Flight and Descent
Iberia flight IB062 departed Málaga, Spain, at 19:30 UTC bound for London-Heathrow Airport, United Kingdom. The weather was slightly misty with intermittent drizzle, but visibility remained reasonable. The aircraft was cleared to descend to flight level (FL) 210 after passing latitude 50°N and was routed via Ibsley and Dunsfold. Following a conflict with other traffic, the crew received a new clearance to FL110 and a heading of 060° toward Dunsfold. As the aircraft passed abeam Fawley, it was further cleared to FL60. The crew acknowledged this instruction, reporting that they were leaving FL145.
Final Moments
Just under four minutes later, air traffic control cleared the flight to proceed direct to Epsom on its own navigation, a call that the crew acknowledged. Throughout this period, the aircraft remained in a continuous descent until it struck trees on the southern slope of Blackdown Hill, approximately 48 km south-southwest of Heathrow Airport. The aircraft continued for hundreds of yards across a meadow, killing 65 grazing sheep. It then crashed through a large hedge; parts of the aircraft detached, destroying a garage and damaging sections of the roof of Upper Blackdown House as the aircraft disintegrated. None of the 37 occupants survived.
Investigation Findings
Accident investigators were unable to identify a reason for the aircraft's continued descent. A possible misreading of the altimeters was examined in detail. The aircraft was equipped with three-pointer altimeters that included warnings indicating when the aircraft was below 10,000 ft. The descent was steady over 13½ minutes, meaning the pointers were in continuous motion, increasing the likelihood of a misreading. The cross-hatching on this type of altimeter first appeared in a window in the 10,000 ft disc at an indicated altitude of 26,666 ft; the edge of the cross-hatching would have been visible within two minutes of the descent's start. At 10,000 ft, the cross-hatching completely filled the window and remained filled while below that altitude. Thus, the cross-hatching was visible for about 9½ minutes before the aircraft passed through FL60.
Investigators noted that with such altimeters, an indication of 6,000 ft could easily be misread as 16,000 ft if the position of the 10,000 ft pointer was not carefully noted. However, the crew's report to ATC of passing FL145 suggests that at that moment they knew they were below 16,000 ft, indicating no misreading down to that level. Yet that does not rule out the possibility that the crew later suffered a mental loss of sequence and transposed themselves to an altitude above 16,000 ft—a phenomenon known to have occurred before. Nevertheless, the investigators concluded that no evidence showed this happened on this occasion. The accident was due to the aircraft continuing to descend through its assigned flight level to the ground, with no reason established for the continued descent.