LATERAL NAVIGATION ERRORS

More Common Causes Of Lateral Navigation Errors

13.3.1 The most common causes of GNEs, in approximate order of frequency, have been as follows:

• having already inserted the filed flight plan route co-ordinates into the navigation computers, the crew have been re-cleared by ATC, or have asked for and obtained a clearance, but have then omitted to re-program the navigation system(s), amend the Master Document or update the plotting chart accordingly.

• a mistake of one degree of latitude has been made in inserting a forward waypoint. There seems to be a greater tendency for this error to be made when a track, after passing through the same latitude at several waypoints (e.g. 57°N 50°W, 57°N 40°W, 57°N 30°W) then changes by one degree of latitude (e.g. 56°N 20°W). Other circumstances which can lead to this mistake being made include receiving a re-clearance in flight.

• the autopilot has been inadvertently left in the heading or de-coupled mode after avoiding weather, or left in the VOR position after leaving the last domestic airspace VOR. In some cases, the mistake has arisen during distraction caused by SELCAL or by some flight deck warning indication.

• an error has arisen in the ATC Controller/Pilot communications loop, so that the controller and the crew have had different understandings of the clearance. In some cases, the pilot has heard not what was said, but what he/she was expecting to hear.

SECTION 5 – ETOPS ROUTE PLANNING – DAY-TO-DAY DISPATCH REQUIREMENTS

Prior to crossing the last land based navigation fix, usually referred to as “Coast Out”, the flight crew should complete any required navigation accuracy checks, HF radio and SELCAL checks, and RVSM Altimeter comparisons. This information is typically recorded on an Oceanic Navigation Log (ONL) for analysis by the maintenance department. It is also useful in the extremely unlikely event of a total navigation computer system failure.

Additional actions the flight crew will need to complete on an ETOPS flight are those items associated with entering ETOPS Airspace. This occurs at the first point during the flight where the track is more than the operator’s threshold distance from an Adequate Airport, also known as the ETOPS Entry Point (EEP). In Figure 5.11, the EEP is located approximately 407 nm to the East of St. Johns (CYYT). Prior to the airplane passing the EEP, dispatch is required to contact the flight with updates of weather and field conditions at the three ETOPS Alternates, as well as any other nearby airports that might be considered if a diversion were to become necessary.

If the flight had been dispatched subject to the verification of a corrective maintenance action, referred to as a Maintenance Verification Flight, the flight crew are to notify the company of the results of their observations, and receive authority to continue the flight into ETOPS Airspace.

Maintenance Verification activities are typically limited to confirming that the repaired airplane system is functioning normally. Further discussion on Maintenance Verification Flights is provided in the Boeing ETOPS Guide Volume II.

5.8.2 The ETOPS Portion of the Flight

As the flight progresses into the enroute ETOPS phase, the effective use of the Master Computer Flight Plan document, an Oceanic Navigation Log, and the enroute plotting chart will greatly enhance the conduct of the crossing in accordance with the operator’s Standard Operating Procedures (SOPs).

One of the primary concepts of ETOPS is that the flight crew will be provided sufficient information to maintain good situational awareness of the airplane’s fuel state and position throughout the flight. This requires the dispatch department to give concise pre-flight briefings of anticipated along route conditions as well as accurate Computer Flight Plans. It also requires the flight crew to be diligent in their conduct of the flight by adhering to the companies SOPs for ETOPS and Long Range Navigation.

The use of a Fuel and Time Score Card, sometimes referred to as a “How Goes It”, is a typical method used by most major airlines, to assist flight crew in detecting fuel burn / leak anomalies before they can become a threat to the safety of the flight. There are many methods used by the worlds airlines to track the fuel/time progress of long range flights. An Oceanic Navigation Log (ONL) is one method. An partially filled out example ONL is shown in Figure 5.12

Dispatch should continue to monitor the status the ETOPS alternates and other nearby airports.

SECTION 5 – ETOPS ROUTE PLANNING – DAY-TO-DAY DISPATCH REQUIREMENTS

Captain ____________ First Officer __________ RO

ATC ADDRESSEE NEW YORK NEW YORK NEW YORK SANTA MARIA

POSITION LONG 60W 50W 40W 30W

or FIX ETA Z @ 0324 Z @ Z @ Z @ Z

Figure 5.12 Example Oceanic Navigation Log

The ONL is used to record and document, for easy reference during the flight, the details of each Oceanic Waypoint crossing. Each column represents an oceanic waypoint, which the flight crew fill in as the flight progresses. In the above example, the crew have filled out in advance, some of the information for waypoints that the flight will cross, and have filled in all of the pertinent data for the first waypoint, BALOO, that the flight crossed at 0308Z. The order of the information on the example ONL follows the Standard Position Report Sequence, allowing the pilot to read the required items directly when making the position report to ATC. The Fuel /

SECTION 5 – ETOPS ROUTE PLANNING – DAY-TO-DAY DISPATCH REQUIREMENTS

Time Score section shows that the flight is 1 minute ahead of plan (-1) and has burned 100 kg more fuel than planned (+0.1).

The MNPS Manual (2005 Edition), which has been quoted previously, contains a wealth of information pertinent to any Long Range Navigation and/or ETOPS flights, and operator’s are encouraged to consult it when developing their own SOPs for Long Range Nav. One additional excerpt from chapter 8 of the MNPS manual is appropriate at this point, dealing with the use of the enroute plotting chart. An example of a partially completed enroute chart with ETPs and Post Position Plot points is shown in Figure 5.13

“Position Plotting

8.2.9 A simple plotting chart provides a visual presentation of the intended route which, otherwise, is defined only in terms of navigational co-ordinates.

Plotting the intended route on such a chart may reveal errors and discrepancies in the navigational co-ordinates which can then be corrected immediately, before they reveal themselves in terms of a deviation from the ATC cleared route. As the flight progresses, plotting the aircraft's position on this chart will also serve the purpose of a navigation cross check, provided that the scale and graticule are suitable.

8.2.10 As the flight progresses in oceanic airspace, plotting the aircraft's position on this chart will help to confirm (when it falls precisely on track) that the flight is proceeding in accordance with its clearance. However, if the plotted position is laterally offset, the flight may be deviating unintentionally, and this possibility should be investigated at once.

8.2.11 It is recommended that a chart with an appropriate scale be used for plotting. Many company Progress Charts are of the wrong scale or too small. It has been noted that the use of plotting charts that are small can lead to oceanic errors. EAG Chart NAT (H/L) 1&1e; No 1 AIDU (MOD) Charts AT(H)1, 2, 3 & 4 and the Jeppesen North/Mid Atlantic Plotting Charts are all useful compromises between scale and overall chart size; while the NOAA/FAA North Atlantic Route Chart has the advantage, for plotting purposes, of a 1° latitude/longitude graticule."

One final quote from Chapter 14 of the MNPS Manual, where listed among the “cures” for oceanic navigation errors, plotting charts are again mentioned:

Plot your Present Position regularly on your chart. – this may seem old-fashioned but, since the present position output cannot normally be interfered with and its calculation is independent of the waypoint data, it is the one output which can be

SECTION 5 – ETOPS ROUTE PLANNING – DAY-TO-DAY DISPATCH REQUIREMENTS

Figure 5.13 Example ETOPS and Long Range Navigation Plotting Chart ETP3 @ 46N030W

280 nm from previous reporting point

Airports LPA / SNN

Filed on NAT Y

Adjacent and Crossing Tracks W, X & Z also plotted

First Post-Position Plot is not on planned track

Second Post-Position Plot shows return to planned track

SECTION 5 – ETOPS ROUTE PLANNING – DAY-TO-DAY DISPATCH REQUIREMENTS

5.8.3 ETOPS Data Collection

The collection of Engine Conditioning (ECM) and Airplane Performance Monitoring (APM) Data is typically performed by flight crew on airplanes that do not have automatic data collection capability. If the data is to be collected manually, it is important that it be done in stable

conditions, to the extent practical. Boeing’s APM Program is available to operators detail guidance on collecting and analyzing the data. The data collected in accordance with the Boeing APM Program guidelines will typically be satisfactory for most engine manufacturer’s Engine Condition Monitoring Programs as well.

Approximately one hour prior to descent, if the operator has identified the flight as an APU Inflight Start flight, the crew will need to conduct the start and fill out the appropriate forms for maintenance. APU Inflight Starts on ETOPS flights are typically limited to the return to home base flight. Multiple start attempts may be performed within the limits stated in the Airplane Flight Manual and the Airplane Maintenance Manual, Chapter 49. Consideration should be given to performing the final start attempt within the route or track constraints as defined by ATC.

Additional information on APU Inflight Start Programs can be found in the Boeing ETOPS Guide Volume II.

One of the final ETOPS activities conducted prior to descent on some models is the cycling of the fuel crossfeed valve. Operator’s should consult the Configuration, Maintenance and Procedures (CMP) document for their aircraft to determine if this s procedure is required.

SECTION 5 – ETOPS ROUTE PLANNING – DAY-TO-DAY DISPATCH REQUIREMENTS

This Page Intentionally Left Blank

SECTION 6 - TRAINING