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Guest eker

Another small quiz

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Continue Mark`s success.A 737NG at normal cruise. A/P & A/T engaged.In forward galley: 100kg of beer and softdrinks to be consumed during 3 hours of flight (still same cruise)Q:What changes will occur (aircraft, aircraft system) during this scenario?Note: Toilet waste tank located in aft section of aircraft.eker.

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CG would move aft therefore trim would be added in the direction of nose down?

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Hi Jamie... (waving back)..Your conclusion is right.... and wrong...It is a bit more complicated.eker :-)

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I'll take a stab.It would change the CG and would change the trim slightly until the people who drunk it went to the toilet, then it would be deposited in the aft section of the plane causing a more significant trim change?What do I win? :DCheers!Liam

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Hi Liam...Did I forget to mention the prizes?..... Sorry!Of course you won first:A trip from your favourite airport to Las Vegas in a brand new PMDG 737NG! Sorry - but just one way ticket.Second prize - not yet a candidate:Full tank of fuel (PMDG 737NG) delivered to an airport near you.( Correct answer tomorrow -sunday)eker

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I would suggest a change in the CG to the cabin for a short time, thence aft and finally a diversion to the nearest airport to offload unruly pax which would result in a weight redistribution. :-)ScottYBTL

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Solution:1. Main point: Stabilizer produces downforce to keep nose up. (Stab looks like an inverted wing)2. Moving weight aft means that you do not need so much downforce and the stabilizer trim to a closer aerodynamic zero. - 3- Resulting less drag and airspeed increases - and autothrottle reduces power.Thank you guys for interest and I really enjoyed ALL answers!:-) :-) eker

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"A 737NG at normal cruise. A/P & A/T engaged.In forward galley: 100kg of beer and softdrinks to be consumed during 3 hours of flight (still same cruise)Q:What changes will occur (aircraft, aircraft system) during this scenario?"Interesting mental exercise, Eker....My 2c's worth on a very complex issue.... :-)Oddly, you may have to look at the hygiene standards of the passengers. Do they wash their hands after going to the toilet.. and how much water do they use doing this? A potable water tank supplies water for washing hands, flushing toilets, etc. This tank is located towards the rear of the aircraft (like the waste tank). Depending on hygiene standards, more water may be used by the washing of hands than the flushing of toilets (Vacuum toilets use very little water for flushing). So-called "grey" water drained from the hand basins is vented from the aircraft via fuselage Drain Masts... It doesn't go to the waste tank, therefore water may be removed from the rear potable water tank almost as fast as toilet water is put into the rear waste tank. There may only be a certain percentage shift of weight to the aft as a result of consumed beverages ;-) What is the density of alcohol-laden urine with respect to potable water? If it is less dense, then perhaps there would be an even slower weight shift towards the rear? This however, may be offset by the diuretic effect of alcohol, tea, etc... There may be more liquids "wasted" than drunk.There may be 100Kg of beer and softdrinks available to be consumed, but perhaps not all the 100Kg is consumed. The Fwd Galley may be catering to First and/or Business Class (These people usually have a greater selection of beverages... and therefore might only drink a small percentage of the available beverages).Any prizes for the most convoluted answer? :-)Cheers.Ian.

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Let us not forget the redistribution of payload as a result of drunken passengers unable to find their assigned seat, and sitting somewhere completely different after a visit to the lavatory. Depending on how full the flight is, this could potentially invalidate any calculations of CG shift based on liquid consumption and "redistribution".

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Ross.Give you a few points ;-)More seriously - Ian.Good! Didnt think of graywater myself. An important factor to be considered. We have a winner!!eker

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Unless, of course, the Drain Mast Anti-Ice system isn't working properly.... :-)28Vac is supplied to the heating system on the ground... and 115Vac in the air. On other aircraft, I have seen cases where the air/ground relays are not operating properly.... or where heater elements have broken.Who would have thought grey water Drain Masts would have affected C of G!Cheers.Ian.

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