Specific handling the stick for barrel rolls in F 16

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saberrider

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Unread post19 Jul 2018, 20:05

An F 16 pilot talking with me about barrel roll technic , told me this, in order to do barrel roll in F16 one first must apply pressure for the pull then stick is "moved " for rolling . This is because is hard to do mix pressure on the two axis (roll and pitch)or because FLCS not permitted ?
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35_aoa

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Unread post20 Jul 2018, 03:39

I think maybe a little is being lost in translation, but that is generally how you would initiate a barrel roll in any aircraft. You start by pulling back on the stick to get the nose tracking upwards, and then you feed in aileron/rudder in the direction of roll, while maintaining/modulating back stick pressure. If you pulled back on the stick, released, rolled with aileron and didn't maintain back stick pressure, it wouldn't be a barrel roll, but rather a climbing aileron roll. Don't know if that helps. I never just went out and practiced barrel rolls in the F-16, but an ACM/BFM displacement roll is pretty much the same thing, which I did quite a lot of, and I don't remember the mechanics of that being notably different than anything else Ive flown.

Mixing pitch and roll inputs is not difficult at all, though the ergonomics of using a side stick will tend to cause such maneuvers to be more "ratchety" while you are getting used to it. By that, I mean kind of rough angle of bank control when using a lot of backstick pressure at the same time. Beyond that, the only other limitation I can think of is peculiar to the FLCS (and maybe it was addressed in the digital FBW upgraded blocks).....the "don't assault the limiters" adage, when slow. I.e don't be on the AoA limiter, and then also do a yaw rate limit, or roll rate limit input (or all three) at the same time. I don't know the backstory of this.....I assume either an aerodynamic issue, a FLCS processing issue, or both........but smart people told me it was bad, so I believed them :) I think there is an issue of Bill Dryden's "Semper Viper" series in Code One magazine from the early 80's that describes this phenomenon, but I am too lazy right now to dig up exactly which one.
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saberrider

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Unread post20 Jul 2018, 17:53

For sure , first must pitch the a/c and then do the rolling but in the F18 this could have been done better and agresive ( my opinion) in one move diagonally towards your seat.
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johnwill

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Unread post20 Jul 2018, 21:50

Read what 35 aoa said, simultaneous pitch and roll commands are no problem for F-16.
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vilters

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Unread post23 Jul 2018, 12:58

A barrel roll is a combination of a loop and a rol.
You gradually feed in the back pressure to start the loop, and then gradually add the roll to complete the roll.
The result is a "barrel movement".
This is the same for all aircraft.

Now come the F-16 part.

The F-16 has a side stick.
The pilot is NOT sitting directly behind the stick.

Purely due to "human" limitations, body positioning and arm/hand movement? => If you "pull back without thinking about it", you automatically pull and add roll to the left. (The hand pulls towards the body).

That is why in the F-16 the stick movement is "offset" by 12degrees if my memory is still correct.
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planehazza

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Unread post07 Aug 2018, 13:56

I think what the OP is asking, is why is it pull back, pause, and then feed in aileron (SSC path would look like an L ), and not just pull diagonally 45 degrees (SSC path \ ) to feed in roll and pitch from the start.
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saberrider

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Unread post08 Aug 2018, 07:36

planehazza wrote:I think what the OP is asking, is why is it pull back, pause, and then feed in aileron (SSC path would look like an L ), and not just pull diagonally 45 degrees (SSC path \ ) to feed in roll and pitch from the start.

Exactly . Maybe because it is not possible to position the stick .But in GA pull a little and move diagonally. My hint is because the F 16 non linear pitch could do abruptly pitch and overshoot the rolling at various speed

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