sea-plane crash hawkesbury river nsw

[facthunter]

Lately there's a lot of attention given to the 30 degree bank "Limit" .A thinking person could see someone banking to the so called "limit" and still wanting to tighten the turn on base to final ," Kick in" some extra rudder. making the plane unbalanced and prone to flick. That imaginary limit may have unintended consequences.

 

A course reversal for least energy is at generally more than 30 degrees of bank , more so with a draggy plane that has a poor glide ratio. Tightest turns are also at the lowest speed that is safe, (all other things being equal) so you are serving two masters at the same time. Being encouraged to "aim " the plane where you land is also a worry if you are turning.. Nev

 

 

[Oscar]

We are all - and absolutely I include myself in the 'we' equation - trying to find rational reasons as to why an apparently very, very experienced and competent pilot, flying what we have to assume for now was a very competent and fully-operational aircraft, ended up in this really ghastly situation. I sincerely believe that those contributing to this discussion are doing so with the best intent, so that others will gain an appreciation of a situation that evolved so terribly, not engaging in any sort of point-scoring. To do so would be a travesty of useful debate and a sad indictment of a forum conversation that hopefully can help improve safe flying. I state that my pre-occupation with this event is because it happened in an area for which I have a very special and lifelong attachment - it is as if it happened in my own backyard.

 

As Nev has said above, the '30-degree limit', is merely a convenient number - it is NOT a physical limitation. The physical limitation is when the stall speed of the inside wing in a turn (and that has to be moderated by the effect of aileron position) is reached, and the outside wing is still generating lift, which drives the aircraft into a deep spin. I do not know, but imagine, that the drag of floats would lower the centre of drag possibly below the c/g, pushing the nose even further down before recovery.

 

There is a damn good reason why test pilots won't start to investigate the limits of spin characteristics without having multiple thousands of feet AGL below them. If you look at the videos of Jabiru testing - and the Jabby is a renowned benign aircraft - you will see how much height it takes to recover from a 'serious' spin entry. Even the Sunbird Seeker - an aircraft that the FAA chief test pilot who flew it out here, remarked 'has possibly the most benign stall characteristics of any aircraft I have ever flown', and recommended that the FAA consult with the aero-engineer as to how that was achieved - would go to more than 70 degrees of bank, and a few times in early testing went inverted in early certification spin testing. I know the CASA test pilot for the Seeker; that is no exaggeration.

 

Even the best pilots can be caught out. Many years ago, a mate - Paul Mander, a competition glider pilot - spiralled in while trying to climb out of low altitude, only about three kilometers from my place, over a large area of gently rolling pasture. He survived, but rather banged-up. I was horrified at the news, as I had done some minor repairs to his Pik 20B not a long time before, and immediately got in touch with him, but it wasn't the Pik, it was (from memory), a 17-metre Kestrel. His comment to me was (and I have to paraphrase here, we are talking 'way back in the day' stuff), that he'd gotten in well over his first turn just fine and 'then it just folded'. He had actually been on final approach for an outlanding - there was plenty of room for that - and hit a patch of lift, and tried to catch it.

 

Look, we all know about the effects of wind shear. If we could SEE the wind, we could fly more safely for sure. Yachties - particularly those who race competitively - become pretty good at predicting the wind shift pattern around known areas bounded by major topographical features. Pilots who tread the same path many times ( such as croppies or glider tug pilots) become attuned to the likely local wind patterns.

 

I hope, that a result of this forum discussion, readers may become more conscious of a 'danger envelope' into which one should try to NOT place oneself. That at least would be an honourable legacy for those who perished, so sadly, on a flight that should have been a wonderful experience.

 

 

[MikeBravoYanky]

Just a thought.. High aspect ratio 'should' make wing drop esp in an 'unbalanced - skid' turn more likely because the speed differential across the wing tips will be greater.. I would be interested in practical experience confirming this.. I only know of one who managed it on climb out and ended up in hospital..

 

All respect, sad thoughts and prayer for those affected by the tragedy..

 

 

[Head in the clouds]

Just a thought.. High aspect ratio 'should' make wing drop esp in an 'unbalanced - skid' turn more likely because the speed differential across the wing tips will be greater.. I would be interested in practical experience confirming this.. I only know of one who managed it on climb out and ended up in hospital..All respect, sad thoughts and prayer for those affected by the tragedy..

Again ... that has nothing to do with aspect ratio, though the effect in a skid would be increased with an increase in span ... BUT given the same span and a plane with higher or lower aspect ratio, the shorter chord of the higher aspect ratio wing would reduce the Re (Reynolds number) at which the foil would be operating, with a consequent very small (probably not enough to be detectable, in practical terms) increase in stall speed, to which you might be alluding, but simply thinking an increase in aspect ratio increases stall speed is erroneous.

 

However, with an aircraft with all things being the same (i.e. span included), except the aspect ratio, then the one with higher AR would have a higher wing-loading, and that would increase the stall speed - but what has that to do with this?

 

 

[APenNameAndThatA]

Is that really how it works? Maybe I need to refresh my understanding of physics but I would have thought if a plane is flying balanced and turned downwind it would NOT change airspeed any more than turning upwind.

 

Unless this comment relates to specifics of this particular plane i have trouble understanding it. I am guessing you mean 30degrees angle of bank rather than just turning 30 degrees left or right, but I don't understand how passing the 30 degree mark somehow induces a stall? Again assuming a balanced turn I would say it would increase your stall speed but to say that would induce a stall i find a bit simplistic.

Turning downwind definitely decreases airspeed just as turning into the wind increases airspeed, but only to the degree that the wind speed increases. If wind was gusting, then that could happen, or if a geographical feature altered the wind, then that would happen. It is a form of windshear, or at least acts like windshear.

 

A 30 degree bank (balanced turn) increases stall speed by 7%, because of the increased wing loading. (The wing has to accelerate the aircraft around the turn, as well as keep it off the ground.) So, the poster was saying, that if an aircraft turns downwind, there are two factors that combine to increase the stall speed that are both acting together, and that increases the probability of stalling. A 30 degree bank is just a rule of thumb.

 

 

[GraemeK]

Turning downwind definitely decreases airspeed ...

Oh dear, where to start?

 

 

[Chinaplate]

Oscar that makes a lot of sense. I have some experience sailing there. I am very surprised that the plane would turn left into Jerusalem Bay rather than continue to climb out to the NE and then eventually turn right to head south. The prevailing at the time of the incident at Gosford was moderate NE. So turning left would immediately reduce airspeed. If the pilot recognised a problem at this stage, any hard right would already be on the edge of stall speed. I am always amazed watching those planes and feel that they dont have a lot of margin.Does that mean that their normal mode of operation is a left into Jerusalem Bay and then climb out over the highway? That surprises me.

Mea Culpa re: turning downwind. Unmitigated retraction. I was wrong to relate the horizontal air direction specifically as being relevant to stall . :-(.

 

 

[facthunter]

I have been seriously misinterpreted also.. Talk about manoeuvring in an airmass.. Windshear and up and downdrafts, rotors, yes. Nev

 

 

[SDQDI]

Turning downwind definitely decreases airspeed just as turning into the wind increases airspeed, but only to the degree that the wind speed increases. If wind was gusting, then that could happen, or if a geographical feature altered the wind, then that would happen. It is a form of windshear, or at least acts like windshear.

I disagree with your first sentence here. Your second sentence is more on the money, yes if the wind is gusting ect that can and will change your airspeed BUT doing a nice balanced turn in a stable wind won’t have a different result going upwind or downwind. The only difference is in your ground speed.

 

A 30 degree bank (balanced turn) increases stall speed by 7%, because of the increased wing loading. (The wing has to accelerate the aircraft around the turn, as well as keep it off the ground.) So, the poster was saying, that if an aircraft turns downwind, there are two factors that combine to increase the stall speed that are both acting together, and that increases the probability of stalling. A 30 degree bank is just a rule of thumb.

Flying downwind in no way whatsoever affects your stall speed, bank angle does increase stall speed but exceeding 30degrees doesn’t magically induce a stall.

 

 

[turboplanner]

I disagree with your first sentence here. Your second sentence is more on the money, yes if the wind is gusting ect that can and will change your airspeed BUT doing a nice balanced turn in a stable wind won’t have a different result going upwind or downwind. The only difference is in your ground speed.Flying downwind in no way whatsoever affects your stall speed, bank angle does increase stall speed but exceeding 30degrees doesn’t magically induce a stall.

It doesn't MAGICALLY INDUCE a stall, but as the turn get steeper, the dynamics change and the degree of skill required to assess exactly what is happening changes. Someone has previously mentioned the G force increases. At 45 degrees (Rate 2 turn) in a level turn, it has increased enough to require additional throttle input; g force is exponentially greater again at 60 degrees , and considerable more power is required, and stall speeds by now are considerably higher than those found in normal circuits. This is all changed again by slipping and skidding, and the one that seems to take out most pilots is a tightening turn; the "I just need one more photo!" shot, or where you are focused in ground speed, or do your circuit turns based on a ground reference, and it's "oops, just missed my turn!"

This pilot had 9000 hours, 8000 of them with the added weight and drag of floats. At those hours, most pilots have got past doing beat ups, pulling tight turns, and have seen every wind there is. That's not to say they can't have a momentary lapse, but given that this airframe did crop dusting for years, condition of its components after its fatal crash in that life looked like it was ready for the tip, I wouldn't be at all surprised if a control item was fractured.

 

 

[Head in the clouds]

...... but given that this airframe did crop dusting for years, condition of its components after its fatal crash in that life looked like it was ready for the tip, I wouldn't be at all surprised if a control item was fractured.

It was crashed in 1996 and rebuilt and put back on the register in the early 2000s, so if there was a damaged control that escaped replacement through all the rebuild inspections, it took 15 or so years to manifest itself ...

 

 

[Oscar]

With great respect to all here, I think that the 'airspeed' question is immaterial. I agree with SD and Nev that airspeed per se does not change with consistent wind speed and direction.

 

However - and once again, I exhort people to look at the topography in Satellite View from Google Earth or even Google Maps and try to overlay a likely image of the flight-path onto that. With my knowledge of the area, and constrained by my very limited power flying experience, I have tried to visualise what that flight-path might have been from the pilot's perspective. I have assumed that the pilot was extremely experienced and competent in flying that aircraft and would not have willingly, or incompetently, flown the thing right on the edge of stall speed..

 

I suggest that the major operative factors here were not airspeed per se but climb gradient, SOG, air mass horizontal direction and the geographical limitations of the area..

 

Let's look first at climb gradient. In crude terms: if you have a climb gradient of - let us say - 1:10 over a flat terrain (or water), and the terrain changes to an elevation gradient of +1:10, then you have a zero climb gradient. You are not increasing your AGL distance, even though your climb angle has not diminished.

 

SOG: At a constant climb angle, turning downwind increases your SOG so climb gradient decreases. If you are flying into what amounts to a narrowing canyon, the terrain is coming up at you faster and you are effectively climbing out of it more slowly. Visually: the ground is rising around you and at the same time, your manouevering area is becoming tighter and tighter, very quickly. We recently had the double-fatal of the Icon Seaplane from turning into a narrowing 'canyon' where it did not - apparently - have the climb ability to avoid the rising terrain.

 

In that situation, the pilot has only two options: try to fly the thing onto a slow hit on the side of the terrain, or try to turn away. I posted above a picture of Jerusalem Bay, and you can see how tight and steep the sides are, and what the local terrain comprises: it's all large trees.

 

So suddenly, the very, very hostile ground is coming towards you at an increasingly fast rate. A tight turn to the right is likely the only option precluding an immediate crash. In the narrow confines of Jerusalem Bay, it appears that the pilot managed to execute that turn into wind - at least partly - successfully. Full marks to him.

 

That SHOULD have put the plane into a considerably better effective climb gradient: but then horizontal air flow hits it. From long-time local knowledge, in any half-decent Easterly, there is a strong curl-over from the Eastern side of Jerusalem Bay. So instead of achieving a useful climb gradient, the air-mass is acting as (please excuse the emotive description), a giant hand pushing you down to the ground.

 

I can all too easily imagine being the pilot, with the only choice left to me being to either fly into the side of the hill or try to tighten the turn to avoid that and hope to pull out over the water.

 

Then, geographical limitations come into play. Jerusalem Bay at water-level is on average not much more than 200 metres wide. And when full of holiday boats, a bloody narrow target when everything has already gone very pear-shaped.

 

I have very limited experience of power-flying, so do not claim to be in any way expert in my judgement. I am sure that others - and particularly, those with experience of flying a float-equipped Beaver - could provide a far better analysis of this scenario.

 

 

[turboplanner]

It was crashed in 1996 and rebuilt and put back on the register in the early 2000s, so if there was a damaged control that escaped replacement through all the rebuild inspections, it took 15 or so years to manifest itself ...

15 years is young; I seem to remember a clevis coming apart in a Mustang after 65 years - could be something that was bent or stretched in the crash. You would think virtually all the items would have been replaced by new, but sometimes someone washes the part clean and makes a management decision.

I'm certainly not raising this as a central issue.

 

 

[facthunter]

Any vertical component of movement of the parcel of air you are in adds or subtracts from the climb rate you can achieve.. IF you have a plane in a certain situation , say a required turn and you already need all the power, if there's curlover (rotor) the front part of it may easily have a down effect of well over 500 fpm you need to cope with.

 

A steady wind flowing down a slope will also have a downward component. If it's a tailwind and you are downslope, the ground recedes away from you at the same rate as the downward sinking of the parcel of air so you are not affected as far as contacting the ground is concerned but you are losing height.. If you are trying to fly upslope and into wind you need to counter the slope of the ground and the descending airmass. Your relative airflow is at an angle higher than normal level flight.

 

My brain's hurting check this out to see if I've made sense of it.. I hope I have. Nev

 

 

[Oscar]

Nev: I take the statement that 'Your relative airflow is at an angle higher than normal level flight' means that your relative airflow is negative relative to the ground. With which I completely agree.

 

There was a quote in one of the Press reports from the Vice-President of the Australian Seaplane Pilots Association ( if I have that right, I can't find the report at the moment) that suggested a rotor from the northern shore could have been the problem. He would have experience that I simply do not have.

 

But - FWIW- may I add here a personal experience of how strong such a rotor may be.

 

I have a mate with a Pine plantation in the area between Taragla and Oberon. |We share work on our respective farms, and on his place, we have planted, and pruned, more than 70,000 pines. About 20 years of constant work, so you can imagine. we don't f-around with fire hazard reduction work.

 

On a really serious wind day from the immediate West - directly upwind of his property - in at least 25 kts of wind, we did a hazard reduction burn on the eastern side of a ridge aligned almost due north-south. (We had permission, we were all members of the local RFS with many years of experience of hazard reductions to our credit with RFS management).

 

First line of burn, across the ridge a few metres below the edge. The wind curl-over took our burn line up to the top of the ridge and then blew it completely out. Then we went to the bottom of the hill and lit up across the face.

 

The curl-over wind took that burn-line straight up the hill to our previous break, and then the HR burn simply disappeared. Self extinguished. Not a damn spark went into my mates Pine forest, only on average about 50 metres from the line at the bottom of the hill where we lit it.

 

Curl-over is a very strong feature of wind behaviour.

 

 

[Awqward]

You’re all (most of you!) have it right...which is a relief given the opening gambit on the subject...turning into or away from wind does not affect airspeed...nor rate of climb in fpm...but it does affect climb gradient in fpnm...which is very relevant if close to the ground and trying to escape rising terrain... without knowing ANY facts my first thought was a stall / spin just like the Grumman in Perth...

 

 

[Guest deanfi]

This article by Jim Davis is quite a good read on the down wind turns , apparent slip is a interesting one

 

Dragons of the downwind turn - Australian Flying

 

 

[SDQDI]

Very well written.

 

We all can understand how our body can trick us when in imc but it never ceases to amaze me just how much our eyes can trick us in those low level situations. It is well worth doing some low level training, bit of a broken record but it is true.

 

 

[facthunter]

Currently it's not permitted. Nev

 

 

[Head in the clouds]

Currently it's not permitted. Nev

What? LL training isn't currently permitted? Which dickwit removed it from the available endorsements, and when? As far as I'm concerned it should be a compulsory part of basic training, particularly since it's the main cause of fatal crashes.

 

 

[Happyflyer]

There is an a LL endorsement form on the RAAus webpage.

 

https://www.raa.asn.au/storage/1-low-level-endorsement-fillable.pdf

 

It isn’t on the basic syllabus for RAAus or GA (RPL,PPL or CPL). Probably because widespread LL training by every instructor would result in more problems than it would solve.

 

 

[Awqward]

The FAA require either turns around a point, figure of eights or s-turns along a line feature at low level (600-1000’) as part of the practical flight test for the private licence... I did mine with a 25kt wind...useful skills...especially since the US (and the UK) allow low level flight (right down to just above the ground) provided you remain 500ft from people, vehicles, vessels or structures...

 

 

[M61A1]

What? LL training isn't currently permitted? Which dickwit removed it from the available endorsements, and when? As far as I'm concerned it should be a compulsory part of basic training, particularly since it's the main cause of fatal crashes.

It's my understanding that the training is permitted, but RAA have decided that you must have a valid reason for getting a LL endorsement.

I know two instructors that do LL, and I think it's probably the most valuable training I've done, but I have no endo.

 

There is an a LL endorsement form on the RAAus webpage.https://www.raa.asn.au/storage/1-low-level-endorsement-fillable.pdf

It isn’t on the basic syllabus for RAAus or GA (RPL,PPL or CPL). Probably because widespread LL training by every instructor would result in more problems than it would solve.

Having every instructor proficient in LL and teaching every student some basic competencies,I believe, might just save a few lives. I have read a few examples of forced landings where it would appear that the aircraft was mishandled in close proximity to the ground, resulting at best, in destruction of the aircraft and at worst, death or injury to the crew.

LOW LEVEL ENDORSEMENT (LL)

 

14. An applicant for the issue of a Low Level Endorsement must, prior to commencing training, provide sufficient reason to the RAAus Operations Manager to attain the endorsement; and

 

a. achieve a minimum of 50 hours pilot in command of a recreational aeroplane of the same Group as the endorsement is sought; and

 

b. have reached the competency standards required in Unit 1.08 of the RAAus Syllabus of Flight Training, and

 

c. pass a flight check with a RAAus Examiner, or d. provide written proof to the Operations Manager of an appropriate recognised qualification. Proof of recency may be requested.

 

Still in syllabus....Cut and paste.

 

UNIT 1.08 – LOW LEVEL ENDORSEMENT SYLLABUS

 

1. LEGAL REQUIREMENT

 

1.1 RA-Aus Operations Manual (OM) 1.2 CAR, CASR, CAO 95.55, 95.32, 95.10 2. AEROPLANE HANDLING

 

2.1 General aeroplane handling at altitude

 

2.2 Stall symptoms and recovery at altitude

 

2.3 Advanced manoeuvres at altitude

 

3. FACTORS AFFECTING SAFETY DURING LOW LEVEL FLIGHT 3.1 The effects of wind 3.2 The effects of turbulence

 

3.3 Effect of light on hazard sighting

 

3.4 Lookout

 

3.5 Obstacles

 

3.6 Bird Behaviour

 

4. LOW FLYING

 

4.1 Low level flight over flat terrain

 

4.2 Low level flight over undulating terrain

 

4.3 Low level medium turns <45° AoB 4.4 Low level steep turns 45°- 60° AoB

 

4.5 Max rate / min radius turns at MTOW

 

4.6 Slow flight

 

4.7 Methods of losing height

 

4.8 Emergency procedures

 

 

[facthunter]

Must we persist in dumbing down the essential skills of safely flying an Ultralight? I Used to teach low flying and haven't looked like killing anyone yet. It helped ME but I' not allowed to help others. Unless they do mustering. The last part of a forced landing. (or any landing for that matter) is LOW flying. so do we conveniently ignore that.?.Nev

 

 

[Blueadventures]

It's my understanding that the training is permitted, but RAA have decided that you must have a valid reason for getting a LL endorsement.Agree. I have my bfr due soon and before xmas I contacted a local instructor and asked if I could start on getting a LL. He explained that you need a reason and that he does not do them. That's understandable. My reason was not to get the endorsement just to develop / improve my skill and awareness at low level flying and in hilly wind effected areas that would be usefull accessing tight short airstrips and during any emergancy or precautionary landings I need to do. Cheers