Thunder over Hjørring

In April 2020, archaeologists from Vendsyssel Historiske Museum found some fragments of an aeroplane during a preliminary excavation in connection with municipal construction work. The museum did not dig specifically for the aircraft but found a number of fragments that had not been removed after the plane crash in 1959. Several of the fragments had serial numbers indicating that it was an American-built Republic F-84G ‘Thunderjet’ jet fighter. The press coverage revealed a dramatic event that nearly cost civilian lives and ended with the tragic death of the pilot.

By Jens-Christian Hansen

It was a fateful Thursday morning, 26 February 1959, when a drama unfolded in the skies over Hjørring. Two Royal Danish Air Force jet fighters were on a training flight practising dives from a height of six kilometres, which would prove fatal for one of the planes and its pilot, 22-year-old Leif Ardal.

In 1959, Denmark was a ‘frontline state’ during the Cold War. The arms race between the Warsaw Pact and NATO was in full swing, which resulted in extensive deliveries of various jet fighters to the Royal Danish Air Force, especially from the US during the 1950s. One of these aircraft types was the ‘Thunderjet’, the American-built Republic F-84, of which the Royal Danish Air Force received 246 in versions E and G, and also had other aircraft types available for various tasks.  This made the F-84 the Air Force’s most widely used aircraft type ever. In comparison, Denmark has currently ordered a total of 27 Lockheed-Martin F-35s, six of which will be permanently stationed in the US to train Air Force pilots. However, it should be emphasised that the jet fighters of the time were far from technologically advanced and were designed for a different kind of warfare. Furthermore, the aircraft of the time were not nearly as reliable as modern fighter jets, and crashes – including fatal ones – were common in the first decades of the Cold War. For its time, however, the ‘Thunderjet’ was a very modern aircraft, as it could carry tactical nuclear weapons and could be refuelled in the air. The aircraft type was developed from the end of World War II and produced between 1947 and 1953, when the US Air Force used the aircraft during the Korean War, primarily as a fighter-bomber. In total, 7524 aircraft were built in different versions.

The aircraft that roared across the Vendsyssel skies this Thursday morning was a Republic F-84G Thunderjet with the registration letters AT-A. The aircraft, manufactured by Republic Aviation on Long Island, New York, was delivered to the Royal Danish Air Force in August 1956. Prior to this, it had flown for the Belgian Air Force (now Belgian Air Component) between 1952 and 1956. In the first post-war years, many European NATO countries received massive arms aid from the US, which also helped explain the extensive deliveries of military hardware. The aircraft was originally intended to be delivered to 728^th Squadron at Skrydstrup Air Base but was instead assigned to the training flight at Aalborg Air Base, where pilots were retrained and educated.

On this February morning, two aircraft had taken off from Aalborg at 8.30am for a training flight. One was the accident aircraft piloted by Flight Lieutenant Leif Ardal; the other was flown by his instructor. It was Ardal’s second training flight in a Thunderjet. In the beginning of the training flight, the landing gear on the accident aircraft could not be fully retracted, so a manoeuvre was needed for at complete retraction, after which the opportunity was taken to practice an emergency landing procedure. The practice flight continued, and the planes climbed to an altitude of six kilometres to practice dives, so-called ‘speed runs’, where the aircrafts were pushed to their limits and the dive happened at a speed just below the speed of sound. It should be noted that the aircraft type was not designed as a supersonic aircraft. During the dive, the instructor lost sight of the accident aircraft while looking at his instruments, but managed to establish radio contact with Leif Ardal, who was able to reply ‘Roger, but I am…’ before the connection became unclear and contact was lost.

What happened in those seconds over north-eastern Hjørring can primarily be reconstructed through interviews in the press coverage of the time and other sparse sources. In terms of source criticism, it should be noted that the statements from the witnesses to the crash were subjective and not always entirely consistent with each other. However, they can be used to try to reconstruct which way the plane flew over Hjørring. At the same time, it was a very dramatic local event, which the press also sensationalised at the time. Although the Royal Danish Air Force lost many of its fighter planes during this period (on 27 January, a ‘Thunderjet’ crashed during an exercise at the shooting range in Tranum, and it was the eleventh plane to crash in just six months), there had not been similar situations close to the town since the occupation years, when a German Luftwaffe Junkers Ju-88 fighter bomber had to make an emergency landing on 4 November 1942 at the power station on the western edge of Hjørring.

But back to 26 February 1959. On the same day, Vendsyssel Tidende proclaimed that the pilot had made a heroic effort to avoid hitting a built-up area in the north-eastern part of the town, before the plane crashed at 10.08am with a huge bang 150 metres from proprietor Engel’s farm Vester Thirup. Witnesses to the crash agreed that they had seen smoke from the plane before it hit the field, some even claimed to have seen fire and also an explosion in the air, which the Air Force quickly denied. In the final seconds, the aircraft was said to have flown very low over the road Norgesvej and curved over the north-eastern part of the city. The author of the newspaper article indirectly questioned his own claim of the pilot’s heroic efforts by writing that the plane’s manoeuvre could also have been due to a defective tail rudder, although there is no evidence of this in the other sources. Interestingly, the witnesses had many different opinions about which direction the plane was actually coming from. Workers at the railway goods yard believed that it had come from the south-east, which may be explained by the fact that the plane originally came from the north-east and flew over the town in a clockwise curve over the road Norgesvej with Nordre Skole-school (Holmegårdskolen) before crashing south of the Vester Thirup farm with the nose pointing south. In that case, the aircraft flew in a 360-degree curve over Hjørring before crashing. The fact that something was terribly wrong while the plane was in the air was emphasised by the fact that it had already lost several pieces when it flew very low over the Vester Thirup farm just before the crash. Whether the pilot was in control of his fighter plane at all was therefore already the big question in that day’s evening press.

The plane hit the ground with such force that the debris was thrown hundreds of metres away and the explosion could be heard from miles away. The crash therefore attracted many curious locals. The Falck-rescue service responded with an ambulance and extinguishing equipment. Unfortunately, the former was not needed. The police and soldiers from the Skibsby barracks, which was in the immediate vicinity of the accident site, took over surveillance until the military police from Aalborg arrived to secure the area. At this point, the arrival of the military police was already hampered by the many curious locals blocking the access roads.

By that afternoon, the authorities were already clinging to the faint hope that the pilot had managed to eject from the plane using the ejection seat, and a search was launched with another aircraft, while military police dog patrols combed a large area around the crash site.  Already the next day, however, newspapers reported that the pilot’s body had been found the same evening the plane had hit the ground.

And what was the cause of the crash? The instructor who flew the second ‘Thunderjet’ told the press that Leif Ardal had either taken ill or had engine problems. Witnesses also claim to have seen the plane climb slightly shortly before it crashed – this may be part of the explanation of why it was believed that the pilot had attempted to manoeuvre the plane away from the dense urban area. The press also speculated that because of this manoeuvre, the plane had been in a stall, i.e. at an angle of climb where it lost lift.

On Saturday, two days after the crash, the newspaper Vendsyssel Tidende reported that the accident investigation board had found parts of the ‘Thunderjet’s’ canopy (the cockpit glass) near Bjergby, which also explains why witnesses saw the plane coming from the north-east. Therefore, the press speculated that the canopy had been blown off during the flight for unknown reasons, had torn off the pilot’s oxygen mask or had otherwise caused the pilot to lose consciousness. The latter would mean that he would not have been able to manoeuvre the plane at the end, and that the curve over Hjørring was the last seconds of the plane’s uncontrolled flight towards the abyss.

Unfortunately, it was not possible to obtain any accident report in connection with the preparation of this article, but prior to an article on October 29, 2005, the newspaper Nordjyske Stiftstidende had obtained access to the accident report from the Tactical Air Command. The report’s conclusions are largely consistent with the testimonies of civilians on the ground and the instructor in the other ‘Thunderjet’.  The Accident Investigation Board concluded in the report that there had been no fire in the aircraft, so the observed fire could only have occurred when a wing tank caught fire as the aircraft hit the ground at a 90-degree angle. The angle indicates that the machine was in a spin just before it hit the ground. Interestingly, however, the accident investigation board had also concluded that the canopy was missing.

At the same time, the accident investigation board also found that the landing gear had been a few centimetres out again during the crash. This was due to the fact that after practicing the emergency landing procedure, where the landing gear had been lowered again, it had not been checked that it was back in place. Thus, the pilot had not repeated the manoeuvre that solved the problem in the first place. According to the press, the report could not conclude whether the accident was caused by the canopy blowing off for unknown reasons or coming loose during one of the manoeuvres flown during the practice flight, or a defect in the landing gear caused the pilot to lose control of the aircraft. It can be assumed that a landing gear that was not fully retracted under the aircraft could have affected the aircraft’s manoeuvrability, for example during a very fast dive. Whether this would have caused the aircraft to lose some of its parts during the manoeuvre is, however, pure speculation. What ultimately led to the tragic accident in which 22-year-old Flight Lieutenant Leif Ardal lost his life east of Hjørring will probably never be solved.

While the Royal Danish Air Force was using the F-84G, more than 550 pilots flew the ‘Thunderjet’. 39 of them died. The high number of fatalities can be explained by the fact that the jet fighter was still a relatively new aircraft type that was still under development and had great power potential, where pilots were trained to test the limits of the equipment – sometimes with fatal consequences.

Sources:
– Morten Larsen: ”Koldkrigsarkæologi – om den i 1959 nedstyrtede F84G Thunderjet” in: Vendsyssel NU&DA, 2020. pp. 95-103.
– Ole Rossel: Danmarks Jagerfly. Fra Spitfire til F-16. Gyldendal, 2014. pp. 80-113.
– The newpapers Vendsyssel Tidende’s and Nordjyske’s coverage of the accident in 1959, 2005 and 2020.
Thanks to private collectors and experts for kindly providing sources and photos.