Mason From United States of America, joined Jun 1999, 748 posts, RR: 1 Posted (14 years 5 months 2 days 19 hours ago) and read 11210 times:
I was thinking how bennifical the Concorde would be on flights like JFK-LAX, SFO-LAX, MIA-JFX, etc...Why isn't the Concorde permitted to fly supersonically over land? Military fighters do it every day. Plus, the Concorde flies so high, no other aircraft would even be close to it!
Woodsboy From United States of America, joined Mar 2000, 1031 posts, RR: 3
Reply 2, posted (14 years 5 months 2 days 19 hours ago) and read 10996 times:
From what I remember it was a pretty effective lobbying effort by environmentalists who argued the detremental effects of sonic booms and the very loud t/o performance of the Concorde. I think also there were concerns over the highly polluting, smokey turbojet engines.
But as I have thought about this over the years I know that military a/c fly supersonically, perhaps though not so often over land than over the ocean.
When Branniff flew the Concorde I believe they either had to fly subsonic till they got to the East Coast then increase speed or they had to stop for fuel somewhere before crossing the Atlantic- does anybody know this for sure?
777x From , joined Dec 1969, posts, RR:
Reply 4, posted (14 years 5 months 2 days 18 hours ago) and read 10971 times:
The sonic boom is a shockwave that travels along with the aircraft, creating a sonic boom everywhere they plane is flying supersonic, not just when the plane transitions, or on a period basis.
This means that if a supersonic plane flew from NY to SF, EVERYONE living along the flight path would expirence the sonic boom. (The width of the affected area on the ground varies on aircraft size, but AFAIK for concorde it's ~20 miles)
Back when the US was working on the SST, test flights were flown with a milary aircraft flying supersonic over populated areas, but complaints were high and property damage resulted (broken windows mostly). Therefor there was a strong backlash against the supersonic aircraft being used over land (or at least populated areas)
JFL From , joined Dec 1969, posts, RR:
Reply 6, posted (14 years 5 months 1 day 19 hours ago) and read 10917 times:
Hi guys !
As previously said, the problem of supersonic fligth is the sonic boom.
The development of CONCORDE over the US is not restricted by polution nor because of noise restriction. CONCORDE is allowed by FAR 91.821 to operate over the US, even if he is not even complying with Stage 2 noise level.
Per FAR 91.817, no A/C may be operated at a true MACH of more than 1. Also the Mmo must not be above MACH 1 unless fligth crew was informed of the restriction.
As one folk said this FAR has been instated because of damage that can cause the sonic boom.
CONCORDE can fly to LAX but it will have to reduce to or below Mach 1 when reaching the ADIZ.
This will anyway not or quite not happen because CONCORDE has "short legs" and CDG-JFK is already close to the range limit of the airplane.
Ilyushin96M From United States of America, joined Sep 1999, 2609 posts, RR: 12
Reply 7, posted (14 years 5 months 1 day 19 hours ago) and read 10903 times:
I remember when the Concorde entered service in 1976, it was the subject of much controversy here in the States. I remember the newspaper articles about the noise regulations, and how difficult it was for BA and AF to get the necessary permits even to operate in and out of JFK and Dulles. And yes, when Concorde was operated by Braniff on DFW-JFK, it was a feeder route, and did not operate at supersonic speeds.
I've experienced sonic booms several times. It's no wonder supersonic flights over populated areas are not allowed, the shock wave is quite noticeable, and jarrs one's nerves, especially in areas where earthquakes are common. But I wonder if specific routes couldn't be flown at supersonic speeds, over sparsely-populated areas, with Concorde slowing down as it approaches its destination?
As far as Concorde's range...it is my understanding the aircraft can fly as much as four hours between fueling stops, hence the flights between London and Barbados, and Paris and Rio de Janeiro. Anyone know any differently?
Turbulence From Spain, joined Nov 1999, 963 posts, RR: 20
Reply 8, posted (14 years 5 months 23 hours ago) and read 10876 times:
Just a little note:
The sonic boom is a “little” phenomenon that DOES NOT last for all the supersonic flight. It is not desirable to occur over populated areas, since it can cause (minor) material damages, but actually is nothing else than a wave conflict.
When the flight is subsonic, the air mollecules in front of the airplane start vibrating BEFORE the the airplane reaches to them, due to the sound propagation, travelling faster.
When the flight is supersonic, the nose (well, let's maybe say better “the needle” ) must cut the air mollecules that are immobile yet. Therefore there's actually a needle and not a nose, and therefore the use of special materials in order to support the high temperatures reached because of friction due to the “extra” work of cutting the air. Do not forget that, despite we do not feel it because of our low walking speed, air is something very very dense. Just try to take your hands off the window of your car when travelling at 130 Km/h (72 mph) in Europe (or 250 Km/h in Germany or in Montana daylight if you are that lucky), or even at just 55 mph (88 Km/h) in the US. Then try to imagine that speed made 1240 Km/h.
Back to the sonic boom, there is a moment, just when the speed of the plane is equal to that one of the sound, when both vibrations reach to the air mollecules at once. The sum of both vibrations creates a much bigger one which can be heard as an explosion, louder and deeper than the noise of the turbines, since the wave length is double.
Thus, a Concorde could take off from JFK, LGA or EWR east bounded, break the sonic barrier over the Atlantic, turn 180º, fly supersonic westwards absolutely silent (from earth distance, of course) over crowded land, slow down over the Pacific ocean, and land nicely and quietely at LAX.
Leo-ERJ From , joined Dec 1969, posts, RR:
Reply 10, posted (14 years 5 months 19 hours ago) and read 10865 times:
Actually the main cause of sonic booms is the large pressure gradients created by sound waves which names itself the so-called "compression shockwave". Whenever travelling at M larger than one, the aircraft is always ahead of the sonic waves which eventually produces a cone behind the aircraft. The faster the aircraft flies, the smaller the angle of the cone gets and hence it will create sound disturbances, much like tubular sea shells you may find at the beach.
In the case of not being able to fly over land is probably already stated above as to restrictions regarding sound disturbances over populated areas.
Boeing 777-400 From United States of America, joined May 1999, 128 posts, RR: 2
Reply 11, posted (14 years 5 months 18 hours ago) and read 10863 times:
"Back to the sonic boom, there is a moment, just when the speed of the plane is equal to that one of the sound, when both vibrations reach to the air mollecules at once. The sum of both vibrations creates a much bigger one which can be heard as an explosion, louder and deeper than the noise of the turbines, since the wave length is double.
Thus, a Concorde could take off from JFK, LGA or EWR east bounded, break the sonic barrier over the Atlantic, turn 180º, fly supersonic westwards absolutely silent (from earth distance, of course) over crowded land, slow down over the Pacific ocean, and land nicely and quietely at LAX. "
but it doesn't make sense to me, the sound barrier could be broken over the atlantic, and if you fly supersonic over the U.S. there wont be and sonic booms?!?
When a concorde flys over the water and comes close to other aircraft, why doesnt it damage them? If it breaks windows 10 miles to the ground then shouldn't something happen to those other airplane should they get too close?
JFL From , joined Dec 1969, posts, RR:
Reply 14, posted (14 years 5 months 10 hours ago) and read 10844 times:
Just one precision, CONCORDE is a very complex piece of aircraft. You will almost never fly straight & level with CONCORDE. During all the flight, all alt/speed variation the FE has to X-FEED fuel from aft to FWD to modify CG. Has the Rolls Royce jet engine is not a bypass engine, the higher it is operated the best perfs you'll get (fuel efficiency). SO from CDG to JFK you will climb almost all the flight. The descent is an "open descent".
So you can't say just T/O fly away, climb, get speed and finally head to destination. You'll have lost to much time. And anyway by law (FAR) it's impossible unless no sonic boom free (no solution as for today's technologies).
777x From , joined Dec 1969, posts, RR:
Reply 15, posted (14 years 5 months ago) and read 10836 times:
Maybe this wasn't stated clearly enough earlier in this thread, but let me reiterate, because many of you seem to believe that the sonic boom only occurs at the point the aircraft goes supersonic.
The Sonic Boom is a pressure wave that is present in front of the aircraft continuously while the aircraft is supersonic, thus producing a constant overpressure in front of the aircrafts flight path, and to the human ear, this is the sonic boom.
So, the sonic boom CAN be heard (& felt) along the ENTIRE flight path of the aircraft whilst it is supersonic, so an aircraft (such as concorde) could NOT simply take off, head over water, go supersonic and then proceed over land.
For a more detailed description, there is a link in my earlier post.