Recipient Operated Search & Rescue Supply Dropper

Recipient Operated Search and Rescue Payload Delivery Mechanism for DJI Phantom 4


Description
This device is designed to provide a way for Search and Rescue personnel to deliver a payload to a person in need of rescue while they wait for the S&R team to reach the location of incident. It is recipient operated though the use of a long release line hung below the Phantom 4. This design allows the user to bypass the risk of landing near they recipient altogether. Landing in terrain is hazardous to both the recipient and the aircraft and present a potential loss of control signal issue. 

Payload Size
~115mm x ~70mm x ~45mm
This version accommodates small payloads in attempt to minimize effect to the DJI Phantom 4’s flight time. Ideal for small payloads like a 2-way radio or first aid supplies. The mechanism can easily be scaled for larger multi-rotors like the DJI Inspire. I plan to design a larger version for larger multi-rotors at a later date. Also a larger version that mounts to the bottom of the DJI Phantom 4 to accommodate bulkier payloads can easily be modified. Great care should be taken to not overload the Phantom, not only for flight time, but more importantly for the safety of the those involved in the drones use.


Possible Use
Deliver supplies to a person in need of rescue while they wait for the S&R Team to reach them.
- 2 way radio. To determine further needs that can be air dropped. First Aid supplies
- First Aid Supplies. To include additional supplies the S&R team may need after getting to the person
- Strobes or marking flairs/smoke for helicopter landing
- Other Interim Supplies. Water, food, space blanket, etc.    

Assumptions
For this application and design contest the DJI Phantom 4 is the focus. I am assuming that the intended recipient of the air drop has already been located but not recovered. The search and rescue team may be preparing to depart or is already on the way. Possibly a manned or unmanned fixed wing aircraft or even another Phantom 4 with a FLIR camera was used to locate the victim.

Components
Carrier – Attached to the rear underside of the DJI Phantom 4 by clipping to the landing legs. The main purpose of the carrier is providing a mounting point for the release mechanism and the delivery payload.

Release Mechanism – Mounted to the Carrier, the release mechanism holds the Payload Tray until it is ready to be deployed. The mechanism releases the payload tray when a pin attached to monofilament line (fishing line) is pulled by the recipient of the air drop. The line remains attached to the dropped payload tray to aid in retrieval. If the person in need of rescue has limited mobility they could then pull the delivery over using the still attached release line.

                         
Release Line – Use at least 30 feet of fishing line. Using a release line overcomes 3 issues with multirotor drones use in Search and Rescue application. 1) The landing phase of multi-rotor drone flight is by far one of the most hazardous and potentially dangerous phases of flights. Un-even terrain further complicates landing. Trying to land a multi-rotor drone near a likely injured person poses a hard to both them and damage of the aircraft itself. 2) The same terrain that could make for a tricky landing could also block or degrade control and video signal to the aircraft, making landing difficult if not impossible. Having a release line of 50ft or more greatly enables the aircraft to maintain line of sight to the drone operator. 3) The DJI phantom 4 does not have an auxiliary channel that can be used for mechanical remote controlled release. Many first responders that use drones like the DJI Phantom 4 do not want to have to buy and install a separate 3rd party control device. This delivery scheme is as simple as attaching the carrier mechanism, strapping on the needed cargo and flying to the person(s) in need. 


Release Line Weight/Hook – Attached at the end of the release line, it serves as both a weight to keep the line below the drone. The recipient would pull on the weight to release the payload. The hook can also be snagged on a nearby object in the event a payload needs to be dropped that doesn’t need to be retrieved by the search and rescue recipient. IE: Location Strobes to make the incident area more visible to other aircraft, like a landing helicopter.  

Payload Tray – Designed to accommodate payloads in a size category that will not affect the overall size footprint of the DJI Phantom 4. Items intended to be delivery would be strapped to the payload tray. When the payload is released a small parachute is also deployed to help slow the descent and aid in visual acquisition.

Parachute (Optional) - A simple plastic parachute like those used in model rocketry can be purchased anywhere where model rockets are sold. Just tie the chute to the payload tray and lightly fold it so it does not bind or get tangled in flight to the recipient. If item is rugged and can survive a fall, wrap foam type material around the item for added projection from harsh unintended impacts.

Payload Mount Recommendation
The Payload tray has slots in it to accommodate hook and loop cable straps. Insure whatever you are attaching will be secure enough for flight but not too difficult to remove for the recipient. For loose items ziplock bags work well. For fragile items construct a small foam box and attach as desired to the payload carrier

Assembly Recommendations
Insure the payload tray can freely fall away from the payload carrier when the pin is pulled. Drilling out guide hole may be needed. Also make sure the release pin will pull out easy enough for the recipient but not so easy the weighted hook pulls it out on takeoff. 

Design Disclaimer
I designed this using measurements from the a DJI Phantom 4 model provided for use in the SAR3DP contest. I only had limited access to a real Phantom 4 for about 30mins at a local retailer to get measurements. Some things may not fit perfectly. In the event I get my own Phantom 4 the design will be updated accordingly.

The design blocks the Phantom 4’s bottom facing optical flow sensors. The flow sensors should be disabled if using this mechanism. I am not 100% sure if this is an option. If it turns out disabling the sensors is not possible I will redesign the mechanism. 


Video Description
This short clip shows a test release mechanism I flew on my race quad-copter since I do not have a Phantom to use. The video shows the quad climbing until the release cable is tight at which point the line pulls the pin releasing the mechanism and dropping the payload. In this test the payload was a real 2 way radio. 

I was only able to get one test video recorded before the sun went down, but Ill be making updates on a 2nd product page.