NW747-400 From United States of America, joined Jun 1999, 491 posts, RR: 0 Posted (8 years 10 months 3 weeks 3 days 7 hours ago) and read 2419 times:
New noise restrictions with strict guidelines are likely to be issued soon, and the JT8 powered mad dogs may or may not squeak by. If they are unable to pass any new noise restrictions, would it be feasible to re-engine the MD's with new high bypass engines? Right now they are running on a 2:1 bypass ratio and they sacrifice subsonic fuel economy. New high bypass engines, maybe something near 5:1, would improve noise and help tremendously with fuel efficiency. With Delta and American operating hundreds of mad dogs, it is not financially viable to replace the airplanes outright.
Lightsaber From United States of America, joined Jan 2005, 11966 posts, RR: 100 Reply 3, posted (8 years 10 months 3 weeks 3 days 5 hours ago) and read 2296 times:
Pratt has also developed a mixer to squeak the MD-80 past stage 4 requirements. This is similar to the one in the nozzle of the V2500 or the RR Trents. Note: last I looked they hadn't thrown the $$$ to certify it. So noise will not force the issue.
On another front, the MD-80 engines are fairly low thrust. The BMR-175 or pw6000 would both be ok replacements. At today's oil prices, an engine change would be a close call (it all depends on the retrofit costs vs. estimated fuel and mx savings).
PSU.DTW.SCE From United States of America, joined Jan 2002, 7198 posts, RR: 29 Reply 5, posted (8 years 10 months 3 weeks 2 days 21 hours ago) and read 2189 times:
Any new noise restrictions will be phased in. The MD-80's, etc will all be grandfathered in until they are retired. There are simply too many in service, that it is uneconomical to have them all replaced for this before the end of their useable life. These regs primarily will apply to biz jets.
A350 From Germany, joined Nov 2004, 1099 posts, RR: 23 Reply 7, posted (8 years 10 months 3 weeks 2 days 17 hours ago) and read 2102 times:
Aren't there some more flexible rules like landing fees as a function of noise? AFAIK, we have such rules in Germany. Furthermore, will the rules apply to all airports? I think in the US you have some quite remote airports which don't need such strict noise regulations as airports in urban areas need.
Photography - the art of observing, not the art of arranging
Lightsaber From United States of America, joined Jan 2005, 11966 posts, RR: 100 Reply 9, posted (8 years 10 months 3 weeks 2 days 13 hours ago) and read 2010 times:
As the regs are written, you can fail one test by a few db, but as long as you cleared other tests with margin, you can be a CAT 3 or CAT 4. I knew Europe takes a tougher stance, I didn't know the details. Since the ICAO regulations were supposed to be the "end all be all" of noise regulations, it has created friction that individual countries take different interpretations...
There is always a lag between new regulations and enforcement. Right now the airlines are trying to set up the politics so that the US never requires retrofit to CAT 4 (from 3). Personally, I'd like to see a phase out in 15 years (or retrofit), but my opinion and $4 gets you a Latte at Starbucks.
Seriously, non-aviation enthusiasts are really annoyed by aircraft noise. How I like to think of the noise regulations:
CAT 1: non-noise regulated. It hurts when these fly over.
CAT 2: If you're in a house, stop your conversation while the plane flies over.
CAT 3: You could yell over the plane if you're talking in the house, but you're not going miss noticing it.
CAT 4: You could yell over the plane if you're outside the house as it flies over.
CAT 5: (proposed, still under ICAO committee) You could still converse outside of the house. This is the first level where the neighbors noisy mower is more annoying than an aircraft.
Please don't get me wrong, I love aircraft. Maybe its because noise regulations would put more $$$ into engine R&D...