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Platform · High Altitude Low Opening

H.A.L.O. platforms

High Altitude Low Opening means falling fast for a long time and opening late — which requires a two- or three-stage deployment sequence.

Line drawing of a payload descending under a parachute from high altitude above the curve of the earth

Stage one: stabilise

The two- or three-stage deployment sequence ensures precise control during high-speed, high-risk descents. The initial parachute, often a drogue, stabilises the platform’s direction and reduces excess speed. It operates at high flight speeds and brings the platform to the minimum safe main canopy opening altitude — precisely the defining characteristic of a low-opening profile. What follows is either another stabilisation stage or direct main canopy deployment.

Stage two: controlled descent

The high-speed descent produces rapid altitude loss with minimal drift — the decisive tactical advantage where pinpoint landing accuracy matters. Directional stability and descent-speed control ensure consistent main canopy openings even at the lowest operational heights.

Main canopy deployment

The main parachute is extracted at low altitude by either the drogue or a secondary stabilisation chute. Depending on opening speed and maximum allowable G-loads, reefing lines or slider mechanisms are integrated to manage deployment shock and protect payload integrity.

What controls the transition

Stages are triggered by sensors: onboard barometric altitude sensors, or descent rate sensors detecting reduced vertical speed as atmospheric pressure increases. Speed measurement combines static and dynamic pressure via Pitot tubes, applying Bernoulli’s principle. The mechanical changeover runs through precision release mechanisms or pyrotechnic and pressure cutters such as Cypres® line cutters, ensuring reliable operation under extreme conditions.

Applications

H.A.L.O. systems are widely used in special forces operations, high-altitude UAV recovery and covert resupply missions. There, low-bulk, lightweight, high-performance parachute solutions reduce detection risk and improve mission success rates.

Products
Deceleration parachutesRam-air parachutesUltralight low volume solutions
Environments
Low air density

Technical data per manufacturer documentation from APCO Aviation Ltd , as of 2026-07-30.

Frequently asked

Asked in technical terms.

Why do H.A.L.O. systems need multiple deployment stages?

Because the main canopy should open only at minimum altitude. The first parachute, usually a drogue, stabilises the platform and removes excess speed until the minimum safe opening altitude is reached. After that follows either another stabilisation stage or direct main canopy deployment.

What controls the transition between stages?

Sensors: barometric altitude sensors, or descent rate sensors detecting reduced vertical speed as atmospheric pressure increases. Speed measurement combines static and dynamic pressure through Pitot tubes. The mechanical changeover runs through precision release mechanisms or pyrotechnic and pressure-actuated line cutters such as Cypres® line cutters.

Where are H.A.L.O. systems used?

They are widely used in special forces operations, high-altitude UAV recovery and covert resupply missions, where low-bulk, lightweight, high-performance parachute solutions reduce detection risk and improve mission success rates. The main parachute is extracted only at low altitude by the drogue or a secondary stabilisation chute, while reefing lines or sliders protect payload integrity.

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