Dual deploy reliability

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taiwanluthiers

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It's weird but the only time I have seen dual deploy (not much, a long time ago at NARAM and just today at the AARG launch) they have all failed. Either the altimeter failed to detect launch (so it didn't do anything) or it just won't deploy at all. What are the chances of this happening? Seeing them really made me afraid to dual deploy.

Also what's wrong with G-Wiz flight computers? Some people don't like them it seems.
 
Odd most I have seen are successful I have had a fail or two but 90% is user setup error.

TA
 
G-Wiz use to be reliable.
They were ahead of their time when they first came out (around 1999).
3 channels; one dedicated for air-starts or staging along with DD.

I had 2 LCX units til last year when I lost one due to no events occurring.
Possible power loss.
The unit was compacted and crushed the PCB so I could not retrieve any data.

The other one failed to fire the air-starts after burnout.
It did however record peak altitude... too bad it wasn't used for that.

Their MC2 had firmware issues. I started flying mine after the firmware was straightened out.
It had about 5 good flights before it buried itself.
I think it lost power on the way up so, I don't really attribute that to an error by the unit.
They are OoP now, website has gone away.

JD
 
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I've been flying DD since 1996, with over 300 successful flights (a guesstimate).

It's all in the preparation.


JD
 
On the one hand, ANY extra complexity in a given system is technically one more thing that can fail. And in this regard, the concept of K.I.S.S. makes sense. And for some rockets/flights, I'd much rather go with motor eject/single deploy.

That said, in my experience pretty much all currently available dual-deploy altimeters are nothing less than ULTRA reliable. I would venture to say (though this is conjecture on my part) that the vast majority of flight problems that happen in dual-deploy are the result of some sort of user error - things like faulty connections, not checking ejection charge lighters before use, not enough (or too much) ejection charge, poor battery mounting, poor sim calculations, recovery harness or parachute not packed well, no ground testing, etc. I've never had an altimeter simply not work, and it's rare that I hear about someone else experiencing it (though, it CAN happen, yes). But have I seen a flight problems (and rocket damage) due to faulty delays when using motor eject? - definitely, quite a bit in fact. In my experience electronic ejection is VASTLY MORE reliable, and my preferred method the large majority of the time.

Honestly, dual deploy is really not all that difficult to do. If you pay attention and are methodical about your pre-flight setup, it really is very reliable. Yes, there are a lot of things to consider and think about, but that's what makes this hobby interesting and fun! Don't be afraid of dual deploy and/or electronic deployments - they really do work.

s6
 
On the one hand, ANY extra complexity in a given system is technically one more thing that can fail. And in this regard, the concept of K.I.S.S. makes sense. And for some rockets/flights, I'd much rather go with motor eject/single deploy.

That said, in my experience pretty much all currently available dual-deploy altimeters are nothing less than ULTRA reliable. I would venture to say (though this is conjecture on my part) that the vast majority of flight problems that happen in dual-deploy are the result of some sort of user error - things like faulty connections, not checking ejection charge lighters before use, not enough (or too much) ejection charge, poor battery mounting, poor sim calculations, recovery harness or parachute not packed well, no ground testing, etc. I've never had an altimeter simply not work, and it's rare that I hear about someone else experiencing it (though, it CAN happen, yes). But have I seen a flight problems (and rocket damage) due to faulty delays when using motor eject? - definitely, quite a bit in fact. In my experience electronic ejection is VASTLY MORE reliable, and my preferred method the large majority of the time.

Honestly, dual deploy is really not all that difficult to do. If you pay attention and are methodical about your pre-flight setup, it really is very reliable. Yes, there are a lot of things to consider and think about, but that's what makes this hobby interesting and fun! Don't be afraid of dual deploy and/or electronic deployments - they really do work.

s6

This. Electronics may require setup and ground testing buy they are very reliable especially with a safe battery setup and ematches. You can also usually use motor eject as a backup to deploy your drogue chute or run other types of flight tests.
 
In this case a guy was doing a L2 attempt. He used a G Wiz and for whatever reason it didn't detect launch, but he used motor eject backup. The rocket came down too fast and was damaged (only drogue deployed). It was really windy today so nobody really flew much at all. The guy who took me was going to cert but decided to call it off because of the wind. There were a surprising amount of parachute failure too, one didn't open at all, another basically had its shroud line ripped off. I saw a team wanting to do a rocket within a rocket (basically one big rocket, that launches another smaller rocket). No idea how it went. If anyone's there please post a video of it...

When I get my eggfinder TRS I intend to do a simulated dual deploy. Basically single stage deploy with motor backup, with another blank e match to use as "second stage". This is to see whether or not it works, if it works I can add on a payload section for the second stage.
 
If mounted upside down or possibly armed in a non-vertical orientation; it may do this....



JD
 
FYI on the TRS:

You have 2 battery inputs: one for Pyro power and the other for Computer power.
You have to use the LCD receiver to put it into launch mode.
Read the user manual a few times before flying it.
It is different than most altimeters.... and I've flown just about all of them.


JD

In this case a guy was doing a L2 attempt. He used a G Wiz and for whatever reason it didn't detect launch, but he used motor eject backup. The rocket came down too fast and was damaged (only drogue deployed). It was really windy today so nobody really flew much at all. The guy who took me was going to cert but decided to call it off because of the wind. There were a surprising amount of parachute failure too, one didn't open at all, another basically had its shroud line ripped off. I saw a team wanting to do a rocket within a rocket (basically one big rocket, that launches another smaller rocket). No idea how it went. If anyone's there please post a video of it...

When I get my eggfinder TRS I intend to do a simulated dual deploy. Basically single stage deploy with motor backup, with another blank e match to use as "second stage". This is to see whether or not it works, if it works I can add on a payload section for the second stage.
 
failure that I have had with any electronic were most of the time due to poor batteries.
Dual deploy works really well.
My advices would be
- do some ground testing with no ejections charges (replace them with bulbs) check your connections (shake your ebay when powered) and make sure all stays in place
- charge up your batteries and use good one
- do redendoncy with 2 altimeters from different brand
 
My only dual deploy failure was my fault. I didn't make my ejection charges properly.
 
A good ground test rig for me has been a Foodsaver with the marinating bowl attachment, i put the altimeter into the bowl with christmas tree light bulbs attached to the pyro connection points, pull a vacuum and watch for the "events". Then I hook it up to my computer and check the data for the "flight".
 
Dual deploy is very reliable, but you MUST ground test with the exact battery and igniter that you are going to use. Make a checklist, follow it religiously, test you batteries before you fly, and you'll be fine. Almost all of the dual deploy failures I've seen have been mechanical... chutes getting stuck in the payload bay, shock cord failures, too little BP, etc. The current crop of DD altimeters are ridiculously reliable... chock that up to better software due to experiences of the past. [Full disclosure... I make the Eggtimer products.]
 
That said, in my experience pretty much all currently available dual-deploy altimeters are nothing less than ULTRA reliable.

s6

Correct, which is why I don't understand the need for redundant altimeter setups. My 0.01% DD failure rate is due to things that a second altimeter would not fix (bad burrito wrap, shock cord mishap, poor battery holders, etc). Do it right, and one altimeter is all you need for basic flights. (I am not counting extreme projects, here.) Commercial ematches are also very reliable. Motor backup is good enough for me. Prepping one altimeter/ebay/payload is enough work as it is. I am not gonna do it twice!
 
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The vast bulk of all of my high power flights since about 2000-2001 have been dual deploy (there are a few simple flights of the Loc 4). This represents a lot of flights.

In that span I have had three flights have issues with dual deploy.

The first was my fault as it was my first dual deploy flight, I had go fever, and did not listen the continuity beeps. The drogue came out on que but the main did not open as it was open due to a wire working loose while packing the main chute. Lesson learned.

The second was having to small of an apogee charge, and the rocket coming in ballistic until the main blew. Nice zipper. Learned to ground test.

The last was last summer. Two things on this. It was drougeless, and I should have used two shear pins instead of one. Nose came loose and tangled with cordage between sections. Drogue would have likely prevented that. Then the main blew and it mostly opened, but was a bit tangled. Got away without damage on that one. Lesson learned- reconsider using small drogue a or possible streamers at apogee.
 
I've been flying DD since 1996, with over 300 successful flights (a guesstimate).

It's all in the preparation.


JD

I agree with JD 100%. All of the DD's I've seen fail as been user error. Take your time, don't get distracted, and double check everything.
 
Correct, which is why I don't understand the need for redundant altimeter setups. My 0.01% DD failure rate is due to things that a second altimeter would not fix (bad burrito wrap, shock cord mishap, poor battery holders, etc). Do it right, and one altimeter is all you need for basic flights. (I am not counting extreme projects, here.) Commercial ematches are also very reliable. Motor backup is good enough for me. Prepping one altimeter/ebay/payload is enough work as it is. I am not gonna do it twice!

Some issues a 2nd altimeter will alleviate:

Battery connection gone bad, vibration,wire comes loose,[ overzealous charge may cause at apogee], now you got nada for main.
bad ejection starter that passes continuity check
starter bridge wire burns without lighting pyrogen
BP fails to ignite.....it does happen! [to me twice...now that's a weird one]
Failure of one channel on other altimeter.
Switch bounce or disconnect on 1.
This happens to be the flight your altimeter decides to go haywire and cease working.
Some strange anomaly happens to one, but not the other.....[good reason for using 2 brands]
Allows for a larger back-up charge, first one fires NC or chute hangs & second charge pushes them out
Just a few things I have personally witnessed as failures.


Some of these can be handled with just one altimeter by:

using 2 starters per terminal so you have 2 in each charge.
using second set of pyro's for back up when altimeter has 4 pyro hook ups. [Not all altimeters have this capability]
Some you need a totally independent system to do. Wiring problem-failure of unit-battery issues


I agree with JD 100%. All of the DD's I've seen fail as been user error. Take your time, don't get distracted, and double check everything.

I probably have used way more units than most...over 100 by now. Currently 17 altimeters are mounted in various rockets.
I like having 5 rockets ready to fly and that's 8 units right there. 3 flight will use 2 on sled for 3in and above. 2 flight will use 1 @ sled for 38mm & 54mm airframes.

So far I have had these flights which I would not call user error:

3 G-whiz altimeters total fail during flight...landed beeping out ready for flight readings. They were returned and never fixed properly....why you have so many bad opinions about them. Go through here searching for the numerous threads on that.

2 Ravens: 1 fire charge one power up for staging pyro [igniter NOT in motor thank god.] New...never flown.
1 in a 2-stage total failure....beeping ready for flight upon landing. Flown several times before, new one sent, issue never determined

1 Missleworks old version, flown 55 times [used to keep a log] Beeped fine on pad, failed in flight. Sent in for repair, but BP residue had corroded board too badly. I no longer store altimeters on sled in rocket with out removing fired charges and cleaning tubes/bulkplates.
I suppose this one could be called user error. But it failed in flight after testing on ground. A second one would have prevented failure, which is being discussed here.

2 R-Das....tough call here. Both flew fine in different rockets had bad/hard landings, then flew fine for several other flights before failing in flight. Yes they passed the self test mode. So possible damage showing up down the road. 2nd back-up saved the day on both flights. Also returned/repaired and flew fine.


User error....not really, just anomalies that do happen where 2nd altimeter saved the day:

Battery box broke loose from wood sled at apogee from large charge....showing charge pulled -55G's...wood screws pulled from sled. I now use only bolts.

Wire ties holding battery on N-10,000 flight let go, battery clip wires broke.

Switch [key type] lost contact. Use twist & tape exclusively since.


I'm sure others have stories too. On the other hand, many fly just one altimeter and have had no issues.
 
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Correct, which is why I don't understand the need for redundant altimeter setups. My 0.01% DD failure rate is due to things that a second altimeter would not fix (bad burrito wrap, shock cord mishap, poor battery holders, etc). Do it right, and one altimeter is all you need for basic flights. (I am not counting extreme projects, here.) Commercial ematches are also very reliable. Motor backup is good enough for me. Prepping one altimeter/ebay/payload is enough work as it is. I am not gonna do it twice!

You never know what could happen until it does, even with rockets which have been flown before and everything is setup "perfectly"

[video=youtube;8kEMGniMe0g]https://www.youtube.com/watch?v=8kEMGniMe0g[/video]

Altimeters are so inexpensive these days there is rarely a good reason not to have redundancy.
 
You never know what could happen until it does, even with rockets which have been flown before and everything is setup "perfectly"

[video=youtube;8kEMGniMe0g]https://www.youtube.com/watch?v=8kEMGniMe0g[/video]

Altimeters are so inexpensive these days there is rarely a good reason not to have redundancy.
completly agree, and this video is a very good exemple
 
So what happened here? It looks like the body tube separated a bit but not all the way, then it eventually separated. Was the first ejection too weak?
 
Beautiful example! Redundancy saves the day!!!

You never know what could happen until it does, even with rockets which have been flown before and everything is setup "perfectly"

[video=youtube;8kEMGniMe0g]https://www.youtube.com/watch?v=8kEMGniMe0g[/video]

Altimeters are so inexpensive these days there is rarely a good reason not to have redundancy.
 
I have to agree with the others.

My DD failures (except for one) were due to deficiencies with the idiot writing this e-mail. As for the one failure not created by something I did (or did not do) were due to me using a brand-x altimeter instead of the very reliable Stratologger. Won't do that again!

Once you find an altimeter that works, stick with it!
 
As others have said, if you ground test your setup, make no changes to the setup for your flight, and follow the correct setup procedures preflight, you will be fine.
I use redundant altimeters on my larger birds. For smaller ones, I go with a single altimeter.
I guess I am old school, because when using redundant altimeters, I use different manufacturer's brands. It's nice to compare the post flight data between the 2.
Given the costs of our many of our rockets, not to mention the time and effort we put into them, comparing those factors to the low costs of altimeters these days, I don't understand how folks can not think these are one of the most worthwhile components we can employ. (along with trackers of course)..
 
Another reason for going with different vendors altimeters for redundancy is that it will eliminate some software bug from affecting both your primary and backup deployment controllers. It's not a very common thing, but it could theoretically happen.
 
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