Air France Flight 447 was a scheduled commercial flight from Rio de Janeiro to Paris, that crashed into the Atlantic Ocean on 1 June 2009, killing all 216 passengers and 12 crew members.(Wikipedia)
Looked at the Nova video. The Supercooled water theory seems very doubtful because there is no evidence it has ever happened to any aircraft or to an A330. the only indication of the -20 degrees seems to be the reading on the temp gauge. Good for you for noting it because it went by very quick.
Supercooling can be defeated not only by impurities but by movement. The molecular attractions needed to change the state of the water seem to make ice form at 32 degrees almost regardless of the temperature difference.
Also, water with salt, alcohol or anti-freeze is water that is not pure but sort of exists with lots of impurities at temperatures below zero, contrary to the Nova explanations. It is however correct that ice does not happen in supercooled water.
Wikipedia for supercooled water has some discussion of rain and flying but it seems wrongly worded. They ignore completely the presence of water in the gas state. A side issue for the moment.
Three pitot systems and evidence of past failures is that only two two failed.
There is no “sensor” inside a pitot tube. It’s a differential pressure gauge. No moving parts. It measures two different pressures called the static pressure and the dynamic pressure. There are multiple static systems available so the failures are usually in the dynamic system. There is no evidence offered in the Nova piece that all three systems failed.
Even if all three failed there are other ways for pilots to sense airspeed. The 10 knot range and the five knot range is not fully correct.
The thrust lever theory leaves out alternate methods of controlling airspeed. The easiest one is to simply lower the nose. Every pilot learns very early that going down increases the a/s.
There is also the lack of discussion of the trim wheels that set the attitude of the a/c and are a reliable back up to lessening the pilots workload, especially under emergency conditions.
A wing stall does not happen all at once. The root stalls first and there is no ambiguity about what’s going on. The plane flies fine with a stalled root. There is a reflexive action that when a stall is perceived causes the pilot to simply push the stick foreword. It’s so automatic and ingrained, sort of like a swerve maneuver in a car that it is a reliable substitute for moving the thrust levers or dialing in a different thrust or airspeed.
Presentations like this are one reason I find myself wanting to shout at the TV or the radio when looking at PBS. he political issues are much worse but this video is correct only when it says it’s a mystery. hey say that all the way through while presenting or dramatizing their opposite ideas.
Finally, and far from the issue, — there is a lot of inherent anti-people bias underlying PBS. Sort of like the Michael Moore stuff. They are not alone in this but it’s so prevalent and so easily accepted and it gets reinforced so easy that it’s no mystery why so many people, — fundamentally, — don’t like people.
To continue: …. Also there is a stick shaker that warns of an impending stall in plenty of time to recover.
Flying with a side mounted stick is how every hi-performance fighter jet is flown. Sticks are more intuitive than control wheels.
Flying becomes a matter of sub-conscious instinct developed and honed by habit. It’s very useful, especially during instrument conditions, not too different than driving except pilots are far better trained than car drivers, except for race car drivers …. and they use their sub-conscious to control the car too. The idea that these pilots could not fly well enough or that they lacked some kind of training is a very glaring error on the part of Nova, the SOB’s.
The attitude indicator is an electric gyroscope that makes it very easy to keep the attitude of the aircraft well below a wing stall. Even when a wing fully stalls the aircraft is controllable because the control surfaces are the very last parts of the control system to no longer work. The rudder for example steers the aircraft after the wing stalls during the landing flare. Same for the horizontal stabilizer which works to control the attitude during and after the landing flare maneuver. Happens every time. Controllable, not like the Nova piece which is far more imaginative than factual.
The Air France a/c seems to have landed in a level attitude on the water. If it was stalled it would have hit either nose up or nose down.
Also, Air France pilots have wine with their in-flight meals so they are more relaxed and ready for emergencies.
Anyhow, this covered about 50 reasons the Nova presentation was a lot of non-science, non-logic and non-reason…. not to put too fine a point on it. There is lots more where this came from and lots more to all this but for now it’ll have to do.
The trim wheels lessen pilot workload. They are not so easy to understand and to use well. The 447 video didn’t even mention them because that would nullify their wrong theories that the pilots …. and the flight engineer, … were overloaded and not trained enough.
When a pilot is holding pressure on one of the control surfaces, turning the trim wheel holds the pressure sort of neutralizing the stick forces, and the pilot can do something else.
The trim is set to “take-off trim” before take-off. As the aircraft climbs the pilot uses the elevator to keep the attitude of the a/c somewhat nose up. As the a/c settles down to a rate of climb at a certain prop and throttle setting the pilot uses the elevator to set the airspeed. Non-pilots think the nose has to be raised for the a/c to climb but that’s mostly not correct. The engine setting, i.e., the throttle is used to make the a/c climb.
During climb-out the pilot can turn the elevator trim wheel to take the pressure off the elevator control. It’s sort of like setting the front end alignment on a car while it is going along the road.
One marker of an instrument pilot is their frequent use of the trim settings. They will set elevator and rudder trim constantly during the climb then reset the trim during straight and level flight. Even during straight and level flight the conditions change as the a/c burns off fuel, for example so the trim is set, checked often and reset. Good pilots even re-set trim during the landing flare. “Never stop flying the airplane”.
The way to check the trim is to briefly let go of the controls and watch what happens. If the nose drops slightly, … and a pilot would never let the nose drop enough so the passengers would even sense it, the control wheel is pulled back slightly and some nose-up trim is dialed in. The new setting is checked by letting go of the controls and the sequence continues.
During straight and level the trim is nudged while watching the airspeed. Lowering the nose slightly may give a slightly higher airspeed with no loss of altitude so the pilot is constantly monitoring the instruments and re-setting the trim for elevator, rudder and ailerons along with the RPM, manifold pressure and engine gauges. The trim process becomes almost automatic for pilots.
The adage for an instrument pilot is: “trim is your friend”. The a/c can be highly controlled with trim and the workload is lessened considerably.
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