In this particular incident the ATSB talks about "dry microbursts" I assume a wet microburst would show up on their radar.
Accident: Network Aviation Australia F100 at Nifty on Oct 19th 2012, hard landing
What is the difference between windshear and micobursts ?
There are two type of windshear warning systems. Older aircraft only have reactive systems, whereas the new will generally have both predictive and reactive.
Predictive windshear warnings are based upon the doppler shifts that are seen by the radar. But the radar does not see air...it has to have something to reflect from. So, if there's no water droplets, there's no paint, no doppler, no warning. But, in general the nastiest stuff is associated with rain from thunderstorms, so you will generally get a reaction from such a system if needed. Remember that the aircraft is not in a windshear encounter at this point, its a prediction, so whilst it will result in an abort if it activates during take off, and a go around on approach, it won't immediately push us into the 'in extremis' windshear recovery techniques.
Reactive windshear is based upon what the aircraft is actually encountering. If it goes off, you're already in trouble. The response should always be TOGA, and whatever pitch is necessary to keep the aircraft unstalled and away from the ground. Stick shaker activation is quite possible during this, and you won't change the configuration at all until the warning stops, and it's all back under control.
When shear is predicted, most flight manuals (after suggesting that you really should either go somewhere else, or hold for a while) will recommend that landing be done with less than full flap, and at a higher than normal approach speed. This morning in Melbourne, with the wind at 1,500' around 60 knots, and the wind on the ground 35 knots, we used flap 3 and Vref +10. The aircraft will have less drag, and so will respond better to power increases, but it does tend to give more speed excursions on the high side. There is a greater margin between the approach speed and the stall.
In the incident referenced, the crew initially seem to have done the right thing, with less flap, and more speed, but later took those corrections out. Of course hindsight is a great thing.
A microburst is really an extreme example of windshear. They are very localised, and basically there is a very strong downflow from a storm cloud, that reaches the ground, and moves away from the centre of the cell. An aircraft encountering one will hit the outflow, where it will have rapidly rising airspeed, to which the response will be a very large power reduction. It then gets to the centre with the down flow, and will encounter high sink rates, so lots of power, and then to the far side, where the speed will very rapidly wash off. A US Navy discussion of this, in relation to the extremely powerful F14, stated that power necessary to recover could well exceed the capabilities of that aircraft....so airliners don't stand much chance.
It really wasn't recognised until the DC10 crash in Dallas. I recall flying an emulation of that in the 767 sim, and it was eye opening to say the least.
