Mallard Down in Perth
Join Date: Mar 2014
Location: WA
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Different kettle of fish regarding type and purpose, but very sad coming days after Colin Barnett's breathless launch of seaplane tours to splash down in Swan River.
http://https://au.news.yahoo.com/wa/...tourism/#page1
http://https://au.news.yahoo.com/wa/...tourism/#page1
Headmaster
"So, the velocity change is still 200 kts"
I totally agree , but if say rate 2 turn ie 30 seconds the time available to accelerate this heavy mass is too short.
That is my experience, many times, especially in jetstream holding patterns.
"So, the velocity change is still 200 kts"
I totally agree , but if say rate 2 turn ie 30 seconds the time available to accelerate this heavy mass is too short.
That is my experience, many times, especially in jetstream holding patterns.
Amazing that so many people STILL get confused by airspeed and groundspeed...read the article and stop spouting rubbish that others believe and repeat.
The bottom line is FORGET about groundspeed, the wing does not care about it.
However pilot perception CAN be influenced by changing groundspeed leading to PILOT INDUCED issues.
The bottom line is FORGET about groundspeed, the wing does not care about it.
However pilot perception CAN be influenced by changing groundspeed leading to PILOT INDUCED issues.
An article for you to read:
Dragons of the downwind turn - Australian Flying
http://www.australianflying.com.au/n...-downwind-turn
Dragons of the downwind turn - Australian Flying
http://www.australianflying.com.au/n...-downwind-turn
Having made around 5000 turns onto base in aircraft from 2t to 70t, up to 30 AoB, in conditions that have given me a sudden tailwind, I call BS on all the speed and wind theories. I'm sticking with stalling AoA (possibly combined with low IAS) being exceeded and more than happy to eat humble pie if this turns out to be wrong.
As for holding, I am not aware of what system you use in that aircraft. All aircraft I have flown for the last 20 years have FMS and fly a ground track - not constant angle of bank. This is why there are speed variations - variations in rate of turn to make good the ground track.
Join Date: May 2002
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From what I have seen from the various video clips of the crash, it would appear to be very similar to the B52 crash at Fairchild AFB in Washington where the crash was attributed to cross controls and a lower wing stall. I have also seen a video of another crash in the US, this time of a Cessna at an air show which did exactly the same thing.
Last edited by PLovett; 28th Jan 2017 at 07:32. Reason: Got my AFB bases wrong
All aircraft I have flown for the last 20 years have FMS and fly a ground track - not constant angle of bank.
None of this made one bit of difference to the viability of airflow over the wing, even with 100 knot crosswind.
Just heard on ABC news (can't be arsed linking quote, trust me I'm as reliable as Facebook) that the investigation will/may take up to a year to determine the cause. Really? That long?
Thread-drift but...
Originally Posted by Iccy
The in the jets I have flown the FMS flys over the holding fixed then rate one outbound, the "width" of the hold being determined by wind effect. Then the outbound leg is determined either by time or leg length in the FMS, the inbound turn varies with wind but not over rate one
The outbound turn into a headwind can be way less than rate 1 (sometimes only 5°) because it needs to go wider to allow for the tailwind on the inbound turn.
For those who still believe in the old turning downwind furphy, despite the best efforts of the headmaster et al: Have a think about what happens if you fly constant-AOB orbits in a jet at higher levels in a steady 100 kt jetstream. Does the jet just go round and round at pretty much constant IAS, or does it alternate between stalling and overspeeding as it turns in and out of the wind?
That doesn't make sense (and certainly doesn't happen on my jalopy). If you have a hundred knot headwind into the HP, the outbound cannot be Rate 1 as there would be no chance of turning inbound anywhere near the HP inbound track.
The outbound turn into a headwind can be way less than rate 1 (sometimes only 5°) because it needs to go wider to allow for the tailwind on the inbound turn
The outbound turn into a headwind can be way less than rate 1 (sometimes only 5°) because it needs to go wider to allow for the tailwind on the inbound turn
The point being NOT a ground track as suggested above.
(PS I know YOU get this A)
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Looking at that pix just before impact. Thank you -- The Wawa Zone.
Rudder Neutral.
Elevators Neutral.
Flaps - Not Down
Aileron - Set for Left Turn ?
Ahead of the Pilot what happened apparently.
Rudder Neutral.
Elevators Neutral.
Flaps - Not Down
Aileron - Set for Left Turn ?
Ahead of the Pilot what happened apparently.
Join Date: Nov 2004
Location: Perth - Western Australia
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One can only guess if the low level and surface winds had any impact on the aircraft involved, which factor could possibly have been a negative one in the conditions leading to the crash.
The nearest surface weather-measuring site to the crash site, is at Melville Water, at Inner Dolphin Pylon.
This weather-measuring point is about 2kms from the crash site, and would give a good indication of the surface winds on Perth Water. The crash occurred on the SE end of Perth Water.
Inner Dolphin Pylon
Melville Water is the next large stretch of open water in the Swan River, just downstream of the Narrows Bridge.
Perth Water is the open stretch of water opposite Perth city, where the Mallard was intending to land.
At the time of the crash (approx 17:00Hrs local time), the surface wind at Melville Water was from the SW at 12kts, gusting to 14 kts.
At the previous 16:30Hrs reading, the wind was WSW at 14kts, gusting to 17Kts - and at 17:30Hrs, the wind was from the SW at 11Kts, gusting to 13Kts.
Normally, in Summer, a strong SW sea breeze blows across Perth and its suburbs in the afternoons, usually appearing between 11:00Hrs and 14:00Hrs.
On Australia Day, because of a strong low pressure trough located over Perth city and suburbs, the sea breeze was very weak, resulting in only a very modest breeze.
The aircraft was initially heading approximately SE and banked around to the NE, which is when the stall/port wing drop, is first observable and highly noticeable.
This effectively means the aircraft would possibly have been flying SE with a very modest crosswind, but running into a very modest tailwind on the left turn.
It's entirely likely the left turn, which changed the airflow from crosswind to tailwind, along with reduced airspeed in the bank, led to the port wing stall, and the resultant unrecoverable situation.
Latest Capital City Observations Melville Water
A screenshot of the relevant Melville Water readings around the time of the crash. Unfortunately, a number of the measurements readings from this site, were inoperative at the time.
The nearest surface weather-measuring site to the crash site, is at Melville Water, at Inner Dolphin Pylon.
This weather-measuring point is about 2kms from the crash site, and would give a good indication of the surface winds on Perth Water. The crash occurred on the SE end of Perth Water.
Inner Dolphin Pylon
Melville Water is the next large stretch of open water in the Swan River, just downstream of the Narrows Bridge.
Perth Water is the open stretch of water opposite Perth city, where the Mallard was intending to land.
At the time of the crash (approx 17:00Hrs local time), the surface wind at Melville Water was from the SW at 12kts, gusting to 14 kts.
At the previous 16:30Hrs reading, the wind was WSW at 14kts, gusting to 17Kts - and at 17:30Hrs, the wind was from the SW at 11Kts, gusting to 13Kts.
Normally, in Summer, a strong SW sea breeze blows across Perth and its suburbs in the afternoons, usually appearing between 11:00Hrs and 14:00Hrs.
On Australia Day, because of a strong low pressure trough located over Perth city and suburbs, the sea breeze was very weak, resulting in only a very modest breeze.
The aircraft was initially heading approximately SE and banked around to the NE, which is when the stall/port wing drop, is first observable and highly noticeable.
This effectively means the aircraft would possibly have been flying SE with a very modest crosswind, but running into a very modest tailwind on the left turn.
It's entirely likely the left turn, which changed the airflow from crosswind to tailwind, along with reduced airspeed in the bank, led to the port wing stall, and the resultant unrecoverable situation.
Latest Capital City Observations Melville Water
A screenshot of the relevant Melville Water readings around the time of the crash. Unfortunately, a number of the measurements readings from this site, were inoperative at the time.
737-Ng FCOM
Other types will no doubt be different. There are other protections not mentioned above as well, ie, it's not going to throw you into a 30 AOB at FL 410 ISA +15 !
Personally I think the argument is about inertia not momentum and we are actually talking about windshear.
Do the mathematical calculations still produce the same result if we hypothesise the turn taking only one second? I think they do, if you have faith in them we could jimmy up a 100knot negative windshear over one second and gather some data for the equations
( meant in a funny way, not an antagonising way )
Obviously 100kt negative windshear will see something happen, if you drag it out over a two minute hold entry then the results are benign.
Anyway, I may be wrong so I'd like to see the calculations done for one second rather than two minutes.
Cheers.
The FMC computes holding patterns with constant radius turns based on current winds and FMC commanded airspeed. The pattern size is limited to FAA or ICAO protected airspace. In LNAV, the AFDS tracks the holding pattern using up to a 30 degree bank angle. Strong winds or airspeed in excess of FAA or ICAO entry speeds may result in the airplane flying outside the protected airspace.
Personally I think the argument is about inertia not momentum and we are actually talking about windshear.
Do the mathematical calculations still produce the same result if we hypothesise the turn taking only one second? I think they do, if you have faith in them we could jimmy up a 100knot negative windshear over one second and gather some data for the equations
( meant in a funny way, not an antagonising way )
Obviously 100kt negative windshear will see something happen, if you drag it out over a two minute hold entry then the results are benign.
Anyway, I may be wrong so I'd like to see the calculations done for one second rather than two minutes.
Cheers.
Join Date: Jan 2017
Location: Perth
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Anyone know what the effect of hitting the water would have had on the props? Would hitting the water have the same effect as and on land where prop blades tend to bend back significantly when hitting the ground under high power settings?
Images on the West Australian website today showing the recovery of the aircraft show no apparent damage to the props on one engine and only a slight bend to one prop blade on the other engine.
https://thewest.com.au/news/wa/plane...-ng-b88367962z
Is this an indication that the engines weren't producing power at the time of the accident?
Images on the West Australian website today showing the recovery of the aircraft show no apparent damage to the props on one engine and only a slight bend to one prop blade on the other engine.
https://thewest.com.au/news/wa/plane...-ng-b88367962z
Is this an indication that the engines weren't producing power at the time of the accident?
It's entirely likely the left turn, which changed the airflow from crosswind to tailwind, along with reduced airspeed in the bank, led to the port wing stall, and the resultant unrecoverable situation.
The aircraft doesn't care if it's blowing 300 knots, it just flies merrily along its' way.
What does matter is if a pilot tries to get to a certain spot to land and misjudges their base and final turn due to the ground track, and ends up turning too tight in order to make the intended landing point.
