Douglas X-3 Stiletto FSX Native

[Mach3DS]

Rick:

They would be flaps as opposed to slats as they do not open up an airway behind them and apparently are manually controlled separately from the TE Flaps. This allows the test pilot to carefully try out different positions and combinations. Interesting that the ailerons droop with the flap extension. This might have made for roll control at low speeds (relatively) being less agile.

The chart is also quite interesting regarding stall speeds in IAS increasing at higher altitudes. The only thing I can imagine changing significantly at altitude would be Mach Number?

Cheers: T

Yes that's my mistake. I should have looked more observantly at the photos! Rookie mistake from someone who knows better!

 

[Milton Shupe]

Havent been feeling up to par the last couple days but did get a chance to take her up for a bit today. I was totally delighted to see it "misbehaving" almost on cue. She fliy's beautifully between 500 and 650 knots and is a delight. Right around 730 knots @ sea level she gets real interesting. It's like trying to swim through half dried concrete, which is a it should be. Landing was amazing. From the VC its real easy to line up on the runway, but setting it down in one piece without screwing something up is definitely an artform to be developed. Hehehe.. two mile long stopping distance.. I am quite confident that this is going to be one of the masterpieces of flight sim.. Great job Milton and team.. absolutely magnificent.

Thanks Pam. It's only a basic FDE for testing the model and general development. I was hoping to give you a good starting point for FDE development, but mainly just needed my usual base test flight model.

I know you can take it to a level we need for realism.

EDIT: Just FYI, the LE and TE flaps do have individual controls. I hope to use xml to accommodate that, but for now, I have the two flaps sections doing what the pilot would do with separate flap controls. Also added the speed brake now, and it works perfectly well.

 

[warchild]

Thanks Pam. It's only a basic FDE for testing the model and general development. I was hoping to give you a good starting point for FDE development, but mainly just needed my usual base test flight model.

I know you can take it to a level we need for realism.

EDIT: Just FYI, the LE and TE flaps do have individual controls. I hope to use xml to accommodate that, but for now, I have the two flaps sections doing what the pilot would do with separate flap controls. Also added the speed brake now, and it works perfectly well.

Oh excellent.. Thank you Milton..

I'll need to translate the adverse roll into adverse roll + pitch.. It'll need some study and experimentation from me. Since ive never made an fde that specifically follows an exact and well documented performance curve, it'll be a real challenge. It's almost like i have to unlearn how to make a nice enjoyable plane. My old experience flying the cherokee has no relevance here..
heheh I'm really going to enjoy this..

There's another phenomena that happens at transsonic speeds that i want to look at with this model as well.. As you approach the speed of sound, your drag doubles, but once you pass the speed of sound, it drops to half. I'm sure we can program that in with an xml baed config file seperate from aircraft.cfg, but i'm very curious about how it all ties in together, especially since the adverse yaw happens at 1.05 mach, right where the drag starts to drop..

 

[Milton Shupe]

Pam,

The FDE is apparently compensating for or simply ignoring the real dynamics of drag I suspect, or simply compensating with thrust to get to M1.05.

If you add any more drag pre-mach, it will never get there without boosting the thrust.

 

[warchild]

oH no.. I'm sory.. did I make it sound like the fde is doing that?? No.. That happens in real life.. It's very bizaar and may be related to what Tom says is Mach Tuck. More for me to learn ..

https://www.theairlinepilots.com/forum/viewtopic.php?p=691&sid=322be5fb5b9e02d92e2bb65065e8dd3f


Another related phenomena is that as you transit the speed of sound, the shock cone narrows..

 

[fliger747]

Pam:

The mach drag can be directly modeled in the .Air file, Table 430. The major issue with it is that it is in .2 Mach intervals, would be nice if it was a closer spacing.

Cheers: T

 

[warchild]

Pam:

The mach drag can be directly modeled in the .Air file, Table 430. The major issue with it is that it is in .2 Mach intervals, would be nice if it was a closer spacing.

Cheers: T

I.m not so sure microsoft could ever perceive that anyone would delve this deep into flight characteristics. They wouldnt have a reason to think more granularity is needed.. Mach drag doesnt have an effect until 0.75 mach, so the normal airliners see only a limited amount of its effect. concorde sees its full effect, but has enough power it isnt even noticeable to the normal passenger..
I dont normally like messing with tables, because i make so many mistakes, but i guess i need to learn eh??

 

[Milton Shupe]

Looks like table 430 takes care of that and that thrust does in fact overcome it in our little aircraft that can

 

[warchild]

So heres something thats blowing my mind. According to the airlinerpilots page, as you go supersonic, the pressure wave turns rectangular??

https://www.theairlinepilots.com/forum/viewtopic.php?p=691&sid=322be5fb5b9e02d92e2bb65065e8dd3f

 

[warchild]

Looks like table 430 takes care of that and that thrust does in fact overcome it in our little aircraft that can

Excellent.. . I can be my typical little cowardly self and not cause any grief .. I really like that.. ::

Now, if we take that ([ correction ]) drag curve, and add in the below, overlaying it in our minds ( because we dont have a million dollar wind tunnel ) we start to see a complete picture..

On a typical transonic airfoil the transonic rearward shift of the CP occurs at about M 0.75 to M 0.98

On an example wing (Symmetrical at 2 deg alpha with MCrit at M0.75)

At MFS (free stream Mach) of M0.75:

- Mini shockwaves form on upper surface of wing.

- CP 20%

MFS between M0.75 and M0.81:

- As Mach number increases the shock waves join up and move aft.

At MFS of M0.81:

- A single clearly defined shockwave is formed at 70% chord.

- CP moves aft to 30%

- Bottom flow (not so fast at 2 deg alpha) is not yet sonic. Its just below it.

At MFS of M0.89:

- Top shockwave is stuck at 70% chord (high pressure behind it).

- Bottom shockwave is at the trailing edge.

- CP moves forward to 15%

At MFS of M0.98:

- Both shockwaves at trailing edge.

- CP moves back to 45% (in the transition from M0.89 to M0.98 )

At MFS of M1.4:

- Bow shock attaches (MDet)

- Trailing edge shocks become oblique.

- CP 50%

 

[warchild]

And your right zMilton. This is definately the little plane that can. Westinghouse may have screwed up, but douglas created something amazing..

 

[fliger747]

Intereresting test flight. Got up to M 1.02 in level flight at 25,000' (ISA). However in a dive to M 1.25, I found the ailerons completely loose effectiveness above M 1.1. The plane will remain in whatever roll attitude it is in without regard to cockpit input.

Interesting in the .Air file there are more entries for Mach related effects than any other single area. Hmmmm.

The 737 started hitting a mach drag slope after M .74, any faster took a lot of thrust. The 747, especially, was a race car. It was optimized for about M .86 but would cruise happily all day at M .90-.92. At that speed one could crane their neck around in the cockpit and see a shockwave standing up about 10-15 feet inside the winglet. However at those speeds (much higher was possible if not certified) fuel consumption increased significantly.

 

[warchild]

If you continue to accelerate you will find that that loss of aileron control i the onset of reverse control. left aileron will cause the plane to roll to the right, and right aileron will cause the plane to roll to the left. Its a bit primitive, but its exactly in line with this aircrafts adverse yaw behavior..

 

[fliger747]

The usual reason for aileron reversal is wing flexibility. What happens is the aileron starts acting as a booster tab and warps the wing in the opposite direction. It's that reason that large swept wing aircraft usually have the outboard ailerons locked out above a certain speed and roll control is provided by inboard ailerons and spoilers.

However, as you point out, in the high transonic environment the drag induced by one wing developing critical mach over that wing and not the other can cause a change in lift and drag inducing an opposite roll moment. As shockwaves in this environment come and go quickly when on the "edge" I would guess it is sudden onset condition and not preceded by aileron lock over any appreciable speed range. Any info on that?

Interesting airplane! I did successfully land it at KEDW using about 2/3 runway! Haven't crashed it yet...

Cheers: T

 

[Bjoern]

Pam:

The mach drag can be directly modeled in the .Air file, Table 430. The major issue with it is that it is in .2 Mach intervals, would be nice if it was a closer spacing.

Cheers: T

That's what table 154a is for, but it's not usable for RTM/SP1/SP2 users.

So heres something thats blowing my mind. According to the airlinerpilots page, as you go supersonic, the pressure wave turns rectangular??

https://www.theairlinepilots.com/forum/viewtopic.php?p=691&sid=322be5fb5b9e02d92e2bb65065e8dd3f

This only denotes an almost instantaneous pressure increase.

 

[zswobbie1]

Is there anyway we can use some of the configs in FS2004? Or are they unique to FSX

 

[fliger747]

Yes the 154a table (at the very bottom of the F18 .Air file) is probably what the 430 table should have been but given the Freeware market segment we are probably stuck with the 430 table for compatibility. I think I may still have the RTM version on an ancient computer somewhere, running XP.

Both the XF 92A and the X-3, along with many jets of the era suffered from low available thrust. A skating buddy of mine was a WIZZo on the B-47, what interesting stories! Not enough thrust, just add engines! Even the 747 project almost failed due to engines, the first ones needed water injection to meet takeoff performance requirements. A long way from the sky rocket the 400 was.

 

[Milton Shupe]

As mentioned in an earlier post, I had to re-do the gear doors. Available time has limited progress but now have left side doors, hinges, actuating rods, interior bay area, floor, ceiling, ribs, etc. close to done. Just got to tie the upper and lower actuating rods together to a common junction used to rotate the doors.

Then, on to the wheels and tires, torque links, brake lines, .... then clone for the other side.

 

[Bjoern]

Yes the 154a table (at the very bottom of the F18 .Air file) is probably what the 430 table should have been but given the Freeware market segment we are probably stuck with the 430 table for compatibility. I think I may still have the RTM version on an ancient computer somewhere, running XP.

Primarily use table 154a, then put interpolated values into table 430 and a disclaimer in the manual that the thing won't fly quite correctly in RTM/SP1/SP2. FSX will choose the best table automatically. Problem solved.

 

[Milton Shupe]

Slowly making progress to complete the left gear bay, doors, and the many gear parts and animations. A couple of brake line animations to do, then clone for the other side.