Downdraft induced accidents. Busting the myth...

[FLYNOTE]

virga ... sorry not virgin, I mean not virgo ...
Here is the whole truth and nothing but the truth. Makes good reading.

http://en.wikipedia.org/wiki/Microburst

If you are in the vicinity of the cold air resulting from virga in a gyro or microlight , you go down. Very little leeway here. Sometimes all the way , sometimes you lose a couple of 1000 ft as you battle to keep altitude , not quite understanding what is going on !! All Ts and Ps in the green . Rpm as set and yet machine is losing altitude... If you add turbo and still get no joy you naturally edge back on the stick ... en hier kom daai 'behind the power curve ' met groot gejuig en trompetgeskal. Look out for virga and do not fly under dose cloud thingies. I had a really interesting 'sink' resulting from virga in my Beech Baron once. This was near Gabarone on one of our typical hot highveld 'thunder in the air' days.
Full on microburst will and has pushed Boeings into the ground on take off. Cold air caused by virgo need not neccessary result in a fully fledged microburst but it will push you down and I'd rather not hang around to measure the extent of the burst !

Also be very cautious of women you don't know wanting a flip in your gyro ... and be carefull of your cap going through the prop and beware of ... Just joking !! Forget being cautious about all the possible things that can go wrong. It will spoil your flying. Just take note and be aware of as many potential hazzards as possible. It helps one to understand certain situations you could land up in and simply enhances the joy of flying.

[Learjet]

http://www.youtube.com/watch?v=Zx5ZUFnNOQk

This 38 second youtube video sums up the whole story!

[Gyronaut]

Good one Dave

Interesting to note how quickly it happens eh? From the point of running out of ideas to impact is VERY quick!

[Magnifan]

Very interesting video. In any fixed wing aircraft this pilot would have stalled the wing, dropped the nose or a wing and could easily have been killed even from that height, which backs up FO Gyro's comments about Gyro's not stalling. The problem is that Gyro's, being more forgiving, tend to lull pilots into a sense of false security as far as airspeed is concerned. No, you won't stall if you let all your airspeed bleed away, but you won't continue to fly either, so you had best have a bit of altitude in which to recover!

[FO Gyro]

That is an amazing video, demonstrating the dangers of taking off and pitching up rather agressively. Not that this was an engine failure, but, at the first sign of an engine failure, the nose has to be lowered asap, otherwise the the flare capability is reduced to zero such as in this video. This student appears to have panicked a bit with the high nose attitude on take off, and reduced the power suddenly. Up until his vertical landing, was still running under a reduced power setting. He might have attempted to go into some sort of hover mode, not realising that gyro's can't quite do that when at 100ft or so.

For the non-gyro's pilots reading this, I tell my fixed wing colleagues that the approach speed (1.3 x the stall speed), is aimed to provide a safe buffer during the approach and landing to prevent the aircraft stalling. In a gyro, the approach speed is such that it allows you have enough energy and airflow through the rotors to be able to flare. This poor guy got into a situation where he lost all that.

[Hub-Bar]

Interesting thread guys! Yesterday I was driving along the coast between Hangklip and Gordonsbay. There was a howling black southeaster blowing. As the wind came over the mountain tops, downdraughts rushed down the northwestern face to whip spray from the sea way below. I stopped and watched the phenomenon for a while. At times a perfectly round column of air about 50-75m across would hit the water with such force that spray was created all around the circumference of the circle and driven outwards in all compass directions with the circle widening until it dissipated in about 10 sec – even got spray in my face where I was standing 100ft up from the water. The form of the downdraught as it manifested on the water was ever changing crazily, but the bottom line is that it hit the water HARD all the time. Looking up at the mountain tops where the cloud was billowing over and dissipating in the downdraught, serious turbulence was evident, but nothing remotely suggesting the force with which the invisible downdraught hit the water. Food for thought.

I would like to share the following for the sake of interest and to put a smile on your mugs. A couple of years ago when I was a fresh gyro pilot with a 20h on the clock we decided to attend the Vredendal fly-inn flying from Gansbaai. Myself & Theo in my RAF and Nick & Louw in theirs, with all our kit. Plan was : Gansbaai – Fisantekraal via Franschoek, refuel & join up with Louis van Wyk & others then Saldanha and on to Vredendal. As we had to cross the mountain at Franschoek 2 up, I opted to take just 60l of fuel on the first leg as I intended to go bee-line. As we took off Nick asked if we could instead go low level coastwise via Hermanus. I did a quick calc and said it was fine as I had at least an extra 1h endurance in stock. From Hermanus we started climbing to gain altitude for the Franschoek mountain crossing. We had a mild southeasterly tailwind so the climbing was going full throttle – myself & Theo & kit not being light. Abeam Botrivier Nick’s transmissions started breaking down. I could still hear other traffic so concluded his radio was acting up. Next minute he was gone from sight. Made a few circles searching, to no avail. Decided to carry on in the hope that they were now ahead of us. Not nice – funny things come to mind. At Theewaterskloof dam my fuel gauge went to the first amber. I did not expect that! This being my first long x-country after training, I put it down to the characteristics of the gauge which I did not know very well at the time (What DID I know very well at the time??). I checked the flight time against the fuel I put in and relaxed somewhat. Almost across the dam and the next amber lit up! Now I was sitting up! Had I sprung a fuel leak or what? Ok. Plan to land in Franschoek valley at Moreson which I knew of. Closest option unless an emergency. Still gunning to get sufficient altitude over the mountain – not getting quite where I wanted to be. Moments before crossing the mountain saddle - FUEL RED LIGHT! Now I am convinced there was a fuel leak – and started sweating accordingly. Still no sight of Nick. Just over the mountain saddle and severe turbulence and downdraught grabbed me – my first! For 5 sec I thought this is it – no response to the stick – down we go - it flashed through my mind that a control link must have gone with the first klap. Man, it is deep down to Franschoek from there! Got control back eventually and nose down realised what had happened. By now sweat is running into my eyes, mouth like cotton and hands trembling, not to mention the kidney pain caused by adrenalin. Now back to the supposed fuel leak - the red fuel light glared at me and still approx 10 mins to run, locate and land. Where the heck is Nick? Getting very lonely up here now. Landed ok at Moreson and got out on very wobbly legs – no fuel leak – 15l remaining. Phoned Div Visser (ZU-VIS) who kindly brought me some more fuel. Took off for Fisantekraal still shaken up badly. The first links of a chain (then unknown to me) were well in place. Arriving at Fisantekraal I was tense as a snare. Fortunately Theo did not say too much at the time. Needless to say, stressed out as I was, I botched the (high speed) landing so badly, it was touch and go or the gyro turned over. Three times I caught it just before what felt like the point of no return – right then left and right again before I got it under control. As I turned off the runway there was a crowd watching – and filming – including Nick & Louw. There I was – stripped of confidence and shaking – again. As I got out I just heard one guy say : “ Now that is a novel way of landing a gyro..” A cup of coffee from Hannie made me feel somewhat better. After refueling we took off for Saldanha – the 2 RAF’s from Gansbaai, Louis van Wyk and Celliers Burger in their Magnis. Landed & refueled with Johan Froneman in Saldanah & took off for Vredendal. Long stretches of peaceful beach flying restored me somewhat so that I could even enjoy it. Then came Elandsbaai. Approaching the rock sentinel at the point of Elandsbaai, we were low level with a considerable tailwind and groundspeed. Louis was about a mile ahead and I was following him no 2 in the line. Louis disappeared round the kop and I followed blindly. (Later I learned that Nick and Celliers behind me wisely opted to go over instead of round the kop.) Unknown to me, the shoreline curled back sharply on the other side of the kop. As I rounded the kop, I found myself in severe turbulence and downdraught way out over the white crested water which was rising up to me fast. Once again I experienced the loss of stick feeling induced by the downdraught. Got control again 50ft off the water and made haste for the shoreline. Shaking and adrenalin pains all over again! Got out at Vredendal on wobbly legs and it took the rest of the weekend and some help from Bacchus to calm my frayed nerves. The return trip to Gansbaai was uneventful and great fun. Thanks goodness this happened way back in the past and I can tell the tale – the images however is still crystal clear in my mind. Man, those things that the eye can’t see …we must be aware of it.

[Learjet]

Another example of a "downdraft induced" accident. NOT!
Typical behind-the-power-curve take-off and resultant "mush" back to earth

http://www.youtube.com/watch?v=wYsmteyirio

Note:
how the rough grass strip impedes ground-roll speed before take off
the very, very steep take-off angle
pilot elects not to abort immediately (whilst still above runway) but dogmatically tries to climb out whilst flying behind the power curve
further reduction of lift once out of ground effect
no attempt at all to lower the nose and increase airspeed


"Learn all you can from the mistakes of others. You won't have time to make them all yourself."

[Gyronaut]

What I found interesting about this clip is that he had a full 14 seconds (from the time he left the ground to impact) and enough ground clearance to get the nose forward and gain some speed but didn't. Makes me wonder why? Basics - who taught him to fly or was there a mechanical/control problem perhaps?

[ger koff]

Learjet

A similar thing happens with helicopters. It's called overpitching. It's a well known phenomenon, particularly with smaller helicopters. It goes something like this:
1. Helicopter is over MAUW. (1st mistake)
2. Density altitude is quite high.
3. Pilot is not that experianced, particularly with small helicopters

He lifts off into the hover with throttle wide open and only just enough power. He begins the take off and moves off the ground cushion, the machine sinks slightly and scrapes the skids but still has enough momentum to attain translational lift.
The rate of climb is quite low and HE FAILS TO KEEP HIS SPEED UP because he raises the nose too soon. He starts sinking slightly and he raises the collective to compensate. That's the 3rd mistake. The increased collective pitch increases drag on the MR blades which causes them to slow down (low MR warning horn blaring!), the machine starts to descend faster so he raises the collective more! The situation spirals out of control and the machine hits the deck with a rotor RPM of 75%. It has happened so many times I have lost count. The pilot then claims that he experianced a down draught or ran out of power! There must be something wrong with the engine, maybe icing!
It seems that a very similar thing is happening with gyros too. If you fail to keep your airspeed up you can get into a very similar situation. By pulling the stick back (in a gyro) you are effectively increasing the collective pitch and the rotor drag which will require an increase in power (if it's available). It has a striking resemblance to over pitching.

[Learjet]

Hi ger koff. welcome to the forum and thanks for your informative first post. looking forward to many more

[Gyronaut]

Spot-on Ger. Exactly the same situation in light helicopters and you are quite right about increasing the drag by pitching the nose up - greater angle of attack = more drag which requires more power. If that power aint available the machine WILL descend. Ask Mr Newton.

Welcome to the forum, I suspect your choice of nickname may be inappropriate considering your clarity of knowledge.

[Grumpy]

I suspect your choice of nickname may be inappropriate considering your clarity of knowledge.

I'm sure it's 'short' for something like Gerard Koffer or something Hey??????
cos it surely can't be a different spelling for Jerkoff???

[ger koff]

Thank you for the warm welcome

Another problem that I have discovered is that most helicopter rotor blades are designed for relatively low altitude (ie High air density) operation. This is where they are used most of the time. On the highveld with the high density altitude the blades are past their best lift/drag ratio point. This means that when the aircraft is operating at or beyond it's MAUW or at very high altitude any increase in blade pitch results in a disproportionate increase in drag. I wonder if gyro rotor blades suffer from the same problem. Are there more "downdraught related accidents" at high altitude than at low altitude?
In an ideal world we would be able to get high altitude blades and low altitude blades, depending where you operate the aircraft most often.
Sorry for the long winded reply.

[M I Claase]

Ger koff
Daar slaan jy nou, wat my aanbetref, die spyker op sy kop! Ek vermoed al die gyros se proppellor lemme is grond verstelbaar en party sin is "varible". Die RAF se hoof rotor is grond verstelbaar vir verskillende hoogtes bo seevlak. Dit lyk vir my die beste is om hom vir so 4000vt te stel dan "perform" hy goed van 1000 tot 6000vt.
Ongelukkig is hierdie verstellings nie maklik nie en kan dit lank neem om die regte resultate te kry veral as jy dit nie gereeld doen soos die oem nie.
As jy nou tussen die lyne lees vermoed ek dit is direk waarskynlik een van die grootste bydraende faktore wat insidente met "density altitude" aanbetref veral vir ouens wat gewoond daaraan is om op laer terein (-3500vt) te vlieg en dan na hoog gelee gebiede te vlieg.Ek raai en wil se daar is min gevalle van "d a" insedente by laag liggende gebiede. Die gyros wat se rotors nie kan stel -wonder vir watter gemiddelde hoogte is hulle ingestel of varieer die rotor spoed maar net? Oor hierde onderwerp sal ek graag die opinie van istrukteurs en oem wil hoor.Ek dink dit het baie manne al in die moeilikheid gehad en dit is NIE dieselfde as "beyond the power curve" of "downdraft accidents"!

[Learjet]

From CAA Aircraft Occurrence log April:

CA18/2/3/9164 15-Apr-13 Gyro MTOSport ZU-REB NC
Onseekans -
Upington
0
Pilot experienced a down draught near Augrabies and collided with terrain, resulting in substantial
damage to the gyrocopter.
Private

And the downdraft myth keeps getting perpetuated...

I do hope the pilot involved finds it within himself to post the real facts so that we (and he) can learn how to avoid these terrible downdrafts that only seem to affect gyroplanes

As for the CAA which really should know better by now.... ja well, maybe too much "draught" being consumed there

not that he is alone though... another mysterious downdraft victim in the USA this month as reported on Steve_SP's informative website http://gyroaccidents.blogspot.co.uk/

1st June 2013 - near Hebron, Maryland, MD, USA - Air Command gyro - the pilot states the gyrocopter was being flown at 30 feet above ground level and at 40 knots indicated airspeed. The gyro started to lose altitude and a gust dropped him down to just 5 feet above ground level before impacting into a ploughed field. The Air Command gyro rolled over with damage to the blades, propeller and mast. The pilots seat belt also tore during the accident.

airspeed...airspeed...airspeed...