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CTSW ACL 4 Beacon Replacment

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I recently purchased an ACL 3 beacon for my CTSW, My Factory ACL I is cracked/yellowed and a few LED's are burnt out.

The attached install instructions talk about a FLARM interface. And some quick research shows that this is primary a European thing that has to do with traffic avoidance.

I am not familiar with this, Has anyone heard of this? Does the Dynon interface with this FLARM output?

ACL 4 Install.pdf




Excerpt on the interwebs:

"How does FLARM work? FLARM works by calculating and broadcasting its own future flight path to nearby aircraft. At the same time, it receives the future flight path from surrounding traffic. A smart motion prediction algorithm calculates a collision risk for each aircraft based on an integrated risk model. When a collision is imminent, the pilots are alerted with the relative position of the intruder, enabling both to avoid a collision"



If you order an ACL 3 from Aircraft Spruce they will ship you and ACL 4, and is actually drop shipped from JHM Innovations In Texas. 

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Flarm is a collision avoidance system widely used by sailplanes, especially in Europe, and often required in soaring competitions, including in the US.

Flarm has been around for about 15 years. Like ADS-B, it's based on aircraft periodically broadcasting their GPS coordinates, and listening for the coordinates of others. Where it differs from ADS-B is in the computations it makes to determine the threat level. It looks not just at the speed, position, altitude and direction of travel of the other aircraft, but also at the rate of change in direction and altitude. It computes where each aircraft will be in the future, assuming they continue around a turn if they are in a turn; and based on that decides the level of warning needed.

For sailplanes, which often fly very close to one another, even within a wingspan, especially while thermalling, this computation is particularly important. A sailplane at exactly your altitude, directly across the thermal from you, in about the same 45 degree left-banked turn as you, with about the same airspeed and climbing at about the same rate, is not really a threat, even if he's only a couple hundred yards away. He will sweep through the airspace you currently occupy within 10 or 15 seconds, but by then you'll be in the airspace he currently occupies. At contests, where there might be 20 or more sailplanes in the same thermal, you don't want the system to issuing warnings unless there is an immediate threat.

The system available in the US is called Power Flarm. It is compatible with ADS-B in that it also receives 1090Hz ADS-B broadcasts (not 978 UAT) and includes these among its potential targets. However, it does not provide ADS-B out and therefore cannot be used in rule airspace. It broadcasts on a different frequency.

In the US, where Flarm has only been adopted by gliders (as far as I know), there is absolutely no need to equip a powered aircraft with Flarm unless you often operate near an active gliderport with a substantial number of Flarm-equipped sailplanes. 

The Flarm feature on your light is interesting. I assume that if it receives notification of a potential threat from an on-board Flarm unit it will start blinking extra bright or extra fast until the threat clears. I've never heard of this before. I wonder why the light wouldn't just blink faster or brighter all the time unless there's a power (certainly on sailplanes) or heating issue.

Mike Koerner

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