Re: Which redundancy?
Posted: Sun Mar 06, 2016 8:30 pm
[quote author=Colonel Sanders link=topic=2315.msg7172#msg7172 date=1457292170]
Even worse: with all the required redundancy and
backup in the cockpit, you inevitably end up with an
incredibly complicated system that really no one
understands.
Everyone shits on the Asiana 214 crew that took out
the seawall at SFO, but the guy flying it honestly
thought he had auto-throttles - but he didn't because
of the incredible software complexity. Do some research.
[/quote]
I'll agree that modern jets are extremely complicated and system integration isn't transparent. It doesn't help that the manufacturers only gives you limited information about these systems. The philosophy is to give you only enough information to operate the aircraft safely.
With regard to the autothrottle system both Boeing and airbus [b]clearly state[/b] that if the system is not performing adequately it has to be turned off and thrust should be set manually.
Autothrottle mode is clearly annunciated in the top left corner of the PFD (Primary Flight Display). For landing the system must be showing it is in a "Speed" mode. Anything else means something is wrong. When I flew Boeings it was "Manual flight - Manual Thrust". The only time I landed with autothrottle was on a Cat2/3 approach.
I guess times have changed.
Asiana 214
[url=http://www.ntsb.gov/news/events/Pages/2 ... tract.aspx]
http://www.ntsb.gov/news/events/Pages/2 ... tract.aspx[/url]
[quote]
The flight was vectored for a visual approach to runway 28L and intercepted the final approach course about 14 nautical miles (nm) from the threshold at an altitude slightly above the desired 3° glidepath. This set the flight crew up for a straight-in visual approach; however, after the flight crew accepted an air traffic control instruction to maintain 180 knots to 5 nm from the runway, the flight crew mismanaged the airplane’s descent, which resulted in the airplane being well above the desired 3° glidepath when it reached the 5 nm point. The flight crew’s difficulty in managing the airplane’s descent continued as the approach continued. In an attempt to increase the airplane’s descent rate and capture the desired glidepath, the pilot flying (PF) selected an autopilot (A/P) mode (flight level change speed [FLCH SPD]) that instead resulted in the autoflight system initiating a climb because the airplane was below the selected altitude. The PF disconnected the A/P and moved the thrust levers to idle, which caused the autothrottle (A/T) to change to the HOLD mode, a mode in which the A/T does not control airspeed. The PF then pitched the airplane down and increased the descent rate. Neither the PF, the pilot monitoring (PM), nor the observer noted the change in A/T mode to HOLD. As the airplane reached 500 ft above airport elevation, the point at which Asiana’s procedures dictated that the approach must be stabilized, the precision approach path indicator (PAPI) would have shown the flight crew that the airplane was slightly above the desired glidepath. Also, the airspeed, which had been decreasing rapidly, had just reached the proper approach speed of 137 knots. However, the thrust levers were still at idle, and the descent rate was about 1,200 ft per minute, well above the descent rate of about 700 fpm needed to maintain the desired glidepath; these were two indications that the approach was not stabilized. Based on these two indications, the flight crew should have determined that the approach was unstabilized and initiated a go-around, but they did not do so. As the approach continued, it became increasingly unstabilized as the airplane descended below the desired glidepath; the PAPI displayed three and then four red lights, indicating the continuing descent below the glidepath. The decreasing trend in airspeed continued, and about 200 ft, the flight crew became aware of the low airspeed and low path conditions but did not initiate a go-around until the airplane was below 100 ft, at which point the airplane did not have the performance capability to accomplish a go-around. The flight crew’s insufficient monitoring of airspeed indications during the approach resulted from expectancy, increased workload, fatigue, and automation reliance.[/quote]
I can still remember Asiana trying to shift the blame onto Boeing when their own crew didn't follow company procedures. Disgraceful.
The Primary task of the Pilot Flying is to [b]fly the aircraft[/b] and ensure that all parameters remain within the correct limits.
The Primary task of the Pilot Not Flying is to [b]monitor the aircraft flight path[/b] and call any deviations.
Neither of the above happened or this crash wouldn't have happened.
Even worse: with all the required redundancy and
backup in the cockpit, you inevitably end up with an
incredibly complicated system that really no one
understands.
Everyone shits on the Asiana 214 crew that took out
the seawall at SFO, but the guy flying it honestly
thought he had auto-throttles - but he didn't because
of the incredible software complexity. Do some research.
[/quote]
I'll agree that modern jets are extremely complicated and system integration isn't transparent. It doesn't help that the manufacturers only gives you limited information about these systems. The philosophy is to give you only enough information to operate the aircraft safely.
With regard to the autothrottle system both Boeing and airbus [b]clearly state[/b] that if the system is not performing adequately it has to be turned off and thrust should be set manually.
Autothrottle mode is clearly annunciated in the top left corner of the PFD (Primary Flight Display). For landing the system must be showing it is in a "Speed" mode. Anything else means something is wrong. When I flew Boeings it was "Manual flight - Manual Thrust". The only time I landed with autothrottle was on a Cat2/3 approach.
I guess times have changed.
Asiana 214
[url=http://www.ntsb.gov/news/events/Pages/2 ... tract.aspx]
http://www.ntsb.gov/news/events/Pages/2 ... tract.aspx[/url]
[quote]
The flight was vectored for a visual approach to runway 28L and intercepted the final approach course about 14 nautical miles (nm) from the threshold at an altitude slightly above the desired 3° glidepath. This set the flight crew up for a straight-in visual approach; however, after the flight crew accepted an air traffic control instruction to maintain 180 knots to 5 nm from the runway, the flight crew mismanaged the airplane’s descent, which resulted in the airplane being well above the desired 3° glidepath when it reached the 5 nm point. The flight crew’s difficulty in managing the airplane’s descent continued as the approach continued. In an attempt to increase the airplane’s descent rate and capture the desired glidepath, the pilot flying (PF) selected an autopilot (A/P) mode (flight level change speed [FLCH SPD]) that instead resulted in the autoflight system initiating a climb because the airplane was below the selected altitude. The PF disconnected the A/P and moved the thrust levers to idle, which caused the autothrottle (A/T) to change to the HOLD mode, a mode in which the A/T does not control airspeed. The PF then pitched the airplane down and increased the descent rate. Neither the PF, the pilot monitoring (PM), nor the observer noted the change in A/T mode to HOLD. As the airplane reached 500 ft above airport elevation, the point at which Asiana’s procedures dictated that the approach must be stabilized, the precision approach path indicator (PAPI) would have shown the flight crew that the airplane was slightly above the desired glidepath. Also, the airspeed, which had been decreasing rapidly, had just reached the proper approach speed of 137 knots. However, the thrust levers were still at idle, and the descent rate was about 1,200 ft per minute, well above the descent rate of about 700 fpm needed to maintain the desired glidepath; these were two indications that the approach was not stabilized. Based on these two indications, the flight crew should have determined that the approach was unstabilized and initiated a go-around, but they did not do so. As the approach continued, it became increasingly unstabilized as the airplane descended below the desired glidepath; the PAPI displayed three and then four red lights, indicating the continuing descent below the glidepath. The decreasing trend in airspeed continued, and about 200 ft, the flight crew became aware of the low airspeed and low path conditions but did not initiate a go-around until the airplane was below 100 ft, at which point the airplane did not have the performance capability to accomplish a go-around. The flight crew’s insufficient monitoring of airspeed indications during the approach resulted from expectancy, increased workload, fatigue, and automation reliance.[/quote]
I can still remember Asiana trying to shift the blame onto Boeing when their own crew didn't follow company procedures. Disgraceful.
The Primary task of the Pilot Flying is to [b]fly the aircraft[/b] and ensure that all parameters remain within the correct limits.
The Primary task of the Pilot Not Flying is to [b]monitor the aircraft flight path[/b] and call any deviations.
Neither of the above happened or this crash wouldn't have happened.