S1, C7 - Altimeter Setting And Vertical Reference

Question 1

The regional pressure setting (RPS) is…

Answer 1

…a forecast of the lowest QNH value within an ASR.

ATSUs are to have available the RPS for the ASR in which they are situated and appropriate adjacent regions.

These values are to be passed to pilots when requested or at the discretion of the controller.

However, a pressure setting is not to be volunteered if a controller is unsure that it is appropriate to the flight.

Airspace below TMAs and CTAs does not form part of the ASR RPS system. Instead, the QNH of an adjacent aerodrome should be used for aircraft at or below the transition altitude.

Question 2

The transition altitude is…

Answer 2

…the altitude at or below which the vertical position of an aircraft is controlled by reference to altitude (or height where QFE is used).

Wherever possible, there is a common TA for aerodrome within a CTR. Unless otherwise notified, the TA for civil aerodrome is 3000ft

(6000ft at EGAA)

Question 3

The transition level is…

Answer 3

…the lowest FL available for use above the TA. It is determination he’d from the table in MATS1, App A, as follows:

1) within CAS by the controlling authority and it will normally be based on the QNH of the major aerodrome
2) OCAS by the aerodrome operator and based on the aerodrome QNH.

Question 4

Transition layer is…

Answer 4

…the airspace between the TA and TL.

Question 5

When transmitting altimeter pressure settings that are lower then 1000hpa…

Answer 5

…controllers are to specify clearly the unit of measurement and pay particular attention to the read back

Question 6

1013.2 - Level expressed as FL:

Answer 6

1) at or above the TL
2) climbing through the transition layer
3) above 3000ft amsl and not in the vicinity of an aerodrome

Question 7

QNH - Level expressed as altitude:

Answer 7

1) at or below the TA i.e. In the vicinity of an aerodrome or beneath specified TMAs and CTAs
2) descending through transition layer
3) during final approach

Question 8

QFE - Level expressed as height:

Answer 8

During final approach, as local procedures require or when requested by the pilot

Question 9

RPS - level expressed as altitude:

Answer 9

At or below 3000ft amsl when OCAS and not in the vicinity of an aerodrome

Question 10

Aerodrome elevation is…

Answer 10

…the elevation of the highest point on the landing area.

It is the elevation upon which the height for visual manoeuvring (circling) is based.

In addition a threshold elevation is published for each runway

Question 11

The pressure settings associated with aerodrome and threshold elevation are expressed as…

Answer 11

…QFE aerodrome and QFE threshold respectively.

Question 12

QFE threshold for an instrument runway is used when…

Answer 12

…the threshold elevation is 7ft or more below aerodrome elevation.

Question 13

Aircraft are to be given the aerodrome QNH…

Answer 13

…prior to taking off and when at/below the TL for arrivals.

…prior to commencing an approach

The TA and TL will only be passed if requested by the pilot.

Question 14

When an aircraft is cleared to descend from a FL to an altitude…

Answer 14

…the appropriate QNH shall be included in the same transmission.

If FL vacating reports are required the request should be included with the descent clearance.

TL is only passed to aircraft if requested.

Question 15

If an aircraft makes an instrument approach that is to be followed by a visual manoeuvre (circling) to land on another runway…

Answer 15

…as appropriate, the QFE aerodrome or QFE threshold is to be given.

Question 16

The lowest cruising level available for assignment on ATS routes shall be determined by…

Answer 16

…the ACC using the appropriate RPS. On an airway, this must always be at least 500ft above the notified base.

Question 17

Except when aircraft are leaving CAS by descent, controllers should not normally allocate…

Answer 17

…a level to an aircraft which provides less than 500ft vertical separation above the base of a CTA or airway.

This will provide some vertical separation from aircraft operating beneath the base of CAS.

Similarly, controllers should exercise caution when operating close to the upper vertical limit of a CTR or CTA where it is not contiguous with further CAS.