Beech Premier down on apprach RWY 15 WMSA
Thread Starter
Nose Down? Hmmm... how is the track yawing right? If he was trying to turn right, nose would not be down, crossed controls. .
I think he was madly trying to roll left, ailerons not effective... Rudder not effective... elevators not touched.
Pilot is making my case. No controls, not any effort to stop the roll or turn is visible, airframe totally ballistic... no attempt to arrest a 60 degree bank?
I think he was madly trying to roll left, ailerons not effective... Rudder not effective... elevators not touched.
Pilot is making my case. No controls, not any effort to stop the roll or turn is visible, airframe totally ballistic... no attempt to arrest a 60 degree bank?
Concours, are you referring to a track change to the right with an aircraft that is in a right bank? That is not indicative of yaw, it is indicative of a turn rate.
- madly trying to roll left, ailerons not effective...
- Rudder not effective...
- elevators not touched.
Wake Turbulence. Wake turbulence is always able to mess up a lighter aircraft all by itself, but this particular airport has painfully generous wake separation that is applied religiously. If there was an aircraft "the same day" in front it would be a surprise. [this is true for approaches, for takeoffs, at this airport I have more than once had to advise ATC we would take a delay of X seconds for wake separation on departing traffic]
A bank of 60 degrees by itself does not indicate that an aircraft will reach a stall AOA, but the flight path angle will degrade if the achieved lift doesn't match weight, so the pitch will increase. Being at 90 degree bank doesn't stall a wing, being at or above critical AOA does. Will the plane permit level flight at 140kts 60 AOB with a stall speed of 108Kts? nope.
In this case so far, the indication is of a lateral departure from controlled flight that then resulted in a severe dive angle, and at the time that the aircraft started to go pear shaped, it is not pulling enough g to get to stall AOA, If anything, the aircraft was at a relatively high energy point and needed to slow down to the Vref for the approach, speed itself was not the issue, something upset their coffee, enough to get a wild bank angle going.
As far as data goes, the aircraft won't have a DFDR, it will have a CVR, probably still a Fairchild/L3 2100-1010, which should provide some information. For the investigators at CAAM, there is a test and readout capability for those in Jakarta, one of few around in the area. The flight display info may give some data, and the ECU for the engines, but the CVR will give RPM anyway, and there is little likelihood that engines are related to this incident. The ADSB-out will give good information to support the video and CVR.
P.S:
at t=1s. the aircraft is wings level, at t=4s, AOB is around 45, at t=6s AOB is greater than 60, that is a reasonable roll rate, but well within the roll authority of the aircraft in normal conditions. From around t=1s to t=13s the situation has gone from a relatively normal flight path to unrecoverable, with impact about 3-4 sec later. In that time, the pilot has to determine the cause of the upset while mitigating the effect it has on the flight path. That's about the same time that Laura 004's crew had to intervene and stop the loss of the B763 way back in the 90's. Might seem easy in an arm chair, but with an aircraft that has a mind of its own, not so much. That is a similar time that the Yeti crew had to work out what the ninny in the RHS had done by feathering both engines instead of closing the power levers in Nepal.
P.P.S.: The lift dump switch is the T-handle on the center console well behind the throttles, behind the rudder trim. It is well out of the sight line of the pilot. but has its own set of alerts and warnings.
Last edited by fdr; 20th Aug 2023 at 03:20. Reason: recovery point
Thread Starter
The runway in the middle image of the ADSB data on Google is WMSA/SZB/Subang/Lapangan Terbang Sultan Abdul Aziz Shah/Sultan Abdul Aziz Shah Airport. It was the former international major airport for KL, until the opening of KLIA. It is still an international airport but is primarily a domestic, corporate and regional international airline airport. It has an ILS to RWY 15 which sometimes works, and it was the site where the B747F of Flying tigers ended up in the side of a hill from the opposite direction many years ago (ended in tears). It's actually a pretty good airport, and reasonably easy access to downtown, where the food is excellent (it's Malaysia, the food is excellent everywhere). The RMAF have some of their airlift based out of there on the west side of the airport, lots of MROs on the SW and E side of the airport. Excellent FBO there, Skypark, both sides of the airport. Old terminal had a fire years back just as we parked a visiting B747, new terminal is not bad at all, but Skypark is one of the best FBO's in SE Asia, like Wings over Asia in Seletar.
So Beech was making a turn. To final? The Twitter vid shows a Stall as he turns...he didn't recover it, and a second one caught him out...imo
So much for straight in...Or...?
Thanks Captain
Last edited by Concours77; 20th Aug 2023 at 03:48.
"Concours, are you referring to a track change to the right with an aircraft that is in a right bank? That is not indicative of yaw, it is indicative of a turn rate."
Last edited by Concours77; 20th Aug 2023 at 03:44.
Thread Starter
Nope, but done a fair share of accident investigations over 43 years. flew in this area in different militaries, and airlines and in my own jets. Have 2 cats there still...
No, it is essentially a straight in approach. Ipoh to CE gives a slight left turn to pick up the LLZ, The approach was nominal until the plane darted off to the right, and that was away from the runway.
The video shows a turn that is away from the desired course, and that cause is the 64 dollar question, what makes the plane turn unexpectedly? It doesn't have T/Rs, so they are out of the picture, an asymmetric flap may be ugly, and an inadvertent lift dump is high on the suspects. If single pilot, incapacitation would be there too. Its VFR, it isn't an instrument failure... These suggest a stall of the RH wing tip is an precipitating factor, and that suggest a limited number of options. The plane hasn't stalled n the turn, it is a stall that has caused a turn, and the stall is not from inadequate airspeed, or erroneous ADC's, GS and IAS correlate well in the start and that indicates the ADC was still good. This plane doesn't stall at 1g at 140kts...
Not sure there is a second one, the cause of the upset doesn't appear to be resolved at any point, this started bad and never got better.
The approach is straight in to RWY15, and they would have been more or less stabilised to start with, but a little fast. Configuration is still not determined, but there is no reason that the config would have directly affected the lateral attitude of the aircraft, so is no material to the event.
welcome.
Being stalled doesn't mean you are falling, it means the wing has reached or exceeded the stall AOA, At that point, maintaining level flight isn't going to occur. unless you have vectored thrust, or buckets of excess thrust, (an extra 360 or a monster Pitts will sit happily on its prop vertically, as does an F-35B or a Harrier, and when serviceable even a Yak-38 Forger will (but only till it busts). In aerobatics, stall is just another flight regime, sometimes it is needed to achieve another manoeuvre, sometimes it is what is avoided by varying g load... it's nothing special in it's own right, and the plane doesn't fall out of the sky or become uncontrolled just because of that. A stall with a yaw rate, or with asymmetry of forces will get more interesting, but it is just a AOA that needs to be managed, nothing much more than that, if you time and airspace to do so.
Interestingly, the roll rate is modest throughout this event, it just doesn't get reversed to reduce the bank angle. This event doesn't have any high rates of roll at all, it is remakable that the rates are very genteel. Almost any aircraft out flying will achieve far better than 30 degrees a second sustained roll rate after a couple of seconds of a full control deflection, even a Boeing... This event is a relatively low roll rate, and, yes, it has a steep bank angle in the final moments, but that is around 10 seconds from the start (video time covers multiple takes of the scene). Whatever happened was not arrested in time by the pilot(s), and yet was not that catastrophic. For a full spin entry, the roll rates will usually be over 90 degrees a second pretty quickly (some planes will flaff about and take forever to achieve a spin entry... some are really quick) The yaw rates into a spin will be pretty high, above 30 deg/s pretty quickly, and pitch rates will also be fairly good, same or so. Unstable spins are quite disorienting, as. are aircraft that go from upright to inverted and back again quickly... but this case, there is no appreciable yaw, the bank angle has not been mitigated, ad the plane cannot maintain a flight path in such case and so the flight path angle will steepen. Off the video, it looks like it is near vertical bank at impact, or slighty over (90-100) and around -15 pitch. (The wing bus 20 degree sweep, and from almost abeam, the tip is still forward of the wing root... ) The pitch isn't the primary problem, the bank is "what the problem is". Ordinarily, the IAS would have accelerated rapidly in an event like this, around 10-15K/s sort of minimums, and that has not happened, which is why I would suggestive lift dump actuator lengths will be telling in this case. If a flap had blown up asymmetrically, causing a roll, the drag reduces partially and the descent would result in a speed increase, that hasn't appeared to occur on the first glance of the ADSB data. Drag appears to have increased... not reduced.
Watch at around 3:20 onwards for a fail to recover Great footage before that on wing rock, and departure with immediate recovery
No, it is essentially a straight in approach. Ipoh to CE gives a slight left turn to pick up the LLZ, The approach was nominal until the plane darted off to the right, and that was away from the runway.
The video shows a turn that is away from the desired course, and that cause is the 64 dollar question, what makes the plane turn unexpectedly? It doesn't have T/Rs, so they are out of the picture, an asymmetric flap may be ugly, and an inadvertent lift dump is high on the suspects. If single pilot, incapacitation would be there too. Its VFR, it isn't an instrument failure... These suggest a stall of the RH wing tip is an precipitating factor, and that suggest a limited number of options. The plane hasn't stalled n the turn, it is a stall that has caused a turn, and the stall is not from inadequate airspeed, or erroneous ADC's, GS and IAS correlate well in the start and that indicates the ADC was still good. This plane doesn't stall at 1g at 140kts...
Not sure there is a second one, the cause of the upset doesn't appear to be resolved at any point, this started bad and never got better.
The approach is straight in to RWY15, and they would have been more or less stabilised to start with, but a little fast. Configuration is still not determined, but there is no reason that the config would have directly affected the lateral attitude of the aircraft, so is no material to the event.
welcome.
"Concours, are you referring to a track change to the right with an aircraft that is in a right bank? That is not indicative of yaw, it is indicative of a turn rate."
Not if the aircraft is Stalled, and it is not a "turn". The aircraft is falling, not flying. Can't prove it. The increasing roll rate, the falling off of the nose, the descent looks like 1g. All elements of a Spin? Just about vertical at impact...
Not if the aircraft is Stalled, and it is not a "turn". The aircraft is falling, not flying. Can't prove it. The increasing roll rate, the falling off of the nose, the descent looks like 1g. All elements of a Spin? Just about vertical at impact...
Watch at around 3:20 onwards for a fail to recover Great footage before that on wing rock, and departure with immediate recovery
Last edited by fdr; 20th Aug 2023 at 04:57.
Has it been established whether there were one or two pilots?
Perhaps a passenger was "having a go" at the controls and inadvertently stalled it by making much too rapid control movements while flying slow. This might have happened by them suddenly looking up and seeing the road on their right and 'lurching' the yoke towards it, (and maybe pulling back as well), thinking it was the runway - before PF could stop them - at which point the aircraft stalled and dropped a wing into a full spin. And then there was only very limited altitude to recover.
RIP
Perhaps a passenger was "having a go" at the controls and inadvertently stalled it by making much too rapid control movements while flying slow. This might have happened by them suddenly looking up and seeing the road on their right and 'lurching' the yoke towards it, (and maybe pulling back as well), thinking it was the runway - before PF could stop them - at which point the aircraft stalled and dropped a wing into a full spin. And then there was only very limited altitude to recover.
RIP
fdr... Many thanks. Your expertise and experience are quite evident. I am learning at a rapid rate.
What I meant to say was -1g. Accelerating descent at g. The final descent has elements of a barrel roll, that would be 1g, yes?
The AC had some lift or the descent would have been "falling".
The timing would tell. My surmise "rudder ineffective" has to do with a lack of recovery from roll right. Pilot would apply aileron and rudder in coordinated fashion. That didn't happen, or it did with no success. If the aircraft is not stalled, we are stuck with CFIT, in some form or fashion.
The only Pitch we would see if not Stalled would be NU? The "turn" is tightening, but not remarkably...stopping the descent is priority one...
Exonerating pilot(s) would involve conclusions such as incapacitation (single pilot) or ineffective controls, something broke. I lean toward the latter. The flight path is not unusual if aerobatic, but knife edge is not desirable here. Only tightening the turn would maintain altitude, as the aircraft sinks for want of (banked) lift? Pilot lost consciousness and slumped the yoke? The (seeming) lack of recovery from the Stall induced departure from track is a puzzle.
Thanks again for your posts, they are superb... conc
What I meant to say was -1g. Accelerating descent at g. The final descent has elements of a barrel roll, that would be 1g, yes?
The AC had some lift or the descent would have been "falling".
The timing would tell. My surmise "rudder ineffective" has to do with a lack of recovery from roll right. Pilot would apply aileron and rudder in coordinated fashion. That didn't happen, or it did with no success. If the aircraft is not stalled, we are stuck with CFIT, in some form or fashion.
The only Pitch we would see if not Stalled would be NU? The "turn" is tightening, but not remarkably...stopping the descent is priority one...
Exonerating pilot(s) would involve conclusions such as incapacitation (single pilot) or ineffective controls, something broke. I lean toward the latter. The flight path is not unusual if aerobatic, but knife edge is not desirable here. Only tightening the turn would maintain altitude, as the aircraft sinks for want of (banked) lift? Pilot lost consciousness and slumped the yoke? The (seeming) lack of recovery from the Stall induced departure from track is a puzzle.
Thanks again for your posts, they are superb... conc
Thread Starter
Has it been established whether there were one or two pilots?
Perhaps a passenger was "having a go" at the controls and inadvertently stalled it by making much too rapid control movements while flying slow. This might have happened by them suddenly looking up and seeing the road on their right and 'lurching' the yoke towards it, (and maybe pulling back as well), thinking it was the runway - before PF could stop them - at which point the aircraft stalled and dropped a wing into a full spin. And then there was only very limited altitude to recover.
RIP
Perhaps a passenger was "having a go" at the controls and inadvertently stalled it by making much too rapid control movements while flying slow. This might have happened by them suddenly looking up and seeing the road on their right and 'lurching' the yoke towards it, (and maybe pulling back as well), thinking it was the runway - before PF could stop them - at which point the aircraft stalled and dropped a wing into a full spin. And then there was only very limited altitude to recover.
RIP
Not definitively, but is was originally reported as 2+6
Perhaps a passenger was "having a go" at the controls and inadvertently stalled it by making much too rapid control movements while flying slow. This might have happened by them suddenly looking up and seeing the road on their right and 'lurching' the yoke towards it, (and maybe pulling back as well), thinking it was the runway - before PF could stop them - at which point the aircraft stalled and dropped a wing into a full spin. And then there was only very limited altitude to recover.
- There is no evidence of an abrupt control input, the roll rates that have been seen are well within the control authority of the aircraft if only caused by the pilot input.
- The only indication of a possible stall is the gentle roll rate away from a clearly in view 10,000' runway that is 3 miles ahead, and looks like a runaway not like a road intersection.
- Roll if related to a stall in such a manner is not consistent with a normal lateral authority or a lift altering issue that has caused part of the wing to reach stall AOA.
- This aircraft is not in a spin, with incipient or full. Are we still referring to the accident of N28JV at Kuala Lumpur? This aircraft has rolled to the right to a high bank angle, at a gentle rate, it has not pitched up, down or otherwise, the back end of the plane is tracking the pointy bit, there is no significant yaw.... so no spin. Thee is no wing rocking, there is no pitching either up or down, there is an apparent static speed stability response of the aircraft, this being an aircraft that has stick pusher, not evidently in effect. Try: google "spin".
Thread Starter
A barrel roll requires more than 1g to do unless you desire to end up in a vertical dive recovery, at which point more than 1g must be applied, or the flight terminates at the interface of tin and planet. A barrel roll is normally a modest positive g manoeuvre. It describes a smooth path inclined along an imaginary cylinder, which is a nice manoeuvre, it requires coordinated roll and pitch rates to make it smooth. To get the nose to come up from the initial entry requires more than 1g, otherwise it becomes a spiral dive. When inverted, the pitch rate is reduced, if the shape is desired to be smooth, and the airspeed is normally lower than entry. In a propeller aircraft, it also requires coordinated rudder as the trim condition is changing with airspeed. A tight barrel roll may be done at well above 1g, it can be done up to the g limit of the plane but normally it is a 2-3g+/- manoeuver. 1g will achieve a near vertical dive pretty quickly. The g loading changes throughout a smooth barrel roll, but is normally at least slightly positive at the top, which is the controlling condition for an appropriate g load and consequent appropriate roll rate. A constant roll rate at varying g loads requires constantly altering aileron inputs, It is a nice coordination exercise, mores with a big radial engine or large prop, or draggy biplane.
The AC derives lift from the wings and fuselage, tail and even the engine nacelles. If vertical resultants equal weight the plane will fly in level flight, if vertical resultant forces exceed mass, the aircraft will increase in height. Aircraft don't "fall" as such, unless dropped from a crane or otherwise. A helicopter that has mast bumped and removed the rotor will "fall".
My surmise "rudder ineffective" has to do with a lack of recovery from roll right. Pilot would apply aileron and rudder in coordinated fashion. That didn't happen, or it did with no success. If the aircraft is not stalled, we are stuck with CFIT, in some form or fashion.
Last edited by fdr; 21st Aug 2023 at 00:19. Reason: gramah
To achieve -1g takes a considerable pitch down rate in level flight, at 140kts, roughly around 8-9 degrees nose pitch down per second. Nothing in the video suggests the plane achieved any g loading that was much removed from 1g. The gz if it had been recorded before the roll would be around 0.995 or so and quite stable. If the plane had been built with slats, the value would be just below 1g, and the sum of gx and gz would give a vertical vector slightly below 1g. The plane is trimmed at the start to a given AOA that will achieve that g loading. If the lift vector is inclined, the flight path angle will degrade to a steeper flight path. If the stick pusher activates, the aircraft is "pushed" to a lower AOA, and will pitch to achieve that AOA, appropriate to the stab trim + elevator forces.
A barrel roll requires more than 1g to do unless you desire to end up in a vertical dive recovery, at which point more than 1g must be applied, or the flight terminates at the interface of tin and planet. A barrel roll is normally a modest positive g manoeuvre. It describes an smooth path inclined along an imaginary cylinder, which is a nice manoeuvre, it requires coordinated roll and pitch rates to make it smooth. To get the nose to come up from the initial entry requires more than 1g, otherwise it becomes a spiral dive. When inverted, the pitch rate is reduced, if the shape is desired to be smooth, and the airspeed is normally lower than entry. In a propeller aircraft, it also requires coordinated rudder as the trim condition is changing with airspeed. A tight barrel roll may be done at well above 1g, it can be done up to the g limit of the plane but normally it is a 2-3g+/- manoeuver. 1g will achieve a near vertical dive pretty quickly. The g loading changes throughout a smooth barrel roll, but is normally at least slightly positive at the top, which is the controlling condition for an appropriate g load and consequent appropriate roll rate. A constant roll rate at varying g loads requires constantly altering aileron inputs, It is a nice coordination exercise, mores with a big radial engine or large prop, or draggy biplane.
The AC derives lift from the wings and fuselage, tail and even the engine nacelles. If vertical resultants equal weight the plane will fly in level flight, if vertical resultant forces exceed mass, the aircraft will increase in height. Aircraft don't "fall" as such, unless dropped from a crane or otherwise. A helicopter that has mast bumped and removed the rotor will "fall".
The rudder is almost always effective, below transonic speeds. The rudder is not affected greatly by AOA, it becomes relatively more effective than the ailerons as AOA increases, as aileron effectiveness reduces. There is no evidence here of a rudder input so far, normally the rudder doesn't get much exercise in flight in a jet. Some jets will apply a turn coordination rudder input in some conditions, and in this case, I would assume but do not know as a fact that a yaw damper is installed in the aircraft. Most jets end up with a need to have a yaw damper, and if the wings are swept, then that becomes near certainly a necessity. A yaw damper failure can cause an initial roll like this, and may be a factor, however aileron or rudder remain available to compensate, they are normally very limited authority [UA585, US427 are cases where a failure mode of a yaw damper resulted in a large deflection of the rudder by the initial input of a yaw damper]
Speed stability will ensure the aircraft is wanting to pitch to a constant AOA, and that would be ANU. Stopping the descent when at a near vertical bank requires removing the bank first, and if that is due to a stall, then the stall must be resolved to gain control authority.
A barrel roll requires more than 1g to do unless you desire to end up in a vertical dive recovery, at which point more than 1g must be applied, or the flight terminates at the interface of tin and planet. A barrel roll is normally a modest positive g manoeuvre. It describes an smooth path inclined along an imaginary cylinder, which is a nice manoeuvre, it requires coordinated roll and pitch rates to make it smooth. To get the nose to come up from the initial entry requires more than 1g, otherwise it becomes a spiral dive. When inverted, the pitch rate is reduced, if the shape is desired to be smooth, and the airspeed is normally lower than entry. In a propeller aircraft, it also requires coordinated rudder as the trim condition is changing with airspeed. A tight barrel roll may be done at well above 1g, it can be done up to the g limit of the plane but normally it is a 2-3g+/- manoeuver. 1g will achieve a near vertical dive pretty quickly. The g loading changes throughout a smooth barrel roll, but is normally at least slightly positive at the top, which is the controlling condition for an appropriate g load and consequent appropriate roll rate. A constant roll rate at varying g loads requires constantly altering aileron inputs, It is a nice coordination exercise, mores with a big radial engine or large prop, or draggy biplane.
The AC derives lift from the wings and fuselage, tail and even the engine nacelles. If vertical resultants equal weight the plane will fly in level flight, if vertical resultant forces exceed mass, the aircraft will increase in height. Aircraft don't "fall" as such, unless dropped from a crane or otherwise. A helicopter that has mast bumped and removed the rotor will "fall".
The rudder is almost always effective, below transonic speeds. The rudder is not affected greatly by AOA, it becomes relatively more effective than the ailerons as AOA increases, as aileron effectiveness reduces. There is no evidence here of a rudder input so far, normally the rudder doesn't get much exercise in flight in a jet. Some jets will apply a turn coordination rudder input in some conditions, and in this case, I would assume but do not know as a fact that a yaw damper is installed in the aircraft. Most jets end up with a need to have a yaw damper, and if the wings are swept, then that becomes near certainly a necessity. A yaw damper failure can cause an initial roll like this, and may be a factor, however aileron or rudder remain available to compensate, they are normally very limited authority [UA585, US427 are cases where a failure mode of a yaw damper resulted in a large deflection of the rudder by the initial input of a yaw damper]
Speed stability will ensure the aircraft is wanting to pitch to a constant AOA, and that would be ANU. Stopping the descent when at a near vertical bank requires removing the bank first, and if that is due to a stall, then the stall must be resolved to gain control authority.
I can't see that flight path as aerodynamic flight....the turn radius is miniscule. Is there an RTL? Cuz the rudder could be keeping the nose tracking
Last edited by Concours77; 21st Aug 2023 at 00:55.
Thread Starter
It is difficult to suss looking at the AC belly on, but the AC looks well NU relative to the flight path. If the departure involves the shaker/pusher, I could see a version of Colgan here. Highly stressed, pilot pulls on the pusher, it becomes a push pull.match, pilot gaining purchase on the firewall with the right foot and rudder, well, it has happened. Legacy carrier, (Continental/Colgan)
I can't see that flight path as aerodynamic flight....the turn radius is miniscule. Is there an RTL? Cuz the rudder could be keeping the nose tracking
I can't see that flight path as aerodynamic flight....the turn radius is miniscule. Is there an RTL? Cuz the rudder could be keeping the nose tracking
It is difficult to suss looking at the AC belly on, but the AC looks well NU relative to the flight path. If the departure involves the shaker/pusher, I could see a version of Colgan here. Highly stressed, pilot pulls on the pusher, it becomes a push pull.match, pilot gaining purchase on the firewall with the right foot and rudder, well, it has happened. Legacy carrier, (Continental/Colgan)
That is close to a word salad; the flight path is the resultant of all forces acting on the body, which are rather well known, since Otto L took up jumping off Sandhills. It was within the planets atmosphere, so it is aerodynamic as a result. However, if you mean it is not following a commanded path, then that is an interesting question, and the answer is, it is following the normal behaviour of a vehicle with the forces on it that are evident. That is, lift vector & thrust. That the path is undesirable is the problem, it hasn't broken physics, it is only a question as to why the path is in the direction it is.
the turn radius is miniscule.
Not sure if you are saying that it is a tight turn, e.g., a very small turn radius:
[[color=#70757a]adjective: miniscule
- 1.
extremely small; tiny.
"a minuscule fragment of DNA"]
Is there an RTL? Cuz the rudder could be keeping the nose tracking
If you are referring to a turn coordination function ["RTL?"] of the rudder, if the aircraft has a yaw damper, then quite often (but not always) a coordinator function will be incorporated. They are of limited authority, and are usually not a linear function, the requirement for coordination is a 3rd order effect dependent on bank angle. At near vertical bank, a turn coordinator won't help much on doing anything. The aerodynamic forces and stability behaviour of the aircraft are consistent with the video, in pitch, and yaw. The anomaly here is if the pilots wanted to land on a perfectly serviceable 10,000' of concrete, then the turn is anomalous, and not removing the bank before the smoke starts issuing forth is presumable an undesired outcome.
Any aircraft rolled over to vertical bank will have the nose lower as a natural outcome, the aircraft lateral-directional stability will require that to occur. If you had a really big rudder, then that can be mitigated, but comes with the risk of resulting in a spectacular departure from controlled flight, as it introduces a yaw rate into the state of the aircraft, and that gives the potential for a very rapid stall and flick. That can be a fun manoeuvre in a Pitts or an Extra, is less enjoyable in a swept wing jet at 500' AGL.
At the risk of repeating myself, this aircraft diverges from a nominal flight path with little obvious intervention. As the attitude would be obvious to anyone in the aircraft, this was not due to missing the cue of attitude, it suggests the crew were unable to intervene meaningful to the divergence. There are not many items that will do that, and fewer than normal in this case, it doesn't have T/Rs, so they are off the list. The other item that is known is the IAS(CAS?) and GS of the aircraft, these are from different sources, but agree within reasonable margins. They indicate that the aircraft had entered a fairly impressive dive, and yet IAS and GS have not appreciably increased. That is of interest, as if the roll divergence was related to a split flap, then drag would be reduced, and a speed excursion would be likely to be observed. In the absence of that, it would appear that drag increased, and that can't be from thrust reversers (T/R's) as they are not fitted, and the only other interesting option is the lift dump. Lift dump activation in flight will give an increase in AOA to maintain a flight path with the altered CL that exists, and that then puts the tips of the wings up towards the stall AOA, in fact the whole wing, but the point of interest is the tips. The PRE1 has two vortilons on each outboard wing section, and that indicates that during flight test, the stall behaviour was needing an improvement, although, unless a substantial twist existed in the wing, the need for span wise flow control is obvious, and readily managed by many different aerodynamic mechanisms. Aileron responsiveness is dependent on AOA, and at high AOA, an initial roll that is relatively benign becomes problematic with the use of ailerons. The vortilons are effective, but they still don't stop a left roll input causing a further AOA increase of the RH wing tip, which is already high from a right roll (damping effects). Of all airports, Subang is up there in the least likely to have a wake encounter for a landing aircraft. Have only taken jets in there a couple of hundred times, and the operational frustration is the opposite to being given inadequate wake separation.
The dive is a normal body response to the extended period of flight with a high bank angle, the plane has done e xactly what it is designed to do from a lateral-directional and longitudinal static stability viewpoint.
This plane is an FAA certified aircraft, TCDS (A00010WI), and also holds EASA TC (A.073). It is certified under 14 CFR Part 23 up to amendment 52. The Part 23 Subpart B provides a fairly basic set of stability and control requirements, but they are nothing unusual. These include §23.2135 Controllability, §23.2145 Stability, §23.2150 Stall characteristics, stall warning and spins.
§23.2145 (a)(1) requires "Have static longitudinal, lateral, and directional stability in normal operations". Pretty vanilla stuff, but that is what the plane will have at all times, unless there is a biggly intervention to that. 965, as amended by Amendments 23-1 through
23-52
P.S.:
There are some excellent books out there on aircraft aerodynamics, stability & control. Fixed wing is easy, rotary S&C is far more fascinating. There is a modest amount of maths involved, but the concepts are not that hard, and the maths can be broken down into components that each make sense. Leishman, Pamedi, Perkins & Hage, Robert Nelson, Duncan, Chudoba, Abzug & Larrabee, Michael Cook, Jan Roskam, and many others have written on the subject. For helo's, Ray Prouty is hard to beat, and Wayne Johnson adds the maths. Padfield, etc make helo S&C interesting. Standard control concepts apply to all systems, and planes are just systems in the end, there is some neat physics, but it is able to be modelled and understood pretty well, and that means we can back drive the event to what is possible to determine what must have occurred.
Last edited by fdr; 21st Aug 2023 at 02:00. Reason: P.S.
RDR. Rudder travel.limiter. Constrains rudder sweep with increase in AirSpeed...
CVR. All I've got. You are a Gold mine... you could bump all but two or three of the best AV writers.
CVR. All I've got. You are a Gold mine... you could bump all but two or three of the best AV writers.
Thread Starter
Just because the aircraft is below Va doesn't mean that mishandling or handling in the face of lack of knowledge cannot bust an aircraft.
We have managed to take the tail off aircraft just from gust loads, being kind to aircraft is a good idea.
This is not relevant to the KL accident, the tail remained on the plane, and the system has almost certainly not got a rudder ratio or rudder throw/deflection/travel limiter.
P.S.: Air Asia 8501 report from NTSC states a causal factor was the RTLU unit failure, which is not supportable by the evidence. The RTLU will bring up an ECAM fault message, that indicates as well a FAC fault, FAC 1 and then later FAC 1&2. The actions by the flight crew in attempting to reset a minor fault resulted in the FCS eventually reverting to Alternate law, this is a modest downgrade of functionality, but the crew then appeared to become spatially disoriented, and the aircraft and occupants had a bad day. The RTLU may have been contributory, but any other fault causing a minor degradation would appear to have been likely to repeat the outcome, the problem was the spatial disorientation when the pilot was needed to actually be in the loop in flight. For AA-587, the rudder limited was cited by the NTSB as a contributory factor, I would contend the failure of industry awareness of certification criteria was a greater latent failure that came to the fore. The flight crew responded to a wake encounter with inputs that exceeded the design and actual strength of the aircraft, while following in part the training that the industry was giving at that time.
Last edited by fdr; 21st Aug 2023 at 05:33. Reason: PS:
Having in mind one of the passengers was a local mediatic malaysian politician, could we also consider some sort of ilicit intervention, hijack, suicide, etc?
Concours77 You say CVR is all you have? I'd assume there's EFIS/ECC logs that can be extracted by the manufacturers of said units. And I can provide you with the ADS-B data I used for the plots above. While of limited use, it helps preclude some scenarios. PM me if you want that data.
OK. (forgive me, I cannot view the video for some reason).
So, if there were no significant flight control surface movements, then there was no 'piloting' going on. But why?
Engine failure and they both looked in and PF forgot to look outside, control the flight path and keep flying?
Pilot incapacitation, and their hand pulled back the Starboard engine thrust lever as they passed out?
If so, where was the second pilot, and why did they not react?
What would an uncorrected engine failure do at this phase, in this aircraft? How much yaw/roll would result?
So, if there were no significant flight control surface movements, then there was no 'piloting' going on. But why?
Engine failure and they both looked in and PF forgot to look outside, control the flight path and keep flying?
Pilot incapacitation, and their hand pulled back the Starboard engine thrust lever as they passed out?
If so, where was the second pilot, and why did they not react?
What would an uncorrected engine failure do at this phase, in this aircraft? How much yaw/roll would result?
Whatever happened, the result was asymmetry. There is some chatter re interference w/ crew, or homicide, suicide. However, the crews' credentials want a look?
The upset was radical and seemingly immediate....
"The U.S. NASA Aviation Safety Program[2][3] defines upset prevention and upset recovery as to prevent loss-of-control accidents due to aircraft upset after inadvertently entering an extreme or abnormal flight attitude."
The upset was radical and seemingly immediate....
"The U.S. NASA Aviation Safety Program[2][3] defines upset prevention and upset recovery as to prevent loss-of-control accidents due to aircraft upset after inadvertently entering an extreme or abnormal flight attitude."
Looking at the cockpit photo there are 2 `yellow-topped knobs next to the throttles..are these `engine `run/stop` controls,as they seem to be `unguarded` and could be inadvertently operated...?
Also,if the aircraft had `speedbrakes`,where/how are they operated...SWITCH,OR LEVER...?
I have spent a few years doing airtests on ex-mil jets which have speedbrakes/airbrakes on the wings or fuselage,and I would always check their operation for symmetric extension,no yaw/roll,at low speeds before high speed extension...
To me this looks like a hurried approach,and then maybe a tecnical failure,ie,flap asymmetry,same for airbrakes/lift dump,leading to the roll...or inadvertant engine shutdown..
Also,if the aircraft had `speedbrakes`,where/how are they operated...SWITCH,OR LEVER...?
I have spent a few years doing airtests on ex-mil jets which have speedbrakes/airbrakes on the wings or fuselage,and I would always check their operation for symmetric extension,no yaw/roll,at low speeds before high speed extension...
To me this looks like a hurried approach,and then maybe a tecnical failure,ie,flap asymmetry,same for airbrakes/lift dump,leading to the roll...or inadvertant engine shutdown..
