Larry Dighera wrote in message . ..
On Thu, 05 Feb 2004 13:06:42 GMT, Juvat
wrote in Message-Id: :

After an exhausting session with Victoria's Secret Police,
(Krztalizer) blurted out:

Any idea who owns this or what it is doing? From under the landing pattern for
San Diego's International Airport, we watch dozens of airliners and corporate
jets gliding down to land.

Hope your observation point is not on short final to 27...I get a
chuckle thinking of the folks that live with spooled up 757s passing
less than 200 feet RA (radio/radar altitude) over their noggins. I'd
love to see a 747 on final to 27 (must have at some point since there
are special taxi lines labeled 747 at the threshold of 27).

Wonder what a house costs right there, wonder what conversations are
like inside those homes.

In the '50s with the advent of turbine powered aircraft, the B-707
noise assault on homes under the 4 approach paths to LAX 3 to 4 miles
distant from the threshold was so bad, that it was completely
impossible to have a conversation or hear the 6 o'clock news. I would
characterize the constant din of arriving aircraft overhead every 5
minutes for a couple of hours every night as being unhealthy and
EXTREMELY LOUD. Within a year or two, property values plummeted to
the point that minority residents were able to afford veritable
mansions in the once prestigious neighborhoods surrounding the
airport.

The homeowners' litigation against the City of Los Angeles raged for
decades. The city was ultimately forced(?) to purchase much of the
prime ocean front property under the departure path at depressed
prices. The city's reprehensible conduct in permitting the operation
of noisy aircraft to degrade the environment of residents' habitat to
such a degree that they were forced to move was/is the epitome of
hubris.

But like the effective hushing of police helicopters, that in the '70s
were so loud overhead on their nightly neighborhood patrols that they
would repeatedly rouse sleeping residents, today's airliners are as
quiet as many piston powered aircraft. In the end, the city's
arrogance provided minority citizens an otherwise unavailable
equal-rights opportunity at a time when local laws required 'negroes'
off the public streets after 10:00 pm. And the Great Experiment
trundles forward ...



I wonder if jet engine engineers had of been given an absolute
imperative to develop silent engines for 50s and 60s commercial
avaition we could all have been spared this.

Jet engine development was driven by the needs of the Military and for
them noise and soot come second to succesfull penetration and
survival.

Personaly I think given a requirement and the industry would have
risen to the challenge.

I was reading about a rather quiet turbofan engine the germans were
developing and ran succesfully on a bench several times in 1943 but
was cancelled so that resources could be freed for the more
desperately needed conventional turbojets and their turboprop
derivatives.

The Daimler Benz DB 007 was a rear fan turbofan in which the outer
part of the turbine also acts as fan. The mixing of high velocity
with medium velocity air apparently made the engine quiet.

I believe some business jets used such a rear fan configuration.
Can't recolled the name now?

The engine consisted of a contarotating stator drum and inner axial
compressor driven by gears. At the rear the inner 30% of the turbine
was in low pressure bleed air and here it acted as a sort of gentle
fan. The outer 30% acted as a fan as well. The middle 40% was in
combustion air of about 1100C. Most german engines ran at just under
800C and used hollow cooled blades but in this configuration the
blades could handle 1100C without inner cooling since the roots and
tips were in very cooling airflows.

Silencing seemed to require introducing the turbofan, getting rid of
the external support spider, and mixing he hot exaust gases by
creating turbulence and simply putting sound absorbing padding around
part of the assembly.

Engines these days are so silent one hardly notices the A320 B737NG
class of aircraft. They are at their worst when manoevering
excessively to avoid overflying areas to keep the noise down.