NTSB Press Release
National Transportation Safety Board
Office of Public Affairs
Public Meeting of June 17, 1997 Abstract of Final Report Descent Below Visual Glidepath and Collision with Terrain Delta Air Lines Flight 554, McDonnell Douglas MD-88 LaGuardia Airport, New York October 19, 1996 (ADDITIONAL CONCLUSIONS AND RECOMMENDATIONS MAY BE ADDED)
June 17, 1997
EXECUTIVE SUMMARY
About 1638 eastern daylight time, on October 19, 1996, a McDonnell Douglas MD-88, N914DL, operated by Delta Air Lines, Inc., as flight 554, struck the approach light structure and the end of the runway deck during the approach to land on runway 13 at the LaGuardia Airport, in Flushing, New York. Flight 554 was being operated under the provisions of 14 CFR Part 121, as a scheduled, domestic passenger flight from Atlanta, Georgia, to Flushing. The flight departed the William B. Hartsfield International Airport at Atlanta, Georgia, about 1441, with two flightcrew members, three flight attendants, and 58 passengers on board. Three passengers reported minor injuries; no injuries were reported by the remaining 60 occupants. The airplane sustained substantial damage to the lower fuselage, wings (including slats and flaps), main landing gear, and both engines. Instrument meteorological conditions prevailed for the approach to runway 13; flight 554 was operating on an instrument flight rules flight plan.
Safety recommendations concerning these issues were addressed to the Federal Aviation Administration and to optometric associations.
Conclusions
1. The pilots held appropriate flight and medical certificates; they were trained and qualified for the flight, and were in compliance with the Federal regulations on flight and duty time. However, the captain was using monovision contact lenses, which were not approved by the FAA for use by pilots while flying.
2. The flight attendants had completed Delta's Federal Aviation Administration-approved flight attendant training program.
3. The airplane was properly certificated, and there was no evidence that airplane maintenance was a factor in the accident.
4. No air traffic control factors contributed to the cause of the accident.
5. Delta Air Lines provided the pilots with adequate preflight, en route, and arrival weather information to conduct the flight safely; however, because of rapidly changing surface conditions, the conditions they encountered differed from what was forecast. (to be revised)
6. Although the weather conditions encountered by the pilots during the approach differed from the forecast conditions, these conditions should not have affected the pilots' ability to conduct a safe approach and landing.
7. Delta flight 554 did not encounter windshear during its approach to runway 13 at LaGuardia.
8. Because the airplane was in stable flight and the captain had taken actions to correct for the glideslope deviation, the captain's continuation of the approach after he established visual contact with the approach lights was not inappropriate.
9. The captain gradually reduced the engine power because he perceived a need to slightly increase the airplane's rate of descent; however, the descent rate increased beyond what the captain likely intended to command.
10. Irregular and shortened runway edge light spacing and degraded weather conditions can result in a pilot making an unnecessarily rapid descent and possibly descending too soon, especially in the absence of other visual references or cues.
11. The captain's use of monovision contact lenses resulted in his (unrecognized) degraded depth perception, and thus increased his dependence on monocular cues (instead of normal three-dimensional vision) to perceive distance.
12. Because of the captain's use of monovision contact lenses, he was unable to overcome the visual illusions resulting from the approach over water in limited light conditions (absence of visible ground features), the irregular spacing of the runway edge lights at shorter-than-usual intervals, the rain, and the fog, and that these illusions led the captain to perceive that the airplane was higher than it was during the visual portion of the approach, and thus, to him unnecessarily steepening the approach during the final 10 seconds of the approach.
13. During the visual portion of the approach, when the captain was primarily relying on visual cues, the first officer, who was primarily monitoring cockpit instrumentation to gauge the airplane's position with regard to the runway, provided input to the captain that surpassed what was set forth in the guidance available to the pilots at that time.
14. The Delta manuals were not sufficiently specific regarding pilot-not-flying duties during Category I instrument landing system approaches after the pilot flying establishes ground contact.
15. Although Delta's manuals did not adequately specify operational criteria for a stabilized approach, the lack of guidance in this area did not contribute to the accident.
16. Aviation medical examiners (AMEs) need to know if pilot examinees are using contact lenses, and currently no process is in place to ensure that AMEs are provided with that information.
17. Information concerning the possible hazards of monovision contact lens use is not well disseminated among optometrists and the pilot population.
18. The lag time in the display of vertical speed information in the vertical speed indicator installed in the accident airplane limited the first officer's ability to provide the captain with precise vertical speed information during the critical final seconds of the approach, and therefore contributed to the accident.
19. The Federal Aviation Administration's current guidance on special airports contained in Advisory Circular 121.445-1D is not sufficiently specific about criteria and procedures for designation of special airports; therefore, the FAA's current guidance might not always be useful to air carriers operating in and out of (existing or potential) special airports.
20. The present requirements for special airport pilot qualifications might not be sufficient to ensure that pilots who are so qualified have been exposed to the runways and/or approaches at those airports that make the airport "special."
21. The captain's decision to evacuate the airplane was appropriate for the circumstances and was made in a timely manner.
22. The flight attendant in charge reacted to the captain's evacuation command promptly and assertively, in accordance with Delta's flight attendant manuals and training.
23. The quality of the crew resource management was not a factor in this accident.
24. The atypical installation and use of runway visual range transmissometer equipment at LaGuardia did not adversely affect the validity of the runway visual range values reported at the time of the accident.
25. The low level windshear alert system equipment anomalies were not a factor in this accident.
Probable Cause
The National Transportation Safety Board determines that the probable cause of this accident was the inability of the captain, because of his use of monovision contact lenses, to overcome his misperception of the airplane's position relative to the runway during the visual portion of the approach. This misperception occurred because of visual illusions produced by the approach over water in limited light conditions, the absence of visible ground features, the rain and fog, and the irregular spacing of the runway lights.
Contributing to the accident was the lack of instantaneous vertical speed information available to the pilot not flying, and the incomplete guidance available to optometrists, aviation medical examiners, and pilots regarding the prescription of unapproved monovision contact lenses for use by pilots.
Safety Recommendations
As a result of the investigation of this accident, the National Transportation Safety Board makes the following recommendations:
--to the Federal Aviation Administration:
1. Identify Part 139 airports that have irregular runway light spacing, evaluate the potential hazards of such irregular spacing, and determine if standardizing runway light spacing is warranted.
2. Require all 14 CFR Part 121 and 135 operators to review and revise their company operations manuals to more clearly delineate flightcrew member (pilot flying/pilot not flying) duties and responsibilities for various phases of flight, and to more clearly define terms that are critical for safety of flight decisionmaking, such as "stabilized approach."
3. Revise FAA Form 8500-8, "Application for Airman Medical Certificate," to elicit information regarding contact lens use by the pilot/applicant.
4. Require the Civil Aeromedical Institute to publish and disseminate a brochure containing information about vision correction options, to include information about the potential hazards of monovision (MV) contact lens use by pilots while performing flying duties and to emphasize that MV contact lenses are not approved for use while flying.
5. Require all 14 CFR Part 121 and 135 operators to notify their pilots and medical personnel of the circumstances of this accident, and to alert them to the hazards of monovision contact lens use by flightcrew members.
6. Require all flight standards district office air safety inspectors and accident prevention specialists to inform general aviation pilots of the circumstances of this accident and to alert them to the hazards of monovision contact lens use by pilots while flying.
7. Expedite the development and publication of specific criteria and conditions for the classification of special airports; the resultant publication should include specific remarks detailing the reason(s) an airport is determined to be a special airport, and procedures for adding and removing airports from special airport classification
8. Develop criteria for "special runways and/or special approaches" giving consideration to the circumstances of this accident and any unique characteristics and special conditions at airports (such as those that exist for the approaches to runways 31 and 13 at LaGuardia Airport) and include detailed pilot qualification requirements for designated special runways or approaches.
9. Once criteria for designating special airports and special runways and/or special approaches have been developed at recommended in Safety recommendations A-97-XXX and -XXX, evaluate all airports certificated under Part 139 Airports against that criteria and update special airport publications accordingly.
--to optometric associations:
10. Issue a briefing bulletin to member optometrists, informing them of the potential hazards of and prohibition against monovision (MV) contact lens use by pilots while performing flying duties, and urging them to advise pilot-rated patients of those potential hazards (MV contact lens' effect on distance judgments/perceptions).
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