To Infinity and Beyond (DCS F-86 peculiarities - next chapter).

[Art-J]

A short story about F-86 lift/drag/thrust subject, discussed here previously a couple of times.

 

Yesterday I decided to do some sadistic "DCS-hypoxia-effects" experiments by sending my poor virtual alter ego up to ~12000 m without oxygen regulator preset properly ;). After testing all related switches up there, when my pilot started blacking out for good I moved throttle all the way back, expecting the plane to start descending slowly by itself (maybe even fast enough for the fella to revive at lower altitudes).

 

Now, I fully understand that throttle moved back while flying fast will not make the jet engine run at idle RPM and some residual thrust will still keep pushing the plane. Nevertheless, much to my surprise, the Sabre kept on flying happily, making very slow phugoidal oscillations and dropping speed even more slowly (the plane was trimmed before for more or less level flight). As a result, 32 minutes after takeoff, my pilot died :D. At that time the Sabre was cruising at 14200 m with the TAS stabilized at ~820 km/h, pretty fast for a choked throttle if you ask me ;).

 

2 hours 8 minutes later the damn thing crashed at last, after running out of fuel. When the engine quit, the plane was still at 13200 m (!) and doing 670 km/h. I didn't measure the distance it covered, but if we assume an average of about 750 km/h, we'll get into 4-digit range. The flying coffin started its journey in the lower right corner of the map, flew across to MinVody, left northwest of it and proceeded into The Great Northern Blue Outback (as seen on the map, attachment 1)... which, if anyone wonders, is actually The Great Green Nothing (as seen from the plane, attachment 2).

 

While we're at it, is it normal that contrail of a plane with engine off looks like on pic no.3?

 

All and all, I don't have any historic data about maximum lift to drag ratio for F-86 in clean config, but... I'm not sure it was so exceptional that the pilot could cut the throttle and still cover distances in excess of 1000 km :D. I don't think even U-2 could do that ;).

 

It seems the lift and drag of F-86 has been tuned quite a bit in recent few patches, but maybe some further adjustments might be necessary? Any thoughts and comments are welcomed.

[ricktoberfest]

Try this, but turn fuel off instead of throttle at idle. I'm pretty sure it's more about the thrust produced at idle than a drag co-efficient. Does need to be looked at though. IMHO

[iFoxRomeo]

Art-J, there is a "similar" problem with the MiG-21Bis. If you eject, the aircraft continues to fly and fly and fly and reaches altitudes the MiG normally can´t... Once my pilot died and I was only a spectator from there on, and the MiG got the same strange contrails you had on the sabre.

 

So test this with a alive pilot.

Probably the moment you eject or the pilot dies the aircraft switches from PFM to SFM.

 

Fox

[CoBlue]

All and all, I don't have any historic data about maximum lift to drag ratio for F-86 in clean config, but... I'm not sure it was so exceptional that the pilot could cut the throttle and still cover distances in excess of 1000 km :D. I don't think even U-2 could do that ;).

 

It seems the lift and drag of F-86 has been tuned quite a bit in recent few patches, but maybe some further adjustments might be necessary? Any thoughts and comments are welcomed.

Good find! This is not an correct behavior for sure.

[Art-J]

iFox, that is an interesting clue. Will do some testing with the pilot "alive and kicking".

[chaos]

Art-J,

 

Are you sure the thrust lever was at idle? Adjusting the power _after_ blacking out might not actually work... like in real life. ;)

[Art-J]

Yep it was, I moved it while I could still see a little bit of instrument panel :). Besides, the annoying emergency beep was a dead giveaway.

[Art-J]

Did another test flight, not killing my pilot this time and monitoring instruments ;). Looks like moving throttle all the way back when You're at ~14000 m doing ~900 km/h decreases RPM only to 75-77%. So it is indeed enough to keep the plane flying, albeit slower (oscillating between 760 and 790, depending on pitch trim).

 

Sounds plausible, although one might wonder if it's not a way of cheating/exploiting the flight model in order to increase range and endurance of the airplane.

[iFoxRomeo]

...

Sounds plausible, although one might wonder if it's not a way of cheating/exploiting the flight model in order to increase range and endurance of the airplane.

I don´t consider this to be a cheat. Everyone else can climb to that altitude too.

 

Fox

[Art-J]

You're right, I should rephrase - an exploit, which allows us to do things which perhaps weren't quite possible in real plane. On the other hand, with most of off- and online flying taking place waaay lower, I think we can live with that.

[Holbeach]

You're right, I should rephrase - an exploit, which allows us to do things which perhaps weren't quite possible in real plane. On the other hand, with most of off- and online flying taking place waaay lower, I think we can live with that.

 

The max distance a RL clean Sabre on idle can travel from 45,000 ft is 240 nm.

 

This will take 37 minutes.

 

So yes, I think it might be doing something it shouldn't. :music_whistling:

[SgtPappy]

Yes, hopefully they'll look at this soon.

 

I remember another member testing the glide ratio of the aircraft and matching that to the 14:1 mentioned in the manual. So the problem now is probably more to do with the thrust output rather than the drag model.