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Auto ACASAutomatic Air Collision Avoidance System

The brief brief brief one.

Bengt-Göran SundqvistSaab Aerosystems

2005-02-02

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Auto GCAS•Automatic Ground Collision Avoidance System •Cooperaton Between Sweden and USA 1997 – 1999•Flight tested in F16.•Currently under implementation and flight test in Gripen.

Historic perspective – Losses of 37 Viggen

Auto ACAS

• Automatic Air Collision Avoidance System

• Technology demonstration program between Sweden (FMV) and USA (USAF), 2000 – 2004

• Funded (50-50) by USAF Air Force Research Laboratory and FMV (totally 12 MUSD)

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LOCKHEED MARTIN

LOCKHEED MARTIN

Auto ACAS - Cooperation

Koncept Developm. Implementation Flight test

2000 2001 2002 2003

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Auto ACAS Auto ACAS Objective/Customer ”requirements”

• Flight Test Demonstrate a system providing:• Protection through an automatic escape maneuver• No-nuisance operation, i.e. not interfere with normal

operation (incl. Air Combat, Formation flight etc)• Fail-Safe operation

• System designed as emergency last resort and aimed for both manned and unmanned A/C (UAV)

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The concept Auto ACAS

Intuitive to first identify a collision …..

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Datalink Datalink

… and compute coordinated escape maneuvers.

Auto ACAS does not predict future collision.

It continuously optimizes coordinated escape maneuvers. The maneuver is executed when these claimed spaces intersect (in time and space).

The concept Auto ACAS

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The uncertainties are represented by cones

Cone radius

• ½ Wingspan

• Position uncertainty

• Pred. error of trajectory

Escape maneuver: roll 120 deg/s, followed by 5g

Cones intersect

Activate the escape maneuver!

Roll to the selected escape angle and apply nz

Control is returned to the pilot

The concept Auto ACAS

The aircraft fly within the claimed space

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Summary Auto ACAS concept

• Does not predict collision.

• Continuously claims space, for the own escape maneuver, which is optimized against claimed spaces of other AC.

• The size of the space depends on the physical size of the AC and a number of uncertainties. The size varies continuously as a function of these.

• Automatically activates a safe escape maneuver when the optimized spaces intersect (in time and space).

• The AC flies in the claimed space during the activation.

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Pros using the Auto ACAS concept

• Safe as all uncertainties are accounted for in the size of the claimed space. All AC ensure that the own fly-out will stay within the own transmitted claimed space.

• Nuisance free as the maneuver is deterministic for all AC it can be estimated with high fidelity and the uncertainties are thus kept small.

• Handles dynamic situations (continuously optimized escape maneuvers for all AC).

• Requires no handshaking (same optimization) • Easily adoptable to new platforms• Fail-safe• Robust against link drop-outs

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Cons using the Auto ACAS concept

• ACAS will require transmission of data over the link, this can limit the transmission of tactical data.

• Full operation is not safe in an out-of-network environment.

• Complex - to fulfill requirements, given the limitations and uncertainties, requires heavy algoithms.

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Formation flight logic

When in Close formation: all activations are inhibited.all other aircraft yield to formation flying aircraft.

When in Inhibit: the activation is inhibited against the specific aircraft. full ACAS functionality against other aircraft.

The logic is by-passed during activation.