Ultralight Parachute Systems Evaluated

⚫ pilot parachute with spring initiation,

⚫ ballistic with 8oz steel slug tractor,

⚫ballistic mortar with the densely packed parachute as the projectile,

⚫ rocket tractor.

Joe Chitty and Charles Ligeti are working on a variation that uses a cartridge (dual) to fire a small cylinder attached to the parachute bag. It also has a back-up pilot chute.

The deployment times are from the time of pulling the release handle or throwing the parachute. In the case of the hand-deployed type, much time could be lost in grasping the bag and clearing it from its velcro retainer, particularly if there are strong centrifugal or pitching forces on the pilot; the chance of fouling the structure also tends to be higher. Some of these factors would also have some relevance during the release process for the other types.

The critical feature of deployment times is that a seconds delay can mean feet of altitude lost. If you have had an engine failure over hostile territory, then you probably have ample time to deploy the parachute after preparing yourself and the plane. If you are in a vertical dive, just passing your aircraft’s VNE, after falling off the top of a loop, you could be losing at least 100 feet per second. Ballistic parachutes have been successfully deployed at 75 feet following an engine failure and at 200 feet following a wing failure and spiral dive from 1,100 feet.

To ensure reliability, the ballistically operated types include 2 cartridges. On some types, one is fired electrically and the other mechanically, while other types fire each one mechanically. Of course, only one cartridge is required to deploy the parachute. There is no redundancy in the rocket system. However, there is a built-in electronic system for checking the circuits, the battery and the rocket charge.

Because of the weight of the projectiles and their high velocity, the ballistic and rocket types are quite lethal. The motor type may not be quite as lethal due to the larger surface area. Care must be taken to safety/disable the equipment while on the ground. Of course, pre-take-off checks should include the check that safeties have been removed.

There are a number of factors to consider with regard to the mounting position. The manufacturer/supplier is in the best position to provide specific advice. The ballistic types need to be mounted securely on a part of the aircraft which is strong enough to absorb the recoil from the charge. Furthermore, it should not be attached to a part of the airframe which could fail in flight- there would not be any resistance to the thrust of the cartridge, so the slug would not be projected. The pilot chute deployed type needs to be mounted where there is a clear air flow available to enable the pilot chute to operate. There has been at least one case of either incorrect mounting or packing which allowed the accidental deployment of a pilot chute type. The aircraft struck power lines before falling into a lake – both potentially dangerous situations.

The attachment point for the parachute bridle should be given careful consideration. It should be reasonably close to the centre of gravity so that the touch-down attitude is not too far off level. It should also be the strongest point on the aircraft. If this is in doubt, wear a portable pilot’s harness and attach this to the parachute bridle.

It is important that a stainless steel cable is used between the aircraft and the parachute bridle. This cable should be long enough to extend past the propellor as its purpose is to prevent the propellor from cutting the nylon bridle, thus detaching the parachute. A case like this happened in Europe in May. We believe that all Australian suppliers include the stainless steel cable with their equipment.

The question may well be asked: why a recovery parachute; why not a personal parachute? The main reason relates to height. Ultralights are rarely high enough to provide enough time to climb out of the aircraft (spinning and pitching) and deploy a parachute after gaining enough separation. Also, most ultralight pilots are not trained in parachuting and so may have difficulty in releasing the parachute and also risk injury on landing.

It should be appreciated what effect would occur on deployment. The opening shock would be quite severe, particularly if the largest possible parachute was fitted. The plane is likely to pitch up 90° initially. There is also likely to be some degree of pendulum action. Touching the ground while swinging sideways could be somewhat unsatisfactory. Wind will also influence the way that the plane makes contact with the ground.

The quoted rates of descent are exclusive of any drag gain from the aircraft structure or any drag loss from “primary body wake effect” of the aircraft. Since these factors depend on the shape of the aircraft as it sinks below the parachute, they cannot be predicted. For example, if the structure is still intact, the wings will provide quite a large parachute effect; they may also provide shielding and generate unfavourable turbulence to the parachute. However, taking the raw rates of descent, for rates between 22. 5 and 25 feet per second the aircraft structure must absorb moderate impact loads; for rates between 25 and 27. 5 feet per second, the aircraft structure must be sufficiently robust to absorb high-impact loads.

The parachutes need to be unpacked and inspected periodically – usually every 12 months. Most types can be re-packed by your local parachute rigger for quite a modest charge. However, the motor type needs special equipment and the repacking can cost several hundred dollars.