King Air down at Essendon?
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I knew Max many years ago so I joined here to observe the outcome (and post). I do hope the authorities get to the bottom of it all. It's the ones left behind that suffer for ever & a day:-(
Jay Hook?
I wonder if the J Hook did not disengage - so the gear was physically blocked from being selected up?
It's plausible to imagine the pilot getting distracted by the stuck gear and fumbling for the J Hook release. In this scenario he would have his head inside the cockpit - and hand off the power levers. This would be the worst time to experience a power lever creep back, or a sudden power lever closure, as discussed earlier in this thread.
It's a horrible thought - a nightmare- to imagine looking up in this situation to see you are low level, low speed, off the runway centre line and diverging towards the buildings.
It's plausible to imagine the pilot getting distracted by the stuck gear and fumbling for the J Hook release. In this scenario he would have his head inside the cockpit - and hand off the power levers. This would be the worst time to experience a power lever creep back, or a sudden power lever closure, as discussed earlier in this thread.
It's a horrible thought - a nightmare- to imagine looking up in this situation to see you are low level, low speed, off the runway centre line and diverging towards the buildings.
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ATSB did say that it was a longer takeoff roll than normal.
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Maybe the pilot decided to stay on the ground a little longer than normal flight manual lift off for weight, as a precaution to pick up more airspeed for controllability reasons in case of engine failure after lift off. Quite a common practice with some pilots flying light propeller twins.
Sorry Squawk, can't say, won't say. Secret squirrel business.
And Eddie, the reason is that it deserves note - right now- is that the ATSB has a long history of sloppy investigative work and of taking the easy way out and blaming the pilot, especially a dead one. The ATSB needs to be put on notice that it will not be accepted again.
Ack. That makes more sense now.
You are not interested in airspeed because measurements are being taken from ground impact references (prop slash marks) which relate to GS.
The last data point gives a GS of 108 knots, which equals,
108*6080/60 ft/min = 10944
Four bladed prop - distance over five (one RPM) consecutive blade strikes I measure at 6.9 feet ie one complete prop rotation
Prop RPM then equals 10944/6.9 = 1,586 RPM
I used a mixture of Google Earth and the dimensions between ridges of the roof cladding to work numbers.
Connedrod, quite correct that you have no idea of the power being produced, though touchdown was with yaw about 25° and a 6° descent (rough figures).
The last data point gives a GS of 108 knots, which equals,
108*6080/60 ft/min = 10944
Four bladed prop - distance over five (one RPM) consecutive blade strikes I measure at 6.9 feet ie one complete prop rotation
Prop RPM then equals 10944/6.9 = 1,586 RPM
I used a mixture of Google Earth and the dimensions between ridges of the roof cladding to work numbers.
Connedrod, quite correct that you have no idea of the power being produced, though touchdown was with yaw about 25° and a 6° descent (rough figures).
Megan,
Hats off to you on your practical maths but can I ask what dimensions did you use for the roof cladding?
The ridges/corrugations in the cladding should be 30 cm apart. By my measurements the first five prop strikes occur over a distance of 1.82 metres or 5.97 feet. That yields an average prop rotation of 1833 rpm. As you'd expect the last five prop strikes occur over a slightly greater distance; about 1.89metres or about 6.21 feet by my measurements, yielding 1762 rpm.
I make the yaw to achieve the left and nose wheel gear marks nearly aligning as they do to be around 30°.
Last edited by MickG0105; 1st Apr 2017 at 08:51. Reason: Correct missing spacing.
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Megan,
Hats off to you on your practical maths but can I ask what dimensions did youuse for the roof cladding?
The ridges/corrugations in the cladding should be 30 cm apart. By mymeasurements the first five prop strikes occur over a distance of 1.82 metresor 5.97 feet. That yields an average prop rotation of 1833 rpm. As you'd expectthe last five prop strikes occur over a slightly greater distance; about 1.89metres or about 6.21 feet by my measurements, yielding 1762 rpm.
I make the yaw to achieve the left and nose wheel gear marks nearly aligning asthey do to be around 30°.
So what prop speed is it 2000rpm 1586 1833. So megans difference is nearly 25% ish. Thats a large difference is it not. Why is that important. Because one is in prop gov range and the other is not basically. This is an indication of the power being produced by that engine. Case in point you really cannot make any expectation of prop speed with out detail measurements this includes airspeed at inpact. If its slower than expected the inpact marks will be closer and vice versa.
The CVR is powered off the No 1 Dual Fed Bus, so named because it is powered by both the Left and Right Generator Buses.
So what prop speed is it 2000rpm 1586 1833. So megans difference is nearly 25% ish. Thats a large difference is it not. Why is that important. Because one is in prop gov range and the other is not basically. This is an indication of the power being produced by that engine. Case in point you really cannot make any expectation of prop speed with out detail measurements this includes airspeed at inpact. If its slower than expected the inpact marks will be closer and vice versa.
Power is clearly a different story but the difference between the first and last sets of five strikes may be instructive; the average prop speed slowed by less than 4% after 11 increasingly deep strikes. That might suggest that the engine was producing power.
The shape of the strikes certainly indicates that the left propeller was not feathered so it is reasonable to infer that the left engine was producing more than 200 foot-pounds of torque otherwise the auto-feather system would have opened the dump valve and feathered the prop.
As has been explained to you previously airspeed is irrelevant to the calculations; the prop strikes are on an object fixed to the ground and we have the ground speed at impact from the ADS-B data as 108 knots.
So how do we account for so much (apparent) yaw to the left?
That is a very good question. If you review the dash-cam footage it looks like the airplane yaws through about 90° to the left in less than 2 seconds; as the airplane initially climbs into view it appears to be nose-up, climbing and oriented properly with the direction of flight along the extended centre line then very quickly we see it in profile, nose-down and descending. The flight path illustrated in the ATSB preliminary report might be a gently curving arc but the airplane appears to be oriented obliquely to it in the lateral axis; both the dash-cam and the the alignment of the nose and left landing gear strike marks bear that out. Unfortunately it's difficult, if not impossible, to determine the rudder position from the dash-cam footage.
And you all have no idea whatsoever as to what constitutes courteous and professional discourse so perhaps you might heed your own advice regarding holes, cake and shutting thereof.
zanthrus, you can always be relied upon to make some stupid post, whatever the thread. Now shut YOUR cake hole. No one knows exactly what happened, and we await the ATSB report, but in the mean time we are free to discuss.
I used 700mm which is quoted as the coverage for a single sheet. I assumed that would have meant 350mm from ridge to ridge.
From the manual.
With one-engine either at idle or inoperative, flaps UP and propeller windmilling, VMCA may be as high as 108 KIAS.
Note the last groundspeed, and we can assume the airspeed, given the wind was 23005, to be the same, was 108 knots. Recommendation from the good book for practice Vmca demonstration is a minimum of 5,000 feet, clearly not something to be trifled with.
Low side governor failure, P3 air leakage?
what dimensions did you use for the roof cladding
So how do we account for so much (apparent) yaw to the left?
CAUTION
With one-engine either at idle or inoperative, flaps UP and propeller windmilling, VMCA may be as high as 108 KIAS.
Low side governor failure, P3 air leakage?
But the extrapolations from the prop strikes suggest the left engine and propellor were operating 'normally'. If they were, why would a reduction in airspeed below VMCA result in yaw to the left?
(And zanthrus, I generally refrain from following post-crash threads because they often degenerate into character assassinations of the pilot. But I don't see what's wrong with calmly discussing the mechanical and aerodynamic implications of various pieces of information such as the photos of the prop strikes and gear strikes.)
(And zanthrus, I generally refrain from following post-crash threads because they often degenerate into character assassinations of the pilot. But I don't see what's wrong with calmly discussing the mechanical and aerodynamic implications of various pieces of information such as the photos of the prop strikes and gear strikes.)
It may well have been the other way around; the yaw to the left may have caused the reduction in airspeed (and positive vertical speed).
Megan,
Could you post the photo that you have used for your calcs? The effective cover and ridge spacing is different for different profiles obviously but from the photos I've seen I can't say for sure which profile has been used. If I can I can give you the exact measurements.
Could you post the photo that you have used for your calcs? The effective cover and ridge spacing is different for different profiles obviously but from the photos I've seen I can't say for sure which profile has been used. If I can I can give you the exact measurements.
That style/type of roof panelling comes in a range of widths; 305mm, 420mm, 620mm, 700mm, 762mm, 820mm, 840mm, 930mm. The 700mm panels have four ridges per width or 175mm ridge to ridge. I think an indication of the distance between the ridges can be gained from their alignment with the rectangular HVAC ducting (900mm) and the rooftop walkways (615mm).
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=megan;9726487
Low side governor failure, P3 air leakage?
Low side governor failure, P3 air leakage?
This should show up on preflight run up.
Last edited by Eddie Dean; 2nd Apr 2017 at 08:32.