Wind and turbulence

OK, let’s first think about when a controller should use visual separation. ATC need to consider the following points before separating departing aircraft by visual means. Aircraft performance, wake turbulence, closure rate, routes of flight and known weather conditions. If successive departure routes or aircraft performance prevent the pilot from maintaining adequate separation then don’t apply visual separation of aircraft.

Now we need to consider a number of other factors – it must be day, the air-traffic controller must have both aircraft in sight and must be in radio contact with at least one of them. The flight crew of the trailing aircraft must have the lead aircraft in sight and be informed of the lead aircraft’s position, its direction of flight and its crew’s intentions. The pilots of the trailing aircraft must acknowledge sighting the lead aircraft and they will then be instructed to maintain visual separation.

It’s important for the pilots of the trailing aircraft to remember that the tower controller will not provide visual separation between aircraft when wake turbulence separation is required. In controlled airspace with ATC radar coverage, the controller must inform the pilot of converging aircraft and VFR traffic. In cruise, when IFR and VFR aircraft are sometimes separated by as little as 500 ft, pilots must use appropriate avoidance procedures.

Of course, the problem with wake turbulence is that it is nearly always invisible, so pilots need to anticipate where it might be. Remember, the weather is going to affect wake turbulence. If it’s still, then there is more chance of wake turbulence occurring.

Finally, remember your role. As air-traffic controllers you need to issue ‘Caution – wake4 turbulence’ warnings only. You are not responsible for anticipating the existence or effect of the condition.

TEXT 15 (2.05 – Track 15)

ICING

The most severe icing encounter I’ve ever experienced happened once when I was doing mountain flying in a Dash 8-200 model. It was -8°. This is the magic temperature. We started picking up super cooled large droplets at FL220. Within that first minute we had accumulated so much ice we had lost 15 kn. I could barely see out my left window at the boots and propeller.

In my experience, if you lose your windshield in the dash, it shows the ice is getting behind the de-ice equipment. I had the ice systems set at maximum and I lost my windshield completely. The airframe was vibrating and shaking violently and I knew we couldn’t climb out of it in time. We requested lower and when ATC cleared us I dropped the props to 1,200 rpm, switched off the autopilot and dove down at 4,000 ft per minute.

We finally broke out of IMC at 11,000 and ATC wanted us to contact the airport in sight, but I told them we needed to fly for a bit and get lower to melt all the ice as I couldn’t see out my window to land.

So, before we move on, have any of you had an icing experience?

TEXT 16 (2.08 – Track 16)

STORMS

I = interviewer, P = pilot

I	What’s like to fly through a storm?
P	Actually flying into a storm is pretty nasty for the passengers and can be pretty scary for us. Flying in stormy conditions is always a challenge, but when you get active storm clouds at high altitudes, when there’s uplift and moisture in the clouds, it’s really tough.
I	If you can’t fly through them, do you fly around them?
P	Yeah, wherever possible. Flying through storms does happen, but I think most pilots would agree that it is pretty unusual to take an aircraft straight into a storm cell.
I	What do you do when you’re faced with storms?
P	If there is a line of storm clouds to fly through, you usually go for a gap in the line. We have a radar on board which senses water droplets, so we can see storm activity up ahead and plan for it. When visibility is poor, or you are flying at night, the radar is especially important. The problem is, the radar only senses water droplets. It can’t see turbulence, so even if you fly around a storm, it could still be a bumpy ride.
I	We know weather causes a lot of delays for airlines. Are storms particularly disruptive?
P	Yeah, weather is usually in the top three reasons for delay. I once had to circumnavigate a large area of showers over the western Pacific which was almost 300 nm out of the way. Definitely the longest diversion I ever had to make.

TEXT 17 (2.14 – Track 17)

BAD WEATHER

Good morning. We’ve already looked at delays due to technical difficulties but today we’re going to focus on the weather. Bad weather causes far more delays than any other factor.

Commercial aircraft have a lot of restrictions and rules about operating in the vicinity of bad weather. Aircraft can’t take off unless the visibility at the destination airport is forecast to be at or above certain distance. Usually half a mile. Airlines take great care when bad weather is reported, because they want to prevent passenger injury. Two thirds of turbulence-related accidents occur at or above 30,000 ft. In fact 46% of all passenger injuries in flight are due to turbulence. This leaves airlines with little choice but to delay when bad weather turbulence approaches.

Although people think of the winter as being connected with bad weather it is usually spring and summer months which are the worst for bad weather delays. These month carry hot humid air, which produces dangerous thunderstorms, severe lightning and turbulence. In fact thunderstorms can contain just about every nasty aspect in one package.

The airport an aircraft is waiting to depart from might have perfect flying conditions but if the destination airport or the route has bad weather you may well have to delay the aircraft. During departure, you route the aircraft to a specific navigation point, the ‘departure fix’. If thunderstorms or other bad weather are lingering around this fix location, or elsewhere along the route of flight, or even at the destination, then you have to prevent departures to the affected area.

TEXT 18 (2.17 – Track 18)

Дата добавления: 2015-11-14