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 is very important.

Began to sell to emerging sUAS users around 2009.

sUAS is now outpacing other industry segments in

need for Parachute Recovery Systems (PRS).

Sold well over 1000 UAS systems to large range of

customers. Many companies are integrating now.

Earned a place as a topic expert!

Some Fixed Wing systems need PRS – they are primary or backup recovery.› Examples, no landing gear, PRS is primary recovery

› Limited space to land, i.e. in the mountains or rugged terrain.

Other 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 sense 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 cost in case there is a failure.

UAS Systems not fool proof, they fail.

And any system, even with redundancy,

can also fail.

Can be mechanical, electrical, software,

environmental – think wind, rain, etc.

Failure result usually similar, impact into

the ground!

People can be hurt, and property can

be damaged.

Government agencies primary driver is need to protect

the public.

They recognize even the best systems can fail.

Safety systems like parachutes greatly lessen risk of injury

or property damage. But PRS are not perfect either.

Still, UAS with PRS have statistically much better

outcome than not!

Many EU countries now mandate. Australia, and some

South America countries do as well.

ASTM F38.02 subcommittee WK37164 is working on

safety standards for commercial use over populated

areas. Parachute safety is part of the standard.

Insurance industry driven by risk

assessment vs cost of claims settlement.

PRS in their eyes is a quick win –

statistically lowers risk of personal injury,

and reduces property damage.

Some companies are requiring PRS in

order to get business operational liability

coverage. Also will lower premium fees.

Why most people contact us about a

PRS. A $50K system can be protected for

<5% of the UAS cost!

Alternative is failure that can lead to

total UAS loss.

PRS makes sense when the value of the

UAS is 10x or more cost of the PRS.

There are many styles of parachutes.

We’ll discuss the various types, the

advantages and disadvantages of most

popular chutes… These include:

› Flat Sheet Parachute

› Multi-Panel Parachute

› Elliptical, or Conical Parachute

› Annular, Pull down Apex, Toroidal

And why it matters!

Before we start there are challenges in comparing designs:› Inconsistency in how chute size is sold to the user.

Some as canopy area Some as circumference around top of canopy FC measured based on projected frontal area, i.e the opening

diameter Complex canopy shapes make comparison hard.

› Ultimately you want to know a chute’s design coefficient of drag, or Cd, for a given reference area.

› Knowing the Cd is essential to calculate the descent rate under any given weight, size, and base altitude.

› We feel it’s simplest to measure the chute based on the opening diameter of the skirt. The “reference area” is simply the area of the opening. This along with the Cd and you can predict chute performance at a given size, and load weight!

Goal in design is to maximize drag at least possible weight. This means a higher Cd is essential!

Advantages:

› Simple Design

› Low Cost

Disadvantages:

› Low Cd of approximately 0.7 to 0.8

› Bulky for a given load

› Poor Stability, can oscillate above the load

› Lower strength – this is partly due to materials selection

Advantages:› Good stability, stays above the load

› Very strong, usually has over-the-top riser connections

› Fewer risers to tangle – easier to untangle if they do

› Probably most popular HP Rocketry style currently

Disadvantages:› Moderate, Cd of approximately 1, little published info on this. Type not used

outside Rocketry and racing that we can find.

› Use heavier webbing for shroud lines (fewer connections to carry the load)

› More complex design, two to three pattern shapes needed. Uses a lot of tape reinforcement on edges and on all seams leading to higher weight.

› Can rotate under load due to variations in symmetry.

› Can sometimes breathe under slower descent (jelly fish)

› Limited use in UAS as far as we can tell

Advantages:› Good stability at lower speeds, stays above the load

› Good strength-to-weight ratio

› Better efficiency, Cd of about 1.5 – 1.6

› Packs into smaller space per load rating

› Simple repetitive design – only one pattern shape needed

Disadvantages:› At high speed it can wobble

› Multiple gores means more sewing and higher cost

Advantages:› Good stability at typical main chute descent speeds.

› Good strength to weigh ratio

› Very high efficiency, Cd of about 2.2 – 2.4. Noted as the highest known Cd for unguided chute for a given canopy area

› Packs into smallest space per given load rating

› Simple repetitive design – only one pattern shape needed

› Fast opening good for low altitude UAS

› Popular as reserve chutes for parachute jumpers, hang gliders, and ultra-lights

Disadvantages:› Not as good at high(er) speed

› Very fast opening can also cause high opening shock load

› More complex to make, apex pull down adds to complexity and cost

Ideal parachute has the highest load capability at least weight. This means a chute with a high Cd is better.

Different parachute designs can be boiled down to a single number called “Performance Rating” (PR) and then compared objectively.

PR is simple ratio between the parachutes load capability at a given descent speed divided by the parachute’s static weight.

Higher is better!

Chute Type Chute size determined by:

Cd Reference Area

Stability Cd Performance

Rating @ 15 fps **

Use

Flat Sheet Distance across fabric

Area of fabric Ok at low speed,

poor at high speed

Low – 0.7 Approx. 8:1 Main or drogue

Panel Style Distance across

top panels,

usually on diagonal

Area of fabric Good vertical

stability, can rotate or spin

Med – 1.1 Approx. 10:1 Mostly as a Main in Rocketry

Elliptical ,

spherical, conical

Opening

diameter, or

canopy circumference

Area of opening

Medium high

speed, Good low speed

Med – 1.6 13.4:1 Main or Drogue chute

Annular (Iris Ultra)

Opening diameter

Area of opening

Good medium to lower speed

Highest at 2.2

30:1 High

performance

main chute.

Ideal for UAS recovery

We will discuss several methods of chute

deployment:

› Fixed Wing UAS deployment using a

Deployment Bag and pilot chute

› Compression spring based Parachute

Launchers

› CO2 Ejection Systems

› Passive, requires forward flight and air movement for extraction

› Used for Fixed Wing UAS

› Small pilot chute used for extraction

› Simple and low cost

› Not suitable for Multicopters!

Examples are Skycat Launcher, and MARS systems

Active deployment does not require forward flight – use with multicopters

Relatively low cost

Limited in chute size by spring strength to around 60”D chutes.

Because of this max load around 10Kg system as a safety-only device. Descent rate too high to eliminate damage.

Can use with larger chutes by spring ejecting smaller chute which acts a pilot for larger chute. But this delays deployment.

Examples Peregrine Sentinel, Peregrine IDS, DJI Dropsafe

Active ejection using CO2 gas, more energetic deployment, shorter deployment time.

Peregrine systems rated up to 100Kg loads. Features high packing density, resulting in small size.

Manufacturers are not necessarily thinking of facilities to add parachute recovery to products.

Parachute deployment channel needs to be standard on all autopilots (some have this.) Both manual, and programmatic based.

Backup failsafe devices separate from autopilot need to be developed to do automatic algorithmic deployment when risky situations are encountered, like fast descent speed, unsafe attitude (sideways or upside down,) out of bounds, etc…

ESC need failsafe override to cut power in case failsafe activates. You can not deploy a parachute system if rotors are active!

Airframes designed to accommodate PRS. Currently these are an afterthought and it’s up to the buyer to figure it out.

Download this presentation here:

http://fruitychutes.com/other_fun_stuff/genes_blog

/usb-expo-drone-parachute-tutorial.htm

Parachute Recovery Tutorial:

http://fruitychutes.com/uav_rpv_drone_recovery_p

arachutes/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!