On most modern aircraft, airspeed is one sensor input that is used to derive signals to limit the available movement range of flight controls. For example since the group is currently discussing the rudder, airspeed is used along with other signals to cause the rudder maximum available deflection to decrease significantly as airspeed increases.
I am not an Airbus expert nor am I a flight controls expert so I cannot say for sure how Airbus does this. I cannot even state with certainty what type of relationship is there (linear, non-linear, etc) except I know the relationship between airspeed and available rudder travel is inversely proportional.
The point is since both pitot tubes (and thus airspeed) and the rudder appear to be players in this accident (note I said appear, I am not qualified to second guess the investigating agencies) perhaps the two systems are related in their involvement. Erroneous airspeed information could have allowed larger than desired rudder excursions, and the storm could have provided very large yawing forces that the yaw damper attempted to dampen, possibly exceeding designed-for aerodynamic forces on the vertical tail.
The above is pure speculation on my part of course. But I remember reading about very early KC-135 operations in the USAF where pilots would attempt to manually dampen the natural dutch roll the aircraft had, and if they got behind the aircraft and moved the rudder incorrectly at the wrong moment, supposedly the outboard engine on one of the wings would break away from the aircraft. (Is this urban legend or does someone out there know this to be fact?) I heard it from a retired Lieutenant Colonel for whom I worked years ago.
I think it might be more accurately a case of barreling along in a car at 100 MPH and rotating the steering wheel to one side as fast as possible.
I'm not saying I necessarly agree with Airbus design decisions. The trade press carried some very insightful pilot comments back when the AA crash occured.
I don't think it's really related to the Air France aircraft though.
Also related to the the significance of the Air Data System and airspeed, in my own experience as a rookie student pilot, I've learned about V sub a = manuvering speed.
This is the speed you must slow to in heavy turbulence to avoid structural damage. At Va the wing stalls (aerodynamically) before heavy turbulence can cause structural damage, but it is fast enough to stay flying.
I KNEW someone would shoot holes through my analogy...
Even at that, you don't expect the wheels to fall off immediately; you might flip the car half a dozen times, but more often than not, the wheels don't come off from the original FUBAR, but from the subsequent impacts with the ground.
Supposedly, it's still possible to steer a plane without a rudder or fin, but it's extremely difficult:
Interesting article on the B-52 that lost it's Vertical Stabilizer over the mountains due to severe gusts, in the 1960's... Static stability was barely maintained in this instance. Apparently, other BUFFS fared worse in WX related mishaps.
You would need to fill the entire plane with dye to make a dent in the middle of the Atlantic...
We did discuss the possibility of a deployable FDR, that would float on the surface for just such an occasion.
As for the ultrasonic microphones, it's not just the quantity, but also the depth. The wreckage is ostensibly at the limit of the transmission depth of the ULBs, so you need to have submerged receivers. Additionally, there's no guarantee that the FDRs or the ULBs didn't get so badly damaged from the crash or the subsequent submergence to 4000m depth that they ceased operation. Or, that the wreckage didn't get so buried in silt that the transmission strength was grossly attenuated.
I think I read that they found the fuel anyway. Apparently it didn’t help them locate the wreckage. A mid Atlantic storm with high seas is a tough environment.
I know older Emergency Locator Beacons were bouy like affairs. I believe we just passed some sort of regulatory deadline to migrate to GPS - satellite ELBs too.
Unfortunately, it may still be strapped to a piece of cockpit bulkhead someplace at the bottom of the ocean.
I kind of wonder how much passenger Personal Electronic Device (PEDs) gear is still actively running that might have an EM signature. Of course with FCC abd CE emissions controls, it would be a small signature too.
How about a timed release of something like boyant packing popcorn with embeded RFID chips, possibly designed for easy detection when activated by a radar signal. I read a lot about military ground surveillance radar.
It's well beyond me to visualize the working details, but it seems like it could be made to work. RFID applications seem to extend well beyond the L band.
The missing point is that the FDRs already have RF beacons, so if they were on the surface, we would have found them by now. The issue is that the FDRs are usually buried somewhere in the tail for protection, so getting them deployed after a water impact is the primary issue, hence the discussion about a possible redundant FDR specifically for deployment after a water impact.
This FDR would have to be near, or on, the exterior skin of the airplane, and be jettisoned far enough away from the airplane so that it can float clear of the wreckage to reach the surface. The fact that so few bodies have been found, particularly with the hypothesized mid-air breakup of the plane, shows the difficulty in getting something from inside the plane to get clear of the wreckage.
I've seen and installed all of the emergency gear that goes in modern aircraft. I also supported the shops that repaired the gear we’re talking about for a couple years. It seems to me that the principle behind some of hasn’t really changed much with technology.
Spending millions dollars sweeping the ocean for a pinger, about the size of 2 D-cell batteries seems like an expensive proposition. I guess it has a good track record, but what was the cost to find them?
My first idea was a dye pack. That’s probably WWII era thinking. Then I thought about radar detection and floating chaff.
Then I began to wonder what you could intentionally do to a radar return with RFID.
Apparently RFID is inexpensive enough it can be embedded in baggage tags (I saw the prototypes), grocery labels, etc. So I thought maybe they could be embedded in small floating foam objects by the 1000s and placed in various locations within the aircraft structure. Maybe they could be packaged into solid blocks that de-bond or release themselves from within the aircraft structure if the it’s cracked open and submerged.
With luck something like this could be developed to require no maintenance beyond keeping it dry.
I’m not involved with radar development, but I am aware that signal processing in modern radars goes far beyond finding something large like a ship or aircraft.
Detection range may be the issue for something like a door prox card. Still it might be possible to develop devices designed to be detected by powerful radar. With the right signature and signal processing maybe a RFID device signal return could be tailored to bloom on a radar screen.
I wrapped up a project to equip a fleet of airplanes with predictive windshear weather radar at my last job. This system essentially detected water droplets moving sideways instead of down. I can only imagine what the military has going on with Synthetic Aperture Radar and ground surveillance. I understood a radar that gave you any sort of decent return from a ground sweep was something of a breakthrough.
To change the subject,
It also amazes me that we've been talking and developing and fielding ADS-B (Automatic Dependent Surveillance – Broadcast ) on 1090 Mhz for ATC (Air Traffic Control) surveillance in major regions across the globe as independent project’s for the better part of the last decade. No one I’ve heard has ever suggested we should be developing a satellite ATC surveillance system that would work over the oceans. The only open water coverage I’ve heard of involves putting ADS-B receivers on oil rigs.
ADS-B is where the aircraft regularly transmits it’s ID, GPS based position, velocity, altitude, heading etc. as a replacement for determining an aircraft’s position using ground radar and altitude reporting.
One of the reason we don't know where 447 was or it's speed and direction is because the routine ACARS messages were transmitted about once every 10 min (Aviation Week).
I’m also still not clear why they couldn’t avoid the storm front. The airplane certainly had weather radar.
I’m sure it will all unfold as the investigators dig into it.
From what I have seen... Airbus needs to consider placing the CVR & FDR... or miniaturized secondary version containing the essence of both [lets-say 30-minutes worth of data for each]... in the middle of the vertical stabilizer.
That-way when the stab fails, and gently flops to the ground or into the water, essential data is easily recovered...
I had to resurrect this thread to share this news story about a "streaming black box" going to flight test phase. Looks like it uses the existing Iridium system.
Not sure if the original question was answered, but do a search on "TSO-C155". Will show FAA Technical Standard Order for Recorder Independent Power Supply. Power back-up source is now required to allow recorder to continue operating should acft power be lost. It's either a separate unit adjacent to the recorder or built-in.
