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The ACAS is a free service that proactively notifies a pilot when a new adverse condition arises after a flight plan is briefed or simply filed. Alerts are specific to particular flight plans. The ACAS was created because pilots may be unaware of new adverse conditions that arise between telephone interactions or radio contacts with Flight Services, in some cases resulting in a safety issue for the pilot.

Alerts are sent to the pilot using text messages (also known as Short Message Service or SMS messages), email messages, or short messages similar to SMS messages that are transmitted via the Iridium satellite constellation directly to special devices in the cockpit.

The alert messages are short. They only identify the type of adverse condition and the flight plan to which it applies. Pilots are asked to contact Flight Services to obtain complete details for the adverse condition. However, pilots also can go to their home page on the LMFS Pilot Web Portal to view and acknowledge ACAS alerts for their flight plans without having to call a specialist. 

An additional ACAS feature is Flight Plan closure reminders.  These are sent via text message or email for flight plans that have not been closed 15 minutes after the estimated time of arrival.

What Adverse Conditions Generate Alerts?

The ACAS generates flight plan-specific alerts for:

  • TFRs
  • NOTAMs for Airports or Runways being Closed or Unsafe (applies to origination, destination and alternate airports)
  • Convective SIGMETs
  • Center Weather Advisories (CWAs)
  • Severe Weather Watches and Warnings
  • Urgent PIREPs or AIREPs

An adverse condition must intersect or be within a standard 25 nm briefing corridor of the flight plan route in order for an alert to be generated.

When Are Alerts Sent?

Alert detection begins as soon as a flight plan is filed. However, alerts are not transmitted to the pilot until 2 hours prior to departure. Alerts that were detected prior to the 2 hour window are only transmitted if they are still valid at 2 hours prior to departure.

This approach is taken to avoid inundating pilots with transient alerts that will clear up prior to the 2 hour window. Consider a pilot that gets a briefing for a flight the evening before a morning departure. During the night, adverse conditions may move through the area and be gone before morning, and there is no value in sending alerts to the pilot for those situations. However, any adverse condition that arises during the night and is still valid 2 hours prior to the departure will result in an alert being sent to the pilot at that point.

Adverse conditions that arise once inside the 2 hour window and up until flight plan closure are sent to the pilot immediately.

How Do I Sign Up?

Pilots register for the ACAS on the Lockheed Martin Pilot Web Portal. Once you’ve created an account on the Pilot Web Portal, go to the Account Preferences page and select the Alerts sub-tab. The figure below illustrates an account with two sets of contact information.

The first row indicates that Preflight alerts and Flight Plan Closure Reminders are to be sent via text message to the phone number in the third column. The second row indicates that In-flight alerts should be sent to a SpiderTracks device, the first Iridium-based device supported by the ACAS.

Additional detail on interaction with the Alerts sub-tab can be found in the Pilot Web Portal help documentation.

Once the contact information is saved in the pilot’s account preference, alerts are automatically transmitted for all flight plans filed under the account (either on the web or via telephone). If for any reason alerting is not desired for a particular flight plan, an override capability is available both on the website or when filing via a specialist over the phone.

Briefing or No Briefing

ACAS handles flight plans for which a standard briefing was performed differently than for flight plans for which an outlook, abbreviated, web or no briefing (through LMFS) was performed.

If the ACAS finds that a standard briefing was performed for a flight plan, only adverse conditions that occur after the briefing time can result in an alert. Once an alert is sent to the pilot, and (if) the pilot contacts Flight Services to obtain the details of the adverse condition, the specialist will know that the pilot received a standard briefing. In that case, if no further information is requested, the specialist will be able to provide just the details of the specific adverse condition.

If the ACAS finds that anything less than a standard briefing was performed, the file time is used as the start point for new alerts. When the pilot contacts Flight Services, the specialist will know a standard briefing was not performed (by LMFS) and will be obligated to provide additional information after addressing the alert. Keep in mind that alerts are not generated for adverse conditions that arose prior to the file time. We understand pilots may obtain a briefing elsewhere, and it would be undesirable to receive an ACAS alert for a potentially large number of adverse conditions. It’s important that users understand that the ACAS is not a substitute for getting a briefing.

For LMFS Pilot Web Portal users, we understand pilots can self-brief on the website consistent with the requirements for a standard briefing. However, there is no reliable method to automatically determine this was the case. For example, we could detect that a pilot clicks on all the sections of a briefing, but we cannot determine if the sections were actually read. Consequently, the system simply lets the specialists know a web briefing was obtained, and the specialist will ask if the pilot has any further questions relative to that briefing.

Messages Sent to the Pilot

Pilots will always receive at least one message from the ACAS at the time a flight plan is filed. This message is simply to confirm to the pilot that the ACAS has begun monitoring the flight and to let the pilot know when alert transmission will start. The format of the message is shown below:


LM Flt Svcs Advisory--N345678--ALERTS STARTED@DDHHMM TX/DDHHMM--NO BRF-- Call Flt Svcs 1-800-992-7433

The first example is for a flight plan for which a standard briefing was found. The second example is for a flight plan for which a standard briefing was not found. The exhortation to contact Flight Services is to request a standard briefing. As noted above, this is not required, but allows for more focused provision of information when calling Flight Services to obtain alert information.

The TX field indicates the time at which alerts will be sent (transmitted) to the pilot. This corresponds to the start of the 2 hour window prior to the filed departure time as discussed above.

The format of an actual adverse condition alert is shown below:

LM Flt Svcs Adv Cond Alert--Conv SIGMET--NRKC409 KBWI 021930 KORD--Call Flt Svcs 1-800-992-7433

LM Flt Svcs Adv Cond Alert--Multiple Conditions--NRKC627 TIW 071930 K0Q9--Call Flt Svcs 1-800-992-7433

The first example is for a single adverse condition, a Convective SIGMET in this case. Following the adverse condition type is the aircraft callsign, the departure location, the departure date and time (DDHHMM), and the destination location. The Flight Services number is provided directly in the message for ease of placing the call.

The second example illustrates what happens when multiple conditions are detected in a short period of time. This can happen commonly when AIRMETs are issued. Rather than sending multiple adverse condition alerts all corresponding to different phenomena in the same AIRMET, the ACAS bundles these together in a single alert that simply indicates multiple adverse conditions have been detected. When the pilot contacts Flight Services, the specialist will still have information on each individual adverse condition.

A variety of other messages can be sent to the pilot for less common situations. These include:

  1. Alerts Stopped notification – occurs when a flight plan is filed with alerts enabled, but alerting is subsequently disabled for the flight plan.
  2. Alerts Cutoff notification – occurs when a flight plan is not closed within a period of time after the filed ETA.
  3. Alerts Modified notification – occurs when a flight plan for which alerts are enabled is amended and no standard briefing can found to match the amendment.
  4. ACAS Outage & Estimated Recovery Time notification – occurs when maintenance or any other type of outage occurs for the ACAS; this message is only sent to pilots that have filed flight plans in the system that are eligible for ACAS alerting. Note that the message may be sent more than once if the estimated recovery time needs to be extended.
  5. ACAS Restoration notification – occurs after an ACAS outage when service is restored.
  6. Test Messages – when contact information is entered in the Alerts sub-tab of the Account Preferences, the user can immediately send a test message any address, phone number or special device simply to verify the contact information was entered properly.

What to Expect When Contacting Flight Services After Receiving an Alert

When a pilot contacts Flight Services after receiving an alert, the specialist will know immediately when the flight plan is retrieved if adverse conditions exist. Even if a pilot calls for some reason other than an adverse condition alert, the specialist will see and communicate the alerts. The specialist will be able to provide the information quickly. With a single click, the specialist has access to both textual and graphical information depicting the location of the adverse condition relative to the route or, for in-flight, the extrapolated (estimated) position of the aircraft. This provides an approximation of the proximity of the aircraft to the adverse condition.

As discussed earlier, if a standard briefing was performed for a flight, the specialist will be able to provide just the information associated with the adverse condition alert. Otherwise the specialist is required to provide additional information.

IFR Limitations

IFR flight plans receive ACAS alerts in the pre-flight time frame up to 30 minutes before departure. At that point, IFR flight plans are deleted from the Flight Services automation system. This occurs because Flight Services is not made aware of amendments made to an IFR flight plan by ATC. Without correct routing information, the ACAS might generate false alerts or miss actual alerts.

Lockheed Martin is evaluating methods for obtaining current flight plan information for IFR flights so that in the future ACAS will be able to generate alerts through the duration of the flight.

Other Important Lower-Level Details and Limitations

  1. Standard texting rates apply for any message delivered via SMS or to a special device.
  2. Cell-based communication is not guaranteed and therefore the delivery of text messages or emails to smart phones or tablets is not guaranteed. Pilots must be aware of whether or not they are in an area with cell communications and rely on traditional communications with Flight Services when appropriate.
  3. Cell-based communications is especially unreliable in-flight, particularly above certain altitudes and/or speeds. If a user configures in-flight alerts to be delivered by a cell-based method, the ACAS will still attempt to deliver the messages; however, the pilot must not rely on this mode of alert delivery to stay informed of all adverse conditions.
  4. In the initial version of the ACAS, an additional buffer period of 90 seconds is subtracted from the briefing or file time and used for filtering alerts. This very conservative approach is taken to make sure no adverse conditions are missed. This means that if a briefing is requested and an adverse condition was received by the system up to 90 seconds before the briefing, it will be included in the briefing and the pilot will also receive an alert for the same adverse condition. The buffer period will be eliminated in a future release at which point we will have an alternative, deterministic method for verifying whether an adverse condition was included in a standard briefing.