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An unstalled airliner at 20 kts isn't worth a whole lot, and a plane at coffin corner is a wind gust away from descending out of the sky.
FIxed.
You still have to increase AoA to stall. That was his point. If you lose airspeed at coffin corner and do not try to hold altitude you simply lose altitude. Of course the instinct is to hold altitude, which was my point, which is also your point.
And stop the bull crap that airspeed and high altitude don't matter.
An unstalled airliner at 20 kts isn't worth a whole lot, and a plane at coffin corner is a wind gust away from falling out of the sky in a stall.
Like I said elsewhere- good airspeed control is essential so that you almost never hear even a warning of a stall. (And don't pull up relentlessly and mindlessly).
Yeah it's an AOA/attitude thing but the management of speed and high altitude is kind of critical too.
Who said that airspeed doesn't matter? (at altitude or else)
And what coffin corners? That is a think of the U2, not of modern commercial jets.
A modern commercial airliner will never find itself where the stall speed and Md will meet.
What can happen is that you find yourself at a latitude where your run out of engines to sustain level flight. And of you try to do it by increasing the AoA as the speed goes down, you will stall. The solution is easy: go down. Plenty of room below, reduce AoA, descend, trade altitude for speed, go to thicker air where the engines have more muscle (and, if you want, where Vs and Md get farther away).
If you find yourself in a powerful updraft that takes you uncontrollably up because you need so much nose-down attitude to hold the altitude that idling the engines and extending the spoilers is not enough to prevent overspeeding, well, accept the climb and keep the speed at Mmo/Vmo. You will eventually exit the updraft flying very fast in M/TAS, and that can be somehow slow in IAS, it will be hardly stall speed. You might have not enough thrust to sustain your new cruise level (which might also happen even if you don't climb in the updraft: it can bring warmer air from below which, at this altitude, is less dense and might put yourself past your ceiling for this IAS+X condition), and why would you want to. Go down.
Note the elaw said that it would stall because of the thin air not because the airspeed. I added airspeed just as an additional item in the list. You know: you can stall (or not stall) an any altitude, attitude, airspeed and air thickness.
Of course that speed is critical, because you normally want to sustain 1G, and to do that you need a lift = weight, and to do that you need at least enough speed that will give you that lift at that AoA.
Now, of you don't have that speed, you will not hold 1G. (and this little point is...). You can depart 1G flight by keeping the AoA below critical or by not doing it and stalling. Your choice.
Said lose of airspeed can be caused by a number of reasons. Typically, pilot intervention (yes, BAD pilot intervention, flight itself is pilot intervention).
Other reasons could be atmospheric (most typically a windshear, but let's also imagine the plane flying at a healthy airspeed that is instantaneously displaced up so much that the same TAS now is insufficient IAS).
In any event, what will cause the stall is the increase of AoA, not the lose of airspeed by itself.
If you are in your Cessna 172 flying at and trimmed for 80 kts and, for whatever reason, your speed suddenly drops to 30 kts, that doesn't mean that you will unavoidably stall. Well, a brief transient stall will be unavoidable, but let alone the plane will stall to fall from the loss of lift, the air will hit the tail from below, and the nose will go down to its trimmed AoA again. It would help if you, rather that trying to prevent the nose drom and conserve altitude, pushed down and advanced the throttle so you can regain a 1G-compatible speed as soon as possible.
You will never hear me say that speed is not important. But AoA is more.
You can be NOT stalled an any airspeed, even below the stall speed.
You cannot be NOT stalled and any AoA. At some AoAs you WILL be stalled no matter the speed.
And you can't be at 1G below the stall speed. Now combine this with the previous two sentences and decide how you will depart 1G flight.
And remember elevator controls speed? Did you note that what's required to recover the stall (or avoid one in the first place) and increase the speed is the same thing?
Now, I appreciate that a 100kt updraft is hardly a smooth, laminar flow wind. If you don't break up at the first encounter, you can break up later or lose control in a number of ways. But this is another subject from the plane finding itself in thinner air and stalling.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
INDONESIAN search ships have detected signals believed to be from the flight recorders of the AirAsia plane that crashed into the Java Sea last month with 162 people on board.
"THREE ships equipped with ping detectors received pings from the same location," said Ridwan Djamaluddin, from the Agency for the Application of Technology, whose ship was involved in the search.
He said the ping came from a location about one to four kilometres from where the aircraft's broken tail section was retrieved on Saturday.
"We are confident it's from the black box," he said, referring to the voice cockpit recorder and the flight data recorder.
Searchers lifted the aircraft's tail from the bottom of the sea on Saturday but did not find the recorders.
Data from the recorders help investigators determine the chain of events leading to an accident, and its root cause.
Officials said the recorders, which are normally located in a passenger jet's tail, could have been detached from the plane as it crashed.
The search to find the black boxes is a race against time as the devices' batteries are designed to transmit signals for up to 30 days. The plane crashed on December 28.
The homing beacon emitted by one of the recorders appeared to be about a kilometre from where the tail section was found, based on the signal detected by Indonesian ship KN Jadayat.\
AirAsia flight QZ8501 was flying from Surabaya to Singapore when it disappeared from radar somewhere above the Karimata Strait in the Java Sea.
So far, 48 bodies have been retrieved from the water, but no survivors have been found.
You still have to increase AoA to stall. That was his point. If you lose airspeed at coffin corner and do not try to hold altitude you simply lose altitude. Of course the instinct is to hold altitude, which was my point, which is also your point.
Ummm wrong... An upward wind gust is going to cause a stall. And a speed loss gust is very likely to cause a stall. At coffin corner you literally are at the critical AoA and if you lose speed the plane may fall and get you the magical 16.1 degrees of AOA before it can nose over...
Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
That was a bit too much for the Del Norte division who sees speed control as extremely important (not that a relentless pull up can't trump a healthy air speed).
But there are some damn important interactions with speed.
Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
An upward wind gust is going to cause a stall.
And a speed loss gust is very likely to cause a stall. At coffin corner you literally are at the critical AoA and if you lose speed the plane may fall and get you the magical 16.1 degrees of AOA before it can nose over...
WHAT
COFFIN
CORNER
???????
In both cases, yes, there can be a transient stall. With the updraft, the stall can be immediate but the plane will quickly pitch down to it's trimmed AoA. It's the static longitudinal stability at play. The AoA was disturbed and it will be restored.
In the speed loss gust, things are more slow motion. It's the dynamic longitudinal stability at play (phugoid).
Figure this scenario:
- You are flying at 100 kts (say that your 1G stall speed is 90 kts). Load factor = 1. Lift = weight.
- You are hit by this gust and the speed goes down to 80 kts. Do you stall NOW?
- No. The AoA hasn't changed. The AoA was not disturbed, and that's why we won't have the quick response of the static stability.
- But you are not longer at 1G. For the same AoA, lift goes with the square of speed. 80^2/100^2 = 0.64. Now lift is 0.64 times the weight. You are at a load factor of 0.64. What happens?
- It is no brainer. We were happily in steady flight and suddenly we have a great reduction in lift, down we go. The plane accelerates down. The sink rate, that was zero until now, starts to increase. It's just starting. We are still at time 0. The altitude hasn't changed yet. Neither the AoA.
- Now as the sink rate starts to develop, with the pitch initially in the same position, the AoA starts to increase. The lift starts to increase too, both in the wing as in the tail, which now starts to lower the pitch.
- So now you have the plane increasing the sink rate, increasing the AoA because of that, but reducing the AoA due to the nose going down in the other hand. In the beginning, the net effect is an increase in the AoA. But this increase is smaller and smaller every second.
- The question is whether the AoA will stop increasing before reaching the stall AoA. It doesn't matter so much (especially not at high altitude, where ground clearance is not of immediate concern).
- At one point the AoA will stop to increase (where in a stall or not) and will start to reduce.
- The plane will go to recover the original trim AoA, the one where 100kts is 1G.
- When it reaches that AoA, the plane will still be nosing down because the speed is still below the 1G speed of 100 kts.
- Eventually the plane will achieve 100kts, now it has the same speed and AoA that at the beginning, so it's at 1G and the nose stops going down.
- Except that the plane is descending more than what it's needed to keep 100kts, so it will overshoot 100kets and start to nose up.
- And then will follow a series of oscillations in pitch, altitude, vertical speed, and airspeed around 100kts. Phugoid 101.
Oh, and the pilot was just along for the ride. pilot intervention can help... or not. If he helps the plane do what it's trying to do (go for the trim AoA and airspeed), it will help. If, on the contrary, he fights the plane, he will actively stall it.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
Wow, more than 1 km away from the tail? Doesn't this imply there was some sort of mid air breakup?
It could, but not necessarily.
It could mean that the black box separated at impact and, being a quite small and heavy item, wen straight to the bottom, while the tail was slowly sinking while drifting with the current.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
You will never hear me say that speed is not important. But AoA is more.
You can be NOT stalled an any airspeed, even below the stall speed.
You cannot be NOT stalled and any AoA. At some AoAs you WILL be stalled no matter the speed.
And you can't be at 1G below the stall speed. Now combine this with the previous two sentences and decide how [not if] you will depart 1G flight [because you will, be it stalling or reducing the AoA].
But there are some damn important interactions with speed.
Go figure...
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
The flight recorder from the crashed AirAsia QZ8501 flight has been discovered in the Java Sea, Indonesian authorities confirmed in a statement.
According to the country’s Directorate General of Marine Transport, the black box will be retrieved from the seabed on Monday.
"The navy divers in [the] Jadayat state boat have succeeded in finding a very important instrument, the black box of AirAsia QZ8501," said Tonny Budiono, a senior ministry official, as cited by AFP.
According to Budiono, the divers, who found the flight recorder on Sunday, failed to retrieve it on the spot because it was stuck under debris from the main body of the plane.
Earlier on Sunday, strong signals from the recorders were detected not far from where the tail part was found.
PANGKALAN BUN/JAKARTA - Indonesian divers on Sunday found the black box of the AirAsia plane which crashed in the Java Sea a fortnight ago with 162 people aboard, the transport ministry said.
But they failed to retrieve it because it was stuck under debris from the main body of the plane, it added.
“The navy divers in Jadayat state boat have succeeded in finding a very important instrument, the black box of AirAsia QZ8501,” said Tonny Budiono, a senior ministry official, adding that it was at coordinate 03.37.21 South/109.42.42 East at a depth of between 30 to 32 metres.
"The black box is trapped under parts of fuselage. We will slowly move these obstacles out of the way, but if it does not succeed, we will lift the fuselage parts using a balloon like what we did to the plane's tail," Budiono said, adding that a small buoy marker had been placed at the location to make retrieval on Monday easier.
Strong ping signals were being picked up by three vessels involved in the search in the Java Sea, S.B Supriyadi, a director with the National Search and Rescue Agency, told reporters.
Ummm wrong... An upward wind gust is going to cause a stall. And a speed loss gust is very likely to cause a stall. At coffin corner you literally are at the critical AoA and if you lose speed the plane may fall and get you the magical 16.1 degrees of AOA before it can nose over...
Can we agree never to use the words "coffin corner" again in a thread about passenger jets? That's so 2009...
Should we edit the whole dictionary? Goofy perhaps, even morose but that is what they call it and it does get your attention which is what it's intended to do.
Why? The dictionary is fine. Just use a word within the scope of its definition.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
Rudder portion has been torn off starting from hinge and steeper angled than the fuselage, suggesting that it was torn away by secondary action, by the fuselage bottom?
There is no frontal compression damage visible, cannot see signs of metallic objects rushing towards the tail. Also the circular structures are pretty much intact, so the bottom up (flattening) forces were not very great at the moment of impact.
The forward top section of this piece is curled upwards also, so it was perhaps acting as hinge at the moment tail broke loose.
So i conclude my analysis by saying, that the plane ditched semi controlled on rough waters at 25 degrees nose high, right engine first. Possibly with high TAS (tailwind conditions?). All passengers died on the impact, bottom has been ripped away by great forces.
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