"Pedal turn" versus "Conventional turn"

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gta4

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Unread post04 Apr 2017, 17:16

I strongly suspect that J-turn is the so-called "pedal turn" because Lockheed Martin uses J-turn as a sample maneuver that F-35 can perform using high alpha yaw.
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collimatrix

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Unread post13 Apr 2017, 14:21

Could the formation of asymmetric vortices over the fuselage forebody have something to do with it?

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I'm wondering if the pedal turn exploits controlled nose slice.
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steve2267

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Unread post13 Apr 2017, 14:58

What is the source for your graphic? Book? Periodical? (Because I'd like to read it.)

I believe the graphic depicts a condition that occurs with a cylindrical (or continuously smooth) cross section. E.g. F-15 nose.

However, I believe the existence of nose chines (F-22/F-35) or leading edge root extensions (LERX or strakes - F/A-18, F-16), fix or otherwise control the creation / shedding of the vortices. You may very well get asymmetric vortex shedding at higher angles of attack, but the chine/LERX will fix the location of the vortex attach / shed point. There is a flow constant (the name of which I forget at the moment) that is used to characterize the frequency of vortex shedding. In the case of higher angles of attack, I believe asymmetrical vortex shedding will occur at such a rate that you would get alternating left/right components of the forebody lift force. I believe this is one (prominent) source of buffet. I do not believe you can control it for nose slice as I suspect the shedding frequency is (somewhat) unpredictable and the too high (or too quick).

Nice illustrations.
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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Unread post13 Apr 2017, 18:37

It's from Ray Whitford's Design for Air Combat.

And it is a really fantastic book.
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Unread post14 Apr 2017, 02:18

I remember seeing similar images in a paper introducing F-18's pirouette maneuver.

Does pirouette and J-turn resemble?

https://forums.vrsimulations.com/forums ... 53&start=0

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Unread post11 Jun 2017, 18:25

more pics from technical papers:
J-turn F-35 pedal turn.jpg
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smsgtmac

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Unread post12 Jun 2017, 03:55

Just an FYI...JIC.
That first tech paper snippet is from the 2014 AIAA paper "F-35A High Angle-of-Attack Testing", authored by a Mr. Steve Baer, (Lockheed Martin "Aeronautical Engineer, Flying Qualities" at Edwards AFB), and presented to the Atmospheric Flight Mechanics Conference held between 16 and 20 June 2014, in Atlanta, Georgia. It is a key bit of evidence that debunks the "F-35 losing to a F-16D in a dogfight" meme. The CLAW testing that was mischaracterized in the 2015 faux dogfight story was described a year earlier by Mr. Baer.

J-turns are described by the originator of the 'Herbst Manuever' (and the term supermaneuverability itself) , Dr W.B. Herbst. As I understand it, the difference between the J-Turn and Pedal turn is mostly about the order in which rotations about different axes occur, maybe somewhat to how far into the post-stall environment is important too. As the nose falls during the post-stall rolling, the movement has been described as 'coning'. It appears that the J-Turn primarily involves rolling at the apex of the climb first, and the Pedal turn appears to involve turning about the Yaw axis to bring the nose on point. At the time, Herbst claimed thrust vectoring was required to do a J turn, but who knows with 40K thrust engines, modern flight control laws and big honking control surfaces?
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rheonomic

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Unread post12 Jun 2017, 20:49

smsgtmac wrote:J-turns are described by the originator of the 'Herbst Manuever' (and the term supermaneuverability itself) , Dr W.B. Herbst. As I understand it, the difference between the J-Turn and Pedal turn is mostly about the order in which rotations about different axes occur, maybe somewhat to how far into the post-stall environment is important too. As the nose falls during the post-stall rolling, the movement has been described as 'coning'. It appears that the J-Turn primarily involves rolling at the apex of the climb first, and the Pedal turn appears to involve turning about the Yaw axis to bring the nose on point. At the time, Herbst claimed thrust vectoring was required to do a J turn, but who knows with 40K thrust engines, modern flight control laws and big honking control surfaces?


IIRC that was one of these two papers in Journal of Aircraft...
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Unread post13 Jun 2017, 00:35

smsgtmac wrote:Just an FYI...JIC.
That first tech paper snippet is from the 2014 AIAA paper "F-35A High Angle-of-Attack Testing", authored by a Mr. Steve Baer, (Lockheed Martin "Aeronautical Engineer, Flying Qualities" at Edwards AFB), and presented to the Atmospheric Flight Mechanics Conference held between 16 and 20 June 2014, in Atlanta, Georgia. It is a key bit of evidence that debunks the "F-35 losing to a F-16D in a dogfight" meme. The CLAW testing that was mischaracterized in the 2015 faux dogfight story was described a year earlier by Mr. Baer.

J-turns are described by the originator of the 'Herbst Manuever' (and the term supermaneuverability itself) , Dr W.B. Herbst. As I understand it, the difference between the J-Turn and Pedal turn is mostly about the order in which rotations about different axes occur, maybe somewhat to how far into the post-stall environment is important too. As the nose falls during the post-stall rolling, the movement has been described as 'coning'. It appears that the J-Turn primarily involves rolling at the apex of the climb first, and the Pedal turn appears to involve turning about the Yaw axis to bring the nose on point. At the time, Herbst claimed thrust vectoring was required to do a J turn, but who knows with 40K thrust engines, modern flight control laws and big honking control surfaces?


Thanks for the explanation. In the past I could not distinguish J-turn from pedal turn and pirouette.
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Unread post20 Jun 2017, 16:27

Finally, the pedal turn.

It is incredible that F-35 has such a high pitch rate, and such a high yaw authority.

I believe this maneuver could dominate all non-thrust-vectored aircrafts, including Typhoon, Gripen, Mig-29 and Su-27.

During the initial backflip, the initial pitch rate is amazing, and the whole 270 deg took less than 8 seconds. Faster than any non-thrust vectored jets.

The 360 pedal turn that followed is much faster than any conventional turns performed by other non-thrust-vectored jets.

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This maneuvers allows F-35 to turn inside of any non-thrust-vectored jets.

https://www.youtube.com/watch?v=hkAmQpkrHZc
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castlebravo

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Unread post20 Jun 2017, 18:45

gta4 wrote:Finally, the pedal turn.

It is incredible that F-35 has such a high pitch rate, and such a high yaw authority.

I believe this maneuver could dominate all non-thrust-vectored aircrafts, including Typhoon, Gripen, Mig-29 and Su-27.

During the initial backflip, the initial pitch rate is amazing, and the whole 270 deg took less than 8 seconds. Faster than any non-thrust vectored jets.

The 360 pedal turn that followed is much faster than any conventional turns performed by other non-thrust-vectored jets.

Image

This maneuvers allows F-35 to turn inside of any non-thrust-vectored jets.

https://www.youtube.com/watch?v=hkAmQpkrHZc


It's cool to watch, and it's a great demonstration of the F-35's control authority at low speed, but I doubt the utility of that maneuver (or any other post-stall maneuver) in actual combat. All the opponent needs to do is go vertical, avoid stalling alongside the F-35, then come back down on it with guns or a heater. Of course, this is all assuming the mythical 1v1 dogfight where both fighters lack a HOBS missile, otherwise it never gets to this point.
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Unread post20 Jun 2017, 18:51

castlebravo wrote:
gta4 wrote:Finally, the pedal turn.

It is incredible that F-35 has such a high pitch rate, and such a high yaw authority.

I believe this maneuver could dominate all non-thrust-vectored aircrafts, including Typhoon, Gripen, Mig-29 and Su-27.

During the initial backflip, the initial pitch rate is amazing, and the whole 270 deg took less than 8 seconds. Faster than any non-thrust vectored jets.

The 360 pedal turn that followed is much faster than any conventional turns performed by other non-thrust-vectored jets.

Image

This maneuvers allows F-35 to turn inside of any non-thrust-vectored jets.

https://www.youtube.com/watch?v=hkAmQpkrHZc


It's cool to watch, and it's a great demonstration of the F-35's control authority at low speed, but I doubt the utility of that maneuver (or any other post-stall maneuver) in actual combat. All the opponent needs to do is go vertical, avoid stalling alongside the F-35, then come back down on it with guns or a heater. Of course, this is all assuming the mythical 1v1 dogfight where both fighters lack a HOBS missile, otherwise it never gets to this point.


The first part of the maneuver (the backflip part) is not a post stall maneuver. In fact it is very close to a conventional loop, with a significant smaller radius and higher angular velocity.

If the enemy goes vertical, F-35 could easily pitch up with its amazing initial pitch rate, and follow the enemy with its small loop radius. I believe it could put the enemy in its crosshair throughout the maneuver, even though the enemy may be higher than F35.
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Unread post20 Jun 2017, 19:58

That "back flip" leaves the jet with less airspeed than is needed for level flight, and puts it into what would be a spin for most other aircraft. At that point, the jet is falling out of the sky until it gains enough smash to resume normal flight; there is no way it is going to pull into the vertical unless LockMart snuck in a reaction control system and a motor with double the thrust while no one was looking. The 5th-gen trick is a limited ability to maintain control of the nose (at least in the bottom hemisphere) while stalled out and falling like a leaf. This is IMO superior to the near unless ability of some Russian jets to depart controlled flight, and recover with a reasonably predictable attitude.
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Unread post20 Jun 2017, 23:22

castlebravo wrote:That "back flip" leaves the jet with less airspeed than is needed for level flight, and puts it into what would be a spin for most other aircraft. At that point, the jet is falling out of the sky until it gains enough smash to resume normal flight; there is no way it is going to pull into the vertical unless LockMart snuck in a reaction control system and a motor with double the thrust while no one was looking. The 5th-gen trick is a limited ability to maintain control of the nose (at least in the bottom hemisphere) while stalled out and falling like a leaf. This is IMO superior to the near unless ability of some Russian jets to depart controlled flight, and recover with a reasonably predictable attitude.



This seems to jibe with my understanding that US pilots would never intentionally depart from controlled flight during flight demos.That's test pilot stuff.
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Unread post21 Jun 2017, 15:58

castlebravo wrote:
It's cool to watch, and it's a great demonstration of the F-35's control authority at low speed, but I doubt the utility of that maneuver (or any other post-stall maneuver) in actual combat. All the opponent needs to do is go vertical, avoid stalling alongside the F-35, then come back down on it with guns or a heater. Of course, this is all assuming the mythical 1v1 dogfight where both fighters lack a HOBS missile, otherwise it never gets to this point.


I disagree. If at the merge, the F-35 goes vertical, but the bogey remains in a (more or less) horizontal turn, this maneuver enables the F-35 to stay at the center of the bogey's turn and point its nose at the bogey with impunity.

If the bogey goes vertical as well, then I think you are set up for vertical, rolling scissors. The F-35 pilot will have to go to Plan B as he probably won't be able to simply pedal turn his nose at the bogey. However, in the Jon Venable article where he interviewed F-35 pilots and asked them to compare the F-35 to their former steed, ALL pilots said the F-35 was (vastly?) superior to their previous aircraft with regard to scissors. So if the bogey also goes vertical, and rolling scissors ensue, the bogey is still playing into the hands of the F-35.
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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