Question about mechanical MARD devices

[DonnellyB 2]

I have been searching every corner of the web trying to find an answer to this question.  I'm hoping that the experienced folks here can help me shine a light on it.  For the MARD in the Infinity, there is a trigger that sits in a small pocket.  My understanding is that in the case of a cutaway, the trigger will be extracted from that pocket, and in this moment will lock the right main riser to the center of the reserve pilot chute bridle (essentially by allowing for a change in the angle of the MARD pin).  This facilitates the extraction of the reserve as well as pins the freebag to the cutaway main to help locate it later.

What I'm curious about is if under any circumstance the trigger could be extracted from its housing inadvertently.  And if this is possible, could this result in a reserve pilot chute in tow?  I wonder if in the case of a hard collision with another jumper the force could potentially extract the trigger from the housing, without any main canopy deployment.  Then if this would 'lock' the reserve pilot chute bridle to the right main riser and keep the reserve from deploying (ex. from AAD firing for unconscious jumper after collision)?

Thanks for fielding the question, do also wonder about similar pin and loop designs such as the RAX system.  

[mark 102]

A simple collision is unlikely to extract the trigger.  Think of how difficult it would be to extract a Cypres control head from its pocket in similar circumstances.

You might be able to extract the trigger if the collision involved snagging the RSL.  I can't recall any incidents involving snagged RSLs on any system, so we should consider the probability of this happening to be quite low.

[riggerrob 558]

Modern RSLs and MARDs are ALMOST idiot-proof. You are more likely to dis-lodge the RSL/MARD by slamming your rig around on the ground or slamming a door frame on exit. If you are habitually that rough on your gear, it will not last very long.

For illustration: both Cypres and BOC became fashionable introduced about the same time during the early 1990s. It was briefly fashionable to stand a rig on its yoke to stuff the pilot-chute into the BOC. After a few broken Cypres cables, that packing method fad soon faded.

Container manufacturers responded by shifting Cypres control heads from the right mud-flap to deeper in the reserve container where they were better protected. Other manufacturers of electronic AADs learned from Cypres' problems and installed thicker, more durable cables.

[Deyan 31]

20 hours ago, mark said:

I can't recall any incidents involving snagged RSLs on any system, so we should consider the probability of this happening to be quite low.

You are welcome!

[riggerrob 558]

On 4/1/2023 at 5:55 PM, mark said:

A simple collision is unlikely to extract the trigger.  Think of how difficult it would be to extract a Cypres control head from its pocket in similar circumstances.

You might be able to extract the trigger if the collision involved snagging the RSL.  I can't recall any incidents involving snagged RSLs on any system, so we should consider the probability of this happening to be quite low.

I can think of two accidental deployments involving snagging an RSL.

The first was a static-line student who was not mentally capable of handling the stress of a solo jump. The chief instructor put him out on a static-line jump anyways. After his main opened properly, he searched for the red steering toggles. Every other student grabbed the red steering toggles hanging near their ears. Instead, he fumbled around and pulled red RSL that was velcroed to the yoke behind his neck. He landed his round reserve in the trees beside the bowl. GRRRRRR!

The second accidental deployment occured with an early production Telesis 2 student rig. During an unstable main deployment, the student snagged the RSL and pulled it. Rigging Innovations promptly changed the RSL coverage on the Telesis 2. I doubt if any Telesis 2 are still in service as it was soon replaced in production by the Telesis 3.

[KellyF 16]

On 4/1/2023 at 5:25 PM, DonnellyB said:

What I'm curious about is if under any circumstance the trigger could be extracted from its housing inadvertently.  And if this is possible, could this result in a reserve pilot chute in tow?  I wonder if in the case of a hard collision with another jumper the force could potentially extract the trigger from the housing, without any main canopy deployment.  Then if this would 'lock' the reserve pilot chute bridle to the right main riser and keep the reserve from deploying (ex. from AAD firing for unconscious jumper after collision)?

Yes, if the trigger is fully dislodged from the pocket, and you have a reserve first deployment (not a cutaway from a partial malfunction), you could tow the reserve pilot chute, and you would want to release the snap shackle on the RSL/riser.

NOW, think about the actual process here. You have the MARD that weighs about an ounce, which means it is easy to accelerate and decelerate (Newton's First Law of Motion), that is being held in a tightly packed reserve container. It's likely going to take around 30 lbs. of force to get the MARD to start to move inside the packed container, let alone move the full inch required to clear the trigger from the pocket. Without doing the math, that's going to take a MASSIVE hit to the right side of the jumper's body. Enough of a hit that I think there's going to be two dead jumpers regardless of if their reserves open or not.

[lyosha 46]

Well that's a frightening scenario. I'd be more worried about a jumper not doing gear checks (most don't) and the issue happening on the ground...

[KellyF 16]

6 hours ago, lyosha said:

Well that's a frightening scenario. I'd be more worried about a jumper not doing gear checks (most don't) and the issue happening on the ground...

What issue? The MARD getting pulled/dislodged from of a packed reserve and not getting noticed because a jumper didn't check their gear?

The MARD is VERY secure when packed. If the rig is handled poorly enough that it somehow becomes dislodged on the ground, and the jumper DOESN'T do a COMPLETE gear check afterwards, they shouldn't be participating in the sport, IMO.

We made this system pin checkable after seeing how creative riggers got with other MARD systems. This is an opportunity to give the jumper peace of mind, and to keep riggers in check. We can only do so much as manufacturers.

[wolfriverjoe 1,340]

7 hours ago, KellyF said:

What issue? The MARD getting pulled/dislodged from of a packed reserve and not getting noticed because a jumper didn't check their gear?

The MARD is VERY secure when packed. If the rig is handled poorly enough that it somehow becomes dislodged on the ground, and the jumper DOESN'T do a COMPLETE gear check afterwards, they shouldn't be participating in the sport, IMO.

We made this system pin checkable after seeing how creative riggers got with other MARD systems. This is an opportunity to give the jumper peace of mind, and to keep riggers in check. We can only do so much as manufacturers.

Ya know?

One of the REALLY cool things about this site is that when stuff like this arises, it's not all that uncommon for someone like, oh, the President of USPA to chime in on a discussion.
Or maybe Bill Booth.

Or, in this case, Kelly Farrington. 

You know, the "Velocity Fella". 

Post #6 had an accurate, technical description of what would have to happen for the proposed scenario to emerge.

This last one says "Short answer, not gonna happen unless you really screw up". Along with "we've seen what some idiots are capable of doing, and we deliberately engineered this to avoid that."

Love it.