Mast Collapse
Emley Moor has been used as a transmission site since the earliest days of TV transmission. The first permanent transmitter to be built there was an ITV transmitter, covering much of the North. It used a 135 metre lattice tower, which provided only limited coverage. The performance of the site was improved in 1966, in anticipation of colour PAL transmissions, when a 385 metre guy-supported tubular mast was erected, constructed from curved steel segments to form a 2.75-metre (9 ft) diameter tube, 275 metres (902 ft) long. This was surmounted by a lattice section 107 metres tall and a capping cylinder, bringing the total height to 386 metres (1,266 ft). At the time of its construction, it was one of the tallest standing structures in the world. It was designed by BICC and manufactured by EMI.
The cylindrical steel mast regularly became coated in ice during the winter months, and ice also formed in large icicles on the guy wires, placing them under considerably greater strain. The guy wires passed over several small roads, and thawing ice caused a falling icicle hazard. For this reason, red warning lights were placed on the tower for use in times of falling ice, with notices posted on the roads near the guy wire crossings.
On 19 March 1969, a combination of strong winds and the weight of ice that had formed around the top of the mast and on the guy wires brought the structure down. The Duty Engineer wrote the following in the station's log book, demonstrating that this failure of the structure was completely unexpected:
- Day: Lee, Caffell, Vander Byl
- Ice hazard - Packed ice beginning to fall from mast & stays. Roads close to station temporarily closed by Councils. Please notify councils when roads are safe (!)
- Pye monitor - no frame lock - V10 replaced (low ins). Monitor overheating due to fan choked up with dust- cleaned out, motor lubricated and fan blades reset.
- Evening :- Glendenning, Bottom, Redgrove
- 1,265 ft (386 m) Mast :- Fell down across Jagger Lane (corner of Common Lane) at 17:01:45. Police, I.T.A. HQ, R.O., etc., all notified.
- Mast Power Isolator :- Fuses removed & isolator locked in the "OFF" position. All isolators in basement feeding mast stump also switched off. Dehydrators & TXs switched off.
The collapse left sections of twisted mast strewn across the surroundings of the transmitter site and across several small local roads. Although one of the falling stay cables cut through a local church and wreckage was scattered all over the transmitter site, no one was injured in the collapse. The collapse completely disabled the BBC2 UHF transmitter and the ITV VHF transmitter, leaving several million people without service. BBC1 VHF Television transmissions continued from the nearby Holme Moss transmitter. The ITA owned a collapsible emergency mast, 61 metres tall, and it was quickly moved to Emley from the ITA transmitter at Lichfield so that some service could be restored. ITV signals were restored to 2.5 million viewers within only four days. The BBC provided a mobile mast on an outside broadcast van, which was used to restore a restricted BBC2 colour service within just two days. The ITA bought a larger temporary mast from a Swedish company. A crew of Polish riggers, with Jozef Miciak in charge, were hired and a 204 metre mast was erected in just under 28 days at a cost of £100,000. However, this mast could hold only one set of antennae, so many viewers in outlying areas still could not receive colour programmes. The taller mast was brought into service on 16 April. Some weeks later, the BBC erected a 91 metre mast, improving coverage.
The accumulation of ice was generally believed to have caused the collapse, but a committee of inquiry attributed it to a form of oscillation which occurred at a low but steady wind speed. Modifications were then made to similar masts at Belmont and Winter Hill, including the hanging of 150 tons of steel chains within each structure. None of the modified masts have collapsed.
After a series of temporary masts, erection of the current concrete-built tower began in 1969 with UHF (625-line colour) transmissions commencing on 21 January 1971 with the older VHF (405-line black & white) system coming into operation on 21 April 1971. Local residents did not wish to see another mast on Emley Moor, and so a departure from normal designs was called for. The new structure consists of a curved pillar, 275 metres tall, constructed of reinforced concrete, topped by a 55 metre steel lattice mast which carries the antennae.
A section of the collapsed tower was converted for use as a racing control tower at nearby Huddersfield Sailing Club.
Read more about this topic: Emley Moor Transmitting Station, History
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