AC Condensation at Gate

[Pavement Guy]

I'm looking into a fairly unusual issue where the concrete apron underneath parked aircraft is partially dissolving due to what appears to be fluid dripping out of aircraft. This is happening at several different terminals of the same airport, serving different carriers, and always directly underneath parked aircraft.

My first thought was this was some sort of de-scaler used in the aircraft water system, but our tests of the concrete show no cation enrichment, just leaching of calcium.

So I'm thinking that this is maybe due to water extracted from the air conditioning system or maybe APU bleed air system. The few diagrams I've found of aircraft air conditioning systems show that the extracted moisture is sprayed into the ram air system. However, I figure this wouldn't be done when the aircraft is parked on the ground.

Is there a secondary direct vent for this extracted water to the exterior of the aircraft? Where would it typically be, and what might it look like? Also, how hot would the water be?

Any help would be greatly appreciated!

[bcgallacher]

The 747 has three air conditioning packs in the unpressurized area of the lower fuselage which can produce cold air down to about +4deg C . In high humidity conditions condensation forms on all the external surfaces of this cold ducting and drains on the concrete sometimes in considerable quantities . The water centrifuged and drained from the cold airflow is indeed injected into the heat exchanger matrix but emerges as invisible water vapour at high temperature . Quite what you can do about this I do not know - I worked with large passenger aircraft for over 30 years and this is the first time that I have heard that it is a problem. Better quality concrete perhaps?

[emergency000]

Possibly runoff from de-icing fluid? Or if the aircraft are washed on the bay that could also be a potential culprit.

[Capot]

Jet fuel - and maybe Avgas - can do dreadful things to all kinds of pavement, as I'm sure you know.

But even minor spillages are very rare, and any leak from an aircraft would be treated as a a symptom of a major safety hazard and dealt with before anything else.

So it's very unlikely to be fuel that's behind the deterioration, but it might be worth double-checking that.

[SeldomFixit]

Is it directly under the airplane's footprint or off to the side?

I'm guessing it's Diesel from GSE which eats concrete like a $3 whore eats a virgin boy :uhoh:

[bcgallacher]

Pavement Guy - I have worked at airports worldwide,seen water running down the ramp from A/C pack condensation in all sorts of climates but have never seen it cause any kind of damage It is only water after all, depending on configuration just about all aircraft will drip water to some degree.About all I could suggest is paint the affected areas with something like the stuff that is used on garage floors. I really think that the cement or concrete that you have is the problem. Please keep us informed, too many times advice is asked then no feedback -which is annoying.

[Capot]

I'm guessing it's Diesel from GSEI didn't think of that, which is ridiculous after the thousands of hours I've spent wandering about on the ramp. It's a very good suggestion!

[BeeBopp]

Could it be that aprons are now taking aircraft weights which were not considered possible when some of the airports were built. Frost and ice will do the rest. I know the ACN and PCN are supposed to be compatible but when you see the state of some aprons it is hardly surprising they are deteriorating.

[mad_jock]

Well on our aircraft that water is the pax's sweat which condenses on the inside of the hull then melts and there goes down to the bottom of the hull and gets let out through the drain valves in the hull.

So I suspect you have salt damage.

Concrete Deterioration by Deicing Salts: An Experimental Study (http://www.ctre.iastate.edu/pubs/semisesq/session1/cody/)

[cockney steve]

Very similar thought to mad jock, Ithought a combination of condensation from Pax breath and sweat, added to which, sundry urine splashes/leaks and "waste water" leaks/spills. It's amazing how even a very weak acid can erode concrete which was not formulated to withstand it.

[sb_sfo]

Just to be clear, you're not talking about pavement degradation under the drain masts, but elsewhere?

[bcgallacher]

I presume that it rains from time to time in your neck of the woods - does this seem to do any harm? Diesel fuel on the ramp would be obvious and it is unlikely to be underneath the centre section of the aircraft - at the front where a GPU would be positioned perhaps.A pushback tug might drop oil but that too would be obvious.What exactly is happening to the concrete? Is it over a large area or small isolated areas and is it so bad that it causes concern?I still think you have something wrong with your concrete.I have worked in the UK,Europe,USA,South and Central America,Far East,India,Pakistan,Central Asia,Caribbean , Africa ,Middle East and places I have forgotten but have never seen ramp damaged by anything from the Aircraft or refuelling equipment. fuel spills on long haul aircraft were common at one time,even Phosphor ester based hydraulic fluid does not seem to cause a problem.Get some kind of concrete expert to have a look. Just one point - do you have a high salt atmosphere in your area as salt can cause concrete degradation.

[Capot]

I've seen concrete and tarmac (to use a fairly inaccurate term) turned into sludge by Jet A1 spills. Diesel would obviously have had the same effect.