz and Reiner Brunn. Flights were filmed from the ground and with on-board Gopro cameras, and recorded (see the info box) using data loggers. Physicist and Systems Engineer Peter Wild worked as Technical administrator for the data loggers. Instructors Barbara Lacrouts, Ben Liebermeister, Björn Klaassen and Karl Slezak spent two days on a beginners slope and collected valuable information on the glider launching characteristics from approximately 200 starts.

Choosing the gliders
We wanted to investigate the complete bandwidth of the A and B classes, so in addition to pure LTF-A gliders we also chose both “low end” (as criteria we chose the manufacturers recommendation whether a glider should be used for schooling or not) and “high-end” LTF-B class gliders.

Info: data logger technology

Over the last two years the test pilots from the DHV have been testing the use of data loggers for the documentation of flight tests. The data loggers have been developed by a local engineering company together with DHV Systems Engineer Peter Wild.
The pilot data logger is firmly attached to a main suspension strap on the pilots harness.
A second smaller glider logger is attached to a cell wall inside the glider using two strong magnetic plates. The best position for data collection has been determined to be where the C-gallery lines are attached to the canopy at the 70% collapse marker points. Logger data is collected continually from the beginning to the end of the test flight and the two instruments are synchronized  with each other via a low-range radio signal. Data sets are transferred from standard micro-SD memory cards to a PC after landing.

The loggers collect the following information:
 Pitch, roll and yaw angle,
 Pitch roll and yaw acceleration,
 Vertical velocity calculated over a 0.5 second window from the barometric altitude sensor,
 Velocity: the pilot data logger contains a 5 Hz GPS, from which the velocity over ground is calculated,
 G-Force: from the accelerometers contained in the pilot data logger the G-force acting on the pilot is calculated,
 Altitude: both the barometric height (recorded at 100Hz) and the GPS height (5Hz) are recorded.

Data processing: the processing software is written to automatically recognize the beginning and end of a test manoeuver. Pilot and glider movements are simulated from the recorded data, and this simulation is synchronized with the video material of the test flight. Test pilots check the synchronized results for plausibility. Data loggers are instruments to assist test pilots and provide additional objective information on parameters which are difficult to judge in the air such as roll and pitch angles, height loss,  course changes and durations.

The data loggers mounted in the canopy and on the pilots harness are synchronized via short range radio signals
Data logger mount position in canopy

Launch preparations

We began our test series where all flights begin, with launch preparations. Ergonomic considerations where the machine (paraglider) should fit perfectly to the user (pilot) for a particular use (launching) quickly revealed large differences between the different models. Life can be simple, very simple, as revealed by the Skywalk Mescal3, Nova Prion and Paratech P12. These gliders have just a few solid lines organized in an easily understandable scheme together with soft upper gallery lines which don't tend to tangle with each other and clearly coloured and separated risers. Line checks are quickly made with a few gentle pulls and glances. On gliders where thin, unsheathed gallery lines are present (Nova Mentor 2, Swing Mistral 6, Ozone Rush 3, Gradient Golden 3, Skywalk Chili 2, Nova Ion Light) line checks become increasingly demanding. “Dental floss” lines not only require more optical attention, but also tend to tangle or get caught up in small obstacles more readily. Most demanding in this respect was the Ozone Rush 3, here unsheathed lines are present in the upper and middle galleries. Several unsheathed lines are also attached to the stabiliser and require careful checking for tangling before launching. In addition, the aramid lines used are relatively stiff and have a tendency to form loops and tangle with each other.

Other competing models use less of these race lines and mostly only in the upper gallery and upper brake gallery lines. Checking these lines for tangles is easier than the longer C/D lines which contact the ground.
Risers: thinly constructed risers (Nova Mentor 2, Swing Mistral 6, Ozone Rush 3, Gradient Golden 3)  receive ergonomic minus-points. Handling, particularly in bulky gloves is difficult. Real problems are present when the heavier line-mallions and brake handles begin to live a life of their own – these elements can quickly become twisted or cause the riser tapes to become tangled through the lines. It is important to re-check the rear riser for twisting on the Ozone Rush 3 and Nova Mentor 2: the long thin tape used here can easily turn unnoticed through 180° resulting in a brake line twist around it. The A riser to the outer lines on the Swing Mistral 6 is so short that it does not readily fit in a gloved hand – this was a source of irritation for our testers.

All tested LTF-A gliders had solid and well arranged risers with few differences in construction. Noteworthy in particular is the Nova Prion: individual colouring for each line set, and clear Big-Ears and B-stall labels to help reduce confusion.
Easy launch preparation is not as trivial as it might first seem. Every year we receive several accident and injury reports from pilots having launched with knotted or tangled lines. Every pilot must decide personally if “cool” race lines are really worth it, when considering the additional attention they require at start. The majority of low-airtime pilots will not profit from minimal gains in glide performance offered by race lines.

Line checking ease..
..and team discussion
High-end B risers are often thin...
...solid and clearly marked A-class risers
Ideal – riser labeling on Nova's Prion
Need careful attention: thin race lines on Ozone's Rush 3

Launch characteristics

Beginners and Low-airtime pilots are always happy when a glider starts without any “special effects”, but is it possible to define an ideal launch behavior for our typical weekend-warrior pilot? The answer is yes; the simpler the necessary coordination requirements are to get airborne the safer a glider is. Ideal characteristics are as follow: inflation occurs with minimal pilot input, and the canopy climbs at a moderate rate to its zenith. A healthy tension on the A-risers indicates to the pilot at what position in the climb the canopy is; to begin with the tension is high, and decreases progressively as the canopy climbs. Towards the end of the climb phase, the canopy slows of its own accord and settles nicely at the zenith. It is not necessary to prevent the canopy from overshooting through excessive use of the brakes.
Such a glider can be launched with minimal stress and gives the pilot the most important requirement for a safe start – time. Time to make a good control check, and time to make the take-off decision. The take-off run can then begin once these checks and decisions have occurred.
Most of the class A gliders tested by us displayed these characteristics. Our testers particularly liked the balanced behavior of the Skywalk Mescal 3, Niviuk Koyot and the Paratech P12.
Ozone's Mojo 3 was more difficult to start –  the canopy climbs slowly and the tension on the A-risers is low and does not provide good feedback to the pilot.

Gliders which climb rapidly and need a good block on the brakes to prevent them from overshooting require mode advanced coordinative skills to launch safely. This was the case with Ozone's Rush 3; particularly at steep launch sites, good reactions are required to keep the canopy under control at all times. The Nova Mentor 2, Skywalk Chili 2 and Golden 3 from Gradient were all somewhat tamer, but giving these gliders too much of an impulse or leaving your hands on the A-risers for a little too long would make them all clearly overshoot.
Dynamic launch characteristics are fun in the hands of experienced pilots, gaining the necessary coordinative skills requires training – particularly on steep launch sites. The impulse used to inflate the canopy must be in accordance with the steepness of the site and wind strength, and you have to develop a feeling for the right moment to let go of the A-risers. Timing the moment to block an overshooting canopy with the brakes, and getting the block-amount right are the next steps. If you have to use a lot of brake to block an overshooting canopy, then the next phase is quite tricky – knowing how much, and when to release the brakes to prevent from starting in a deep stall is critical. The brakes must be released moderately – abrupt movements here can cause the canopy to overshoot alarmingly.
From the accident reports we have received, it is clear that a gliders launch characteristics are a very important safety feature. The main cause of serious launch accidents – the canopy overshooting, collapsing and a resulting crash can be minimized by the choice of glider.

Videos launch characteristics

                                          

                                      delayed                                      balanced                                    dynamic
      

                                                   

          

 

All gliders were launched from gently sloping starts..
..and steep ones too.
Tester impressions were recorded immediately on landing
 

Flight stability

All pilots who payed attention to the flight-school theory lessons know that a paraglider is stabilized through the weight of the pilot hanging below it. The range of the canopy-pilot pendulum system differs greatly between differing models. Gliders which are designed to be pitch stable, dampen these movements and also dampen the effects of turbulence on the canopy. Dynamic gliders with less pitch stability react more aggressively to turbulence, and require the pilot to actively prevent them from diving forward in the air. Collapses which occur while a canopy is diving forward are generally serious events – gliders will turn and spin much faster when this occurs.
Through pitching and seeing how far a canopy dives forward, we have a measure of the potential dynamics of a  glider. Measurements were made after three pitching cycles.
                 

 

Processed data logger diagrams from the Paratech P12 (left) and Niviuk Hook 2 (right). Note the pitch curves on the P12 – in spite of relatively high pitch back (positive) values where the test pilot applies lots of brake, the glider does not dive far in front of the pilot (15° negative pitch). The Hook 2 is different – its dynamic handling is displayed by the high negative pitch values of over 60°. On the 3rd pitching amplitude the glider had to be blocked via the brakes to prevent a frontal collapse.

Asymmetric Collapses

Video example of an asymmetric collapse with data logger simulation

Imagine your glider collapsing asymmetrically just over the ground. Would you react correctly? Not just by using massive brake which might result in a full stall, but by letting the glider fly again, and catching the dive and spin with appropriate brake and weight-shift actions? If you are not sure of your answer, well, you are not alone; many, even experienced pilots often make mistakes in this situation. The main problem revealed in the accident statistics (see DHV 2010) is that pilots don't manage to stop the glider from turning or spinning because they don't react quickly enough, or don't react at all. Therefore it's very important to know what your glider does, when you don't do anything.
The DHV test pilots performed several (generally at least six) asymmetric collapses according to the LTF requirements both at trim-speed (brakes off) and full-speed (speed bar pushed to its limit) for every glider. Particular attention was taken to ensure that only collapses were judged which fulfilled the LTF requirements exactly. Here the canopy must be collapsed to within a clearly defined set of markings, and the trailing edge must also be completely affected by the collapse. With the data loggers accurate measurements of the canopy and pilots movements were recorded, which is more than the requirements defined in the LTF norm.

 

                                                     

Figure: the red lines indicate where the canopy is to be marked. On the right are minimum and maximum markings for the large 75% test collapse, going through to the trailing edge. On the left, the 50% collapse line.

 

                                                     

                                                                 

 

Figure: schematic of an LTF-norm collapse. The collapse should fold according to the markings on the canopy, and must deform from the leading edge through to the trailing edge. Collapses which do not fold along the marked lines do not usually include the trailing edge of the canopy. Such collapses are  associated with less dynamic reactions and would falsify judgment if used in certification tests.

Asymmetric collapse table information

Height loss in meters: the entire height loss from the beginning of the collapse until stable normal flight was regained is given.
Pitch angle in degrees: the maximum angle the canopy dived to after collapsing is given.
Pitch change rate in degrees per second: processing the pitch angels and time signals provides us with this result. Higher values of pitch change rate indicate dynamic gliders, lower values show more dampened canopies.
G-Force in G: measured at the pilot. In stable straight flight 1G (gravitational pull of the earth) acts on the pilot. Dives and spins induced by asymmetric collapses accelerate the pilot and increase the acting forces. At 2G the pilot feels twice the gravitational pull of the earth and is “pressed” with twice the weight into the harness.
Course change angle: the total angle through which the glider turns from the beginning of the collapse until stable normal flight is regained is given.
V/sink max. in m/s: the maximum recorded sink velocity in m/s is given.



Collapse testing: size is what matters

From accident investigations we know that it's almost always big asymmetric collapses that lead to accidents. The sudden loss of a large part of the canopy right back to, and including the trailing edge generates the maximum in dynamic reactions from a glider. If the trailing edge remains unaffected by the collapse then reactions are usually much less dynamic.
For this reason, the LTF testing norm defines that the canopy must be collapsed to within the measurement field including the trailing edge, before the manoeuvre can be rated.

 

This collapse with the Mentor 2 is well within the measurement field and clearly shows trailing edge deformation.
This collapse on the Hook 2 is too small. The measurement field has not been reached, and the trailing edge is not deformed.

Asymmetric Collapse LTF A

 

Asymmetric Collapse LTF B Low Level

Asymmetric Collapse LTF B High Level

Summary: asymmetric collapses

LTF-A glider collapse..
..with severe dynamic overshooting.
LTF-norm collapses within the measurement field are possible without folding lines on the Rush 3...
...but the glider can collapse with very large folding angles.
The greater the folding line on a collpase, the larger the chances are that the stabilizer will tangle in the lines...
... and cause a cravat.
Initial inflation of the Chili 3 outer wing...
..may sometimes end in a tangle and cravat.
This is also true for the Mentor2 when collapsed to the maximum limit.
 

We were excited to see if the results from the data loggers would back up the opinions of the test pilots and video analysis. The first surprises were the relatively large pitch angles recorded when the glider dive forward after the initial collapse. According to the LTF norm, class A and B gliders should not dive forward more than 45°. Only a few of the tested gliders managed to roughly remain within this limit. Many of the LTF-B gliders had much greater recorded pitch values, some in excess of 60°. An explanation for these discrepancies are that during testing the pitch angles can only be roughly judged by the test pilots and from video material. Here there are no fixed reference points, hence the results are likely to have large margins of error.
In the tables above, the recorded angles give a good indication of whether a glider reacts moderately or dynamically to a collapse:
Large negative pitch angle – fast pitch change rate – high G-force – high V/sink => large height loss
Small negative pitch angle - slow pitch change rates – low G-force – low V/sink => moderate height loss
From the tests with the gliders in the table we note:
The friendliest LTF-A gliders Paratech P12, Gradient Bright 4 and Skywalk Mescal 3 all need about 30m to regain normal flight after a norm asymmetric collapse. The Nova Prion was a little more dynamic. Niviuk Koyot and Ozone Mojo 3 required almost twice as much height to recover and recorded significantly higher sink velocities. Such a bandwidth under class A gliders is unwanted. In the safest glider class possible, pilots ought to be able to expect the maximum in technically possible passive safety from their gliders. Reactions to asymmetric collapses range from “manageable” to “unexpectedly dynamic”. On the positive side, none of the tested gliders showed any particularly undesirable tendencies (e.g. to cravat after collapsing or similar).

Under the LTF-B gliders the differences were, as expected, greater. Low-end gliders Paratech P28 and Swing Arcus 6 were almost identical to the LTF A models. Others were somewhat more dynamic, but all within acceptable limits.
Under the high-end LTF-B gliders things are different: the bandwidth here, of possible reactions to a collapse is much greater. All gliders demonstrated reactions applicable to the test norm for some   collapses, but could also react far more dynamically on occasion. The Skywalk Chili 2 collapses particularly softly and unremarkably. On recovery the outer part of the collapsed wing inflates first, which occasionally lead to a cravat. The Nova Mentor generally reacts very well to collapses of all sizes, but again can react particularly dynamically on occasion. Large collapses, on the outer limit of the norm measurement field can lead to cravats, and require active recovery from the pilot to prevent entering a spiral dive. Cravats, generally the “worst case scenario” for hobby pilots occurred on Ozone's Rush 3 when collapsed massively. This glider passed the LTF tests with folding lines attached to the front of the canopy, and reacts more dynamically to collapses induced via the A-risers. We note here critically, that folding lines are not necessary to collapse the glider according to the LTF-norm. The Niviuk Hook 2 was particularly dynamic, with fast rotations, high sink velocities and large height losses of approximately 70m after collapsing.
Some of the gliders found in the high-end B sector clearly have the potential to expect too much from a hobby pilot. It is evident that the line between “appropriate behavior according to the norm” and “not certifiable” is very thin in some instances.

Frontal collapses

Accident statistics indicate that frontal collapses are not as dangerous as asymmetric ones, but are on the increase in recent years. Reports of the entire canopy folding in are not seldom. The LTF norm can be interpreted such that frontal collapses only need to fold over  40% of the canopy. For our tests, we particularly wanted to see what happened when as much of the canopy as possible was folded. All gliders with the exception of the Paratech P12 (designed for stability) could be collapsed with such a “destroyer”.

 

This is what can happen in reality: frontal collapse along the entire leading edge on a Nova Ion due to turbulence. (Click picture for video link). Source: Youtube
Video example of an frontal collapse with data logger simulation.

Frontal Collapse LTF A

Frontal Collapse LTF B (Low Level)

 

Frontal Collapse LTF B (High Level)

Summary: frontal collapses

Nova Mentor 2 significant middle deformation tendencies..
..occasionally with tangles and cravats.
Niviuk Hook2 front horseshoe with rotation
Care should be taken with brake input in this phase of the recovery: both ears are still collapsed, and from the trailing edge we see the glider is in deep stall. Ozone's Mojo 3 with delayed recovery from a frontal collapse.

From accident investigations we know there are two main problems when dealing with frontal collapses: if a glider recovers very slowly, often combined with collapsed ears then should the pilot apply brake at the wrong moment, this can lead to a full stall. If pilots attempt to open the collapsed ears by applying symmetric brake before the glider has regained sufficient airspeed, then this may result in a full stall with all its consequences and height loss. For such gliders it is particularly important to adhere to the approved school of thought: “hands up” until the glider has regained normal airspeed.
Another problem which is becoming more evident with the popularity of higher aspect ratio gliders, is the tendency of a canopy to deform in the middle “horseshoe” after a frontal collapse. Re-inflation often occurs asymmetrically, and the collapsed part of the canopy may then hang in the lines or cravat. It is often not possible to stop the following rotation without resorting to a stall. These characteristics are nothing new, but are often not revealed though the LTF norm tests, especially when the tests are conducted at the minimum folding limit. Advanced pilot skills are required to deal with such situations: a short jab on the brakes is required at the right moment to prevent the glider entering a horseshoe. Woe is in store for the pilot who stays on the brakes for too long – the canopy is prevented from regaining airspeed and can directly enter a full stall.
In our tests the Niviuk Hook 2 demonstrated a tendency to horseshoe, combined with fast rotation speeds and a danger of twisting.
“Normal-speed symmetric recovery” from a massive frontal collapse as demonstrated by e.g. Nova Ion Light and Prion, Skywalk Mescal 3 and Gradient 4, are the least challenging for the hobby-pilot. A significantly delayed recovery, or the tendency to horseshoe require much better pilot skills to manage safely, and are always associated with greater loss of height.

Spiral dives

Video example of a spiral dive with data logger simulation. (click on picture).

Serious injuries and fatalities from spiral dives are one of the biggest safety problems in paragliding. Glider characteristics are one area which needs to be addressed, but for many pilots the far greater danger comes from the unexpected forces acting on ones body. Most spiral dive accidents result from pilots loosing consciousness or blacking out due to the high G-forces experienced. A big step in paragliding safety could be made if untrained pilots simply avoided this manoeuvre.

Spiral dives are subject to constant and repeated discussion at the LTF and EN working group meetings. No other manoeuvre can be so easily manipulated by the actions of the test pilot; different entry speeds or slight weight shifting from the neutral position can make for big differences in the test outcome.
To date, paragliders are tested to sink velocities of max. 14m/s under the LTF norm. In future, the recovery behavior of the glider after a spiral rotation of 720° will also be judged. Most gliders have significantly higher sink velocities at this point.
We followed these plans in our tests, so the results are not directly comparable with the current LTF tests.
Two turns at maximum speed in the spiral and then “hands up” to see what happens – requirements on gliders (and test pilots) are tough. Results show that the normally “friendly” gliders can react particularly differently under these conditions – some gliders reacted with further acceleration and only a very gradual recovery to normal flight on their own. It is known that compact low aspect ratio glider designs are often more associated with recovery problems than higher aspect ratio gliders.
The recorded datasets from our loggers provided interesting information after processing. For example, the rate at which rotation speeds and sink velocities increase gives a clear indication of the dynamics present in the manoeuvre. High sink velocities attained in short periods of time are typical for gliders which quickly begin to dive. Gliders which enter the spiral more moderately can be identified with the lower build up of sink velocities. The rightly feared “dive point” in a spiral, where the canopy suddenly begins to markedly accelerate can also be clearly identified in the data. Datasets show an abrupt increase in sink and rotation velocities between the first and second turn.
G-forces are usually greater than 3.5G in a massive spiral dive. According to medical studies (see under  dhv.de), forces such as these are border-line for untrained pilots and can lead to blackouts or loss of consciousness. Experiences made at the G-force training station also validate this. Some gliders reached even higher G-forces, top was the Swing Mistral 6, with 5.5G at 27m/s sink velocity. As a side note: the length of a gliders lines also play a role in the G-force felt by the pilot: short line gliders do not develop as much G-force.

Things usually work out well, as long as the ground is far away enough, as we found in our tests. The Sing Mistral 6 was the only glider which entered a stable spiral dive and required active pilot reactions to recover from it. All the other tested gliders recovered (some only after severe height loss) on their own. Further evidence, that spiral dives should only be conducted with sufficient height reserves.

Spiral dive LTF A

Spiral dive LTF B (Low Level)

Spiral dive LTF B (High Level)

B-Line stalls

Video example of a B-stall with data logger simulation. (click on picture).

Many experienced pilots do not think highly of B-line stalls as a descent method. However, in the LTF-A and B classes, clean glider behavior in a B-stall is very important. For pilots who are not confident in flying spirals over prolonged periods, the B-stall is an important alternative in an emergency. “Good behavior” in respect to B-stalls is defined as follows: the B-risers should be clearly marked to help prevent danger of confusion, the force required to hold the stall should be moderate, sink velocities should be significantly higher than those in a big-ears descent, the canopy should not deform or horseshoe while in the B-stall and recovery should occur with no deep or parachutal stall phase.

In our tests, B-stall of over 10 seconds were performed. This is important to identify if a canopy has a deformation or horseshoe tendency – LTF tests are often kept far too short.
Data loggers recorded how far back the glider pitched on entering the B-stall, and how far forward it dived on recover. In addition the sink velocity and height required for recovery was recorded.

B-Line-Stall LTF A

 

B-Line-Stall LTF B (Low Level)

B-Line-Stall LTF B (High Level)

Summary: B-Line stall

All LTF-A class gliders left good impressions in the B-stall tests. Longer B-stalls were possible without problems. The higher a gliders aspect ratio is, the more difficult it becomes to keep it in a stable B-stall.  Some of the LTF-B gliders had significant deformation tendencies. If a deformation remains unnoticed and is not recovered from in time it can lead to a cravat. Reducing the length of travel on the B-risers as done on the Swing Mistral 6 can be a method of reducing the deformation tendency. Under a normal recovery procedure (rapid controlled release of the B-risers) none of the test gliders showed a tendency to enter deep or parachutal stalls. The Swing Arcus 6 was the only glider which had a somewhat delayed recovery to normal flight.
Accidents often occur with this manoeuvre when mostly inexperienced pilots pull the wrong risers on entry. For this reason it is important that the risers are clearly marked to help prevent confusion. The Nova Prius has clear coloured and marked risers – other gliders rely only on a colouring scheme.

Big-ears

Swing Arcus 6
Gradient Bright 4
Skywalk Chili 2
Niviuk Hook 2
Nova Ion Light
Niviuk Koyot
Nova Mentor 2
Skywalk Mescal 3
Swing Mistral 6
Ozone Mojo 2
Paratech P 12
Paratech P 28
Nova Prion
Ozone Rush 3
Skywalk Tequila 3

Big-ears is probably the most important descent method for hobby pilots. Her we don't suffer from high G-forces as in a spiral dive, or have to control a glider in a B-stall . While descending with big-ears the glider still flies forwards – and this is often just as, or more important than the descent itself. Via weight-shifting, directional control is possible at all times. This manoeuvre must be simple and safe for all beginners and low-airtime pilots: simple entry, easy to maintain over prolonged periods, the canopy should remain stable and not thrash around, the sink rate should be effective and exiting should occur without any further problems. In addition, no deep stall tendencies should be apparent when flying this manoeuvre.
None of the tested gliders had real problems with this manoeuvre. Differences were noted in the maximum sink velocities. Most gliders sank at around 2.5m/s when flown at trim speed. Both Nova gliders, the Prion and Ion Light sank at about 3.5 m/s; these gliders only have two main A lines, and so the reduction in area on big-ears is greater than by other gliders with 3 main A-lines. Once the gliders were accelerated to full speed with the speedbar, the faster gliders also had the highest sink velocities.
Top was the Nova Mentor with 5,5m/s, the rest in the B class reached sink values between 4 – 4.5 m/s. A class gliders were between 3-3.5 m/s – top here was the Nova Prion at 4 m/s.

Flying with big-ears naturally reduces the gliders airspeed. The additional drag causes a reduction of between 5-8 m/s in airspeed, depending on how much area has been folded. Pushing the speedbar to its limit brings the LTF-A gliders back to their normal trim speed, LTF-B gliders fly between 5-10 km/h faster than trim.

None of the gliders showed a tendency to enter a deep or parachutal stall. At full speed, the Niviuk Hook 2 tended to thrash a little, all other gliders remained stable.
All gliders have separate A-risers for entering big-ears, but even in the A class, not all gliders had clear labeling or colouring on these risers. Nova and Skywalk have taken the worries of flying schools to heart, and help to reduce the danger of confusion by clearly marking the big-ears risers.

Conclusions

The test series conducted here clearly supports the general suspicions regarding LTF and EN testing: the norms are at best a coarse sieve – large discrepancies are quickly found, but smaller ones may find their way through. We haven't found any really dangerous gliders in the A and B classes, but it is somewhat frightening to see gliders tested to be as safe as possible, that still require 60m of height to recover from a massive collapse. In doing so they pitch forward alarmingly, rotate through almost 360° and have sink velocities of over 20 m/s. This is not the kind of glider that belongs in the hands of a beginner. Accident investigations clearly show what beginner and low-airtime pilots tend to do in the event of a collapse – nothing! They are usually much too frightened and inexperienced to calmly and coordinately react in the heat of the moment. What they need in such a moment, irrespective of the piloting errors they may have made beforehand, is a particularly friendly glider with moderate reactions. This is often promised for the LTF-A class, but these promises are not always kept.

The performance gliders in the high-end B class are marketed, quite correctly, as cross-country machines. They belong in the hands of experienced pilots and are definitely not for “Sunday” flyers. The thin line between “just OK” and “clearly over-demanding” regarding what pilot skills are required to recover from instability provide a lot of food-for-thought. A slightly steeper folding angle on an asymmetric collapse, a bit more of the span on a frontal collapse or a little more sink in a spiral can change a moderate glider into one that's hard to recognise again. Between “typical behavior for its class”, and cravats, dives or stable spirals lies very little margin for error in some cases. Gliders in this segment are only for pilots capable of active flying, able to recognise the onset of instability and react immediately to prevent collapsing.

The general impression we were left with is that more intensive testing is required, and not just two norm flight tests for certification. To provide realistic judgments on glider characteristics, a test program with several collapses, stalls and dives is necessary. Only then can we determine the entire testing results bandwidth and inform pilots appropriately.

We often hear of the evil surprises that some gliders provide in extreme situations, such as the fatal crash last season of a school pilot after an asymmetric collapse, cravat and spiral dive into rocks. Or the pilot with 20 years experience who moved up to a high-end B glider and dies after not being able to exit from a spiral dive.

To simply write off these incidents as “pilot error, bad luck” does not do them justice. Paragliders are built for pilots, and pilots do make mistakes. In glider classes for beginners and low-airtime pilots  passive safety characteristics must have utmost priority. And there we still have plenty of room for improvement.