• Hi Guest! Forum rules have been updated. All users please read here.

Hinting at supercruise ? ( F-35 )

seruriermarshal

ACCESS: Top Secret
Joined
May 4, 2008
Messages
1,061
Reaction score
266
The F-35 can't supercruise like the F-22 Raptor, but the test pilots have found that once they break the sound barrier, supersonic speeds are easy to sustain.

"What we can do in our airplane is get above the Mach with afterburner, and once you get it going ... you can definitely pull the throttle back quite a bit and still maintain supersonic, so technically you're pretty much at very, very min[imum] afterburner while you're cruising," Griffiths said. "So it really does have very good acceleration capabilities up in the air."

http://www.defensenews.com/story.php?i=6792072&c=FEA&s=CVS
 

LowObservable

ACCESS: Top Secret
Senior Member
Joined
Oct 18, 2006
Messages
2,214
Reaction score
195
Actually what he's saying is that it does not supercruise at all, even under test conditions.
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
14,009
Reaction score
2,432
By comparision one F-104 pilot related how they were able to cruise at Mach 2 in min afterburner, at 73,000ft. Granted, the F-104 wasn't much more than a tinfoil tube wrapped around an engine but still. . .
 

LowObservable

ACCESS: Top Secret
Senior Member
Joined
Oct 18, 2006
Messages
2,214
Reaction score
195
Better than a plastic freight container wrapped around an engine...
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
14,009
Reaction score
2,432
LowObservable said:
Better than a plastic freight container wrapped around an engine...

The best tool for the job isn't always the one that looks the coolest.
 

chuck4

ACCESS: Top Secret
Joined
Jan 17, 2011
Messages
803
Reaction score
8
sferrin said:
By comparision one F-104 pilot related how they were able to cruise at Mach 2 in min afterburner, at 73,000ft. Granted, the F-104 wasn't much more than a tinfoil tube wrapped around an engine but still. . .

Mach 2 at 73,000 feet has the same gorund speed as Mach 1.5 at sea level.
 

Abraham Gubler

ACCESS: Top Secret
Senior Member
Joined
Mar 18, 2008
Messages
3,555
Reaction score
255
seruriermarshal said:
"What we can do in our airplane is get above the Mach with afterburner, and once you get it going ... you can definitely pull the throttle back quite a bit and still maintain supersonic, so technically you're pretty much at very, very min[imum] afterburner while you're cruising,"

It’s a shame to see how such a semantically driven concept like “super-cruising” has become important in defining contemporary aircraft. What is really important is how much fuel an aircraft type needs to burn to sustain supersonic flight. The F-22 burns around four times as much fuel at Mach 1.5 than at Mach 0.8 even without the need to apply reheat.

LowObservable said:
Actually what he's saying is that it does not supercruise at all, even under test conditions.

Test conditions? Do they have a special low pressure atmosphere to test in that makes it easier to cruise at supersonic speeds?

I would imagine anyone with a fair approach to such things will look at this information and think engine growth… The F-35 on its initial engine is cracking Mach 1.0 at the lowest reheat setting (~30,000-35,000 lbs). So what is it going to do with an F135-PW-200 engine onboard or the F136 with claimed higher thrust?
 

chuck4

ACCESS: Top Secret
Joined
Jan 17, 2011
Messages
803
Reaction score
8
F-35 on it's second engine is also likely to have gained a few hundred pounds at least elsewhere.
 

LowObservable

ACCESS: Top Secret
Senior Member
Joined
Oct 18, 2006
Messages
2,214
Reaction score
195
"So what is it going to do with an F135-PW-200 engine onboard?"

Burn more gas.
 

purduesUSAFguy

ACCESS: Restricted
Joined
Jun 15, 2011
Messages
2
Reaction score
0
A clean F-15 can pull basically the same trick, the difference is that you could go to war with a clean F-35 (in theory at least) and a clean 15 is only useful for delivery flights and air shows.
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
14,009
Reaction score
2,432
LowObservable said:
"So what is it going to do with an F135-PW-200 engine onboard?"

Burn more gas.

Kinda like a Superhornet with higher powered F414s? ;)
 

Abraham Gubler

ACCESS: Top Secret
Senior Member
Joined
Mar 18, 2008
Messages
3,555
Reaction score
255
LowObservable said:
"So what is it going to do with an F135-PW-200 engine onboard?"

Burn more gas.

Which in the real world results in higher exhaust velocity which leads to increased thrust. Though I would imagine P&W would not just be increasing the nozzle flows into the turbine for improved F135s but looking at other methods of tweaking more thrust from the engine. That is of course if I judge the program fairly rather than try and defame it at every opportunity.
 

Sundog

ACCESS: Top Secret
Senior Member
Joined
Aug 2, 2006
Messages
2,888
Reaction score
378
Abraham Gubler said:
LowObservable said:
"So what is it going to do with an F135-PW-200 engine onboard?"

Burn more gas.

Which in the real world results in higher exhaust velocity which leads to increased thrust. Though I would imagine P&W would not just be increasing the nozzle flows into the turbine for improved F135s but looking at other methods of tweaking more thrust from the engine. That is of course if I judge the program fairly rather than try and defame it at every opportunity.

Indeed, they're also raising the TIT.
 

bobbymike

ACCESS: USAP
Senior Member
Joined
Apr 21, 2009
Messages
10,950
Reaction score
2,193
Abraham Gubler said:
LowObservable said:
"So what is it going to do with an F135-PW-200 engine onboard?"

Burn more gas.

Which in the real world results in higher exhaust velocity which leads to increased thrust. Though I would imagine P&W would not just be increasing the nozzle flows into the turbine for improved F135s but looking at other methods of tweaking more thrust from the engine. That is of course if I judge the program fairly rather than try and defame it at every opportunity.

I will try and find the old Aviation Week article (maybe six months or so ago) that talked of up to 25% thrust growth or in the 45k to 50k along the lines of the VAATE target I believe.
 

Abraham Gubler

ACCESS: Top Secret
Senior Member
Joined
Mar 18, 2008
Messages
3,555
Reaction score
255
bobbymike said:
I will try and find the old Aviation Week article (maybe six months or so ago) that talked of up to 25% thrust growth or in the 45k to 50k along the lines of the VAATE target I believe.

If they achieve a 25% increase in dry thrust (~35,500 lbs) then lo and behold we have a supercruising F-35.
 

bobbymike

ACCESS: USAP
Senior Member
Joined
Apr 21, 2009
Messages
10,950
Reaction score
2,193
Abraham Gubler said:
bobbymike said:
I will try and find the old Aviation Week article (maybe six months or so ago) that talked of up to 25% thrust growth or in the 45k to 50k along the lines of the VAATE target I believe.

If they achieve a 25% increase in dry thrust (~35,500 lbs) then lo and behold we have a supercruising F-35.
flanker said:
wow, 25 % extra thrust. Color me skeptical.

OK closer to a year ago:

Pratt Raises Stakes In JSF Engine Battle

Aug 27, 2010 - By Guy Norris

WEST PALM BEACH, Fla. — Pratt & Whitney is upping the ante in the ongoing F-35 Joint Strike Fighter engine war by revealing the F135 has achieved combat-rated thrust 20% higher than the specification. The disclosure raises the demonstrated sea-level thrust for the F135 above 50,000 lb
 

Abraham Gubler

ACCESS: Top Secret
Senior Member
Joined
Mar 18, 2008
Messages
3,555
Reaction score
255
flanker said:
wow, 25 % extra thrust. Color me skeptical.

You've obviously never heard of the development life of just about every engine to date. For example:

F100-PW-100 23,930 lbs
F100-PW-229 29,160 lbs
 

bobbymike

ACCESS: USAP
Senior Member
Joined
Apr 21, 2009
Messages
10,950
Reaction score
2,193
bobbymike said:
Abraham Gubler said:
bobbymike said:
I will try and find the old Aviation Week article (maybe six months or so ago) that talked of up to 25% thrust growth or in the 45k to 50k along the lines of the VAATE target I believe.

If they achieve a 25% increase in dry thrust (~35,500 lbs) then lo and behold we have a supercruising F-35.
flanker said:
wow, 25 % extra thrust. Color me skeptical.

OK closer to a year ago:

Pratt Raises Stakes In JSF Engine Battle

Aug 27, 2010 - By Guy Norris

WEST PALM BEACH, Fla. — Pratt & Whitney is upping the ante in the ongoing F-35 Joint Strike Fighter engine war by revealing the F135 has achieved combat-rated thrust 20% higher than the specification. The disclosure raises the demonstrated sea-level thrust for the F135 above 50,000 lb

Other articles basically say its a thrust vs engine life issue (most here at SP probably know this already) You can have much higher thrust now at the cost of engine component life. Over the life of the engine as AG pointed out incremental thrust increases are usually accompanied by claims that it won't reduce engine life and hence increase R&M expense.
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
14,009
Reaction score
2,432
Abraham Gubler said:
flanker said:
wow, 25 % extra thrust. Color me skeptical.

You've obviously never heard of the development life of just about every engine to date. For example:

F100-PW-100 23,930 lbs
F100-PW-229 29,160 lbs

furthermore. . .

F100-PW-232 ran at 37,150 lbs back in the 90s.
GE F110-132 ran at 36,500 lbs back in the 90s.
 

Trident

ACCESS: Top Secret
Senior Member
Joined
May 8, 2006
Messages
1,155
Reaction score
495
Abraham Gubler said:
Which in the real world results in higher exhaust velocity which leads to increased thrust. Though I would imagine P&W would not just be increasing the nozzle flows into the turbine for improved F135s but looking at other methods of tweaking more thrust from the engine. That is of course if I judge the program fairly rather than try and defame it at every opportunity.

It's hardly unreasonable to point out increased fuel consumption when that could potentially take the 'cruise' out of supercruise, depending on how the F-35's transonic/low-supersonic thrust requirements stack up. Since reheated thrust lapses less with altitude than dry thrust, the military power increment over the current engine necessary to match the minimum afterburner setting of the latter might be more substantial than it seems.

sferrin said:
furthermore. . .

F100-PW-232 ran at 37,150 lbs back in the 90s.
GE F110-132 ran at 36,500 lbs back in the 90s.

True, but for how long? 2 hours?

The fact that the most powerful variant of either power plant to enter actual operational service (which it only did a few years ago, too) produces 4000 pounds less than this rather speaks for itself ;) It also took the better part of 2 decades to get from the F100-PW-100 to the -229.
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
14,009
Reaction score
2,432
Trident said:
True, but for how long? 2 hours?

The fact that the most powerful variant of either power plant to enter actual operational service (which it only did a few years ago, too) produces 4000 pounds less than this rather speaks for itself ;) It also took the better part of 2 decades to get from the F100-PW-100 to the -229.

Is this really the place for conspiracy theories? ::)
 

Trident

ACCESS: Top Secret
Senior Member
Joined
May 8, 2006
Messages
1,155
Reaction score
495
sferrin said:
Is this really the place for conspiracy theories? ::)

I would not exactly class it as a conspiracy theory to point out that a 37000 pound rating would probably have degraded TBO intervals to an impractical level. It's not that uncommon to run bench tests way beyond the intended service thrust level BTW, a recent example would be the RR Trent XWB (the model for the smaller airframe variants, to be precise, intended to produce 75000 to 84000 pounds operationally). This has already been tested to 100000 pounds, which is more than the version for the A350-1000 at its newly increased 98000 (used to be 93000) pound rating, despite the fact that the latter will be switched to an upgraded core to meet the higher thrust target. If the basic design truly was good for 100000 pounds with no durability penalties, why would they do that?
 

LowObservable

ACCESS: Top Secret
Senior Member
Joined
Oct 18, 2006
Messages
2,214
Reaction score
195
Remember that a static-thrust throttle push may not get you supercruise.

You also need to tolerate higher temperatures at the compressor exit because of pressure and temperature rise in the inlet. The design of the inlet itself is also important.

Higher thrust in the F-15 and F-16 was called for to maintain high subsonic speed and acceleration in heavy, dirty configurations, and I don't know that the later F100 and F110 were intended to do that much for you above Mach 1.

A VAATE/Advent-type engine would be a different kettle of fish, but won't be around for a while.
 

Similar threads

Top