PlaneSmart From New Zealand, joined Dec 2004, 1689 posts, RR: 0 Posted (11 years 5 months 1 week 6 days 21 hours ago) and read 5533 times:
If cabin air was replaced as frequently as in the 70's to mid 80's, (partly because smoking was permitted back then), bleedless engines wouldn't be viable, as the power req'd to heat incoming air for cabin use would be too great. As cabin air standards are currently set so low, bleedless is possible.
What is the maximum cabin refresh rate the 7e7 is going to be capable of at 30,000 feet versus 777, 767, 757, 747, A32, A33, A38, MD11?
How will 7e7 operators raise the refresh rate if a higher standard is demanded / req'd by customers and/or the World Health Organisation?
JetMechMD80 From United States of America, joined Jul 2004, 380 posts, RR: 6
Reply 1, posted (11 years 5 months 1 week 6 days 16 hours ago) and read 5472 times:
There is no difference between the rate the cabin air was "replaced" in the 70s. and 80s. The same aircraft are in service, with the same packs, recirculation fans, and out-flow valves. They are operated the same way they always have been. The goal is to pressurize the cabin, and heat it to a comfortable level. That's it. Nothing has changed. I can not answer your other questions about the 7E7's rate, or WHO standards. Sorry.
Dalmd88 From United States of America, joined Jul 2000, 2891 posts, RR: 14
Reply 4, posted (11 years 5 months 1 week 6 days 9 hours ago) and read 5426 times:
The current rate of air refresh is actually very high. Somewhere I read a report from Boeing detailing the 767 system. The air exchange rate actually exceeds the rate for an infectious desease area of a hospital. I'll bet the 7e7 will still have a similar rate.
Ha763 From United States of America, joined Jan 2003, 3739 posts, RR: 5
Reply 6, posted (11 years 5 months 1 week 6 days 1 hour ago) and read 5382 times:
According to Boeing, the norm on most Boeing aircraft is 50% recirculated and 50% fresh air. I say, "most Boeing aircraft," because the 717 is 100% fresh air. Also current cabin air systems circulate enough air to replenish the whole cabin every 2-3 minutes. This is way better than the air exchange rate in an air-conditioned building. More info can be found here:
HAWK21M From India, joined Jan 2001, 31875 posts, RR: 54
Reply 7, posted (11 years 5 months 1 week 6 days 1 hour ago) and read 5392 times:
The B732 I remember correctly did not have Recirculating Fans,so the Air was 100% Fresh bleed extracted Air.Later versions did come up with One or Two Recirculating fans & so the percentage of Recirculated Air Increased.
However Present Day Aircraft have a refresh rate thats adequate,With no Smoking on board,things are more better.