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  1. #31
    Join Date
    21st April 2011
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    Australia
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    Quote Originally Posted by Feckless Counsel View Post
    I think the program is financed but might ask for loans of big parachutes.
    Great project watching with interest - sky diving parachutes are good for this size (ya think!!!). We sourced 3 'decommissioned' 'man-rated' chutes for the V2...

    IIRC 'they' have to throw them out after a certain time period or amount of 'jumps/uses', so you maybe able to come across some relatively cheaply - ex-army, military surplus...etc...

    Edit: where I say we, I mean Krusty - maybe shoot him a PM for details...

    Last edited by astrojase; 8th August 2016 at 07:17 AM. Reason: as stated
    Me and my rockets run on moonshine.
    Lvl 1 - Scratch built 1/4 scale D-Region Tomahawk AT I600.
    Lvl 2 - Performance Rocketry Nike Smoke AT K1100.
    Lvl 3 - Scratch built 2/3 scale D-Region Tomahawk AT M650.

    Jason Batey - TRA13325
    Jase's Youtube Channel.

  2. #32
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    18th January 2009
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    Virginia - Central
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    3,999
    Quote Originally Posted by astrojase View Post
    Great project watching with interest - sky diving parachutes are good for this size (ya think!!!). We sourced 3 'decommissioned' 'man-rated' chutes for the V2...

    IIRC 'they' have to throw them out after a certain time period or amount of 'jumps/uses', so you maybe able to come across some relatively cheaply - ex-army, military surplus...etc...

    Edit: where I say we, I mean Krusty - maybe shoot him a PM for details...
    28 foot double Ls can be had....just check to make sure they aren't rendered useless.
    Sometimes they will cut off the suspension lines to decommission them when sold, they will usually indicate that and say they are for tents or something like that.
    Others will leave them on with a warning not to be used for intentional sport jumps.

    We got two categories of pilots around here. We got your prime pilots that get all the hot planes, and we got your pud-knockers who DREAM about getting the hot planes.
    Now what are you two pud-knockers gonna have?... Huh?”
    Pancho Barnes-
    The Right Stuff
    http://www.mwavs.com/0053148414/M4RS...udknockers.m4r

    Tripoli #2747

  3. #33
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    18th January 2009
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    Amazing project. I hope that I can make it our to see it go up!
    Dick Stafford
    The member formerly known as the Pointy-Haired Moderator.
    The Original Rocket Dungeon
    Volunteer compiler of product news for ROCKETS Magazine

  4. #34
    Join Date
    18th December 2010
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    TRF,

    Our team continues to advance CAD work for this model. Please see attached images:

    1. Scale study of this project relative to 6 foot tall man.
    2. Capsule renderings including ejection canisters.

    Will provide a detailed illustration on the recovery scheme soon. May I please thank you for the comments on availability of larger parachutes.

    Feckless Counsel
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  5. #35
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    TRF,

    Steady progress the last three months. We are targeting TAP review early January and construction start late January.

    Feckless Counsel
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  6. #36
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    Do you have some idea of where the recovery loads and attachments will be? I see you aren't keeping a stuffer tube up the middle, which I've found in my lightweight built up airframes to be a bonus in adding some rigidity in tying the airframe together and taking recovery loads. I understand this is quite a bit larger than things I've done but was just curious.

    Frank

  7. #37
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    15th March 2016
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    336
    If you need larger than man rated chutes, look into military surplus cargo chutes. I saw some hundred foot ones somewhere... Needless to say, they were larger than I was looking for.

    I saw your test section at MDRA over the summer, very impressive. Good luck! I'm looking forward to seeing this one for sure now.

  8. #38
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    Frank,

    No central tube. We believe simulation supports a semi-monocoque design through all phases of flight. The recovery attachments, as you indicate, are a point of discussion. Here are the basic points tabled at out last meeting:

    Booster and airframe are individually 250 pounds
    Booster plus spent motor and recovery stuff is 350 pounds
    Recovery is 10G acceleration. Therefore attachment should support 10x weight.
    Therefore booster recovery “weight” is 3,500 pounds.
    ½”-13 in grade B-7 steel and equivalent eye nut adequate to support that “weight.”

    Regarding the steel attachments rooted in the rocket we have considered an equivalent 1-1/4 inch thickness of Baltic birch plywood backed by a 3-inch washer.
    Consider the booster section. That plywood equivalence is one ¾-inch thick thrust plate, one ¼-inch thick central plate and one ½-inch thick coupling plate. All those pieces are joined by a ½-13 steel rod in tension across all plates. So joined the plates are equivalent to a single 1-1/4 inch plate with a ½-inch steel attachment bolted through.

    You buy that argument?

    Best regards,

    Feckless Counsel

    Post Script: Does this inform our discussion brother T.C.

  9. #39
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    27th January 2009
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    Oregon
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    I buy your calculations and the idea of tying the plates together. I just have questions about the recovery attach points. A rocket going vertical in compression and sustaining that load is different when you have something tumbling or at an angle then pulling to a recovery position, I would think if you can have the lower section recover tying into the thrust plate that would be a good idea, just not sure where you will break the rocket into pieces, and where they will tie in. If it were me, I'd solidify that solution before completing design work on the structure, but that's just me. The majority of large rockets I see fail are usually in a)lack of deployment, b)recovery attach failures, c)deployment failures(chute tangles, etc).

    I like your structure approach and I think that's a much more elegant way to build large rockets.

    Frank

  10. #40
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    15th March 2016
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    336
    Where did your 10g's come from? I've heard people quote as high as 40g deployment forces for smaller rockets (everything is smaller when you attempt a world record), and I would not be cutting this close. If you have data, great, but remember that these forces are highly dependent on shock cord lengths, charge sizes, and chute packing technique. You may want to fly some smaller L-3 birds with various recovery setups, for the sole purpose of getting data and planning this thing. Also, get data from every previous record holder you can, along with as much info on how they deployed their gear as you can get. Some projects like this failed. Find out how and why.

  11. #41
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    18th December 2010
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    AdAstra,

    Thanks for your reply. The 10G number is not well developed. It is loose. Sources include skydiving data, NWC technical report 6575 and some noisy altimeter data. After a lot of discussion we believe it represents an adequate design goal.

    Still skeptical? Maybe this line of reasoning is convincing?

    Let’s say any one piece has a “terminal velocity” of 70 meters per-second. Because this thing is massive lets also say we intend to land at 3 meters per-second. First let’s assume we’re using good technique and have a reasonably linear deceleration over 2 seconds. The deceleration is 67 / 2 = 34 or about 3.5G. But real chutes are not linear so let’s assume the parachute has a “opening force coefficient” of 1.5. Even then the peak load on the attachment would be less than 6G.

    Feckless Counsel

  12. #42
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    23rd July 2011
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    Butte, MT
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    I've seen quite a few instances where rocketry data showed gee forces at about 30 gees when the main opens. Unless you're reefing your chute line and possibly using a slider to soften the opening the deceleration is definitely not close to linear.


    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  13. #43
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    20th February 2009
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    Quote Originally Posted by Feckless Counsel View Post
    AdAstra,

    Thanks for your reply. The 10G number is not well developed. It is loose. Sources include skydiving data, NWC technical report 6575 and some noisy altimeter data. After a lot of discussion we believe it represents an adequate design goal.

    Still skeptical? Maybe this line of reasoning is convincing?

    Let’s say any one piece has a “terminal velocity” of 70 meters per-second. Because this thing is massive lets also say we intend to land at 3 meters per-second. First let’s assume we’re using good technique and have a reasonably linear deceleration over 2 seconds. The deceleration is 67 / 2 = 34 or about 3.5G. But real chutes are not linear so let’s assume the parachute has a “opening force coefficient” of 1.5. Even then the peak load on the attachment would be less than 6G.

    Feckless Counsel
    10 gee is a good rule of thumb for a nominal flight profile. Typically you need to plan for 4X to 5X that to account for potential anomalies.
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  14. #44
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    18th December 2010
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    TRF,

    May I thank you for this excellent discussion. Perhaps this dialog demonstrates a general gap in knowledge?

    I am familiar with accelerometer data indicating very high G accelerations. But those are measured at the accelerometer. Those are also reasonably high bandwidth measurements. So we could be measuring 50G at the accelerometer at 2kHz.

    What is missing is direct measurement of riser loads at deployment. I have been unable to find those data for sport rocketry.

    Feckless Counsel

  15. #45
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    5th December 2013
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    Quote Originally Posted by Feckless Counsel View Post
    TRF,

    May I thank you for this excellent discussion. Perhaps this dialog demonstrates a general gap in knowledge?

    I am familiar with accelerometer data indicating very high G accelerations. But those are measured at the accelerometer. Those are also reasonably high bandwidth measurements. So we could be measuring 50G at the accelerometer at 2kHz.

    What is missing is direct measurement of riser loads at deployment. I have been unable to find those data for sport rocketry.

    Feckless Counsel
    Feckless,

    Please keep in mind the MDRA field schedule. After LDRS, we move to the SOD farm for the summer. I know you mentioned fall, but if Tommy has another good bean crop, then we might not get back to Higgs until December. Could end up being a winter launch.

    BTW, I am no use to you at all, but depending on where you are doing your build, I would love to stop by sometime to see what you're doing. It would be a learning experience for me; but mostly it would just be a wow moment.

    PM me if you would be open to me stopping by sometime.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  16. #46
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    18th December 2010
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    TRF,

    Please note AEROPAC have developed some interesting data concerned with shock and vibrations that might damage electronics payloads. Those data are NOT parachute riser data. Instead those are data recorded at the payload.

    http://www.feretich.com/rocketry/Res...ger/index.html
    http://www.aeropac.org/newsletters/S...Newsletter.pdf

    Note the deployment data and videos. Indeed there are data at the payload exceeding 50G. But also note there is NO cordage present in the experimental video. That 50G data is a record of deployment charge acceleration.

    Feckless Counsel

  17. #47
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    23rd February 2014
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    Eastern Shore, MD
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    Searching on DTIC.mil you can find "Parachute Recovery Systems Design Manual" from 1991 which may have data you can use. There was all kinds of hits for "parachute riser loads".
    Dennis Kingsley
    NAR #97251, TRA #17554, MDRA #128
    L1 - Madcow Torrent
    L2 - Madcow Sensor
    L3 - Extended Madcow Stinger

  18. #48
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    18th December 2010
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    djkingsley,

    Thank you for this information. We are aware of the publication otherwise known as NWC TP 6575. That manual, all 500 pages of it, is about as deep and you can get without access to a supercomputer and some serious hydro-code.

    From our reading it says shock loads may be estimated by the following process:

    1. Pick a chute style
    2. Design for landing velocity
    3. Use parachute area from step 2 to calculate drag force at DEPLOYMENT SPEED
    4. Multiply drag force of step 3 by opening force coefficient, a tabular value
    5. Use the force in step 4 or refine the number using other nuanced factors

    Is that how you read the process?

    Feckless Counsel

  19. #49
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    15th December 2011
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    Too far from the event horizon.
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    Many of the high-G acellerometer spikes often seen correspond to the separation charge in dual-deploy setups. I did not get the impression that this project will be such a beast, and that the general figuring was for an apogee deployment. If so, the opening shock, then, should be significantly less than having something screaming in at 80-100 FPS and deploying a large main. 10G's sounds reasonable, if so. Personally, I'd build for 25, just to have a presentable safety margin built-in...

    Then again, I only have a handful of rockets taller than this thing is wide, so what do I know?


    Later!

    --Coop
    "For although the nepenthe has calmed me, I know always that I am an outsider; a stranger in this century and among those who are still men." --HP Lovecraft

    Custom crafted recovery: http://paramedichutes.com

  20. #50
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    11th October 2016
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    Twin Cities, MN
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    Feckless,

    If you decide to go military surplus on parachutes and need guidance let me know.
    I am currently a full time parachute rigger for the Minnesota Air National Guard.
    We deal with cargo airdrops at least twice a month up to 3600 pounds per heavy drop load for our big ones, and around 640 lbs for our smaller ones.
    If you need numbers on how much weight each chute can safely recover, weights for each chute, etc, I'd be willing to help with that if needed.
    For the weights alone (not including your 10G calculation) your best (and least complicated) parachute to try to get your hands on would be a G12 cargo chute.
    The cost new is about $4600 per chute. Not sure how much they go for as military surplus.
    It might be hard to find them as surplus because most units that drop them stateside reuse them until they are no longer usable as a parachute.
    Overseas, they are a one and done, leave it behind kind of deal.
    We use two G12's on our heavy drop platforms that weigh 3600 pounds.
    PM me if you want any more info.
    Hope this helps!

  21. #51
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    Are we still targeting fall17? I need to put in for vacation.

    For those of us on the Wrong Coast; how can we help?

  22. #52
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    18th December 2010
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    Ccolvin968,

    Thanks for your reply. The G-12 parachute has certainly been part of the discussion. But we are concerned that’s too much parachute. It’s something like 7 cubic-foot packed and weighs 130 pounds. Is that correct?

    Otherwise what do you think of the G-14 parachute? Note we want to land 350 pounds at 10 feet per-second.

    Feckless Counsel

  23. #53
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    dhbarr,

    We are hoping for a design review late January. That should bring us closer to a launch date. As Bat-mite mentioned the fall can be difficult to schedule given crops. Either way we will keep you informed.

    Feckless Counsel

  24. #54
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    11th October 2016
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    Yes, that is correct. Packed the G12's are roughly 130 lbs.
    I have not packed a G14 either in school or at my duty station so I can not speak from experience.
    From what I can gather in the Technical Manual, it weighs roughly 37 lbs and is about 2.2 cubic feet.
    The chute is able to support loads up to 500 lbs. Again, this is suspended weight.
    I'm sure if they can kick it out of a C130 at roughly 140mph it should work fine for a 150 pound rocket.
    The descent rates are as follows on a per chute basis for a 200 pound payload.


    1 chute: 15.6 fps
    2 chutes: 11.5 fps
    3 chutes: 9.8 fps
    4 chutes: 8.7 fps
    5 chutes: 7.7 fps

    I'm on my phone posting this right now, but if you'd like I can send you a link to the TM for the G14 specifications.
    I'll try to attach the chart from my phone.
    If it doesn't work, I'll post it from my laptop later.
    Hope this helps!
    Chris
    TRA 16662
    L1: 30 October 16, 3" Formula 75, 29mm H123, 871 Ft.
    L2: 13 May 17: 4" Tomach, 54mm K650, 6756 Ft.

  25. #55
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    18th December 2010
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    Ccolvin968,

    Thanks for these technical data. Single G-14 appears too fast for the estimated 350 pound booster.

    May I suggest that landing momentum is more important than landing velocity. Landing velocity “rules of thumb” will result in airframe failure as mass increases. Instead we should fix landing momentum and scale landing velocity accordingly. Does this idea mirror any of your professional training?

    Consider 17 FPS (5 MPS) is acceptable for a 50 pound (23 kg) rocket landing on soil. The total momentum is 115 kg-m /s. Now consider the booster in this project is 350 pounds (160 kg). The same momentum would have a landing velocity about 1 MPS or 3 FPS.

    Feckless Counsel

  26. #56
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    15th March 2016
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    What sort of impact is your structure designed for? This is the real question. Your structure is not just a scaled version of a typical 50 lb bird, and I would say your scaling needs to take into account the increased strength of the larger structure anyway.

  27. #57
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    Quote Originally Posted by AdAstraPerAspera View Post
    ...I would say your scaling needs to take into account the increased strength of the larger structure anyway.
    Yes, I would hope so, otherwise they should stop the project now.
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  28. #58
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    Quote Originally Posted by Feckless Counsel View Post
    Ccolvin968,

    Thanks for these technical data. Single G-14 appears too fast for the estimated 350 pound booster.

    May I suggest that landing momentum is more important than landing velocity. Landing velocity “rules of thumb” will result in airframe failure as mass increases. Instead we should fix landing momentum and scale landing velocity accordingly. Does this idea mirror any of your professional training?

    Consider 17 FPS (5 MPS) is acceptable for a 50 pound (23 kg) rocket landing on soil. The total momentum is 115 kg-m /s. Now consider the booster in this project is 350 pounds (160 kg). The same momentum would have a landing velocity about 1 MPS or 3 FPS.

    Feckless Counsel
    It's not as simple as momentum. You're on a bit of the right track. The rocket undergoes a change of momentum, impulse. Just as when Impulse is delivered by a rocket motor, it's the force delivered over some time as the rocket lands and how that force is distributed or concentrated in some portions of the rocket. Slowing the velocity certainly reduces the impulse, but you really need to be looking at how the rocket will hit, where the force will be concentrated, and whether the rocket body has the ability to flex or if it will simply break.
    Having breakaway fins or an sacrificial section at the aft endmay be a way to absorb some of the energy.
    I do not see how you would get a rocket of this size to 3 ft/s. Notice that the chart listing the target descent rate and number of chutes is non-linear.


    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  29. #59
    Join Date
    9th May 2009
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    1,577
    As with a lot of things associated with recovery, determining acceptable descent rate from deceleration at landing depends on a lot of parameters that are hard to know, for example how springy/yielding your landing surface is. Obviously, coming down on sod is a lot less stressing than coming down on concrete. It also depends strongly on what hits first, what that contact area is, and how the impact is distributed to the rest of the structure. Big projects I've seen have usually aimed for the low end of the typical guidelines for descent rate: 10 to 15 FPS. You may end up being limited by the size and weight of the chute you can afford to fit in the airframe. Or you could consider coming down in two or more pieces, having breakaway fins, etc.

  30. #60
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    11th October 2016
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    Feckless,

    I apologize, I misread your post before. I read it as 150 for some reason.
    As for getting 350 lbs to 3 ft/s... That is a very tall order.
    Also, keep in mind that each chute has a minimum weight in order to function properly.
    With that being said, you only have a few chutes to pick from.
    None of them in any configuration will slow 350 pounds to 3 ft/s.
    You can pick from the following. Charts for a 400 pound load is included for each. (Increments of 50 are not on the table.)

    G13:

    1 chute 23.7
    2 chutes 17.8
    3 chutes 15.0
    4 chutes 12.9
    5 chutes 11.8

    G14:

    1 chute 22.2
    2 chutes 16.4
    3 chutes 13.8
    4 chutes 12.3
    5 chutes 11.0


    T10C:
    Old personnel chutes: No data available. Minimum drop weight 150 lbs

    T10R:
    Old personnel chutes: No data available. Minimum drop weight 150 lbs

    Chris
    TRA 16662
    L1: 30 October 16, 3" Formula 75, 29mm H123, 871 Ft.
    L2: 13 May 17: 4" Tomach, 54mm K650, 6756 Ft.

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