Reserve Extraction Force Test?

[GLIDEANGLE 1]

Is there a standardized test of how much force it takes to extract a reserve? This would be a test which could be used by a rigger to assess if a specific combination of reserve, container, and main is likely to extract promptly or not. I know that the rigger is responsible to assess this compatibility. How is the rigger to asses this other than “Damn, that sucker is a tight fit!”?

The thumb test led to the TS-108 pull test, the “closing loop seems tight” led to the pin pull force checking tool (lets the pin move a little… but not come out completely during a pull test with a fish scale), so what test do we have for reserve extraction?

My memory seems to recollect a service bulletin that described a test of this… but my brain can’t remember enough to help me find it.

I would imagine that the test would be something like:

1. Secure the rig, belly down, with main packed and reserve container closed.

2. Pull reserve handle to open reserve container.

3. Attach a fish scale to the pilot chute/bridle connection

4. Record the force needed to remove the reserve in five directions: directly UP, toward head, toward feet, right, & left.

The choices we make have consequences, for us & for others!

[spootch 0]

# 4 would be moot after the first extraction.

FWIW i have done periodic tests (curiosity) after the extraction debate was brought up some years ago. I have the jumper stand with rig on and measure the pull on the bridal to extract the molar with the main still packed. The highest i've had was 19.5 lbs. what does that mean for the price of rice in China? nothing, but I have not seen one "stick" or appear to be stuck such as some of the video John S has.

[Southern_Man 0]

I was talking to a well experienced Master Rigger about this last week and he said that he was attaching a fish scale to the bridle and measuring the extraction force when pulling towards the jumper's head as he thought that was the direction that was tightest. You really can't test in more than one direction that I can tell--once you've moved it in one direction it is no longer seated in the container the same way. Anyhow, I am adopting this as my test procedure as well unless there is a better idea put forward.

I wish there was a standardized test and a specific number that we are looking for. My reserve was the only one I had in for repack this week and it was not a problem (large reserve that is not overstuffed).

"What if there were no hypothetical questions?"

[GLIDEANGLE 1]

Quote

# 4 would be moot after the first extraction.

Yes, that is true. I was imprecise in my description. One would have to run this test 5 times with the reserve container closed each time.

The choices we make have consequences, for us & for others!

[ctrph8 0]

I like the thinking on this but I'm having trouble extrapolating it to the real world.

Wouldn't it be a different number for each canopy depending on the weight of the canopy/bag and maybe a whole bunch of other factors? I would think that the extraction force of a tandem would be significantly different than for an Optimum 99 and that number would differ a little from container manufacturer to manufacturer and maybe even from geographic location to geographic location.

Are you looking for a standardized number (It should take XX pounds of force to extract...) or a ratio or something else?

Quote

Is there a standardized test of how much force it takes to extract a reserve? This would be a test which could be used by a rigger to assess if a specific combination of reserve, container, and main is likely to extract promptly or not. I know that the rigger is responsible to assess this compatibility. How is the rigger to asses this other than “Damn, that sucker is a tight fit!”?

The thumb test led to the TS-108 pull test, the “closing loop seems tight” led to the pin pull force checking tool (lets the pin move a little… but not come out completely during a pull test with a fish scale), so what test do we have for reserve extraction?

My memory seems to recollect a service bulletin that described a test of this… but my brain can’t remember enough to help me find it.

I would imagine that the test would be something like:

1. Secure the rig, belly down, with main packed and reserve container closed.

2. Pull reserve handle to open reserve container.

3. Attach a fish scale to the pilot chute/bridle connection

4. Record the force needed to remove the reserve in five directions: directly UP, toward head, toward feet, right, & left.

[GLIDEANGLE 1]

I am looking for a standard. I don't care how it is expressed.

The choices we make have consequences, for us & for others!

[rifleman 61]

I'm not a rigger so take this with a pinch of salt - maybe have the maximum allowable extraction force for the freebag as a percentage of the snatch force of the PC eg: extraction force <= 75% of PC snatch force

As I say, I know nothing about the subject but it just seems that if as John Sherman says PC's are not generating enough force to lift the bag from the container then maybe it's time to start making sure that the PC has got enough force to do the job it's supposed to.

I also suspect that buying the next size container down from what you actually need atm then stuffing a tight fitting main and reserve into it doesn't help either.

Atheism is a Non-Prophet Organisation

[cgoodlet 0]

I would have to agree with this thought. As obvious as it seems, you absolutely want the pull out force to be some percentage less then the PC can generate in a sub terminal malfunction.

[riggerrob 558]

Ask John Sherman because he expounded on the subject - at great length - during the 2013 Parachute Industry Association Symposium in Daytona Beach, Florida ... last week.

[JohnSherman 1]

Quote

Is there a standardized test of how much force it takes to extract a reserve?

The BPA has adopted a standard test, attached.

Additionally they have released a companion video:
https://www.youtube.com/watch?v=bSvxHutNFTM


Additionally, See:http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Extraction_of_Rsv.&SortBy=DATE_D
and
http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=18pounds&SortBy=DATE_D

The extraction force can not excede the capability of the pilot chute. In many cases still an unknown.

[GLIDEANGLE 1]

Thank you Mr. Sherman!!!

The choices we make have consequences, for us & for others!

[peter.draper 0]

2 years ago I had a factory assembled and packed Mirage G4 here. I left the main in to imitate a total and fired the reserve. The launch was decent, when I went to pull the bridle I lifted the rig off the ground, I could swing it around and nothing came out. I re-closed the rig and put it on a friend (who weighs 120lb) when I attached a fish scale and pulled straight up his shoulders came up and the scale topped out at 43 lbs straight up, over 50 lbs when pulled toward the main.

[p.w.stockwell 0]

It was me that proposed the opening procedure in the UK. It will be circulated to all packers and riggers in the UK as an acceptable method of opening a reserve. It does include guidance when to refer the system to Riggers committee. It is not mandatory or a rule as that would cause difficulties if a rigger is handed a container that is already open for example but many have started to use it already and are surprised by the results they are getting. I hope it will make packers more aware of the effect of closing loop length and trapping canopy material under the reserve pilot-chute. I also hope, with having a lot of people measuring the extraction force, we will start to get some useful data that can be discussed with manufactures if it is high. At least they will have to say if a rig is OK at 40+lbs or not. Its time we started to ask from a position of Knowledge rather than ignorance to avoid the smoke a mirrors manufacturers sometimes employe when they don't really want to answer the question.

Credit to Mr John Sherman for his ideas and help

.

Quote

Quote

Is there a standardized test of how much force it takes to extract a reserve?

The BPA has adopted a standard test, attached.

Additionally they have released a companion video:
https://www.youtube.com/watch?v=bSvxHutNFTM


Additionally, See:http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Extraction_of_Rsv.&SortBy=DATE_D
and
http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=18pounds&SortBy=DATE_D

The extraction force can not excede the capability of the pilot chute. In many cases still an unknown.

[babz 0]

Hi Paul,

Does this mean that the BPA are insisting that this is done on the previous pack job (i.e. at repack time) or before the paperwork is signed off for the next packjob (i.e. the AP/Rigger has to pack the kit, test it, close it again)?

Also is it a recommendation or a mandatory test as part of the repack (STC/Rigger minutes not available on BPA Site)

Am just curious as if it is the former this will mean I can no longer effectively practise reserve drills at repack time.

[freekflyguy 0]

Babz, the procedure should be carried out prior to a repack and is a recommendation and not compulsory.

Ideally it should be done with the owner wearing the rig as it allows them to:

A. Practice their reserve drills as you have mentioned.
B. See how their equipment performs in the worst case scenario (low altitude AC emergency exiting on your reserve at low airspeed).
C. Revise their decisions regarding opening heights, equipment choices, A/C emergencies etc.

Interestingly, Bill Booth expressed his concerns regarding reserve deployment speeds, opening heights and AAD activation heights in DSE's interview with him at the PIA which can be seen on another thread on DZ.com.

It is hoped that although it is not mandatory this procedure will be widely adopted and we can see if there is a trend with equipment types/configurations that leads to excessive reserve deployment times and from that educate users.

Hope that clarifies things.

It's nice to be important, but it's more important to be nice.

[babz 0]

Cheers Buzz, it's an interesting subject that trying to get my head around. I've heard various opinions on reserve extracting forces (other than on DZ.com) and also how reserve PC design impacts this.

I've just had a try (not popping the reserve as I don't fancy wasting £40) of this, I was a little concerned as I do a 'both hands on each handle' drill, that it wouldn't be do able - however it is but a little awkward.

How does this take into account skyhooks? From the last time I cutaway on the ground the PC didn't have enough force to break red seal thread and therefore the skyhook didn't disconnect so couldn't get to full extension (i.e. failing the 5ft clearance).

Are these guidelines published yet?