2 Men dead as rope under Helicopter breaks

What your instructor never taught you. Continuing your education and learning from others. Flight safety topics and accident/incident discussions.

Moderator: Moderators

User avatar
mikev
Finals (unmanned) for a Full Stop
Posts: 422
Joined: Sat Mar 22, 2008 10:34 am
Closest Airfield: FAKD
Location: Swartpan International Airport
Has liked: 18 times
Been liked: 12 times

Re: 2 Men dead as rope under Helicopter breaks

Unread post by mikev » Tue Aug 13, 2019 2:23 pm

mikev wrote: ↑Mon Aug 12, 2019 7:04 pm
I suspect the "squib" might have been activated somehow which then jettisoned the load. Very sad.
Either that or they used rock climbing equipment and did not factor in dynamic amplification.

Having hung below all sorts of flying and non flying stuff, I still cringe when I think of it. Horrifying!

Poor souls, may they rest in peace!
Rock climbing ropes are designed for dynamic loads, and will hold approximately 2-3tons, so 2 troops plus 100kg flag at up to 10G’s. They are however sensitive to abrasion and being cut over sharp edges despite all intentions in design against this. However my money is still on an accidental jettison.
All true!

Where the dynamic amplification comes in, is enhanced vibration and resonance because there is now a constant airflow over the rope and the flag towed behind etc. This is not part of the design criteria for rock climbing.

My point is not exclusive to the rope, also inclusive of carabiniers and/or other rock climbing equipment and methods whereby aluminium carabs may be hooked up to steel hooks/clamps, resonance and vibration from the airflow over both rope and flag will be directly impacting on that hookup, dissimilar metals will have an enhanced metal fatigue effect, hence causing failure.
Lions ikke miste søvn over vurderingene av sau
User avatar
biffvj
Joining unmanned airfield circuit
Posts: 388
Joined: Thu Dec 06, 2012 9:29 pm
Closest Airfield: Polokwane Civil
Location: Polokwane
Has liked: 23 times
Been liked: 31 times

Re: 2 Men dead as rope under Helicopter breaks

Unread post by biffvj » Tue Aug 13, 2019 7:05 pm

According to the Colombian military the rope did not disconnect from the helicopter, it broke. Some are even insinuating foreign agents tampered with the rope. On the closeup photographs on Spanish news you can see splices in the rope, so I'll go with budget restraint maintenance issues common to third world countries.
A true friend has the guts to tell you what you need to hear.
User avatar
deanvdm
Post Take off checks
Posts: 222
Joined: Fri May 21, 2010 5:49 pm
Closest Airfield: FAGC
Location: Gauteng
Has liked: 4 times
Been liked: 14 times

Re: 2 Men dead as rope under Helicopter breaks

Unread post by deanvdm » Tue Aug 13, 2019 7:16 pm

mikev wrote:
Tue Aug 13, 2019 2:23 pm
All true!

Where the dynamic amplification comes in, is enhanced vibration and resonance because there is now a constant airflow over the rope and the flag towed behind etc. This is not part of the design criteria for rock climbing.

My point is not exclusive to the rope, also inclusive of carabiniers and/or other rock climbing equipment and methods whereby aluminium carabs may be hooked up to steel hooks/clamps, resonance and vibration from the airflow over both rope and flag will be directly impacting on that hookup, dissimilar metals will have an enhanced metal fatigue effect, hence causing failure.
What a tragic accident.

Without any specific information, one will have to go back and consider what are the most likely causes of high angle and helicopter rescue accidents. The details may differ but the overarching category of the most common weak link is the same as in aviation: human factors. And that should be the prime suspect here too. This could range from choosing the wrong equipment, rigging/connecting it incorrectly, neglecting inspections, complacency etc.

The wind loading of the flag would be very different from normal what would be the case for a short-haul in a rescue context (which is effectively an external human cargo slinging operation) but maybe the banner towing guys can help with some indications of the kind of forces/issues that can be expected.

To me there is nothing in the video esp. the moments leading up to the accident that gives any hints as to a problem developing. There also does not appear to be any significant jerking/bouncing or cyclical loading of the rope (or cable). To me, it appears that the complete assembly (flag + humans + rope (or cable) etc.) suddenly and without much warning separates from the helicopter. What remains attached to the helicopter (or not) will probably be key to understanding what happened and where to go and look for the cause.

Speculation: If one assumes (a big assumption considering the kind of problems in that country) that proper equipment has been used (i.e. along the lines of accepted practices), it would be very strange to see the outright failure of the non-helicopter complement of the equipment being used here as the cause of the accident (ie. assuming appropriate equipment for the job was used and the equipment itself failed despite it being used and rigged correctly). My thinking: short hauls are a relatively well-understood technique under many combinations of longer and shorter ropes, different weights, durations and distances and most of the equipment limitations are, relative to helicopter rescue operations, mitigated to an extent that permits it being used in the context of live human loads. However, this is but for one very important and overriding characteristic of helicopter rescue techniques: there are many single points of failure and very little redundancy in the overall system to safeguard against a failure of any one of the components. Any weak link in the chain can cause the catastrophic failure of the complete system/operation.

The human factors that could be at play in this type of exercise are many-fold: you typically have more organisations involved, like many displays, there are time and budget pressures, there more people involved (and importantly typically from different organisations), there is a higher reliance on good communication, and the list goes on. Compared to a hoist style helicopter rescue, short-haul has a much higher risk profile despite it on the surface appearing to be a very similar style operation. Whereas terrestrial rescue has developed many safeguards against a failure, helicopter rescue has little to mitigate the failure of one of its critical components: humans that make independent decisions and judgment calls.
User avatar
Ugly Duckling
Six Tousand
Six Tousand
Posts: 6500
Joined: Sat Mar 18, 2006 2:24 pm
Closest Airfield: Brakpan Benoni FABB
Location: Waterkloof
Has liked: 417 times
Been liked: 315 times

Re: 2 Men dead as rope under Helicopter breaks

Unread post by Ugly Duckling » Tue Aug 13, 2019 11:24 pm

The tragedy could have been compounded if the remnants of the rope/cable had gone into the tail rotor.
Paul Sabatier EAA Ch 575, SSSA, ERGC, ERFC, AeroClub
Long time Cygnet builder
The object is to fly, it does not matter what the object is!

Return to “Academy & Flight Safety”