June 1, 1999
By Bruce Landsberg
On the anniversary of a major airline accident that occurred almost a quarter of a century ago, the issues of thunderstorm avoidance have not changed. Although the technology has improved, pilots should be as cautious as ever.
On June 24, 1975, Eastern Air Lines Flight 66, a Boeing 727-225 on a flight from New Orleans, arrived in the New York City terminal area, bound for John F. Kennedy International Airport. There was nothing on the automatic terminal information service (ATIS) to indicate any particular problem: "Kennedy weather, VFR, sky partially obscured, estimated ceiling 4,000 broken, five miles with haze. Wind 210 at 10, altimeter 30.15. Expect vectors to an ILS Runway 22L, landing Runway 22L, departures are off 22R...."
The terminal forecast for Kennedy Airport called for thunderstorms and moderate rainshowers after 6 p.m. At 3:45 p.m., the forecast was amended to call for thunderstorms, heavy rainshowers with visibilities as low as one-half mile, and winds from 270 at 30 knots with gusts to 50 kt after 4:15 p.m. There was no evidence that the flight crew of Eastern 66 received any of these forecasts.
At 3:51:54, the arrival controller broadcast, "...we're VFR with a five-mile, light, very light rainshower with haze, altimeter check 30.13...." At 3:52:43, the controller transmitted, "All aircraft this frequency, we just went IFR with two miles, very light rainshowers and haze. The runway visual range is not available, and Eastern 66 descend and maintain 4,000, Kennedy radar one three two four." Eastern 66 acknowledged the frequency change.
At 3:53:22 the flight contacted the Kennedy final controller, who provided radar vectors around thunderstorms in the area and sequenced the flight with other traffic on the localizer course. At 3:57:21 the cockpit voice recover (CVR) tells us that the flight crew discussed the problems of arriving with minimum fuel when confronted with terminal area delays. They checked the alternate weather at La Guardia Airport, in Flushing, New York, and a crewmember remarked, "One more hour and we'd come down whether we wanted to or not." At 3:59:19 the final controller transmitted a message to all air-.craft on his frequency that "a severe wind shift" had been reported on the final approach and that he would report more information shortly.
Eastern Air Lines Flight 902, a Lockheed 1011, had abandoned its approach to Runway 22L at 3:57:30. At 3:59:40, Eastern 902 reestablished radio communications with the Kennedy final controller, and the crew reported, "We had...a pretty good shear pulling us to the right and...down and visibility was nil, nil out over the marker...correction...at 200 feet it was...nothing." The final controller responded, "OK, the shear you say pulled you right and down?" Eastern 902 replied, "Yeah, we were on course and down to about 250 feet. The airspeed dropped to about 10 kt below the bug, and our rate of descent was up to 1,500 feet a minute, so we put takeoff power on and we went around at a hundred feet."
Flying Tiger Flight 161, a Douglas DC-8, preceded Eastern 902 on the approach and landed on Runway 22L about 3:56:15. After clearing the runway, the captain reported to the local controller: "I just highly recommend that you change the runways and...land northwest; you have such a tremendous wind shear down near...the ground on final." The local controller responded, "OK, we're indicating wind right down the runway at 15 kt when you landed." The captain retorted, "I don't care what you're indicating; I'm just telling you that there's such a wind shear on the final on that runway, you should change it to the northwest." The local controller did not respond. At 3:57:55, he transmitted missed approach instructions to Eastern 902 and asked, "...Was wind a problem?" Eastern 902 answered, "Affirmative."
Eastern 902's wind shear report to the final controller was recorded on Eastern 66's CVR. While Eastern 902 was making this report, the captain of Eastern 66 said, "You know this is asinine." Another crewmember re-marked, "I wonder if they're covering for themselves." The final controller asked Eastern 66 if it had heard Eastern 902's report. Eastern 66 replied, "Affirmative."
The controller advised the flight's position as being five miles from the outer marker (OM) and cleared it for an ILS approach to Runway 22L. Eastern 66 acknowledged the clearance at 4:00:54 with "OK, we'll let you know about the conditions." At 4:01:49, the first officer, who was flying the aircraft, called for the final checklist. While the final checklist items were being completed, the captain stated that the radar was, "Up and off...stand by.... I have the radar on standby in case I need it; I can get it off later."
At 4:02:42 the final controller asked Eastern 902, "Would you classify that as severe wind shift, correction, shear?" The flight responded, "Affirmative."
At 4:02:50 the first officer of Eastern 66 said, "Gonna keep a pretty healthy margin on this one." An unidentified crewmember said, "...would suggest that you do." The first officer responded, "In case he's right."
At 4:02:58 Eastern 66 reported over the outer marker, and the final controller handed the flight off to Kennedy Tower. At 4:03:12 the flight established communications with the Kennedy Tower local controller and reported that it was "Outer marker, inbound."
At 4:03:44 the Kennedy Tower local controller cleared Eastern 66 to land. The captain acknowledged the clearance and asked, "Got any reports on braking action?" The local controller responded that there were no adverse reports.
At 4:04:38 the aircraft was nearly centered on the glideslope when the flight engineer called, "500 feet." The airspeed was oscillating between 140 and 148 kt. The sound of heavy rain was heard on the cockpit voice recorder as the aircraft descended below 500 feet, and the windshield wipers were switched to high speed.
At 4:04:40 the captain said, "Stay on the gauges." The first officer responded, "Oh, yes. I'm right with it."
At 4:04:45 National Air Lines Flight 1004 asked the local controller, "Everyone else having a good ride through?" At 4:04:58 the local controller responded, "Eastern 66 and National 1004, the only adverse reports we've had about the approach is a wind shear on short final." National 1004 acknowledged that transmission — Eastern 66 did not.
At 4:04:48 the flight engineer said, "Three greens, 30 degrees, final checklist," and the captain responded, "Right."
At 4:04:52 the captain said, "I have approach lights," and the first officer said, "OK." Again, the captain said, "Stay on the gauges," and the first officer replied, "I'm with it."
Eastern 66 passed through 400 feet, and its rate of descent increased from an average of about 675 feet per minute to 1,500 fpm. The aircraft rapidly began to slip below the glideslope, and four seconds later, the airspeed decreased from 138 kt to 123 kt in 2.5 seconds. The aircraft continued to deviate farther below the glideslope, and at 4:05:06, when the aircraft was at 150 feet, the captain said, "Runway in sight." Less than a second later, the first officer said, "I got it." The captain replied, "Got it?"
At 4:05:10 an unintelligible exclamation was recorded, and the first officer commanded, "Takeoff thrust." The sound of impact was recorded at 4:05:11.
Two flight attendants who had been seated in the aft portion of the 727's passenger cabin later described the approach as normal with little or no turbulence. According to one of the attendants, the aircraft rolled to the left, and she heard engine power increase significantly. The aircraft then rolled upright and rocked back and forth. She was thrown forward and then upright; several seconds later she saw the cabin emergency lights illuminate and oxygen masks drop from their retainers. Her next recollection was the escape from the wreckage. One hundred thirteen passengers and crewmembers died in the crash. There were 11 survivors.
Witnesses near the middle marker for Runway 22L saw the aircraft at a low altitude and in heavy rain. It first struck an approach light tower that was located about 1,200 feet southwest of the middle marker; it then struck several more towers, caught fire, and came to rest on a highway. Five witnesses located along the localizer course, about 1.6 miles from the threshold of Runway 22L to near the middle marker, described the weather conditions when Eastern 66 passed overhead as heavy rain, lightning, and thunder, with the wind blowing hard from directions ranging from north through east. Witnesses a half-mile south of the accident site, however, stated that no rain was falling at their location when they saw the crash. The visibility to the northeast was good, but visibility to the north was reduced.
The captain of Flying Tiger 161 stated that during his approach he experienced severe changes of wind direction, turbulence, and downdrafts between the outer marker and the airport. He observed airspeed fluctuations of 15 to 30 kt, and at 300 feet, he applied almost maximum thrust to arrest the descent and maintain 140 kt. The aircraft began to drift rapidly to the left, and he eventually had to apply almost 30 degrees of heading correction to overcome the drift. The captain stated that the conditions were so severe that the flight would not have been able to abandon the approach after he had applied near-maximum thrust, and therefore he landed.
The captain of Eastern 902 stated that he flew into heavy rain near 400 feet. The indicated airspeed dropped from about 150 kt to 120 kt in seconds, and his rate of descent increased significantly. The aircraft moved to the right of the localizer course, and he abandoned the approach. He was unable to arrest the aircraft's descent until he had established a high nose-up attitude and had applied near maximum thrust. The aircraft descended to about 100 feet before it began to climb.
Two other aircraft — Finnair Flight 105, a DC-8, and N240V, a Beech Baron — followed Eastern 902 on the approach. Their pilots stated that they also experienced significant airspeed losses and increased rates of descent. However, they were able to cope with the problem because they had been warned of the wind shear condition and had increased airspeed substantially to compensate. Neither pilot reported the condition because they said it had already been reported.
Flying Tiger 161, Eastern 902, and Finnair 105 preceded Eastern 66 on the approach by eight minutes 59 seconds, seven minutes 28 seconds, and six minutes 45 seconds, respectively. Flying Tiger 161's flight data recorder showed that after the flight had descended through 500 feet, its airspeed decreased from 154 to 137 kt within 10 seconds and the rate of descent increased from 750 fpm to 1,650 fpm.
About eight minutes before the accident, the National Weather Service weather radar located at Atlantic City, New Jersey, showed an area of thunderstorm activity along the northern edge of Kennedy Airport. The area, oriented west-northwest to east-southeast, was 30 to 35 miles long and about 15 miles wide. Several groups of thunderstorm cells had tops that exceeded 50,000 feet. About the time of the accident, the largest group of cells, moving east-southeast at a speed of 30 to 35 kt, merged with a smaller group of cells, moving east-northeast at a speed of about 20 to 25 kt. The cells merged over the approach course to Runway 22L. This information was not available to ATC or flights operating in the area.
Could a jet airliner fly through these conditions and survive? Eastern 902 and Eastern 66 had flown through similar conditions, according to their flight data recorders, but Eastern 66 was closer to the runway threshold. The analysis showed that the flight encountered an increasing headwind as it descended on the glideslope. The wind increased from 10 kt at 600 feet above ground level to 25 kt only 100 feet lower. The aircraft then encountered a downdraft of about 960 fpm that increased rapidly to more than 1,200 fpm. The headwind dropped from more than 20 kt to only five kt in just four seconds. Eastern 66 slipped rapidly below the glideslope during this encounter. The National Transportation Safety Board believed that these conditions might exceed the climb capability of the Boeing 727.
A visual Boeing 727 flight simulator was programmed with the estimated wind conditions to see how pilots would react. Fifty-four approaches were flown by different pilots. Eighteen resulted in crashes and there were 31 successful missed approaches. Only five approaches produced successful landings. The element of surprise was missing, which biased the results of the test, but eight of 10 pilots believed that they would have crashed during actual flight. The simulator tests showed that most pilots applied less engine power and less back pressure on the control yoke than they had thought, resulting in sub-optimal performance of the aircraft.
Hindsight always clarifies the view — and two questions prompted by this incident are why the tower did not change runways, and why the pilot did not request a different runway after the wind shear reports. As previously mentioned, the surface wind instruments indicated that the wind favored Runway 22L. The realities of operations in high-density airports during prime time show why even seemingly simple changes are not made. The tower failed to recognize a problem despite the reports of shear. Other flights had landed successfully, and it would have taken ATC approximately half an hour to reconfigure for a different runway. Likewise, pilots depend, at least partially, on the reports of other aircraft ahead to decide whether to continue. If a change to other than the duty runway is requested, a flight may well be delayed for 30 minutes or more to coordinate a nonstandard arrival. Frequently that is the reserve fuel cushion, so going against the flow is done only under duress. The crew's comments regarding remaining fuel showed their concern.
The NTSB concluded that the accident involving Eastern 66 — and the near accidents of Flying Tiger 161 and Eastern 902 — resulted from the un-derestimation of the severe weather conditions by all parties involved. "Pilots must exercise more independent judgment when confronting severe weather conditions in the terminal area. Air traffic con-trollers...must closely follow the development of severe weather conditions by gathering...and disseminating information from all sources — radar, visual, pilot reports, and weather reports — so that appropriate action can be planned before air safety is threatened. Air carrier and National Weather Service forecasters must emphasize the accurate and timely forecasting and reporting of severe weather conditions."
From the analysis of this accident the terms downburst and microburst were coined by scientist Theodore Fujita. They describe the downward rushing of winds out of a thunderstorm that results in high sink rates and airspeed loss. One finding is that timing is everything. A previous aircraft on departure or approach may encounter no problem, but the subsequent one will crash. Doppler radars, low-level wind shear alerting systems, and a much higher level of awareness have helped us to predict the location of these phenomena with more accuracy but not with complete certainty. Since Eastern 66, several air carrier aircraft have been lost to thunderstorms in wind shear encounters during takeoff or landing.
For pilots flying light aircraft, the decisions remain much as they have always been — gather as much information as possible from other flights in the area and from ATC/FSS. Believe your eyes — if it looks bad, it probably is. Wind shear, downbursts, and microbursts can exceed your climb capability. They will not be present with every thunderstorm, so beating the tiger once is no guarantee that you won't lose in a future encounter.
See also the index of "Safety Pilot" articles, organized by subject. Bruce Landsberg is executive director of the AOPA Air Safety Foundation.
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