Aerodrome Safeguarding Approach Surfaces

[OCEAN WUN ZERO]

I hope this is the right forum for this.
Can any Airport Ops Lads or Lasses answer this.
If you have a displaced threshold the approach surface starts 60m into the undershoot from the threshold it then is 150m either side of the centerline diverges at 15% and has an initial slope of 1:40.
It appears that a number of airports have holding points that therefore put the average public transport jet in the surface and therefore the runway should not be used for landing whilst this “ obstacle “( CAP 168 Glossary page 3) is there!!!!!??????? Thus severely limiting the holding point options.

Any ideas??
:ugh::ugh::ugh::ugh:

OWZ

[Musket90]

You are correct. Same applies for runway crossing points half-way down the runway where holding points are positioned inside the the runway strip but outside the cleared and graded area i.e for instrument runway between 105m and 150m from runway c/l.

I can only think that because the "obstruction" at the holding point is constantly changing, moving and therefore temporary it is considered acceptable. If it wasn't then runway capacity would be seriously affected. Gatwick comes to mind as it has displaced thresholds at each end and is probably the busiest single runway airport in the world. Moving holding points at busy airports like Gatwick much further away from the runway so they are outside the approach surface would create significant capacity problems.

[OCEAN WUN ZERO]

I also assumed that there must be some kind of exemption.

However ASD have brought this issue up in a development and appear to be going to be asking why and be compliant at existing runway configurations.


CAP 168 definition

'Obstacle' All fixed (whether temporary or permanent) and mobile objects, or
parts thereof, that are located on an area intended for the surface
movement of aircraft or that extend above a defined surface
intended to protect aircraft in flight, or that stand outside those
defined surfaces and that have been assessed as being a hazard to
air navigation.

As you say if this is enforced major capacity issues will result.
Sounds like a job for some industry representation.
:uhoh:

OWZ

[SimJock]

Hmm... this is from ICAO Annex 14.

"3.12.9 The location of a runway holing position established in accordance with 3.12.3 shall be such that a holding aircraft or vehicle will not infringe the obstacle free zone, approach surface or take-off climb surface or ILS/MLS critical/sensitive area or interfere with the operation of radio navigation aids"

So UK doesn't conform to that International Standard then ?

[OCEAN WUN ZERO]

The UK files differencies from many ICAO standards. Seems however that SRG wish to move toward "compliance" thus causing us to decrease runway capacity on runways that have been deemed safe for many years and all of a sudden are not.
:confused:
OWZ

[Musket90]

OWZ - I think it's right that SRG reduce differences to ICAO therefore giving a more consistent licensing standard at airports in general. In regard to the displaced landing threshold and approach surface issue I'm not sure that airports would accept any enforcement of this if it meant that moving holding points would significantly affect runway capacity as already mentioned. Simply because many airports with displaced thresholds have been operating safely like this for many years and with CAA Knoledge, so maybe it's questionable that the ICAO Annex 14 and CAP168 requirements for this is valid. Time for a review I think.

[SimJock]

Ok, found the disclaimer in the UK AIP ICAO differences, http://www.nats-uk.ead-it.com/aip/current/gen/EG_GEN_1_7_en.pdf, Annex 14, 3.12.3,

"UK permits the location of a runway-holding position that will cause an
infringement of the OFZ by an aircraft."

"Permissible only if no
interference occurs and the
infringement is addressed in the
calculation of the OCA/H."

So.. if there is no aircraft holding there you could lower your minimums ? and I guess that the OCA/H adjustment is based on the the 'largest possible aircraft that could reasonably be expected to be holding there at any time' :hmm:

[OCEAN WUN ZERO]

Well done simjock

I dont think the OFZ is the same as the approach surface? And if it is does this exemption cover both? Seem to remember the OFZ being parallel to the runway and going off at 1:10. The slope that you need to keep glidepath aerials, wind socks etc out of.

OWZ

[Musket90]

Just had a look at CAP168 (Chapter 4) - The OFZ is within the approach surface and is to a distance 60m either side of runway c/l and extended c/l. It's transitional slope is 1:3.

[SimJock]

Had a look at PANS-OPS ICAO 8168, there is no OCA/H adjustment for this situation shown in there so the 'adjustment' must be a non specific obstacle height to be used in the instrument procedure design it seems.

Had a look at CAP232, suprisingly, there is no specific reference to including holding points and the categories of aircraft that might use them into the airfield obstacle survey, although the holding points are surveyed and drawn into the airfield plan of course.

I don't think its really covered by the bit in CAP232 chapter 10 that says:

"Features to be surveyed:
Roads, railways, river or canal features shall have sufficient levels to show their
surface elevation, (in the case of a body of water subject to tides, high and low tidal
variations are required) and the height of the highest mobile feature that could be
expected on them. The features shall include vegetation, hard, mobile and
temporary objects"

[OCEAN WUN ZERO]

So are we saying that any Code 3 or 4 runway that has space to put holding points in the undershoot area must be 150m plus any further distance encompassed by the 15% divergence, away from the centerline and below the 1:50 surface. And that if you already have the potential to hold larger aircraft at these holding points you should not have them there whilst arrivals take place.
If this is the case will it not affect the expedition and runway capacity at a number of the top16 UK airports and possibly a number of European ones.
:)
OWZ