Turbulance

[t-bird]

Well done FF. We need more pilots like you . Precautionary landings is part of our training and is often a safe alternative but never used maybe because of the pilots ego

[ACE]

Agreed with the last two posts, well done and thanks FairyF. Was your passenger on a training/intro flight and how was he afterwards ??

Something that I did notice in your report-back was that you observed, and remembered, the conditions back at the lagoon. That reminds me of an instructor telling me to always keep a spot available for any emergency. Basically navigate from one open space to another.

This is where we all learn from some of the more serious exchanges of info/experiences on a forum such as ours.

Regards.

[Fairy Flycatcher]

Thanks guys. I was a bit worried when I made my post that it would be too much detail, but often your emotions and thoughts plays a bigger part in the outcome than the actual events. I must admit my ego almost DID get in the way

The passenger was a spin-off from the marriage proposal. He saw the figure 8's over the beach and simply followed the sign boards. I often do flights for people without charging, I just love sharing the experience.

He was seriously rattled, but thankful. I explained my decision to him before, explained what PAN PAN PAN means, and who I contacted. I think because I appeared in control of the situation he took it rather well. He fully agreed with me that it was the right decision, especially when the helicopter was thrown around in the turbulence above us!

What upset me though, was that I called a precautionary landing, then radio'd that the landing was successful, with no damage or injuries, yet the helicopter which went to La Mercy just told David that he must please come, there is a microlight that went down near Zimbali. So the man's family were in tears when we landed back with the helicopter. This was seriously unnecessary trauma.

[Fairy Flycatcher]

I must thank the instructor and student in the R44, who came to our help. They really went out of their way, and were most helpfull. Thanks to all the pilots who go out of their way for other people. I have heard of so many lately...

[kb]

That reminds me of an instructor telling me to always keep a spot available for any emergency. Basically navigate from one open space to another.

Regards.

ACE, this is the way I do fly. When crossing the forrests between Greytown and Ballito, I k@k myself, cause it's just forrest. I always try and fly, with my left eye on the ground below, looking for a LZ. Also, worth keeping an idea on which direction the ground wind is blowing.

[lamercyfly]

I promised that I would ask my skygod Johan Anderson about the weather phenomenon on Friday. I asked FF to give him all the details and here is his reply

Hey Annie!

Wow! Wat n ondervinding moes dit nie gewees het nie! Ek is so bly jy is OK
en het ongedeurt deer dit gekom - iemand anders was nie so
gelukkig nie en ek is jammer om dit te hoor... Des te meer van goeie
besluitneming en piloting skill...

Dit is n traumatiese ervaring. Soos verwag kan word bevraagteken jy baie
dinge. Vir party mense is dit selfs genoeg om op te hou vlieg. Een van die
dinge wat die lewe my geleer het is dat blaam plaas niks help nie. Moenie
dat enige iemand vir jou se jy is n sussie nie. Daar is nie so ding soss n
sussie in vlieg nie - die weer is groter as enigeiemand! Ervarings is
relatief - wat aanvaarbaar is vir een is angswekend vir iemand anders. Jou
ondervinding is akuraat relatief tot jou ervaring van die gebeurtenis. As jy
se dit was erg dan was dit erg! En soos dit vir my klink was dit ook so! Net
iemand met die ondervinding soos David sal dan terug wil vlieg maar ek dink
ook dat die ergste al verby was teen daai tyd.

Wat gebeur het? Ek was nie daar nie en weet ook nie wat die
weersomstandighede regtig was nie. Soos wat ek kon aflei dink ek dit kan
dalk a) sterk berg wind invloed gewees het b) wave rotor gewees het of c) n
kombinasie van bergwind (Pre-frontal offshore) en wave rotor gewees het. My
suspiesie se vir my dit was c gewees. Kom ek probeer verduidelik hoekom.

Daar is altyd sterk Wes na NoordWestelikke winde wat elke koue front voor
uit gaan. Die winde is gewoonlik baie hoog en het gewoonlik nooit n direkte
invloed op die oppervalk nie. Die winde manivisteur hulle self in die form
van "bergwinde" - sterk, droe en warm winde wat van die binneland af waai.
Gewoonlik teen die tyd wat dit by die kus aan kom (Spesifiek die Natalse
kuslyn) met die gapaartgaande topografie - die kus lyn is redelik beskermd
as gevolg van die relatiewe hoe land massas tot teen aan die kus lyn -
beweeg die winde skadeloos bo oor die kus gebiede. Hulle het wel n indirekte
invloed. Hoe temperature en n skerp daling van druk op die kus. (Dit is die
skerp daling van druk wat die kus laagdruk sy oorsprong gee.) Verder en
gewoonlik baie hoer is daar gewoonlik ook wave aksie. Die kom voor veral
wanneer die bo-lug omstandighede gunstig is vir wave forming en wanneer
kondisies erg gunstig is kan die wave effek oor baie hoe hoogtes (en
laagtes) manifisteur. (Nogal n ding vir my om die in afrikaans te
verduidelik! Wanneer die atmosferiese kondiesies so is dan kan die wind
af gedeelte van n golf tot teen aan die grond kom - selfs al is die golf
wolke (lenticulars) op 15000ft of hoer. (Waar is die koppelteken!?
Elkgeval, omdat die golf dinamika baie dinamies is (dit is nooit n stabiele
sisteem nie maar verander die heeltyd - golwe kom in sinkronisasie dan met n
hoe amplitude en dan weer laag - soos iets wat asem haal. In die regte
omstandighede kan die afvaartse golf wind presies die effek he wat jy deur
gegaan het. Die "down wash" van die golf kon die onstabiele lug (wat n
karakter is van die bergwind laag van wind) van die bergwind gekombineer om
laer te daal. Die wind word letterlik saam gepers - soos in n venturi en
beinvloed die laer vlakke dan met mening! Soos in jou geval. Sodra die golf
lengte verander verdwyn die "down wash" van die golf en dinge word weer
kalmer - onverklaar baar! (Tensy jy van meer van golf dinamieka weet

Dit is eintlik maklik om die phenomena te voorspel maar jy het die regte
informasie nodig. Jy het n upper air sounding nodig en so ver ek weet stuur
Dbn nie meer die goed in die lug in nie - al hulle informasie word op modele
voorspelings gebaseur en eks bevrees die informasie wat jy nodig het om die
katestrofe te voorspel kan jy nie van die modelle afkry nie. Jy moet op
datum wees van eintlikke wind sterkte en temperature (is dit stabiel met n
isotermiese laag en veral die diepte van die laag...) Dinge wat die Dbn se
weerkantoor tien teen een eintlik nie n benul van sal he nie (Tensy een van
hulle n sweef entoesias is!) Dit is nou die regte tyd van die jaar vir die
soort van ding - die sweeftuig klubs doen hulle berg kampe spesifiek om die
'lee' golf van die Drakensberg te vlieg. Die sweef tuig pilots sal weet
wanneer die kondisies reg is vir groot en diep wave aksie. Dalk kan julle
iemand bel en hoor hoe
sterk is die komende front en wat se golf aksie om te verwag en dan op jul
hoede wees vir iets soortgelyl. Ten minste kan julle studente belet om ver
te vlieg of selfs te vlieg wanneer die weer soortgelyk is - ie as daar n
diep stabiele laag in die bolug is voor die front (of kuslaag) kom met baie
sterk bolug winde. Daar is van
die sweef tuig manne wat baie akkurate voorspellings maak vir dit. (Jy sal
nie die soort
ding in die somer kry nie.)

Ek dink ook die Dbn weer kantoor weet dat al is daar sterk NW of W winde op
hoogte die omtrent nooit die oppervlak area affekteur waar julle langs die
kus vlieg nie - dus hoekom daar geen waarskuwing was vir die coastal traffic
nie. (Ek wonder of daar n waarskuwing was van CAT's vir die groot vliegtuie
van Jhb or elders en op watter vlak?) Miskien kan jy dit opcheck.

Wanneer jy bewus is van die soort moontlikheid sou jy dalk die tekens reg
geidentiviseur het. Toe jy hoog geklim het en omtrent nie kon penetreur nie
moes
die waarskuwings tekens erg afgegaan het. Plus die feit dat die
turbulent laag besig was om te daal - en die cherrie op die koek - die hoe
vlak lenticular! As die soort wolke in die lug verskyn dan vlieg ek altyd
met my sesde sintuig op hoogs gereedheid! Golf invloed kan enigetyd
gebeur en is baie onvoorspelbaar - as die golwe sterk lyk dan bly ek eerder
op die grond...

Annie, ek hoop die verduideliking help. Dalk kan jy bietjie na die rekkords
van die weer kantoor kyk en sien of my verduidelikking sin maak. Soos ek se
ek was nie daar nie maar ek is redelike seker dit is n goeie senario wat
verbasend gereeld gebeur (veral in winter!
Dit is voorspelbaar of ten minste die kondisies wat goed is vir so iets is
voorspelbaar en dit mag dalk n goeie ding wees om op die hoed vir dit te
wees en dan studente uit die lug te hou of naby te hou ten minste.

Weer eens is ek bly jy is OK. As ek een ding kan byvoeg oor wat jou
instrukteur gese het is dit die:" What ever happens fly the glider first AND
never, ever give up."

Sterkte en baie liefde

Johan

[DarkHelmet]

WOW - Thank Johan for that - MOST informative... I was told "If you see lenticulars walk to the clubhouse and make coffee... DON'T GO UP!"

Now, thanks to Johan's excellent explanation (although topographically local to your area) I have a better understanding!

[ACE]

DH, I was wondering if you might be able to give a translation for me and hopefully others, who like me, don't have a good enough command of the taal. There's some incredibly good feedback there .. asseblief boet..

[Wart]

This confirms my observations at Cato on Friday: the pressure dropped below 1000!!!

[Pepper]

This confirms my observations at Cato on Friday: the pressure dropped below 1000!!!

If the QNH is low, don't go

[Robin Hood]

Wow! This is great info from Johan!! My question: can someone please give me a simple explanation of lenticular?

That entire message (plus the lesson learned from the poor student who possibly died because of this particular weather condition) should be surely be included in our training?

[IFLYHI]

I cant remember was "Meteorological conditions" a big part of our training

Or was it just tales told by our instructors while we waited for the right conditions to start our "actual" training

In fact Ex 1 should be : "The air that affect your flying world" and if you don't pass this strenuous test no taking off from the ground

[Morph]

(Hi all, I have translated Johan's message to the best of my ability. Some of the terminology might be out - Morpheus)

Hey Annie!

Wow! What an experience that must have been? I am happy you are OK and survived the experience un-injured although I understand someone else was not so lucky and I am sorry to hear about the accident. Your survival is attributed to your good decision making skills and piloting skill.

This was a traumatic experience. As expected you start questioning many things. For some the experience is enough to give up flying. One of the things I learned in my life is trying to place blame never helps. Also, don’t allow others to call you a sissie as the weather is greater than us all!. Experiences are relative. i.e. what is acceptable to one is horrific to another. Your experience is accurate relative to how you experienced the event. If you say it was terrible, then it was, and it sounds to me that this was indeed the case. Only someone with enough experience like David will consider flying back, but I think the worst was over by that time.

What happened? I wasn’t there and also have no idea of what the weather conditions were at the time. But from what I can deduce it was either a) influences from strong berg winds, b) wave rotor or c) a combination of a berg-wind(Pre-frontal offshore) and wave rotor.

I suspect that it was c). I’ll attempt to explain why.

A frontal system is always preceded by strong Westerly to North Westerly winds. These winds are very high and thus usually have very little influence on the surface. The winds manifest themselves in the form of strong “berg-winds” – strong, dry warm winds that blow from the interior outwards. Usually, by the time they reach the coast and in particular the Natal coastline with it’s particular topography (the coast line is reasonably well protected as a result of the relative high land masses close to the coast) the winds blow harmlessly over the top of these areas. Add high temperatures and a sharp drop in pressure along the coast. (it’s this sharp drop in pressure that brings about the origin of the coastal low). Additionally and at a much higher altitude there will be wave activity. This occurs in particular when the right conditions exist for the forming of waves and in the case of absolutely critically perfect conditions the wave can attain very high and low altitudes. With these atmospheric conditions the down draught can extend all the way to ground level even if the wave clouds (lenticulars) are at 15000ft or higher.

Due to the fact that wave activity is very dynamic (it is never a stable system, varying continuously) multiple waves synchronise producing a very high and low amplitude.

In the right conditions the down draught will have the precise effect that you experienced. The down draught of the wave combined with the unstable air of the berg-wind will create a deeper low. As a result the air is literally compressed, as in a venturi that results in a faster down-draught. As in your case, as soon as the individual waves lengthen again, and go out of synch with each other the conditions suddenly and inexplicably get better.

It is relatively easy to predict this phenomenon but you must have access to the right information. You need an upper-air sounding but as far as I am aware Durban is not doing this anymore, they are basing their information on prediction-models (not sure about this term – Morph) and I am afraid that you cannot get the information needed to predict this catastrophe from these models. You must be intimately aware of current wind strengths and temperatures (is it stable with an isothermic layer and in particular how deep is this layer) Things that the Durban weather office will probably have no concept of, unless of course one of them is an enthusiastic hang-glider. It is now the right time of year for these things to manifest themselves. Hang gliding clubs specifically do their mountain camps in order to fly on the ‘lee’ waves of the Drakensberg (I’m not sure he means lee as in downwind, or lee as in Afrikaans for low-Morph). These glider pilots will know when the conditions are right this large and deep wave activity.

Perhaps you could call someone to determine the strength of an approaching front as well as the expected wave activity and use this to be more cautious in these circumstances. At a minimum you should limit the distances the students fly or even prevent them from flying completely when the conditions present themselves, i.e. is there is a deep stable low ahead of a front (or coastal low) with very strong high level winds. There are some glider pilots who are very good at making accurate predictions and perhaps these are the guys you should call.

I also think the DBN weather office knows that even though there are very strong W or NW winds at high altitudes, these normally never effect the surface where you guys fly so as a result no warnings were issued to coastal traffic.

Once you are aware of the possibility of this happening you would have correctly identified the signs. When you were trying to climb and just couldn’t penetrate the warnings bells should have been ringing. Added to this the turbulent layer was dropping and the cherry on the cake, a high level lenticular cloud. When these clouds are visible I fly with my sixth sense on high alert! . Wave activity can occur at any time and is unpredictable, if the waves are strong, stay on the ground.

Annie, I hope this explanation helps. Perhaps you can check up on the records at the weather office and see if this makes sense. I was not there but I am reasonably certain that this is the scenario that occurs at surprising regularity(particularly in winter)

Lastly, I am glad you are OK and as My instructor always said, “What ever happens fly the glider first AND never, ever give up."
Johan

[DarkHelmet]

TG I read an entire post before I commit! Thanks morpheus! I just walked in from some hard work (always feel guilty after a morning flight and then work EXTRA hard the day!)

[Griffin]

I think the Morph has just changed his name to Babel fish.

Johan Anderson is probably one of SA's top hangglider pilots and is also an excellent mocrolight pilots and teacher. There was a video made of him, flying a hang glider, and a chap flying a paraglider. The two of them did a trip together and there some incrediably flying sequences. Not sure if it ever made it to DVD.