HFI alerts pilots to threats

A new acoustic-based detection system could help helicopter pilots evade small arms fire when flying low into war zones.

The hostile fire indicator (HFI) technology, being developed by BAE Systems, will help pilots ascertain which direction shots are coming from so that they can take evasive action.

‘Most aircraft already have missile warning capability but are still vulnerable to small arms fire,’ said Bill Ashe, programme manager at BAE Systems’ Survivability and Protection Systems. ‘Often the helicopter crews don’t know they’re being fired upon until it’s too late and sometimes it is way too late.’

Small arms fire, which includes rounds from machine guns and rocket-propelled grenades, has been responsible for dozens of helicopter losses and deaths in Iraq and Afghanistan.

The BAE Systems technology uses acoustic data from microphones, noise reduction and location algorithms and information from existing aircraft survivability equipment sensors to give helicopter crews multiple indications of such hostile fire. The information is relayed to the pilot through an onboard display in the helicopter.

BAE Systems recently conducted live-fire tests at a facility in the US and found that the HFI system could measure acoustic data and accurately detect threats in each test scenario.

‘The system is specific enough for the pilots to take evasive manoeuvres,’ said Ashe. ‘Currently they don’t know which direction they’re being shot at and our system is accurate enough to help them with that.’

The most challenging part for BAE System’s HFI developers was designing acoustic sensors that could pick out the sound of gunfire amid all other noise — including the whirring sounds from the helicopter itself, which Ashe likened to listening to a whisper during a rock concert.

Ashe said the developers are still investigating how to distinguish between the sound of incoming and outgoing fire. In the technology’s current stage, crew members firing out of the helicopter could potentially register a string of false reports on the HFI system.

Ashe stressed that the acoustic-based HFI technology is not designed to be a stand-alone system. It could be used with, for example, optical sensors.

There are plans to test additional sensing technologies and techniques on military aircraft to make the system more robust and improve its detection capabilities.

The HFI system is constructed in such a way that it could be connected to existing onboard indicator systems.

‘It could be installed in hours with very little impact to the warfighter,’ said Ashe.

Siobhan Wagner