Qatar 787 smoke

[Cathay Boy]

Any electrician knows you spilled water on wire, if the wire is wet, you ignore it, and there eventually will be fire. If 787 do have condensation issues it is a flying fire hazard, pure and simple. If 787 is prone to condensation like many of you have said, then it all makes sense. Nothing you can do on wiring, electrical systems, battery, will prevent a fire if there's condensation that make the electrical systems, wires, battery, wet over time, it will catch on fire.

I don't know what Boeing is doing to "fix" the condensation issue, but if it is not taken care of, 787 is a flying fire hazard waiting to happen.

[Speed of Sound]

An engine out is an engine out. As long as no bits come off it and the fuel flow to it is stopped, then as has been said, it will fly perfectly well on the one remaining engine.

An electrical problem however, can be anything from not being able to watch your chosen video on the IFE to a fire in the roof of the rear cabin at an altitude where a rapid descent is necessary.

[UAVop]

The fix for the condensation issue was to finish them.
When the aircraft sit on the line outside at Boeing Everett unheated, condensation forms on the inside of the fuselage tube. It drips down to the cabin ceiling, quite a bit actually, would almost sound like rain inside.

[Tu.114]

As long as the thread is drifting anyways: From the other thread, I gather that the upper half of the fuselage is completely uninsulated. On the F70/100 with insulation wrappings between the outer skin and the cabin and a "standard" humidity in the cabin, it is rather common to have light rain in the flight deck during descent. And the 787 with its uninsulated shell and higher humidity must gather much more condensation than the humble Fokker.

So are there any systems, drains etc. in place to gather the unwanted humidity and dump it overboard safely? Or is the water just left to swash around until it reaches the bilge and gets dumped via some drain holes in the lower fuselage?

[Finn47]

The 787 has this "zonal drying" system, made by CTT Systems AB of Sweden:

The system effectively removes moisture using established industrial technology. The system takes air from the crown area or cargo area and feeds it though zonal dryer units between the cabin and the outer skin of the aircraft using a specially designed piccolo duct. This lowers the dew point in the crown area preventing the condensation process from occurring, thus keeping the insulation blankets dry.

Depending on aircraft type, the Zonal Drying™ System consists of one or more zonal dryer units installed at strategic points in the aircraft. Each unit features a slow-moving rotor impregnated with silica gel.

The Zonal Drying™ System is standard equipment on Boeing 787 "Dreamliner" and furthermore available as BFE option on Boeing 737NG.

CTT Systems

[simple-simon]

The 787 has this "zonal drying" system, made by CTT Systems AB of Sweden:

Presumably that doesn't help when the plane is parked on a stand, unoccupied, disconnected from ground power.

[fenland787]

From the other thread, I gather that the upper half of the fuselage is completely uninsulated.

I'm not sure that is right as far as thermal insulation is concerned, is this a confusion between the folk on the other thread worried about the SFT properties of composite materials pointing out that the 'special' insulation put between wires and the skin to protect against heat, arc and sparks was only fitted in the lower 180 degrees of the fuselage?

I was fairly sure there was thermal insulation blanket in the crown. However, if I'm wrong no doubt someone will put me right!

[cldrvr]

I was fairly sure there was thermal insulation blanket in the crown

common sense dictates there has to be or else the pax will end up as popsicles on their first pond crossing, if they don't suffocate first of course because of the smoke........

[Tu.114]

Thank You for the link, Finn47. An interesting system; it makes me wonder though whether it was already operative on the initial test flights that apparently led to the aircraft being dubbed "Rainliner".

Does anyone know if this system is releasable via MEL?

[UAVop]

I have been in the aircraft sitting on the line up at Boeing Field, when you would go inside, you could easily hear the water drops. Most of these had completed interiors, just sans engines.
I have not been in a delivered aircraft, that has been sitting, and turned off.

I am sure they didnt add the zonal drying system to the 787 because it would be nice to have.

What is not clear is what happens to the condensation when the aircraft is sitting there turned off, for say, overnight...

[bartonflyer]

Surely if the aircraft is sitting parked without passengers exhaling, sweating and doing whatever else passengers do there is a drastically reduced condensation problem? The only air/moisture inside the fuselage is that which was there when the doors were closed and the aircraft parked!

[cldrvr]

Surely if the aircraft is sitting parked without passengers exhaling,
sweating and doing whatever else passengers do there is a drastically reduced condensation problem? The only air/moisture inside the fuselage is that which was there when the doors were closed and the aircraft parked!

A cold soaked airframe that sits with its door closed will accumulate a lot of moisture inside, especially if the OAT is high/-ish

[bartonflyer]

By what mechanism?
Once the doors are closed as the aircraft is parked then is it not effected "sealed"? If so then the only moisture inside is that which was captured during its last flight?
I'm also puzzled by your statement "....will accumulate a lot of moisture inside, especially if the OAT is high/-ish " - if the OAT is high/ish then that will warm the fuselage and encourage moisture to remain gaseous rather than condense?
Or have I just got the physics wrong?

[UAVop]

From Boeing:

"The cabin's humidity is programmable based on the number of passengers carried, and allows 15% humidity settings instead of the 4% found in previous aircraft."

Sounds like a much higher overall humidity level.

The insulation keeps the moist cabin air warmer longer. The fuselage cools off, and condensation occurs.
Unlike aluminum, the composite material of the 787 allows for significant interior icing at altitude, or as noted above, fuselage interior cold soaking.
When the aircraft is parked, this ice melts and contributes to significant 'rain in the plane' issues for the aircraft.

I just found this from July 18, 2013: condensation may be cause of beacon fire...

"Boeing's new plane has a relatively high humidity, which helps keeps passengers more comfortable, and investigators are now looking at whether there is enough insulation to prevent moisture from condensing and short circuiting systems such as the beacon, said the source, who was not authorized to speak publicly.
A source close to Boeing, speaking on condition that he not be named, said the 787 may need better isolation of electrical components from the plane's high humidity, something industry people refer to as "rain in the plane."

[olasek]

Sounds like a much higher overall humidity level.

We covered that before, 15% is still a very dry air, just about what you get in summer, late afternoon in Death Valley.

[Tu.114]

True, but it still is nearly 4 times the industry standard. So the amount of condensed water per flight hour must be correspondingly higher on this type than on, say, the 767.

I assume that the packs cannot be easily tweaked to remove more water and reduce cabin humidity, should it be found desirable?

[joy ride]

15% is dry, but that is an Average figure for the internal atmosphere. Seeing as much of this 15% is likely to condense/accumulate at the same place, is it enough to be significant?

Elsewhere another poster wondered about the 787 hull's expansion and contraction rates compared to an aluminium plane, and wondered if they might be higher and possibly lead to increased abrasion on the thin Teflon insulation on the wiring. I too would be interested to know the answer to that one!

If the 787's IS greater, then perhaps could these two separate relatively minor issues be combining to make a bigger problem?

[fenland787]

...and short circuiting systems such as the beacon, said the source......

A beacon that is specified for a one hour immersion at one metre depth needs better condensation protection to work in a 787? That must be a pretty aggressive form of condensation they've got in there!

[olasek]

assume that the packs cannot be easily tweaked to remove more water and reduce cabin humidity, should it be found desirable?

Not sure what this all have to do with this particular accident at Heathrow.
The aircraft was completely powered down (for 8+ hours), packs were off, doors were opened, so whatever humidity was inside airplane was the same as at the airport, perhaps 60-80% as it is often the case specially on cloudy, rainy, muggy day. 787's 15% humidity in cruise is completely irrelevant here.

[fenland787]

Elsewhere another poster wondered about the 787 hull's expansion and contraction rates compared to an aluminium plane, and wondered if they might be higher and possibly lead to increased abrasion on the thin Teflon insulation on the wiring. I too would be interested to know the answer to that one!

There are plenty of composite experts on here may know better, but from memory, Al is around 22 x 10-6 mm per deg while Carbon Fiber is at least an order of magnitude less. (changes a bit with % fiber and fiber direction I think?) I suspect in an airplane structure flexure under load is going to dominate and wiring is routed/secured to deal with that.
Think 787 wing profile on TO...!