Altitude for legal super sonic flight?

NoSoup4U

Well-Known Member
I have always wondered what altitude a super sonic jet has to be at to travel above the speed of sound. Is there a certain altitude restriction, or is super sonic flight allowed above 10,000 MSL?
 

NJA_Capt

Well-Known Member
I have always wondered what altitude a super sonic jet has to be at to travel above the speed of sound. Is there a certain altitude restriction, or is super sonic flight allowed above 10,000 MSL?
Civilian SS flight is prohibited over the US.
 

SpiraMirabilis

Possible Subversive
(a) No person may operate a civil aircraft in the United States at a true flight Mach number greater than 1 except in compliance with conditions and limitations in an authorization to exceed Mach 1 issued to the operator under appendix B of this part.
(b) In addition, no person may operate a civil aircraft for which the maximum operating limit speed exceeds a Mach number of 1, to or from an airport in the United States, unless--
(1) Information available to the flight crew includes flight limitations that ensure that flights entering or leaving the United States will not cause a sonic boom to reach the surface within the
United States; and
(2) The operator complies with the flight limitations prescribed in paragraph (b)(1) of this section or complies with conditions and limitations in an authorization to exceed Mach 1 issued under appendix B of this part.
and:

(a) An applicant for an authorization to exceed Mach 1 must apply in a form and manner prescribed by the Administrator and must comply with this appendix.
(b) In addition, each application for an authorization to exceed Mach 1 covered by section 2(a) of this appendix must contain all information requested by the Administrator necessary to assist him in determining whether the designation of a particular test area or issuance of a particular authorization is a "major Federal action significantly affecting the quality of the human environment" within the meaning of the National Environmental Policy Act of 1969 (42 U.S.C.
4321 et seq.), and to assist him in complying with that act and with related Executive Orders, guidelines, and orders prior to such action.
(c) In addition, each application for an authorization to exceed Mach 1 covered by section 2(a) of this appendix must contain--
(1) Information showing that operation at a speed greater than Mach 1 is necessary to accomplish one or more of the purposes specified in section 2(a) of this appendix, including a showing that the purpose of the test cannot be safely or properly accomplished by overocean testing;
(2) A description of the test area proposed by the applicant, including an environmental analysis of that area meeting the requirements of paragraph (b) of this section; and
(3) Conditions and limitations that will ensure that no measurable sonic boom overpressure will reach the surface outside of the designated test area.
(d) An application is denied if the Administrator finds that such action is necessary to protect or enhance the environment.
 

ppragman

FLIPY FLAPS!
(3) Conditions and limitations that will ensure that no measurable sonic boom overpressure will reach the surface outside of the designated test area.

How high is that though? That's probably way the hell up there, what are talking about FL600, FL700? The crew would practically have to be pressure suited, and forget pax, if you have a cabin depress the lack of oxygen doesn't kill em, the burning heat from clipping along at mach 2.5 or 3 does.
 

SpiraMirabilis

Possible Subversive
(3) Conditions and limitations that will ensure that no measurable sonic boom overpressure will reach the surface outside of the designated test area.

How high is that though? That's probably way the hell up there, what are talking about FL600, FL700? The crew would practically have to be pressure suited, and forget pax, if you have a cabin depress the lack of oxygen doesn't kill em, the burning heat from clipping along at mach 2.5 or 3 does.
It varies given atmospheric conditions but mainly aircraft and airfoil design. You can google "Sonic Boom Mitigation Study" to read PDFs from NASA on the subject.

I know the SR71 can fly high enough that their sonic boom overpressures are not heard on the surface, or at least are rather quiet.
 

ppragman

FLIPY FLAPS!
It varies given atmospheric conditions but mainly aircraft and airfoil design. You can google "Sonic Boom Mitigation Study" to read PDFs from NASA on the subject.

I know the SR71 can fly high enough that their sonic boom overpressures are not heard on the surface, or at least are rather quiet.
Googling, cool, this looks interesting.
 

SpiraMirabilis

Possible Subversive
Forgot this part in B.92

(b) For a flight outside of a designated test area, an authorization to exceed Mach 1 may be issued if the applicant shows conservatively under paragraph (a)(3) of this section that--
(1) The flight will not cause a measurable sonic boom overpressure to reach the surface when the aircraft is operated under conditions and limitations demonstrated under paragraph (a)(3) of this section; and
(2) Those conditions and limitations represent all foreseeable operating conditions.
Basically you either have to get a test area approved by the Administrator or demonstrate that no overpressure will reach the surface if you want to fly supersonic outside of a designated test area.
 

Hacker15e

Dunning–Kruger Observer
In USAF training, we had a designated route for our supersonic flights. In Mississippi where I trained, there was some 50 or 60-mile arc north of Columbus where we had to go in order to Hit the Number.

IIRC, we had to be above FL310 at a minimum to do it, but FL360 is also rattling around in my brain somewhere.

So, I have to think that the combination of that particular location and that altitude added up to the FAA restrictions mentioned above....since student pilots went out by the dozens and flew this sortie every couple weeks (and at 4 different training bases scattered throughout the country!).
 

Matt13C

Well-Known Member
In USAF training, we had a designated route for our supersonic flights. In Mississippi where I trained, there was some 50 or 60-mile arc north of Columbus where we had to go in order to Hit the Number.

IIRC, we had to be above FL310 at a minimum to do it, but FL360 is also rattling around in my brain somewhere.

So, I have to think that the combination of that particular location and that altitude added up to the FAA restrictions mentioned above....since student pilots went out by the dozens and flew this sortie every couple weeks (and at 4 different training bases scattered throughout the country!).
Can you feel a difference when you are going mach 1 as opposed to mach .95? I remember when I was a kid they had the "mach 1 experience" at a Six Flags. They made it feel as though the moment you went through the speed of sound everything got smooth as if all forms of turbulance was no longer an issue. I figured this was just their way to add to the experience but never really knew as i have never been mach 1+.
 

Orange Anchor

New Member
I have always wondered what altitude a super sonic jet has to be at to travel above the speed of sound. Is there a certain altitude restriction, or is super sonic flight allowed above 10,000 MSL?
Not so much a function of altitude but rather just making sure the big BOOM does not reach the ground as a sharp audible.

Here's a somewhat recent piece on the supersonic bizjets. Interesting about how they are working to turn the over-under-return to ambient pressure from a sharp N into a fast long S turned on its side. http://tinyurl.com/45ca8a

This site talks about the NASA F-15 modified with the 'quiet spike'. You can google NASA quiet spike and get more.


A second airplane, a highly modified Navy (aggressor squadron) F-5, dubbed the Pelican also studied how to lessen the boom. It is now at museum in Florida.. Valiant Air Command?



Finally, if you just want to look around at some of the NASA birds and projects. here is a great page.
http://www.dfrc.nasa.gov/Gallery/Photo/index.html
 

NJA_Capt

Well-Known Member
This is not true.
In practice it is true.

"As a result of the noise and other environmental factors, civilian supersonic flight over land has been outlawed in the United States since 1968." - http://www.ainonline.com/news/singl...itments-for-ssbj/?no_cache=1&cHash=d334b9758d

First, No operable certified civilian aircraft capable of sustained mach cruise exists (no you cannot include demil'd fighters).

Second, the only way you are going to get approval is for flight testing, not for "travel" purposes. You can't just call a FSDO and get permission to do it from A to B and you can't just buy an F104 and file for Mach cruise.

Several designers are developing supersonic business jets. One of the biggest hurtles is the availability to cruise SS over land. The manufacturers are pushing to remove this ban.

There is more to it than just flying high enough to mitigate the N wave. Concorde had an overpressure of approx 2.1 psf at FL490. A test aircraft (F5, later an F15) had an overpressure of over 2.5 psf at FL570. Current goals (DARPA) are for overpressure of approx 0.3 psf.

For the record, NetJets has been involved with several manufacturers and the FAA regarding supersonic business jets for over 5 years.
"The group comprises Boeing, Cessna, Gulfstream, Lockheed Martin, Northrop Grumman and Raytheon, as well as General Electric, Pratt & Whitney and Rolls-Royce's Allison Advanced Development unit. The 10th member is business-jet fractional ownership company NetJets."- http://www.flightglobal.com/articles/2005/06/14/199485/paris-mach.html

http://www.aerioncorp.com/
http://www.saiqsst.com/
http://www.nasa.gov/centers/dryden/news/NewsReleases/2006/06-39.html

Braniff airlines operated a Concorde in 1979-1980 from IAD-DFW. It was restricted to subsonic flight.
http://www.concordesst.com/history/events/braniff.html
 

Hacker15e

Dunning–Kruger Observer
Can you feel a difference when you are going mach 1 as opposed to mach .95? I remember when I was a kid they had the "mach 1 experience" at a Six Flags. They made it feel as though the moment you went through the speed of sound everything got smooth as if all forms of turbulance was no longer an issue. I figured this was just their way to add to the experience but never really knew as i have never been mach 1+.
The best analogy I can make is that going super is like being up on the step/plane in a boat.

It is very smooth, but your maneuverability is significantly decreased until you get back subsonic -- much like when a boat gets back down off plane.

In the F-15, we start getting trans-sonic flow above .96Mach (IIRC, that is when we hit the Force Dynamic Mach Number and there is the dramatic increase in drag). When you go supersonic and are just going straight and level, you'll see the typical "bump" in the altimeter and VVI indicating that the shockwave has passed over the pitot boom and static ports.
 

NoSoup4U

Well-Known Member
Thanks a lot guys' for all the information. I'm reading a lot about it in the links given.

Also, it's incredible that people like Hacker15e can explain their real experiences with this type of thing. After I finish my schooling in 3 months, I am going to apply for a pilot slot in AF. I hope to be in a similar position someday. I still have to take the AFOQT and BAT.

Thanks again.
 

mjg407

Well-Known Member
The best analogy I can make is that going super is like being up on the step/plane in a boat.

It is very smooth, but your maneuverability is significantly decreased until you get back subsonic -- much like when a boat gets back down off plane.

In the F-15, we start getting trans-sonic flow above .96Mach (IIRC, that is when we hit the Force Dynamic Mach Number and there is the dramatic increase in drag). When you go supersonic and are just going straight and level, you'll see the typical "bump" in the altimeter and VVI indicating that the shockwave has passed over the pitot boom and static ports.
I was shaving with a mach 3........
high and fast is overrated...:eek:
 

Scandinavian13

New Member
The FARs restrict it, though it's not completely prohibited. That's not to say, however, that it's permissable for passenger carriage or point to point flights.

NJA_Capt, you're quoting AINonline over the FARs? They're just simplifying what the FARs say because the general readership wouldn't want to parse FARs - they just want to know for all intents and purposes, point to point supersonic flight isn't going to happen any time soon.





I don't see what the issue is here, though.
Are sonic booms really that loud if the aircraft is at altitude?

All of the reasons it is restricted seem to be pretty borderline.
The EPA probably came out with some ridiculous assertion that the boom would disrupt animal activity and throw species into extinction.
Homeowners would complain that, even though there are much longer, much louder disruptions all day, the sonic boom would be a nuissance.
Etc, etc...

Sonic booms from altitude wouldn't break windows and, from what I understand, sound like muffled gunshots.
Going from the reasons it's prohibited, should we then ban hunting seasons?
It kills animals and the sounds cause the same disturbance.

I could be wrong, however. I'm just going off of what I've been told.
 

Air 1

Well-Known Member
Come over here to southeastern TN if you want to get a taste of a sonic boom. I haven't heard it in a month or so, but for the last year or two you could hear and "see" a sonic boom 3 or 4 days a week. When I say see, you could look up and see two contrails with a small blip looking thing in the trail. (I'm guessing that had something to do when the aircraft went supersonic. In binoculars you could actually see the aircraft yanking and banking.) There were always two planes, and always went from the NE to SW. One of the news stations out of Nashville did some research and said it was F-22's doing testing out of Marietta, GA after they come off the assembly line. I remember reading online IIRC that the airspace stretched from about Crossville, TN to Scottsboro AL. After about 3 or more of these things a week I see why they don't allow a whole lot of booms just everywhere! I wouldn't be the least bit surprised if it actually did do some damage to things such as house foundations after repeated occurrences.
 

E_Dawg

Moderator
The few times the Space Shuttle landed at Edwards in the 90s the booms were quite loud, shook the windows a lot too.

But I really don't think the designers really cared about the boom, either
 
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