realistic drag? Or gaining too much lift?

Hi there.

At first let me say, I don't have any knowledge of the real bird.

Now, I am experiencing the F-86 having sort of almost none drag at upper speeds. If you cut off throttle down to idle you can glide enormous distances. You can even keep a climb but are losing speed only so slowly.

Also if i pull the stick only a bit, having the ADI pointing the nose slightly above the horizon, I get huge climb rates instantly, mostly with my pilot coughing due to the G-load. It is very rare you can keep the bird steady for longer than a few seconds without getting into climb or descent rates beyound 1000 ft per minute. You can trim, but trimming affects the bird way slower than your next unintentional climb.

Biggest problem being the huge climb/descent rates without having a significant shift of the horizon out of your cockpit. You have to watch your VSI constantly to hold level flight and this is not an easy task with your stick in the LOS to that instrument, even with TIR.

I believe it's a realistic behavior for an unaugumented aircraft, traveling at speeds in excess of say 450 knots, to be very responsive in pitch resulting in high instantaneous climb/descent rates.

When flying in an IFR like fashion I recommend keeping the speed below 400 IAS (or maybe lower) when cursing, if constant altitude is a recuirement. Remember the higher you go the higher TAS you will get from a given IAS, so 300kts at 20 000 might still be an acceptable speed but the aircraft is probably less sensitive in pitch.

I have no idea regarding the drag though!

Something to do with high altitude first, and then keeping the low drag from high into the lower altitudes?

I noticed this too, when I ended up loosing control after gaining +550 mph at low altitude, and this plane should be controllable at +1 mach.. Even turning high G's 4-6 didn't slow it down below 550, at 95% throttle.

Is this a known bug, or something new?

F-86F Drag test.trk

Something to do with high altitude first, and then keeping the low drag from high into the lower altitudes?

 

I noticed this too, when I ended up loosing control after gaining +550 mph at low altitude, and this plane should be controllable at +1 mach.. Even turning high G's 4-6 didn't slow it down below 550, at 95% throttle.

 

Is this a known bug, or something new?

Controllable at Mach 1? Please give a source, everything i've read clearly state the opposite.

Controllable at Mach 1? Please give a source, everything i've read clearly state the opposite.

Could be the engine stalls at redline, but the training video from US Airforce says it's fully controllable to redline, or 593miles at sealevel. And I loose control just after passing 550-560mph.

In theory the plane would be controllable at high speed dive, if it didn't loose hydraulic pressure from engine stall because of the moving tailfin. At least this would make the pitch control available.

Now it behaves kind of more like a MiG-15 i asume.

http://www.wmof.com/F-86.html

The forerunner of the operational Sabre was the XF-86, first flown Oct. 1, 1947 and became the first aircraft to fly at Mach 1 in a routine flight.

The F-86 is a clean plane with a relatively high aspect ratio wing (compared to modern fighters). It shouldn't be all that draggy. I didn't notice anything that seemed obviously wrong when flying it. Maybe I'll look again.

The F-86 is a clean plane with a relatively high aspect ratio wing (compared to modern fighters). It shouldn't be all that draggy. I didn't notice anything that seemed obviously wrong when flying it. Maybe I'll look again.

You have to fly up to high altitude first, it seems the drag at the highest altitude seem to get stuck in afm all the way down again.

Edit I did a airstart at 5000 only, at 500mph, and the plane behaved nicely, and was controllable at 600mph too. So something happens during that dive i think. But it wasn't hard to get 600, just dived slowly and gained speed, and i kept it moving back to 5000feet too.

I looked at your track and I see what you mean. The drag at high speed was lower than expected.

MPH doesn't say much. Mach is the important factor. And from what I've read the Sabre start to experience difficulties around M0.95+.

So avoid transonic speeds, and supersonic speeds are a disaster if you happen to make it through.

from what i remember seeing, the F86 IDLES Higher as you Gain Alt

You have to fly up to high altitude first, it seems the drag at the highest altitude seem to get stuck in afm all the way down again.

Well that sounds like a pretty serious bug.

So avoid transonic speeds, and supersonic speeds are a disaster if you happen to make it through.

How is it a disaster? The Sabre was the first US fighter jet to be able to dive past Mach 1, and there are multiple accounts of it happening uneventfully. It's also fine in the game, although it takes more attention to keep it straight and true.

Could be I'm a little confusing trying to explain what happened in my first post this thread, I'll try be more spesific. And I mistakingly was hung up from a multiplay dive I didn't bother looking back on, because the track was long. I basicly was in a turn, and only had yaw control, but I also had pitch control, but somehow I forgot that. ( Maybe because I crashed just seconds later ).

The reason I take this up, is a modification on the F model, that could be more useful in transonic speed than the DCS F-86F seem to have, I'm well aware this is only my opinion based on other transonic shockwave information, one is the shuttle's front, that push the shockwave outside ailerons.

I'll try explain this here;

I could be wrong, but this new little fin, is probably blocking the transonic shockwave, that would make it much harder to have aileron control on older F-86's. It's not 100% effective, but I asume it would help in a dive.

And I also experienced something I'm not sure is correct, just below transonic speed I also lost aileron control, during a high G turn.

I'll try to show this in a video here;

And that last blackout, touching -3G a short moment, really?

Good post! I'd love to hear a response regarding the correctness of the behaviour in that video.

Interesting diagrams, Buz. Although I'm not too certain about how the shocks might affect aileron control, I also know that it isn't as simple as drawing lines from nose at an arbitrary angle.

The angle of the shock front relative to a location is based on the Mach number of the aircraft. A plane just barely reaching Mach 1 is unlikely to have a shock front angle so acute. Additionally, the shape of the sabre's nose is likelier to produce a parabolic bow shock rather than an oblique one (which is shown in your diagram), which is a different mess entirely.

This is a T-38 model creating oblique shocks.

This one is an XB-70. I can't say the Mach numbers exactly, but thre are charts in some of my textbooks which detail how to calculate the exact angle, Mach numbers, stagnation pressures and other properties before and after the shock based on Mach number and the angle of the object relative to freestream airflow.

Looking at more Transonic videoes, it's possibly not shockwave, but a transonic wave this extra fin shifts, almost like vortex generators.

But I'm still kind of guessing.

This one kind of explains it.

Not to put too fine a point on it, the guesswork is rather obvious.

Wing fences. You may want to Google that.

Not to put too fine a point on it, the guesswork is rather obvious.

 

Wing fences. You may want to Google that.

Maybe you could tell us why they put in that little airfoil on the wing then? .....

Edit; Ok, I finally googled it, kind of small for a Fence, but ok, if it does the trick.

But not too far away from my guessing, or?

http://gtae6343.wikia.com/wiki/Stall_Fences

For aircraft with swept wings, the local flow along the wing is not in the direction of flight. There is also a spanwise flow along the wing from the center toward the tips. This causes the boundary layer to thicken towards the tips, making them more susceptible to stalling than the inboard portion of the wing. This is dangerous because the ailerons, used to control roll, are located near the wing tips (where they will have the greatest moment arm). If the tips stall the ailerons will lose their effectiveness, making the aircraft uncontrollable.

Edit#2; Or is it the higher aoa on wings, that make airflow on top go into transonic speed? (I guess this could be it, and i really learned something today)

0:42 , if you really need to save time...

Looking at more Transonic videoes, it's possibly not shockwave, but a transonic wave this extra fin shifts, almost like vortex generators.

But I'm still kind of guessing.

 

This one kind of explains it.

I don't think there is a difference between these. A shock is a shock. They may differ in strength and location/angle but there is no "transonic shock" that differs in properties from a supersonic shock. By this, I mean formulas to calculate properties of shocks remain the same for shocks in general. There are, however, expansion waves which are not shocks but are Mach waves that increase the speed which is what happens when supersonic air moves around something that is expanding. Also, vortex generators are completely unrelated, as are the wing fences. The fences on the Sabre simply "reset" the span wise flow which gets worse at high AoA and worse as you move outboard from the fuselage.

I don't think there is a difference between these. A shock is a shock. They may differ in strength and location/angle but there is no "transonic shock" that differs in properties from a supersonic shock. By this, I mean formulas to calculate properties of shocks remain the same for shocks in general. There are, however, expansion waves which are not shocks but are Mach waves that increase the speed which is what happens when supersonic air moves around something that is expanding. Also, vortex generators are completely unrelated, as are the wing fences. The fences on the Sabre simply "reset" the span wise flow which gets worse at high AoA and worse as you move outboard from the fuselage.

 

I know I didn't use that much time to get the wording more correct. But to me it was more important to understand it was logic this happened, not needing to really know what the different zones of speed was called.

And I'm quite impressed with Belsimtek how high standard there is in this.:thumbup::thumbup::thumbup::thumbup::thumbup:

I imagine this could be very useful for small plane pilots, that don't have the availability of a real simulator. Because experiencing a emergency (in DCS) is alot better than having just a theoretical knowledge, if it happens in real life.

I know I didn't use that much time to get the wording more correct. But to me it was more important to understand it was logic this happened, not needing to really know what the different zones of speed was called.

And I'm quite impressed with Belsimtek how high standard there is in this.:thumbup::thumbup::thumbup::thumbup::thumbup:

 

I imagine this could be very useful for small plane pilots, that don't have the availability of a real simulator. Because experiencing a emergency (in DCS) is alot better than having just a theoretical knowledge, if it happens in real life.

Ah don't worry about the wording. I had to be in school for 5 years to get it correct! :) If you need to understand something, like the logic, well that's where the theory comes in. No need for the math, but your statements just sorta made no sense :P But that's ok, we all learn everyday.

That being said, where do you think simulator modeling comes from? The theory we learn.