Typhoon’s and Flying

Well it’s 10:54 PM here in Hong Kong and I’ve been listening to the wind rattle the windows for most of the evening. The day started out like any other, except we knew there was a typhoon to contend with at some point. There was a level one warning on Saturday night, which we had to consider as we had plan’s for Shawna’s birthday downtown. Intense typhoon’s shut down the inter-island ferries here in Hong Kong, and we were not going to risk being stranded downtown with our two young puppies at home. But after a quick check of the surface analysis charts, and with the typhoon centered more then 500 kilometers away, off to the W hotel we went. But we couldn’t avoid our first typhoon for long.

So after most of the day being nothing more then a windy rainy day, I decided a quick bike ride into town would be doable, but not for long. We needed milk after all. Rolling into town I noticed quickly that virtually everything was shut down. The two local grocery stores and McDonalds were the only businesses that remained open. Everything else, including the ferry to Hong Kong island was closed. Now at level 8, this Typhoon means business.

So back to the house with no milk (sold out). The wind has done nothing but increase for the last few hours, peak gusts reported at 125 kms/hr. Which has resulted in most everything on our roof top being rearranged by the wind, despite my efforts to store everything. The dogs sure don’t like all the noise. They have a hard time peeing on the roof with nothing in its original place and rain coming from all directions. But after four trips to the roof, finally comfortable enough to take care of business.

After a quick search online, it appears most flights are delayed at least an hour, and in some cases much more. Typhoon’s can create several hazards to flying that result in such delays. So I thought it would be appropriate to take a look at them.

Here I am the next morning now, the aftermath of the Typhoon. Last night saw the Typhoon warning increase to level 10, and peak winds reaching 180kms/hr. The airport reported gusts as high as 66 knots. The airport was shut down for several hours last night, with several flights effected for most of today and tomorrow as well. Locally in our village, many trees have blown over, but thankfully, no damage or leaks in our village house.

So back to the point of this post, the hazards to flying. Typhoons typically bring a few major hazards to the pilot faced with flying near them.

One, the wind. With the above mentioned wind speeds, its not hard to imagine that these winds can create conditions outside many aircraft’s operating limits very quickly. Even with a cross wind 30 degrees off the runway, it’s not long before a 60 knot total wind velocity has created a crosswind component out of limits, both landing and taking off. Wind such as what I have attached below also creates wind shear, which is basically large sustained changes in wind direction or speed. This can be both performance enhancing (wind shifting from a tailwind to headwind) or performance degrading (a shift from a headwind to a tailwind). The latter is generally of most concern to us as pilots. Our aircraft here at Cathay Pacific, as well as the Hong Kong International Airport have sophisticated equipment to predict and report wind shear. However, wind comes and goes faster then most weather phenomena and this is where the hazard exists. Sometime we do not get a predictive wind shear warning (that is a wind shear ahead type of warning) and we can be faced with actual wind shear warnings. These situations call for a disregard to all ATC instructions, and even TCAS avoidance measures, and require a prompt, and swift reaction to the wind shear. I find most of the aircraft I have flown, from the Metro, to the 747, we are taught to establish maximum available power, and a maximum nose up attitude (often just below a stall pitch angle) and to leave the aircraft in the configuration it is in until a positive climb is established. That is to say, flaps are not to be retracted until a safe airspeed and climb has been established (flaps of course assisting in lift), while the gear remain down until a climb has been established as well. The idea being that a “bounce” off the ground is better then a scrape (in very general terms here). In most cases with wind shear in a forecast or reported, pilots elect to hold if fuel permits, or simply divert to a nearby airport.

Which brings us to a second hazard. Diverting to an alternate is a regular occurrence in the airline world, however when facing a typhoon, alternates may be up to several hours away. Typical flights into Hong Kong use Macau or Shenzen as alternates. But as this typhoon last night, and virtually all others have adverse weather affecting area for several hundred miles in all directions from the center of these phenomena, finding a suitable alternate can be difficult. The nice thing about this type of weather is that they are well forecasted, so generally hours before a crew even wakes up in Europe to fly to Hong Kong, dispatchers have determined suitable alternates for such a flight. This however will never replace the responsibility the pilot has to double check all he weather information available prior to a flight, and to continue with weather updates while enroute. Fortunately through datalink systems in the 747(and most modern airlines) we are only a few simple key strokes from receiving all the weather we need when in the air. It looks like (via our company web site) that most flights were using Kaohsiung, on the island of Taiwan as an alternate. This is about an hour away, much further then Schenzen and Macau, which are both less then 20 miles from Hong Kong. Flights were also generally given at least 30 minutes additional fuel for potential holding. This of course can be supplemented with a more economical fuel burn through flying slower, as well as f course adding additional fuel if payload permits. My policy is generally you can only have to much fuel if you’re on fire. Pilots in situations like these are generally more comfortable looking at lots fuel in the tanks, more fuel means more options.

The final major hazard to consider is the rain. Rain produces lower visibilities, and damp or wet runways degrade aircraft braking performance. Hydroplaning is also a concern for aircraft if the conditions are right. Certain techniques can help with hydroplaning, but poor braking can rarely be avoided until a runway dries up. The poor visibility as a result of heavy rain is a concern for obvious reasons. However the 747 like most modern airliners can land with very low forward visibility. Rain on a windshield can also produce an optical illusion that we are higher then we actually are, due to the way light refracts through water. This of course can lead to hard landings, but wipers and rain repellent assist with this hazard.

So as I have thought of everything I can regarding typhoons and flying, and now that I have re arranged our roof top patio furniture, I leave you with some pictures of the last 24 hours.

Enjoy, and fly safe, or at least have someone fly safe for you 🙂

Back to Amsterdam Thursday!