June 13, 2025, 08:09:00 GMT
permalink Post: 11900142
What the 767s I flew did have, was a hydraulic generator (or 2 in some cases), but that sure ain\x92t a RAT.
June 13, 2025, 14:15:00 GMT
permalink Post: 11900554
Video evidence suggests at least the leading edge devices were extended:
https://youtu.be/oUFS2np0mKc?si=0f1Td6bQiqNOE4U-
https://youtu.be/oUFS2np0mKc?si=0f1Td6bQiqNOE4U-
Only to say, that LE devices seen extended on the crash a/c don't prove configuration on takeoff.
B777/787 rated/current/active pilot.
B787 FCOM:
The slat autogap function is only available in primary mode when the slats are in the middle position and the airspeed is below 225 KIAS. At a high angle of attack, autogap fully extends the slats to increase the wing camber, thus increasing the lift and margin to stall. The slats return to the middle position after the angle of attack decreases. The autogap trip threshold is a function of AOA, airspeed and flap position.
Last edited by T28B; 13th June 2025 at 16:58 . Reason: Formatting assistance
June 13, 2025, 17:21:00 GMT
permalink Post: 11900715
I believe the loud bang that survivor heard was a (BTB) Bus Tie Breaker short.
Based on the comments made by the passenger who travelled on the aircrafts previous sector, speaking about air conditioning that was going on and off, I think a faulty (CAC) Cabin Air Compressors may have contributed.
The B787 FCOM has information about the about only two of four CAC’s being used for ground operation, maybe B787 crew can confirm.
I am curious if the increased electrical demand of the CAC’s shortly after take-off somehow contributed to this potential short.
If such a short did occur then the next question would be how this may influence the engine controls, but given the 248 day AD for electrical issues, it could potentially affect the engines.
I was also surprised to learn that the B787 EICAS actually has a ENG THRUST caution, so not a totally unexplored issue.
Based on the comments made by the passenger who travelled on the aircrafts previous sector, speaking about air conditioning that was going on and off, I think a faulty (CAC) Cabin Air Compressors may have contributed.
The B787 FCOM has information about the about only two of four CAC’s being used for ground operation, maybe B787 crew can confirm.
I am curious if the increased electrical demand of the CAC’s shortly after take-off somehow contributed to this potential short.
If such a short did occur then the next question would be how this may influence the engine controls, but given the 248 day AD for electrical issues, it could potentially affect the engines.
I was also surprised to learn that the B787 EICAS actually has a ENG THRUST caution, so not a totally unexplored issue.
June 13, 2025, 17:28:00 GMT
permalink Post: 11900718
I believe the loud bang that survivor heard was a (BTB) Bus Tie Breaker short.
Based on the comments made by the passenger who travelled on the aircrafts previous sector, speaking about air conditioning that was going on and off, I think a faulty (CAC) Cabin Air Compressors may have contributed.
The B787 FCOM has information about the about only two of four CAC\x92s being used for ground operation, maybe B787 crew can confirm.
I am curious if the increased electrical demand of the CAC\x92s shortly after take-off somehow contributed to this potential short.
If such a short did occur then the next question would be how this may influence the engine controls, but given the 248 day AD for electrical issues, it could potentially affect the engines.
I was also surprised to learn that the B787 EICAS actually has a ENG THRUST caution, so not a totally unexplored issue.
Based on the comments made by the passenger who travelled on the aircrafts previous sector, speaking about air conditioning that was going on and off, I think a faulty (CAC) Cabin Air Compressors may have contributed.
The B787 FCOM has information about the about only two of four CAC\x92s being used for ground operation, maybe B787 crew can confirm.
I am curious if the increased electrical demand of the CAC\x92s shortly after take-off somehow contributed to this potential short.
If such a short did occur then the next question would be how this may influence the engine controls, but given the 248 day AD for electrical issues, it could potentially affect the engines.
I was also surprised to learn that the B787 EICAS actually has a ENG THRUST caution, so not a totally unexplored issue.
2015-09-22: Air compressor failure caused smoke in cabin and diversion for checks. Aircraft diverted to Kolkata for an emergency landing, returned to service same day after air compressor replaced.
June 15, 2025, 08:58:00 GMT
permalink Post: 11902261
So one thing to keep in mind, the RAT can be deployed manually, but also comes automatically when certain conditions arise, everybody here is assuming it\x92s only on dual engine failure but there are 4 more conditions that trigger the RAT,
- all three hydraulic system pressures are low
- loss of all electrical power to the captain and first officers flight instruments
- loss of all four EMP\x92s (electro motor driven pump) and faults in the flight controls system occur during arrival
- loss of all four EMP\x92s and an engine fails during take off.
This all comes directly from B787 FCOM,
If we assume that what our survivor saw is correct, maybe it was an electrical failure, the aircraft had electrical issues in Delhi during departure and I checked the crash video again, I don\x92t see the strobe lights (neither wing or tail) and also no Anti collision light either. this might also explain the self starting APU on loss of the electrics (engine driven generators). That could also result in a loss of situational awareness with the speed, because of no indication, even the HUD would not work. The mayday call would still be doable because the radios work from the battery.
- all three hydraulic system pressures are low
- loss of all electrical power to the captain and first officers flight instruments
- loss of all four EMP\x92s (electro motor driven pump) and faults in the flight controls system occur during arrival
- loss of all four EMP\x92s and an engine fails during take off.
This all comes directly from B787 FCOM,
If we assume that what our survivor saw is correct, maybe it was an electrical failure, the aircraft had electrical issues in Delhi during departure and I checked the crash video again, I don\x92t see the strobe lights (neither wing or tail) and also no Anti collision light either. this might also explain the self starting APU on loss of the electrics (engine driven generators). That could also result in a loss of situational awareness with the speed, because of no indication, even the HUD would not work. The mayday call would still be doable because the radios work from the battery.
June 16, 2025, 06:44:00 GMT
permalink Post: 11903147
Based on the video taken from the left of the flight path, can we determine at what point of the runway rotation occurred? Is there positive confirmation that the takeoff roll started at the beginning of the runway ? Are the two indicative of trouble before rotation, as the Times states ?
Source: https://www.thetimes.com/world/asia/...rash-vhqw6b7v3 (paywalled)
Source: https://www.thetimes.com/world/asia/...rash-vhqw6b7v3 (paywalled)
1250m from the end of the runway, between high speed C and D, adjacent to the closed high speed.
There is nothing unusual with the rate of acceleration that is observable ninth video. You can work that out using google earth and the Indian AIP and/or state airport charts. The weight of the plane can be estimated by the flight time and pax load and an allowance for cargo. The simplified TO performance is in the inflight performance section of the FCOM, which you may find a copy on line.
The aircrafts rotation has no obvious issues, until a few seconds after achieving an attitude that is consistent with the V2+15-25 range, at which point the ROC visibly starts to decay.
June 16, 2025, 06:44:00 GMT
permalink Post: 11903746
Based on the video taken from the left of the flight path, can we determine at what point of the runway rotation occurred? Is there positive confirmation that the takeoff roll started at the beginning of the runway ? Are the two indicative of trouble before rotation, as the Times states ?
Source: https://www.thetimes.com/world/asia/...rash-vhqw6b7v3 (paywalled)
Source: https://www.thetimes.com/world/asia/...rash-vhqw6b7v3 (paywalled)
1250m from the end of the runway, between high speed C and D, adjacent to the closed high speed.
There is nothing unusual with the rate of acceleration that is observable ninth video. You can work that out using google earth and the Indian AIP and/or state airport charts. The weight of the plane can be estimated by the flight time and pax load and an allowance for cargo. The simplified TO performance is in the inflight performance section of the FCOM, which you may find a copy on line.
The aircrafts rotation has no obvious issues, until a few seconds after achieving an attitude that is consistent with the V2+15-25 range, at which point the ROC visibly starts to decay.
June 17, 2025, 15:25:00 GMT
permalink Post: 11904394
RAT powered systems
There’s been some debate over what electrical and hydraulic systems are powered. According to one unauthorized and Not For Flight -labeled FCOM copy that seems quite authentic:
The list of inoperative systems include most/all secondary fligh controls powered by the center hydraulic system. There we can conclude that centre hydraulic system electric pumps are not available when operating on
APU
RAT (or battery) only electrical mode.
“In-Air Rat Only Operation” mode (Standby Power) – If loss of all electrical power to captain’s and first officer’s flight instruments occurs in flight, the RAT energizes the captain’s flight instruments and other essential equipment for flight controls, navigation, and communication. The main battery provides standby power until RAT deployment. Significant loads energized by this mode include:
captain’s inboard DU
• captain’s outboard DU
• lower DU
• autoflight system
• MCP
• autopilot
• captain’s / first officer’s ACP
• captain’s / first officer’s
flight interphone
• VHF L
• TCP L
• DSP L
• MFK L
• CCD L
• IRU L, R
• AHRU L, R
• INR L, R
• ISFD
• FMC
• PFC
• CCR L
• center pitot heat
• engine/APU fire detection
• miscellaneous lightin
Note: Autothrottle, flaps, slats, stabilizer, thrust reversers, auto speedbrakes, air conditioning / pressurization, Head-Up displays, HF radios, SATCOM systems, external lighting, WIPS, and window heat are inoperative on standby power.
“In-Air Battery Only” mode (Standby Power) –
This mode energizes the same
equipment as the “In-Air RAT Operation Only” mode with the exception of center
pitot heat.
captain’s inboard DU
• captain’s outboard DU
• lower DU
• autoflight system
• MCP
• autopilot
• captain’s / first officer’s ACP
• captain’s / first officer’s
flight interphone
• VHF L
• TCP L
• DSP L
• MFK L
• CCD L
• IRU L, R
• AHRU L, R
• INR L, R
• ISFD
• FMC
• PFC
• CCR L
• center pitot heat
• engine/APU fire detection
• miscellaneous lightin
Note: Autothrottle, flaps, slats, stabilizer, thrust reversers, auto speedbrakes, air conditioning / pressurization, Head-Up displays, HF radios, SATCOM systems, external lighting, WIPS, and window heat are inoperative on standby power.
“In-Air Battery Only” mode (Standby Power) –
This mode energizes the same
equipment as the “In-Air RAT Operation Only” mode with the exception of center
pitot heat.
Last edited by Senior Pilot; 17th June 2025 at 21:44 . Reason: Remove false information
June 17, 2025, 17:15:00 GMT
permalink Post: 11904482
I agree. You'll note that I left the quoted post being objected to in the answering post; people can still take a look at the speculation therein.
How many of us, over the years, have seen a case of 'fast hands', and had to catch it, or correct it before things went pear shaped?
I don't think anyone intends to do that.
I felt that the (valid) objection was to the problem of stating as a fact that which is an estimate or a guess.
How many of us, over the years, have seen a case of 'fast hands', and had to catch it, or correct it before things went pear shaped?
I don't think anyone intends to do that.
I felt that the (valid) objection was to the problem of stating as a fact that which is an estimate or a guess.
I certainly am not advocating excluding crew actions from consideration but I am saying that uninformed rank speculation on that particular topic has much more potential to be harmful to actual people. PPRUNE is widely read by news outlets and Youtube pontificators. Give them a "credible" reason and they'll be digging into the personal lives of the crew in ways that none of us would like. If you want to ask "what would happen if the captain just switched off both engines at rotation?" then I suppose the answer might be that the result would be pretty much exactly what happened here. But I think it is a bad idea to go there so soon and without evidence, especially since we're likely to have more evidence soon.
Last edited by BrogulT; 17th June 2025 at 17:16 . Reason: typos
June 17, 2025, 21:31:00 GMT
permalink Post: 11904684
Short answer is yes but IIRC from the 777 (believe the 78 to be similar) the auto throttles go into SPD mode at that point which could be really confusing. As one goes up through the MCP altitude and the FD commands a descent.
In any case the autopilot wouldn\x92t have been in at such a low altitude and the PF would have been hand flying. Most of the min engagement altitudes for autopilots is 400\x92 AGL.
But again all of this is speculation in every way.
In any case the autopilot wouldn\x92t have been in at such a low altitude and the PF would have been hand flying. Most of the min engagement altitudes for autopilots is 400\x92 AGL.
But again all of this is speculation in every way.
As mentioned elsewhere both EK and Air NZ have had messy low level mis-set altitude capture incidents with the B777, but in isolation, obviously, this wouldn't cause RAT extension.
About airport cameras. Someone pointed out on the other thread that airports have more coverage than they would necessarily advertise. Presumably available to investigators but not to the public or press.
June 17, 2025, 21:37:00 GMT
permalink Post: 11904691
Most? The Airbus I'm familiar with is 100' AGL or 5s after liftoff and I think this is common to all Airbus FBW. The B787 & B777 appear to be 200' AGL but I'm taking this from online FCOM extracts. The
B737
does appear to be 400'. Company limitations may be higher.
As mentioned elsewhere both EK and Air NZ have had messy low level mis-set altitude capture incidents with the B777, but in isolation, obviously, this wouldn't cause RAT extension.
About airport cameras. Someone pointed out on the other thread that airports have more coverage than they would necessarily advertise. Presumably available to investigators but not to the public or press.
As mentioned elsewhere both EK and Air NZ have had messy low level mis-set altitude capture incidents with the B777, but in isolation, obviously, this wouldn't cause RAT extension.
About airport cameras. Someone pointed out on the other thread that airports have more coverage than they would necessarily advertise. Presumably available to investigators but not to the public or press.
Yes yes back into my box.
June 17, 2025, 22:42:00 GMT
permalink Post: 11904730
Most? The Airbus I'm familiar with is 100' AGL or 5s after liftoff and I think this is common to all Airbus FBW. The B787 & B777 appear to be 200' AGL but I'm taking this from online FCOM extracts. The
B737
does appear to be 400'. Company limitations may be higher.
As mentioned elsewhere both EK and Air NZ have had messy low level mis-set altitude capture incidents with the B777, but in isolation, obviously, this wouldn't cause RAT extension.
About airport cameras. Someone pointed out on the other thread that airports have more coverage than they would necessarily advertise. Presumably available to investigators but not to the public or press.
As mentioned elsewhere both EK and Air NZ have had messy low level mis-set altitude capture incidents with the B777, but in isolation, obviously, this wouldn't cause RAT extension.
About airport cameras. Someone pointed out on the other thread that airports have more coverage than they would necessarily advertise. Presumably available to investigators but not to the public or press.
yeah the low MCP alt setting/alt capture doesn\x92t make a whole lot of sense- the plane didn\x92t pitch forward it just failed to climb/lost lift
that\x92s not conducive with what happened nor does it explain why the gear is still down (although seemingly selected up given the boogie tilt) or the RAT deployed (if it really was)
June 18, 2025, 08:46:00 GMT
permalink Post: 11905031
Most? The Airbus I'm familiar with is 100' AGL or 5s after liftoff and I think this is common to all Airbus FBW. The B787 & B777 appear to be 200' AGL but I'm taking this from online FCOM extracts. The
B737
does appear to be 400'. Company limitations may be higher.
As mentioned elsewhere both EK and Air NZ have had messy low level mis-set altitude capture incidents with the B777, but in isolation, obviously, this wouldn't cause RAT extension.
About airport cameras. Someone pointed out on the other thread that airports have more coverage than they would necessarily advertise. Presumably available to investigators but not to the public or press.
As mentioned elsewhere both EK and Air NZ have had messy low level mis-set altitude capture incidents with the B777, but in isolation, obviously, this wouldn't cause RAT extension.
About airport cameras. Someone pointed out on the other thread that airports have more coverage than they would necessarily advertise. Presumably available to investigators but not to the public or press.
The ideas of mis-set MCP, AT modes, etc. were worth exploring but by this point, like the gear/flap/performance ones, there is enough convincing evidence now that a) the takeoff was normal until it suddenly wasn\x92t and b) none of the above would cause RAT deployment and a glide into the ground.
June 18, 2025, 09:17:00 GMT
permalink Post: 11905048
I think the minimum autopilot engagement height is a FCOM limitation but not necessarily a limitation of the system, i.e. you can engage the AP lower than that but it hasn\x92t been technically qualified to work in all circumstances, although it might actually do that..
June 18, 2025, 12:13:00 GMT
permalink Post: 11905186
Hi all,
Disclaimer: I read this thread from hour 1, still scratching my head regarding perf though.
I know sound analysis points to higher odds being a dual engine failure with RAT deployed, however I still have some questions if anyone is available to enlighten.
So, my questions is related to T/O performance.
Is it possible on the 787 to calculate perf in the OPT for F15/20 T/O, and to enter F5 T/O speed on the FMC ?
By that I mean do normal procedure, but at the point where you are suppose to enter flaps, CG speed ect\x85. You, out of habit (if F5 is indeed a habit on the 787) enter F5, but F15/20 speeds ? Or would there be a warning that you have manually inputed speeds that are not correct for the selected flaps and conditions inputed in the FMC ?
Thanks for the help !
Disclaimer: I read this thread from hour 1, still scratching my head regarding perf though.
I know sound analysis points to higher odds being a dual engine failure with RAT deployed, however I still have some questions if anyone is available to enlighten.
So, my questions is related to T/O performance.
Is it possible on the 787 to calculate perf in the OPT for F15/20 T/O, and to enter F5 T/O speed on the FMC ?
By that I mean do normal procedure, but at the point where you are suppose to enter flaps, CG speed ect\x85. You, out of habit (if F5 is indeed a habit on the 787) enter F5, but F15/20 speeds ? Or would there be a warning that you have manually inputed speeds that are not correct for the selected flaps and conditions inputed in the FMC ?
Thanks for the help !
June 18, 2025, 12:26:00 GMT
permalink Post: 11905199
I think this has been answered for 76 and 77 on the first thread but I can\x92t recall an answer for 78.
Can anyone confirm if you have inputed F15 in the FMC but selected F5 you would have some sort of FMC message displayed ?
June 18, 2025, 13:08:00 GMT
permalink Post: 11905228
I (and I think everyone else here) have been assuming that the FADEC does in fact have a dedicated permanent-magnet alternator, as is the case on the Airbuses (confirmed by FCOM) and surely the 737.
I have been told elsewhere that this is not the case. A read of the draft FCOM available online for the 777 & 787 makes no mention of a FADEC generator, but then neither does the 737 manuals. Is this simply a case of "Boeing thinks you don't need to know"?
It has been proposed that the primary source of power for the FADECs is actually the flight control PMGs, mounted on the engine gearbox, but that this power goes to the avionics bay, has failover switching gear, and comes back to the EEC.
Can anyone shed concrete light on this (e.g. a source that clearly states there is both an EEC alternator and a flight control PMG on the accessory gearbox)?
Alternator and generator seem to be used interchangeably in this context.
It's not quite that, but there is a
list of received channels for a GEnx 787 in the
FDR report into one of the original battery fires
.
Unfortunately, it is only a list of parameters that they used and verified in the investigation - the only ones listed for the engines are N1 and cutoff switch. Other accident/incident FDR reports might be more focused on engines and include a similar table.
I don't think you'll find an actual wire list for it (or it won't be useful) as apparently most/all of the data is via an ARINC bus.
I attempted to PM this but your inbox is full.
[SLF with an electrical background and some exposure to ground-side critical facilities power]
I have been told elsewhere that this is not the case. A read of the draft FCOM available online for the 777 & 787 makes no mention of a FADEC generator, but then neither does the 737 manuals. Is this simply a case of "Boeing thinks you don't need to know"?
It has been proposed that the primary source of power for the FADECs is actually the flight control PMGs, mounted on the engine gearbox, but that this power goes to the avionics bay, has failover switching gear, and comes back to the EEC.
Can anyone shed concrete light on this (e.g. a source that clearly states there is both an EEC alternator and a flight control PMG on the accessory gearbox)?
Alternator and generator seem to be used interchangeably in this context.
I don't think you'll find an actual wire list for it (or it won't be useful) as apparently most/all of the data is via an ARINC bus.
I attempted to PM this but your inbox is full.
[SLF with an electrical background and some exposure to ground-side critical facilities power]
Last edited by Someone Somewhere; 18th June 2025 at 13:32 .
June 18, 2025, 13:22:00 GMT
permalink Post: 11905242
I (and I think everyone else here) have been assuming that the FADEC does in fact have a dedicated permanent-magnet alternator, as is the case on the Airbuses (confirmed by FCOM) and surely the 737.
I have been told elsewhere that this is not the case. A read of the draft FCOM available online for the 777 & 787 makes no mention of a FADEC generator, but then neither does the 737 manuals. Is this simply a case of "Boeing thinks you don't need to know"?
It has been proposed that the primary source of power for the FADECs is actually the flight control PMGs, mounted on the engine gearbox, but that this power goes to the avionics bay, has failover switching gear, and comes back to the EEC.
Can anyone shed concrete light on this (e.g. a source that clearly states there is both an EEC alternator and a flight control PMG on the accessory gearbox)?
Alternator and generator seem to be used interchangeably in this context.
It's not quite that, but there is a list of received channels for a GEnx 787 in the FDR report into one of the original battery fires .
I don't think you'll find an actual wire list for it (or it won't be useful) as apparently most/all of the data is via an ARINC bus.
I attempted to PM this but your inbox is full.
[SLF with an electrical background and some exposure to ground-side critical facilities power]
I have been told elsewhere that this is not the case. A read of the draft FCOM available online for the 777 & 787 makes no mention of a FADEC generator, but then neither does the 737 manuals. Is this simply a case of "Boeing thinks you don't need to know"?
It has been proposed that the primary source of power for the FADECs is actually the flight control PMGs, mounted on the engine gearbox, but that this power goes to the avionics bay, has failover switching gear, and comes back to the EEC.
Can anyone shed concrete light on this (e.g. a source that clearly states there is both an EEC alternator and a flight control PMG on the accessory gearbox)?
Alternator and generator seem to be used interchangeably in this context.
It's not quite that, but there is a list of received channels for a GEnx 787 in the FDR report into one of the original battery fires .
I don't think you'll find an actual wire list for it (or it won't be useful) as apparently most/all of the data is via an ARINC bus.
I attempted to PM this but your inbox is full.
[SLF with an electrical background and some exposure to ground-side critical facilities power]
(h) Aircraft Supplied Electrical Power.
(1) The Engine Control System must be designed so that the loss or interruption of electrical power supplied from the aircraft to the Engine Control System will not -
(i) Result in a Hazardous Engine Effect,
(ii) Cause the unacceptable transmission of erroneous data.
The effect of the loss or interruption of aircraft supplied electrical power must be taken into account in complying with CS-E 50(c)(1).
(1) The Engine Control System must be designed so that the loss or interruption of electrical power supplied from the aircraft to the Engine Control System will not -
(i) Result in a Hazardous Engine Effect,
(ii) Cause the unacceptable transmission of erroneous data.
The effect of the loss or interruption of aircraft supplied electrical power must be taken into account in complying with CS-E 50(c)(1).
June 18, 2025, 13:23:00 GMT
permalink Post: 11905243
- Each engine has a PMG for the FADECs
- Only for engine start the FADECs are powered by the aircraft
- Once the engines are running, this connection is opened
- It is verified, that the FADECs are then no longer connected to the aircraft electrical system. A failure to open the connection triggers a "No dispatch" message
- In case the PMG fails, the FADECs are once again powered by the aircraft electrical system
June 19, 2025, 10:22:00 GMT
permalink Post: 11905892
Originally Posted by
DTA
That failure can be the result of physical damage or wear so that the knob is stuck in the pulled position. It would not be obvious if you did not look closely.
