Post mortem on an IEC connector

There`s a lot of stuff, some useful some 'not so' on the PPrune boards about this accident. Many of the posts are from people who fly these birds everyday for a living, it`s a good read.

Well LVA is still alive and well, I just don't do many repairs any more, I`m concentrating more on live sound production. Sorry Arfa I don`t have a diag for that amp.

Ron(UK)

No sweat. I've found the problem now. Some moron had pinched a wire to the fans under a board mounting pillar when reassembling after some previous repair. It had nicked the insulation, resulting in an intermittent short to the metal pillar. Very odd symptoms this caused. Sometimes, when you flicked the "ground lift" switch on the back panel, the fans would start up at full chat, and a sound that can best be described as a drone pipe on a set of bagpipes, ramped up as the fans ran up. Very odd indeed.

So, where do I find this PPrune board ?

Arfa

This whole "black box recovery" stuff seems silly to me. Given the number of accidents in which the recorders are never found, or when found are FUBAR, and given today's communications technology, I don't know why data isn't being constantly streamed to ground recording centers.

Technically, that'd be a bit tricky on (for example) a trip between New York & London.

Ah. A point that I made to my pilot friend yesterday, and apparently, some of the flight data is streamed to the ACARS system continuously, via satellite. He says that height, speed, heading, inertial nav position estimate, and true GPS position, amongst other things, are transmitted. Which then begs the question of why it is so difficult to locate the position of a downed aircraft. I guess that if it is coming down from 7 miles up, with significant forward speed, and not necessarily in one piece, that might make it more difficult. Still, I would have thought that it would have given them a bit more of a 'ball park' area to be looking in, than seems to be the case. In fact, I remember seeing an episode of ACI, where they took the place of last transmission of an aircraft, and then plotted by computer, how the pieces would fall, and came up with a location for a door I think it was, which struck me as pretty clever.

But yes. Given the level of compression that can be applied to data streams these days, it does seem archaic to record all this data on board the item that you are trying to protect. I suppose privacy issues might come into transmitting flight deck chat, but I'm sure that with the encryption systems available, and operating the same rolling window system, that could be overcome.

I also questioned the state these boxes are in when found, but he said not to be misled by their appearance. Apparently, if they were working in the first place - and that's not always a given, which is a bit worrying - the chances are that they will still be working when recovered. Seems that the actual recorder is inside a sphere, and the battered bit that you always see, is just an outer case, which might contain some ancilliary electronics, and is shaped to fit a rack in an equipment bay. Also, these days, they employ solid state memory, rather than any kind of electro-mechanical recording mech.

Arfa

Arfa

into

and

in

are

down

piece,

would

by

door

streams

systems

electronics,

I thought they retained wire recording, as the data survived fire temperatures above the 150C of Si which is easily exceeded in a sustained fire , up to something close to the melting point of steel.

I see the recent Quantas airbourne rollercoaster affair, over Oz, is now deemed RFI intrusion. I liked the scenario of the prime-minister's motorcade, anti-bomb detonation phone-jammer system passing underneath that Boeing that crash landed at Heathrow last year, just as the fuel management system failed. Compareed to the official version of 2 separate fuel jelling/icing events coinciding

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Really? So transatlantic flights are out of contact with flight control?

I'm sure the Airbus aluminum skin is much more than foil. I watched how it was constructed but forget the exact thickness. I think where lightning is concerned it's not going to matter or even be that much of a concern. To me, the more paths for conductivity as in a fully aluminum-skinned airframe would negate the Faraday effect more than aluminun sandwiched carbon fiber composites.

As far as the 747 goes, yes it is a tried and true airframe and I'm sure they've learned from past mistakes. Doesn't mean that I can completely eliminate them from my mind.

A good jolt of lightning in the right place, a 1 in a million circumstance could have rendered the flight controls useless. It will be interesting to find out what happened provided the flight data and cockpit voice recorders were still functioning after whatefer happened.

Probably some old VK checking if 10 metres has started opening yet ... !!

Yes. That was an odd one. Given that the thing landed basically intact, with a fully alive crew and completely undamaged flight recorders, it seemed strange to me that they would very quickly wheel it away into a hangar, and then take months to reach this conclusion. They talked about the thing passing through an area of very cold air, and on some of the news reports that I heard, they were talking "below -50 deg C". However, when you fly across the Atlantic at 38000 feet, the temperature is always at around -56 deg C the whole way, according to the flight data display available as an entertainment channel, and it doesn't seem to cause a problem. I'm sure that designers must know this, and take it into account when working out the fuel delivery and storage systems. When you think about how much (expensive) systems redundancy is built into jet airliners in the pursuit of safety, it would be a pretty unforgivable design oversight to make the fuel system not able to cope with a few tens of degrees colder than it would normally expect to encounter, wouldn't it ?

Arfa

That certainly used to be the case. Most 'regular' civilian ATC takes place on VHF, which obviously has quite limited range. Transatlantic airliners do stay in contact with their own offices via HF SSB I believe, using a sel-call system. I believe that weather reports are also communicated likewise. I don't suppose that there is much need for ATC when mid Atlantic. Your course is pretty much pre-planned and established, barring odd unforseen circumstances. ATC monitoring used to be a bit of a hobby of mine, but I haven't kept up to date with it. Maybe these days, they are in touch with someone constantly. I guess it wouldn't be that difficult via satellite, especially if they are already relaying ACARS data in that way, as my pilot friend says they are.

Ah. Here ya go ...

Arfa

From Wiki:

"Commercial airliners typically cruise at altitudes of 9-12 km in temperate latitudes, in the lower reaches of the stratosphere.[3] They do this to optimize jet engine fuel burn, mostly thanks to the low temperatures encountered near the tropopause. It also allows them to stay above any hard weather, and avoid atmospheric turbulence from the convection in the troposphere. Turbulence experienced in the cruise phase of flight is often caused by convective overshoot from the troposphere below."

I'm certain even without asking that anti-gel additives are used in commercial and military fuels. But as indicated in the Wiki article\\ different layers of the upper atmosphere have different temperatures and while inside at least the Stratosphere the idea that the higher you fly, the colder it gets doesn't apply.

I've listened to trans-atlantic traffic control on HF, usually lower SSB.

Scroll down to the boxed descriptions.

I honestly don't know, but I assume they would be for at least part of the trip. But even if I'm wrong about that, I doubt that there'd be the bandwidth available for every plane in the air to be continuously streaming 20+ channels of telemetry, etc, back to base.

Commercial lines have GPS tracking and sat communications if needed. Plus there are many HF channels for flight control and military tracking stations located strategically upon small islands, atolls, etc.. that would surely assist commercial aviators.

Yeah, but Jeez, that'd be an incredible effort to go to!

Boeings have always had issues with their design. 737 rudder hydraulics for example were a death trap waiting to happen and some f*****ts let them keep flying despite a serious design issue being known about for 15 years... and as for the 747, we have fuel tanks that explode, engines that fall off, lightning strikes that make the wing fall off to name but a few.

Walk around a Boeing assembly plant, or previously an MD plant and you see workers in casual street clothes, keys hanging off their waistband, loose items in their pockets. Walk around an Airbus plant and you see workers in specific work clothes with *no* pockets, with tight control on personnel access and all losses of hardware being fully investigated. At Boeing you get birds nesting in the structures and people eating food, people dropping small items and just picking another one from a parts bin with no regard for where the stray bits end up. Look at the number of foreign objects found in nooks and crannies on Boeing aircraft during their maintenance stripdowns - a full size sweeping brush FFS! numerous coins, numerous spare fasteners, a mouldy sandwich, even huge ring binders stuffed with 'QA documentation'

Then sit in the other seat with a right handed joystick.

The robot driver *usually* *does* know more, but not always.

Conventionally, a fixed wing pilot sits in the left seat. This is a hangover from airfields having a left hand circuit for fixed wings, so on the circuit leg turns, the bank is in the direction that the pilot has a view of the ground and is able to see that he does not overshoot his turn points. Obviously, that does not apply with airport 'straight in' long finals approaches, but I don't think that you really want to be having one flight deck seating convention for one plane, and the opposite for another.

As far as the robot knowing more than a human pilot, on paper that might be true. But sometimes, complex tasks like flying require dynamic 'outside the box' thinking to handle unforseen circumstances, and that is where the experience and flexible thought processes of an experienced flight crew, might just make the difference.

With the A330 incident, AF investigators have today announced that the automatic ACARS error messages were streaming events of "inconsistent height" and "inconsistent speed", which they think may have been due to the automatic throttles cycling as a result of the heavy turbulence which the pilot had declared he was encountering, using the ACARS manual text messaging option. Presumably, if that was what was actually occuring, it would not have been desirable, and the pilot would have been aware of it, so is this an example of a total fly by wire control system that the pilot cannot disengage, and operate manually ?

The trouble is that once you've thrown away the yoke and other manual controls, there's no going back. I don't have a basic problem with a fly by wire system, but I think that the option of over-riding it in exceptional circumstances, and when agreed by both crew, is the sensible one. If you totally lose the computer systems, or have a total electrical failure on one of these planes, then that's it. You are screwed every which way, and you are going to die. If you have a similar failure on a plane which has a triple redundancy hydraulically linked set of controls, then provided that the fluid resevoirs retain some system pressure, there's a good chance that the pilot is going to be able to at least make a controlled descent, and possibly even a successful landing.

Arfa

into

and

in

Well what effort would you go to if you were in the captians seat and your bearings didn't jive?