A KLM Lockheed L-049 Constellation airliner (named Nijmegen and registered PH-TEN) crashed into high ground near Glasgow Prestwick Airport, Scotland, on 20 October 1948; all 40 aboard died. A subsequent inquiry found that the accident was likely caused by the crew's reliance on a combination of erroneous charts and incomplete weather forecasts, causing the crew to become distracted and disoriented in the inclement conditions.

The flight

Events prior to approach

The aircraft was piloted by Koene Dirk Parmentier, one of the winners of the MacRobertson Air Race, widely regarded as one of the great flyers of the era, and KLM's chief pilot. The co-pilot on the flight was Irish citizen Kevin Joseph O'Brien.

Nijmegen was scheduled to fly from its home base at Schiphol Airport near Amsterdam at 8:00 p.m. CET to New York via Prestwick, with Shannon Airport in Ireland as the alternative stopover point in case of bad weather at Prestwick. The aircraft carried sufficient fuel to divert to Shannon and then back to Schiphol, if necessary. The plane's departure was delayed as additional cargo was loaded for transport to Iceland, which would be an additional stop en route from Prestwick to New York.

The plane eventually left Schiphol at 9:11 p.m., crossed the English coast at Flamborough Head, eventually heading NW at 2320, when it turned almost due South approximately 15 miles ESE of Kilmarnock. The aircraft eventually started its run in towards runway 32 (Prestwick's longest runway and, at the time, its only runway that offered a ground-controlled approach, at 2325 at 1500'.

The weather forecast Parmentier had been given by the Royal Dutch Meteorological Institute at Schiphol had told him that there was some slight cloud at Prestwick, but that it would likely dissipate by the time the Nijmegen arrived. This report was incorrect; the weather at Prestwick was steadily deteriorating, Prestwick had a second, alternative, runway (Runway 26) which was heading into the wind but had no radar-approach system. However, KLM pilot guidelines, drafted by Parmentier himself, forbade a landing at Prestwick in low cloud on the alternative runway. No new forecasts, which would have told Parmentier of the expected decreased ceiling were broadcast. Nor did he know that already that evening two airliners from SAS had turned back rather than attempt a landing at Prestwick.

Inland of the runway was high ground of over , Three miles <!-- nautical or statute? --> (5&nbsp;km) to the north-east of the runway, rising to over , were a set of wireless masts. inland ran a series of electricity pylons and high-tension cables, the main national grid line for South Scotland, carrying 132,000&nbsp;volts. However, the error-riddled charts issued by KLM did not have these marked and gave a spot height close by of 45'. Instead, he decided to attempt an overshoot of the main runway guided by the ground radar controller, followed by a left-hand turn that would bring the plane downwind of the alternative runway. He would then overfly the runway before looping round for his final approach. However, three miles out Parmentier decided that the wind was probably too strong for landing on the main runway and decided to overshoot and land on the alternate. He overflew Runway 26, the lights of which he could now see, climbed to a height of and extended the landing gear ready for landing. At this point they ran into what Parmentier believed was an isolated patch of cloud. However, this was the actual cloud-base, which was now as low as in some areas. at about 23:32 UTC.

All 30 passengers (22 Dutch, 6 German, 1 British and 1 Irish

Court of enquiry

The subsequent court of enquiry blamed several factors for the crash:

  • The failure of the ground authorities to inform the Nijmegen of the deterioration in the weather.
  • The failure of the crew to time their flight downwind of the runway.
  • The errors in the official KLM approach chart the crew had relied on. It emerged during the enquiry that these charts had been copied from war-era United States Air Force charts, which upon subsequent examination were also found to be faulty. The court of enquiry was astonished to find that KLM had relied on maps from a foreign authority when detailed and correct maps were available from the Ordnance Survey, the United Kingdom's national mapping authority.

The enquiry determined the probable cause for the accident was:

  1. That when the pilot started his landing manoeuvre for runway 26 of Prestwick Airport the weather conditions were already below the limits for this manoeuvre but that from the weather forecasts received this could not be known to him and that this could not be personally judged at the time.
  2. That, although the landing on runway 26 under the weather conditions, as far as these were known to the pilot, required the greatest caution, the pilot could not be blamed for having commenced that landing procedure.
  3. That flying too long on the downwind-leg of runway 26 caused the accident.
  4. That, if no unknown circumstances contributed to the extension of the flight on the downwind-leg of runway 26, the extension was due to the delayed action of the pilot after he lost visual approach.
  5. That it was not impossible that a stronger wind that the pilot accounted for contributed to the extension of the flight on the downwind-leg of runway 26.
  6. That the possibility of other circumstances as mentioned under 4 could not be ruled out, but that no data was available which could give cause for the supposition that they contributed to the extension of the flight at a low altitude on the downwind-leg of runway 26.

Notable fatalities

  • Bert Sas, Dutch diplomat, former military attaché to Berlin who warned the Allies in October 1939 about German plans to invade France and the Low Countries.

See also

  • List of accidents and incidents involving commercial aircraft

References