“A design for the delivery of humanitarian food aid from an airborne platform”
Page 3
Release mechanism
My experience with release systems for sub sea work has provided several valuable lessons. Firstly a mechanical or electromechanical device is the most reliable. Second is the need to have a redundant system.
The above pictures show the release mechanism on the left hand side of the top unit. The close-up picture illustrates the double ended release bar. Should either end be triggered the bar will be released. Note the three cables attached to the release bar. The top one is connected to a streamer (or very small drogue chute), another to the parachute release pin and a third to the deployment bag located in the parachute storage pack.
Illustration of the streamer and initial release.
Parachute storage & deployment
The parachute is contained in a “D Bag” which is in turn stored in a quick release container on the top of the DBX. This outer container has been designed to protect the parachute during ejection from the aircraft and will also prevent the parachute from opening prematurely. The “3 triangles” system is secured with a single release pin connected to the release bar.
During deployment the bar is released, the pin is withdrawn and the D Bag pulled from the container. The D Bag is released from the parachute and the parachute starts to inflate. At this time the parachute lines will release the toggles and the DBX will be ready for package ejection when the lines fully extend.
The following figures illustrate the deployment sequence.
Stable descent
Release triggered + parachute pin removed
D Bag pulled from parachute box
Parachute ready to inflate
Parachute deployed
Both side toggles released
Front toggles released
Detail of front & side toggles. Side toggles are released from inside the DBX, wires shown for illustration. Cable exits from slot in top of DBX. Front toggles are released from outside the DB as it would be impossible to close the “lid” and secure the toggles from the inside.
Rear of the DBX showing position of webbing straps, these carry the weight of the DBX during package ejection and transit to the ground.
Sequence as webbing straps take the load.
The DBX is no longer a container at this point and it is possible that the DBX will open up due to the descent velocity. This could well be in the order of 200mph so the illustrations are hypothetical.
The point at which the web straps take the load poses an interesting question. What weight will they have to take ?. Theoretically (if the DBX is still in the form of a container) there will be some load as the contents force open the base but I feel this will be minimal. I think the actual load will be the weight of the empty DBX + deceleration. I will incorporate a strain gauge in the webbing connections to measure this force.
Final stage of package delivery.
