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Gary73

Student AAD Firings

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Student AADs are supposed to fire at 1,000 feet at descent rates over 29 MPH to protect students who haven't cutaway from a malfunction that's fast enough to hurt or kill them but isn't anywhere near the 78 MPH firing speed of an expert AAD. Unfortunately, that speed range can easily be reached by performing spirals or making fast descents in the plane, which can result in an undesired and possibly dangerous two-canopy-out situation. I've seen several cases of the latter over the years, but none of the former. What I'm wondering is how often student AADs fire for the intended reason instead of the unintended one. So if any of you have actually been on the dropzone when a partial-malfunction student AAD firing occurred, I'd appreciate if you would tell us about it. Please also give an estimate of how many "undesired" student AAD firings you've witnessed. Thanks.

"Extraordinary claims require extraordinary evidence." - Carl Sagan

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I don't know of any student cypres fires under canopy at our dz, might have been some but I think we had more problems with fxc's.

Then again, last year I say a SL student doing stall turns (!!) on a manta 288 or skymaster 280, down to 90ft or so then let up and land :S "What? Not allowed to do that? F-X-what?" The guy was a paraglider too.... Guess a student cypres WOULD have fired :o

Some of the rental rigs from the shop next door have student cypres, I know these are now only rented out to STUDENTS not heavier experienced jumpers anymore, because of a few problems :S


ciel bleu,
Saskia

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While I have no experience in seeing an AAD fire I do have a suggestion. I know the vigils store the descent data from the last 10 flights. Why not regularly download this data and determine how far from the limit each flight has been. I assume the manufacturers did some extensive testing to determine the proper cutoff on descent rate.

One other point I learned from a technical discussion with my rigger is the importance of leaving the brakes set on a reserve should it come out along with the main. This was not taught in my FJC and I'm not sure why... Any comments on that?

-Michael

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Hi,

1. Two years ago at my former DZ there was an AAD fire under fully inflated/steerable canopy (PD Navigator 280). The student did sharp 360 degree turn at approx. 1000ft maybe a bit higher. He was a really big guy (205cm/6ft 9" - 115kg/250lb). AAD fired, he realized reserve is opening, did cutaway and opened reserve (RSL), landed OK.

2. I also saw one AAD fired on the ground, but due to the fact that the data from the AAD differs from what i saw and heard while standing one feet away, and the fact that everybody trusts the machine, i will not write more details about this.

On the other hand couple of weeks ago I witnessed two real saves by AAD.

blues!
dudeist skydiver #42

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29mph is (42 feet per second) or 2500ft per min, how many jump planes decend this quickly, especially below 1000ft?

Have there actually been cases of a student AAD firing due to decending in the plane? (With modern AADs rather than FXC or other older AADs?)

I'm curious, how many places insist on a student cypres being switched off for the decent?

I've only seen one AAD fire on a student... and it did it's job perfectly! I haven't seen any "undesired" firings with modern student AADs

Edited to add: Was a student no-pull and not a partial malfunction


Don't sweat the petty things... and don't pet the sweaty things!

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First of all, it is considered bad form for jump planes to descend rapidly below 1,000 feet.
At most airports, the traffic pattern starts at 1,000 feet AGL and flying fast below that scares other pilots.

Secondly, I have had an FXC 8000 fire in my lap, while the plane dived through a hole in the clouds.

Most schools tell instructors to turn off AADs before descending with students in the plane.
The better schools tell their pilots to reduce rate of descent below 2,000 (to avoid scaring tandem AADs).

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Have there actually been cases of a student AAD firing due to decending in the plane? (With modern AADs rather than FXC or other older AADs?) - Altichick



From the CYPRES manual:

If a jump plane is descending without having dropped, switch the Student CYPRES off!

Unlike the Expert CYPRES models, we recommend that the Student CYPRES be switched off in the aircraft prior to descent if the jump is aborted and the student will land with the plane.

Be aware that it is possible to exceed a vertical speed of 29 mph under a fully inflated canopy!


The problem is that once the descent begins, the AAD doesn't want to shut off, which is understandable. In that case, it's very important to tell the pilot to keep the rate of descent less than 1000 feet per minute below 2,000 feet AGL.

I''ve been on the DZ for at least four such cases with student CYPRESs. Everything stayed in the plane; no injuries. A few years ago, however, there was a fatality (in Europe, I believe) when a student AAD fired and pulled an observer (or maybe co-pilot?) out of the plane. The AAD functioned exactly as documented; it just wasn't used as intended.

So yes, unintentional firings do happen. What I'm trying to get a feel for is the proportion of intentional (partial malfunction) student AAD firings to unintentional ones.

Please don't misunderstand me here: AADs save lives. I have two rigs, both have (Expert) CYPRESs,
and I wouldn't have it any other way. But at the same time, every safety feature has drawbacks which must be understood in order to be minimized.

"Extraordinary claims require extraordinary evidence." - Carl Sagan

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I'm usually at a fairly large static line DZ with FXC's on their gear. I don't recall or recall any talk about any unintended FXC firing over the last 5 or more years. (The exception was one FXC that went bad and fired while the student was flying around at normal descent rates.) Student AAD's are turned off in a descending plane.

When the DZO was looking at expanding the range of rental rigs available, I did a few test jumps with a bag of 3 FXC's. I couldn't get any to fire when doing toggle spirals at a 1.3 wing loading on a Sabre 135, but two went off at 1.4 wing loading.

(However, I only did a single jump at each wing loading. In the spirals I was trying to achieve by feel the fastest possible descent. )

The tests gave some assurance that even for a lowly FXC, even when trying hard to fire them, it can take quite a high wing loading to get that to happen.

I don't have the FXC firing specs in front of me but another post by an experienced rigger suggested 40+ fps (approx 28 mph).

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I did a few test jumps with a bag of 3 FXC's. I couldn't get any to fire when doing toggle spirals at a 1.3 wing loading on a Sabre 135, but two went off at 1.4 wing loading.

(However, I only did a single jump at each wing loading. In the spirals I was trying to achieve by feel the fastest possible descent. )

The tests gave some assurance that even for a lowly FXC, even when trying hard to fire them, it can take quite a high wing loading to get that to happen.

I don't have the FXC firing specs in front of me but another post by an experienced rigger suggested 40+ fps (approx 28 mph).



Descent rate faster than 65 fps (approx 45 mph) MUST fire.
Descent rate slower than 40 fps (approx 27 mph) MUST NOT fire.
Between 40 and 65 fps may or may not fire.

Allowable firing range + 300 feet, so may fire as low as 700 feet below the preset altitude and still be within calibration limits. (I'm guessing you set the altitude to 3000 or 4000 feet so you wouldn't have to worry about spiralling through 700 feet.) The + 300-foot range also applies to the freefall speed test, 175 fps (approx 119 mph).

Mark

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Many years ago (1993 if I remember well), we had a Cypres Student fire when the pilot of our Cessna 206 lowered the flaps in final approach before landing. The parachute was on the back of a passenger and the pilot chute exited the cargo door and pulled the passenger out at a (very) low altitude. Fortunately enough, she was just slightly injured (broken clavicle bdue to the contact with the door frame) as the reserve opened quickly without interfering with the plane tail. In that time the warning instruction asking to shut off the Cypres Students before landing with the plane was written in small letters in the Cypres booklet. Later on, when similar firings occured, happily most of the time without injuries, the writing in the following editions of the Cypres Instruction booklet appeared in bold than in bold bigger and bigger, with additional Caution marks.
I only know about one firing in Germany where the passenger was also pulled out but unfortunately the reserve get caught in the Pilatus tail and the plane went in killing the pilot and the passenger wearing the parachute.

On an other opportunity, we had a plane with 6 students on board (Cessan Caravan with a roll door) that had to land on an other airfield due to the bad weather. The jumpmaser did not switched off the Student Cypres' and it resulted in 6 reserve popping out at the same time within the plane, with no problem as, as said, the door was closed. The only one who was more than embarrassed was the jumpmaster when they came back to the drop zone, who had to explain to me (the rigger) why I had to repack 6 reserves [:/].

As far as Student modern AAD's firing due to spiraling under an open main, I only have seen it once, but the jumper had already quite a few jumps and was jumping again after a stop (and that is why he was using a student gear). When FXC's were used more extensively, I have seen quite a few firing under spiraling canopies, often with jumping having some paragliding experience, and it hapened more often withe the European version of the FXC that was activating at slightly lower descending speed than the original FXC.

To come back to the modern AAD's in Student configuration, all manufacturers precise clearly in their instruction manuals that they must be switched off if it is intendended to land with the airplane (but it is for sure still a good practice warning the pilot to avoid high descending speed under 2500 ft) but they also recommend that the control unit for student gears should be easily reachable without removing the equipment (on front main lift web or on the ouside of the yoke).

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Allowable firing range + 300 feet, so may fire as low as 700 feet below the preset altitude



Care to explain your math here. +300 feet means just that. 300 feet above the preset to 300 feet below the preset.

Our student/rental gear has a mixture of AAD's, including several FXC's and I have never seen any of them fire because of spiraling. As someone else stated he should do, our pilot slows his descent if there is any jumper still on board, never a problem so far that I know of.


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Allowable firing range + 300 feet, so may fire as low as 700 feet below the preset altitude



Care to explain your math here. +300 feet means just that. 300 feet above the preset to 300 feet below the preset.



That would be the kind of math I do when I type faster than I think.

What I meant to write was that at the lowest allowable setting of 1000 feet, actual firing could be as low as 700 feet for a unit within calibration limits.

Sorry.

Mark

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Here in Norway we teach 3 rules to all students. Below 1500f they're not allowed to turn more than 180 degrees in each turn. Then at 500f when they are starting their final, they're not allowed more then 90 degrees turns. When they reach 200f, they are not allowed to turn, just make minor corrections to avoid trees and other not-so-cool-objects-to-land-on. The last rule here is mostly to prevent turnings them selves into mother earth. However, the first two rules are there to avoid cypress/FXC firing. Are they teaching the same in USPA?

Three weeks ago we had a double fire while descending. the JM forgot to turn them off =)
"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return." - Da Vinci
www.lilchief.no

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I am not sure about USPA, but on DZ where this happened (Bosnia), rapid maneuvers limit is 1000ft, then 90 degrees until 300ft and minor correction below. This event was at about 1000ft borderline. Also you know how students are like, sometimes they have brain-lock or just late in reactions.
1/2 - 1 second longer turn under Navigator with a 120 kilo guy...
dudeist skydiver #42

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When I was a student none of the rigs were fitted with "Student AAD" They were all "Expert" model Cypress's for this very reason.



That was the practice here also. But the new law (about skydiving schools/training centers) issued here states that: "...during student training, operating mode of the AAD must be set accordingly (student mode)."
dudeist skydiver #42

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