Forum: F-35 Lightning II

DL,
I'm glad it's all so simple to you. I'm going to make one last effort to put thre record semi-straight, since having engaged this discussion I feel the need to finish.
Sensor package. (1) It bloody well should be good since IOC is ten to fifteen years later than any of the other aircraft mentioned. (2) Many of those aircraft will be upgraded by then. (3) Although you may argue that the overall sensor package is superior, there are sub-areas where its performance will not be better than that of its rivals - for example, an Su derivative will likely have better detection range due to aperture size.

The SU has a 1m class radar vs 700mm on an F-35, Typhoon or F-18. The other fighters have smaller aperture sizes. That is the SU has roughly twice the aperture size (antenna area). Assuming equivalent radar technology that translates roughly to twice the output and hence roughly a 30% improvement in range (it's a logarithmic function; roughly ten times the output equates to roughly twice the range). However, this is assuming parity in AESA technology. The fact however is that the USA is roughly 15 years ahead of the pack in AESA fighter radar implementations. This is not an blind statement. How many fighter AESA has the EU or Russia put into service? Answer, none, but they are working on the first for the earlier part of the next decade. How many has the USA put into service? Let's see... APG-63(v)2, APG-63(v)3/4, APG-77, APG-77(v)1, APG-79, APG-80. The F-35's APG-81 will be the fifth or the eighth depending on whether you count subvariants, and the oldest US fighter AESAs are now roughly 12 years old.

Kinematics & fuel reserves. The F-35A/C has a large internal fuel fraction, which is not bad (although there is a large price in OEW that must be set against the drag of tanks), but ultimately you carry as much fuel as you can lift. For instance, it's not hard to run the numbers on a Typhoon and an F-35A in max-practical-load conditions. The F-35A in that condition has a fractionally greater fuel fraction (0.38 plus vs 0.38 minus) and the same wing loading as an F-105.

I am not sure what is "practical" for you. However, the F-35 will carry 8.4 tons of fuel whereas the Typhoon carries 4.5 tons (internal). The maximum take off weight of the F-35 is 27.9 tons with an empty weight of ~12.7 tons. With 8.4 tons of fuel, that leaves about 6.8 tons for ordnance and external fuel. The maximum take off weight of the Typhoon is 23 tons with an 11 tons empty weight; with full fuel that leaves 7.5 tons for external fuel and mission ordnance. In terms of shear lifting capacity, the F-35 will lift 1.2 times its structural weight in fuel and ordnance. The Typhoon will lift 1.1 times.What's most important however is that a "clean" F-35 has almost twice the amount of fuel as a "clean" Typhoon. And whereas a clean Typhoon can't do anything but take the pilot on a joyride, a clean F-35 can fly an air superiority mission or a deep strike run with a weapons load typical of an F-16/18 flying these missions.

Maneuver: The F-35 at extreme altitudes will be penalized by high wing loading and higher effective wing loading (versus canards with no tail down moment) and higher bypass ratio. It also has an ops empty weight 3/4 that of the F-22 with juat about half the power and wing.

Let's put it this way... right up to 60,000 ft wing loading is not the problem. The aircrafts have more lift than they need to keep aloft. What matters more is control surface area -- for control authority -- the F-35's tails are 2~3 times larger than the Typhoon and Rafale's canards. In any case, the wing loading is calculated by extending the leading and tailing edges of the main wing to the center line. This invariably favors deltas and rhombic wings with high leading and trailing edge sweeps since a lot of "area" that isn't part of the wing is counted as "wing area". Wing area is also rather meaningless as fighters can derive up to 30~50% of their total lift as lift generation over the body and not the actual wing. In addition, at high AoA's body lift increase dramatically as a percentage of total lift to the point where planar area is probably a better indicator of high AoA lift than wing area.

The F-35 does not have tail down moments in level cruise; the tail provides lift. The aircraft is unstable and without the tails the aircraft with pitch up and flip over. The reverse is true for the Typhoon which is also an unstable design. The Cg of the typhoon is such that without the canards it will pitch up and flip over. The canards provide DOWN FORCE to keep the aircraft level. In short, with unstable designs the role of the tail or canards is reversed -- instead of keeping the nose up, they act to keep the nose down.

Ordnance: Best is subjective. Largest? Maybe, sometime.

No, best may be subjective, but largest is not. The US aircraft ordnance selection is significantly larger and more comprehensive than European or Russian ordnance selection. It is also important to note that the F-35 will shoot ALL of the leading Typhoon ordnance (eg. Meteor and Storm Shadow), whereas the reverse is not true.

Operability: Where does the seven hand tools thing come from? I've heard a similar statement made about the engine.
None of this is in any way a criticism of the designers. The F-35 was designed around an incredibly difficult requirement which demanded:
* stealth, with 2 x internal JDAMs + 2 x AMRAAMs
* size constrained by STOVL with a single engine
* basic design adaptable to a 140 knot CV approach speed
* basic design capable of accommodating powered lift system
* flight performance comparable to F-16 or F-18
* CV version with superior range (internal fuel) to fully loaded F-18E
It remains to be seen whether setting those requirements was a bright idea.

DL,
You're using the intellectual tactic of disregarding facts you can't disprove and inventing new ones to replace them.
But it's rather like running out of fuel in a dogfight. I'm running out of time and energy faster than I'm running out of arguments. I've got a turkey to go and cook, and it's more interesting than debating you.
(Later)
Turkey on...
AESAs don't change physics. You can pump more power through the aperture, do all sorts of fun tricks, but not change the equations. And the US will be 15 years ahead in 2015, if nobody's got an experimental AESA squadron; or in 2022, if nobody's got one in service. Expect that won't happen.

No, it doesn't but an AESA is typically more power, more sensitive and much better at LPI and multitasking modes than an MSA of the same size. Besides, the Typhoon for example has the SAME aperture deficit against an SU-30 compared to an F-35 -- both aircraft has the same radar aperture size. And, 15 years ahead or not, the USA is clearly ahead of everyone else in fighter AESAs and with an equivalent aperture to the Typhoon it is prudent to assume that the a 2015 F-35 will have a better radar than a 2015 Typhoon. If that is not good enough, then where does that leave the Typhoon?

JSF carries fuel inside (at least the A & C do). Rivals carry it inside and outside. Drag lower, weight higher, hence no drop tanks on an A380 and drop tanks on pretty much every fighter since 1940. In the real world, at same MTOW, fuel fractions are not that different.

Fuel fraction is not that different between, but a higher internal fuel fraction permits longer range and better kinematics because average drag is lower compared to an equivalent fuel load carried with a higher percentage in drop tanks. Using your example, if you take an A380, slim down the aircraft a little and put half of the fuel it carries on three external "drop tanks", it will end up with a shorter range and a higher per mile fuel cost.

Whats more important in terms of performance is that once a 4th generation fighter like the Typhoon drops its tanks (which it has to make a decent high speed dash), it has at most about 4.5 tons of fuel left. When an F-35 punches its tanks, it has up to 8.4 tons of fuel left. With both aircrafts having an installed thrust in the 40,500~43,000 lbs bracket and with TSFC of both engines being within 10% of each other, it means that the F-35 has almost twice the amount of afterburner endurance -- the F-35 probably leads in both thrust and TSFC but the difference does not change the argument.

Body lift is not something one finds in the standard aerodynamic textbooks. Neither has a breakthrough in this respect been mentioned in connection with F-22 or F-35 in 25 years of work. At high alpha the body will generate one thing, which is lots of drag.
In any event, this is getting close to the porcine musical instruction threshold, so over and out for now.

LO

Body lift is an integral part of most modern fighters although the designs such as the F-22 and F-35 with their broad fuselage, slab undersides and deliberate shapings then to produce body lift in larger quantity and higher efficiency. Even a wingless tube produces body lift at AoA's greater than zero degrees. One thing you'll notice about the F-35 fuselage if you slice it from the intakes to the trailing edge of the tails is that it is shaped somewhat like a Whitcomb airfoil.

If you observe an F-35 in flight you will notice two things. (1) The aircraft uses the horizontal tails for lift at cruise -- the tails are deflected upwards slightly in level flight. (2) The landing gears are situated ahead of about 3/4 of the main wing -- meaning the Cg is ahead of most of the wing.

What this means is that the body has to be generating a significant portion of the total lift. Otherwise with most of the wing lift aft of the Cg the aircraft will have a heavy stability bias and require significant down force by the tails to keep level.

Like I said, inventing new facts.
Typhoon has more radome space available than JSF. The nose diameter at the relevant point is 14 inches greater. Measurable and visible.

Let's put it this way, the Captor is a 700mm radar (ala the Hornet's AN/APG-73). The F-35's AN/APG-81 is also a 700mm radar. The F-18E/F block II carried a 700mm class AN/APG-79 and the future AMSAR offspring for the EF is likely to be 700mm class. None of these radar occupy the full diameter of the randome to airframe mate line if that is what you are looking at.

"15 years or not" - you made that statement and when it is proven to be unfounded you slide over into a different assertion. It is likely that AESA will become universal and much less expensive over the next few years and that all national capabilities will level out.

I stand by the 15 years statement in that by the time the first European or Russian fighter AESA enters service (circa 2012) the US would have been flying AESA equipped fighters operationally for 15 years. And, with over a decade of a head start, much more implementation and in-service experience, and a greater yearly R&D investment, it is likely that the technological gap in fighter radars will never disappear for the foreseeable future. Whether it will close and by how much however remains to be seen. Nonetheless, it should be a pretty safe bet that the F-35 in 2015 will have a better AESA than a Typhoon in 2015.

Did I say that internal fuel was bad? No. But it's fuel all the same, and costs in structure weight. With max internal fuel the F-35A weighs 5.8 tons more than the Typhoon. In the non-Dwight world where the laws of physics apply, that means it's gonna burn fuel about 35 per cent faster other things being equal, which they probably aren't due to inlet design, fineness ratio and engine TSFC.

Actually, no. Three reasons. (1) The maximum fuel the engine can burn is the maximum thrust output times the TSFC. It has nothing to do with weight. (2) Weight does not translate directly to drag or to impediment of acceleration unless you are going straight up. If an aircraft lightens by say 30% from a full tank to near empty, its drag does not decrease by 30% during that time, it decreases by a far smaller percentage. (3) A larger airframe is in general more efficient than a smaller one and larger engines are more efficient than smaller engines. In otherwords, if you double the size of an airframe the drag will less than double. In general, 40,000 lbs thrust engine is slightly more efficient in every respect than a 20,000 lbs engine.

Body lift may be useful if the wing's missing. Also, I'd suggest that you look at the F-35 in flight and ask whether the tail is at a positive alpha relative to the local airflow at the trailing edge of the wing.

The tail's normal attitude at cruise exhibits a positive alpha on unstable (tail heavy) designs. The F-35 and F-22 are both unstable airframes. In flight photos clearly show positive upwards deflection. Whether this is positive to local airflow is harder to ascertain, but it is highly unlikely that the F-35 wing has such excessively downward air stream behind the tailing edge of the wing.

And if the F-35 has such great body lift why does the C need a 670 sq ft wing?

"For AA-1, our biggest challenge is to be aggressive enough to find out all the things we don't yet know about the aircraft's performance. We have some real opportunities to learn how EHAs work at high speeds."

They learned (FLASH POOF OMG IT'S *&*&ING DARK IN HERE) about that all right...

"For AA-1, our biggest challenge is to be aggressive enough to find out all the things we don't yet know about the aircraft's performance. We have some real opportunities to learn how EHAs work at high speeds."

They learned (FLASH POOF OMG IT'S *&*&ING DARK IN HERE) about that all right...