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Can Supersonic Fly-by Effect Another Aircraft?  
User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Posted (12 years 1 month 1 week 1 day 17 hours ago) and read 3673 times:

This is going to be a repeat topic from something I posted in Tech Ops, I got almost 1000 views and no replies, maybe it might be better to ask you guys...


I remember reading a UFO story about a 747 crossing the Atlantic and both pilots reported an object on radar was coming right at them pasted M2, it passed underneath the 747 by about a thousand feet. They braced for a soft sonic boom from the object, which never came.

Let's say 'it' was Concorde, I'm sure it's happened before under different conditions. Is there any interaction or effect at all between the two vehicles?

If you guys don't know, at least tell me, otherwise I'll attempt to venture into the Military forum with another iteration of this post.



The meaning of life is curiosity; we were put on this planet to explore opportunities.
14 replies: All unread, jump to last
 
User currently offlineConcordeBoy From , joined Dec 1969, posts, RR:
Reply 1, posted (12 years 1 month 1 week 1 day 16 hours ago) and read 3645 times:

This (if it happened to be a Concorde) would be both extremely unusual and dangerous.... remember that a Concorde's typical supersonic cruising altitude is between 50000 and 60000ft, whereas a 747's is in the realm of 30,000 (almost half).

Flying at M2.02 at an altitude lower than 40,000 would place enormous stress on the airframe of a Concorde, and would never be done intentionally.


User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Reply 2, posted (12 years 1 month 1 week 1 day 16 hours ago) and read 3628 times:

Okay, if 'it' was Concorde, this would a BIG AS HELL IF.

But IF it happened, what effect of the shock wave would the 747 experiences? Concorde, like you said for example, flies at 60000ft and a 747 at 40000ft, the 747 would feel a boom. We sure would at sea level, so it could be more intense being 20000ft away, right?

Take the original incident; whatever 'it' was came no closer than a thousand feet away, according to the pilots. What kind of shock impact could have occurred?



The meaning of life is curiosity; we were put on this planet to explore opportunities.
User currently offlineMD88Captain From United States of America, joined Nov 2001, 1338 posts, RR: 20
Reply 3, posted (12 years 1 month 1 week 1 day 16 hours ago) and read 3619 times:

I don't know the answer, but I remember being warned by a controller over northern France that the Concorde was passing above and from right to left and was accelarating to mach +. He thought we might get "thumped" (which is my word not his). We never felt a thing but it was very cool to see.

User currently offlineBellerophon From United Kingdom, joined May 2002, 585 posts, RR: 59
Reply 4, posted (12 years 1 month 1 week 1 day 13 hours ago) and read 3581 times:

Concorde can't fly anywhere near Mach 2.0 at 40,000 ft.

The radar in a B747 is there for weather avoidance, and will not give you any idea of the speed of another aircraft, even if you do manage to detect it, which is highly unlikely anyway.

Concorde does not fly level whilst supersonic, she cruise/climbs, and so ATC do not issue clearances that involve flying underneath other aircraft whilst in supersonic flight.

Sometimes, to the South of Ireland, during the early part of the acceleration on a Westbound flight, Concorde flies over subsonic traffic that is arriving from the USA and cruising around FL370-FL410. If close to this traffic, by which I mean 10-15 miles, then ATC will often warn them that they may be "boomed" as the shock waves pass over them.

From the reports I've heard from some of these crew, this can vary from nothing to a clearly audible double boom, but nothing to cause any concern or alarm.

If a B747 had another aircraft at Mach 2.0 pass one thousand feet directly underneath them, they would most definitely hear it.

Regards

Bellerophon





User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 5, posted (12 years 1 month 1 week 1 day 4 hours ago) and read 3519 times:

A Partnair CV-580 crashed just off the coast of Northern Denmark in Sep. -89.Just moments before,an F-16 had passed close by at M. 1+ and one theory maintains that the "bump" started vibrations in the horizontal stab. which disintegrated.


"Luck and superstition wins all the time"!
User currently offlineBroke From United States of America, joined Apr 2002, 1322 posts, RR: 3
Reply 6, posted (12 years 1 month 1 week 1 day 1 hour ago) and read 3477 times:

The CV-580 crashed because of an inflight structural failure which was affected by the use of substandard structural hardware in a repair. The fasteners were marked frauduently marked as meeting aeropsace standards, but were not.
During the Berlin Airlift in 1947-48, the transports supplying Berlin were buzzed in head-on passes by Soviet fighters at very close quarters. Even though these passes were not made jet at M 1+, they did upset the transports some. Happily none were lost due to these antics. I would think a supersonic pass at close quarters could upset a smaller airplane. Larger airplanes like 747's would feel it, but probably not be knocked out of control.


User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 7, posted (12 years 1 month 1 week 22 hours ago) and read 3449 times:

Yeah,substandard repair practice was the reason disintegration took place.However,tests have been performed that indicates disintegration could not take place without some other impetus from outside,setting up a vibration or flutter.It is in this view that the F-16 fly-by may have triggered the chain of events.


"Luck and superstition wins all the time"!
User currently offlineBravo45 From United States of America, joined Sep 2001, 2165 posts, RR: 11
Reply 8, posted (12 years 1 month 1 week 16 hours ago) and read 3392 times:

The radar in a B747 is there for weather avoidance, and will not give you any idea of the speed of another aircraft, even if you do manage to detect it, which is highly unlikely anyway.
This is something that came to my mind as well. When did this happened? Or do you have a link?
Secondly, I think that I have not understood your question properly. There are two things that might come under the explaination of effect, a sonic boom that can be heard. If you hear it, just as you may on the ground when an airplane breaks the sound barrier, it will only be the sound of it. No feel and so same in the air. If an airplane breaks the sound barrier miles away from you, what you may get would be its sound and no feel.
Aircrafts flying close to each other are effected by one way, their vortices and wake turbulance. And to feel the effect of that you or the other or both aircrafts needs not to be supersonic. Suppose one is just as in this case, firstly, the sonic boom is ONLY heard when the aircraft crosses Mach1 and thus normal noise of the engines afterwards. So you wouldn't hear a sonic boom if you pass a concorde that has been flying supersonic for an hour.
The other thing, being effected is related to the distance of the two airplanes, in this case you say it was vertically one thousand feet. Certainly an airplane will create more turbulance behind it when its subsonic than when its supersonic. But to be effected by that turbulance you need to get "hit" by it. That is when you fly through that tubulance from the other aircraft. And to be able to detect where that turbulance would be, you need to know a few factors involved. Forexample wind, wind takes the effect of tubulance in its direction as the turbulant area keeps on getting larger and thus weaker until it finally dissapates.
Final word: In order to get effected by this turbulance, you need to fly through it when it strong enough to effect your airplane. A 747 might not have the slightest of feel while flying through an area of turbulance as compared to a C152 shaking badly when flying through the same area (meaning an area equally turbulant).


User currently offlineBellerophon From United Kingdom, joined May 2002, 585 posts, RR: 59
Reply 9, posted (12 years 1 month 1 week 13 hours ago) and read 3298 times:

Bravo45

So you wouldn't hear a sonic boom if you pass a concorde that has been flying supersonic for an hour.

Wrong.

firstly, the sonic boom is ONLY heard when the aircraft crosses Mach1

Wrong.

Certainly an airplane will create more turbulance behind it when its subsonic than when its supersonic.

Wrong.

Regards

Bellerophon


User currently offlineBravo45 From United States of America, joined Sep 2001, 2165 posts, RR: 11
Reply 10, posted (12 years 1 month 1 week 13 hours ago) and read 3292 times:

Dear Bellerophon!
Please correct me through explaination.


User currently offlineBellerophon From United Kingdom, joined May 2002, 585 posts, RR: 59
Reply 11, posted (12 years 1 month 1 week 11 hours ago) and read 3246 times:

Bravo45

The shock wave, caused as an aircraft passes through the speed of sound, remains attached to the aircraft as long as the aircraft is supersonic. Its position relative to the aircraft will change as the aircraft Mach number increases, but it is always there.

It doesn’t matter how long the aircraft has been supersonic, the shock wave stays with it, and if it passes over you, your ears will detect the sudden pressure change as the sound we call the boom. Actually it will probably be heard as a double boom as there are two main shock waves, the bow wave and the tail wave. How loud the boom seems to you will depend mainly on how close you are to the aircraft at the time.

At very low supersonic speeds the boom may not reach the ground, and occasionally during turning or decelerating flight the boom can appear stronger at some points on the ground than others, but, unfortunately, it is always there. This is the main reason that most, but not all, countries have banned overflight by civilian aircraft at supersonic speeds.

The turbulent wake an aircraft leaves behind it varies with several factors. It is true that, for various reasons, a subsonic jet may well generate more turbulence on approach, when it is flying slowly, than it does in cruise, when it is flying faster.

This does not mean that when comparing the amount of wake turbulence caused by two different aircraft, flying at vastly different cruising speeds, one subsonic and the other supersonic, that you may assume that the faster aircraft will cause less turbulence.

Concorde will be travelling around two and a half times faster than the subsonic jet and will cause substantially more wake turbulence. If you want to believe otherwise, feel free.

Regards

Bellerophon


User currently offlineBravo45 From United States of America, joined Sep 2001, 2165 posts, RR: 11
Reply 12, posted (12 years 1 month 1 week 7 hours ago) and read 3072 times:

I quote myself here again:
Certainly an airplane will create more turbulance behind it when its subsonic than when its supersonic.
I obviously was talking about the same aircraft in the SAME weather conditions. That I took it for granted might be called a bad explaination from my behalf but I though that it was obvious from the way I wrote.

While having the commercial aviation as my primary interest and not being a great fan of the concorde, I don't have all that much knowledge about sonic booms and that it remains attached to the airplane is something new for me. Can you please provide a link that explains the process??

Its not believing what anyone feels like. Atleast not for me. I like getting myself corrected and the views that I have should they be wrong.

Reagrds,
Bravo45.


User currently offlineBellerophon From United Kingdom, joined May 2002, 585 posts, RR: 59
Reply 13, posted (12 years 1 month 1 week 2 hours ago) and read 2927 times:

Bravo45

Let me quote you again

Certainly an airplane will create more turbulance behind it when its subsonic than when its supersonic....I obviously was talking about the same aircraft in the SAME weather conditions.

No it won’t. Let me repeat again, you are still wrong.

Don’t confuse the situation on take-off or on final approach (which are generally the areas of most concern to pilots, and the areas that have received the most research) with what happens in cruise.

As for links, why not do your own research on the internet? Try typing Sonic Boom or Wake Turbulence into any good search engine, and you will get more information back that you can deal with.

Just to get you started, try any of these links.

  • http://www.dfrc.nasa.gov/PAO/PAIS/HTML/FS-016-DFRC.html

  • http://www.sky-flash.com/boom.htm

  • http://www.gmi.edu/~drussell/Demos/doppler/doppler.html

  • http://nasaui.ited.uidaho.edu/nasaspark/safety/basic/thrust.html<?LI>
  • http://www.tech.purdue.edu/at/courses/at479/_private/chapters/wake_turbulence.htm

  • http://aviation-safety.net/events/wxx.shtml


  • If I may make a suggestion, if you do not fully understand a subject, it would be better to avoid making rash and incorrect statements about it, which may mislead others, and instead to phrase your post as a question. That way you are more likely to receive the explanation you seek.

    Trying to pass off ill-informed comments, like some of those in your earlier post, as fact will impress nobody, and merely invites the sort of blunt reply you received.

    Regards

    Bellerophon


    User currently offlineBravo45 From United States of America, joined Sep 2001, 2165 posts, RR: 11
    Reply 14, posted (12 years 1 month 4 days 18 hours ago) and read 2729 times:

    Dear Bellerophon,
    While yet to make a search on my own and to see the links that you have posted, I apologise to all viewers of this thread for being so wrong. I don't make much statements on this forum that are dealing with such topics because there are way too many better informed people here that solve almost all problems brought up here. Those were just my two cents here on this topic and the reason why I interferred here was that I didn't see the people posting here things that appeared to me as explaining the topic in a very clear detail. My bad, I should have written that I am not sure if I am correct but I ofcourse posted that to read the comments on my thoughts on this topic and things are now more clear though not in a very appreciating manner. I also have to say that this is not my usual way.


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