Airliner destroyed landing short after holding for a Cb. 100 survivors.
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Micro Burst - Avoidance
Thanks for the info bsevenfour,
I was probably drawing a long bow in describing both Cbs as Micro bursts, but on the other hand from my experience , I'd suggest that in the tropics it's the way to bet. If there's a Cb near the field you can always observe significant wind reversals & down drafts and even though it may not be a genuine micro burst, it is well avoided. I should perhaps have titled the post "avoidance of possible microbursts". I do disagree on there being such a phenomena as an "innocuous Cb".
I was probably drawing a long bow in describing both Cbs as Micro bursts, but on the other hand from my experience , I'd suggest that in the tropics it's the way to bet. If there's a Cb near the field you can always observe significant wind reversals & down drafts and even though it may not be a genuine micro burst, it is well avoided. I should perhaps have titled the post "avoidance of possible microbursts". I do disagree on there being such a phenomena as an "innocuous Cb".
Last edited by Capt. Crosswind; 2nd Aug 2002 at 01:04.
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Just in case there remains confusion about microburst generation, let me state this unequivocally and clearly: A microburst does not need a thunderstorm (cumulonimbus) to form, any low or mid-level convective cloud type can produce a microburst. Hence the previous references to innocuous cumulus (cu), or towering cumulus (tcu). The National Weather Service does not classify thunderstorms into intensities, where confusion may arise is in the reported VIP levels. These levels describe the precipitation intensity within a thunderstorm, not the strength of a thunderstorm. In the western United States, as well as in Australia and Africa, you can get some viciously nasty thunderstorms with high temp/d.p. spreads having very low VIP levels.
It would be a prudent decision to treat all contouring convective cells as being able to generate microbursts and being prepared for such an encounter when your flight path takes you beneath or into such an environment.
It would be a prudent decision to treat all contouring convective cells as being able to generate microbursts and being prepared for such an encounter when your flight path takes you beneath or into such an environment.
Bae146-100 in Africa, summer 1999 recovered from a microburst without injury but had to make an emergency landing with gear up due to branches in the wheel well.
The aircraft had to climb up through trees from less that 50 ft after rapid descent from 800ft.; the severity of the microburst was FAA level 4, similar to DFW. There was a good write up in the BAe safety magazine; it showed that excellent airmanship in following the correct recovery procedure and good CRM do pay off. Also the value of flying an aircraft with high lift, 4-engine thrust, and of very solid construction.
The aircraft had to climb up through trees from less that 50 ft after rapid descent from 800ft.; the severity of the microburst was FAA level 4, similar to DFW. There was a good write up in the BAe safety magazine; it showed that excellent airmanship in following the correct recovery procedure and good CRM do pay off. Also the value of flying an aircraft with high lift, 4-engine thrust, and of very solid construction.
Re 146-100 microburst in Africa (ALF5071H). In addition to the remarkable airmanship and CRM shown in this incident the Captain’s report added some very good advice about this type of encounter.
The cloud was a small cumulus on the approach, rain was falling sufficient to obscure the airfield. There were no indications or warnings such that the Captain should have delayed the approach, “it was a nice day in East Africa”. The first unusual indication was the intensity of the rainfall as the aircraft flew into it. The noise of the rain increased to a previously unheard level, and then the aircraft fell out of the sky.
Recovery was flown with full power, attempting to maintain stick shake speed and pitch attitude. The aircraft general attitude was very low in the microburst. The down draught gave a 12 degree flight path, thus the resulting pitch attitude (Vss angle of attack in the relative airflow) was much less than that which would be seen during practice stalls. The pitch control (trim forces) and the pitch attitude continuously changed due to the turbulence.
The crew did manage to recover at very low altitude, probably as the aircraft just exited the core of the down draught. Tree damage resulted in a nose gear stuck up, one main gear without indication, and a double hydraulic failure!
The cloud was a small cumulus on the approach, rain was falling sufficient to obscure the airfield. There were no indications or warnings such that the Captain should have delayed the approach, “it was a nice day in East Africa”. The first unusual indication was the intensity of the rainfall as the aircraft flew into it. The noise of the rain increased to a previously unheard level, and then the aircraft fell out of the sky.
Recovery was flown with full power, attempting to maintain stick shake speed and pitch attitude. The aircraft general attitude was very low in the microburst. The down draught gave a 12 degree flight path, thus the resulting pitch attitude (Vss angle of attack in the relative airflow) was much less than that which would be seen during practice stalls. The pitch control (trim forces) and the pitch attitude continuously changed due to the turbulence.
The crew did manage to recover at very low altitude, probably as the aircraft just exited the core of the down draught. Tree damage resulted in a nose gear stuck up, one main gear without indication, and a double hydraulic failure!
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Full report at http://www.fly-safely.org/story.asp?id=32
Lesson learnt...... use a 146 for tree pruning, not an A320
Lesson learnt...... use a 146 for tree pruning, not an A320
I mistakenly overlooked this topic all summer long.
%MAC: yep, in the past we could add about 1/2 the steady wind+gust factor (but no more than 20 knots)? Anyway, few pilots now are comfortable with adding only 5 knots extra to the normal approach speed(s), but none of us add more than about 10-15 knots. This is during very gusty winds and with a long runway ahead.
717: a clever guy at a former maint. hangar (ATL) developed some window "cushions", each of which fits a specific windshield and block out the sun very well. Makes a big difference, not to mention being sure that nobody switches on the ram air before they leave the plane, in order to add a little bit of airflow-but it comes from a very hot tailcone! Guys still do it, now and then, in 80-95* weather!
%MAC: yep, in the past we could add about 1/2 the steady wind+gust factor (but no more than 20 knots)? Anyway, few pilots now are comfortable with adding only 5 knots extra to the normal approach speed(s), but none of us add more than about 10-15 knots. This is during very gusty winds and with a long runway ahead.
717: a clever guy at a former maint. hangar (ATL) developed some window "cushions", each of which fits a specific windshield and block out the sun very well. Makes a big difference, not to mention being sure that nobody switches on the ram air before they leave the plane, in order to add a little bit of airflow-but it comes from a very hot tailcone! Guys still do it, now and then, in 80-95* weather!
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APFDS, during the severe windshear envisaged in this post, your FBW ground speed mini is not sufficient for "so that the pilot can fly the aircraft normally" Perhaps you and others who refer to Reference Ground Speed were thinking of more managable shears. A common downburst from a decaying CB could result in windshear in the region of 80 knots plus. So if your IAS drops 80K on late final in the landing configuration, and at the same time your sink rate increases from 600fpm to 3000+fpm, TOGA & alpha floor are insufficient for survival.
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I'll back up Slasher's post here as well. The ONLY time I have encountered a microburst, I was on the ground (thank God!). I currently live about 20 klicks south of MNL. I have always been curious why the CB bases here are so much lower than in the states (Ohio)-have to assume it's a closer range of dew point/temp here (stand to be corrected).
Anyway, it was june and the southwest monsoon season with convective activity moving in from the west. At first, I thought it was just a prefrontal gust-except it never stopped. Shortly before the lightning commenced, I noticed what was possibly virga and then there was an incredible downward burst of wind. I can't even estimate the rate, but it absolutely FLATTENED a mango orchard! These were mature trees probably 40 feet in height and it looked like a giant had stomped em flat. Roughly a circular 'footprint' about 75-100 feet in diameter.
I've never experienced anything like this before and I grew up in 'tornado alley'-this was just as violent as a tornado, except very localized. I don't see how any aircraft could survive an encounter with this type of phenomenon-avoidance really is the only option.
As to recovery options, etc, I was taught (after DON'T GO THERE!) full throttle, pitch for vx and PRAY! This was similar to the technique taught in my Falcon course as well. That course also taught that you leave the wx radar ON until sure that the final approach and missed approach paths are clear.
Be safe and happy flying all!
Anyway, it was june and the southwest monsoon season with convective activity moving in from the west. At first, I thought it was just a prefrontal gust-except it never stopped. Shortly before the lightning commenced, I noticed what was possibly virga and then there was an incredible downward burst of wind. I can't even estimate the rate, but it absolutely FLATTENED a mango orchard! These were mature trees probably 40 feet in height and it looked like a giant had stomped em flat. Roughly a circular 'footprint' about 75-100 feet in diameter.
I've never experienced anything like this before and I grew up in 'tornado alley'-this was just as violent as a tornado, except very localized. I don't see how any aircraft could survive an encounter with this type of phenomenon-avoidance really is the only option.
As to recovery options, etc, I was taught (after DON'T GO THERE!) full throttle, pitch for vx and PRAY! This was similar to the technique taught in my Falcon course as well. That course also taught that you leave the wx radar ON until sure that the final approach and missed approach paths are clear.
Be safe and happy flying all!
