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Gradient / Aspen 2

1.  Summary
2.  Daily Notes

by Jérôme Daoust.  Revised 2006/7/7


Summary (Top of Page)

 

 

This section is a summary of my experience, some of which are further described in the Daily Notes (more pictures there too).

 

Thanks to Gradient (company profile) and Patagonia Paragliding (USA distributor) for providing the wing for this review.

 

Conditions

·        Total airtime:  2 hours, as of 2006/2/4.

·        Model flown, 28, has a 90 to 115 kg weight range.  My total flying weight is 225.2 lb (102.2 kg) (49% into the weight range) where 51.2 lb (23.2 kg) for equipment.

·        See Daily Notes for flying conditions and more detailed notes.

·        The harness used is a Sup'Air / Profeel XC 2, and a chest strap set at minimum length (maximum relaxation, sufficient feedback and weight shift to my taste).

 

User's Manual:

·        English: Download (Thanks to Nebojsa Rosic for scanning his).

 

Construction

·        Design is by Vaclav Sykora.

·        Overall: After spending some time examining details I am left with an impression of high quality design, materials and fabrication.

·        Lines.

o       Many colors were used to differentiate their purpose.

o       The lines connected to the wing are unsheathed (Picture), and have a slippery waxy feel like those on the Zoom Race.  This is similar to the Nova/Aeron setup, but the length of unsheathed lines seems longer here (to be verified).

o       Gradient: A new generation of Edelrid lines is used, the 7443 series.

o       Nebojsa Rosic, 2006/3/4: Measured the length of the final brake line (from lower fork to toggle) on his Aspen 28 to be 227.5 cm.

·        Risers.

o       The riser ends have color tabs to differentiate them. Picture.

o       They seem to be of average width: Not the narrowest I have seen.

o       Triangular quick-links and O-rings (almost a standard today) are used to attach the lines. No rigid plastic inserts for you to loose.

o       The brake line pulley is offset with a side webbing, for better alignment with hands to the side of the risers.

o       For those who like to separate the harness after a flight (I don't):

§         A riser bag is provided, with cinch cord. Picture.

§         There is a snap to hold the risers together. Picture.

·        Accelerator system.

o       3:1 ratio pulley system, achieved with 2 pullies.

o       Line travel is 31 cm (Reference: Nova/Tattoo has 33 cm).

o       Sliding C risers.

o       All-metal pulleys seem sturdy. Picture.

o       Hefty riser accelerator line.

o       An extra pair of Brummel hooks is supplied (to attach the lines going to the harness). Picture (look for small plastic bag).

o       No speedbar supplied.

·        Transport bag (Rucksack).

o       Too small:

§         Its circumference (girth) needs at least another 10 cm (+15 cm ideally) so I can fit the wing and my Sup'Air / Profeel XC2 harness.

§         Unusable helmet pouch. When tightly filling the main container, my helmet cannot fit in the external pouch as its outer skin is under too much tension to expand and allow helmet insertion.

o       A handle on each side of the bag. Good idea.

o       The waist strap can be removed and prevented from sliding in its sleeve by Velcro.  I like this, as I rarely hike, so i prefer take it off for car transport and reduced in-flight storage bulk.

·        Brake toggles. Picture.

o       Good: They are held to the risers with mechanical (Not magnetic which I dislike) snaps.

o       A semi-rigid base will allow me to use them "bus-style", and should be soft enough for those who like to pass their hands through them.

·        Wing.

o       Serial number: 917282601001.

o       No certification placard on the wing.

§         2006/2/8 update: Ondrej Dupal says this wing is pre-production.

o       Flat shape & color pattern: Underside and Topside pictures.

o       Leading edge opening pattern: Center and Tip pictures. The openings near the tip are meshed.

o       At the leading edge, there is reinforcement material. Single layer on cell walls without a load line, double and tapered (nice !) on load bearing walls. Picture.

o       Wing tips have a straight edge and use micro attachment points. Internal tabs distribute the load. Picture.

o       Gradient: A combination of Porcher Marine Skytex S 9092 water repellent (45g/m2) for the upper sail and Porcher Marine Skytex S 9017 (40g/m2) for the lower surface. The ribs are of Porcher Marine Skytex.

o       A thin fabric inner bag is provided for those who like to slip their wing into something more comfortable (than the rucksack) after the flight. Picture.

o       No apparent damage to lines (or wing) after the induced accelerated frontals (2) and asymmetric collapse (1). Good.

o       There are tension straps running spanwise between the line attachment points pulling against each other. Picture (see the one under the black dot, and there is another).

o       Left wing tip dimple/wrinkle:

§         From this picture, a qualified observer said: The wing you tried seems to have a bad wrinkle on the left wingtip (maybe too short middle fork line on B, or a badly sewn diagonal).

§         2006/2/5 update: I searched for a knot, and did not find one. This does not mean there was none when the picture was taken. Remaining possibilities: There was a knot at the time, internal construction problem, line length problem.

§         2006/2/6 update #1: Probable explanation (disproved below). I believe this picture was taken as I did my first (unintentional) launch. I noticed I had my left brake line wrapped around another line but waited until I cleared the mountain before unwrapping the brake line. There is a high probability that it caused the dimple shown in the picture taken at that time.

§         2006/2/6 update #2: I was almost satisfied with the above probable explanation, but then I though: How much time after launching was that picture taken? I know I cleared the brake line within 10-15 seconds after launching. Going back to the picture of the one taken shortly after launch and the one showing the wing tip dimple, there is a 4 minute time difference. This is proven by the last information lines under each picture in this image. So… I am now sure that the wing tip dimple/wrinkle was NOT caused by the improper brake line routing I had shortly after the first launch.

§         2006/2/7 update: Having the risers held together, I compared the symmetry of the lengths to the line attachment points on the wing's 3 supporting cell walls closest to the tips. Symmetry was good. Remaining possibilities:

Ø      Knot in lines at the time of the picture. Cannot turn back the clock to clarify.

Ø      Bad wing construction. Professional examination can clarify this. I tried to look inside but the meshed openings near the tips and no clear visual path leaves me inconclusive.

Ø      Bad line lengths to the tips, although length symmetry was proven good for this wing.

Ø      The dimple is normal. This can be resolved by the designer, by observing other wings, or by observing right wing tip (but must return the wing now).

§         Olivier Georis, 2006/2/26: When my friend was kitting it at the take off, we could have a look on the surface finish of the wing. Nice. I paid particular attention to the possible “wrinkle” observed on Jerome’s wing. Not even a trace. Nothing. Tips were clean.

o       Robustness. Good: No line or apparent wing damage following Collapse recovery tests. Accelerated frontals can cause damage (I have witnessed this in the past).

 

Launching

·        Behavior. Picture

o       Launching is easy, but the very long brake travel makes it difficult to prevent the wing from lifting you off. My first flight was not intentional as I launched despite my efforts not to, but full brake travel still allowed the wing to perform enough to lift me off, then I had to release braking to avoid being close to a stall once lifted. See also: Gradient info - Demo wing had brakes too long.

o       Wing has much lifting power on launch, reminding me of an Omega 4 (140 hours on that one).

·        Kiting.

o       Wing is easy to kite. The long brake travel reminds me of a beginner wing.

§         Update 2006/2/8: See Gradient info - Demo wing had brakes too long.

 

Landing

·        Flare. Picture

o       Possible without taking a wrap of the brake lines, but to rapidly bring the wing down after touchdown you may want to do so.

§         Update 2006/2/8: See Gradient info - Demo wing had brakes too long.

 

In flight

·        Collapse recovery. 

o       Size 28 DHV Test report.

o       Why I test fully accelerated collapses: Because they are likely to happen in XC flights (full speedbar transitions). Better to know what is likely to be experienced later, and note the behavior when you expect the collapse. The goal of this testing is to prove to myself twice that the wing behaves as desired (see criterions below). In the event of undesired behavior, I do not keep re-testing as it then become a statistical study which I am not paid to take risks for, so the burden shifts to the general pilot population and I wait for a consensus to emerge. I do not test Stalls or Spins because they are unlikely to happen and are normally only pilot-induced. Related discussions:

§         ParaglidingForum: Limit yourself to 1/2 speedbar ?

§         ParaglidingForum: How can you become comfortable going at full speedbar ?

o       My criterions for accelerated collapse (frontal + asymmetric) recovery acceptance (independent from AFNOR, CEN or DHV):

§         Recovery should be near automatic (minimal pilot input required).

§         The wing must remain above the pilot (not dive below him).

§         The goal is for an experienced pilot to feel comfortable with recovery from this type of event.

o       Fully accelerated full frontal. Acceptable (but with no margin, as input felt required in both cases).

§         1st time. Wing shot back (with respect to pilot) which is normal, then stabilized overhead where it had regained its span-wise dimension but remained crumpled chord-wise. It stayed that way for maybe 2+ seconds in an apparent parachutal phase, which made me want to give a tap on the brakes, to stretch it chord-wise. Not sure if that was the best idea in retrospect as it could have put me into a full stall, but I was lucky and the wing behaved as I had hope, regaining a better shape and then surging forward at about 45° to regain its normal flight mode. Pulling on the A risers would have been the better recovery technique in my view, but there is an interesting comment from the manual supporting the recovery method I used:

Section 5.3.3. Deep Stall: Recovery: … you may accelerate the recovery of the glider by one of two methods: Either you can pull both brakes intensely followed by a fast release of brakes or you can pull on the A-risers lightly.

§         2nd time (wanting confirmation). Wing shot back (with respect to pilot) which is normal, then stabilized overhead as a horseshoe (a common occurrence). Braking was used to open the horseshoe. A strong surge followed and normal flight resumed.

§         Other experiences:

Pilot Name

Expertise

Claim of impartial observer

Comments

Simon Foley

Average

No affiliation with Gradient

Source. I did a very big frontal (from trim speed, not accelerated). Interestingly, the wing went parachutal. I pulled the risers down quick and hard to get the collapse and thought I had let go immediately - maybe I paused but I cannot remember it. The parachutal stall saw the wing tips folded under which meant I did not want to tap the A's to get it flying again. A quick, quick jab on the brakes got it going without any other problems. It was a very big frontal and easy to get out but a pilot would need to recognize the parachutal stall.

 

Top South Africa pilot

 

Charles Swart writes (Source): In February one of the most experienced cross country pilots in South Africa (343km on a DHV2, numerous 200km +'s, two Aspen 1's flown to +-300hrs each etc. etc.), had an incident on an Aspen2. We where flying a competition task in Porterville, the first section being a basic 25 km ridge height speed run (full speed bar). Shortly after turning to start the run back, eye witnesses saw the pilot, in quick succession, suffer a frontal collapse, recovery, a stall followed by a partial recovery resulting into a sharp dive turn into the side of the mountain. Luckily the pilot survived with only a compound elbow fracture, a fractured pelvis and concussion. As we discussed our friend's incident that evening, the one thing that puzzled us was the stall in the sequence of events. Could this have been the result of a parachutal combined with too much brake input? Also the excessive diving as reported in your review, now start to form a pattern. Unfortunately the pilot has no memory of the event, and he is the only one that would be able to tell us exactly what went wrong. The pilot does not blame the wing at all and is still flying it on a regular basis.

 

 

 

 

o       Fully accelerated asymmetric on right side. Unacceptable.

§         1st time. From max speed (maybe 1cm shy of pulley contact) in what seemed like a calm air zone during a thermal day, pulled right the A riser down. Right side shot back (with respect to pilot) which is normal. Rapid and deep dive to collapsed side (right): Change of course of about 135°. Wing dove below me (unacceptable) at about 110° from its vertical position. Lines went slack as I fell towards the wing. Camera on my cockpit traded paint with my right red carabiner as my rolled body was tossed back when risers re-loaded. Normal flight resumed after some oscillations.
Update: I do not believe the "bad wrinkle" in the left wing tip (picture) is the main cause. I am more likely to believe a combination of bad air during the recovery can have contributed to this wild ride. I may re-test later this year, if there is a consensus amongst pilots that recovery from this maneuver is not as radical as what I experienced.

§         2nd time. There was no 2nd time, for the reason described above under "Why I test fully accelerated collapses".

§         Perspective: The event I experienced should only be seen as only one data point of experience. More input from independent pilots testing this same maneuver can be collected here. The goal is to have a consensus that the wing is not likely to dive below the pilot. Simply send me your name, claim your expertise, impartial observer status, and report your experience which can be added here:

Pilot Name

Expertise

Claim of impartial observer

Comments

Jérôme Daoust

Experienced

No affiliation with Gradient

2006/2/4. One test. Wing dove below pilot and risers went slack. Best effort was made to use a calm air zone within a thermic flight, but unexpected active air could have aggravated the recovery. Maybe it still qualifies as a simulation of real conditions (air is not smooth when you get a collapse).

DHV pilot

Highest

Independent study group.

Wing rated as DHV 2 (different criterions than mine). Testing is done in calm air, which is not when one can expect a collapse. A DHV 2 rating does not imply a maximum pitch/roll angle from vertical (unlike DHV 1-2 wings which are limited to 45°).

Dimitri Roman

Experienced

No affiliation with Gradient.

Pilot said: I didn't think it was such a collapse, I hardly noticed it. The wing just reopened fast and didn't turn or hardly. Obviously I released the bar at that time, just to push it again seconds later. Source.

 

 

 

 

·        Sharp input.

o       To simulate a rapid course change (thermalling core offset or pilot avoidance), I tried to get a feel for a Spin. I made a few rapid stabs of brake with lots of amplitude. Wing responded normally without initiating a spin, or deforming back that half of the wing. Good behavior.

·        Stability.

o       Rate of collapse:

§         Frontal collapse: 0 in first 2 hours airtime.

§         Asymmetric collapse: 2 small 20% in first 2 hours airtime.

o       In flight, the wing supplies more roll feedback than average.

·        Thermalling. 

o       Agility.  Defined as the ability to ease to stay in sharp-edged lift that wants to push you out its side.  Low agility may force a pilot to explore the limit of brake pull prior to inducing a spin.  My scale of 0 to 10 :

§         0 for an Apco/Presta M at the bottom of its weight range.

§         4 for a Nova/Artax.

§         5 for a Nova/Aeron

§         6 for a Nova/Mamboo or Apco/Lambada.

§         8 for an Advance/Omega 6.

§         10 for an Advance/Omega 4 or Nova/Tattoo.

I rate this wing as a To-be-determined (needs re-test).

§         Initial impression (2006/2/4): Long brake travel (with light line tension), which makes this wing feel almost like a beginner wing. But given enough input (almost full travel) the wing can achieve rapid turn changes. Notice the amount of brake pull I used in this picture for normal thermalling.

§         Update 2006/2/8: See Gradient info - Demo wing had brakes too long.

o       Efficiency. Sink rate in turns seems very good. Turn quality is good (no dive following turn input changes).

o       Pitch stability.  Wing significantly pitches back upon thermal entry.

o       Compared to:

§         Axis/Venus (2005 AFNOR performance, Para2000 info). In a late afternoon smooth wide thermal, both these wings seem to exhibit a similar performance.

·        Performance (straight-line).

o       Airspeed, corrected to sea level, with 50% into weight range, at 15º C (59º F). See Daily Notes for details.

§         Trim: 37 km/h. (same as Nova/Tattoo C with unsheathed lines).

§         Max: 56 km/h. (3 km/h more than Nova/Tattoo C with unsheathed lines).

o       Sink rate. Seems good.

o       Energy retention. Low, as there is little height gain following a turn. Yet, this wing nicely does wing-overs.

 

Conclusion

·        Rating the highlights, prioritized by value (first row):

Value

0 = Don't care

10 = Very important

Rating

0 is very bad

5 neutral

10 excellent

Criterion

Extra Comments.

10

1/10

See Collapse recovery.

Frontals were acceptable (2 performed) but input was required to recover.

One unacceptable asymmetric recovery: Wing dove below pilot. See details in Collapse recovery.

9

9/10

High L/D at trim and accelerated.

Seems excellent, needs in-flight comparisons to give max rating.

8

9/10

Efficient at thermalling.

Performance is high. Low energy retention influence is debatable.

8

9/10

Low sink rate.

Seems excellent, needs in-flight comparisons to give max rating.

8

10/10

Construction quality.

Excellent: Looking close at details conveys high quality design and manufacturing . Robust: No damage following 3 induced accelerated collapses.

7

10/10

High max speed.

56 km/h at sea level, or 62 km/h at 1525 m (5000').

4

Needs re-evaluation

Pleasure of crisp handling.

Low responsiveness to brake input, but tension is light.

Update 2006/2/8: See Gradient info - Demo wing had brakes too long.

4

8/10

Higher possible if re-evaluated

Launching/Landing

Easy kiting, but may need to take a wrap to prevent unintentional launches.

Update 2006/2/8: See Gradient info - Demo wing had brakes too long.

1

1/10

Rucksack can easily contain all equipment.

Significant compression required to fit wing + Sup'Air Profeel XC2 into main compartment. Then unable to fit helmet in central pouch. Construction quality helped avoid null rating. Nice touch to be able to remove waist band.

Too bad for the ill-adapted rucksack, but I will simply keep using my previous one. No big deal, it's the wing I'm really interested in.

·        Pictures in the Daily Notes.

·        Final word: This review is "on hold" until a consensus amongst independent pilots make me believe the Collapse recovery from fully accelerated asymmetric will keep the wing above the pilot. I just want to be safe and not place the burden of risk of more testing onto myself. Once a positive consensus emerges, I will be glad to resume testing, given the opportunity of another test wing. If testing resumes, I will re-test twice that particular maneuver and also re-qualify this wing's handling behavior based on a verified brake line length adjustment (See Gradient info - Demo wing had brakes too long). I would look forward to enjoy the many good qualities of this wing.

 


Daily Notes (Top of Page)

Does not mention all my flight, just whatever is worth reporting.

 

2006/2/3

·        Received Aspen 2 (Size 28, Blue) demo wing. Examined its construction.

·        Pictures:

o       Brake toggle.

o       Flat wing: Underside, Topside.

o       Leading edge openings: Center, Tip.

o       Leading edge wall reinforcement.

o       Upper unsheathed lines.

o       Riser: Global, Pulleys, Pair snap, Bag.

o       Rucksack and wing shell.

o       Transverse load straps.

o       Wing tip micro attachment.

 

2006/2/4

·        2 hours of thermalling at Marshall, California.

·        Pictures:

o       By Mark Kranz:

§         Launching.

§         Top landing.

o       By Bob Barry:

§         Kiting. 12:01 pm time stamp.

§         Soaring. 12:01 pm time stamp.

§         In-flight, underside. 12:05 pm time stamp.

§         In-flight, front view. 12:06 pm time stamp.

o       By myself:

§         In-flight, Left underside.

·        Flight #3 data. Mid day thermalling conditions + Collapse recovery testing. You can find a Google Earth rendition link.

·        Flight #4 data. Soft thermalling. You can find a Google Earth rendition link.

·        Airspeed measured, at 1525 m (5000'), 70ºF:

o       Trim: Varied from 39 to 46 km/h, most often showing 41 km/h. Corrected for 15 ºC and sea level: 37.2 km/h.

o       Max: Varied from 60 to 65 km/h, most often showing 62 km/h.  Corrected for 15 ºC and sea level: 56.3 km/h.

 

2006/2/7

·        Wing returned to distributor for his examination.

 

2006/2/8

·        Gradient info - Demo wing had brakes too long. Ondrej Dupal (Gradient) says there was an error in this series of pre-production wings, and the brake lines were 10 cm too long. This seems confirmed by looking at this picture taken at trim speed (not when adjustment is to be evaluated, see adjustment guideline) the amount of bow does seem more than normal (30 cm bow when accelerated is ideal, here I guess 50 cm at trim, but one could scale knowing the cord length). Until a re-test is possible I removed conclusions on handling in this review.
But brake line adjustment has no influence on my main concern at this time: Collapse recovery behavior from accelerated asymmetric collapse.

 

2006/2/23

·        Link added for the DHV report.

 

2006/3/6

·        Link added for the English manual.

·        Separation of my personal criterions for collapse recovery from those of any certification laboratories (AFNOR, CEN or DHV). See Collapse recovery.

·        Links added to external discussions.

·        Added input from other pilots: Brake line length, frontal collapse recovery from trim, wing tip shape.

 

2006/6/19

·        Added a pilot's experience of an accelerated asymmetric collapse.

 


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