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James Yuen

real world Clearing up some acronyms (GMP related)

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James Yuen

With a few events coming up, lets make a few acronyms clear as some are being mis-interpreted. We don't plan on using (most of) these on VATSIM anytime soon, however please be careful when teaching this to other people especially and refer correctly to the terms.:

SOBT - Scheduled Off Block Time

  • What: The time the airline timetables for a flight to depart
  • Why: To tell passengers when to arrive at the airport
  • Accuracy: None (especially if you fly with Ryanair!)

EOBT - Estimated Off Block Time

  • What: The time the flight communicates with Eurocontrol's Network Manager Operations Centre (NMOC), that indicates an estimate to when they will push back
  • Why: For general ATC planning purposes, such as determining a CTOT
  • Accuracy: +/- 15mins of calling ready for pushback

CTOT - Calculated Take Off Time a.k.a. 'slot'

  • What: A (optional) time that is issued by NMOC, that indicates when an aircraft can take off. The slot time is often no earlier than EOBT + Minimum Taxi Time (MTT)
  • Why: For longer term ATC planning, either to regulate the amount of aircraft entering an airspace sector or to control the amount of aircraft landing at an airport with a landing restriction (i.e. limit on arrivals per hour)
  • Accuracy: -5/+10mins

*The below is for airports with A-CDM (Airport Collaborative Decision Making), which is (essentially) the above on steroids*

TOBT - Target Off Block Time

  • What: Often the exact same as the EOBT, this the time that the flight will communicate to the airport itself. It is also used to determine a TSAT.
  • Why: To get a more accurate scope of aircraft movement on the GND
  • Accuracy: +/- 5 mins of calling ready for pushback and +/- 11mins of EOBT

TSAT - Target Start Approval Time

  • What: The time that, given a TOBT and CTOT (if exists), the airport determines an aircraft can pushback. When there's no delay, TSAT=TOBT which then determines the TTOT.
  • Why: To prevent aircraft from pushing back early, and keeps aircraft on stand in a 'virtual queue' rather than sitting at the holding point with engines on.
  • Accuracy: N/A

TTOT - Target Take Off Time

  • What: The time that is calculated either by determining the next available departure time. Examples:
    • During the 10-11am in the morning, there are many flights from LHR to the USA, but not from other airports. Therefore, there is no CTOT but a delay at the holding point for route separation. The TTOT will determine when the next possible time a departure to the USA can take off based on the queue.
    • If there's no delay, as mentioned above, the TTOT will be TOBT + MTT.
    • If there's a CTOT, the TTOT defaults (initially) to CTOT - 5mins (given the CTOT accuracy) to determine the TSAT
  • Why: For the airport to monitor the airports performance; to inform pilots of when they expect to take off
  • Accuracy: N/A; ideally as accurate as possible.

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Michael Benson
On 08/08/2019 at 09:58, James Yuen said:

TOBT - Target Off Block Time

  • What: Often the exact same as the EOBT, this the time that the flight will communicate to the airport itself. It is also used to determine a TSATIt is used to generate a TTOT, which then determines the TSAT.
  • Why: To get a more accurate scope of aircraft movement on the GND + providing NMOC with a much more accurate picture of the situation thus helping with management of the network.
  • Accuracy: +/- 5 mins of calling ready for pushback and +/- 11mins of EOBT Each airport will have it's own rules.

TSAT - Target Start Approval Time

  • What: The time that, given a TOBT and CTOT (if exists), the airport determines an aircraft can pushback. When there's no delay, TSAT=TOBT which then determines the TTOT. After a TTOT is generated the TSAT is determined (in a simplistic way) of TTOT - Average time taken to get from that stand to the hold.
  • Why: To prevent aircraft from pushing back early, and keeps aircraft on stand in a 'virtual queue' rather than sitting at the holding point with engines on.
  • Accuracy: N/A Each airport will have it's own rules, ours is -5/+infinity.

TTOT - Target Take Off Time

  • What: The time that is calculated either by determining the next available departure time. Examples: It's not quite as simple as that - using the TOBT data and taxi times the system develops what it considers to be the optimum departure order based on wake turbulence, SIDs and any route restrictions.  Therefore an A320 on a MID may get a later start time than a B747 on a MID as the system is attempting to group a bunch of heavies.
    • During the 10-11am in the morning, there are many flights from LHR to the USA, but not from other airports.Therefore, there is no CTOT but a delay at the holding point for route separation. The TTOT will determine when the next possible time a departure to the USA can take off based on the queueI think it is important to be clear here that it is SID based, not where in the world it is going.  A CPT may get a 10 minute start up delay, and UMLAT also going to the USA may get nothing.
    • If there's no delay, as mentioned above, the TTOT will be TOBT + MTT.
    • If there's a CTOT, the TTOT defaults (initially) to CTOT - 5mins (given the CTOT accuracy) to determine the TSAT
  • Why: For the airport to monitor the airports performance; to inform pilots of when they expect to take off We don't use it operationally and therefore no pilot should be basing the time  they'll get airborne off it.  The main purpose is to generate the TSAT and to give NMOC a more accurate indication of departure times compared to EOBT mode.
  • Accuracy: N/A; ideally as accurate as possible. We don't use it at all from an operational point of view

 

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Connor Faulder

😕🤨

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Harry Sugden

Enough to send any S1’s (or even anyone’s) head spinning during CTP... doh! Another acronym!

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