Forum: F-35 Lightning II

Can somebody explain how the F-35 with a high wing loading can be at the same time agile, maneuverable, as LM says???

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Wing loading isn't the only metric that determines a fighter's maneuverability. There is also the lift coefficient, lift-to-drag ratio, thrust-to-weight ratio, thrust-to-drag ratio, the flight control system, control surface sizes and moment arms, etc. Also, consider that the F-35 carries its weapons internally, which will reduce drag when maneuvering and therefore allow it to retain energy better.

I have no idea, may be this is some more debating stuff for technical members

LM defends F-35 JSF agility against critics
Quote: Chris Pocock June 15, 2009 Military Aircraft
Source: http://www.ainonline.com/news/single-ne ... ics-21060/

But Rand authors John Stillion and Scott Purdue contended that the high wing loading of the F-35 makes it inherently less agile than current fighter aircraft, including Russia’s MiGs and Sukhois, and Europe’s Rafale and Typhoon. Moreover, the F-35’s thrust loading is significantly inferior to that of the F-15, F-16 and F-22, they said. As a result, Rand alleged, the F-35 is inferior in visual-range combat in terms of acceleration, climb and sustained-turn capability. It also has a lower top speed, they added.

Beesley called these comparisons naïve and simplistic. An empty F-35A will weigh 30,000 pounds and have a maximum thrust of 40,000 pounds, he noted. “Even when you add the 1,200 pounds of our air-to-air combat load and the 9,000 pounds half-fuel load with which you would typically begin an air-to-air engagement, then our power-to-weight ratio is still almost 1:1.” Moreover, he noted, the F-35’s half-fuel load is greater than today’s fighters. An F-16 would have only 3,600 pounds.

Beesley also insisted that the sustained turn rate of the F-35 is conquerable, despite its higher wing loading. He insisted that there is “a huge amount of thrust available” from the aircraft’s Pratt & Whitney F135 engine, which is the most powerful ever fitted to a combat aircraft.

The F-35 chief test pilot further noted that the F-35 can fly at angles of attack that are just as steep as those of the F-18 or the F-22. “It’s a fully maneuverable 50-degree airplane,” he said. He invited those who had witnessed the F-22’s startling agility at airshows recently to ponder the fact that “the same people also designed the flight control system for the F-35.”

Moreover, Beesley told AIN, the debate should not be limited to a discussion of visual-range dogfighting. “In a real combat mission, the ability to sneak up on your opponent and be the first to shoot is paramount,” he said.

This is a reference to stealth, of course, and the F-35’s low observability cannot be matched by any of the fighters that were mentioned in the Rand analysis. Opposing fighter pilots will find that the range at which they can detect the F-35, either by radar or electro-optics/infrared means, will be much shorter than they are used to.
But Beesley also had another “non-kinetic” characteristic in mind–the F-35’s mission avionics, claimed to be the most advanced in the world. “The F-35 pilot will have superior situational awareness, by day and by night, and a helmet-mounted display. This will be a great advantage and will allow him to take full advantage of the performance of today’s off-boresight air-to-air missiles,” he said.

A Rand analysist who has never flown anything but his desk

vs

Various test pilots who have flown the jet and have a lifetime experience in aeronautics

Ask yourself Which ones the more credible source..?

Last edited by m on Jan 23, 2011 - 08:25 PM; edited 1 time in total

Not that difficult to answer .. either the article may be wiil some help for Calel.

And let's not forget the case where an F-16 had to use the afterburner to keep up with a non-afterburning F-35.

Wing loading isn't an accurate metric nowadays, since strakes, body lift, high lift devices, etc. all matter. It's basically leftover from an era when airplanes were tubes with wings.

In the olden days of jet fighters the fuselage wasn't designed to generate lift, all they produced was drag. A typical case for this would be an F-104 with its pencil fuselage. Then the teen series of fighters came along with their Lead edge extensions which induced vortex lift over the wing. The F-16 and F-18 would be your case example here. With the F-22 and F-35 the fuselage has totally optimized through 3d CFD and wing tunnel testing to produce the best lift to drag ratio possible. So in actuality the F-35 is a blended wing lifting body. A lot people look at wing aspect ratio as indication of aircraft performance which is fine for an aircraft with a pencil fuselage like the F-104 but doesn't work so good for an aircraft like the F-35. So to answer your question the F-35 can get away with stubbier wings because its fuselage produces lift as well.

The other aspect of the F-35 is it is designed to carry its weapons internally so it does not have the parasitic drag penalty that the teen series fighters have when carrying ordinance and extra fuel. If the F-35 is leaving the F-16 and F-18 chase planes in the dust now with them just carrying a belly tank it will be flying circles around them when they are fully armed pushing a lot of parasitc drag. Smile

Dunno why that Northrop honcho would bother to tell us that 'manouverability is irrelevant' if the concerns about the F-35's manouverability were not legitimate. And while we're on the topic of what's irrelevant - so is the 'parasite drag' argument put forth by the JSF apologists. Because fighter-bombers can jettison their draggy loads when the need to manouver becomes paramount. And yes, while it's true that a bomber without bombs cannot accomplish much, that is of little relevance if the situation rarely comes up. As it has not for many decades, and very likely will not for decades more to come. Sinophobic Chicken Little squawks to the contrary...

Another thing: It's an elementary principle of logic that the validity of an assertion is not dependent upon who makes it. If a desk jockey says something that's true, it's true. Regardless of how many fast jet hours his corporate employee opponent may possess. BTW, I asked this once and got no answer, so I'll ask again - has the the Hi-AOA flight characteristics of the F-35 been rigorously explored yet, or not? And if so, where are the reports that contradict the recent DOT&E report on the subject?

JL

Reply to original question

Wing loading means virtually nothing. It's as many have said before, aerodynamics isn't trivial. You don't look at one statistic and claim to have an answer. The F-35's agility doesn't only depend on wing area, but the airfoil, fuselage, wing planform, thrust, etc.

Oh, and the F-35's wing loading isn't all that high anyway. It carries 18,000 lbs of fuel, the wing loading for other fighters may exclude drop tanks, which makes their numbers look much better.

Reply to butters

Fighters typically won't drop their air to air load out, as it would make them useless. Even if they did, I'm pretty sure that the pylons stay on. Also, if there are weapons mounted externally, the engineers have to choose the configuration where the plane performs best (clean? full load out? half load out?).

It's true that truth is truth regardless of who says it, but some people are more likely to be correct than others on certain subjects (I'm not taking sides, just saying).

I don't know of any high AoA flight test data on the F-35.

@butters..... If the F-35 makes the enemy aircraft jettison it's ordinance by it's sheer presence then it is a mission success for the F-35 and mission failure for the enemy aircraft. Also don't forget by the time the stealthy F-35 shows up on the enemy planes radar he will right on top of him. From 30 miles out if both planes are near supersonic speed coming head on it's only 50-75 seconds to the merge.

If the F-35 fires an Amraam missile first at the 30 mile mark the enemy has 30-35 seconds to make evasive maneuvers before probable missle impact which puts the enemy aircraft in a defensive posture with two F-35 rolling in on him.

Also because the enemy pilot doesn’t know whether it is F-22’s or an F-35’s coming he really can’t be to careful.

30 miles for a head-2-head radar engagement with the F-35 is EXTREMELY optimistic. Even Kopp (who hates all things F-35) puts the Su-35's range for detecting/tracking a F-35 at less than 20 (head on).

@ Cowboy, I think if the bandit even gets something on it's radar would it have enough information in those pings to see if the fighter is bearing down on it from 60k+ and supersonic speeds or 30k and subsonic speeds...

calel wrote:

Can somebody explain how the F-35 with a high wing loading can be at the same time agile, maneuverable, as LM says???

FYI, the F-4 Phantom has a lower wing loading than an F-16, but which do you think will fly circles around the other? The wing loading doesn't tell the whole story, aerodynamically. Other posters have mentioned some of the other factors involved.

@Wrightwing....... Some would argue that the only reason the F-4 flys at all is because it is repulsed by the earth.

@calel....... On Google books check out the chapter 4, of the book, "Fighter Combat Tatics and Maneuvering"

Chapter 4 deals with, "One-versus-One Maneuvering, Dissimilar Aircraft". Page 140-141 discusses wing area and wing loading of the F-14.

Also check out the appendix for some delightfully nerdy reading on "Fighter Performance".

http://books.google.ca/books?id=hBxBdKr0beYC&lpg=PA141&dq=Fighter%20Wing%20Loading&pg=PP1#v=onepage&q=Fighter%20Wing%20Loading&f=true[/url]

Forum: F-35 Lightning II

Agile F-35 High Wing Loading