knife edge flight...how?

[Ala12Rv-watermanpc]

Hi, this may sound stupid (and probably it is :D) , but for some reason, I cant manage to do a proper knife edge flight with ANY plane in DCS and I would like to know why???

 

I think it should be pretty easy, just put wings 90º over the horizontal and apply rudder/yaw to the foot looking at the sky...the problem is, no matter how much yaw I apply, NO PLANE cant sustain that state of reduced lift and it starts falling to the ground pretty badly so I have to recover after a couple of seconds.

 

I have seen lots of videos where pilots seem to easily maintain that configuration through the whole fly by and beyond...what am I doing wrong??:huh:

 

I posted this here because there are many planes in the FC3 "module" but it happens actually with every single plane...

 

For example, look at this video at 6:44sec

 

 

looks to me like the plane is maintaining very well the knif edge flight...

[ricktoberfest]

Make sure you lift the nose before flipping on your side, and have enough speed. Other than that it's hard to say without seeing what you're doing.

 

 

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[Shahdoh]

Not all a/c are capable of sustained knife edge flight either. Increase the speed, get the nose up higher as mentioned and put it on edge. The Mustang for instance will not hold it more then 5-10 seconds depending on entry airspeed, maybe a bit longer, been a while since I have done it.

[esb77]

Keep in mind that you are creating an illusion of level flight.

 

In reality, if you roll 90 degrees you're basically skydiving while wearing an airplane. You and the airplane are in freefall, and preserving the illusion doesn't last long. In the video he only holds a full edge on position for 4 or 4.5 seconds.

 

There are a bunch of things that contribute to maintaining the illusion from the airshow audience viewpoint.

 

Lack of visual references. They're looking up, ideally enough so that any ground references are in their peripheral vision. This makes it hard to see that the plane is not truly flying in a straight and level path.

 

Viewing angle. Again, being high enough in the field of view gives you an edge. By forcing the view to be at an angle from below, the vertical rise and fall of the airplane creates less angular displacement for a ground observer than would be apparent to an aircraft flying straight level, and in line abreast formation with you.

 

Starting with a positive vertical velocity. If you're climbing at 5 m/s when you roll fully 90 degrees, then it's going to take a second or so before your vertical velocity drops to zero and you start falling. Assuming of course that you make your roll in a way that doesn't bleed off that vertical velocity.

 

Slight upward yaw. The side of the plane will generate a slight amount of lift this way and your engine thrust vector will also have a slight upward component. You'll still be in freefall, probably faster than a skydiver in a wingsuit, but every bit helps.

 

Not really rolling the full 90 degrees. Keep it at 80 degrees and pull a slight turn, and you'll get a bit of upward lift, but it will be very hard for ground viewers to detect this.

 

 

Short duration. Typically it is only done for a few seconds. The one in the video was pretty long, and it lasted about 4.5 seconds.

 

 

At the end of the day, level flight while rolled 90 degrees is an illusion.

Seventy million dollars is not enough to buy an exemption from the laws of physics.

 

Edit: Forgot to mention that extra altitude also helps, the farther up you are the longer you can fall before they start to notice.

 

 

If you just want edge flight, and don't care about pretending to be in level flight, then just start at higher altitude, keep airspeed up, and hope your fuel system pickups are still submerged.

 

If you're having trouble with not enough yaw to keep the nose level or slightly up you can on twin engine planes throttle down the upward engine to give it a bit more nose up yaw.

Edited February 17, 2017 by esb77

[riproren]

Yup, kind of an illusion in air shows. In a jet, at 350kts and accelerating, put it on edge and gently pull back on the stick. As you see your airspeed drop, gently apply more power.

 

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[SinusoidDelta]

Here is how the F-15C demonstration team performed the knife edge pass

[Ala12Rv-watermanpc]

Nice info guys!!, really appreciate it!!:thumbup:

 

@esb77, I knew at the end of the day it is an ilusion but as you said, in this video and others I remember it seems like those pilots are really skilled because in some of them I would have swear they were maintaining that unstable maneuver forever (which is not possible).

 

Also, despite I gently apply a nose up (10/20º) before starting the manouver I feel like I cant manage to keep the fly by as long as the one in the video for example, before my nose starts falling very quickly and cant do it for more than 2,5/3 secs before its too evident Im looking at the ground.

 

Maybe the speed is the problem...I remember trying at 350/400 knots in the SU-27/mig-29 but might not be enough. Of course more speed should lend for little more sustained maneuver fly by.

 

@SinusoidDelta, great info there mate!!!:thumbup: thanks for sharing...I will try exactly at those parameters and see what happens. I also like how the manual says to apply "forward stick pressure" which is exactly what happens in DCS also as soon as you try this maneuver...as soon as you start applying yaw, the plane makes a slowly positive g turn which you must compensate with negative g stick movement.

 

I will try all what you told me and come back to share my improvements, thanks a ton guys!!:thumbup:

[SinusoidDelta]

 

@SinusoidDelta, great info there mate!!!:thumbup: thanks for sharing...I will try exactly at those parameters and see what happens. I also like how the manual says to apply "forward stick pressure" which is exactly what happens in DCS also as soon as you try this maneuver...as soon as you start applying yaw, the plane makes a slowly positive g turn which you must compensate with negative g stick movement.

 

I will try all what you told me and come back to share my improvements, thanks a ton guys!!:thumbup:

 

No problem! In my opinion the maneuver doesn't look quite right when performed in DCS compared to videos from air shows but it certainly do-able.

[Ironhand]

...

In reality, if you roll 90 degrees you're basically skydiving while wearing an airplane.

 

...

 

At the end of the day, level flight while rolled 90 degrees is an illusion.

Seventy million dollars is not enough to buy an exemption from the laws of physics.

 

...

??? I'm sorry but that's not how it works. Lift is lift whether you are flying level, on your side, or upside down. It's just a matter of directing it where you need it.

 

Watermanpc,

 

See the attached track. It's not the best in the world but basically level and lasts until the engines become fuel starved and which point I level out so they can get fuel again. Made with my beloved Flanker...

[Ala12Rv-watermanpc]

I also though that before or after that configuration was unstable (in most planes) but of course I guess it all depends on how much lift the vertical stabilizers can generate and the amount of yaw thay can provide. Will check your track mate!, thanks!;)

 

EDIT: Done, I have just saw you track, very nice pass!! looks like the speed was my mistake, I was trying to do it very slow...will try for my self, thanks a lot!!

Edited February 18, 2017 by watermanpc

[SinusoidDelta]

??? I'm sorry but that's not how it works. Lift is lift whether you are flying level, on your side, or upside down. It's just a matter of directing it where you need it.

 

Watermanpc,

 

See the attached track. It's not the best in the world but basically level and lasts until the engines become fuel starved and which point I level out so they can get fuel again. Made with my beloved Flanker...

 

Right. In a knife-edge the lift vector is pointed in the horizontal direction, forward stick pressure keeps the flight path straight. Top rudder (i.e., the top or highest rudder pedal when in the bank) generates the yaw force and side slip to hold the velocity vector above the horizon.

[Ironhand]

...looks like the speed was my mistake, I was trying to do it very slow...will try for my self, thanks a lot!!

For the Flanker, right around 850 km/hr works well for sea level. Haven't a clue as to the proper speed for other lesser ( :) ) aircraft.

 

Enjoy your flights. It's a lot of fun.

 

SD,

 

Nice explanation.

[Stuge]

Try high speed and asymmetrical thrust. In the Su-27 asymmetric thrust gives you that extra lift that you need to make good knife edge. And if you fly straight as an arrow there's no fuel starvation. And go faster than 700-800 km/h.

 

FC3 planes with old flight models can do knife edge easily without asymmetric thrust. You just need to be fast enough.

 

F-15C remains untested for this yet, maybe someone could? :)

[Ala12Rv-watermanpc]

thanks all guys, finally I was able to make a proper sustained low level knife edge pass!!:thumbup::thumbup:

 

Using increased speed as well as asymmetric thrust (even only with the first) it worked like a charm, very similar to the video I posted...damn, I cant believe how stupid I was :doh:, for some reason I insisted in the low speed in my attemps and thus it didnt work, as simple as that :D:doh:

 

Again, thanks all guys for your help!!:thumbup::thumbup: