ChatterBank3 mins ago
Airasia Flight Qz8501...looks Like Pilot Error
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Apparently the aircraft was climbing at a rate of 6,000 feet per minute. Do we have any aviation experts here on AB that can tell me that how much "too fast" that rate of climb was please ?
Apparently the aircraft was climbing at a rate of 6,000 feet per minute. Do we have any aviation experts here on AB that can tell me that how much "too fast" that rate of climb was please ?
Answers
The Airbus 320 maximum possible climb rate is supposed to be 3,000 feet/minute, and it now appears it actually climbed at 8,000 feet/minute. It sounds more likely that the plane was pull up by a huge updraft at such a speed that the plane disintegrate
18:50 Tue 20th Jan 2015
@237SJ
I acknowledge that turbulence can exist in a layered form, such that not all passing planes experience it. In this case, however, we are conjecturing a powerful vertical upgraught. I was only really implying that it must have been incredibly localised, in order to have not affected the 'conflicting traffic' which caused them to be denied the chance of a controlled climb.
I look forward to any mention of presence of TCAS on this particular aircraft as well as whether the pilot responded to what it was telling him or not.
I also forgot to add that climb performance at ground level is what you are likely to find in manufacturer's performance tables. Only actual pilots could tell you what the climb capability is like at cruise altitude (with payload and fuel factors to consider). Offhand, I would say that 8,000'/min starting at 34,000' is outside the performance envelope.
I acknowledge that turbulence can exist in a layered form, such that not all passing planes experience it. In this case, however, we are conjecturing a powerful vertical upgraught. I was only really implying that it must have been incredibly localised, in order to have not affected the 'conflicting traffic' which caused them to be denied the chance of a controlled climb.
I look forward to any mention of presence of TCAS on this particular aircraft as well as whether the pilot responded to what it was telling him or not.
I also forgot to add that climb performance at ground level is what you are likely to find in manufacturer's performance tables. Only actual pilots could tell you what the climb capability is like at cruise altitude (with payload and fuel factors to consider). Offhand, I would say that 8,000'/min starting at 34,000' is outside the performance envelope.
TCAS (Traffic/Collision Avoidance System) is required on all transport aircraft as well as most turbine powered aircraft regardless of service (commercial or private). The TCAS only references other aircraft equipped with the same sytem though and has nothing to do with weather or air traffic control...
I am no expert, but if normal climb is expected to be 1000feet/minute, and the manufacturer says its maximum climb the is 3000feet/minute, then if the flight recorder says its moving at 8000feet/minute, something else must have been moving it.
The Plane was going slow at the time 469knots, much slower than a nearby Emirates aircraft. That might suggest they were battling into an headwind , and that slowed it to its stall spend.
The Plane was going slow at the time 469knots, much slower than a nearby Emirates aircraft. That might suggest they were battling into an headwind , and that slowed it to its stall spend.
Winds aloft have no effect on the airspeed of an aircraft… only the ground speed, which is no factor at all in this issue. The indicated airspeed will be the same whether the aircraft is flying into or with a wind.
The indicated airspeed of 469 knots is near maximum for the aircraft, however at altitudes above around 25,000 feet above sea level (Flight Level 250) speeds are calculated in percentage of Mach rather than knots per hour (kph). Usual cruise speed (discounting head or tail winds which only affect ground speed) the Mach speeds average .82 Mach or so.
Additionally, although it seems anti-intuitive, winds aloft have no affect on the stall speed of any aircraft. The "stall" is an aerodynamic loss of lift usually, but not necessarily due to low airspeeds… the actual, measured speed of the aircraft through the air. What is meant is that the only thing that actually produces a stall is an angle of attack (angle of the wing to air through which it is flying) that is to great, which most often occurs at slow speeds but can occur at high speeds if the angle of attack is induced sufficiently by abrupt or aggressive elevator control input.
The elevator is the horizontal control on the tail section at the rear of the aircraft. It controls the aircraft around one of three axis… the pitch axis… that is the position of the nose up or down in relation to the horizon.
The sustainable rate of climb decreases with altitude. At sea level it can be reasonably high… say 3,000 to 5,000 feet per minute. But that requires a high deck angle (the angle of the entire aircraft as measured with the surface over which it is flying). The higher one flies the less that sustainable rate becomes to the point that the last few thousands of feet to assigned cruise altitude are often 1,000 feet per minute or less. I've seen less than 500 feet per minute in a Boeing 727 on a warm day and trying to climb a heavily loaded aircraft to 37,000 feet (Flight Level (FL) 370). (Air temperature contributes significantly to aircraft performance since it relates to the density of the air… colder air, better lift and vice versa).
Finally, ground based weather radar can actually tell the velocity of up and down drafts. Several years ago, a Lockheed 1011 landing at Dallas, Texas was caught in a "down burst" that was measured to be in excess of 10,000 feet per minute. Sadly, the aircraft was incapable of escaping from it before crashing into the surface.
Here in the Great Plains of the United States, super cells (the worst thunderstorms) often produce baseball and grapefruit sized hail (not to mention tornadoes) because of the extreme speeds of the updrafts within. Such updrafts have been known to reach 150 to 175 MPH, or about 12,000 to 15,000 feet per minute, with the added terror of having nearly as severe downdrafts adjacent to the updraft within a mile or less causing wind shear that most aircraft could not survive.
Super cells are not common in the tropics, but have been reported...
The indicated airspeed of 469 knots is near maximum for the aircraft, however at altitudes above around 25,000 feet above sea level (Flight Level 250) speeds are calculated in percentage of Mach rather than knots per hour (kph). Usual cruise speed (discounting head or tail winds which only affect ground speed) the Mach speeds average .82 Mach or so.
Additionally, although it seems anti-intuitive, winds aloft have no affect on the stall speed of any aircraft. The "stall" is an aerodynamic loss of lift usually, but not necessarily due to low airspeeds… the actual, measured speed of the aircraft through the air. What is meant is that the only thing that actually produces a stall is an angle of attack (angle of the wing to air through which it is flying) that is to great, which most often occurs at slow speeds but can occur at high speeds if the angle of attack is induced sufficiently by abrupt or aggressive elevator control input.
The elevator is the horizontal control on the tail section at the rear of the aircraft. It controls the aircraft around one of three axis… the pitch axis… that is the position of the nose up or down in relation to the horizon.
The sustainable rate of climb decreases with altitude. At sea level it can be reasonably high… say 3,000 to 5,000 feet per minute. But that requires a high deck angle (the angle of the entire aircraft as measured with the surface over which it is flying). The higher one flies the less that sustainable rate becomes to the point that the last few thousands of feet to assigned cruise altitude are often 1,000 feet per minute or less. I've seen less than 500 feet per minute in a Boeing 727 on a warm day and trying to climb a heavily loaded aircraft to 37,000 feet (Flight Level (FL) 370). (Air temperature contributes significantly to aircraft performance since it relates to the density of the air… colder air, better lift and vice versa).
Finally, ground based weather radar can actually tell the velocity of up and down drafts. Several years ago, a Lockheed 1011 landing at Dallas, Texas was caught in a "down burst" that was measured to be in excess of 10,000 feet per minute. Sadly, the aircraft was incapable of escaping from it before crashing into the surface.
Here in the Great Plains of the United States, super cells (the worst thunderstorms) often produce baseball and grapefruit sized hail (not to mention tornadoes) because of the extreme speeds of the updrafts within. Such updrafts have been known to reach 150 to 175 MPH, or about 12,000 to 15,000 feet per minute, with the added terror of having nearly as severe downdrafts adjacent to the updraft within a mile or less causing wind shear that most aircraft could not survive.
Super cells are not common in the tropics, but have been reported...
Apologies 237SJ, apparently the plane wa flying slower.
I am getting my info from pulot and enthusiast forums. Can you comment on this...
// Noteworthy, a leaked ATC image published by Gerry Soejatman on Twitter shows the AirAsia flight climbing through 36300ft with a Ground Speed of only 353 knots: the radar screenshot shows an airplane much slower than expected at that altitude (a nearby Emirates flight at FL360 – 36,000 feet – was flying at 503 knots).
Flightradar24 receivers have tracked the flight by means of ADS-B until 06:12, when the aircraft was at FL320, 469 knots, 310° heading.
AF447 was an Airbus 330 from Rio de Janeiro to Paris that plummeted 38,000 feet in 3 minutes and 30 seconds and crashed into the Atlantic Ocean in 2009. In that case, pilots responded to a stall, induced by inconsistencies between the airspeed measurements likely due to pitot tubes being obstructed by ice, by pulling the nose up instead of pushing it down to attempt a recover.
Even though a low Ground Speed can be caused by strong head winds, the fact that nearby Emirates was cruising at 36,000 feet at a speed of 503 knots, seems to suggest that the missing Airbus 320 was probably too slow and closer to the stall speed than it should have been. //
I am getting my info from pulot and enthusiast forums. Can you comment on this...
// Noteworthy, a leaked ATC image published by Gerry Soejatman on Twitter shows the AirAsia flight climbing through 36300ft with a Ground Speed of only 353 knots: the radar screenshot shows an airplane much slower than expected at that altitude (a nearby Emirates flight at FL360 – 36,000 feet – was flying at 503 knots).
Flightradar24 receivers have tracked the flight by means of ADS-B until 06:12, when the aircraft was at FL320, 469 knots, 310° heading.
AF447 was an Airbus 330 from Rio de Janeiro to Paris that plummeted 38,000 feet in 3 minutes and 30 seconds and crashed into the Atlantic Ocean in 2009. In that case, pilots responded to a stall, induced by inconsistencies between the airspeed measurements likely due to pitot tubes being obstructed by ice, by pulling the nose up instead of pushing it down to attempt a recover.
Even though a low Ground Speed can be caused by strong head winds, the fact that nearby Emirates was cruising at 36,000 feet at a speed of 503 knots, seems to suggest that the missing Airbus 320 was probably too slow and closer to the stall speed than it should have been. //
@Clanad,
I don't know to what extent you are talking from a US perspective there. When you say 'required', I expect you mean under FAA regulations and they don't apply worldwide. I was expressing curiosity about whether TCAS is, similarly, a requirement by SE Asian authorities or if it's a 'nice to have' optional extra - ie the kind of thing a low-cost carrier might scrimp on. (I know that's a horrible thing to say but a thing I'd like to eliminate).
Incidentally, they say "aviate, navigate, communicate"; if ATC has just told you to stay where you are (flight level) and TCAS says "climb", I take it you climb *immediately* and apologise to ATC later?
I don't know to what extent you are talking from a US perspective there. When you say 'required', I expect you mean under FAA regulations and they don't apply worldwide. I was expressing curiosity about whether TCAS is, similarly, a requirement by SE Asian authorities or if it's a 'nice to have' optional extra - ie the kind of thing a low-cost carrier might scrimp on. (I know that's a horrible thing to say but a thing I'd like to eliminate).
Incidentally, they say "aviate, navigate, communicate"; if ATC has just told you to stay where you are (flight level) and TCAS says "climb", I take it you climb *immediately* and apologise to ATC later?
TBH, all of this info is coming out of eh "he said, she said" school of thought. Some people claim to have seen this or that on radar but I think they should wait until they actually see the data from the flight recorders and then they will know what the aircraft is really doing. Hypo - ATC tell pilots to hold on a certain level then that`s what they do.
ICAO (International Civil Aviation Organization) is, as the title implies, a governing body for the world's airlines and establishes standards for nearly everything aviation related. One source says it better than I; "...Starting in January 2003, the International Civil Aviation Organization mandated the use of TCAS worldwide for all turbine-powered aircraft with passenger capacity of more than 30 or with maximum take-off weight exceeding 15,000 kg. In January 2005, that mandate was extended to cover aircraft with more than 19 passenger seats or maximum take-off weight of more than 5700 kg. Today, more than 25,000 aircraft worldwide are equipped with TCAS..." (Source: MIT.edu).
The cost to equip an aircraft with the most advanced TCAS is minimal compared to the overall cost of such aircraft.
Hypo, TCAS (or ACAS as it's called in Europe) has evolved to version TCAS II Or ACAS version 7.0. Both systems operate solely by electronic contact with other TCAS equipped aircraft and the systems alone determine either "TA" (Traffic Advisory) or "RA" (Resolution Advisory) respnse requirements. The "TA" places a symbol on the multi-function screen and tracks it both vertically and horizontally with a little arrow showing expected track of the nearby aircraft.
If the system determines one or more of the TA's is going to produce a potential collision, the TCAS then generates the "RA" with verbal instructions on which way both aircraft are to turn, climb or descend to avoid the collision. If it tells one aircraft to climb and turn right, it will tell the other aircraft to descend and turn left as an example, all the while monitoring tracks with other aircraft within a certain "cube" relative to one's own aircraft.
Any pilot flight response to an "RA" will be reported by the crew immediately via radio to Air Traffic Control, who will then instruct all affected aircraft on what to do next as far as altitudes and headings are concerned.
SJ's example of the BA fligh is a perfect example of the seeming ability of an aircraft to fly "faster than the speed of sound" when in reality what's occuring is the extreme tailwind is causing the aircraft to pass over the surface of the earth at that speed. The crew would not know any difference from the instrument indications in the cockpit... the airspeed indicator would still indicate either knots per hour or percentage of Mach normally experienced... only the navigation system, especially the Distance Measuring Equipment (DME) which also indicates ground speed, would indicate the truly abnormal speed referenced in the article.
Totally agree with SJ on awaiting data from all the recorded events from the aircraft to make any judgements... especially as to "pilot error"...
The cost to equip an aircraft with the most advanced TCAS is minimal compared to the overall cost of such aircraft.
Hypo, TCAS (or ACAS as it's called in Europe) has evolved to version TCAS II Or ACAS version 7.0. Both systems operate solely by electronic contact with other TCAS equipped aircraft and the systems alone determine either "TA" (Traffic Advisory) or "RA" (Resolution Advisory) respnse requirements. The "TA" places a symbol on the multi-function screen and tracks it both vertically and horizontally with a little arrow showing expected track of the nearby aircraft.
If the system determines one or more of the TA's is going to produce a potential collision, the TCAS then generates the "RA" with verbal instructions on which way both aircraft are to turn, climb or descend to avoid the collision. If it tells one aircraft to climb and turn right, it will tell the other aircraft to descend and turn left as an example, all the while monitoring tracks with other aircraft within a certain "cube" relative to one's own aircraft.
Any pilot flight response to an "RA" will be reported by the crew immediately via radio to Air Traffic Control, who will then instruct all affected aircraft on what to do next as far as altitudes and headings are concerned.
SJ's example of the BA fligh is a perfect example of the seeming ability of an aircraft to fly "faster than the speed of sound" when in reality what's occuring is the extreme tailwind is causing the aircraft to pass over the surface of the earth at that speed. The crew would not know any difference from the instrument indications in the cockpit... the airspeed indicator would still indicate either knots per hour or percentage of Mach normally experienced... only the navigation system, especially the Distance Measuring Equipment (DME) which also indicates ground speed, would indicate the truly abnormal speed referenced in the article.
Totally agree with SJ on awaiting data from all the recorded events from the aircraft to make any judgements... especially as to "pilot error"...
Footnote for news editors (and pedants)
If its knots that you're talking about, it's not "knots per hour". Knots is short for "nautical miles per hour".
Thanks for the clarification, Clanad. My understanding was that the whole reason for the invention of TCAS was that ATC does, once in a blue moon, make mistakes. Worse still, from the pilot's perspective, picking out the instruction being aimed at your callsign from amongst otherwise continuous radio chatter (in high-traffic airspave) is a far from perfect way of receiving an emergency instruction when split-seconds count. Obey your instruments!
Latest hearsay (ABC World News, as repeated on BBC News channel) is that the CVR has a cacophony of cockpit alarms sounding, including the stall warning. I can only assume the pilots were unconscious, at this stage (the bulletin is either heavily edited by BBC or just terse by nature but would have mentioned pilot comments if there had been any to report).
If its knots that you're talking about, it's not "knots per hour". Knots is short for "nautical miles per hour".
Thanks for the clarification, Clanad. My understanding was that the whole reason for the invention of TCAS was that ATC does, once in a blue moon, make mistakes. Worse still, from the pilot's perspective, picking out the instruction being aimed at your callsign from amongst otherwise continuous radio chatter (in high-traffic airspave) is a far from perfect way of receiving an emergency instruction when split-seconds count. Obey your instruments!
Latest hearsay (ABC World News, as repeated on BBC News channel) is that the CVR has a cacophony of cockpit alarms sounding, including the stall warning. I can only assume the pilots were unconscious, at this stage (the bulletin is either heavily edited by BBC or just terse by nature but would have mentioned pilot comments if there had been any to report).
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