GA1383 (Skydiving & Parachuting)
Twists and Tangles – Longer version
Report text: [Parachute was] deployed at 3,000ft, fully open at 2,432ft, line twist so decided kick and pull.
Mistake no.1 – I did not look above line twist. Lines untwisted at 1,410ft and realised slider was snagged high up toward canopy.
Mistake no.2 – should have cutaway. Decided instead to release brakes to see if snag could be resolved, canopy bowed in middle, 1,000ft.
Mistake no.3 – should have cutaway. Instead decided canopy could be flown and landed. Canopy would only turn partially so ended up way off landing zone. Approaching ground only then realised how fast I was descending.
Mistake no. 4 – flared. Canopy did not slow it collapsed, fortunately landed on grass between trees and flat on my back. I think if I had done parachute landing fall broken leg(s) would have ensued.
Overall issue: Observation, altitude decision, slider design.
Main points: Slider strings have end tabs. Cutaway before hard deck
Lessons Learned: Look beyond obvious faults. Do not attempt to fly anything that is not big and rectangular. Decide early, if in any doubt whatsoever cutaway. Awareness, distraction.
CHIRP Comment: This was an honest and insightful report. The reporter has candidly identified the causes of the problem and some nodal points where, in hindsight, different decisions could have been made. This rather fraught experience will almost certainly have permanently altered their skydiving behaviour.
Equipment Factors
Modern gliding ram-air parachutes are so keen to open rapidly that they all have to have a device fitted to slow the opening, in order to protect the jumper and the canopy from harm. This device, named a slider and about the size of a kitchen dishcloth, is fitted to the lines and packed with the canopy in a way that restricts the opening of the canopy until the slider is gradually pushed down the lines to just above the jumpers head.
Slider up by Canopy:
Slider halfway down the lines :
Slider down and canopy fully open:
Once the canopy is open, the slider has no further useful function but causes a little drag, flaps loudly and may sometimes abrade the lines. Once licenced, jumpers may choose a slider with drawstrings, which can be pulled to collapse it and reduce the nuisance:
When the parachute is repacked, the drawstrings are drawn back into the slider. If the drawstrings have a tab on the end, it has to be drawn back into a pouch on the slider – this indicates that the slider has been adequately reset and usually keeps the tabs in place during parachute deployment.
Drawstring tabs properly seated:
One tab clearly not reseated:
Tab less obviously not correctly seated:
Whether packing for oneself or using a drop-zone packing service, it is important to ensure such tabs are fully seated before continuing the pack job.
During this reported incident, one drawstring tab has been able to come free and tangle in a ‘cascade’ (where two lines attached to the parachute are fused into a single line halfway down to the parachutist). This is a known but infrequent cause of malfunctions. The report includes an image showing how this happened. The canopy manufacturer’s manual from 2010 states:
Slider: Drawstring/Kill-line
Your slider is equipped with a drawstring “kill-line” for stealthier flight. Please always remember to pull this back to the OPEN position prior to packing it. Your parachute will open VERY HARD if you do not do this! Be sure to pull the slider apart to the fully open position. By fully retracting the drawstring, you are much less likely to have the tab on the end of the line snag in a suspension line cascade possibly causing a malfunction.
While it is disappointing that the reporter has received no direct response to their email to the manufacturer, it is of note that the manufacturer is currently advertising this make of canopy as having ‘continuous Dacron lines’ (i.e. no cascades) and a ‘snag resistant collapsible slider’ so that ‘cascade related malfunctions are impossible’. It appears that the issue may have been addressed here already. The data label on the canopy should indicate when it was manufactured.
Looking at a range of other new canopies, it is common nowadays to see collapsible sliders without any tabs on the drawstring, but a longer drawstring so that a 7-10cm excess is always visible when ‘set’. This lack of a tabs makes entanglement less likely.
It is common for A and B licence holders to use rental equipment or buy pre-used equipment either while they assess their long-term equipment needs or simply because it is cheaper than buying new kit. This is perfectly normal practice and there will be plenty of jumpers still with tabs on their slider drawstrings. The incidence of problems with these tabs is not high enough to need to withdraw them. This report should act as a useful specific reminder of the importance of careful reseating of slider tabs when packing. It also acts to remind all jumpers that older kit may have legacy issues which have been designed out of newer equipment. It may be wise to take detailed advice from a qualified rigger before purchasing pre-used kit and discuss whether any modifications would be helpful or even required.
If the reporter owns their own kit, they could request a parachute rigger to replace their tab drawstrings with the longer tab-free version. This would not be an onerous or expensive job and almost certainly much cheaper than a reserve parachute repack fee.
Normal skydiving practice
Skydivers have two parachutes on their backs, a main and a reserve. The main parachute must be fully open and controllable by a specified minimum ‘opening height’ that is determined by their licence status (3000 ft agl in the case of a B-Licence holder). Parachutes take a few seconds to open while the skydiver is descending at almost 200 feet per second and so ‘pulling’ or initiating the main parachute deployment needs to be done 400-800 feet above the minimum opening altitude. It is common practice to be fully open well above the minimum altitude – it is a ‘minimum’ not a ‘target’.
If a main parachute fails to open to a normal and fully controllable state, the skydiver has a short time in which to decide whether they can remedy the situation or if they need to start their emergency procedures. If the former, they can attempt resolution down to their ‘decision height’ but should then initiate emergency procedures if the problem has not cleared. If the latter, they should start the emergency procedures even if well above decision height. The usual emergency procedure is to jettison the main parachute by pulling a single ‘Cutaway Pad’, falling free and then activating their reserve parachute by pulling the reserve ripcord. If the skydiver has not cutaway by ‘minimum cutaway height’, it is now too dangerous to cutaway and the only choices left are to stay with just the imperfect main canopy or to deploy the reserve with the main canopy still attached. Both of these final choices carry a risk of a serious outcome and a skydiver should always try to make good choices long before reaching this height.
Malfunction or Nuisance factor?
If a canopy is clearly malformed or damaged, then it is usually a malfunction and requires the start of emergency procedures. However, other problems such as twists MAY be just a nuisance which can be resolved before decision height. When a canopy opens normally but either the jumper or the canopy turns during opening, this may put one or more twists in the lines. Twists will often untwist spontaneously, and this may be accelerated by skydiver actions such as ‘kicking out’. However, while the twists remain it is not possible to turn or flare the parachute or even perform a controllability check. Twists are a relatively common nuisance factor and, particularly on ‘lower performance’ and lightly loaded canopies used by less experienced jumpers, a skydiver may develop an incorrect expectation that they will always resolve. As in this report, the jumper may look only at the twists and not see past them to a malfunction above the twists, the twists may conceal a malfunction within themselves or the jumper may mistake tangled lines for twists.
Twists with a normal canopy – reasonable to try to kick out twists while monitoring height – must cutaway if twists still present by decision altitude:
Yes, there may be twists in the lines but there is also a small and distorted canopy above them. Malfunction – cutaway:
Occasionally, especially on high performance or heavily loaded canopies used by more experienced jumpers, the twists can cause the canopy to go into a spiral dive with rapid height loss despite the canopy being fully open. In such a spiral dive, gyroscopic stability can make it almost impossible to ‘kick-out’ the twists. This latter situation is certainly not just a nuisance factor and often requires immediate emergency procedures – this may be the subject of a very detailed advanced instructor brief during progression to C and D licences and the use of these higher performance canopies.
Jettisoning a main parachute which appears mostly open takes a degree of resolve, particularly if it looks as if it may improve shortly. It is easy to keep on trying to sort it out well past decision altitude, or even to forget about decision altitude, and then find one is also too low to cutaway and there is no easy way out.
So, by ‘decision height’, the jumper should be sure that the canopy is large, rectangular and undamaged with lines that are clear, untangled and undamaged and that the canopy is fully controllable with turns in each direction and normal flare response to using the brakes. The controllability check is an essential part of a canopy check, which should follow immediately after ensuring there is no risk of collision with other canopies. If the canopy is flared for the first time at 20 feet above the ground, it is too late to do anything if it stalls or collapses (except for attempting a good landing roll if possible).
The reporter states that when their canopy collapsed near to ground level, they were thrown onto their back. They expressed the view that they may have broken their legs if they had attempted a PLF (parachute landing fall – a technique which spreads the impact across multiple body areas and reduces the risk of injury). The skydivers on the CHIRP Advisory Board were of the unanimous view that a PLF remains the best way of reducing the risk of serious injury during a hard landing, even if a lower leg injury may occasionally be the price of avoiding a spinal, chest or head injury.
For a safe jump, the jumper needs to have a clear plan in their head long before walking out to the aircraft. The plan should include choreography of all jumpers to ensure clear airspace in time to deploy at an altitude which gives them an open and controllable canopy at or above their minimum opening height. They must have a clearly defined and memorised decision height and be resolute that they will commit to emergency procedures if their canopy and lines do not look normal and behave normally by that height. They must have clearly pre-determined that any attempt to clear a problem will be interspersed with frequent altitude checks and that they will not go past decision altitude. Finally, they must have a clear minimum cutaway altitude since low cutaways may be fatal or life altering.
Exact decision altitudes and minimum cutaway altitudes are affected by many considerations including exact type of equipment, Automatic Activation Device (the device that automatically activates the reserve) settings, local geography, jumper experience and currency. Student skydivers must do exactly as instructed on their courses. Licenced skydivers who are not clear about these altitudes should discuss with an advanced instructor before manifesting for their next jump. Any skydiver will benefit from regularly practicing emergency drills in a suspended harness. Many drop zones run a safety day each spring, providing supervised simple and complex emergency drills for any skydiver who wishes it. Don’t be shy – have a go – it may save you!
Applicable Aphorisms
One of the least useful things in aviation/skydiving – sky above you
If in doubt, get it out
Don’t delay, cutaway
Dirty Dozen Human Factors
In addition to the reporter’s own excellent analysis, the following ‘Dirty Dozen’ Human Factors elements were a key part of the CHIRP discussions about this report and are intended to provide food for thought when considering aspects that might be pertinent in similar circumstances.
Knowledge
– Information from manufacturers manual needs to be read and understood.
– Required opening height should be known and its implications understood.
Distraction
– Concentrated on twists rather than looking for problem above twists.
– Focused on task of resolving twists to the detriment of effective cutaway decisions.
Complacency
– Over-assumption of ability or habitual behaviour eg twists have always been resolved in the past
Assertiveness
– Indecisive about committing to a cutaway either above or at safe predetermined height (pressonitis)
