Forum: Civil and General Aviation

CrewDawg-Viper wrote:

Ok the simpilest answere is the FAA wont allow a civvie jet to be built with AB. Even the Concord which coulod go super sonic didn't have AB.

Just to add to JRs point, Concorde did have 4 afterburners added by SNECMA, Rolls Royce built the engine core. Concorde needed it`s afterburners to push up to Mach 1.7 or 8. After that she supercruised. Owed mostly to the slippery low drag shape and fancy variable engine intakes which contributed 64% of the thrust.

Concorde was the noisiest civil aircraft I have ever heard, what a beautiful sound! The plane was not allowed to go supersonic overland, only out over the ocean. They only used the burners for about ten minutes to get to just below cruising speed.

F-16.net Sponsor

Tyger, isn't Ross Perot Jr.'s T-38 an A model? I'm fairly certain the AF didn't bother updating a civilian's jet to "Charlie" standard. A little too much bling to spend on equipment that he'll never use (i.e., the updated equipment in the C model).

Oh yeah, the Collings Foundation either has (or had) an F-4D, which Gen. Steve Ritchie flew for a couple of years.

...and the Concorde?...DEFINITELY had an afterburner (4 of them to be exact)!! Wink

If you ever had the pleasure of seeing a Concorde take off, you KNEW it was the Concorde. D@mn thing sounded like a B-1 or SR taking off! Shocked

That is why only JFK would allow continuous Concorde operations; why Dulles bailed out for a few years, AND why DFW at first only allowed subsonic flights, and then left the program completely after just a few years.

Beers and MiGs were made to be pounded!

Quote:

If you ever had the pleasure of seeing a Concorde take off, you KNEW it was the Concorde. D@mn thing sounded like a B-1 or SR taking off!

I have a picture of the concorde (GBOAAG)? do a touch a go at oshkosh with AB goodness. Sometimes I think I can still hear it

Yeah, I saw the Concorde at Air Space America '88 just south of San Diego in Otay Mesa Very Happy

! They were offering "flights to nowhere" for a few hundred bucks - cruise half way to Hawaii and back at Mach 2 Thumb

! Of course, some doofus environmentalist protestor ran onto the runway in front of the Concorde while it was on short final and we got to see a full AB go around Devil

- that was awesome!!!

snypa777 wrote:

They only used the burners for about ten minutes to get to just below cruising speed.

The AB's are also used on take-off, but are shutdown soon after getting airborne. Seen the 'Speedbird' leaving LHR (London Heathrow) on many occasion with the burners on. Greatest site I've ever seen, especially at sunset! Very Happy

Still the best siting was 2 sitting side by side at LGW (London Gatwick) on a frosty morning getting ready for the Lapland run to see Santi Clause Wink

Yeah, just assumed everybody knew that! ABs on take-off, ABs off, clear land and the international limit over water(I think) or far enough away not to bother some old bloke down the pub` with a sonic boom, then ABs again to get to near cruise height and speed... Cool

Active Member Joined: Jan 10, 2005 - 07:58 AM Posts: 137

Hmm, so I've been reading this thread and now I'm wondering if you had the right nozzle pressure ratio, a really good T/W ratio, and on point intake design, could you have a supersonic aircraft that didn't require afterburner? Someone please say yes because if I ever get rich I'm building one and taking it 12 miles off the coast!

DesignAndConquer wrote:

Hmm, so I've been reading this thread and now I'm wondering if you had the right nozzle pressure ratio, a really good T/W ratio, and on point intake design, could you have a supersonic aircraft that didn't require afterburner? Someone please say yes because if I ever get rich I'm building one and taking it 12 miles off the coast!

Of course you can Very Happy

!!! As a matter of fact, it's already been done - it's called the F-22A Raptor Wink

. The only problem is that it costs over $100 million and the U.S. government won't let civilians have one - go figure Shrug

...

Yes, you would definitely want variable inlet and exit geometry (duh). If not, you'd have supersonic flow at the compressor entrace. Congratulations, you've just created an enormous supersonic diffuser. Its based on the Area-Mach relation and deals with nozzle flows. What you do is cause the inlet to be converging when going supersonic (this slows the flow down, again Area-Mach relation). You then have subsonic flow behind the throat of the entrance thing. You then make a really powerful engine (lets take the F136 core without the afterburner, 22,000 lbs) and stick that in something. Ok, you've got your thrust, you need to mess with it as it exits. This means making an ideal nozzle across all back pressure and engine conditions. So basically it needs to be adjustable and some what smart. This supersonic without afterburner has been done before. I believe the Raptor doesn't need burners to get supersonic (correct me if I'm wrong). If this is too much engineering, look up frontal pictures of planes and engines going supersonic and subsonic. The intake entrance look vary different between the two. I'm just wondering how the Raptor manages to do so much stuff with non variable inlet geometry. There's stuff you can do to drive it toward the sonic condition, but its hard to get it under and keep it under.

LordOfBunnies wrote:

This supersonic without afterburner has been done before. I believe the Raptor doesn't need burners to get supersonic (correct me if I'm wrong).

LordOfBunnies,

You're correct - public figures are about Mach 1.7 at 40,000 feet without burners for as long as you've got gas in the tank Thumb

!

Yeah, I know there are planes that can fly supersonic without the burners, but they have to use them to cross the barrier. The Concorde I believe had to do this I believe. I don't believe that can then be defined as supercruise because of it. Anyway, that word blows for a definitive word. The definition and the word have little to do with one another. The cruise speed (max range speed) of an aircraft (conventional, not counting ram, scram, turboram, and hybrid engines) will always be subsonic because things get funny above Mach 1. A lot of things reverse above that Mach number and it gets weird to deal with something that does subsonic and supersonic. Supercruise just means the plane go above Mach 1 without the use of burners. Nothing to do with the definition of cruise speed. See, going to class does a Bunnies good Smile

.

Just a couple of things...To get an aircraft to fly supersonic, you don`t require variable engine intakes. The F-22, JSF, all the Euro-canards have fixed intakes along with the Viper. The F-15, F-14 had fancy and complex variable intake mechanisms. Another way of controlling air flow is with bleed air systems.

The difference today is more advanced intake and engine design, especially around compressor blade shapes. Fixed inlets are cheaper, lighter, no moving parts means nothing to fail! Designers try to optimise intake shape for an entire flight regime. I think they used to be optimised for max` speed.

I suppose it includes controlling airflow into the engine. One neat way of diverting boundary layer air off the fuselage is on the JSF. It`s called Diverterless Supersonic Inlet, DSL. If you look at the engine intakes, there are two small bumps on the fuselage just forward of those intakes. They divert boundary air away from the intakes, along with the forward swept inlets themselves. I think it works in the same way as the diffuser on the Viper. If you look at the intake on the Viper, it is situated about 3 inches from the fuselage, this distance should equate to the boundary layer air thickness at max` speed.

On afterburners, Concorde would have had more range (not that it needed it) if it didn`t need ABs on take off. Somebody correct me here, wasn`t the Turkey one of the first jets that didn`t use it`s ABs on take off, F-14 B, D models? This would have significantly increased un-refueled range.

For me a supercruising aircraft is one that can stay at supersonic speeds without using afterburners. It doesn`t matter how they get there, it`s the ability to stay there that counts Wink

Although, if you can get there without using afterburners, you may not have to visit the tanker as much Very Happy

A small business jet with supersonic ability has got to be a winner, right?
Richard Branson and Billy Bob Gates have probably pre-ordered them!

snypa777 wrote:

Somebody correct me here, wasn`t the Turkey one of the first jets that didn`t use it`s ABs on take off, F-14 B, D models?

You're correct Smile

! The B and D Tomcats didn't use burner on carrier launches because they had enough thrust without them. I recall hearing a pilot at an airshow say that it seriously increased the jet's unrefueled range over a 'burner launch.

Snypa, those used to trip the flow in order to make sure its small and attached. The JSF then has inlets that are separated from fuselage. I think the trick with the newer planes is to get rid of the air energy. This may be accomplished by going around 2 right angle corners with more or less constant area. Anything else, you may get choked flow and then you have a problem. Air doesn't like right angle. The air may be heated when over M=1. This will actually drive its speed towards M=1. I don't make the rules I just follow them.

The concorde seemed to have turbojet engines, it actually might have been better with turbofans and just generate a normal shock in front of the engine. I need to learn more before I can make any judgements, but the concorde just seems like a colossally bad idea. Snypa, I'm pretty sure that the reason we differ on definitons of supercruise is solely because of the concorde. Smile

`Bunnies, if I got your post right...the idea of the JSF inlets is to try to keep boundary layer air, which sticks to the fuselage, from interfering with the shockwaves in front of the engine inlet cone? Is that about right? Your thought about slowing airflow seems ok, fixed inlets are stepped to accomplish the same thing I think. It will get rid of energy.

Concorde did use turbojet engines, but they had to use a complicated variable inlet config` to manage the mass-airflow in different flight regimes. An analogue system was used before a digital control sys` was fitted in 1972.
Here is a link to inlet design, if your completely bored! http://www.concordesst.com/powerplant.html It is a very good site for Concorde specs` and history.

The idea has, as Duplex has stated, been around for 40 years but Concorde was the first civil design to utilise it.....The intakes were able to adjust their total area, slowing the mass-airflow to one the engines could handle, as you know, engines don`t like supersonic air. Again on Concorde, the afterburning section was much longer than the engine core, evident on pictures.
The Olympus engine was developed beyond the Vulcan bomber for the cancelled TSR2 project, which was a supersonic tactical strike aircraft.

On supercruise, ya got me! Concorde did supercruise, but not like the Raptor!
The F-22 is probably the purer form of the phrase Cool

That`s all i`ll concede Wink

Forum: Civil and General Aviation

Afterburner