How to choose a UAS Parachute Recovery System

How to choose a UAS Parachute Recovery System • Why you need it – Safety, Regulatory, Insurance, Loss Mitigation • Deployment Methodology – Active (Ballistic), or Passive • Sizing the parachute for your UAS • Other components needed

Who is Fruity Chutes Started for hobby rocketry recovery in 2007. Rocketry recovery is very demanding in terms of harsh recovery situations – high speeds, altitudes, stuff goes wrong a lot! Strength very important. � Began to sell to emerging s. UAS users around 2009. � s. UAS now outpacing other industry segments for need for Parachute Recovery Systems (PRS). � Sold well over 1000 UAS systems to large range of customers. Many companies are integrating now. �

Some Marque Customers…

Why do I need a Parachute? � Drivers toward the need for Parachute Recovery Systems (PRS) › Safety – Protect people and property. › Regulatory – Not lost on government agencies is backup safety systems make since for public safety. › Insurance – Insurance companies drive need via lower premium rates or even mandate to get insurance. › Cost of Failure Mitigation – Parachute safety is a fraction of UAS costs in case there is a failure. › Business Continuance – A bad crash can put you out of business. Also you can suffer complete data loss for your flight.

Different UAS need different deployment methods � Broad classes of UAS need different solutions: › Fixed Wing system can use passive deployment or ballistic deployment. › Multicopters or helicopters need some sort of Ballistic Parachute. Since these can hover and have high speed rotors the parachute needs to be ejected out and away from the copter.

Fixed Wing Passive UAS Recovery › Passive deployment relies on forward flight and air velocity for extraction › Used mostly for Fixed Wing UAS › Small pilot chute used for extraction of the main parachute usually in a deployment bag › Simple and low cost › Not suitable for Multicopters!

Ballistic Parchute Deployment � These systems eject the parachute at velocity so it clears the UAS quickly � Deployment by compression spring, CO 2, or even rocket � Large systems used on full size aircraft � Reliable deployment under a wide rage of flight conditions including from hover to forward flight.

Compression Spring Ballistic Parachute Launchers Examples are Skycat Launcher, and MARS systems. Ballistic deployment does not require forward flight – ideal for Multicopters. � Relatively low cost. � Limited in chute size by spring strength. � Can use with larger chutes by ejecting smaller chute which acts a pilot for larger chute, but this delays deployment. � �

CO 2 Ballistic Systems Examples are Peregrine UAV, Peregrine IDS, DJI Dropsafe. Active ejection using CO 2 gas, more energetic, move out and away quickly, faster deployment time. � Peregrine systems rated up to 100 Kg loads. Features high packing density, resulting in small size and light weight. � DJI Dropsafe features almost instant parachute opening. But the parachute ties directly to the copter leading to stability issues (bad oscillation). Also if the copter is rotating the chute will quickly wrap around the copter. � �

Next the proper size chute is needed � After identifying the deployment method the parachute size needs to be determined. Just a few questions need to be asked to size a parachute: › Weight – This tells the size system needed › What is the estimated speed at deployment – If high this can narrow the parachute choices to higher strength versions. › Is it for primary or backup recovery – For Multicopters a parachute is virtually always for backup recovery. But Fixed Wing can be either. When the parachute is a primary recovery device the expectation is there will be minimal to no damage upon landing. So you need to be more conservative. A 4. 6 m/s or so descent rate is a good number to go for low to no damage. Backup / Emergency recovery can sometimes be more aggressive, sometimes up to double the weight of the nominal 4. 6 m/s rating. For example the IFC-60 S chute is rated at 5 Kg @ 4. 6 m/s. As an emergency rated chute it can be used in systems up to 10 Kg. For emergency use you can accommodate up to double the nominal load rating.

Having the right descent speed is important! � Having too high and too low a descent speed can be a problem: › Obviously too high a speed will result in damage. › Not as obvious, too slow can also be a problem. After landing the wind can cause the parachute to drag the payload and cause a lot of damage.

Now size the parachute � To determine the physical size of the parachute you only need three terms: 1. Recovery weight 2. Target Descent Speed 3. Cd of the parachute. The Cd is inherent of the parachute design chosen. For most UAS the Annular parachute style gives the best performance in the smallest possible canopy style. The Fruity Chutes Iris Ultra parachute is an example of this. The Cd referenced to projected area is 2. 2.

You can calculate the canopy opening projected area (Ap) � Here is the formula to determine the canopy opening area in Sq feet Ap = (2 * W) / (rho * Cd * V) Ap – Area projected in sq feet W – Weight in lbs rho – 0. 00238 slugs / cu feet at sea level Cd – Based on chute design, from 0. 7 to 2. 2 V – Velocity of target descent in feet per second

Formula to determine descent rate � Use this formula to determine a parachute descent rate: V = sqrt( (2 * W) / (rho * Cd * Ap ) ) V – Velocity of descent in feet per second W – Weight in lbs rho – 0. 00238 slugs / cu ft at sea level Cd – Based on chute design, from 0. 7 to 2. 2 Ap – Area projected in sq feet

Choose your chute � Once you have the chute area you can convert that to diameter and choose your parachute model with the closest manufacturer’s size. A few things to keep in mind: › The Cd can vary depending on local conditions. The Iris Ultra annular chutes can vary from as low as 1. 9 to as high as 2. 9. › This directly affects the descent speed per the inverse square law.

Other Recovery Products Needed � Some other products are also needed beside the parachute: › Harnesses – These are relatively short cords to connect the airframe to the main riser (shock cord). There are usually from 2 – 4 harnesses to provide a multi-point mount. › Main Riser – This is used between the harness assembly and the main parachute. It’s critical to provide separation between the parachute and load in order to have maximum stability under descent. This also increases the efficiency of the parachute. › You need to interconnect the rigging. Quicks are a good way to go. It is NOT a good idea to tie knots, these weaken the cords by up to 30% or more.

How do you integrate the recovery system to a UAS? � There is no single answer to this, and how the parachute system is integrated varies widely on the UAS. � System generally placed near the Cg of the UAS. � Harnesses and cords need to be secured to the UAS, but allowed to be easily torn away when the parachute ejects. This can be as simple as using masking tape to bundle and secure the rigging.

Multicopter considerations � Canister usually top-side. Parachute ejected over the top of the UAS. � Three or four point multipoint harness so the copter hangs level. � If you have a very high value sensor below the copter (like LIDAR) you might put the recovery system underneath and belly deploy and land the copter upside down to save the payload.

Fixed Wind Considerations Similar to Multicopters in may ways. � Recovery system can be stowed in a compartment under a hatch � Pilot chute egress must be a clear path to avoid things like a pusher prop, or the tail section. � Many fixed wing recovery systems use belly deploy to land upside down. Textron Shadow and Aerosonde are examples. The airframe is considered expendable, the payload and sensors underneath are not. �

Questions?

Further Information: � Download this presentation here: http: //fruitychutes. com/genes_blog/usb-expo-chooseuas-parchute-system. htm � Parachute Recovery Tutorial: http: //fruitychutes. com/uav_rpv_drone_recovery_parach utes/uas-parachute-recovery-tutorial. htm � Gene’s Blog, articles on recovery and other stuff: http: //fruitychutes. com/other_fun_stuff/genes_blog. htm THANK YOU!