Aircraft Midair Collision Alert

Many gliders have an Airborne Collision Avoidance System (ACAS) called a FLARM (FLight AlaRM). This consists of the FLARM device itself (computer, GPS, Tx Rx antennas) and a display. Such systems run for $2500-$3000, but are well worth it as gliders are often flying near each other as well as other aircraft. These units are constantly sending out ping signals with aircraft location, direction, and speed. They also receive the same signals from other FLARMs and process this vector data in order to determine if there is the potential for a collision.

The display will show information on where the other aircraft is, so on an alarm, the pilot can look at it and determine where the other aircraft is and make visual contact and take any evasive action, if necessary.

On Aerotow, the glider is only 200' behind the towplane. As well, gliders near the airfield are often going towards the same clouds or sources of lift to climb in and get away on task. Such busy skies have been a big source of aviation accidents, and so many glider pilots are more than willing to shell out money to equip their aircraft with such systems.

Here is a case where another glider was approaching some gliders circling under a cloud. While they were turning one direction, I was turning the other. I saw them coming and could tell they were banking to get away and line up better to join the thermal, but for a few seconds, we were pretty much pointing at each other. I never saw the warning, though I heard the alarm sound and knew from what I saw, that's what it was warning about. I also had to be concerned for the other gliders I could see in the thermal I was sharing. As it was, I also needed to re-orient myself to adjust for another glider in a thermal, but held off a bit until I saw I was clear.

What do you think? Are these worth the expense? Should something like this be mandatory for all aircraft and not just gliders? Leave a comment and share your experience.