Interesting information here.
I just find it difficult to accept that in less than a minute, the ice progressively worsened to the extent of bringing the plane down...
Check out this interesting NASA video on tailplane icing/stall.We need more evidence, but I wonder if the aircraft's air data probe was working. Would this have accounted for the aircraft's uncontrolled pitching and rolling? Did the probe freeze over? Was it's heater turned on?
This happened to an aircraft during my time working at NASA's Dryden Flight Research Center. An X-31, on a research flight, under good weather conditions, was lost because the pitot tube heater was not turned on. Flying at an altitude where the air was cold with humidity allowed the probe intake to freeze over. This caused the aircraft's flight control system to essentially be "blinded". The aircraft went into out of control gyrations. The pilot was able to eject. This was on the beginning of approach back to base and like the Dash 8 also it landed in a flat spin.
Check out this interesting NASA video on tailplane icing/stall.
It is very scary how they talk about what happens in their research and what is coming out in this investigation with FLT 3407.
The information in the video is well presented and easily understood by experienced airmen. For those that have mechanical experience but limited flying experience with aircraft, it may be easier to interpret the vast amount of information presented in the video by reading and reviewing the technical / aerodynamic data associated with the NASA/FAA Tailplane Icing Program.
The NTSB has provided limited information obtained from the DFDR in 5 second snapshots. The digital data stream recorded in the NVM of the DFDR can be represented in milliseconds. Presenting flight profile data in 5 second snapshots can be deceiving and lead to a false perception of actual events.
In my opinion and by the limited information provided by the NTSB, on the surface it appears that the initial upset (pitch up 31 degrees) does not fit the known characteristics of a tailplane stall. I’m not stating that it wasn’t a tailplane stall.
I’m interested in knowing the role the autopilot played in trimming the horizontal stabilizer and as a result, masking the pitch down characteristics of an impending tailplane stall. Anyone who has experienced an aerodynamic wing stall understands that the airframe buffet can be felt in the “seat of the pantsâ€. Tailplane stalls can only be felt in the control column. As I understand it, the autopilot was engaged during the approach and landing gear extension didn’t appear to initialize the upset. The upset began when the flaps were positioned to 10 degrees. It’s unclear to me exactly when the autopilot disengaged but appears to have disengaged during flap extension. It’s plausible that the autopilot disengaged when it could no longer compensate from the excessive amount of nose up trim required to counteract the pitch down characteristics of am impending tailplane stall. Could this have resulted in a massive pitch up event? Could PIO have started at this point? I seem to think so.
I have no experience in the Dash 8 and welcome comments from anyone who has.
Excellent analysis Tug.The information in the video is well presented and easily understood by experienced airmen. For those that have mechanical experience but limited flying experience with aircraft, it may be easier to interpret the vast amount of information presented in the video by reading and reviewing the technical / aerodynamic data associated with the NASA/FAA Tailplane Icing Program.
The NTSB has provided limited information obtained from the DFDR in 5 second snapshots. The digital data stream recorded in the NVM of the DFDR can be represented in milliseconds. Presenting flight profile data in 5 second snapshots can be deceiving and lead to a false perception of actual events.
In my opinion and by the limited information provided by the NTSB, on the surface it appears that the initial upset (pitch up 31 degrees) does not fit the known characteristics of a tailplane stall. I’m not stating that it wasn’t a tailplane stall.
I’m interested in knowing the role the autopilot played in trimming the horizontal stabilizer and as a result, masking the pitch down characteristics of an impending tailplane stall. Anyone who has experienced an aerodynamic wing stall understands that the airframe buffet can be felt in the “seat of the pantsâ€. Tailplane stalls can only be felt in the control column. As I understand it, the autopilot was engaged during the approach and landing gear extension didn’t appear to initialize the upset. The upset began when the flaps were positioned to 10 degrees. It’s unclear to me exactly when the autopilot disengaged but appears to have disengaged during flap extension. It’s plausible that the autopilot disengaged when it could no longer compensate from the excessive amount of nose up trim required to counteract the pitch down characteristics of am impending tailplane stall. Could this have resulted in a massive pitch up event? Could PIO have started at this point? I seem to think so.
I have no experience in the Dash 8 and welcome comments from anyone who has.
"A study for the National Transportation Safety Board (NTSB) - the organization that investigates air accidents in the United States - says that its efforts may be hampered by manufacturers, contractors and other third parties who may have a vested interest in avoiding any finding of fault with their aircraft or equipment. The study, by the Rand Institute, observed that the NTSB, the world's largest air accident investigation unit, may be "no match for the opposition of large commercial firms facing large potential losses".The pilot's actions, they said, locked the plane in a stall which caused it to plunge to earth, killing all 49 people aboard and one person on the ground.
link to story
"A study for the National Transportation Safety Board (NTSB) - the organization that investigates air accidents in the United States - says that its efforts may be hampered by manufacturers, contractors and other third parties who may have a vested interest in avoiding any finding of fault with their aircraft or equipment. The study, by the Rand Institute, observed that the NTSB, the world's largest air accident investigation unit, may be "no match for the opposition of large commercial firms facing large potential losses".
"Rand found that in some complex accidents, participants in the investigation "may be acting to further various interests beyond prevention of a similar accident."
Same shift, differnt day.
This blame the pilots scenario was "leaked" out at the earliest stage in an investigation in recent memory, by the NTSB. This is a very disturbing trend of todays NTSB investigators. The intestinal fortitude of the NTSB is matching the trend of the economy, heading south.
In my humble opinion the design of the ATR 72 and Q400 are very similar, the flight characteristics are the breeding grounds of a tail stall.
Please, someone stand up for those that no longer have the luxury.
In my humble opinion the design of the ATR 72 and Q400 are very similar, the flight characteristics are the breeding grounds of a tail stall.