Roll Rate Flight testing posts ONLY please:

[cauldron]

Graph credits belong to J.M. Langeron AKA Topolo.

 

 

Ok, so some layout of the testing:

 

The graph below to be used as a baseline reference point so we can can a place to make comparisons - its not meant to be right or wrong, but its our best guess as to a good approximation of what should be:

 

Roll Rate is degrees per second. The AoA should be held as constant aft stick pressure holding the AoA as best you can as you induce max roll commands. Give reference to your aircraft starting conditions, and FBW status and if its in NTTR or Caucus maps.

 

Also to note, important on the roll rate tests is "dynamic pressure". BY definition Dynamic pressure represents the kinetic energy of the free airstream and is a factor relating to the capability for producing changes in static pressure on a surface.

 

Q=1/2pV(2) Q=dynamic pressure, p=density, V= velocity, V(2)= Velocity squared.

This dynamic pressure holds true for subsonic to hypersonic speeds.

 

According to the graph:

 

A Q=200 yields the lowest results and Q=800 yields the best results, and higher yields similar results. So i suggest we test the high end (best roll rate regime) by holding no lower than Q=800 and letting any errors in flying increase the Q as higher Q does not degrade much the roll rate.

 

So how to we test this? How do we go in DCS and test roll rate at dynamic pressure gradients? Dynamic pressure is dependent of altitude and the square of velocity, - for example from sea level to 40k feet you need to double the TAS to have the same Dynamic pressure.

 

Here is how we can do it, and come back here to share the results.

 

Qbar or Q is measured usually in psf [pounds per square foot]. According to aerodynamics for naval aviators NAVWEPS 00-80T-80 we can get the following to work for us:

 

to use Knots for speed we need a constant of .00339 which yields:

 

Q=((density ratio)(velocity[kts] squared))/295 or... for a known value of Q which we have we can find the velocity we need to validate the gragh:

 

V= "squareroot"of/((295xQ)/densityratio)

 

density ratios: 10k feet .7385, 20k ft .5328, 30k ft .3741, 40k ft .2462

 

Qbar of 800 can be the following in a std atmosphere:

sea level and 485knots

10,000ft and 565knots

20k ft and 665kts

30k ft and 794kts

40k ft and 979kts

 

 

for the "slow roll" end of the tests i suggest the 200 Qbar line:

sea level and 242kts

10k ft and 282kts

20k ft and 332kts

30k ft and 397kts

40k ft and 489kts

 

So all we need to do is go fly and compare our results here:

 

I'll set up another thread tomorrow for the MIL power and AB power level flight envelopes.

 

cheers!

Edited January 16, 2016 by cauldron

[cauldron]

First Data set.

 

Ok, after some long testing - mostly on how to get viable data in game.

 

of note: the QBar speeds mentioned in the OP are in TAS, in case i missed mentioning it. It was a pleasure to note how the IAS speeds remained fairly consistent something that *should* be happening, and more importantly the AoA for each of these speeds at different altitudes for a given QBAr were almost identical - meaning the atmosphere model isn't doing anything weird between sea level and 40k feet - as well as validating my numerical analysis in the OP regarding Q gradients. YES:D

 

ok so the results were interesting, i could not come up with a conclusion as to why the roll rate improved noticeably as altitude increased even though the plane was at the same QBAr. My best guess currently is that it has something to due with MACH.

 

As a general/combined result the [ fyi. current Jan22,2016 update to 1.5 was in the testing ] i found the current build to be about 26% below the reference value of 190 degrees per second, averaging 151 degrees per second, which is noticeable to casual observation.

 

included are my results, if needed i can provide the track files, and raw data for the graphs.

 

Test parameters:

clean aircraft-50% fuel set on unlimited. no more than 3 rolls were "continuous". lastest 1.5 build Jan22-23, 2016, not tested on NTTR2.0, FBW was set to normal & A2A mode.

 

I will follow up with a >Q800 plot and a high AoA plot to finish this segment off, and get on to the other flight tests. Would be great to get independent validation of these results.:helpsmilie:

Edited January 24, 2016 by cauldron
typos

[cauldron]

Possible FBW issue

 

I discovered during my tests that the FBW commands under pilot commands to hold full roll, and with no sideslip commanded- that near the end of the third complete roll at higher altitudes( 30k and especially 40k) the plane violently starts a sideslip and enters a MAX AoA condition in a sideslip.

 

That's only about 5 to 6 seconds into a sustained max roll it departs controlled flight. I wonder if there is an issue with the FBW control inputs failing to maintain coordinated flight while commanded to max roll by the pilot. If anyone can reproduce these results please share them.

Edited January 24, 2016 by cauldron

[gospadin]

I'll retest in the next day or so. Before the update, with just roll input, the plane would definitely depart controlled flight within a few rolls. At high speed, this resulted in the wings tearing off.

[cauldron]

For anyone following, I'm sorry i have not been able to keep up my tests faster. RL :cry:

 

I'll get back to it as fast as i can.