The windshear you're thinking of is a microburst (Delta 191 anyone?). A phenomenon associated with dying thunderstorms. The fact that the engines didn't respond here is the issue, I don't recall there being any weather in the area from news reports.
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BA B777 short of runway @ LHR
- Thread starter East
- Start date
The windshear you're thinking of is a microburst (Delta 191 anyone?). A phenomenon associated with dying thunderstorms. The fact that the engines didn't respond here is the issue, I don't recall there being any weather in the area from news reports.
No, not a microburst; if there was a low-altitude temperature inversion, just a pocket of warmer air, you could possibly get enough wind shear to take all the lifties off the wings. And it's clear-air turbulence.
Would go a long way to explaining why the sucker just dropped suddenly; everything's cool, then you're losing altitude spiffy fast and coming up on the power doesn't help, even though the engines seem to be good.
Would go a long way to explaining why the sucker just dropped suddenly; everything's cool, then you're losing altitude spiffy fast and coming up on the power doesn't help, even though the engines seem to be good.
You have watched to many of the Navy windshear/microburst videos.. We have Windshear systems in all our A/C, even the 727 which has been held back in the Stone Age, so I can't imagine it ain't on a Triple 7.. And basically, it will detect said windshear and then via Flight Director give guidance to escape and of course there are manual procedures should the FD not be correct.. Also for us we will go into Holding/Divert, if the field is reporting Windshear.. Our Ops manual guidance is to not fly into areas of KNOWN WINDSHEAR.. But FEDEX also does not fly Vref but 5-15 knots higher depending on winds... 5 for 10 kt winds/and then 1/2 reported winds plus all of gust but not more than 15..
WAY too many. The API studs love the part of the video where the T-6 crashes after flying into a microburst on landing, and I got to see that thing every week. Anyway. Like I say, I don't know much about the heavies and their fancy insturments. How does the windshear alert system work? Would it give you enough warning to fly out/away at very low level? I'm curious - I go back to teaching in less than a month (thank Christ) and this would be good class stuff.
YES... It works in close in the SIM and on the line I have never got it lower than about 500 ft... Basically, it starts yelling at you.. "Windshear, Windshear, Pull Up" depending on which A/C and then the Flight Director will give you escape guidance but as soon and you hear the voice, you start executing manual procedures and then transition to the FD.. PM monitoring will give VSI calls and trend calls (climbing/descending)..
Never flown a Boeing. Windshear alert systems combine temp changes and inputs from SCADCs (Air Data) along with AOA etc.
Airbus jets (320's and 330's, don't know about the older ones) have a "feature" called Ground Speed Mini(mum). What it does is keep the jet above a certain ground speed (computed based on weight and current ALT/TEMP/Winds). If you encounter a decreasing performance shear, it will automatically (If AutoThrust is engaged) add power to increase airspeed and maintain ground speed.
It is kind of a pain in the ass, as target airspeed jumps around on gusty days. You can "Turn it off" by taking the computer out of the loop and setting a manual speed.
Huh. Never flown a Bus .....
If you guys want to know how the 18-Wheeler-Whale does it, let me know. In the meantime, since I don't know the Bus systems, I'm takin' a nap. :sleep_125
Mebbe I SHOULD have checked out on the -330 ..... Naaaaaaaaa ....
millerjd
Stayin' alive
Regardless of wind shear, the fact the engine(s) didn't respond is of huge concern to either autopilot or manual.
Found this picture on ProPilot; looks low.. The speculation going on over there is one engine inop and the other working... But who knows till more info comes out...
After flying this week, I realized I misspoke. Ground Speed Mini actually kicks in if you encounter an INCREASING performance shear, to provent you or the AutoThrust from pulling off power, which is what gets you into trouble in a micorburst.
Increasing performance (RHW increases)--->pull power (a lot)---> decreasing performance as RHW dies and then swings to tailwind---->No power on jet, crash.
phrogpilot73
Well-Known Member
I knew I liked you guys for a reason... Boeing is the only way to go!^What he said.
On the 767 with the autothrottles engaged I've had to intervene twice when the airspeed has gone significantly below the selected speed. After being manually prompted the autothrottles came back to life and maintained airspeed. With all the automation being used your scan can become very anemic,ie automation dependency, and the initial resistance to believing that something has gone awry with the normally dependable system can lead one to delay intervention. I've been in the airplane 5+ years and love the Boeing; it's extremely easy to fly but you have to stay in the loop. Of course I'm in the dark about what happened to the 777, while their system is basically the same as ours it is a bit more advanced.
Got this from one of our Union Block reps... And neighbor..
Accident to a Boeing 777-236, G-YMMM, on 17 January 2008 - Initial Report Update
Accident to a Boeing 777-236, G-YMMM, on 17 January 2008 at 1243 hrs
Initial Report Update 23 January 2008
Since the issue of the Air Accidents Investigation Branch (AAIB) 1st Preliminary Report on Friday 18 January 2008 at 1700 hrs, work has continued on all fronts to identify why neither engine responded to throttle lever inputs during the final approach. The 150 tonne aircraft was moved from the threshold of Runway 27L to an airport apron on Sunday evening, allowing the airport to return to normal operations.
The AAIB, sensitive to the needs of the industry including Boeing, Rolls Royce, British Airways and other Boeing 777 operators and crews, is issuing this update to provide such further factual information as is now available.
As previously reported, whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.
Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust.
All possible scenarios that could explain the thrust reduction and continued lack of response of the engines to throttle lever inputs are being examined, in close cooperation with Boeing, Rolls Royce and British Airways. This work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles.
Further factual information will be released as and when available.
http://www.aaib.dft.gov.uk/latest_ne...ort_update.cfm
Accident to a Boeing 777-236, G-YMMM, on 17 January 2008 - Initial Report Update
Accident to a Boeing 777-236, G-YMMM, on 17 January 2008 at 1243 hrs
Initial Report Update 23 January 2008
Since the issue of the Air Accidents Investigation Branch (AAIB) 1st Preliminary Report on Friday 18 January 2008 at 1700 hrs, work has continued on all fronts to identify why neither engine responded to throttle lever inputs during the final approach. The 150 tonne aircraft was moved from the threshold of Runway 27L to an airport apron on Sunday evening, allowing the airport to return to normal operations.
The AAIB, sensitive to the needs of the industry including Boeing, Rolls Royce, British Airways and other Boeing 777 operators and crews, is issuing this update to provide such further factual information as is now available.
As previously reported, whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.
Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust.
All possible scenarios that could explain the thrust reduction and continued lack of response of the engines to throttle lever inputs are being examined, in close cooperation with Boeing, Rolls Royce and British Airways. This work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles.
Further factual information will be released as and when available.
http://www.aaib.dft.gov.uk/latest_ne...ort_update.cfm
