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How Things Work: Thrust VectoringExplore more photos from the story |
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RedditRemember the scene in the movie Top Gun when Navy pilot Pete “Maverick” Mitchell gets the upper hand on his instructors by slowing down, pulling up the nose of his F-14 Tomcat, and watching his opponent fly right by? The idea was to get a quick, unexpected position behind the bad guy, putting Maverick (played by Tom Cruise) and his trusty sidekick Goose into place to win the Engagement.
Real fighter pilots will tell you that what Maverick does is a showoff move that bleeds off so much energy that you’re vulnerable to getting shot down yourself. What a pilot really needs is a way to quickly get in the right position to fire at the enemy. Today’s most maneuverable fighters use thrust vectoring, which can make a jet turn faster and more tightly.
Powered by Pratt & Whitney F119 turbofans, each with 35,000 pounds of thrust, the F-22A—the Air Force’s newest fighter—sports a nozzle that can direct exhaust thrust up or down as much as 24 degrees.
The advantage to pilots is superior low-speed and high angle-of-attack maneuverability, compared to conventional-thrust aircraft, says Second Lieutenant Aaron Hoke, a propulsion engineer on the U.S. Air Force team that manages the Lockheed Martin F-22A Raptor program at Wright-Patterson Air Force Base in Ohio.
“Our [one-on-one] tactics have changed to incorporate the ‘post-stall’ regime, where other aircraft cannot operate,” explains Captain John “Rocks” Wagemann, who flies the F-22A in the First Fighter Wing at Langley Air Force Base in Virginia. Thrust vectoring enables the pilots to fly up and over in a very tight arc, Wagemann says, and “gives us the nose authority to turn the jet while the wings are stalled, similar to a controlled flat spin.”
Thanks to advanced computers and flight control systems, pilots don’t have to think about choosing vectoring or executing specific steps to perform a maneuver. They simply point the airplane where they want, and the onboard systems automatically coordinate the right combination of flaps, rudder, elevator, and nozzle angle. “The F119’s vectoring nozzle is integrated into the F-22 flight control system” so that “the pilot doesn’t control the nozzle independently,” says Chris Flynn, Pratt & Whitney’s F119 director.
Flaps in the engine nozzle point up or down to “steer” the jet exhaust, making the airplane more responsive and maneuverable. In a two-engine airplane like the F-22, directing the exhaust from both engines upward points the nose up, while reversing the direction points the nose down. The F119 engines are designed to vector in the same direction and by the same amount. The nozzle is said to be “two dimensional” when the shape of the throat is rectangular.
Flight tests of thrust-vectoring designs began in the early 1990s with airplanes like NASA’s modified F/A-18 and F-15, the Rockwell/MBB X-31, and a modified Air Force F-16. In 1994, the X-31 demonstrator was fitted with what German program managers called a “poor man’s thrust vectoring nozzle”—three paddle-like vanes that pushed into the exhaust stream—and the results were spectacular. Without thrust vectoring, the X-31 lost twice as often as it won against the F/A-18 in mock combat; with it, the X-31 didn’t lose once in 129 matches.
Comments
I can not see risking a 200 million dollar fighter in a close in visual engagement. I thought dog fighting was obsolete, again. The more expensive the figher and less that will be built. This then promotes more conservative tactics that put the aircraft less at risk. That may be why so few aircraft have employed thrust vectoring and why more effort is being spent on stealth and longer range air to air missles.
Posted by Brian Cavanagh on May 18,2008 | 04:46AM
You could have talked a little more about the Russian fighters holding thrust vectoring.
Posted by Marcelo Augusto on May 25,2008 | 07:40PM
In response to Brian, Dogfighting will never be obsolete. That's the hard lesson that the military learned when introducing the F-4 phantom over Vietnam. The "experts" went so far as to influence the military to not put guns on the aircraft. They thought the advent of missiles would make dogfighting obsolete, but the pilots without dogfighting training didn't know how to position themselves correctly to fire the missiles, so the missile kill rate was much lower than expected. Furthermore, once they are out of missiles, they aren't as good at evading the enemy because they don't know how to dogfight. The F-22 is the perfect blend of technology and tradition, able to take the enemy out from miles away, but still more capable in dogfighting than any other fighter on earth. Dogfighting may never become obsolete, but the one thing for certain is that technology will always play a crucial role in how dogfighting is carried out. You're right - you don't want to risk a $200 million aircraft, which is why you fire missiles first. But in case you need to get up close and personal, the F22 has teeth that bite there, too.
Posted by Kel Jackson on June 14,2008 | 06:25PM
For Marcelo: Ah, I would have, but magazines only have just so much space. I could have talked not only about the Russians but the Indians, who have taken Russian MiG technology and run with it...particularly in thrust-vectoring.
Posted by Jim Mathews on June 15,2008 | 01:53PM
Well, I litteraly thought you did a great job on this article. But as far as reality is concerned about creation of jets. The Germans were the first to accomplish this. That is...in WWII before the battle of Berlin in 1942, the Germans created the first jet-born fighter which I don't exactly remember the name of. Furthermore, these guys know exactly what thrust vectoring is; and if they see something wrong with the models. They are quick to judge the schematics or blueprints that went into creating an aircraft capable of thrust vectoring. Then also, you mentioned about the early flight tests of thrust vectoring NASA performed on the aircrafts that German managers called the "poor man’s thrust vectoring nozzle." I thought the reason they said this was because the response timing took slightly too long to position the pilots during a dogfight in order to gain the upperhand. Then again, I could be wrong.
Posted by David Smith on June 26,2008 | 08:08AM
For David, The aircraft was the X-31 demonstrator, and it was the "poor man's" thrust-vectoring nozzle because it used three paddles to deflect into the jet efflux rather than a full-up nozzle. It still worked like a champ, though! And yes, it was the Germans who came up with the first operational jet fighter, the Me 262. But they also built half a dozen others as prototypes and experimental aircraft, and it was only economic collapse and poor tactical employment that kept the 262...plus a follow-on jet fighter and a little-known jet bomber called the Ar 234 (I think...someone correct me on the designation if I've recalled it incorrectly)...from having a bigger effect on the course of the war.
Posted by Jim Mathews on July 5,2008 | 12:01PM
I think Kel Jackson is right about why the F-22 needs to be as effective at close range as it is at greater ranges. If the pilot of the F-22 shoots down six adversaries, he may still need to shot down some more planes without going home to re-arm. So the F-22 have to be able to get in some good shots with the AIM-9 or the cannon. So dogfighting will never become obsolete as it will be nessecary when the plane runs out of BVR-missiles, and you would take even greater risks with the 200 million dollar plane if it can't engage in close in fights. About those german WW2 jets; there was several designs from Henschel that did not make it into production for various reasons, not only jets. There was a small production run of planes that used the DB-601A (those planes were used to defend the Henschel factory) that outperformed all contemporary british and german fighters at the time of the Battle of Britain. Fortunely the Luftwaffe were content with the Bf-109.... Henschels jet fighter easely outmanouvered all other german fighters, but they "lost" the contract to the more elegant (and inferior) Me-262. Henschels jets were ready for massproduction much earlier as well.
Posted by freddan on July 12,2008 | 09:19AM
For Jim - good article, but you can't do a Cobra in a military aircraft as easily as you state. Doing this in an F-16 will cause it to depart controlled flight, according to its stability characteristics (AIAA Journal of Aircraft 1973) - but happy to be corrected by any Viper driver! Northrop (& Eidetics) did a lot of work on fighter high-alpha handling during the 70s & 80s, resulting in the F-20's "shark" nose; the basic design premise behind this seems to have been carried on for the F-22 & F-35. They did consider thrust vectoring (particularly for the ND-102) but considered that the additional weight at the back end (aft CG implications) and moving parts in very hot gas flow would be a major maintenance problem. Obviously Lockheed's design team thought otherwise for the F-22, but you'll always get differing design philosophies between different fighter houses. ;-)
Posted by Mike Kim on July 19,2008 | 01:19PM
In response to Kel Jackson - I think it's a mistake to rely on the experience of the Vietnam war, in the issue of relevance of dog-fights. Fifth generation air to air missiles don't need to be stationed exactly "behind" the target in order to lock on it, and be shot. The "cone" of the IR/radar/optics of the missile is very wide, and it can be lunched without "seeing" the target at all. I'm talking about missiles such as the Python 5. Not mentioning future developments.. The fighting aircraft can carry about 4 air to air missiles - I think that by the time they run out, the fight will be over, and no "god-fight skills" will be needed. Fighters usually don't fly alone with significant quantity inferiority.
Posted by Joseph on October 17,2008 | 06:29AM
The 3 panal system used on the X-31, doesn't sound like the poor mans thrust vectoring, it indicates 3D thrust vectoring for both pitch and yaw, while the F-22 has 2D thrust vectoring for pitch. Using 3 panels is how 3D thrust vectoring works, all 3 panals move. It allows for extreme maneuverability. I think the German programmers misunderstood what it was they were looking at.
Posted by Salman on February 13,2009 | 04:23AM
I have reason to believe that all the noise out there regarding the rear of the F-22 is wrong, and deliberately so. Those triangles that stick out the back of the engine cowlings are nothing more than exhaust vector controls. The mount on the V-shaped cutout that you see on all the engine tests. Everything else is a deception. I even found that the museum's copy of the jet is deceptively modified, so that the engine areas have an extra metal frame put over them that shrinks the engine area, which in reality, would prevent maintenance because the engines slide in and out from behind the aircraft. Those triangles are exhaust vector control panels. If all four vector controls were activated at the same time, a pyramid would form that could shut-off the engines completely, if not almost completely. These are the vector controls that allow the aircraft to rotate in place. Without these, the F-22 is merely a smart version of the SST-- which had no lateral controls other than up or down thrusting one bank of engines. As for you F-22 modelers out there?-- keep trying, because the designs I've seen use the center vector control as a single piece, when in reality, there are two vector panels on the inside, back to back, and one each on the outsides of the engines. Anyway, just wanted to show what my son and I figured out over this last weekend. Vasco
Posted by Vasco de Sena on February 23,2009 | 10:04AM