The Crash of Icelandic Airlines flight LL001 — Part 2

The aftermath

he tragic crash of Flight LL001,(Part 1 of this story is here) a Douglas DC-8–63CF operated by Icelandic Airlines and chartered by Garuda Indonesia, in November 1978 sent shock waves through Sri Lanka. The island was just emerging from a long period of self-imposed isolation, with a new government determined to open the country to outside investment. Building an export-based industrial base was a priority. Expanding the country’s nascent tourist industry was also a goal, and to that end a brand-new airline was to be founded to take over from the ailing Air Ceylon.

Colombo airport circa 1978. It was not exactly busy. DP collection

Years of neglect and poor decisions had reduced Air Ceylon to a shadow of its former self. Founded in 1947, the airline had never achieved its potential. A Presidential Commission to investigate its shortcomings had led to a damning report published in July 1978. The situation was so bad that the government had decided to let Air Ceylon wither away, and a fresh start made by setting up a new company named Air Lanka as the national carrier.

The accident investigation

Many years of relative isolation had also led to much of the country’s infrastructure being in a sorry state. The airports were no exception, but the crash of the Martinair flight in 1974 had led to some improvements. However, these too had proved to be lacking, as some vital equipment (such as the Approach Lighting System — ALS) was not working on the night of the Icelandic crash, while the electrical power supply to the airport was best described as ‘erratic’.

Aircraft accidents are investigated closely, in order to not only ascertain what happened, but also to learn from any shortcomings so as to prevent similar occurrences in the future. A multi-disciplinary team with representatives from the aircraft manufacturer, the operator, the airline, and the country where it occurred work together to determine the facts and make recommendations for the future.

Crowds at the crash site. DP collection

In this case the Government of Sri Lanka appointed a former Supreme Court judge, Justice Siva Supramaniam to inquire into “…the causes and circumstances… (of the accident) … “To consider whether any degree of responsibility … may be attributed to any one person” and “To recommend what steps, if any, should be taken to ensure the avoidance of similar accidents in the future.”[i]

At the time Sri Lanka was still functioning under the Air Navigation Regulations last amended 22 years earlier, in 1956. There were no professional aircraft accident investigators in the country, and expertise was lacking in many disciplines essential for conducting such an in-depth inquiry.

The basic facts

Icelandic LL001 had been on a fairly routine instrument approach to Katunayake airport on what might be described as ‘a dark and stormy night’, but weather conditions were not extreme. The crew had sighted the runway well before the Minimum Descent Altitude (MDA), as is evident from conversation on the Cockpit Voice Recorder (CVR), one of the two components of the so-called ‘black box’ that record vital information on every commercial flight. The DC-8 was fitted with older analogue ‘black boxes’ with a limited amount of data, making an exact reconstruction of the accident challenging.

Yet, despite being ‘visual’, the aircraft deviated from the optimal 3° gradient that is the Glideslope (GS) prescribed by the Instrument Landing System (ILS; the radio signal that enables avoidance of obstacles on the ground during the final approach). First, the pilots climbed a little above the GS, then descended well below it[ii] (see Fig. 1). At this stage the sound of rain could be heard on the CVR, and the crew were evidently seeing lightning flashes, a sure sign that they were in close proximity to a thunderstorm.

Fig. 1. The CVR transcript with the flight path and ideal glideslope displayed.

Shortly thereafter the aircraft descended well below the GS. The First Officer called out, “You are red on the VASI” (Visual Approach Slope Indicator), suggesting that they could see the runway lights, and knew they were too low.

The tail section of the DC-8. DP collection

The Captain responded with “Max Climb”, but it was too late. The aircraft impacted coconut trees, the tallest of which stood 163 feet above the runway altitude. The aircraft proceeded to strike several other trees in the vicinity and disintegrated as a result of the collisions. A ‘ball of fire’ was observed from the airport control tower.

A contentious process

The final report of the Commission of Inquiry is typically an unemotional document. But reading between the lines of the bland prose, and from anecdotal evidence given by the few remaining people who were involved, this investigation was a contentious affair.

A delegation from Icelandic Airlines was present, and they appear to have been intent on protecting their dead colleagues from damage to their professional reputations. They seem to have insisted that the glideslope (vertical) portion of the ILS was “bent” due to poor maintenance[iii]. Several complaints from other airlines stating that the ILS was “tripping”, is “unreliable”, and the glideslope was “unreliable”, “useless,” “unserviceable”, and “erratic”,[iv] were produced as evidence of culpability on the part of the airport.

The Captains instrument panel recovered from the crash site. DP collection

Justice Supramaniam appears to have gone to great lengths to educate himself on the technical details of the navigation equipment and the instruments on the flight deck of the DC-8–63. Part of the Captain’s instrument panel was recovered and a photograph of it appears in the final report[v].

The Commission were also diligent in their attempts to verify the veracity of the “bent glideslope” claim. Testimony was sought from an ICAO (International Civil Aviation Organization) electrical engineer, Krishna Prasad, who had overseen the installation of the ILS at Katunayake. Mr. Prasad testified that the ILS was in good condition and had been flight-checked (calibrated) eleven months previously.

The newly appointed Executive Chairman of Air Lanka, (the late) Captain S. Rakkitha Wickramanayake, himself an experienced, senior pilot, also testified. He categorically stated that if the approach had been discontinued at the correct altitude, the aircraft should not have impacted a tree as low as 163 feet above the runway. He also stated that if the GS was “bent” and it gave an inappropriate ‘fly down’ command, he as the flying pilot would have “disregard(ed) it”[vi].

Probable cause

The final report stated that the probable cause of the accident was “… the flight crew’s failure to conform to the laid-down approach procedures.”

While fixing the blame squarely on the crew, the report also mentioned, in the last comment of Section XV, “Contributing to the accident was the fact that there was a down-draft of the wind which probably rendered recovery more difficult[vii]…”

Windshear and microbursts

It is important to note that this accident occurred more than 40 years ago, when aviation was still a relatively risky undertaking. The industry has improved its safety rate exponentially since then.

The dangers associated with thunderstorms, though evident, were not fully understood in 1978. It was only when Delta Airlines Flight 191, a Lockheed L-1011 TriStar (the safest aircraft of its time) had a fatal encounter with a thunderstorm in Dallas, Texas in 1985, that the destructive power of a thunderstorm was fully revealed. The L-1011 was fitted with an updated digital FDR which captured a wealth of information, allowing the US National Transportation Safety Board (NTSB) to reconstruct the events prior to the crash with a great degree of fidelity. That accident, which resulted in 134 fatalities, was attributed by the NTSB to an “encounter at low altitude with a microburst-induced severe windshear, from a rapidly developing thunderstorm located on the final approach course[viii].”

A NASA depiction of a microburst above the airport.

Windshear, a rapid change of wind direction and/or velocity is common in the vicinity of thunderstorms. On aircraft without groundspeed (as opposed to ‘airspeed’) indications, it is difficult to recognize and respond to such an event. A ‘microburst’ is defined as ‘a localized column of sinking air or downdraft within a thunderstorm’[ix]. This was a phenomenon that was little understood in 1979 and only came to light as a result of the investigation into the accident of Delta 191 many years later.

Did LL-001 encounter a microburst?

A microburst close to the ground just ahead of an aircraft on approach would cause the airplane to first encounter a headwind that would cause it to climb. If the crew did not recognize what they were experiencing and abandon the approach, they would then encounter a severe downdraft, followed by an increasing tailwind from which it may not be possible to recover in close proximity to the ground. This is exactly what happened to LL001 as seen in the re-created flight path (see Fig 1 above and Fig 2 below).

Fig. 2. Effect of a microburst. Courtesy US NWS

This is easy to discuss on the ground, but in the cockpit of an aircraft, on a dark and stormy night on approach to an unfamiliar airport, such clues are easy to miss.

With the benefit of hindsight it would appear that the crew of Icelandic Airlines Flight LL001 encountered a thunderstorm and a severe microburst while on approach to Katunayake airport at night, causing a loss of altitude sufficient to impact trees in the vicinity of the field.

The aftermath

The findings of the Commission and the publicity surrounding them led to many changes in Sri Lanka. Civil Aviation Regulations were amended to comply with international norms. Airport infrastructure was upgraded, and the Airports Authority was reconstituted as a corporation. The latest in radar and communications technology was installed, and personnel trained to operate it. A new runway was built parallel to the old one in 1987. The picture below shows the new runway with the approach lighting system on. The old runway is now the taxiway to the left. The crash site of LL001 would at the bottom left-hand corner of the picture..

Approach to Runway 22 at Katunayake. DP collection

All these efforts have been quite successful. Since 1978 there has, thankfully, not been a serious accident to a civil transport aircraft in the country. Apart from the unfortunate destruction of many military and civil aircraft during the Eelam conflict, only two major accidents to civil flights have occurred since. An Antonov An-12BK ran out of fuel and crashed in close proximity to the airport in March 2000; and an Ilyushin Il-18 cargo airplane was damaged beyond repair in another landing incident at Katunayake in 2004. Both aircraft were Soviet types operated by expatriate crews.

List of references

[i] Report of the Commission of Inquiry into Icelandic Airlines aircraft TF-FLA Page 1

[ii] Ibid Annex IV Page 43

[iii] Ibid Page 19

[iv] Ibid Page 25

[v] Ibid Annexe XIV Page 77

[vi] Ibid Page 26

[vii] Ibid Section XV Page 33

[viii] NTSB/AAR-86/05

[ix] US National Weather Service definition

I love airplanes. As an airline captain I flew many including the A380 and Boeing 777. But wish I’d had the opportunity to fly some of these old propliners.