Main reason for failing Cert flights?

NateLowrie said:

Tradeoffs:

• Cost. It costs you $130 or $260 if you do DD and that is in addition to any traditional electronics for apogee.
• The biggest risk that I have seen with the chute release after observing them at MDRA for the better part of a few months is that the chutes take a while to open. There have been several drogueless rockets that have gotten pretty beat up because of the chute doesn't deploy properly. This might be due to the folding of the chute and easily remedied, but I see a bigger risk for tangling and slow opening here. To me, this is a tradeoff because it's a riskier proposition than using a deployment bag.
• There is a risk the chute will dump at apogee from it not being packed right.

Now, that said, it offers advantages that in most cases outweigh the negatives. I think it's a really good choice for L1 and L2 rockets that utilize motor ejection. It allows you to turn a single compartment rocket into a DD rocket with no modification to the airframe. When you start doing electronic deployment at apogee, the choice is less clear.

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Fold the chute like shown at the Jolly Logic site. Attach the chute release and wrap the chute protector around the whole shebang. Here is the kicker that will really help with the deployments. Make doubly sure the chute protector is attached to the harness closer to the open end of the sustainer and the parachute is attached closer to the nosecone. In this way, when the assembly is ejected, the JLCR/chute pulls free of the protector and is out in the open. Kurt

I don't get this delay in opening thing. I tri-folded my chute really tight. When the chute release deploys, the chute springs open with authority. I think any delay would be an error in packing the chute.

Motor deployment isn't as accurate as electronic deployment. You are depending on a delay grain that sometimes burns too slow or too fast (The latter, ask some people who use Aerotech motors). If the motor deploys too soon, you zipper and you tear up your chute. If both are severe, you can fail your cert. If it deploys too late...same thing. In both cases you can also lose a fin. Again, cause for failure. And if you are using a V-Max motor, you can snuff out the delay charge and ultimately dig a nice core sample.

I have gone to at least electronic apogee deployment, using the motor charge as backup.

grouch said:

I don't get this delay in opening thing. I tri-folded my chute really tight. When the chute release deploys, the chute springs open with authority. I think any delay would be an error in packing the chute.

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What I observe is if the the chute protector is close to the attachment point of the parachute, the chute can hang in the chute protector. One wants the chute/JLCR pack free from the protector after ejection from the rocket.

I've see chutes hang in the chute protector even with apogee only deployment events. One needs to get the chute out of the protector when the protector is not needed anymore.

As an aside, I had a Rising Star Payloader have a very unusual recovery with the stock plastic parachute. Darnedest thing I ever saw. I put an "F" something or other motor in the rocket with a long delay and launched it on a cold but not freezing winter
day. The rocket had a nominal apogee deployment "way up there" and was coming down fast. We had a good angle on the rocket and it appeared the chute fully unrolled but was staying taut and the canopy was closed. The rocket descended lower
and the canopy slowly fully opened like a flower. The comment was made, "Was that a dual deploy?" It was only in appearance. Nice thing was I didn't have to walk far and on inspection of the plastic, stock parachute, the chute was absolutely fine.

Bottom line is the aerodynamic forces can keep a chute from making it out of a chute protector OR a poorly designed deployment bag. With the JLCR, getting the chute protector closer to the open sustainer end and using a piece of duct tape to stick it on the harness allows the chute pack to pull free with authority. The chute release just has to spring open and the chute will come out quickly. Kurt

Where is. This check list you where going to post, I've been waiting so I can copy it!

Ahhh! SORRY! Calc test today, been studying for that.

OK, checklist:
1/(1+x)=1+x+x^2+x^3.... OH SORRY! Wrong checklist.


Here it is:
CHECKLIST

Not that I have much experience failing flight tests. I've only tried to certify once past once. BUT my L2 I'm going mile high x2 electronics first tracking first MD high power first. All first. I imagine it's a good way to fail a cert test. But I'm going for it anyway

tangled chutes, zippers, and ejected motors are common ones I see. Don't wrap your chute in the shroud lines, make sure the delay is right if you're using delay, and make sure that motor isn't coming out. punch it

Let me be the first to congratulate you on successful L-1....
FINALLY BlackBrat is certifiable!!!!!! :wink:

Even though he made the club stand around in the pouring rain, with just one lonely little pad waiting for him to prep

[an hour? for L-1 prep?] and get it on the pad. Everything put away, so they could get out of the deluge.

Are we bit wet, literally, behind the ears. I'll give you this......you're a tenancious little bugger.

Should have pulled a "Ben" & tied a wire on the rocket, flown it into clouds and hung on to the key!...LOL

blackjack2564 said:

Let me be the first to congratulate you on successful L-1....
FINALLY BlackBrat is certifiable!!!!!! :wink:

Even though he made the club stand around in the pouring rain, with just one lonely little pad waiting for him to prep

[an hour? for L-1 prep?] and get it on the pad. Everything put away, so they could get out of the deluge.

Are we bit wet, literally, behind the ears. I'll give you this......you're a tenancious little bugger.

Should have pulled a "Ben" & tied a wire on the rocket, flown it into clouds and hung on to the key!...LOL

Click to expand...

Well, just to clarify, I spent about 30 minutes prepping the rocket and the other 30 minutes finangling with my masking tape that decided stop working just as I started setting up the rocket, warming up my fingers to the point where I could handle the screws and nuts, and waiting for a window in the clouds to open.

But anyway, thanks a lot!

For anyone reading this thread, a checklist helped a TON.

Windy day and a rocky landing zone.(broken fin) Other than that a perfect flight. Nothing fancy, only motor deployment.

From what I've heard, the most common cause of cert flight failures is in the recovery system, as others here have mentioned.

But don't forget that CATOs are another reason for failure, particularly if the flier makes the mistake of choosing an Aerotech DMS motor (see here). As far as I know, Aerotech and its vendors (excluding Apogee) continue to market "first" iteration" (aka defective) DMS motors, which Aerotech itself concedes are relatively prone to CATOs, something I've posted about elsewhere.

Fly Aerotech DMS at your own risk.

Best of luck in your cert attempt. Let us know how it goes.

Buckeye said:

...
24mm and 29mm RMS also teach you how to assemble a motor by reading 3-point font instructions printed in greyscale by Aerotech.

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I agree that the 3D drawings packaged with the reloads are sub optimal. I downloaded all of the AT RMS motor assembly drawings from their website and put them in one multi-page PDF. The PDF is on my tablet and when I go to assemble a reload I just open up the PDF and scroll to the page with the applicable diagram. I find the 2D diagrams to be far easier to read and like the parts list legend on the right side.

I have personally witnessed two failed L2 tests. None for L1 or L3. Both failures were the exact same thing on different days. Unsecured batteries that came loose thereby rending the altimeters and their associated charges nothing more than expensive time capsule components inserted into the earths crust with considerable velocity.

Seriously, 50 cents (cue some rap music please) worth of plastic would have saved two beautiful fiberglass rockets, some shame and some tears... Not to mention reduced risk to those on the ground...

As I read this thread it occurs to me that another major cause for failing the cert is "Go Fever". Continuing with the attempt when it would be better to postpone it to a day with better conditions or when things are not as rushed, often leads to failure in my experience.

terryg said:

As I read this thread it occurs to me that another major cause for failing the cert is "Go Fever". Continuing with the attempt when it would be better to postpone it to a day with better conditions or when things are not as rushed, often leads to failure in my experience.

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I intentionally set up a long check sheet for my L3 last week. I'm very susceptible to go fever unfortunately and following a list developed in a calm environment keeps me cool.

terryg said:

As I read this thread it occurs to me that another major cause for failing the cert is "Go Fever". Continuing with the attempt when it would be better to postpone it to a day with better conditions or when things are not as rushed, often leads to failure in my experience.

Click to expand...

I had really bad Go Fever and it manifested itself into rockets that had parts of constructions rushed and half-assed. It specifically led to 3 failures back in the day and when I started again I vowed I wouldn't sucker myself into the trap again. My pre-launch packing and prep checklist has a specific entry where the team and a 3rd party observer discuss the flights and the readiness of each flight. If steps have been rushed and are not done to spec, if required testing hasn't been performed, if the flight isn't properly pre-prepped, or if anyone has issues/concerns about that flight, it doesn't launch until the problems are sorted and everyone signs off. It sounds like overkill, but it works well and I definitely will be leaving it in for any rockets that I fly.

blackjack2564 said:

Let me be the first to congratulate you on successful L-1....
FINALLY BlackBrat is certifiable!!!!!! :wink:

Even though he made the club stand around in the pouring rain, with just one lonely little pad waiting for him to prep

[an hour? for L-1 prep?] and get it on the pad. Everything put away, so they could get out of the deluge.

Are we bit wet, literally, behind the ears. I'll give you this......you're a tenancious little bugger.

Should have pulled a "Ben" & tied a wire on the rocket, flown it into clouds and hung on to the key!...LOL

Click to expand...

think I better warn the guys at UAH and PMW/HARA,,,

fm

HARA's the one that's gotta worry