Upgrade from J to F Sin-LHR worth it?

If I had the points to spare, and for an overnight flights, I would do it. Especailly if you have never experienced long-haul F.

You get a sleeper suit (pyjamas), better amenities kit, better food and beverages, a fully flat bed with duvet and supposedly better service. Oh, yes, and don't underestimate the feeling of turning left :wink: .

Your seat also has a built-in VCR and there is a library of around 50 or so movies to select. This is not as big a benefit for AVOD flights, but at least it tends to be a little more reliable than the new AVOD system.

You will also get access to the First Class lounge at SIN.

 

Another way to look at whether you should do it is

"If you need to ask the question then you need to try it"

Go for it :!:

 

Oops. Looks like we may have created another F junkie .

 

Now that QF31 departs SYD at ~5pm and SIN at ~Midnight, I believe you will find the First Lounge will be open in SIN.

 

Actually, none of the air that enters the cabin through the air conditioning system is "recycled". It is outside air that is compressed and then cooled and fed into the cabin. The outlet from the cabin is vented outside.

Note that even though the outside air at altitude is very cold (sometimes less than -50 deg C, it is very thin and must be compressed to feed into the cabin. The air is sourced as "bleed air" from the engines, and the compression process causes the temperature to increase significantly. At normal cruising altitudes, the air compressed bleed air temperature is such that it can generally be regulated through heat exchanges and the Air Cycle Machine (ACM) are bypassed, but on the ground the AC packs are used to cool this compressed air to suite the desired cabin temperature.

The cabin Environmental Control Unit (ECU or "Pack") removes moisture form the air, and that is about all.

The composition of the outside air that is fed into the cabin is basically unchanged (just moisture removed). Contaminants are neither removed nor added any more than would be the case with a home air conditioner filter would alter. Small air particles and some things like Ozone are filtered.

One thing that can be affected by the heat of compression is ozone, and it is interesting to note that the high pressure caused supersonic flight of the Concorde destroyed nearly all the ozone so no further treatment with catalysts or filters was necessary. This is not the case with commercial sub-sonic aircraft.

So the concern of breathing recycled air is a busted myth. The risk of catching something from fellow passengers is no more than it would be if you were sharing an air-conditioned room with the same people. In fact, in many aspects the risk is less due to the volume of air that flows in and out of the cabin and the fact that no vented air is recycled.

 

Welcome to AFF Vick. I have done a little more research into this matter and dug up some interesting facts. My original comment is out of date and based on very old (and inefficient) systems found on aircraft like the DC9. Modern aircraft do indeed use some proportion of recycled air in the cabin.

A 20 year old (1986) US congressional study into the health affects of cabin conditions on travellers and cabin crew determined that the rate of flow of outside air into modern airliner cabins varies from a minimum of 7 cubic feet/min per economy class passenger, to 50 cfm/first class passenger. These rates vary significantly between airliners and operators. The minimum rate to meet the oxygen needs for people is about 0.24 cfm/person.

A flow rate of 7cfm/passenger (the lowest possible with current equipment design) results in approx 50% recycled, filtered air. So 50% is a worst case scenario. Note that 50% is similar to commercial building air-conditioning, so the time spent in the airport terminal is likely to result in more exposure to recycled air than the time spent in the cabin. Its just that we don't usually spent 14+ hours at a time in the terminal!

The study mentioned above found that the flow of outside air into the cabin for a 747-200 with 318 passengers and using 3 ECUs set to "normal" flow was 17.1 cfm/passenger (in economy cabin), and 10.6 cfm/passenger when set to 50% flow. These are significantly higher than the minimum of 7cfm/passenger mentioned above. On a 767 with optional filters installed, the flow rate was even higher at 19.1 cfm/passenger.

A 1980 study by NASA shows that a DC-10 could experience about 1% fuel saving if the ventilation from of outside air was reduced from 18cfm/passenger to 8 cfm/passenger.

The use of high-pressure water separators in the modern ECUs results in very dry air from the bleed system. The lack of moisture in this air results in less heating affect during pressurisation, and as a result the pressurised air is often still below 0 deg C. To heat this pressurised dry bleed air, it is mixed with recycled cabin air before being fed to the cabin air inlet ducts.

The recirculated air is taken from different places on different aircraft, but most modern aircraft (eg 747, 767, 777 etc) take it from near the ceiling, while the vented air leaves the cabin through slotted grills at floor level. This is based on the assumption that contaminants are generally heavy particles (at least compared with the low humidity air) and are more concentrated at floor level, while the air at the top of the cabin contains less contaminants.

The proportion of recycled air is higher on newer aircraft due to the need to further heat the very dry air that results from the newer high-efficiency high-bypass engines and high pressure water removal process. However, recycled air filtering treatment has also improved over time.

Environmental Tobacco Smoke (ETS) is no longer a problem on most flights. It was determined that 7 cfm/passenger was insufficient to remove the hazardous affects of ETS. This required about double the flow rate. As can be seen from the NASA study noted above, by banning smoking from flights, the airflow can be reduced and fuel savings achieved. So there was more than just health issues as an incentive for airlines to ban smoking, or at least to support the government regulations.

The low relative humidity in the cabin, generally less than 20% and can be as low as 2% depending on the circumstances, may cause passengers some discomfort after prolonged exposure. After 3 to 4 hours of exposure to 5-10% relative humidity, passengers may suffer from dryness of the eyes, nose and throat. The use of high-pressure water separators in the modern ECUs results in even lower cabin humidity.

Of course there is a trade-off. High rates of outside air intake result in lower concentrations of carbon dioxide, carbon monoxide and other contaminants. But it also results in lower relative humidity and increased ozone when operating at certain altitudes.

Of more concern to me is the low relative humidity and exposure to cosmic radiation (for very frequent travellers). The low humidity is an efficiency issue since moisture in the air adds weight to the aircraft and hence more lift is required to maintain flight resulting in higher fuel burn. It is this low humidity that causes discomfort on long flights.

 

A true gentleman, acknowledges his mistakes...well done NM.

As for both the explanations, wow, I'm like Damien...but that's why I think NM is a great guy. His knowledge, research and ability to explain in terms we can understand is indeed astounding...