After French authorities retrieved the MH370 flaperon from Réunion Island, they flew it to the Toulouse facility of the DGA, or Direction générale de l’Armement, France’s weapons development and procurement agency. Here the marine life growing on it was examined and identifed as Lepas anatifera striata, creatures which have evolved to live below the waterline on pieces of debris floating in the open ocean.
Subsequently, flotation tests were conducted at the DGA’s Hydrodynamic Engineering test center in Toulouse. The results are referenced in a document that I have obtained which was prepared for judicial authorities by Météo France, the government meteorological agency, which had been asked to conduct a reverse-drift analysis in an attempt to determine where the flaperon most likely entered the water. This report was not officially released to the public, as it is part of a criminal terrorism case. It is available in French here.
Pierre Daniel, the author of the Météo France study, notes that the degree to which a floating object sticks up into the air is crucial for modeling how it will drift because the more it protrudes, the more it will be affected by winds:
This translates as:
The buoyancy of the piece such as it was discovered is rather important. The studies by the DGA Hydrodynamic Engineering show that under the action of a constant wind, following the initial situation, the piece seems able to drift in two positions: with the trailing edge or the leading edge facing the wind. The drift angle has the value of 18 degrees or 32 degrees toward the left, with the speed of the drift equal to 3.29% or 2.76% of the speed of the wind, respectively.
The presence of barnacles of the genus Lepas on the two sides of the flaperon suggest a different waterline, with the piece being totally submerged. In this case we derive a speed equaly to zero percent of the wind. The object floats solely with the surface current.
This suggests a remarkable state of affairs.
Inspection of the flaperon by Poupin revealed that the entire surface was covered in Lepas, so the piece must have floated totally submerged—“entre deux eaux,” as Le Monde journalist Florence de Changy reported at the time. Yet when DGA hydrodynamicists put the flaperon in the water, it floated quite high in the water, enough so that when they blasted it with air it sailed along at a considerable fraction of the wind speed.
As point of reference, Australia’s CSIRO calculates that that the drifter buoys that it uses to gather ocean-current data pick up a 1.5% contribution from the wind. Here is a picture of one such drifter, kindly supplied to me by Brock McEwen. You can see that more than half of the spherical buoy is out of the water.
It is physically impossible for Lepas to survive when perched up high in the air. Yet the buoyancy tests were unequivocal. So Daniel pressed on, conducting his analysis along two parallel tracks, one which assumed that the piece floated high, and the other in which it floated submerged. For good measure, he also considered scenarios in which the flaperon floated submerged until it arrived in the vicinity of Réunion, and then floated high in the water for the last two days. (Note that he doesn’t present any mechanism by which a thing could occur; I can’t imagine one.)
After running hundreds of thousands of simulated drift trials under varying assumptions, Daniel concluded that if the piece floated as its Lepas population suggests, that is to say submerged, then it couldn’t have started anywhere near the current seabed search area. (See chart above.) Its most likely point of origin would have been close to the equator, near Indonesia. His findings in this regard closely mirror those of Brock McEwen and the GEOMAR researchers which I discussed in my previous post.
Daniel found that when simulated flaperons were asssumed to have been pushed by the wind, their location on March 8, 2014 lay generally along a lone that stretched from the southwest corner of Australia to a point south of Cape Horn in Africa (see below). This intersects with the 7th arc. However, as Brock has pointed out, such a scenario should also result in aircraft debris being washed ashore on the beaches of Western Australia, and none has been found. And, again, the presence of Lepas all over the flaperon indicates that such a wind contribution could not have been possible.
Pierre Daniel’s reverse-drift analysis for Météo France, therefore, presents us with yet another block in the growing stack of evidence against the validity of the current ATSB search area in the southern Indian Ocean.
The most important takeaway from this report for me, however, is the stunning discrepancy between how the flaperon floated in the DGA test tank and the “entre deux eaux” neutral buoyancy suggested by its population of Lepas. No doubt some will suggest that the flaperon may have contained leaky cells that slowly filled as it floated across the ocean, then drained after it became beached. However, I find it hard to believe that an organization as sophisticated as the DGA would have overlooked this eventuality when conducting their wind tests. Rather, I read Daniel’s report as evidence that the French authorities have been unable to make sense its own findings. I suspect that this is the reason that they continue to suppress them up to this day.
@JS
No, GPS will always yield the correct direction of travel. The fact that the course of the plane is being influenced by the wind has no effect on GPS. GPS always gives a true speed and direction. GPS does not care what forces are acting on the aircraft, it only measures the direction of travel of the antenna.
@DennisW: Which is why the differentiating the GPS-derived position vector gives you track, not heading, i.e., the direction of the velocity vector relative to the ground, not relative to the wind.
@Victor
Yes, but the velocity is derived by direct measurement, not by differentiating position which is what makes it such a powerful tool for smoothing the measured positions.
I don’t have much use for “heading” which is not nearly as useful as track. Who cares where you are pointed. What you care about is where you are actually going.
@Dennis – that’s my point. It’s not the direction the nose of the plane is pointing. As a result, it is not a path that could be flown by a human. If the heading mode on the AP is meant to replicate a compass heading being flown by a human, GPS would not be of any use. It is more akin to a human following a map, not a human following a compass. Or, as Victor stated, we’re talking TRK, not HDG.
If you fee otherwise, then sometime since GPS went online the function of HDG changed fairly dramatically. That sounds like it would have caused immense confusion and would have been avoided in favor of adding a new AP mode.
@DennisW: You might not care about heading (there are important reasons why it matters), but the discussion was about heading, not track, independent of whether the GPS-derived direction is a direct measurement of velocity or differentiating position.
@JS and Victor
You are right. Heading and track are two very different things. GPS does not measure heading with a single antenna. I won’t debate the importance of heading. I regard it in the same vein as quaterions – obsolete.
@Trip
Instinctively I think you have nailed motive. Zaharie being suicidal was a stretch, adding this method for him to accomplish it is a shambles. It would not have been considered if it had been put up against other feasible motives but there were not any and the incomprehensible cockpit breach is a huge factor. I also agree it is logical that at least one sighting of the plane is valid and McKay’s story never wavered
@buyerninety – thank you for your reply and expansion on my topic. I would like to point out it is likely difficult to judge which type of aircraft was flying at nighttime. It could have been any militarized civilian aircraft. It is good to know there was a military style formation flying with Kate’s sighting.
@all:
Not sure of the relevance of this but it appears a black box has been discovered off the coast of Somalia. This has appeared in a few Somali papers online in the past few hours. I saw a guy on Twitter mentioning it, but by the time I checked back only 15 minutes later, his tweet was removed (?) Not sure if Twitter does this or the authors themselves.
Well I’ve managed to track down the article the guy was referring to:
http://www.jariibannews.com/archives/3904
Unfortunately its all in Somali but it does contain photos of the find. I’ve tried to Google translate it the best I can but maybe others here will have more luck. And I’m pretty sure the experts here will be able to dismiss/validate the relevance within a few minutes. I don’t think the guy who discovered it claims its from MH370.
(Google translation follows):
Black box of stranded aircraft discovered (Photos)
The origin of the black box is not yet known but it was discovered by a businessman on the coast. The businessman called Major Faandhe (?) The black box contains information vital to air accident investigations. Flight recorders are insulated (?) and can withstand temperatures up to 11,000 degrees. The businessman (from Darfur?) said (?) “MH370 was missing and I was scouring the coast for aircraft and ship debris (to sell)” (Source: AP)
From another site:
http://www.puntlandvision.com/2016/05/05/xeebta-garacad-oo-uu-kusoo-caariyay-wax-loo-maleynayo-sanduuqa-madow-ee-diyaaradaha/
Locals (?) said “they thought he was carrying a black box but didn’t know for sure.” Diameter is less than a meter and it feels heavy and the colour is orange.
(End of translation).
Forgive me if I’ve got the translation all wrong. But at least the first article contains pics.
@Susie Crowe
Well, yeah. I’ve been advocating that scenario from the get-go. It is obvious to me that the diversion was intentional with a political motive. That theory is reinforced by the Malay response.
When I criticize other posters, i.e. IG folks, it is for the very reason that their scenarios lack any coupling to causality or motive. How can you possibly be taken seriously from that perspective?
Of course, IG folks are easy targets, and I sometimes feel bad about it (just kidding, I don’t feel bad about it).
Oleksandr,
Perhaps you can answer this. Is the fuel pump needed for fuel dumping? And wasn’t there something with the ac buses and the fuel pump connection did I read way back? Or what was it that powers or connects to the fuel pump? Could the left ac bus have been reconnected for fuel related purposes and as a consequence came the aes/sdu reboot?
Trip / Susie Crowe,
That motive may be all well and good and for all we know it may be right. It has been what Dennis W. has postulated all along. I agree a non-murderous Zaharie fits much better than a suicidal or murderous Zaharie. But………the two problems I have with it are seasoned and methodical Zaharie runs out of fuel? And Fariq simply goes along with it all? Or did they play the ever so now popular game of let’s lock one another out of the cockpit and Fariq was locked out in your scenarios?
DennisW,
Me too! ;o)
“@JS and Victor
You are right. Heading and track are two very different things. GPS does not measure heading with a single antenna. I won’t debate the importance of heading. I regard it in the same vein as quaterions – obsolete.”
If you mean quater-N-ions, they are far from obsolete. Very useful in 3D geometric modelling, 3D animation, kinematics modelling, etc. I am sure the list is loooong.
@VictorI,
I am not sure I understand your reference to wind in the context of HDG.
Isn’t HDG the direction with respect to the fixed reference of true N, or the semi-fixed reference of local magnetic N, depending on whichever reference is selected? It has nothing to do with wind.
Wind is one of the factors that causes the deviation/difference between HDG and TRK.
@DennisW
I had not forgotten the scenario’s provenance and immediately thought of you and Stevan G. when I read Trip’s comments, I realize now my words did not reflect that. Intentionally or not, discussing motive is usually, quickly and easily deterred.
@Cheryl
The potential cockpit lock out, albeit with precedent, does not seem to fit here. Trip mentioned cultural compliance from Fariq which seems reasonable.
You have often made some astute observations with your outside the box thinking. I have often thought one of your ideas may eventually be the key to the answer.
@AM2
Thank you for the save on my hideous translation, 5 years of French 40 years ago has taken it’s toll. No one had stepped up to answer Oz and my assist, was not.
@Susie Crowe.
No worries. I’m still hoping someone would provide a proper translation of the conclusions page. Please 🙂 I thought some of the wording there was odd or even incorrectly spelled (e.g. a fleur d’eau versus affleure a la surface de l’eau) but my 5 yrs of French a long time ago isn’t enough either.
@Jeff. Do accented characters in text cause a post to be held for moderation?
The FCOM states the conditions that put the autopilot in ATT mode. VictorI is correct. There is no push button that selects ATT mode. You can disengage TRK/HDG HOLD by selecting another mode or by disengaging the AP. If you make an imput on the control wheel to set up a small bankangle you disengage the AP and your back to the conditions cited in the FCOM. We’ve been over this at length.
@Oleksandr.
I was thinking about the possible auto pilot mode with a fixed decent rate of 0.1 you and VictorI were discussing.
Which could lead to a position around 29S 98E and a altitude there around 15.000ft (coming from 35.000ft). A question was asked; why should anyone choose such a setting?
I think it could make sence in an all controlled flight with a pre-calculated destination.
A hijacker/pilot with the intend to ditch and hide a plane in a well chosen pre-calculated location might well choose to set a fixed decent rate for the purpose of being on a certain lower altitude within close reach of his destination.
For setting up a glide around this altitude free oxygen would be available and cabin pressure would be endurable after main power supplies are lost/cut off and only RAT would be available.
Makes any sence to you?
@all:
Oops! Clearly an older flight recorder (duh!) circa 70’s (?), sorry for wasting your time all that clicked the link. The guy posing next to his find a la Blaine Gibson combined with the exotic Somali script and making a late night/early morning post all got me carried away! Still, quite interesting how sturdy these things are!
Susie Crowe,
Thanks so much for the nice compliment, it made my day as I am having a particularly rough go of it this week. You as well have had some keen insights and ideas here.
Jeff, Victor, ALSM, Oleksandr, Oz, Dennis, Brock, Bruce, so many others, we’ve got brilliant men here and Jeff may be right, we are close to solving it.
Sometimes I wish we were all in the same city and could meet with Jeff at a big round table meeting and go over this thing from day before take-off to terminus, laying out what we know piece by piece.
But so many nights I walk away from my computer shaking my head saying to myself, gee I need 25 “Basil Rathbones” to solve this thing.
@Cheryl,
“We’ve got brilliant men here.”
Don’t forget the women!
Definitely off topic but still of interest with regard to response during a crisis in those parts:
http://www.freemalaysiatoday.com/category/nation/2016/05/06/dca-last-contact-with-copter-made-3-minutes-into-flight/?google_editors_picks=true
Almost a 4 hour gap before emergency response or even SAR is activated. Implicitly speaks volumes about that night in March 2014. Maybe “glacial speed” describes it best. And no prices for guessing who is at the helm.
@Sajid UK. Thanks for that report Sajid, still very interesting even though, as you say, it’s not likely to be connected to MH370. btw, I didn’t know the black boxes floated, do the modern ones float?
@AM2, Accented characters shouldn’t cause a problem, as far as I know. Sometimes comments mistakenly go to the spam folder–if something went missing, tell me what time you posted it and I can look for it there.
@MuOne: The heading is both the direction the plane is pointed as well as the direction of the velocity vector relative to the wind. (I am assuming the plane has no yaw.) A plane landing in a strong crosswind provides a great illustration of heading, track, and wind.
@DennisW The work of the IG is data driven – period. They are more focused on the location science. Perhaps it is a good thing that they are thus so preoccupied, leaving speculation as to various scenarios to other good people found here. While questioning their work in the spirit of peer review is appropriate, I see no reason to denigrate their work or otherwise drop random remarks that are clearly (and intentionally) disrespectful in tone.
As for Zaharie, many people, me among them, have long ago stated that perhaps he diverted the plane for political motives. If he did so, then I would say that the return to Malaysia is indicative of his intent to land the aircraft in Malaysia, more so rather than somewhere else. In any case, it really does not make all that much of a difference as to whom was responsible for the hijacking, while political motivation (including weaponization) perhaps provides the most probable rationale above other motives (e.g., cargo theft).
A more interesting point is that the aircraft apparently did not make a landing in Malaysia or apparently anywhere else. Meanwhile, its flight dynamics inclusive of flying to the point of fuel exhaustion further bolster, at least in my eyes, that no matter the intended destination at the point of diversion or who hijacked the aircraft and for whatever (most likely) political motive – the plan was foiled.
How, then, the hijacking was foiled and to what extent Malaysians at whatever levels in military and civilian bureaucratic org structures have knowledge of the events that led to whatever form of intervention that foiled the hijacking is where the digging needs to be done. One can hope, as Brock has stated, that a whistle blower will eventually step forward and spill the beans on what transpired that night.
Meanwhile, the work of those devoted to the location science continues.
@Victor
From my limited understanding, bto provides the distance from the satellite and bfo tells us if the plane was moving toward or away from the satellite. The bto defines the ring. The bfo provides possible solutions for assumed speed, elevation and heading. The bto would only have a single solution while the bfo could have any number of solutions depending on assumptions.
The assumption of a straight flight at a particular heading and speed leads us to the locations we are searching. Changing one, two or all 3 could lead us to a different solution. We know the reasonable limits of speed from say 550 down to say 200 (stall?), elevation limits of 38000 down to 0, and heading either south or north.
what would the location look like if we altered these assumptions? I know we also need to consider the baseline bfo.
What if the 0019 ping happened after landing? Where is
the bfo for that location? You had published a bfo analysis that showed a 0 final bfo over China.
Can we look at the range of possible locations with each ping? In other words use a 3 variable analysis to show the range of possibilities. Then at each ping consider the range of vectors rather than looking at this as a single solution. Combining the 9 pings together then may lead to a different location altogether.
I hope this close to being correct. Thanks for your thoughts.
@Sajid,
it’s fascinating – I’m just wondering which aircraft it might have come from.
It doesn’t have to be from THE plane in order to be of interest – perhaps there is a long forgotten accident waiting to be solved, and perhaps it will make a difference.
I hope they guy has handed it in to the authorities.
@Trip: Because of the way the SATCOM (partially) corrects for Doppler shift, the BFO is more of an indication of the N-S component of velocity rather than the line-of-sight component of velocity.
Because of frequency drift that may occur in the SDU, the BFO is probably more of a general indicator of a northerly vs a southerly path, rather than something that can be used with great precision.
Yes, a series of paths can be reconstructed as a function of position at 19:41 and speed, and these paths would in general be curved. If you allow speed changes along the path, even more possibilities exist. The range of possible paths would extend along the 7th arc, in rough numbers, from around 40S to 10S. Unfortunately, this would be an unrealistically large area to search.
Additional assumptions or insights are needed to constrain the search area to something manageable, such as the assumption of level, automated flight after 19:41. There is valid debate about what those additional constraints should be.
To the experts:
Is it possible to observe a drop in altitude in the BFO values from and between the 19:41 and the 00:11 handshakes?
@AM2:
Here is a translation of Page 18 of the report in idiomatic English. Hope this helps!
___________________________________________________________
Conclusions
The reverse calculations derived from the place where the flaperon was found point to several possible locations for the flaperon on March 8, 2014, according to the hypotheses made about its buoyancy.
Using the buoyancy hypothesis that resulted from the work done by DGA Techniques Hydrodynamiques (scenarios 1 through 3), the places where the flaperon could have been on March 8, 2014 are located on an axis extending from the southwest of Australia (Cape Leeuwin) to the western Indian Ocean, south of 35°S. The probability of this is at most 21%.
Using the hypothesis that the flaperon floated just at the surface of the water, without being blown by the wind (scenarios 4 through 6), the places where it could have been on March 8, 2014 are located much farther north in the vast ocean areas stretching from east of Diego Garcia to the Timor Sea and west northwest of Australia. The probability of this is at least 70%.
http://aviafilms.com/photos/flight-recorder.jpg
Russian letters are seen on the support.
@Susie and Sajid,
Don’t forget, we are still missing a stolen/hijacked B727 from 2003:
http://www.airspacemag.com/history-of-flight/the-727-that-vanished-2371187/
@Sajid UK: The flight recorders that were recovered from MH17 can be seen in the link below. Likely the MH370 recorders are similar.
http://static.euronews.com/articles/274918/606x340_274918.jpg?1405999862
@ Victor re: Coriolis effect:
OK, I dusted off the spreadsheet/numerical simulation, and set it up to model an aircraft in HDG HOLD mode, crossing the equator at 93 degrees at time = 19:20, which is reasonable. If, from that point, assuming zero winds, and a constant southerly velocity of 380 knots (heading held constant at 180 TRUE), the end point at 00:11 is -30.67°, 96.75°. That is not far from the 6th arc.
No, I did not check the other arcs, and yes, I assume a spherical Earth. This is for purely illustrative purposes only. The point being that if in HDG HOLD mode, if you don’t take into account Coriollis, you will have an error on the order of 200 nm for the purposes of MH370 paths.
I did read Brian Anderson’s paper that was linked to. It does not discuss Coriolis at all.
If you ask any average pilot about Coriolis, they will either shrug their shoulders or say it does not affect them. That’s because as a practical matter, it does not ordinarily affect them. Most likely, they will use an autopilot that heads for waypoints. Or if they want to use compass directions, they will put it in a “TRACK HOLD” mode. And even if they use a HDG HOLD mode, they will have a destination in mind, and will adjust the heading accordingly as they go along; any Coriolis effects they will chalk up to crosswinds.
But in a scenario where, say, the pilot was incapacitated, and the autopilot was left in HDG HOLD mode, and it flew on for 6 hours over thousands of miles, Coriolis will DEFINITELY have a noticeable effect, and it is measured in hundreds of miles. At cruising speeds, even if in HDG HOLD TRUE mode, the aircraft will wind up way off in left field past the 7th arc, even assuming zero crosswinds.
Bottom line: if one is going to model curvy paths in the HDG HOLD mode, taking into account Coriolis is absolutely MANDATORY.
@Warren Platts: In the navigational mode HDG HOLD, the heading is held constant. As has been explained by @sk999 and me, and implied by the DSTG report and Brian Anderson, the plane will automatically bank to maintain a constant heading so that the Coriolis effects are compensated. You disagree in the same way @Oleksandr still believes it is possible for a B777 to enter ATT roll mode with level wings. I won’t be able to persuade either of you despite evidence to the contrary. I see nothing to be gained to continue to debate either point.
The plane will automatically bank to maintain a constant heading. Period. It does not follow that it automatically compensates for Coriolis. In order to compensate for Coriolis, it would have to be “crabbed”–that is, not pointed at the ordered heading.
No need to get snarky; this is basic high school physics.
Maybe you and the IG is right: but that would require a special computer algorithm that specifically took into account the Coriolis and keeps the plane crabbed accordingly, instead of pointed at the ordered heading. But that is not what you have been saying, nor did I get that implication from the Brian Anderson paper, nor have I heard that from a pilot on a.net or anywhere else. The burden of proof is on you.
@Ge Rijn said: “I was thinking about the possible auto pilot mode with a fixed decent rate of 0.1 you and VictorI were discussing.
Which could lead to a position around 29S 98E and a altitude there around 15.000ft (coming from 35.000ft). A question was asked; why should anyone choose such a setting?”
I was thinking of a slightly different scenario.
If you wanted to exit the plane but ensure it ditched itself as gently as possible on fuel exhaustion (ie. from a low height) then you could set a first waypoint of (say) 22k ft and a final waypoint with an altitude of (say) 400ft. The aircraft would then (?) slowly descend to reach that altitude at the final waypoint.
The problem with that seems to be that to get the curving path that meets the rings you need a *magnetic bearing* from the first waypoint, rather than a final (fixed) waypoint. How could you get the aircraft to do that?
Also, why 22k ft as the starting height? Why not (say) 20k?
I can’t see a pilot setting -0.1 deg and a magnetic heading (how would you know when it would reach fuel exhaustion – from the FMC/CDU?) but I can see a pilot setting a final waypoint with altitude which (by chance) results in -0.1 deg, simply because it’s easier.
One other thought: what (maximum) altitude could the aircraft have reached at 19.41 with it’s current weight? Would 38K be achievable?
Regarding the FDR linked earlier, looks as though Dornier holds the patent for the spherical design and according to a v helpful chap on another forum, there are a lot of Dornier aircraft in that part of Africa.
So perhaps that’s something of a lead. Whatever it is from though, it’s certainly not MH370.
@Victor thanks for your deep understanding and sorry to bother you again.
So basically we’re taking the bto ring at face value, assuming straight and level flight after fmt and figuring where the plane would intersect the 9th ring at fuel exhaustion. Then we look at the bfo at that point and see what that tells us. I guess looking at the bfo first would be too complex although it is still constrained by the parameters. However if we throw drift models into the equation we end up much farther north. What are the flight stats at possible drift end points? You shared a paper earlier that calculated bfo values along the 9th ring. If the plane was being actively flown where was the best bfo fit?
On a strictly northerly heading it seems the plane descends normally.
@Warren:
How do you compensate Coriolis when you drive your car from your home to the supermarket?
@VictorI – For what it’s worth, I agree with Warren that while there may be an algorithm that corrects for the effect, that hasn’t been stated. I realize this has gone on for some time, but it would be helpful if it was explicitly stated that 1) there is no such effect at all, 2) the effect is de minimus and indistinguishable from any wind effect, or 3) the effect is compensated.
Next question – does the Coriolis effect have any impact on either BFO or BTO? If two objects are moving at the same speed through space, is the Doppler effect zero regardless of the signal direction? I honestly don’t know.
@Warren – one other thing, assuming there is a Coriolis effect on HDG – if the heading is set to 180, the plane will reach the pole regardless. So the effect would be something of a spiral or sine or S curve, right?
@Gysbreght: Interesting point. Let’s say I was on the Bonneville salt flat, I got true compass, I set it for 000 and head north. Will I drift to the right? No. Because the ground is not frictionless.
In the air, there is air. Air causes friction, to be sure, but not as much as the ground causes. There is a thing: it’s called conservation of momentum: p = mv.
You guys are saying the air is as constraining as a pair of railroad tracks. If there was a railroad track at FL350 pointed at 180 TRUE, yes, of course, there would be no drift to the left. You guys are saying that if a 777 is set at HDG HOLD TRUE 180, then–in the absence of crosswinds, it will hug the meridian all the way to the South Pole if it had enough fuel.
But air at FL350 is not like a railroad track.
In the numerical simulation I made, the time step I used was 9 seconds. At 380 knots, that’s actually 1.76 km. The incremental Coriolis effect is going to be tiny, but real, nonetheless. Over thousands of kilometers, the tiny effects add up. Ground speed in my simulation increases, as it has to. So if there was zero wind, eventually mach considerations would increase the drag. Long before that became a factor, however, with a plane pointed at 180 in HDG HOLD, there would be the effect of a sort of “crosswind” flowing from east to west, despite the fact that the plane is drifting from west to east. That will bleed off the east-west momentum that’s conserved as the aircraft moves closer to the axis of the Earth’s rotation. A detailed simulation would have to take that stuff into account. My simulation assumes zero wind, and that the air is frictionless.
But you guys assume the air has the friction of a pair of railroad tracks. Somewhere in between is the truth. The question is whether that truth is negligible. Compared to the details on this forum that people worry about, Coriolis should be YUGE. Ignore it at your own peril…
@sk999 & @VictorI – I find your answers to be very helpful but I guess I’m having trouble wrapping my head around the Coriolis effect.
Going back to the equator spinning at 900 kts and a plane pointed due south at 450 kts, but without any atmosphere, I also got 26.5deg. Now, instead of a plane make it a helicopter. If it goes straight up from the equator doesn’t its launch point move away at 900 kts? We all know that doesn’t happen so I’m guessing the still air is also moving 900 knots keeping the helicopter hovering over its launch point, correct? How would the Coriolis effect affect the helicopter? (I’ve seen the daisy pattern in the sand made by a swinging pendulum so I know the effect exists.)
New question: lets say you have a small plane cruising due south at 100 kts but there is a 100 kt crosswind. Is the ground track 45° or is it lower because the full amount of the crosswind is not translated into the cross direction of the plane?
@JS: “one other thing, assuming there is a Coriolis effect on HDG – if the heading is set to 180, the plane will reach the pole regardless. So the effect would be something of a spiral or sine or S curve, right?”
I copied down a bunch of lines, and I guess it’s a spiral. It does hit 90 degrees south. At that point in the simulation, the time is about 09:34:22. It should have been 09:33:12, so it’s off by about a minute over a total travel time of ~14.25 hours. Not bad. Easterly velocity component at that time is 1672.45 km/hr, which is about what it should be, given that the speed of the equator is 1672.53 km/hr in my simulation.
Obviously, these are supersonic speeds that would never happen. The simulation assumes frictionless air. But still, the easterly velocity differential between the equator and 30 degrees S is ~223 km/hour. Averaged over a 5 hour flight, that’s like it would take the equivalent of a 43 km/hr crosswind to compensate.
The effect is there. Yes, air will reduce the Coriolis, but it’s not AT ALL clear that the air reduces the Coriolis effect for MH370 purposes to zero. I’d need to see some really detailed analysis to believe that. And Victor and Duncan Steel and crew have not provided it.
Presumably, if an aircraft was in HDG HOLD mode, it would maintain a constant mach speed. So to make my simulation more accurate, I would have to do it so that it held the ground speed constant (because I’m assuming zero crosswind and constant altitude, that would keep the mach constant).
Like I said before, even nuclear submarines have to take into account Coriolis. Seawater has a lot more friction than air. The IG ought to give some advice to the Australian and US Navies, because they’re doing it all wrong….
@Warren: An airplane travels in the direction its nose is pointing, very much like your car on its way to the supermarket. It doesn’t need a rail road track or complex algoritm to do that, it only needs to point the nose in the right direction. If the airmass it flies through is moving at certain speed and direction, you just have to add that to the airplane’s own velocity.
@Gysbreght – that’s just not true. In a high side wind the plane is crabbing and going a different direction from where it’s pointing. In a high enough headwind a plane could be going backwards while pointing forward. However small, there should always be a variance between heading and track.
Here, the assumption is along the lines of MH370 heading due south. Which path it actually took is variable even if the FMT location is known. It could have been pointing south but flying SE.
If the effect is significant as Warren suggests it could be, and if it hasn’t been factored in, the search could be way off.
@JS & Gysbreght: I can see Gysbreght’s point: He’s not saying the effect is zero, and he’s not saying that the autopilot has a special algorithm to compensate for Coriolis, he’s saying the effect is de minimus, as if the air at FL350 is like a railroad track. It could be he is right.
I’m saying the aircraft would have to be crabbed to account for a roughly 45 km/hr “crosswind”: not a lot, but not insignificant either. It’s an open question at this point. I am willing to have my mind changed….
Likewise, Warren.