F14 High Alpha Departure Characteristics (USN Video)

[Victory205]

Video from the TPS Gang on F14A departure/spin characteristics and recovery procedures that shows what we were dealing with. The video illustrates the severe problems that result from inertial coupling due to sideslip. These are valid for both AFCS F14 variants that we have in the sim, the only difference is that the B is less likely to generate engine stalls. 

As always, using rudder inputs only to roll at high alpha will help keep you out of trouble. Roll, then pull, and wake up those feet!
 

 

Edited July 21, 2024 by Victory205

[RustBelt]

Sideslip has been a constant problem in sims for decades now. The sims just don’t see the side of the fuselage as a lift surface, and so it just can’t cope well modeling relative wind coming from the side. It’s why no sim knife edges well and no sim ever gets crosswind landing quite right.

[=DROOPY=]

And I thought the overwhelming mediocrity of my 'Knife Edge Passes' were due to my poor flying abilities.

Edited July 23, 2024 by =DROOPY=

[f14billy]

thank you for the video! it clearly explains why roll SAS should be off when dogfighting around minute 28. It also explains why when recovering from a flat spin in DCS I noticed that pulling stick aft and into the needle it helps in the recovery in addition to full rudder opposite into to needle. 

Edited July 31, 2024 by f14billy

[jubuttib]

On 7/23/2024 at 3:03 AM, RustBelt said:

Sideslip has been a constant problem in sims for decades now. The sims just don’t see the side of the fuselage as a lift surface, and so it just can’t cope well modeling relative wind coming from the side. It’s why no sim knife edges well and no sim ever gets crosswind landing quite right.

Huh, that's surprising to hear. We've been modeling side forces of the aerodynamic elements and the body in racing sims for at least a decade now.

[Victory205]

It's surprising to hear because it isn't true.

Sideslip (beta) has been modeled since the beginning, and is used for a myriad of calculations that produce the detailed flight modeling. It's constantly being reviewed and tweaked throughout the flight envelope as it has a powerful impact on handling

A jet isn't a light, prop driven aerobatic airplane that produces lift due to propellor flow over the fuselage and tail control surfaces. The real F14 with full rudder in knife edge (at zero G) would result in the nose slowly falling through the horizon. Don't forget, there is a rudder authority limiter that begins at 250 KIAS and is fully engaged at 400 KIAS (9.5º restriction).

  

[Gareth Barry]

Victory205,

In case you havent heard it enough, i want to thank you for all of your input into this module and on this forum. I really cant express how grateful i am.

One thing that i am trying to figure out is, why it would require so much muscle to shove the stick into the corner when in a spin? Please hear me out on this, whoever is reading this, to see where i have a misconception. My understanding (from reading NATOPS)is that the f14 had a very old-school system of providing artificial feel to the pilot, use a cam+roller+springs with bobweights. The bobweight would provide inertia against centripetal acceleration in the longitudinal axis, the the pilot needs to overcome in order to pull back on the stick. This system gives a more-or-less constant 'stick force per g.'

Now with that being said, in a spin, i would have thought that the major vector of acceleration is towards the nose of the plane, the so called 'eyeball-out g'. This, combined with near zero indicated airspeed, would have made me believe that the stick would become quite 'soft.'?

The reason that i ask this, is that i am working on a simple upgrade that could be attached to any of the non force feedback sticks, that would give increased force required in the pitch axis for a given deflection as airspeed increases. This would not be nearly as good as a proper ffb gimbal, but i think might still be a useful upgrade and much much cheaper. However, if there is something about the f14 stick that i am misunderstanding, i would like to re-educate myself.

Thanks to anyone who read through all of this, and sorry if its slighty OT.

[RustBelt]

On 8/1/2024 at 12:43 AM, Victory205 said:

It's surprising to hear because it isn't true.

Sideslip (beta) has been modeled since the beginning, and is used for a myriad of calculations that produce the detailed flight modeling. It's constantly being reviewed and tweaked throughout the flight envelope as it has a powerful impact on handling

A jet isn't a light, prop driven aerobatic airplane that produces lift due to propellor flow over the fuselage and tail control surfaces. The real F14 with full rudder in knife edge (at zero G) would result in the nose slowly falling through the horizon. Don't forget, there is a rudder authority limiter that begins at 250 KIAS and is fully engaged at 400 KIAS (9.5º restriction).

  

I mean it does some tail lateral stability stuff, but most sims never feel right when side slipping. They model surface action but not airflow changes due to that. Or something, beta always feels simplified. It doesn’t feel like your smashing the side of a plane against high speed airflow, especially downstream. 

[Nightdare]

@Rustbelt

 

How does that feel in real life?

[RustBelt]

9 hours ago, Nightdare said:

@Rustbelt

 

How does that feel in real life?

In everything I flew, as the fuselage blocks the downwind wing you get a rocking sort of dutch roll kind of feel, with a yaw oscillation. At high banking you get a distinctive feeling of over banking (which feeds into a spin). 
 

And un-simable, even small side loading of any uncoordinated missalignment with the relative wind is directly noticeable by feel as a sideways leaning feeling. 
 

I’ve flown up to Turboprop Twins and never jets, but do know the TF-51 and CE2 also don’t exactly show proper behavior either. Normal axis always feels the least legit in almost every sim i’ve ever flown. Probably because it’s the most seat of your pants axis.

[Gareth Barry]

Rustbelt, is something like a co-ordinated turn with rudder something you can accurately feel in real life, or is it something requiring an eye on instruments? I find the little white dot thingies on the acm panel of the f14 to not be very useful, they oscillate around so much. Maybe im using them wrong?

[Dragon1-1]

10 hours ago, RustBelt said:

And un-simable, even small side loading of any uncoordinated missalignment with the relative wind is directly noticeable by feel as a sideways leaning feeling. 

It's not un-simable, you just need a 10000$ motion platform to get that feeling.  I've been meaning to make one myself, hopefully for less, but it's on backburner for now. Sadly, a full centrifuge for G simulation is beyond even that.

[fat creason]

22 hours ago, RustBelt said:

And un-simable, even small side loading of any uncoordinated missalignment with the relative wind is directly noticeable by feel as a sideways leaning feeling. 

This just sounds like a crappy aero model tbh. All those things are possible and are done routinely in sims, assuming the engineer knows what they're doing.

[Dragon1-1]

I think he means that when you sit upright in a plane and enter an uncoordinated turn, the "down" direction will no longer be towards the floor, which is very noticeable through your seat cushion interface.  Obviously, it's not really possible to simulate without a motion platform, which makes flying warbirds well, for instance, much harder than IRL, because you have to look at the slip ball and not just operate the rudder by feel. IRL it's supposedly more like balancing on a bike, once you get it you don't even have to think about getting your turn coordinated, nevermind stare at instruments.

[RustBelt]

14 hours ago, Dragon1-1 said:

It's not un-simable, you just need a 10000$ motion platform to get that feeling.  I've been meaning to make one myself, hopefully for less, but it's on backburner for now. Sadly, a full centrifuge for G simulation is beyond even that.

I type rated in the DASH-8 on a Level D sim. It’s still un-simable. Pitch and roll it can fake up to around 45degrees convincingly, and cheat a bit further with heave. But they can’t make you feel like sitting on the nose of a very long plane and being swung around 360 degrees along the normal axis.  Really screws with your head with Single engine procedures and Steep Turns. 

[RustBelt]

17 hours ago, Gareth Barry said:

Rustbelt, is something like a co-ordinated turn with rudder something you can accurately feel in real life, or is it something requiring an eye on instruments? I find the little white dot thingies on the acm panel of the f14 to not be very useful, they oscillate around so much. Maybe im using them wrong?

Yes. You actually almost exclusively fly coordinated by feel. Something that then you compensate for with the instruments when IMC because it can lead you into unusual attitudes when your only reference is “what feels straight down in the seat” A lot of captains I flew with flew feet up on the console and we didn’t have a yaw damper. I hated those legs, we were always slower, burned more gas, and the ride was, not quite bumpy, but less smooth, especially in turns. It’s half of the feeling people hate about flying Turboprop commuters. Because even the ones with YD still favor active rudder input during Autopilot flight. 

The tomcat’s ball is hard and you really don’t chase the ball ever, it’s a secondary to feel. You “step” on the ball to stay coordinated, but the ball is a confirmation tool. Like holding a speed in a car. You use the speedo to reference how you need to adjust. You don’t stare at it to hold speed.
In a sim, it’s the only way you know if you’re coordinated. And it’s hard to chase.

 

Some say the “jet seats” do some level of a job by buzzing one cheek or the other. Yet to try one.

2 hours ago, fat creason said:

This just sounds like a crappy aero model tbh. All those things are possible and are done routinely in sims, assuming the engineer knows what they're doing.

Take it up with god I guess? Cause that’s what it actually does. Please tell me heatblur has at least dragged everyone to an intro flight at least.

13 minutes ago, Dragon1-1 said:

I think he means that when you sit upright in a plane and enter an uncoordinated turn, the "down" direction will no longer be towards the floor, which is very noticeable through your seat cushion interface.  Obviously, it's not really possible to simulate without a motion platform, which makes flying warbirds well, for instance, much harder than IRL, because you have to look at the slip ball and not just operate the rudder by feel. IRL it's supposedly more like balancing on a bike, once you get it you don't even have to think about getting your turn coordinated, nevermind stare at instruments.

Exactly Right! 

[Nealius]

The yaw string is more accurate than the ball. The ball doesn't show actual slip until it's settled down from Newton's 3 forces acting upon it. E.g., bank to the left and you will see the ball swing right (indicating proverse yaw) while the nose reference and yaw string are still straight as an arrow. 

Edited August 5, 2024 by Nealius

[kablamoman]

3 hours ago, RustBelt said:

In a sim, it’s the only way you know if you’re coordinated.

You don't fly coordinated solely by feel. There's a visual element to it as well (ie. rolling around a reference point) that with a bit of practice works really well in most DCS modules, just as it does in real life.

Seat of the pants feel helps, as does becoming familiar with the required control pressures (pedal being coordinated with stick pressure and/or power changes), but if you're flying with proper technique and paying attention to your attitude and reference point, you can absolutely maintain coordination without using the ball in the sim, just as you would in real life flying.

[kablamoman]

@Victory205 Great video, thanks for sharing!

[RustBelt]

21 hours ago, kablamoman said:

You don't fly coordinated solely by feel. There's a visual element to it as well (ie. rolling around a reference point) that with a bit of practice works really well in most DCS modules, just as it does in real life.

Seat of the pants feel helps, as does becoming familiar with the required control pressures (pedal being coordinated with stick pressure and/or power changes), but if you're flying with proper technique and paying attention to your attitude and reference point, you can absolutely maintain coordination without using the ball in the sim, just as you would in real life flying.

Never been able to personally. Never used rotating around a reference point to tell coordination though, so your mileage may vary / everyone learns this stuff differently.

Edited August 5, 2024 by RustBelt