Erroneous ILS Indications Pose Risk of Controlled Flight Into Terrain

FLIGHT SAFETY FOUNDATION JULY 2002 FLIGHT SAFETY DIGEST Erroneous ILS Indications Pose Risk of Controlled Flight Into Terrain SINCE 1947 FLIGHT SAFETY FOUNDATION For Everyone Concerned With the Safety of Flight Flight Safety Digest Officers and Staff Vol. 21 No. 7 July 2002 Hon. Carl W. Vogt Chairman, Board of Governors In This Issue Stuart Matthews President and CEO Erroneous ILS Indications Pose Risk of Robert H. Vandel 1 Executive Vice President Controlled Flight Into Terrain James S. Waugh Jr. Several incidents involved flight crews who observed normal, Treasurer on-course instrument landing system (ILS) indications ADMINISTRATIVE although their aircraft were not established on the glideslope Ellen Plaugher or on the localizer course. Special Events and Products Manager Linda Crowley Horger U.S. Corporate, Business and Manager, Support Services On-demand Operations Show 20 FINANCIAL Reduced Accident Rates for 2001 Crystal N. Phillips Director of Finance and Administration General aviation as a whole posted higher accident rates for the year compared to 2000 based on a recent analysis. TECHNICAL James Burin Report Provides Safety Data for Director of Technical Programs 24 Joanne Anderson Use in Accident Prevention Technical Programs Specialist The report by the International Air Transport Association, Louis A. Sorrentino III which is part of a safety information package, identifies areas Managing Director of Internal Evaluation Programs of concern and high risk and recommends methods of Robert Feeler improvement. Q-Star Program Administrator Robert Dodd, Ph.D. Manager, Data Systems and Analysis Precautionary Landing of B-767 Darol V. Holsman Prompted by Fumes, Smoke-detector 27 Manager of Aviation Safety Audits Alert MEMBERSHIP Inspections by maintenance personnel revealed that the Ann Hill fumes were caused by the release of chemical compounds Director, Membership and Development in the protective coating on the airplane’s secondary heat Kim Granados exchanger. Membership Manager Ahlam Wahdan Membership Services Coordinator PUBLICATIONS Roger Rozelle Director of Publications Mark Lacagnina Senior Editor Wayne Rosenkrans Senior Editor Linda Werfelman Senior Editor Karen K. Ehrlich Web and Print Production Coordinator Cover photo: Copyright @2002 Getty Images Inc. Ann L. Mullikin Production Designer Flight Safety Foundation is an international membership organization dedicated Susan D. Reed to the continuous improvement of aviation safety. Nonprofit and independent, Production Specialist the Foundation was launched officially in 1947 in response to the aviation Patricia Setze industry’s need for a neutral clearinghouse to disseminate objective safety Librarian, Jerry Lederer Aviation Safety Library information, and for a credible and knowledgeable body that would identify threats to safety, analyze the problems and recommend practical solutions to them. Since its beginning, the Foundation has acted in the public interest to produce positive influence on aviation safety. Today, the Foundation provides Jerome Lederer leadership to more than 850 member organizations in more than 140 countries. President Emeritus Erroneous ILS Indications Pose Risk of Controlled Flight Into Terrain Several incidents involved flight crews who observed normal, on-course instrument landing system (ILS) indications although their aircraft were not established on the glideslope or on the localizer course. FSF Editorial Staff On May 11, 2001, the International Civil Aviation Organization Air New Zealand said, in its report on the incident, that the (ICAO) sent a letter to the civil aviation authorities in its 187 flight crew discussed notices to airmen (NOTAMs) for Faleolo contracting states advising that “a number of incidents … have before departing from Auckland.3 occurred in recent years resulting from the operational use of instrument landing system (ILS) signals being radiated during One NOTAM said that the glideslope equipment for the ILS testing-and-maintenance procedures.”1 Runway 08 ILS approach was operating without a functional standby transmitter. (The glideslope equipment included two The letter, signed by ICAO Secretary General R.C. Costa transmitters; one of the transmitters was not functional because Pereira, said that ILS signals radiated during testing or it had a faulty power amplifier. The report said that the ILS maintenance of ground equipment can cause aircraft had been operating without a functional standby glideslope navigation instruments to display on-course indications and/ transmitter since late May 2000.) or on-glideslope indications, with no warning flags, regardless of the actual position of the aircraft within the Two other NOTAMs advised caution when using the glideslope ILS service area. and the distance-measuring equipment (DME) associated with the ILS approach because the glideslope and the DME were “The use of ILS localizer and/or [glideslope] signals for approach operating in an unmonitored status. (The approach procedure guidance during these testing-and-maintenance procedures can included the use of information from the DME collocated with therefore result in false indications to the flight crew and has the ILS, rather than marker beacons, because a portion of the the potential to cause a controlled-flight-into-terrain (CFIT) final approach is over water.) accident,” the letter said.2 (See “Recommendations for Protection Against Erroneous ILS Indications,” page 2.) ICAO recommends monitoring of ILS components — including localizer transmitters, glideslope transmitters, marker beacons One incident occurred the night of July 29, 2000, at Faleolo (or DME used in lieu of marker beacons) — both by automatic International Airport, which is near Apia on the northwest coast monitoring equipment installed near the ILS components and of Upolu Island, Samoa (formerly Western Samoa). The by air traffic specialists using remote-control-and-indicator incident involved a Boeing 767-300 that was being operated equipment installed in the airport control tower, approach-control as Air New Zealand Flight NZ 60, a scheduled flight to Faleolo facility and/or flight service station (see “ICAO Annex 10 Sets from Auckland, New Zealand, with three flight crewmembers, Standards for ILS Equipment,” page 4). eight cabin crewmembers and 165 passengers. Continued on page 3 FLIGHT SAFETY FOUNDATION • FLIGHT SAFETY DIGEST • JULY 2002 1 Recommendations for Protection Against Erroneous ILS Indications The following recommendations, from several sources, are intended to help flight crews avoid accidents involving Table 1 erroneous instrument landing system (ILS) indications Recommended Elements caused by instrument error or by reception of localizer signals or glideslope signals — generated during maintenance/ Of a Stabilized Approach testing of ILS ground equipment or because of maintenance All flights must be stabilized by 1,000 feet above error — that are not intended to be used for navigation. airport elevation in instrument meteorological Included are recommendations that have resulted from Flight conditions (IMC) and by 500 feet above airport Safety Foundation’s continuing worldwide campaign to help elevation in visual meteorological conditions (VMC). reduce approach-and-landing accidents, including those An approach is stabilized when all of the following involving controlled flight into terrain (CFIT).1,2,3 criteria are met: 1. The aircraft is on the correct flight path; • Be aware of the possibility of erroneous ILS indications, 2. Only small changes in heading/pitch are required including the nonappearance of warning flags; to maintain the correct flight path; 3. The aircraft speed is not more than V + 20 • Check notices to airmen (NOTAMs) prior to flight to REF knots indicated airspeed and not less than VREF; determine the operational status of ILS components; 4. The aircraft is in the correct landing configuration; 5. Sink rate is no greater than 1,000 feet per minute; • Ensure that any reported discrepancies in the if an approach requires a sink rate greater than operation or functioning of ILS receivers and/or 1,000 feet per minute, a special briefing should be indicators have been addressed adequately by conducted; maintenance personnel according to provisions of the 6. Power setting is appropriate for the aircraft aircraft’s minimum equipment list (MEL); configuration and is not below the minimum power for approach as defined by the aircraft operating •Ten minutes before beginning descent from cruise manual; altitude, conduct an interactive approach briefing that 7. All briefings and checklists have been conducted; includes: the use of automatic flight control system (AFCS) modes; use of the radio altimeter; minimum 8. Specific types of approaches are stabilized if they also fulfill the following: instrument landing safe altitudes; terrain features (e.g., location and system (ILS) approaches must be flown within elevation of hazardous terrain or man-made obstacles); one dot of the glideslope and localizer; a and typical vertical speed at the expected final Category II or Category III ILS approach must be approach groundspeed; flown within the expanded localizer band; during a circling approach, wings should be level on • Conduct a stabilized approach (see Table 1); final when the aircraft reaches 300 feet above airport elevation; and, • Maintain situational awareness throughout the 9. Unique approach procedures or abnormal approach; conditions requiring a deviation from the above elements of a stabilized approach require

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