wiki/ news/ 2012-09-25 - New main parachute bag testing

New main parachute bag testing

Since the parachute bag for the main chute tore during last year's motor failure, we had a new bag manufactured. A couple of things were slightly different this time, and even though it packed up just fine it seemed prudent to test the chute coming out.

  1. New main parachute bag testing
    1. First drop
      1. Snag
      2. Inspection
    2. Drop 2-3
      1. Snag
      2. Inspection
    3. Drop 4
      1. Results
    4. Recommendations:

First drop

The chute was packed like usual and had been sitting on the shelf in the bag for about a month. We took it out and attached about 2 kg of mass in a canvas bag to the shroud lines. We set up on the staircase in the atrium of the engineering building. One person held the top of the parachute bag and another held the weight bag with about a dozen cm of slack and then dropped it. The total fall distance was about 10 meters.

Snag

The shroud lines came out very quickly and smoothly, but the little piece of line that holds the flaps that keep the chute in snagged and the falling weight pulled the whole thing out of holder's hands. The still bagged chute fell all the way to the ground.

Inspection

The fallen bag:

Looking at the bag, there was a tiny bit of line left in the loop holding the bag closed. This piece of line appeared to pull out cleanly when done slowly by hand.

We put the line back in the loop and tried again.

Drop 2-3

We tried two other drops with the shroud lines already out, giving the weight bag about 20 cm of slack before dropping it to create some opening force.

Snag

In both cases the bag still did not open.

Inspection

The same thing happened in each case, the last little bit of shroud was stuck in the loop. We tried moving the loop point further towards the base of the shroud lines, but it made difference.

Drop 4

In the last trial we changed the direction that the loop was attached. We noticed that the line was letting the flap be pulled open which put more compression on the loop, likely a run away effect that was binding the bag shut. We reversed the direction that the loop opened and reset our test.

Original loop direction:

Final (working) loop direction:

Results

This time the chute came out cleanly. We did not have the high speed camera with us this night, so there isn't much we can see in the video, but it did come out cleanly the last time.

Recommendations:

This should be looked at closer, with perhaps another test with the high speed camera with the loop in both directions to confirm that there is a preferential direction and that it will open cleanly in flight.