Sound Barrier Broken

[John Kim]

These are actual photos of aircraft breaking the sound barrier. This phenomena only happens at the instant an aircraft breaks the sound barrier and it literally appears like the aircraft goes through a wall.

Will a model jet aircraft break sound barrier some day?

-----------------------------

A naval veteran of 12 years, Gay, 38, manages a crew of eight assigned to take intelligence photographs from the high-tech belly of an F-14 Tomcat, the fastest fighter in the U.S. Navy. In July, Gay had been part of a Joint Task Force Exercise as the Constellation made its way to Japan.
Gay selected his Nikon 90 S, one of the five 35 mm cameras he owns. He set his 80-300 mm zoom lens on 300 mm, set his shutter speed at 1/1000 of a second with an aperture setting of F5.6. "I put it on full manual, focus and exposure," Gay said. "I tell young photographers who are into automatic everything, you aren't going to get that shot on auto.
The plane is too fast. The camera can't keep up."
At sea level a plane must exceed 741 mph to break the sound barrier, or the speed at which sound travels. The change in pressure as the plane outruns all of the pressure and sound waves in front of it is heard on the ground as an explosion or sonic boom. The pressure change condenses the water in the air as the jet passes these waves. Altitude, wind speed, humidity, the shape and trajectory of the plane - all of these affect the breaking of this barrier. The slightest drag or atmospheric pull on the plane shatters the vapor oval like fireworks as the plane passes through, he said everything on July 7 was perfect. "You see! this vapor flicker around the plane that gets bigger and bigger. You get this loud boom, and it's instantaneous. The vapor cloud is there, and then it's not there. It's the coolest thing you have ever seen."

[treehog]

Models doing the speed of sound with ordinary RC unlikely

the best unofficial figures i have seen on previous threads 420mph mack 0.5 with hot spot in Brazil South America at some jet speed fly in measured with on board GPS
average speeds in dives were 320mph and suddenly one was 420MPH so hard to say if its true but details srongly suggest it exceeded 380mph

It helps that Brazil modellers dont got stupid speed limits of 200mph that lot of countries have

If I ever get a hot spot I will have to go to that fly in

way to go

hopefully they will get around to using after burners to speed thing up even more

sorry florida toooooo slow only slow scaly freak show



The Scram jet model from USA milatary got mack 7 or 10 or something like that for ten seconds before crashing into pacific ocean

dont know if they got AMA insurance :D



to get speed of sound probably need a chase plane doing speed of sound and not live in airspeed restricted countries

Ralf

[downunder]

It's extremely unlikely that a model will ever get even close to Mach 1 especially near ground level. Even the fastest of military planes have trouble going much past Mach1.1 at ground level and that's with a couple of afterburning turbofans :D

I remember watching a Phantom do a low level high speed run over our base on a very humid day. All of a sudden the entire plane disappeared inside a white fuzz ball and stayed like that until he backed off...the coolest thing I've ever seen :)

[George99]

Cool pics, I don't believe that a model could ever cross the sound barrier either, except maybe for a model rocket, but that's another story.

[kdk]

those are cool pictures, i have all those and many more. but the vapor shock wave you see can be evident way below the speed of sound. when an a/c breaks the sound barrier it wont always do this. its all about the moisture level in the air and the temperature. the higher the humidity the easier this will happen. the picture you have up there of the f18, blue angels, was taken over the San Francisco bay, over a populated area, during a celebration flight. the aircraft at that time was reported to be doing approx 500 knots. in this country they cant and dont break the sound barrier near homes and people for obvious reasons. the pic pf the b1 was certainly not breaking the sound barrier, nor was the f14 pulling g's in that turn. but as the air accelerates instantly over the wing the air is going way faster then the aircraft and the sudden accel of the humid air causes the water vapor to vaporize and cause the vapor shock wave. you can also see this effect from an airliner, or other heavy high wing loading aircraft, comming off the wing tips creating vortices during landing and helicopter rotor blade tips, again during high humidty operations, which of course are going nowhere near the speed of sound. all thats needed is high speed and and lots of condensation over the wings. a quote from one of my aerodynamic manuals "Condensation is forming in visible clouds because a sudden pressure drop has cooled the air, bringing the air in that region to a temperature/pressure state where the water vapor condenses. The pressure over the wing, in particular is lower than the surrounding air and the molecules are actually further apart, not closer together. No "pushing" is going on. That's what you see the clouds form on the lee side of aircraft protrubences (like the canopy) or other areas where there is some flow separation, and not ahead of them - that's where the real compression of the air (pushing) is going on."
ill attach another pic of that f18 over the San Francisco bay, its screeming but not near mach 1. notice the boats nearby :)
i know this is way more then you wanted or needed to know about this subject, i was just in the mood to type :)

[Quacker]

You will like this one:

http://www.rcgroups.com/forums/showatt.php?attachmentid=752342&stc=1

[kdk]

your link isnt working

[Quacker]

It looks like it was taken down. There is no forum for: jet, full scale, breaking sound barrier, over water, right to left :>P

[kdk]

lol
lets see if there is a forum for an airliner breaking the sound barrier :)

[erbroens]

Well, it was only in the mach .5 flight (wich won the race) that I used full power on this plane..

About the 200 mph imposed in the u.s. I don´t think that is stupid at all, people there fly in much more cramped sites, near urban areas and perhaps keeping a speed limit could be the right thing to do... Just take a look at the FJ pics..

All I can say for now is that we are working in a faster plane for
the Curitiba Jet Speed Event in november 2006, and perhaps with a little luck
we could get closer to the magic mach 1 number .. ;)


Best regards, Enrique

[John Kim]

erbroens,

If a model jet is flown at near supersonic speed, it would be difficult to fly it by visual control from the ground.

It may require a cockpit visual device as used by the military on their unmanned aerial vehicles. Otherwise, you will easily lose sight of plane moving fast at such a high speed. Are we day dreaming?

[John Kim]

lol
lets see if there is a forum for an airliner breaking the sound barrier :)

We are sorry about demise of Concord for purely economic reason.

[erbroens]

Hi John, I believe that is possible. At 400 mph, a plane is doing about 180 meters/second
(our runway length in a little more than a second) and was quite easy to fly.. at mach 1, a ground speed of 360 m/s sound scary, but I believe that it is possible to control if the plane is big enough and if it is flown well away from the runway centerline.

Enrique

[kdk]

john, do you work for BAC ?

[John Kim]

kdk, yes I work for BAC. :p I think US denied Concord the landing right and US market out of jealousy, prompting its demise.

I believe still there is market for supersonic airliner catering to super riches or corporate executives and gov't officials to whom time is money.

[fatboywings]

I can't believe that the speed limit is 200mph in the states for jets. In CA they regularly do over 200mph with gliders.

Why do they put these bands on Jets and not gliders. To answer my own question, I would take a stab that anyone with enough money could go 200MPH with a jet, even an idiot newbie going full throttle on takeoff. Gliders on the other hand, no newbie is going over 150mph+.

Maybe instead of imposing a speed limit you should talk about introducing liscencing for going faster and faster, just a thought.

Really cool pics, I have seen this vapour thing happen at Indy on the Gold Coast in Australia. Quite impressive but no need for supersonic speed at all if there is rain. I think they would have been lucky to crack 200knots and they were a ball of vapour. really cool though.

[kdk]

the speed limit in the us is not 200 mph, its 250 kts (288 mph) below 10000 feet msl. this applies in other countries as well.

the 200 kt limit (230 mph) is imposed within 4 miles of an airport and below 2500 feet.

and this applies to ALL aircraft, not just jets, even gliders. ill quote the faa regs: "Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.)."

in the usa this can be waived in a few cases, such as the minimum speed at which an airplane needs to fly and maneuver safely such as a 747-200/300 which performs better at V2+100, or 285 kts. they simply advise departure control "speed 285 for performance" or equivalent sentence, they know what it means.
If it is not approved, they have to climb out and maneuver with flaps at 230 kts max till reaching 2500 feet, then 288 kts till 10000 feet.

the speed limit is there for good reasons. you wouldnt want a 747 doing 400 kts in the same airspace as the private pilots, student pilots, helicopters and gliders etc. its just managing risk. not many light aircraft are flying above 10000 feet and aircraft that are flying over 10000 feet are usually on a flight plan and being watched by atc, who can see whats going on and control everyone. below 10000 feet is where the students, slow aircraft, low time pilots etc operate. we cant have them doing over 250 kts can we ? :)

[fatboywings]

kdk,
thankyou for the great detailed response. In Australia it is forbidden to fly an RC plane or glider or even a kite within 5km of the airport.

Are you saying that people flying further than 4 miles from an airport below 10000' at speeds greater than 288mph are breaking the law in your country. If so wow! what a crazy world we live in.

regards
Ben

[causeitflys]

kdk, the 200 mph speed limit refered to is the AMA imposed limit for model jets. I don't think the discussion meant full scale aircaft.

[Munkey]

I think once a metal less vulnerable to heat and stress fatigue is synthesised there will be supersonic airliners again. The main problem with concord was when the aircraft was doing mach 2 even in the thin air the aircraft's skin was at 100 degrees celcius and the aircraft grew by a couple of inches while in flight aswell as the stress from pressurisation so once the structure gives up the ghost it would cost a s**t load of money to fix. I cant wait until they re-intoduce nuclear engines (america and russia had prototypes of them) though.

[treehog]

All I can say for now is that we are working in a faster plane for
the Curitiba Jet Speed Event in november 2006, and perhaps with a little luck
we could get closer to the magic mach 1 number ..


Best regards, Enrique



Thanks for joining in from sunny brazil

so is the new message is eat my fumes:D

yeah the 200mph limit is for most countries is a club imposed rule for insurance cover reasons that seems to exist in Northern hemispher countries
but hasn't found any support in the latin quaters of the planet ;)

Hell the italians built cars without brakes cars are meant for going
not stopping :D

I personnaly will save up to get hot spot type craft to try to get full bore dive speeds exceeding 320mph as soon asthe bank will lend me the money for my new buisness scheme..... ultra fast planes INC :D

There is no reasons to stop most modelers in most countries with relevant ATC permissions to exceed 200mph but most jets are scale jobs and are not meant to or able to go ultra fast so will require the correct jets

So like DS it will be a out in the sticks sport enjoyed by a few and shunned by the scale jet meets and probably in nevada desert without AMA insurance
watch out cayote the road runners got a after burner :D beep beep :D



To get speeds of mack 1 well thats a tall order suspect after burner and gobs of J1 and engine run times of 60 seconds plus a few JATO strapped on for luck....and good eye sight


even so there can be few sports that can give sub mack 0.5 for such a few thousand $$$$

busy saving up

Ralf

PS
the max speed for GPS is 999.99mph
so they cant be used buy the baddies for missile guidance systems
unless the new Euroland GPS system dosnt impose similar restrictions ;)

[treehog]

Concord lovers get a grip on the reality
The concord was way past it sell by date
It was the most dangerous airliner staticaly on the planet to fly on
It was late 60's tecknoligy
It was involved in several very close crash situations and the warning signs were there for anybody to see to call a halt to it flying

and it was so noisy as hell

and worst it got less than 10 miles to the gallon per passenger mile equavalent
or used 4 to 7 times as much fuel for each passenger mile as compared to a modern airliner

It was a symbol of its time and as many other symbols were laid to rest like USSR it should have been retired in 1995 at the latest rather than struggle onto a predicable crash

So in keeping with praise where praise is due the abilty to send 120 passengers at mack 2 in the 1970's to 1980's was excelent

The ability of British Airways and AIR FRANCE not to see the writting on the wall by the late 1980's nearly unforgivable

When the craft were made theyy expected them to be scrapped by mid 80's at the latest

Ralf

[treehog]

Ah the good old days where jets were full bore in your face at the local horse racing track before the big crashes in germany which ruined all the fun

yeah in those days the planes 4 phantoms 5 f11 4 f15 and 4 slow hogs came past one by one fivety feet up and some 100 feet from the horse show stand at full tilt and on passing would fire up the after burners sometimes before passing and sometimes after passing the stands

They all cranked full up after passing and went to 20.000 plus feet in seconds and they all had the water vapour affect hanging on the wings with the climb out

That was fun

but unless your a gook getting swatted or in the milatary you wont get to see that anymore for safety reasons

RALF

[erbroens]

Thanks for joining in from sunny brazil

so is the new message is eat my fumes


Absolutely no! the message is come here this year and join the fun! :)


about the airshows, it is good that they are now safer and have more regulations.. (nobody wants another Ramstein kind of accident again) but for the true enthusiast delight anyway, pilots are pilots and they will always zoom the tower at the proper time anyplace... :D

Enrique

[Ballistic]

Now that's a pretty shot.

[treehog]

definitly unlikly this year as saving up to get turbine plane first
The next year might be possible if I can get a hotspot onto a airliner to brazilia
ahhhhh 12 hour flight that sucks where are these hypersonic airliners

I have seen people get on planes with surfboards canoes bycyles Tuba
giant violin things Viola so figure it should be possible if I make a triangle box and put it into oversize luggage

Me I would never save to get a turbine that does 200mph as for a lot less an electric will do that speed but the ability to exceed 300 or 400 mph without the 150db of the pulse jet
thats worth the extra money
hope to be at Brazil show race in 2007-2008 but only to fly fast
but I wouldnt expect to win with standard gear
compared to the others with JATO and afterburners etc

Like the photo

Oh yeah we dont want accidents but they should let the real cult duds be closer in your face close up like the good old days
and the ordinary spectators further back in the car park or similar

Saw a mini airshow in Greece with Greek milatary flying past the towns marina twenty feet of the water in phantoms just to impress the local gal he was dating

You want to see the hand brake turn a phantom does when a big sailing yaught decided to reverse out from its berth not knowing phantom was coming in for another umteenth run
I suspect brown window syndrom was the reason they didn't continue the show
The next week when the local gal dumped one of the pilots the repeated afterburner loops over the main street at 6am didn't impress the villagers sleeping off thier hangovers
Hell hath no wrath as a jilted Greek airforce pilot :D


Ralf

[Sluf7]

The Germans have already done the the After burner thing and the fuel ya need to do it a model would run outa gas.

I also understand under AMA rules no Afterburing Jets are allowed in the Good Ole U.S.of A

[downunder]

That F111C in the photo above is A8-131 and I think it's doing a low level run over Surfer's Paradise during the Indy car race. If you look at the large photo you can just see a bit of the fog over the top of the wing. For the gas turbine enthusiasts have a look at the exhaust nozzle. That's actually a thrust augmentor hanging out the back that's independent of the engine nozzle and has a variable opening that's controlled only by aerodynamic forces and exhaust pressure, no actuators. :D I haven't flown in that one (although I've changed and run many engines in it) but I've been in 137 and 142. And a lot faster than 250 knots at 300 feet :)

[causeitflys]

Could you give a little more detail as to how the augmentors work? I've wondered about them.

[downunder]

Augmentors work by using the exhaust velocity to draw in extra air to be mixed and heated to add thrust over and above what you'd get normally. It's not a new idea but the only application I've ever seen with models is with the old Jetex rocket motors. They had an optional augmentor tube which had a large bell mouth opening at the front where the Jetex unit fired it's exhaust gasses into and venturi action drew in extra air. This added mass of air provided the extra thrust.

In the photo of the engines in the F111 you can see the actual moveable engine nozzles. The one on the left is as the nozzles are all the way from just above idle to full military power. The one on the right shows the nozzle in the full open position which is where it is at idle (to dump thrust) and at full afterburner. Both augmentors are in the fully closed position but they can be pushed open by hand (with some difficulty :)) to give an exit area maybe double what it has when closed but this doesn't happen until very high Mach speeds.

What can't really be seen in the photos is that the inner surface of the augmentors right by the engine nozzles is curved like a venturi and the outer diameter basically just follows the the lines of the fuselage so it's not really sticking out in the slipstream. Because they only use exhaust velocity they're working even with the aircraft stationary or on the takeoff roll.

I honestly don't know why they haven't been at least tried with model gas turbines because they don't add anything to fuel consumption and maybe not even to drag. For a model they could be made extremely light like the ones for the Jetex units.

I hope that helps.

[causeitflys]

Thanks Downunder...
Interesting, I didn't know they were independent. Any idea how much they actually augment? It must be significant but only worth the effort on certain airframe /engine combinations.
Yes, I had a few of the Jetex engines. Now there was some serious thrust :rolleyes:
As for model turbines using this, any plane with a pipe and especially ones using a bypass are doing the same thing, but not very well. The only reason for the model pipes is to get the exhaust out the back of the plane. I always thought the pipe makers were missing the boat on this because most cause a loss of thrust. The only one I'm aware of that adds extra thrust is the Wren pipe. But I guess the losses could be worse so maybe they are doing the job.

[downunder]

It's impossible to know how much they augment the thrust because obviously you can't run the engine without them :). I'd think maybe only Pratt and Whitney would have the figures from when they developed it. Interestingly though, the F14 Tomcat doesn't have the augmentors even though originally it used much the same TF-30. However, the F111 is considerably faster than the F14.

[Antonsoarer]

An old thread on a similar subject: :)

http://www.rcgroups.com/forums/showthread.php?t=362140

and how about this for a low pass!!! (just hit refresh to see it again) :cool:

http://www.negative-shock.net/view-204

Tony.

[downunder]

More on augmentors, and it's funny how one thing leads to another. I followed a link given in the Rednecks and Jets topic and in http://www.aardvark.co.nz/pjet/ there's mention of adding an augmentor to his pulse jets which he guesstimates will up the thrust from 180 to 220 pounds or 22%. Then if you go to http://www.aardvark.co.nz/pjet/pjafterburner.shtml he's added an augmentor but also converted it to an afterburner. That's a really neat bit of lateral thinking because it means you don't need an adjustable nozzle if you do that with a gas turbine :)

[Twizter68]

Actually, the B1 was breaking the sound barrier. The difference in the vapor formations indicates whether or not the barrier has been broken. The Tomcat was not at mach, which is evident by the irregular and wispy vortex trails over the wings and fuselage. When an aircraft breaks the barrier, it forms (if you are looking at it from directly in front) an almost perfect circle of condensation. Most can't do it at ground level, due to air pressure, etc., but the B-1 is one that can (you gotta love four 110's in zone 5 burner!)

[Old Fart]

lol
lets see if there is a forum for an airliner breaking the sound barrier :)

Hell, every heavy leaving 25R at LAX iwhen we have any level of moisture in the air must be supersonic then :)

(I work for LAX - guess where my window looks) :)

[Boomerang1]

I honestly don't know why they haven't been at least tried with model gas turbines because they don't add anything to fuel consumption and maybe not even to drag. For a model they could be made extremely light like the ones for the Jetex units.

Actually augmentor tubes are used in all turbine models with enclosed engines. They do increase thrust by a small amount but the main reason is to suck cool air in with the exhaust gas to lower the temperature of the pipe. Further to this you have 'double wall jetpipes' on turbine models. On these the outer tube is open both ends and is slightly longer (10mm typical) than the inner tube. The venturi effect of the gasses squirting out the inner pipe draws cool air between the inner & outer pipe so that the outer pipe (mine is just litho plate) is barely warm to touch. Not bad considering the exhaust gas temps can be more than 600 deg C! - John.