6. Description of the CarterCopter's Ballistic Chute


Date: Dec 14, 1998 10:18 AM
Author: Doug Marker (dmarker@zeta.org.au)
Subject: Description of the CarterCopter BRS

CC Ballistic Recovery System

Index

This section (provided by Jay Carter Jnr) describes the BRS being used by the CarterCopter during its development phase.

Description of the CC BRS and its deployment. The ballistic chute was provided by Butler Parachute in Roanoke, Va. The 54ft diameter chute is located in the baggage compartment and is pulled out across the top of the right wing with a 100 pound thrust rocket. When fired vertically in a test, the rocket was able to lift the chute 50 ft vertically. The rocket first pulls a small chute which is attached to the bag containing the main chute. A 5/16 inch dia steel aircraft cable attaches to the parachute bridle and runs from the baggage compartment across the trailing edge of the right inboard wing, across the top of the boom, then forward under the wing next to the boom and across the leading edge of the wing toward the fuselage and then toward the nose of the aircraft and anchored at the tip of a 4 inch dia by 4 ft long tube which extends out in front of the aircraft. The tube is heat treated and anchored to the front of the fuselage such that it can carry a 4000 pound load 90 degrees to the tube.

Once the bag containing the chute has been pulled out approximately 4 ft past the tail boom, the 5/16 dia cable attached to the nose boom gets tight and starts to pull the lines from the bag. The rocket continues to pull the bag and chute away from the aircraft until the chute is completely out of the bag.
Once the chute is out of the bag and the 5/16 cable is stretched tight, the thrust and inertia of the rocket breaks the 500 pound strength cord attaching the chute to the bag. The rocket and bag falls away. The 5/16 cable runs outside the tail boom and under the wing to keep the chute and lines from getting into the prop. As the chute starts pulling on the cable, the aircraft starts to turn to the right as a result of the cable force against the right boom 4 ft from the aircraft center of gravity.

Process once chute is out and deployed. Once the aircraft has turned far enought, the cable will pull away from the aircraft and go straight to the nose boom increasing the leverage arm trying to turn the aircraft around. At this point the aircraft is essentially rotating about the rotor spindle axis and not trying to change the plane of rotation of the rotor. As the fuselage continues to turn due to the drag on the chute, the fuselage and tail booms are no longer lined up with the airstream and are now creating tremendous drag which helps slow the aircraft down and helps create a gradual load increase on the chute. The chute will not see more load than the full weight of the aircraft until the aircraft has completely spun around and the aircraft center of gravity is lined up with the cable.

The aircraft will come down tail first. The chute is not designed to be deployed at our test weight at a sea level speed greater than 200 mph, but since the aircraft is forced to rotate sideways before the full force is seen by the chute, we expect the speed might drop 40 mph during this manuver. If the tail booms did not break off when the aircraft was sideways to the air stream, then the tail booms will help absorb the impact.

In any case the engine and prop wiil aborb some of the impact and will be below the pilot so he does not get squeezed. The pilot will be on his back in a position capable of absorbing tremendous g's. The seat can handle a 30 g loading in this configuration. When the rotor hits the ground, the rotor head attachment is designed to break away sideways. The rotor head attachment is very strong in the up and down direction (proof loaded at 12,000 lbs) but designed to break in the plane of the rotor at about 4000 lbs in the event the rotor should ever hit anything.

Description provided by Jay Carter Jnr.

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- 04 Dec 1998
Created: 01 Dec 1998 - Updated: 13 Dec 1998