ebj1248650
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Typhoon And F-22 Afterburner Use

Mon Oct 15, 2007 4:15 pm

Typhoon and the F-22 both have power to spare; can cruise at Mach 1+ without use of afterburner. With this kind of excess power, why don't these airplane take off in military power. I can't number the many photos I've seen of F-22s and Typhoons taking off in afterburner and it seems unnecessary. While stationed at Luke AFB, I often saw clean configured F-16s take off in military power and they had no problem at all. Is the use of afterburner for F-22 and Typhoon take offs for show or is there something I'm not understanding?
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highlander0
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RE: Typhoon And F-22 Afterburner Use

Mon Oct 15, 2007 4:28 pm

Perhaps it is to get the aircraft to the safest speed incase of a one engine failure. I think the F-16 would have a *slight* problem on that front.


I know that Tonka (Tornado) pilots regulary leave re-heat on untill bout 300 knots (555 km/h) which is best single-engine speed should a failure occur.

[Edited 2007-10-15 09:29:08]
 
PADSpot
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RE: Typhoon And F-22 Afterburner Use

Mon Oct 15, 2007 4:39 pm

Quoting EBJ1248650 (Thread starter):
With this kind of excess power, why don't these airplane take off in military power. I can't number the many photos I've seen of F-22s and Typhoons taking off in afterburner and it seems unnecessary.

German Eurofighters usually take off W/O reheat. Exception are alpha-scrambles, air shows or flight under heavy loads. I can just repeat myself once again: Do not draw any conclusion from air shows or events alike.

It is for noise reduction, reduction of fuel consumption and reduction of wear. Also since the introduction of the EF German Air Force is once again conducting simultaneous take offs which had become somewhat rare after the the end of the Cold War.
 
checksixx
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RE: Typhoon And F-22 Afterburner Use

Mon Oct 15, 2007 6:17 pm

F-22's normally take-off without afterburner. Most of the pictures you see that the Raptor is taking off with afterburner are at airshows.
 
garysted
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RE: Typhoon And F-22 Afterburner Use

Mon Oct 15, 2007 6:34 pm

Hi,

I think you'll find it's very, very rare to see operational RAF Typhoon's depart in afterburner - unless it's a airshow performance or a back seat ride for a lucky guest. During numerous visit's to Coningsby for photography I've only seen one afterburner departure - and that was a ride as said above. I've seen operational QRA departure's with wing tanks and eight AAM's and the three tank configuration, all without burners. I guess the high percentage of Typhoon burner shot's on A.net would be because many are airshow pics or are so rare that they've been uploaded specifically because of it. I think a lot of the pre-delivery flights from Warton are also carried out in burner - I would love to photograph burner shots at Coningsby!

Gary
 
ebj1248650
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RE: Typhoon And F-22 Afterburner Use

Tue Oct 16, 2007 2:14 pm

Quoting Garysted (Reply 4):
Hi,

I think you'll find it's very, very rare to see operational RAF Typhoon's depart in afterburner - unless it's a airshow performance or a back seat ride for a lucky guest. During numerous visit's to Coningsby for photography I've only seen one afterburner departure - and that was a ride as said above. I've seen operational QRA departure's with wing tanks and eight AAM's and the three tank configuration, all without burners. I guess the high percentage of Typhoon burner shot's on A.net would be because many are airshow pics or are so rare that they've been uploaded specifically because of it. I think a lot of the pre-delivery flights from Warton are also carried out in burner - I would love to photograph burner shots at Coningsby!

Gary

Gary, to you and the others who responded, many thanks. Now I know the score. Much appreciated. Earl
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autothrust
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 9:34 am

Quoting PADSpot (Reply 2):
Exception are alpha-scrambles, air shows or flight under heavy loads

Isn't it quite sensless using apart QRA to use afterburners even its a flight with heavy load?

Quote:

The 17 Sqn aircraft was airborne after a 2,800ft (850m)take-off roll in full reheat, before climbing to an altitude of 40,000ft using dry power. “With six Paveway IIs and six [air-to-air] missiles, the aircraft was carrying a weapons load equivalent to three legacy platforms,” says Pemberton. “This fit clearly illustrates the impressive nature of the Typhoon’s performance and gives an exciting insight into future operations.”

http://www.flightglobal.com/articles...conducts-heavy-weapons-trials.html

It could have done the takeoff perfectly without afterburner, it would have just needed a little more runway. Waste of fuel don't you think?
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PADSpot
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 10:19 am

Quoting AutoThrust (Reply 6):
It could have done the takeoff perfectly without afterburner, it would have just needed a little more runway. Waste of fuel don't you think?

Runway length is fixed and military airplanes need much larger security margins compared to civil airliners as braking power is relatively much lower. Typical military runways at fighter bases are 2000-2400m. With a heavy load you simply need to be airborne after about 1000m, because otherwise you don't have enough runway left to come to safe stop in case of an rejected take-off. You can almost say required runway length is take-off distance *2.
 
Norlander
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 10:35 am

Quoting PADSpot (Reply 7):
...military airplanes need much larger security margins compared to civil airliners...

Please explain that point a bit more, as I understand it military equipment doesn't need to hold to the stricter security margins of civilian use. They are not liable in the same way. To put it another way: "There is no way a plane like the SR-71 would ever be certified for civilian use".
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TheSonntag
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 11:42 am

Quoting Norlander (Reply 8):
Please explain that point a bit more, as I understand it military equipment doesn't need to hold to the stricter security margins of civilian use.

I am not an expert, but NATO has certain rules which are not mandatory for civilian operations. For example, as far as I know, fire brigades must be ready when a transport plane is switching on its engines, at least my grandfather told me that once.

When taking into account that military planes usually take more risks, it does not seem unlikely that they also have tighter rules for certain procedures. Maybe someone who knows more can explain this.
 
PADSpot
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 2:16 pm

Quoting Norlander (Reply 8):
Please explain that point a bit more, as I understand it military equipment doesn't need to hold to the stricter security margins of civilian use. They are not liable in the same way. To put it another way: "There is no way a plane like the SR-71 would ever be certified for civilian use".

I think you misunderstood me. A fully laden jet fighter needs to be airborne after about 1000m, because it may need the remaining 1000-1200m to come a stop if it had to reject take off. It is not like a B737 which just has to take care that the remaining runway length from the time it reaches V1 speed is sufficient to come to a stop. Jet fighters may have only one engine and are mostly incapable of take-off on a single engine when fully laden. Also jet fighter usually have less breaking power, which makes emergency arrestor systems necessary in cases of emergency. The power-to-weight-to-brakepower ratio is entirely different with jet fighters compared to commercial airliners. Thus runway requirements are different.

In other words you cannot do a "dry" take off with 5tonnes of ordnance that would take 2000m on a 2200 runway. If an engine broke down on the last meter you would be in trouble.
 
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zeke
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 2:21 pm

Quoting PADSpot (Reply 7):

Runway length is fixed and military airplanes need much larger security margins compared to civil airliners as braking power is relatively much lower. Typical military runways at fighter bases are 2000-2400m. With a heavy load you simply need to be airborne after about 1000m, because otherwise you don't have enough runway left to come to safe stop in case of an rejected take-off. You can almost say required runway length is take-off distance *2.

The Jaguar technique was to pull back at the threshold markers at the other end of the runway and hope you clear the fence.
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autothrust
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 3:13 pm

Quoting PADSpot (Reply 10):
Jet fighters may have only one engine and are mostly incapable of take-off on a single engine when fully laden. Also jet fighter usually have less breaking power, which makes emergency arrestor systems necessary in cases of emergency. The power-to-weight-to-brakepower ratio is entirely different with jet fighters compared to commercial airliners.

While i mostly agree, the EF has to have good brakes because the EJ-200 on IDLE produce so much thrust, to make the plane move if the brakes aren't applied.

Second though fighters don't have thrust reversers, the Typhoon(and othe types) have a deployable brake chute, which i guess wouldn't need at a RTO 1000 meters to stop.
“Faliure is not an option.”
 
rwessel
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 8:35 pm

Quoting PADSpot (Reply 10):
Jet fighters may have only one engine and are mostly incapable of take-off on a single engine when fully laden.

That doesn't make a lot of sense to me. Most twin engine fighters have similar (or better) MTOW wing loadings as airliners, and much more installed power.

Consider:

777-200:
MTOW: 535klbs
Engines: 2x77klbs
Wing loading: 132lbs/sqft
Single engine power loading: 6.9lbs/lb

F-15C:
MTOW: 68klbs
Engines: 2x17.5klbs dry, 2x25klbs A/B
Wing loading: 112lbs/sqft
Single engine power loading: 2.7lbs/lb

In fact the F-15 has considerably better power loading on a single engine than the 777 has on both (and only a bit worse than the 777 with a single engine "dry"). Admittedly the F-15C is near the high end of the range, but fighters tend to be severely overpowered.
 
PADSpot
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RE: Typhoon And F-22 Afterburner Use

Wed Oct 17, 2007 8:47 pm

Quoting AutoThrust (Reply 12):
While i mostly agree, the EF has to have good brakes because the EJ-200 on IDLE produce so much thrust, to make the plane move if the brakes aren't applied.

Ehhmm. Don't tell that to anyone who has a basic knowledge of physics. You will get a hell of a bashing  Wink

Just do that experiment with you car. Pull the hand brake really tight and try to start. If your break works it will quite hard to accelerate at all. You will need all the power to overcome the break and it will smoke and smell. Now drive 100kph on a highway and try to stop the car wit the hand brake. It will takes ages ...

Braking power increases almost linearly while the kinetic power that you need to kill with a brake has got a quadratic relation to speed. The kinetic power of 20t aircraft at 320kph is ASTRONOMICALLY BRUTE. Nevertheless even a really bad brake might be able to keep an aircraft still although you apply high levels of (dry) thrust. That's because a still aircraft has ZERO kinetic energy even if full afterburner applied. In order to keep the aircraft still the brake just needs to hold, but is does not destroy any energy. Energies are destroyed when parts of landing gear break after you drove your experiment over the top.

Quoting AutoThrust (Reply 12):


Second though fighters don't have thrust reversers, the Typhoon(and othe types) have a deployable brake chute, which i guess wouldn't need at a RTO 1000 meters to stop.

The Tornado has got thrust reversers. Brake chutes are optional on some types and a mere emergency measure on others. There are not so many type who deploy brake chutes as part of a normal landing.

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