Challenger beyond repair after in-flight upset?
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Second hand info makes it sound even scarier.
The 604 in question had a double engine flameout in the wake along with 5 rolls in its descent of 10000 ft where control was recovered and the engines restarted. RAT did not deploy automatically as it should have either. As it's second hand info I'm waiting to see a report but definitely had some wake scares but nothing in the region.
The 604 in question had a double engine flameout in the wake along with 5 rolls in its descent of 10000 ft where control was recovered and the engines restarted. RAT did not deploy automatically as it should have either. As it's second hand info I'm waiting to see a report but definitely had some wake scares but nothing in the region.
Interesting... can't wait to read actual accounts of this incident.
Do we know if the RAT was deployed manually? Perhaps the RAT did not deploy due to the unusual G forces of the 5 rolls that could have left it stuck in its enclosure.
Do we know if the RAT was deployed manually? Perhaps the RAT did not deploy due to the unusual G forces of the 5 rolls that could have left it stuck in its enclosure.
Which authority will be responsible for preparing a report? I too will be very interested to read this one.
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We always take a deep look outside when something approaches on TCAS, anything bigger than a DC9 we go upwing for a while, have experienced a couple of slight vortex turbulence incidents and no happy with it.
A388 wake turbulence
.... the CL-604 passed 1000 feet below an Airbus A380-800 while enroute over the Arabic Sea, when a short time later (1-2 minutes) the aircraft encountered wake turbulence sending the aircraft in uncontrolled roll turning the aircraft around at least 3 times (possibly even 5 times), both engines flamed out, the Ram Air Turbine could not deploy possibly as result of G-forces and structural stress, the aircraft lost about 10,000 feet until the crew was able to recover the aircraft exercising raw muscle force, restart the engines and divert to Muscat.
Last edited by gearlever; 8th Mar 2017 at 11:53. Reason: typo
Accident: Emirates A388 over Arabic Sea on Jan 7th 2017, wake turbulence sends business jet in uncontrolled descent
That theory is based on their interpretation of ADS-B data which, based on past experience of such analyses by AH, doesn't inspire a great deal of confidence.
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There is a full discussion here: Accident: Emirates A388 over Arabic Sea on Jan 7th 2017, wake turbulence sends business jet in uncontrolled descent
"The Aviation Herald received information that Air Traffic Control all around the globe have recently been instructed to exercise particular care with A380s crossing above other aircraft."
This may be insufficient for safety as it is not really clear how persistent the wake from a 380 actually is. It probably slowly descends and expands. However, for safety it may be necessary for ATC to explicitly apply extra vertical and or lateral separation from the A380's wake with the A380 making the altitude or heading change as it is the reason for the problem. With Free Route Airspace becoming more common the problem may reduce.
"The Aviation Herald received information that Air Traffic Control all around the globe have recently been instructed to exercise particular care with A380s crossing above other aircraft."
This may be insufficient for safety as it is not really clear how persistent the wake from a 380 actually is. It probably slowly descends and expands. However, for safety it may be necessary for ATC to explicitly apply extra vertical and or lateral separation from the A380's wake with the A380 making the altitude or heading change as it is the reason for the problem. With Free Route Airspace becoming more common the problem may reduce.
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The important issue from this AV report:
So the aircraft were flying apart and 1 - 2 minutes later the Challenger was rolled by the wake. That must be 20 - 30 miles behind the 380 and a thousand feet below it the wake was strong enough to roll a bizjet. For those offsetting a couple of miles to avoid wake that may well not be enough with these kinds of figures.
It may also explain the occasional CAT with pax and flight attendants hurt when the flight was otherwise smooth who would suspect an aircraft 30+ miles away?
According to information The Aviation Herald received on March 4th 2017 the CL-604 passed 1000 feet below an Airbus A380-800 while enroute over the Arabic Sea, when a short time later (1-2 minutes) the aircraft encountered wake turbulence sending the aircraft in uncontrolled roll turning the aircraft around at least 3 times (possibly even 5 times)
It may also explain the occasional CAT with pax and flight attendants hurt when the flight was otherwise smooth who would suspect an aircraft 30+ miles away?
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Avherald concedes in its report that the identity of the A380 operator is unconfirmed, and may not have been Emirates at all.
That theory is based on their interpretation of ADS-B data which, based on past experience of such analyses by AH, doesn't inspire a great deal of confidence.
That theory is based on their interpretation of ADS-B data which, based on past experience of such analyses by AH, doesn't inspire a great deal of confidence.
So the aircraft were flying apart and 1 - 2 minutes later the Challenger was rolled by the wake. That must be 20 - 30 miles behind the 380 and a thousand feet below it the wake was strong enough to roll a bizjet. For those offsetting a couple of miles to avoid wake that may well not be enough with these kinds of figures.
The real concern to me is that it has taken two months for this occurrence to be made public, when there could be valuable lessons to learn. Whilst avherald might boldly state that global ATC has been instructed to exercise particular care around A380s, my own ANSP has (at time of writing) offered little in the way of firm guidance.
LTP
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Wake vortices will generally descend at around 2 m/s or 300-500fpm depending on who you ask. They will persist much longer in still air conditions and, as is apparent from this report, conditions of little crosswind (the report states that winds were strong and north-westerly, i.e. directly behind the A380). All things being equal, offsetting by as little as a mile should be enough to avoid wake in more-or-less any conditions. But is this common enough practice?
Accident: Emirates A388 over Arabian Sea on Jan 7th 2017, wake turbulence sends business jet in uncontrolled descent
Rolled at least three times
Challenger a write-off
(I presume due to excessive G load damage).
Rolled at least three times
Challenger a write-off
(I presume due to excessive G load damage).
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...both engines flamed out, the Ram Air Turbine could not deploy possibly as result of G-forces and structural stress, the aircraft lost about 10,000 feet until the crew was able to recover the aircraft exercising raw muscle force...
But maybe the windmilling engines provided enough hydraulics to make the recovery.
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They could have had (or started) the APU and then restarted the engines. IIRC from testing, there is some time before HYD 1 & 2 are depleted (depends on useage of course) and HYD3 is powered by electric pumps. A Challenger or CRJ are best thought of as a FBW aircraft with one channel being pre-stressed Bowden cable! The CF34 does not have sufficient core flow when windmilling to provide ancilliaries but the older Lycoming-powered CL600 I was reliably informed provided sufficient flow to supply hydraulics right to touchdown.
Many years ago I did some work looking at installing a G Load recording system for a Flight Inspection Challenger. The loads routinely experienced at low altitude produce the equivalent of multiple flight hours in airframe life but the Challenger just shrugs them off so I shudder to think what the loads must have been for it to be a writeoff - double figures?
Many years ago I did some work looking at installing a G Load recording system for a Flight Inspection Challenger. The loads routinely experienced at low altitude produce the equivalent of multiple flight hours in airframe life but the Challenger just shrugs them off so I shudder to think what the loads must have been for it to be a writeoff - double figures?
Last edited by ICT_SLB; 10th Mar 2017 at 05:30. Reason: Added windmilling comment
@ ICT SLB...
Yes the Challenger is indeed built like a tank and it must have been a pretty hard upset to have damaged it beyond repair.
Well if the dual engine failure occurred at FL320 or thereafter and the RAT did not deploy automatically or was not deployed manually, I'm afraid they had lost all their hydraulics and AC electrics.
With two engines out, the EDPs on both engines for HYD 1 and HYD 2 would not be able to supply hydraulics to power the flight controls... With a dual engine failure you would have also lost all AC electrics on the aircraft which power all four electric hydraulic pumps, so again no hydraulic power to systems 1-2 and 3 which means no flight controls.
There are two backups to either a dual engine failure or a complete AC electrical failure (lost of the two main AC generators)...
- The first one would be either an automatic or manual deployment of the RAT which would then power the AC essential bus (plus some DC) thus powering the 3B hydraulic pump which would power the flight controls but as we know so far apparently the RAT did not deploy.
- The second one would be that either the APU was already running (doubtful, but not impossible, see note below) which means they had the possibility of using its AC generator to power all the AC busses and hydraulic pumps or that somehow while they were dealing with a dual engine failure and they were rolling the aircraft 5 times out of control and also descending losing 10,000 feet of altitude in the process, someone had the presence of mind to start the APU get the generator on line restoring all the AC and hydraulic pumps.
NOTE: The APU limitation on the 604 is a max altitude of 20,000 feet. Normally it should be shutdown prior to 20,000 feet, usually somewhere in the after takeoff checklist. This said it is well known that crews have forgotten to shutdown the APU and it will run (unloaded) at FL370.
Also Bombardier guarantees a successful start of the APU only up to 20,000 feet. This does not mean someone could not attempt and get a successful start of the APU at 28,000 or even 32,000 feet but I have not heard of such attempts.
Yes the Challenger is indeed built like a tank and it must have been a pretty hard upset to have damaged it beyond repair.
Well if the dual engine failure occurred at FL320 or thereafter and the RAT did not deploy automatically or was not deployed manually, I'm afraid they had lost all their hydraulics and AC electrics.
With two engines out, the EDPs on both engines for HYD 1 and HYD 2 would not be able to supply hydraulics to power the flight controls... With a dual engine failure you would have also lost all AC electrics on the aircraft which power all four electric hydraulic pumps, so again no hydraulic power to systems 1-2 and 3 which means no flight controls.
There are two backups to either a dual engine failure or a complete AC electrical failure (lost of the two main AC generators)...
- The first one would be either an automatic or manual deployment of the RAT which would then power the AC essential bus (plus some DC) thus powering the 3B hydraulic pump which would power the flight controls but as we know so far apparently the RAT did not deploy.
- The second one would be that either the APU was already running (doubtful, but not impossible, see note below) which means they had the possibility of using its AC generator to power all the AC busses and hydraulic pumps or that somehow while they were dealing with a dual engine failure and they were rolling the aircraft 5 times out of control and also descending losing 10,000 feet of altitude in the process, someone had the presence of mind to start the APU get the generator on line restoring all the AC and hydraulic pumps.
NOTE: The APU limitation on the 604 is a max altitude of 20,000 feet. Normally it should be shutdown prior to 20,000 feet, usually somewhere in the after takeoff checklist. This said it is well known that crews have forgotten to shutdown the APU and it will run (unloaded) at FL370.
Also Bombardier guarantees a successful start of the APU only up to 20,000 feet. This does not mean someone could not attempt and get a successful start of the APU at 28,000 or even 32,000 feet but I have not heard of such attempts.
