Adverse yaw and the F-4

[Stingray72 6]

Hi all!!!

 

A few weeks ago I saw a post, another one lol, regarding flying and fighting in the F-4. There were some good things in it, and I had mentioned some stuff about adverse yaw. A few days ago I found this and wanted to put it up for all the Rhino lovers, it goes pretty in detail about adverse yaw without confusing the folks who have a tough time with science description and lawyer speak.....people like me!! They came from a website who's nae I can't recall this instant, but I have it saved in my favs at work so I will post credit as soon as I am able to. Also, I looked for the other post but was unable to locate it, so...............

 

"In the low-speed regime during a dogfight, the F-4 was prone to what was called adverse yaw- normally when the pilot wanted to turn one direction, he only had to move the stick in that direction. At low speeds and high angles of attack that were commonplace in a dogfight, however, if a pilot pushed the stick to the left, the downward-deflected aileron on the right wing would produce more drag than lift, causing the Phantom to yaw back to the right even though the pilot wanted to turn left. As the yaw increases, the effective sweep on the left wing decreases and it starts to produce more left and the F-4 snaps to the right and then into a spin. All this happened nearly instantly and pilots had to compensate for the adverse yaw when rolling left or right by using the rudder aggressively during close air combat- instead of moving the stick into the direction of the turn, the rudder was deflected. So a left turn meant keeping the stick centered and pushing the left rudder pedal down. This causes the Phantom to yaw to the left and this decreases the effective sweep on the right wing- it therefore creates more lift and the plane now snap rolls into the direction of the turn. This took a lot of practice and it was suspected that a significant number of Phantom combat losses were due to adverse yaw conditions."

 

"But the F-4Es had another advantage and that was what was called a "soft wing"- the wing now had leading edge slats that were controlled automatically by the flight control system whenever the angle of attack would reach a certain level. When the AoA hit this preset level, the slats would automatically pop out and it increased the lift across the wing- this had a dual effect on the Phantom- it eliminated the adverse yaw condition, even at high angles of attack. And secondly, the Phantom became practically spin proof as adverse yaw got eliminated- accidents from spins dropped dramatically and pilots could now haul around the beast in the sky without worrying about loss of control. In fact, some pilots felt that the soft wing F-4E flew just like the Northrop T-38 Talons used in advanced flight training."

 

I am also pretty sure that the Adverse yaw issue was not straightened out in the F-100 by adding a larger tail surface. If you read John Boyd's biography you will see that he figured out how to fly the Hun much like the F-4 guys did.

 

MOG_Gunfighter

[turkeydriver 4]

Good stuff there.

 

In the SF series, the are unmodded F-4Es and then modded (1973?) F-4Es with the slats-I've not done any testing to see if they work other than give you a better turn. I'd love to find out though.

[+Cliff7600 1,120]

Thanks for sharing

[ezlead 42]

If you're gonna fly a fighter,you better learn to use rudder. All Attack pilots and Fighter pilots use rudder to help the turn(roll) rate. You will notice that on all more modern jet attack and fighter aircraft the rudder/rudders are above the longitudinal axis of the aircraft. Instead of a severe yaw,you get a yaw with a roll.

[busdriver 35]

We also had Angle of Attack (AOA) indexer lights above the glareshield, when the donut in the middle was illuminated you were pulling optimum AOA, at the same time the aural tone in your ear was nice and soothing. During an approach to landing (around the final turn or on a straight in) the donut was your target AOA, it also happens to be optimum maneuvering AOA. As you exceeded optium AOA (19.2 units in the hard wing F-4) the V above the donut came on (both at same time meaning slightly slow) and if you continued to pull only the V illuminated...think of it as telling you to point the nose down ("Unload for Control" was the name of the film put out to all F-4 RTUs/RAGs). And by now the aural tone was a rapid fire (looking at a Dash 1 it says the "your AOA is too high, you're too slow" tone was 20 pulses per second with a frequency of 1600 Hz.). Above 22.3 units AOA the nosegunner would feel his left rudder pedal shake (think rapid fire chattering). The rule of thumb a new AF Phantom guy learned was, when you hear the beep, use your feet. When the AOA aural tone started (at 15 units) that's when you centered the stick laterally and used your rudder pedals to roll. So around the final turn in the overhead pattern you smoothly pushed on the rudder pedals to control the radius of the turn. During BFM...say during your gun defense when the Gomer was trapped about 1500 feet in the saddle, stomping on the rudder pedal (with the stick snuggly pulled full aft) would get your out of plane maneuver.

 

The F-16 on the other hand...no aural tone, no pedal shaker. We (some guys) put our feet flat on the floor and hooked our toes under the rudder pedals during BFM. Otherwise you simply rested your feet on the pedals, but pedal pressure was always light. It was most definitely something different. But not unlike they way we flew the T-38. You had to be cautious with rudder inputs at high AOA in the T-38. Once a UPT grad got to Fighter Lead In, then he/she was taught to use their feet more.

[dare2 0]

Hi all!!!

 

A few weeks ago I saw a post, another one lol, regarding flying and fighting in the F-4. There were some good things in it, and I had mentioned some stuff about adverse yaw. A few days ago I found this and wanted to put it up for all the Rhino lovers, it goes pretty in detail about adverse yaw without confusing the folks who have a tough time with science description and lawyer speak.....people like me!! They came from a website who's nae I can't recall this instant, but I have it saved in my favs at work so I will post credit as soon as I am able to. Also, I looked for the other post but was unable to locate it, so...............

 

"In the low-speed regime during a dogfight, the F-4 was prone to what was called adverse yaw- normally when the pilot wanted to turn one direction, he only had to move the stick in that direction. At low speeds and high angles of attack that were commonplace in a dogfight, however, if a pilot pushed the stick to the left, the downward-deflected aileron on the right wing would produce more drag than lift, causing the Phantom to yaw back to the right even though the pilot wanted to turn left. As the yaw increases, the effective sweep on the left wing decreases and it starts to produce more left and the F-4 snaps to the right and then into a spin. All this happened nearly instantly and pilots had to compensate for the adverse yaw when rolling left or right by using the rudder aggressively during close air combat- instead of moving the stick into the direction of the turn, the rudder was deflected. So a left turn meant keeping the stick centered and pushing the left rudder pedal down. This causes the Phantom to yaw to the left and this decreases the effective sweep on the right wing- it therefore creates more lift and the plane now snap rolls into the direction of the turn. This took a lot of practice and it was suspected that a significant number of Phantom combat losses were due to adverse yaw conditions."

 

"But the F-4Es had another advantage and that was what was called a "soft wing"- the wing now had leading edge slats that were controlled automatically by the flight control system whenever the angle of attack would reach a certain level. When the AoA hit this preset level, the slats would automatically pop out and it increased the lift across the wing- this had a dual effect on the Phantom- it eliminated the adverse yaw condition, even at high angles of attack. And secondly, the Phantom became practically spin proof as adverse yaw got eliminated- accidents from spins dropped dramatically and pilots could now haul around the beast in the sky without worrying about loss of control. In fact, some pilots felt that the soft wing F-4E flew just like the Northrop T-38 Talons used in advanced flight training."

 

I am also pretty sure that the Adverse yaw issue was not straightened out in the F-100 by adding a larger tail surface. If you read John Boyd's biography you will see that he figured out how to fly the Hun much like the F-4 guys did.

 

MOG_Gunfighter

 

Why on hearth would you go in this part of an F-4 flight envelop?

 

It's the second "Coffin corner" of an F-4, it's heavy, doesn't have loads of lift and has limited turning capabilities, so keep your airspeed up and use the vertical plan, keep your AOA as low as possible below 400 kts and you'll be fine.

Edited May 29, 2013 by dare2

[dare2 0]

"In the low-speed regime during a dogfight, the F-4 was prone to what was called adverse yaw- normally when the pilot wanted to turn one direction, he only had to move the stick in that direction. At low speeds and high angles of attack that were commonplace in a dogfight, however, if a pilot pushed the stick to the left, the downward-deflected aileron on the right wing would produce more drag than lift, causing the Phantom to yaw back to the right even though the pilot wanted to turn left. As the yaw increases, the effective sweep on the left wing decreases and it starts to produce more left and the F-4 snaps to the right and then into a spin. All this happened nearly instantly and pilots had to compensate for the adverse yaw when rolling left or right by using the rudder aggressively during close air combat- instead of moving the stick into the direction of the turn, the rudder was deflected. So a left turn meant keeping the stick centered and pushing the left rudder pedal down. This causes the Phantom to yaw to the left and this decreases the effective sweep on the right wing- it therefore creates more lift and the plane now snap rolls into the direction of the turn. This took a lot of practice and it was suspected that a significant number of Phantom combat losses were due to adverse yaw conditions."

 

 

Something else; something one learns from the very first flight: Never use the ailerons at high AoA/low speeds but the rudder instead.

 

One particular reason is that in this part of your flight envelop, you are close to stall, using the ailerons will increase wing camber in one side and decrease it in the other side therefore increasing the stall speed in the second wing, so with an aircraft with this sort of characteristics, you'll either avoid this part of its flight envelop or turn with the rudder instead of the ailerons.

 

What you want in any case is to avoid assymetric stall.

[xrearl 27]

thanks for the posts, very informative.