Distance to Touchdown
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Safety Reminder Message
Distance to Touchdown
- EUROCONTROL Agency has been informed by some European airlines, through the EUROCONTROL mechanism of voluntary ATM incident reporting, EVAIR, of a number of occurrences concerning provision of distance to touchdown (DTD) information to aircraft being vectored for a pilot-interpreted final approach aid.
- Distance to touchdown information enables pilots to manage their descent profile and energy/fuel efficiency. This is especially important when there is a deviation from the STARs during vectoring and cleared shortcuts.
- Pilots expect accuracy of estimated DTD to increase as distance to go reduces.
- Unexpected reduction in DTD can cause problems with energy management and an overly ‘ambitious’ offer might encourage some crews to ‘can-do’ themselves into an overload situation.
- Significant increase in DTD requires early reduction in Rate of Descent (ROD) to avoid the high fuel burn associated with longer maintenance of the assigned altitude (level flight).
- Crews expect that significant changes to DTD are advised as soon as possible and, if tactical assessments change and speed control cannot resolve matters, the solution should be to increase distance rather than reduce it.
ICAO Provisios in PANS-ATM (DOC 4444)
- 18.104.22.168 b) when an aircraft is given its initial vector diverting it from a previously assigned route, the pilot shall be informed what the vector is to accomplish, and the limit of the vector shall be specified (e.g. to ... position, for ... approach).
- 12.4 ATS SURVEILLANCE SERVICE PHRASEOLOGIES
- 22.214.171.124 VECTORING FOR ILS AND OTHER PILOT-INTERPRETED AIDS
- b) YOU WILL INTERCEPT (radio aid or track) (distance) FROM (significant point or TOUCHDOWN).
- It should be noted that, in case a State decides not to implement the provisions of PANS-ATM, any significant difference between the procedures used in a State and the ICAO provisions should be published in the national AIP.
Your Attention Is Required
- Note the subject and investigate the relevance in your operational environment.
© European Organisation for Safety of Air Navigation (EUROCONTROL) August 2008. This alert is published by EUROCONTROL for information purposes. It may be copied in whole or in part, provided that EUROCONTROL is mentioned as the source and to the extent justified by the non-commercial use (not for sale). The information in this document may not be modified without prior written permission from EUROCONTROL. The use of the document is at the user’s sole risk and responsibility. EUROCONTROL expressly disclaim any and all warranties with respect to any content within the alert, express or implied.