Plane Crash Barossa Valley 26/6

[alf jessup]

You have two considerations in turbulence. Not losing control and not breaking the airframe. If proximity to the stall is your main concern you fly a bit faster . Doing that can cause extra load to the airframe as extra lift is available. There is a speed where the aircraft can have full control deflection and it won't break. What you do with this information is a bit of a mystery to me. Why would you give it full control deflection? Nev

Nev,

 

NOT in any way saying this is the case in this accident but lots of full control deflections have been done over the years I bet when a pilot pops out of the clouds and see's a windshield full of paddock coming at them at an alarming rate, end result is usually a dart spearing in to the ground as the wings amongst other parts have usually departed the fully intact aircraft the moment the application of control deflection was applied.

 

Alf

 

 

[tecnamdave]

In trying to get my head around in what went wrong. I believe that the pilot and passenger had just departed an airfield at Rowland flat. So I imagine they would have been on climb out and if facing the hi ground they would have had to do a climbing turn at around 500 ft being a very cloudy and fogy morning and have found themselves in cloud and unable to put the nose down. I am terrified just thinking of this

 

 

[motzartmerv]

Yes va is clearly something that confuses most.

 

The problem with full deflections is the rapid rate that full deflections will make a 'change' to the aeroplane.

 

If you suddenly rip the stick back and you are above VA , this rapid pitch Change will increase loads to a dangerous point. If you are flying at or below va, this full deflection will not cause load problems becuse the wing will stall before it reaches load limits.

 

The reason VA increases with weight is due to the extra enertia, or the aeroplanes tendency to " resist" change . So when you are light an fluffy, the aeroplane can change attitude much more rapidly. Add weight , increase enertia, and the same control deflection won't effect change as quickly:) so VA is increased.. Clear as mud??

 

 

[rankamateur]

Thanks Andy, my instructor didn't teach me that!

 

I guess most students would turn to mush if you tried to teach them everything you know over a few weeks or months.

 

 

[dan3111]

This is only my two cents worth , just a strange item in that last photo . It looks to be a headset in the rudder if so with my pea brain I would think that would indicated the canopy would had to be open before impact for it to go back ward into the tail . Just only a guess may be a cockpit white out and they opened the canopy at some point to try and see. The crashes I have been to the head sets have gone out the front of the plane I towards impact point

 

.

 

 

[rankamateur]

This is only my two cents worth , just a strange item in that last photo . It looks to be a headset in the rudder if so with my pea brain I would think that would indicated the canopy would had to be open before impact for it to go back ward into the tail . Just only a guess may be a cockpit white out and they opened the canopy at some point to try and see. The crashes I have been to the head sets have gone out the front of the plane I towards impact point .

It might have been hung there by a rescuer untrained in preserving the crash site!

 

 

[turboplanner]

This is only my two cents worth , just a strange item in that last photo . It looks to be a headset in the rudder if so with my pea brain I would think that would indicated the canopy would had to be open before impact for it to go back ward into the tail . Just only a guess may be a cockpit white out and they opened the canopy at some point to try and see. The crashes I have been to the head sets have gone out the front of the plane I towards impact point.

The photos don't really show whether the siding section is there at the site.

 

 

[Phil Perry]

No one ever says anything dumb on this forum, do they?

OF COURSE THEY DON'T . . . . . . . .No need for sarcasm ( ! ) No one says anything dumb on Purpose ( do they . . .? )

 

Phil XX

 

 

[Phil Perry]

indeed, pretty sure if you strap those afterburner equipped monster fuel pumps to a concrete brick it could be made to fly!

I'm sure it might. . . .BUT. . . .Since the F15 is a total "FLY-BY-WIRE" design, with fully reactive and independent computer controlled flying surfaces, then, in the event, having one wing missing was, apparently. . . not a total extinction event on the day. . . . . . . Whether or not this was a foreunner of the Chesly Sullenberger airliner landing in the Hudson River, the simulation of which no pilot has, thus far been able to copy, we shall never know, until another F15, . . or Eurofighter wing is blown off in combat . . . .

The Israeli pilot reported that he had to land the machine at a much higher airspeed than was normal, ( perhaps due to the missing mainplane ? ) but the rest of the controls reacted in such a manner that continued flight AND the landing manouvre were possible, albeit with some difficulty, but not impossible for a well trained and "switched on" pilot, which, was obviously the case in this instance. Whether this was a "One - Off" we may nrever get to find out. . . . .

 

Phil

 

 

[bushpilot]

On topic -

 

Plane Crash Barossa Valley 26/6..

 

..So that I don't have to read all 7 pages here - is the summary of relevant the observations that it was loss of control in cloud? I have a student coming to Bathurst today to fly her Tecnam and she is bound to ask. (I know its all subject to the investigation, etc... but Im just asking about opinions).

 

 

[biggles]

On topic - Plane Crash Barossa Valley 26/6..

..So that I don't have to read all 7 pages here - is the summary of relevant the observations that it was loss of control in cloud? I have a student coming to Bathurst today to fly her Tecnam and she is bound to ask. (I know its all subject to the investigation, etc... but Im just asking about opinions).

Chris ,

 

There are all sorts of theories posted here , but really that's all they are . Suggest you contact our Ops Man. She should have had some feedback from our Investigator by now .

 

Bob

 

 

[turboplanner]

On topic - Plane Crash Barossa Valley 26/6..

..So that I don't have to read all 7 pages here - is the summary of relevant the observations that it was loss of control in cloud? I have a student coming to Bathurst today to fly her Tecnam and she is bound to ask. (I know its all subject to the investigation, etc... but Im just asking about opinions).

It could have been.

 

Also, from photographs it appears the left wingtip was deflected upwards, and departed the aircraft prior to the crash, being shown relatively undamaged in bushes said to be a kilometre away, and its not clear whether the canopy was at the crash site, so another possibility is that the aircraft broke up in turbulence.

 

The NAIPS forecast was for moderate to severe turbulence, so my message would be to always access the NAIPS service which is mandatory anyway, and in this case my decision would have been to park the aircraft.

 

A secondary lesson would be that the NAIPS service provides an aviation based Met report which warns of things like turbulence. We are all well aware of the visibility requirement for VFR flight, and a lot of people just look out the club room window, but turbulence is not something you can see.

 

 

[turboplanner]

Also what Bob says, although the problem we have there is that RAA cannot release data that Police can't release prior to the Coroner's Hearing, and that could be a couple of years away.

 

 

[biggles]

Also what Bob says, although the problem we have there is that RAA cannot release data that Police can't release prior to the Coroner's Hearing, and that could be a couple of years away.

Yes I am very aware of that Turbs . All I'm suggesting is that , in regard to Chris' s concerns , is that a talk to our Ops. people would be the best course of action at this stage .

 

Bob

 

 

[ave8rr]

Also what Bob says, although the problem we have there is that RAA cannot release data that Police can't release prior to the Coroner's Hearing, and that could be a couple of years away.

If the accident was investigated by the ATSB then we would have a prelim report within 30 days.

I understand there is a move afoot to have this happen.

 

 

[Guest Nobody]

Yes va is clearly something that confuses most.The problem with full deflections is the rapid rate that full deflections will make a 'change' to the aeroplane.

If you suddenly rip the stick back and you are above VA , this rapid pitch Change will increase loads to a dangerous point. If you are flying at or below va, this full deflection will not cause load problems becuse the wing will stall before it reaches load limits.

 

The reason VA increases with weight is due to the extra enertia, or the aeroplanes tendency to " resist" change . So when you are light an fluffy, the aeroplane can change attitude much more rapidly. Add weight , increase enertia, and the same control deflection won't effect change as quickly:) so VA is increased.. Clear as mud??

I don't think that it is due to the rate of change of control input and inertia but due to the fact that at higher weight the aircraft has a higher stall speed and therfore the wing stalls before its structural limits are exceeded. Inertia dosent come into it.

 

 

[motzartmerv]

Ok, so how can a load limit be reached without a change in direction (acceleration)?

 

Its not simply the increase in stall speed, again a common misconception.

 

 

[Ultralights]

might have something to do with what was reported in the WX?

 

 

[poteroo]

Ok, so how can a load limit be reached without a change in direction (acceleration)?Its not simply the increase in stall speed, again a common misconception.

Correct - have a look at a V-N or V-G diagram for any aircraft. The 50 fps gust lines give the answer. I'll try to post one of these flight envelope diagrams as a separate subject because it's quite informative.

 

One most important thing about wing loadings - if you deploy flaps in rough air, or with huge pilot induced accelerations - then you are asking for trouble.

 

For a Tecnam P96G, Va is 81 KIAS, and Vfe is 60 KIAS (I've seen 60 given as 'approach' speed in some info.)

 

Flaps retracted + 4.0 g to -2.0 g is the permitted range

 

Flaps 38o (full) + 1.9 g to 0.0g is the permitted range

 

Remember Va is a no flap speed. With flap extended, the wing is much weaker and it's likely the Va for flaps extended is going to be closer to 60. So, the range of IAS seems to be rather limited if you think turbulence and wing loadings.

 

Worth discussing?

 

 

[motzartmerv]

Absolutely. Let's do it :)

 

 

[Guest ozzie]

Why can't the RAAus release a prelime report within a respectable time frame. The ATSB do as well as the APF do for skydive accidents including jumpship incidents.Usually within 24 hrs. Does the HGFA ?

 

 

[facthunter]

In turbulence, particularly severe, you airspeed will be varying and the aircraft will also be subject to fairly large "G" fluctuations.( I've had a good 60 knots variation in a rotor at about 1,000 feet alt., in a c-150). That range would cause a big problem with flaps extended. Control inputs (ailerons mainly) and flap extension can cause loads that are inclined to twist wings. Your control inputs will have a big bearing on whether you survive or not and the throttle IS a control. Large pitch changes are not a good idea and don't apply large control inputs. The situation I was in was made worse by there being quite a few times when there was violent negative "G". The aircraft attitude should be loosely retained at normal for the conditions, which may be climbing, level or descending, with minimum control inputs to achieve the desired attitude, and your airspeed should aim for the safest speed but it will fluctuate about that speed and you can't (and shouldn't) try to stick to an exact speed. Aim for the correct attitude. If you don't pull the stick back it won't stall. You have several tasks Keep the plane from getting out of shape, attitude and not stalling and not imposing severe loads on the airframe..Nev

 

 

[Guest Nobody]

Ok, so how can a load limit be reached without a change in direction (acceleration)?Its not simply the increase in stall speed, again a common misconception.

I think that this can best be explained with the diagram below. Take an aircraft with the following characteristics:

 

Stall at MTOW: 50 kts

 

Stall at a light weight: 40 kts

 

VNE: 150 kts

 

Design load factors of +4.5 and -3

 

It would have an operating envelope something like the diagram below. Flight is only possible in the region in the centre of the chart. Attempt to fly outside this region and either the aircraft will stall or the aircraft will be outside its design peramaters.

 

At a speed below Va it is not possible to overstress the wings because the aircraft will stall first. Above Va it is possible to overload the wings.

 

Now stalling speed increases by the square root of load factor. A load factor of 4.5 would mean that the stalling speed will increase by a factor of 2.12. The graphs shows that the range of values for Va from 85kts to 106 knots as the weight is increased.

 

 

 

[turboplanner]

Why can't the RAAus release a prelime report within a respectable time frame. The ATSB do as well as the APF do for skydive accidents including jumpship incidents.Usually within 24 hrs. Does the HGFA ?

I think this has been explained about five times Ozzie.

 

The Police control non Recreational Aviation accidents and they call in RAA; they will not release their evidence or briefs to the Coroner, just as they do not release car accident evidence before it is presented, or for that matter murder evidence.

 

The ATSB has the legal power to investigate and report during the investigation sequence, and the mechanics of that work well. Maybe APF have similar powers.

 

I've lost track of the move for ATSB to investigate ALL aircraft accidents and that would be the best outcome.

 

However you are never going to get a full report before the final report is published anyway. Speculating may not get you the exact cause of the crash, but it sure provides a lot of great ways to prevent similar incidents.

 

One of the major difficulties with the police/coroner investigations is that they are primarily looking for a cause of death, whereas we are looking for a cause of crash so we can learn from it, and they can be two completely different things.

 

 

[motzartmerv]

Nobody. Yes I understand quite well the principle your using. It doesn't negate the relationship between load factor and acceleration. The reason the wing is being over loaded is due to the load factor being too high yea?

 

How can that load factor be increased by a control input if te aircrafts motion doesn't change? I can assure you, enertia ( acceleration) is required.