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View Full Version : OT: Why is the harrier subsonic.



Thanatos833
01-04-2007, 07:47 AM
You'd think if it had such a powerful engine for the time and a thrust to weight ratio which makes it a VTOL it would have enough grunt to go supersonic. Unless it's design created an unbelievable amount of drag, which I doubt.<div class="ev_tpc_signature">

http://img88.imageshack.us/img88/9285/do17in9.jpg

The Dornier Do-17, another brilliant example of German engineering, a ?Schnellbomber" which could just outrun all fighters, this plane led to the German victory in the Battle of Britain and indeed, the Second World War.

Capt.LoneRanger
01-04-2007, 07:57 AM
Simple: because the engine and the jet itself is not design for that. The Harrier uses vectorized thrust for hovering and VTOL. The same nozzles are used for forward propulsion, too. No wonder they do not push the Harrier to supersonic. With the same reasoning, you could ask why the 3000PS heavy-duty-trucks are not used for Formula 1-racing, though their engines are far superior.

Overall, there are not many planes that reach supersonic speeds with MIL-throttle only in level flight, most rely on afterburners, which the Harrier does not have for obvious reasons.<div class="ev_tpc_signature">

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Ugly_Kid
01-04-2007, 08:16 AM
Lack of afterburner and the nozzles are also not up to providing supersonic thrust.<div class="ev_tpc_signature">

http://www.f19vs.se/fokker_now.jpg

DuxCorvan
01-04-2007, 08:20 AM
As said. No afterburners.

W/o afterburner no plane reaches supersonic speeds -except for the late ultramodern F-22 and EF Typhoon which have supercruise abilities.

Anyway, the vectorized jets in the Harrier hardly would fit afterburners, and SVTOL operations are very fuel-consuming. The small airframe of the Harrier -it's a really tiny jet compared to other types- would unlikely contain all the fuel necessary for afterburning (which 'drinks' fuel at an incredible rate), having a minimum range and carrying a useful payload.

On the other side, it is not necessary: supersonic flight is intended to arrive 'soon' to the combat zone and have an early intercept. Harrier compensates for this by being able to operate from short strips, made by engineers near the frontline, not depending of carriers nor having to travel long distances from large airbases.

Why do you think SVTOL fighters were invented?

HellToupee
01-04-2007, 08:35 AM
Originally posted by DuxCorvan:
As said. No afterburners.

W/o afterburner no plane reaches supersonic speeds -except for the late ultramodern F-22 and EF Typhoon which have supercruise abilities.


dont forget http://upload.wikimedia.org/wikipedia/commons/4/44/Lightning.two.750pix.jpg

DomJScott
01-04-2007, 08:35 AM
Not true Dux.. Supercruise has been around for decades..

The first aircraft to supercruise was the EE Lightning. Also the TSR-2 was supercruiseable along with the Concord, Mig 25 and others.

As for the harrier..

They where developing a supersonic variant which included what they called PBC nozzles. Basically they effectivly afterburned the FRONT nozzles which are actually vectored air off the main fan
http://en.wikipedia.org/wiki/Hawker_Siddeley_P.1154

Thanatos833
01-04-2007, 08:42 AM
3000PS heavy-duty-trucks are not used for Formula 1-racing, though their engines are far superior. Aren't the trucks very heavy though?



supersonic flight is intended to arrive 'soon' to the combat zone and have an early intercept. So it isn't useful in combat?

Isn't the purpose of an afterburner to increase the thrust to weight ratio to a point where the plane can fly faster, assuming the harrier is about as aerodynamic as the average fighter the thrust to weight ratio of the harrier being higher than many other other fighters , even without an afterburner should allow it to supercruise shouldn't it? I thought all afterburner do is add more thrust, unless they do something else I don't know about which helps in supersonic flight, I should think thrust is thrust, no matter how it is produced.


The first aircraft to supercruise was the EE Lightning. Also the TSR-2 was supercruiseable along with the Concord, Mig 25 and others. Not to mention the SR-71. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif<div class="ev_tpc_signature">

http://img88.imageshack.us/img88/9285/do17in9.jpg

The Dornier Do-17, another brilliant example of German engineering, a ?Schnellbomber" which could just outrun all fighters, this plane led to the German victory in the Battle of Britain and indeed, the Second World War.

DuxCorvan
01-04-2007, 08:56 AM
Originally posted by DomJScott:
The first aircraft to supercruise was the EE Lightning. Also the TSR-2 was supercruiseable along with the Concord, Mig 25 and others.


AFAIK those aircraft could *maintain* Mach 1+ w/o afterburners, but could they *reach* Mach 1+ at level flight without them? Not argumenting just asking. http://forums.ubi.com/groupee_common/emoticons/icon_confused.gif


Originally posted by Thanatos833:
quote:
"supersonic flight is intended to arrive 'soon' to the combat zone and have an early intercept."

So it isn't useful in combat?

Very much. But not if your fighter-bombers operate right by the operations area. They take-off very near from target, they don't need to travel too fast to arrive on time, so they can save fuel and carry more weapons with a small aircraft.

SVTOL may not be so fast, but they have many advantages:
1) They can operate from hidden ad-hoc short strips built in hours near the area where tactical support is needed.
2) They can operate from very small CVs and still being an able menacing/defending force.
3) They can survive and even operate if airbases are destroyed.
4) In case of emergence, they can land on the top of your roof -if it is plain enough.

All those capabilities compensate for supersonic speed. Anyway, if the late projects go ahead, we could have a supersonic SVTOL multirole fighter in some years.

whiteladder
01-04-2007, 09:06 AM
aerodynamic as the average fighter the thrust to weight ratio of the harrier being higher than many other other fighters , even without an afterburner should allow it to supercruise shouldn't it? I thought all afterburner do is add more thrust, unless they do something else I don't know about which helps in supersonic flight, I should think thrust is thrust, no matter how it is produced


Quite true, but supersonic flight isn`t just a matter of having enough thrust. Most jet engines (especially high bypass turbofan like the pegesas in the Harrier) don`t work very well if the air entering them is moving fast than the speed of sound. That`s why supersonic aircaft have ramps or cones in the inlets to reduce the speed of the air flow.

The design of the harriers inlet is specifically design for best performance in the hover i.e. zero airspeed. As the aircraft approaches the speed of sound the thrust the engine produces decreases, it can break it in a dive only.<div class="ev_tpc_signature">

http://img513.imageshack.us/img513/5248/whiteladder4ws6pf.jpg (http://imageshack.us)

AWL_Spinner
01-04-2007, 09:18 AM
Pretty sure the EE Lightning could accelerate through Mach 1.0 without use of a/b back when men were still riding Penny Farthings, or whenever it was. And the term supercruise gets bandied about like it's a new thing!

But I digress, as to the Harrier, it's not supersonic for all sorts of good reasons mentioned thus far, and the optimisation of it's intakes and nozzles for the low-level, subsonic combat operations.

You can't have supersonic air hitting the front compressor of your jet engine, which is why supersonic jets have those fancy variable geometry ramps. Which take room, and weight, and for a little jet like the Harrier which requires a T/W radio of over 1:1, those are important things and the first to be dispensed with if such performance is not required.

There was a supersonic version in the works, the P.1154, back when merry England had an aeroplane industry, try here (http://www.harrier.org.uk/history/history2_3.htm). So V/STOL and supersonic performance are not necessarily mutually exclusive, it was just never developed as the requirements never really overlapped.

P.1154


http://www.harrier.org.uk/history/images/p1154b.JPG <div class="ev_tpc_signature">

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XyZspineZyX
01-04-2007, 09:32 AM
If you look at the Harrier, you can tell its a design that is unsound for supersonic. The gigantic air intakes and the all to visible fan blades in the intakes would mean that the Harrier is unable to go supersonic without a major redesign of these parts. If you look at the picture posted above, you can see the intakes are redesigned to allow subsonic airflow to the engine. Also, the thrust nozzles basically prohibit the implementation and use of an afterburner system.<div class="ev_tpc_signature">

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DomJScott
01-04-2007, 09:46 AM
@Dux

Yes I think most could pass Mark I without AB's.

I THINK the concord only used it at takeoff.

Certainly the lightning could and 99% sure the TSR2 could too.

NonWonderDog
01-04-2007, 09:54 AM
Originally posted by Thanatos833:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The first aircraft to supercruise was the EE Lightning. Also the TSR-2 was supercruiseable along with the Concord, Mig 25 and others. Not to mention the SR-71. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif </div></BLOCKQUOTE>
Nope, not the SR-71. It uses afterburners until Mach 2+, then it switches off the turbofans. The afterburner then becomes the main burner, turning the engine into a ramjet. That's not the same thing as supercruise at all.

In turbofan config, the SR-71 does need its afterburners to take off and to break Mach 1. In fact, the afterburners are the only limit on maximum range assuming in-air refueling; it takes a charge of a special low-flashpoint fuel to start the afterburners each time, and the SR-71 only has enough of this fuel for 16 or so afterburner starts.

Well, it doesn't actually turn the turbofans off, but it chokes the compressor airflow and throttles down the turbofan burners. At Mach 3 almost all the thrust is coming from the ramjet portions of the engines.


You limeys (and our leathernecks) are getting a supersonic STOVL soon, though, with the JSF. It's really every bit as VTOL as the Harrier ever was...which means it's not. Both the Harrier and the JSF need a hundred feet or so to take off if they've got fuel and a pilot on board, not to mention ordinance.

Thanatos833
01-04-2007, 10:19 AM
How hard is it to put a cone on the intakes?


Very much. But not if your fighter-bombers operate right by the operations area. They take-off very near from target, they don't need to travel too fast to arrive on time, so they can save fuel and carry more weapons with a small aircraft. No, what I meant to ask was how useful is speed, when the planes are within effective AAM range of each other? By effective I mean at a range where you have a good chance of getting a kill as AAM's are not very accurate at the edge of their range.<div class="ev_tpc_signature">

http://img88.imageshack.us/img88/9285/do17in9.jpg

The Dornier Do-17, another brilliant example of German engineering, a ?Schnellbomber" which could just outrun all fighters, this plane led to the German victory in the Battle of Britain and indeed, the Second World War.

Viper2005_
01-04-2007, 10:35 AM
Concorde used reheat for transonic acceleration.

***

P.1154 might well have been somewhat marginal in certain respects since AFAIK it would have had difficulty making a vertical takeoff without PCB...

There have been a few supersonic V/STOL aeroplanes (or STOVL as the new acronym has it). Yak-141 springs to mind, X-35B, F-35B when they get around to it, and if you want to go back to the dark ages there was Mirage III-V Balsac and the VJ-101C.

Of course all current space launchers takeoff vertically and all are very supersonic...

***

Flying fast means that any missiles you launch are flying fast before they burn any fuel.

If you've got the same missiles as me, and we're approaching each other head on, if I've got more energy than you I'll be able to launch first, which is a pretty useful advantage. Of course, I'll probably need a look-down radar to do that, but that's another story!

KarayaEine
01-04-2007, 11:09 AM
As an engineer that's worked on the Harrier I can tell you that it was never intended to go supersonic. As stated before the Pegasus engine isn't designed for supersonic flight. There's no way to control the inlet air to get it sub-sonic to prevent compressor stall when the airspeed is supersonic.

If you've ever seen the Harrier wings you'll notice they are quite thick in section view. They are not designed for supersonic flight. In order to be they would need to be half the thickness (or more) to reduce the inherent drag induced.

Plus it's primary role is a ground attack aircraft. Ground attack aircraft cannot perform their role very well when going supersonic. In fact supersonic flight low to the ground (where most ground attack aircraft fly) takes a tremendous amount of thrust and would consume huge amounts of fuel due to the air density being so great. Delivery of weapons at supersonic speeds (high drag bombs, dumb bombs, napalm, etc.) is very difficult as well. Most ground attack runs are performed at 400kts or below to insure accuracy.

Harriers have been known to go supersonic in a shallow dive at higher altitudes but this is only for very brief times and not sustained.

hth

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ForkTailedDevil
01-04-2007, 12:29 PM
I understood the F104 could supercruise to.<div class="ev_tpc_signature">

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Taylortony
01-04-2007, 08:09 PM
Ahh the Good old Orpheus engine in the Harrier I know it well http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Incidently the Harrier did trial Reheat systems (Plenum burning) but it was never adopted and they were looking at a supersonic version too again never taken up

CAF96th_Sillyak
01-04-2007, 08:18 PM
Yak-141 anybody?<div class="ev_tpc_signature">

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Xiolablu3
01-04-2007, 08:20 PM
Originally posted by ForkTailedDevil:
I understood the F104 could supercruise to.

It looks like it could if this is correct :-

http://www.916-starfighter.de/Joy%20of%20High%20Tech.htm


List of Supercruising planes from WIkipedia :-

* SR-71 Blackbird
* Concorde
* Tupolev Tu-144
* English Electric Lightning
* F-104 Starfighter
* BAC TSR-2
* Eurofighter Typhoon
* F-16XL
* F-14A+
* F-22 Raptor
* YF-23 Black Widow II
* XB-70 Valkyrie
* Dassault Rafale
* F-4 Phantom II (Israeli "Super Phantom" variant)
* Mikoyan-Gurevich MiG-25
(B-58 could also supercruise apparently)

Remember the older ones could barely do it and only in a very 'clean' verion.<div class="ev_tpc_signature">

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