Deeper Atlantic Lows or Hurricanes?
11.3.08
Donald Burfitt-Dons

In Hertford Hereford or Hampshire hurricanes hardly happen. Eliza Doolittle may have struggled to pronounce her aitches but the song implied that hurricanes are normally associated with the tropics. There the atmosphere has relatively high surface temperatures to draw on to the create conditions for cyclone generation.

No longer. Last week, a tragic accident occurred in the Western Tyrols in Austria. A business man from Liverpool was killed while driving from Salzburg Airport, crushed in his car by a falling rock which had been shaken loose from the mountain above by a hurricane.

Further north a Lufthansa A320 was making its final approach to Hamburg airport in rather unusual conditions to say the least. With the tower reported winds of up to 250 kph (135 knots) the aircraft got hit by a crosswind gust which lifted the into wind wing, causing the downwind wing to scrape the runway surface. Struggling to keep level with ailerons the pilot successfully executed a go around and skilfully retrieved the situation, landing safely on the second approach.

As we have noted before in other articles, modern aircraft are in general limited to a maximum crosswind of 30 knots plus a 5 knot gust allowance. As extreme wind conditions become more common these design limits are being met with increasing frequency. Limits for auto land using triplex autopilots are much lower allowing just 15 knots of crosswind. Aircraft can land in 135 knot winds providing the winds are blowing down the runway although with a final approach airspeed of around 140 knots the aircraft would only be making 5 knots over the ground, or if the wind increased a further 10 knots the hapless crew would find themselves actually flying backwards away from the runway, an unnerving experience quite common in the early days of hurricane data collection. At that time the piston driven aircraft flew at much lower cruising speeds of 140kts and could become stationary or start flying backwards relative to the earth as the crew took their readings approaching the core of the hurricane.

In a 135 knot head wind, a shift of a mere 13 degrees either side of the runway QDM (the magnetic runway direction) the maximum crosswind an aircraft can handle would be exceeded. Judging by the footage of the Lufthansa aircraft’s final approach and go around that is exactly what happened in Hamburg last week.

Both of these incidents were reported as ‘freak accidents’ by the media. In fact there is a common factor in these and many other ‘freak accidents’ which have been occurring on our oceans and airports. As we have repeatedly warned, whether on sea, land or air, we had best prepare ourselves to cope with extreme wind conditions on an ever increasing basis, and be aware that the safety pads which have been built into our ships and aircraft are going to be compromised ever more frequently

The implications are clear. Extreme weather is on the way whether we like it or not.