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View Full Version : The Lateral Offset Tracking Trial Concludes this Coming Saturday


TheShadow
29th Oct 2003, 13:51
Interested in

1. Any additional knowledge about the outcome of this lateral offset tracking trial and the prospects for the procedure being actually adopted internationally.

2. Agreement/disagreement with sentiments expressed here - from an email received (about the US DRVSM Final Rule that's just been released - see Federal Register). Correspondent says:

Previous link (on official RVSM website) is now dead (a bit mysterious). This link below works and the document is reproduced below. NOTE THAT

THE TRIAL ENDS on 01 Nov 2003 (next Saturday). The importance of this airways track offsetting procedure then actually being adopted is that the:

a. Incidence of TCAS alerts will be reduced under RVSM - particularly for aircraft in climb or descent (or carrying undetected altimetric error)

b. Outcome of pilot or ATC error will be reduced (whereas nowadays MNPS-dictated navigational accuracy could almost ensure a midair collision - per the two links below).

c. The prospect of catastrophic high-speed unalerted A380 induced wake turbulence encounters will be much reduced by the 2nm lateral offset. This safer development will apply only to opposite direction traffic of course. Same direction traffic will still be liable to upsets if following an A380 and only 1000ft below its cruising level. In fact I advocate right now that ATC will have to globally incorporate a practise of having any traffic within 5 mins or 45nm behind an A380 at least level and staggered upwards (e.g. preceding A380 at FL360 then closely following/crossing traffic, even another A380, must be at FL360 or above - never higher than at least 2000ft below its level). It's my understanding that under RVSM your tracking still dictates the availability of particular Flight Levels - but it was still addressed below in the NOTAM as concern.

WATRS_LATERAL_OFFSET_NOTAM_Nov_28_02.doc (http://www1.faa.gov/ats/ato/150_docs/WATRS_LATERAL_OFFSET_NOTAM_Nov_28_02.doc)

The case for staggered airways tracking (http://www.pprune.org/go.php?go=/pub/tech/MidAir.html)

The Delhi Saudi 747/Kazakhstan Collision (http://www.pprune.org/go.php?go=/pub/tech/MidAir2.html)

WATRS LATERAL OFFSET NOTAM Nov 28 02
STRATEGIC LATERAL OFFSET OPERATIONAL TRIAL IN THE NEW YORK (NY) OCEANIC FIR WEST OF 60 WEST AND SOUTH OF 38-30 NORTH

It has been determined that allowing aircraft conducting oceanic flight to fly lateral offsets not to exceed 2 NM right of centerline will provide additional safety margin and mitigate the risk of conflict when non-normal events such as aircraft navigation errors, height deviation errors and turbulence induced altitude-keeping errors occur.

Effective 24 January 2002 at 0901 UTC the NY Oceanic FIR portion of WATRS airspace between FL 290 and 410 (inclusive) will be designated as RVSM exclusionary airspace. The WATRS area has a high frequency of opposite direction traffic. This strategic lateral offset trial became effective on 1 November 2001. The operational trial was planned on being in effect for one year, expiring 1 November 2002. The trial period has been extended for an additional year, with a new expiration date of 1 November 2003.

This procedure provides for offsets within the following guidelines. Along a route or track there will be three positions that an aircraft may fly: centerline or one or two miles right. Offsets will not exceed 2 NM right of centerline. The intent of this procedure is to reduce risk (add safety margin) by distributing aircraft laterally across the three available positions.

For the duration of this trial, this procedure should also be used to avoid wake turbulence. In lieu of the existing wake turbulence offset procedures, pilots should only fly one of the three positions shown above. (See paragraph 4 below).For the purpose of this trial, this procedure is applicable in the NY Oceanic FIR west of 60 west longitude and south of 38 degrees, 30 minutes north latitude between FL 290-410 (inclusive). The procedure is as follows:

1. Aircraft without automatic offset programming capability must fly the centerline.

2. Operators capable of programming automatic offsets may fly the centerline or offset one or two nautical miles right of centerline to obtain lateral spacing from nearby aircraft. (Offsets will not exceed 2 NM right of centerline).

3. Pilots shall apply this authority in the area of NY Oceanic FIR identified. Pilots should use whatever means is available (e.g. TCAS, communications, visual acquisition, GPWS, ADS-B) to determine the best flight path to fly.

4. Pilots should also fly one of the three positions shown above to avoid wake turbulence. Aircraft should not offset to the left of centerline nor offset more than 2 NM right of centerline. Pilots may contact other aircraft on the air to air frequency, 123.45, as necessary, to coordinate the best wake turbulence offset option. As noted below, contact with ATC is not required.

5. Due to the frequency of opposite direction traffic in the New York Oceanic FIR, it is recommended that aircraft normally fly an offset of 1 or 2 NM right.

6. Offsets may be applied outbound at the time that radar contact is terminated. Aircraft must return to centerline when radar contact is re-established.

7. There is no ATC clearance required for this procedure and it is not necessary that ATC be advised. (ATP-

skibeagle
29th Oct 2003, 15:15
Hello Shadow,

I haven't been that far South on the Atlantic for a while, so I was unaware of this trial.

Many of us that operate in Africa apply our own 1 or 2 mile right deviation due to the poor standards of ATC in the region, but that is less of a concern on the Atlantic with CPDL and the like coming into fashion. Also, Africa is as yet non-RVSM.

One point comes to mind though, suppose the A380 (or even a smaller aircraft like the 767 for that matter) was flying Eastward offset right two miles and a B757 was Westbound also offset two miles right and 1000 feet below the A380's level. If there was a wind of sufficient strength from the South, it could still effect the 757, in fact, it could be detrimental to fly offsets while flying opposing tracks for this reason.

It is well know that wake turbulence sinks and fans outwards behind the developing aircraft and that it also drifts with wind effect. So, my concern in this environment would be just who would be delegating (or recommending) which offset to use, if any.

I would say that if the upwind (crosswind that is) aircraft is higher on opposite tracks, it is better to have both aircraft fly center line, whereas same direction traffic would be better having the higher aircraft offset right for a wind from the left and the lower aircraft offset right for a wind from the right.

Of course, this has to be managed continuously on the NAT tracks, preferably by the crews themselves - IMHO, which is exactly what the NY Oceanic ATC are recommending. I had a rule of thumb on the Atlantic for same direction traffic, for every 0.01 mach difference and each 1000 feet allow 20 minutes for likely wake turbulence conflict (I personally liked precautionary seat belt sign usage). So e.g. an aircraft 2000 feet above and 0.02 mach faster could likely cause problems for a lower aircraft forty minutes after passing overhead.

You can probably tell that I have absolutly nothing better to do with my time than write stupid posts like this.:ugh:

MTOW
29th Oct 2003, 16:36
It should be mandatory in the cruise when not under radar vectors (ie, HDG SEL). I'd like to see it built into the FMS so it just happened automatically above a given altitude if in LNAV mode.

The increased safety it affords is so obvious I just can't understand the resistance to it.