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Old 26th Apr 2011, 21:37   #161 (permalink)
 
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Hmm would a colour camera/lighting system be of any use in that depth/darkness? Talk about the proverbial needle in the haystack.
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Old 26th Apr 2011, 21:44   #162 (permalink)
 
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Slats11, your comment about education and FBW resonates with me when I translate it to terms with which I am intimately familiar.

I to some degree liken FBW to a new radio coming out that links several controls into three or four push button settings. Unless you know what those settings really amount to in terms of the old controls and understand the old controls you cannot wring the maximum out of the radio. Radio manufacturers stepped back a little and more or less gave access to the old controls within the context of the buttons. Newer high end radios have wider selections of filters. And the filters can be tuned, which can substitute for the tricks you used to do with the old controls. But, if you never learned the old controls it still seems to be difficult to extract the best out of the radios.

Looking at FBW in aircraft, unless the pilot knows how to fly the plane to the edges of its envelop without computer interference and unless the pilot knows precisely what steps the computer took before it "gives up" and hands control back to the pilot, it may be hard to recover as the pilot goes back over ground the AP already covered.

I don't know if this is a clear explanation. The extractable information is that I've found computer aiding is helpful; but, you must know intimately what it is doing and has done if you need to wring that last critical bit of (life saving?) performance out of the machinery.

Is there this level of knowledge among the flight crews today?
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Old 26th Apr 2011, 23:01   #163 (permalink)
 
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Graybeard and ChristianJ - thanks for reminding me of the slot antenna. In '68 they were still under development as dielectric loaded slots by one of my professors at Univ of Mich. I'd had the impression they were basically designed for VHF at the time.

You got me looking. It's apparently a vertical slot on the lower portion of the VS structure. That would be slightly lower efficiency. But, it doesn't much matter. Communications to DAKAR are possible. And at 6.6 MHz even that antenna would be noisier than any (sane) radio connected to it. This reception is not antenna limited. The pattern might be a problem. I'd expect that always to be a problem rather than specific to AF447's situation. (Does anybody know of a good picture of the antenna unmounted from the aircraft? I'm curious precisely how it is constructed. It's not what I grew up calling a slot antenna. But, with the one picture I have of it, there's not a much better short name for it.)

And finally it bears no importance to the AF447 situation because DAKAR did not have the plane in its list of planes to listen for and Brazil never tried using SelCal when calling the plane. The lack of communications was procedural rather than somehow related to an antenna that doesn't work well.

ChristianJ, those gray patches don't look like the diagrams I have managed to find.
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Old 26th Apr 2011, 23:23   #164 (permalink)
 
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Re: Yes: Airbus submits patent for airspeed error monitoring

Fascinating - for those only worrying about US patents, there is ample prior art in discussion here on PPRuNe to get the patent tossed out.
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Old 26th Apr 2011, 23:43   #165 (permalink)
 
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Quote:
Originally Posted by JD-EE View Post
Graybeard and ChristianJ - thanks for reminding me of the slot antenna. In '68 they were still under development as dielectric loaded slots by one of my professors at Univ of Mich. I'd had the impression they were basically designed for VHF at the time.
I first came across slot antennas in my early 'radar' days, and that was SHF, and far earlier than '68.

Quote:
Does anybody know of a good picture of the antenna unmounted from the aircraft? I'm curious precisely how it is constructed. It's not what I grew up calling a slot antenna. But, with the one picture I have of it, there's not a much better short name for it.
I'd be interested too, both in seeing your picture, and any others that somebody might have.

Quote:
ChristianJ, those gray patches don't look like the diagrams I have managed to find.
They were more green than gray... I doubt that the slots were 'dielectric loaded'. I think you're just looking at the honeycomb fibreglass covers of the two "sawcut" cavities.

This all being slightly irrelevant to AF447, maybe us 'radio geeks' should open a separate Tech Log thread about HF aerials on airliners?
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Old 27th Apr 2011, 00:13   #166 (permalink)
 
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Quote:
Originally Posted by Chris Scott
Perhaps HN39 might be able to provide a graph of level-flight AoA versus load-factor, please?
Sure, here it is: LF vs AoA

PS: Same data in different format were posted 31st jan 2011, Post #2663 on the previous thread: A330_gustloads
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Old 27th Apr 2011, 01:07   #167 (permalink)
 
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Quote:
Originally Posted by glad rag
Hmm would a colour camera/lighting system be of any use in that depth/darkness?
It's not so much the depth and darkness as the basic properties of water. Water absorbs (or scatters, or both) light at the red end of the visible spectrum, and to a lesser extent at the blue end. This leaves a transmission peak for green light, with the overall effect that color pictures, of sunlit scenes, taken at depths of more than a few meters have a strong blue-green tone. (I suppose modern CCD cameras may be able to color correct that to some extent.) This effect is modified by the presence of other things in the water, such as algae and plankton at temperate and polar latitudes. In the tropics, ocean water, viewed from above, looks very blue due to scattering, I think, and is often nearly free of marine organisms. Deep sea water is usually very clear, also.

Electromagnetic absorption by water - Wikipedia, the free encyclopedia

So, in answer to the question, deep sea photos require artificial light, as all sun light has been absorbed. That light is often white, as is the xenon strobe on the REMUS 6000 vehicle, or it could be green (thallium-iodide arc lamp, green LEDs, etc.) to take advantage of the transmission peak and scattering minimum. When photos are taken at close range (both the light and camera close to the subject), as is generally the case for ROV and manned submersible work, color cameras are normally used and the colors look natural, or close to it. When the range is greater, the light that travels from the source to the subject and back to the camera becomes so dominated by blue-green that a color camera adds very little. Furthermore, a B&W camera is usually more sensitive (works with lower light) than a color camera using similar technology, so operation from greater range is enhanced. Modern CCDs have become very sensitive, but in the earlier days of underwater video imaging, intensified cameras were sometimes used, and the intensifier was applied to a monochrome camera.

REMUS would fly at 5-20m (typically 10m) above the bottom for photo work, depending on water clarity and height of possible obstructions. The two-way path length is thus quite long and there is little usable color. If any ROV images or video are released, they are likely to be in color.

The ultimate range of underwater imaging is usually limited by back-scatter from the water and the particles in it, which fogs the image. That is a large topic, not related to the question, but I thought I should mention it.

As a side note, I expect that the visible spectrum (spectrum of light visible to humans) is so narrow, being less than one octave from about 400-700nm, exactly because of the absorption properties of water. Either because our retinas are sensitive to the light that gets through our water-filled eyes, or possibly because the type of eyes we have evolved in water dwelling lifeforms. There is probably known science on this, I'm just not familiar with it.
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Old 27th Apr 2011, 01:22   #168 (permalink)
 
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I suppose I opened a bit of a hornets' nest with my comments regarding RF communications by AF447.

I'm a radio amateur and not a radio professional so my observations are based on empiricism but I believe that electromagnetic propagation is still a poorly understood science (not only by me) and at times will not conform to engineering specifications.

My object was to point out the perversity of inanimate objects such as non-vacuum electromagnetic propagation media (and in previous comments - computer software) as observed by Major Edward Murphy and published by his colleague Col. John Strapp M.D. who understood the medical maxim: never say that something never happens or that something always happens. This applies to all professional endeavours.



AF447 foundered is spite of the collective wisdom of all who created and operated her.
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Old 27th Apr 2011, 01:28   #169 (permalink)
 
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Design constraints for airliners HF antennas

"maybe us 'radio geeks' should open a separate Tech Log thread about HF aerials on airliners?"

Considering:

1) Crescent EMI/EMC challenges (High RF pwr near sensitive front end circuitry).
2) A clear room for performance improvement
3) A probable "extra life" for HF
4) The passion for the issue

Why not to open it asap?
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Old 27th Apr 2011, 01:33   #170 (permalink)
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I would modify your maxim to wit. 447 was lost perhaps because the collective was not complete, or some of it was insufficient or incompetent.

This was not an act of GOD. This was a failure(s) that killed people. If we knew it to be a fluke, and nothing was to be found as to cause, there would be no Phase 4, or 5. IMO.
 
Old 27th Apr 2011, 01:36   #171 (permalink)
 
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HF aerials

Hi, KMD OM

Here is Charlie Whiskey, (not OM like you, just 60), hihi

Let´s develop a thread on the issue?
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Old 27th Apr 2011, 01:42   #172 (permalink)
 
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Filtering issue

Some years ago i faced a challenging noise filtering issue so difficult i finally drastically changed the original design.

HF pick up by yaw damper in a supersonic a/c remembers me the space " butterfly region" of stones in spacecrafts flight path.

Very dangerous issue and a real threat to dense circuitry.
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Old 27th Apr 2011, 01:45   #173 (permalink)
 
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Bearfoil;

That is my point. I believe everyone put their best effort into designing and operating that A330 but conditions unanticipated by software writers, a dielectric black hole that swallows RF or shortcuts to improve the bottom line will eventually bite our buttocks.

It's all a teaching and learning experience we should not ignore.

Cheers
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Old 27th Apr 2011, 02:01   #174 (permalink)
 
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Comparing HF wire aerials vs newer designs

GB

Could you comment something on Signal strenght (pwr out) with new ones comparing to the old wire antennas? (not trailing wire)
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Old 27th Apr 2011, 02:13   #175 (permalink)
 
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Sounds good

"The proposed airspeed monitoring system would compare changes in measured airspeed over a short period of time with changes in ground speed as computed by the accelerometers and gyros in the aircraft's air data and inertial reference unit (ADIRU)."

If goes fast to "public domain" will be fine

Last edited by RR_NDB; 27th Apr 2011 at 02:19. Reason: Prior art could kill the french patent and will be good
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Old 27th Apr 2011, 02:16   #176 (permalink)
 
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A388

Links to see the design?
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Old 27th Apr 2011, 03:43   #177 (permalink)
 
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An English transcript of the video published on April 26 is now available at the BEA site:

Start of phase 5 of the sea search operations, English transcript
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Old 27th Apr 2011, 09:02   #178 (permalink)
 
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Re: Picture in post #162

Is this one of the underfloor support members?

If so, it gives an idea of scale.

ImageShack® - Online Photo and Video Hosting
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Old 27th Apr 2011, 09:05   #179 (permalink)
 
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Quote:
Originally Posted by RR_NDB View Post
"The proposed airspeed monitoring system would compare changes in measured airspeed over a short period of time with changes in ground speed as computed by the accelerometers and gyros in the aircraft's air data and inertial reference unit (ADIRU)."
From the published US patent application

Quote:
[0007] Generally, aircrafts comprise systems comparing between them the information provided by different sensors. Thus, if most of the sensors provide a similar value, such a value could be considered as true. However, in some cases, being actually very rare, such sensors could be, either all or most of them, submitted to a similar frost phenomenon, so that the systems of the aircraft and the pilots can be without any reliable indication about speed or be unable to eliminate the erroneous speed(s).
The incorporated French patent submitted Sep 23, 2009
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Old 27th Apr 2011, 12:55   #180 (permalink)
 
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HN39.
Thanks for the LF/AoA graph. Thought you would rise to the small challenge!

Fascinating discussion on HF antennae and propagation, chaps... Yes, Graybeard, think the VC10 also achieved whole-airframe antenna from its fin-mounted thingy. Whereas the B707 just had the antenna sticking forward from top of fin. Aft reception could be difficult in my experience on some aeroplanes, but can't remember which ones of VC10, B707, A310, or DC10. Pretty sure the VC10 is better than B707 in that respect. Aerial-tuners also used to be a problem sometimes, leaving you with the inability to transmit. Changing freq sometimes solved the problem.

Re VHF-AM in static, I'd just like to point out that ear-splitting static often accompanies St Elmo's fire.
 
Re Airbus's proposal of using GS as a way of checking the veracity of sudden indicated-airspeed changes, the Flightglobal report quotes Airbus as saying:
"While airspeed and ground speed can not be compared directly, Airbus notes that over a "very short period", normally significant factors like windspeed, changes in altitude, air temperature and angle of attack will be negligible, allowing for a direct comparison of changes in speed rather than speed itself."

I wonder what "very short period" they have in mind. By definition, large aircraft never experience rapid changes in GS. IAS/CAS, on the other hand, changes very rapidly in gusts. In the different situation of entering a jetstream from the side, the tailwind-component (for example) can increase by 100 kts in two or three minutes. This leads to a steady loss of IAS, which has to be recovered by climb thrust to build kinetic energy until the GS has been increased by the 100 kts.

On walk-rounds, I sometimes pondered on the positioning of the three probes. #1 & #2 are usually symmetrically positioned; #3 usually near #1. All seem equally susceptible to icing. But is it only the shape of the probe itself that matters?

Another point: can't someone invent an even more powerful heater that could kick-in as soon as a sensor/camera shows the beginning of ice formation? On the VC10, we had an ice-probe visible under the captain's DV window. It had a light which enabled the captain to inspect it with mark-1 eyeball, and a heater to de-ice it. (If it was icing up, we would put the airframe anti-ice on.)

Wouldn't it be nice if pilots could actually SEE their pitot tubes?

Last edited by Jetdriver; 27th Apr 2011 at 17:48.
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