Tailspin Turtle
June 12, 2025, 15:20:00 GMT
permalink Post: 11899329

Quote:

Originally Posted by The Nutts Mutts

The more i watch that video it really looks to me like it used the entire length of the runway before finally struggling into the air without enough airspeed to maintain flight, crashing nose-high just seconds later.

My impression was very similar: they never had enough thrust for level flight with the gear down, used up the whole runway accelerating to something close to Vr, rotated and started to climb but very soon started slowing and had to reduce the angle of attack, starting the descent.

Subjects: None

Tailspin Turtle
June 14, 2025, 21:22:00 GMT
permalink Post: 11901853

Quote:

Originally Posted by MR8

You might want to rethink that.
It's approximately 1km glide from where the aircraft was at roughly 200ft, not 2 km. 1km equals about 3000ft, so that is a glide ratio of 15. Taking into account a bit of excess speed to bleed off before reaching alpha max, this sounds very feasible to me.

I wondered about that as well. The 787 reportedly has an L/D of 21. Unfortunately, Google didn't provide me with a gear-down L/D (one data set stated landing L/D was 7 but presumably that includes landing flaps as well) but it is clear from some technical reports that it is a non-trivial reduction, maybe 44%. That suggests a gear-down L/D of 12, not taking into account headwind, change of elevation, off-optimum glide speed, etc. Obviously a higher beginning altitude and airspeed and shorter distance to the crash site that stated as well as the benefit of a flare would affect the outcome. However, the difference between an L/D of 16 and 12 given the stated beginning altitude (200 ft) and distance to the crash site (1 km = 3,280 ft) raises the possibility that the engines were still producing some thrust or were coming back on line.

Aeronautical engineer, CFI, unused ATP rating, 3,000 hours in airplanes, rotorcraft, and gliders

Subjects: None

Tailspin Turtle
June 15, 2025, 03:47:00 GMT
permalink Post: 11902079

Quote:

Originally Posted by appruser

IMO
In the CCTV video, the aircraft stops climbing at 00:28. 3 seconds after, it starts visibly descending. At peak altitude, using the 197ft wingspan as a measure, the altitude is around 200ft or below. The fireball is at 00:48, 17s after descent starts visibly.
Per google maps and the impact location mapped at avherald, the impact point is ~3990ft from the airport boundary road and about 4200ft from the midpoint of the runway threshold and the airport boundary road.
16:1 to 25:1 is what I could find for the 787 glide ratio range (unpowered) with main landing gear down and flaps 5. So the aircraft could cover 16 to 25 ft horizontally for every 1 ft of descent.
With a starting altitude of 200ft, that would imply it could have covered 3200ft.to 5000ft during unpowered descent.
The actual distance covered, around 4000ft, certainly seems to suggest that the descent was unpowered.

Thanks for those numbers. Note, however, the max 787 L/D, flaps and gear up , is reportedly 21 (best in class), which casts shade on the credibility of those L/Ds, certainly 25 with the gear down. What is your source? IF the actual L/D with the gear down and flaps 5 is somewhat lower than 16 and given that starting height and distance traveled are correct\x97and considering that the aircraft might not have been at the speed for max L/D with the gear down and the possibility of a headwind\x97then there must have been some thrust during the descent (it did look to me to be somewhat flatter in that video taken from one side than I would have expected with the gear down, a relatively slow initial speed, and no thrust) or the engines were spooling back up at the end.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AvHerald CCTV

Tailspin Turtle
June 17, 2025, 12:46:00 GMT
permalink Post: 11904272

Based on approximate distances and heights, the time line, the aircraft configuration, surface wind, the published L/D (gear up reduced to a guess for gear down and RAT out), and probable off-optimum speed for maximum L/D in that configuration, it's my opinion (aeronautical engineer, unused ATP rating, and glider pilot, national contests) that we can't rule out both engines being at idle or very low thrust at or shortly after rotation, rather than shut down.

Last edited by Tailspin Turtle; 17th June 2025 at 16:28 . Reason: Added final phrase for clarification

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All)

Tailspin Turtle
June 19, 2025, 23:38:00 GMT
permalink Post: 11906487

Quote:

Originally Posted by MatthiasC172

Can someone help me with the calculations on how far from the point of our last ADS-B readout we can expect the stricken jet to fly/glide?
I am assuming the take off mass around 190-200 tons with 50 tons of fuel. For the glide phase this is of no importance, however.
Data on the Internet puts the glide ratio of a 789 around 18-21:1. Gear and flaps/slats out should have a significant negative effect. Does anyone have a good take how much? Minus 40%?
From the available data we can infer the plane never was higher than 200\x92 AAL, maybe even 100\x92. If I understood the online sources correctly, the point of impact was only about 20\x92 lower than the average runway level.
If I am not mistaken the distance from the last ADS-B point to the impact site is about 2 km as per Reuters and the Guardian. That would put it at 6,500\x92.
I just can\x92t get these numbers over each other without the aircraft producing thrust. Please help me correcting the numbers.

In prior posts, I used approximately the same numbers and came to a similar conclusion (we can't rule out the possibility that there was a least idle thrust available after the loss of thrust), using a guess of a 44% reduction for the configuration from a max L/D of 21. Starting with the height and distance being approximate however, we also don't know what the airspeed/angle of attack was at any point in the descent versus the speed for the maximum (and unknown) L/D for the gear and flaps extended and the RAT out, the amount of headwind, the increase in L/D in ground effect (at a height less than the wingspan) over other than a smooth surface, thermal activity in a urban area, the distance gained in the flare at the end, etc.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB RAT (All)

Tailspin Turtle
June 20, 2025, 00:28:00 GMT
permalink Post: 11906506

Quote:

Originally Posted by Surlybonds

Yes, we can. The RAT was deployed, which only happens if both engines are fully shutdown, or the crew manually deployed it.

Therefore the crew could have manually deployed it... (there's a button for that). If I saw the engines winding down and couldn't be sure that they would stop at idle, I'd be inclined to deploy the RAT instead of waiting for airplane to do it.

Last edited by Tailspin Turtle; 20th June 2025 at 00:53 . Reason: Add a reason for manual deployment of the RAT

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) RAT (Deployment)

Tailspin Turtle
June 29, 2025, 19:09:00 GMT
permalink Post: 11913181

Quote:

Originally Posted by GroundedSpanner

Do we think the engines are fully 'off', shutdown - Or are they struggling to provide thrust?
Listen to the rooftop video in Capn Bloggs excellent Side-By-Side video . Ignore the RAT. Try and focus on all the sound that is not RAT.
I think I can hear a pulsing, a chunk-chunk-chunk' sound.
Do we think that is the engines struggling to work?

An admittedly approximate assessment of the airplane's lift-over-drag capability, considering other conditions (head wind, ground effect, actual airspeed vs that required to maximize L/D, etc.) suggests that the engines were providing some thrust in order for it to get as far as it did. Note that simple calculations based on conversion of energy, e.g. velocity and height, to distance are even more approximate in this scenario.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All)

Tailspin Turtle
June 29, 2025, 22:41:00 GMT
permalink Post: 11913278

Quote:

Originally Posted by GroundedSpanner

Thanks but I want to separate the RAT issue from the engines/thrust issue.
Its possible that the RAT was deployed for other reasons, prior to the engines losing thrust. So, leaving the RAT out of the equation for a bit, do we think there is a sound of engines TRYING to run?

Also note that either member of the crew can deploy the RAT in addition to the automatic modes, conceivably preemptively in response to the engines losing thrust (full disclosure: at least one poster has insisted than no competent crew would ever do that in those circumstances given the multiple actions with a higher priority to be taken). Others may know if their preferred scenario explaining the simultaneous loss of thrust and automatic RAT deployment could have then resulted in the engines recovering but not soon enough to stop the descent.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) RAT (Deployment)

Tailspin Turtle
July 01, 2025, 02:09:00 GMT
permalink Post: 11913983

This is my latest attempt to square the circle using all the data points and minimal assumptions. The main shortcoming of the analysis is not knowing the maximum L/D and the speed for maximum LD with the gear down, flaps 5, and the RAT extended. However, if I use a reasonable number in my opinion for the L/D in that configuration and assume that the airplane is being flown at the speed for it, it will not get to the crash site. The distance from the runway of the crash site is from a previous graphic (1.55 km); the rotation point from fdr, permalink 314; 200 feet max height above the runway being generally accepted; crash site 50 feet below the runway elevation cited previously. An average speed of 180 knots is consistent with the dimensions given and 30 seconds flight time. A flare at 50 feet will briefly increase the L/D to 20, maybe even 30 (500 feet more than shown) but still not enough to make up the shortfall, In fact, with a head wind the L/D will be lower than assumed as well as if the speed being flown is higher or lower than required for maximum L/D in that configuration. In other words, there must have been some thrust available.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) RAT (Deployment)

Tailspin Turtle
July 01, 2025, 03:33:00 GMT
permalink Post: 11914003

Quote:

Originally Posted by MaybeItIs

Hi TT,

Can I ask a question that I guess a few observers will also want to know? Is L/D (Lift-over-Drag?) the same as Glide Slope? I.e. for an L/D of 13, does that equate to 13 forward for 1 down? If so, even at 17, it doesn't look like it would make it.

Yes - Higher numbers are better. The 787 has one of the best for an airliner, almost 21 power off.

Subjects: None

Tailspin Turtle
July 01, 2025, 13:05:00 GMT
permalink Post: 11914261

Quote:

Originally Posted by nachtmusak

There is easily-correctable available data with the aircraft's altitude at pretty much the end of the runway and it is not at 200 feet (it's around 100\xb112.5 feet).

As the aircraft visibly continues to climb past that height (and for a longer period than ADS-B data covers, if the camera's perspective casts doubt on that), it seems rather clear to me that it reached its peak height past the end of the runway.

In light of this I find the fact that people keep calculating a glide from the runway to the crash site to be a bit strange. Wouldn't the first step of any math be to try to determine where it started descending?

Thanks - I'm pretty sure that I read all the posts in both threads but missed that calculation as to the height at the end of the runway. I had originally guessed that the top of climb was 1,000 feet beyond the end of the runway (the current location is based on the referenced statement of the rotation point and an assumed ground speed, not air speed, of 180 kts). That still doesn't get the jet to the crash site, particularly if the post I relied on that it was 50 feet below the runway is incorrect. As far as the benefit of trading speed for distance, there wasn't that much extra speed to start with relative to the likely maximum L/D speed for that configuration and any slowing below it will reduce distance, not increase it, except of course for breaking the glide, i.e. flare at the end (there may have been a little benefit in rounding off the transition from climb to glide that I didn't take into account but I think it was small). My estimate for L/D based on known comparables that didn't include the RAT was actually 12, not 13, and I assumed that they were flying at the max L/D airspeed for that configuration even though it's likely that the crew didn't know what it was (and neither do I) but were following the prime directive, "don't stall". I also didn't take into account the headwind, which would reduce the maximum L/D available and require a slightly faster airspeed to make good than for no wind.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB RAT (All)

Tailspin Turtle
July 13, 2025, 23:43:00 GMT
permalink Post: 11921782

Quote:

Originally Posted by Musician

Thank you for your reply! I'm aware you know more about ADS-B than I do, and I'm happy to learn.
As you know, I'm referring to the map view and data on https://www.flightradar24.com/blog/f...rom-ahmedabad/ .

That's what I thought at first, based on the time stamps.
08:08:50.87 last full ADS-B message (172 kts)
08:08:54 APU inlet door starts to open, per the report.

My problem here is that the report also says that the maximum speed was 180 knots IAS at about 08:08:42. And we have
2025-06-12T08:08:46.550875Z,8005ec,23.069138,72.625871,575
associated with 184 kts as the first ADS-B message in the sequence.
Given that the clocks of ADS-B receivers are sometimes off, I think this might actually represent the moment of maximum speed; but then the AFS-B clock would be 4 seconds fast.
And that's why I adjusted my times.

A way to cross-check would be to track the aircraft position over time from the point of rotation, or to use the new photo in the report that shows the RAT over the runway to triangulate where that was.

Yes.
Would low pressure and high temperature make IAS lower than ground speed, even with the 7 knot headwind?

Either way, if they were decelerating at approximately 3 knots per second, then they would've ended up at about 150 knots IAS, which is less than Vr.

When I look at the CCTV video, 13 seconds into the flight, the aircraft is just "over the hump" and starts descending, so that tracks.

At this point, I don't know what having the engines spool up instead of being dead weight would've done to that flight path; and how successfully the aircraft could've been recovered from that.
Maybe they had only 4 seconds to flip those switches, instead of 5 seconds?

Still, the best bet is to not ask questions, but flip these switches back ASAP, no?

From the beginning, my impression looking at the final glide video was that they weren't sinking as fast as I would have expected with both engines failed completely. A rough analysis using 787 L/D data, revisited as more speed and altitude estimates became available, convinced me that it was very unlikely that they could have gotten that far in that configuration with not only no thrust, but the drag from that big windmilling front fan on each engine. The preliminary report states they got at least one engine turning, apparently fast enough to reduce that drag and therefore get them to the crash site. However, as tdracer opined, a few more seconds would not have allowed for enough thrust to develop to stop the descent before ground contact.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB APU CCTV Engine Failure (All) Engine Shutdown Preliminary Report RAT (All) Timeline (Preliminary Report)

Tailspin Turtle June 12, 2025, 15:20:00 GMT permalink Post: 11899329	Quote: Originally Posted by The Nutts Mutts The more i watch that video it really looks to me like it used the entire length of the runway before finally struggling into the air without enough airspeed to maintain flight, crashing nose-high just seconds later. My impression was very similar: they never had enough thrust for level flight with the gear down, used up the whole runway accelerating to something close to Vr, rotated and started to climb but very soon started slowing and had to reduce the angle of attack, starting the descent. Subjects: None
Tailspin Turtle June 14, 2025, 21:22:00 GMT permalink Post: 11901853	Quote: Originally Posted by MR8 You might want to rethink that. It's approximately 1km glide from where the aircraft was at roughly 200ft, not 2 km. 1km equals about 3000ft, so that is a glide ratio of 15. Taking into account a bit of excess speed to bleed off before reaching alpha max, this sounds very feasible to me. I wondered about that as well. The 787 reportedly has an L/D of 21. Unfortunately, Google didn't provide me with a gear-down L/D (one data set stated landing L/D was 7 but presumably that includes landing flaps as well) but it is clear from some technical reports that it is a non-trivial reduction, maybe 44%. That suggests a gear-down L/D of 12, not taking into account headwind, change of elevation, off-optimum glide speed, etc. Obviously a higher beginning altitude and airspeed and shorter distance to the crash site that stated as well as the benefit of a flare would affect the outcome. However, the difference between an L/D of 16 and 12 given the stated beginning altitude (200 ft) and distance to the crash site (1 km = 3,280 ft) raises the possibility that the engines were still producing some thrust or were coming back on line. Aeronautical engineer, CFI, unused ATP rating, 3,000 hours in airplanes, rotorcraft, and gliders Subjects: None
Tailspin Turtle June 15, 2025, 03:47:00 GMT permalink Post: 11902079	Quote: Originally Posted by appruser IMO In the CCTV video, the aircraft stops climbing at 00:28. 3 seconds after, it starts visibly descending. At peak altitude, using the 197ft wingspan as a measure, the altitude is around 200ft or below. The fireball is at 00:48, 17s after descent starts visibly. Per google maps and the impact location mapped at avherald, the impact point is ~3990ft from the airport boundary road and about 4200ft from the midpoint of the runway threshold and the airport boundary road. 16:1 to 25:1 is what I could find for the 787 glide ratio range (unpowered) with main landing gear down and flaps 5. So the aircraft could cover 16 to 25 ft horizontally for every 1 ft of descent. With a starting altitude of 200ft, that would imply it could have covered 3200ft.to 5000ft during unpowered descent. The actual distance covered, around 4000ft, certainly seems to suggest that the descent was unpowered. Thanks for those numbers. Note, however, the max 787 L/D, flaps and gear up , is reportedly 21 (best in class), which casts shade on the credibility of those L/Ds, certainly 25 with the gear down. What is your source? IF the actual L/D with the gear down and flaps 5 is somewhat lower than 16 and given that starting height and distance traveled are correct\x97and considering that the aircraft might not have been at the speed for max L/D with the gear down and the possibility of a headwind\x97then there must have been some thrust during the descent (it did look to me to be somewhat flatter in that video taken from one side than I would have expected with the gear down, a relatively slow initial speed, and no thrust) or the engines were spooling back up at the end. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AvHerald CCTV
Tailspin Turtle June 17, 2025, 12:46:00 GMT permalink Post: 11904272	Based on approximate distances and heights, the time line, the aircraft configuration, surface wind, the published L/D (gear up reduced to a guess for gear down and RAT out), and probable off-optimum speed for maximum L/D in that configuration, it's my opinion (aeronautical engineer, unused ATP rating, and glider pilot, national contests) that we can't rule out both engines being at idle or very low thrust at or shortly after rotation, rather than shut down. Last edited by Tailspin Turtle; 17th June 2025 at 16:28 . Reason: Added final phrase for clarification Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All)
Tailspin Turtle June 19, 2025, 23:38:00 GMT permalink Post: 11906487	Quote: Originally Posted by MatthiasC172 Can someone help me with the calculations on how far from the point of our last ADS-B readout we can expect the stricken jet to fly/glide? I am assuming the take off mass around 190-200 tons with 50 tons of fuel. For the glide phase this is of no importance, however. Data on the Internet puts the glide ratio of a 789 around 18-21:1. Gear and flaps/slats out should have a significant negative effect. Does anyone have a good take how much? Minus 40%? From the available data we can infer the plane never was higher than 200\x92 AAL, maybe even 100\x92. If I understood the online sources correctly, the point of impact was only about 20\x92 lower than the average runway level. If I am not mistaken the distance from the last ADS-B point to the impact site is about 2 km as per Reuters and the Guardian. That would put it at 6,500\x92. I just can\x92t get these numbers over each other without the aircraft producing thrust. Please help me correcting the numbers. In prior posts, I used approximately the same numbers and came to a similar conclusion (we can't rule out the possibility that there was a least idle thrust available after the loss of thrust), using a guess of a 44% reduction for the configuration from a max L/D of 21. Starting with the height and distance being approximate however, we also don't know what the airspeed/angle of attack was at any point in the descent versus the speed for the maximum (and unknown) L/D for the gear and flaps extended and the RAT out, the amount of headwind, the increase in L/D in ground effect (at a height less than the wingspan) over other than a smooth surface, thermal activity in a urban area, the distance gained in the flare at the end, etc. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB RAT (All)
Tailspin Turtle June 20, 2025, 00:28:00 GMT permalink Post: 11906506	Quote: Originally Posted by Surlybonds Yes, we can. The RAT was deployed, which only happens if both engines are fully shutdown, or the crew manually deployed it. Therefore the crew could have manually deployed it... (there's a button for that). If I saw the engines winding down and couldn't be sure that they would stop at idle, I'd be inclined to deploy the RAT instead of waiting for airplane to do it. Last edited by Tailspin Turtle; 20th June 2025 at 00:53 . Reason: Add a reason for manual deployment of the RAT Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) RAT (Deployment)
Tailspin Turtle June 29, 2025, 19:09:00 GMT permalink Post: 11913181	Quote: Originally Posted by GroundedSpanner Do we think the engines are fully 'off', shutdown - Or are they struggling to provide thrust? Listen to the rooftop video in Capn Bloggs excellent Side-By-Side video . Ignore the RAT. Try and focus on all the sound that is not RAT. I think I can hear a pulsing, a chunk-chunk-chunk' sound. Do we think that is the engines struggling to work? An admittedly approximate assessment of the airplane's lift-over-drag capability, considering other conditions (head wind, ground effect, actual airspeed vs that required to maximize L/D, etc.) suggests that the engines were providing some thrust in order for it to get as far as it did. Note that simple calculations based on conversion of energy, e.g. velocity and height, to distance are even more approximate in this scenario. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All)
Tailspin Turtle June 29, 2025, 22:41:00 GMT permalink Post: 11913278	Quote: Originally Posted by GroundedSpanner Thanks but I want to separate the RAT issue from the engines/thrust issue. Its possible that the RAT was deployed for other reasons, prior to the engines losing thrust. So, leaving the RAT out of the equation for a bit, do we think there is a sound of engines TRYING to run? Also note that either member of the crew can deploy the RAT in addition to the automatic modes, conceivably preemptively in response to the engines losing thrust (full disclosure: at least one poster has insisted than no competent crew would ever do that in those circumstances given the multiple actions with a higher priority to be taken). Others may know if their preferred scenario explaining the simultaneous loss of thrust and automatic RAT deployment could have then resulted in the engines recovering but not soon enough to stop the descent. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) RAT (Deployment)
Tailspin Turtle July 01, 2025, 02:09:00 GMT permalink Post: 11913983	This is my latest attempt to square the circle using all the data points and minimal assumptions. The main shortcoming of the analysis is not knowing the maximum L/D and the speed for maximum LD with the gear down, flaps 5, and the RAT extended. However, if I use a reasonable number in my opinion for the L/D in that configuration and assume that the airplane is being flown at the speed for it, it will not get to the crash site. The distance from the runway of the crash site is from a previous graphic (1.55 km); the rotation point from fdr, permalink 314; 200 feet max height above the runway being generally accepted; crash site 50 feet below the runway elevation cited previously. An average speed of 180 knots is consistent with the dimensions given and 30 seconds flight time. A flare at 50 feet will briefly increase the L/D to 20, maybe even 30 (500 feet more than shown) but still not enough to make up the shortfall, In fact, with a head wind the L/D will be lower than assumed as well as if the speed being flown is higher or lower than required for maximum L/D in that configuration. In other words, there must have been some thrust available. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) RAT (Deployment)
Tailspin Turtle July 01, 2025, 03:33:00 GMT permalink Post: 11914003	Quote: Originally Posted by MaybeItIs Hi TT, Can I ask a question that I guess a few observers will also want to know? Is L/D (Lift-over-Drag?) the same as Glide Slope? I.e. for an L/D of 13, does that equate to 13 forward for 1 down? If so, even at 17, it doesn't look like it would make it. Yes - Higher numbers are better. The 787 has one of the best for an airliner, almost 21 power off. Subjects: None
Tailspin Turtle July 01, 2025, 13:05:00 GMT permalink Post: 11914261	Quote: Originally Posted by nachtmusak There is easily-correctable available data with the aircraft's altitude at pretty much the end of the runway and it is not at 200 feet (it's around 100\xb112.5 feet). As the aircraft visibly continues to climb past that height (and for a longer period than ADS-B data covers, if the camera's perspective casts doubt on that), it seems rather clear to me that it reached its peak height past the end of the runway. In light of this I find the fact that people keep calculating a glide from the runway to the crash site to be a bit strange. Wouldn't the first step of any math be to try to determine where it started descending? Thanks - I'm pretty sure that I read all the posts in both threads but missed that calculation as to the height at the end of the runway. I had originally guessed that the top of climb was 1,000 feet beyond the end of the runway (the current location is based on the referenced statement of the rotation point and an assumed ground speed, not air speed, of 180 kts). That still doesn't get the jet to the crash site, particularly if the post I relied on that it was 50 feet below the runway is incorrect. As far as the benefit of trading speed for distance, there wasn't that much extra speed to start with relative to the likely maximum L/D speed for that configuration and any slowing below it will reduce distance, not increase it, except of course for breaking the glide, i.e. flare at the end (there may have been a little benefit in rounding off the transition from climb to glide that I didn't take into account but I think it was small). My estimate for L/D based on known comparables that didn't include the RAT was actually 12, not 13, and I assumed that they were flying at the max L/D airspeed for that configuration even though it's likely that the crew didn't know what it was (and neither do I) but were following the prime directive, "don't stall". I also didn't take into account the headwind, which would reduce the maximum L/D available and require a slightly faster airspeed to make good than for no wind. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB RAT (All)
Tailspin Turtle July 13, 2025, 23:43:00 GMT permalink Post: 11921782	Quote: Originally Posted by Musician Thank you for your reply! I'm aware you know more about ADS-B than I do, and I'm happy to learn. As you know, I'm referring to the map view and data on https://www.flightradar24.com/blog/f...rom-ahmedabad/ . That's what I thought at first, based on the time stamps. 08:08:50.87 last full ADS-B message (172 kts) 08:08:54 APU inlet door starts to open, per the report. My problem here is that the report also says that the maximum speed was 180 knots IAS at about 08:08:42. And we have 2025-06-12T08:08:46.550875Z,8005ec,23.069138,72.625871,575 associated with 184 kts as the first ADS-B message in the sequence. Given that the clocks of ADS-B receivers are sometimes off, I think this might actually represent the moment of maximum speed; but then the AFS-B clock would be 4 seconds fast. And that's why I adjusted my times. A way to cross-check would be to track the aircraft position over time from the point of rotation, or to use the new photo in the report that shows the RAT over the runway to triangulate where that was. Yes. Would low pressure and high temperature make IAS lower than ground speed, even with the 7 knot headwind? Either way, if they were decelerating at approximately 3 knots per second, then they would've ended up at about 150 knots IAS, which is less than Vr. When I look at the CCTV video, 13 seconds into the flight, the aircraft is just "over the hump" and starts descending, so that tracks. At this point, I don't know what having the engines spool up instead of being dead weight would've done to that flight path; and how successfully the aircraft could've been recovered from that. Maybe they had only 4 seconds to flip those switches, instead of 5 seconds? Still, the best bet is to not ask questions, but flip these switches back ASAP, no? From the beginning, my impression looking at the final glide video was that they weren't sinking as fast as I would have expected with both engines failed completely. A rough analysis using 787 L/D data, revisited as more speed and altitude estimates became available, convinced me that it was very unlikely that they could have gotten that far in that configuration with not only no thrust, but the drag from that big windmilling front fan on each engine. The preliminary report states they got at least one engine turning, apparently fast enough to reduce that drag and therefore get them to the crash site. However, as tdracer opined, a few more seconds would not have allowed for enough thrust to develop to stop the descent before ground contact. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB APU CCTV Engine Failure (All) Engine Shutdown Preliminary Report RAT (All) Timeline (Preliminary Report)

Posts by user "Tailspin Turtle" [Posts: 12 Total up-votes: 0 Pages: 1]