Altitude Deviation Detection
This feature monitors and alerts for situations where aircraft climb or descend away from defined boundaries related to the planned flight level. This feature monitors and provides alerts for deviations outside of +/- 3000ft from the first planned flight level. The system can also provide Notifications when aircraft have recovered from the altitude deviation and returned to within the +/- 3000ft boundary.
How Altitude Deviation Detection Works
During this explanation, refer to the diagram below and the description in the ‘Text Boxes’.
Text Box 1:
Initially, during the climb the detection is inactive.
Text Box 2:
The lower boundary (-3000ft from the filed flight level) is crossed during the climb and Altitude Deviation detection becomes active. Every received tracking point that contains Barometric Altitude is checked for deviation from the upper and lower boundaries, until monitoring stops at Text Box 5.
Text Box 3:
Tracking Flight crosses lower boundary and an Altitude Deviation Notification is sent. The same would occur if the flight crossed the upper boundary.
Text Box 4:
Flight returns to within the lower boundary and an Altitude Recovered Notification is sent. The same would occur if the flight returns into the upper boundary.
Text Box 5:
When the flight has a tracking within the DEST circle then Altitude Deviation detection stops.
The radius from the Destination is based upon the (Cruise Altitude in ft / 1000)*4, e.g. FL200 (20000ft) has a radius of 80NM.

Setting set up Altitude Deviation Notifications
Setting up Altitude Deviation Notifications is completed in a similar way to setting up a normal notification
Post Flight Altitude Deviation
Even if notifications are not set-up the user can still find any Altitude Deviations within Postflight under the Events log.
Special conditions and Limitations of the Altitude Deviation Notification
The following lists some special conditions and limitations to be aware of regarding the Altitude Deviation Notification:
- When a flight has more than one planned flight level the user can expect to experience false alarms if Altitude Deviation Notifications are used.

- If the flight never climbs high enough to reach the lower boundary then Altitude Deviation detection is not started.
- If a flight descends earlier than planned and is still outside the DEST circle, it is possible that it falls below the lower boundary and an Altitude Deviation Notification is generated.
- If a flight diverts to an Alternate airport after entering the DEST circle, then there will be no detection because the monitoring is stopped when the aircraft enters the DEST circle.
- The upper and lower boundaries for monitoring are fixed at 3000ft above and below the first flight level in the flight plan.