Release notes for 11.30: Particles, ATC & 4K panel resolution

By: Sam Clark
September 22, 2018

X-Plane version 11.30 is potentially the most anticipated yet. We've been promised a new particle system, as well as numerous art improvements and misc. bug fixes. The X-Plane devs have been hard at work on the aforementioned particle system, of which we got our first look at just a few days ago.

Our first look at the new particle system coming in 11.30.

Sources have provided Threshold with the 11.30 patch notes, which are attached below:

                 - Summary of AP changes in 11.30

                 - Propeller feathering

                 - Anti- and de-ice systems

                 - Oxygen system

                 - Autopilot parameters

                 - Fixed turboprop engine governor

                 - Vacuum systems

                 - Vacuum gyro limitations & caging

Here are the patch notes for the first private beta of 11.30:

Laminar previously confirmed the coming of 4K panels to aircraft in 11.30 in a blog post released yesterday.

Very exciting news for all X-Plane users. Read on to find out more about developer-side improvements coming to 11.30 (Beware: it is almost 2,000 words!)

To see more about the development of X-Plane, see their Facebook page.

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X-Plane 11.30 is a major update that includes bug fixes and a new experimental mode for testing flight model changes.

Flight model improvements

Now we find ground effect for each BIT of the helo rotor! This phases in the ground effect from front to back as we approach a tall helipad!

Wing force improvements:

New drag coefficients in the airfoil files are now much more accurate POST-STALL. This new improvement makes ZERO difference when the wing is not stalled, but post-stall, the drag is now much more accurate.

NOTE: This is NOT a change to X-Plane! It is a change to Airfoil Maker and the airfoil files that we distribute! If you want to realize this new accuracy in your personal or third-party aircraft, then fire up Airfoil Maker and do the batch-update to update all of your airfoils. (BUT BE WARNED: IF THIRD-PARTY ACFT MAKERS HAVE TWEAKED THEIR AFLS TO BE JUST PERFECT FOR THEIR PLANES, THEN THOSE MODS WILL BE OVER-WRITTEN!)

So, for third-party aircraft-makers, do a batch-convert on your airfoils in Airfoil Maker, and then re-test any post-stall flight that you want to. You will see that the drag is initially higher than in previous versions of X-Plane.

As well as the more accurate wing forces post-stall, in Plane Maker we also draw little spheres where the wings connect, so you can see where you have (or don’t) connected wings in Plane Maker.

Propeller and propwash modeling improvements:

Now in Plane Maker, engines screen, you will notice some really cool new stuff. It’s in the engine screen, prop tabs:

Ellipse ratio: Enter a value of 1.0, or approaching 1.0, to get elliptical props for more efficiency… X-Plane will take the Oswalds efficiency to 1.0 as the ellipse ratio goes to 1.0.

Root AOA, tip AOA, and power to interpolate: Now in addition to the helix-angle prop-twist, we add some AOA to the blades to get us to the optimal AOA for the airfoil… with some washout near the tip to reduce induced drag if desired.

And in X-Plane, the propwash is now much nicer:

Rather than just applying wash behind the disc, we now ACCELERATE the air leading up to the disc over a distance, then ACCELERATE it behind the disc over a distance, as happens in reality! This increase in propwash speed over distance is modeled after charts showing inflow of air into the prop disc, watching the air accelerate as it is pulled into the disc, and pressurized to continue speeding up behind the disc! Hit the control-m key a few times while looking at a propeller airplane at full thrust and not moving (or slowly moving) to really see this effect.

Downwash modeling improvements:

I’ve combined data from a number of NACA tech-reports, and confirmed them as follows:

Flight-test on the Boeing 707 in the 60’s showed that the reduced downwash over the tail due to ground-effect threw the nose down about 2.5 degrees if you never flared. With update from NACA tech reports on observed downwash, we now see the same thing on airliners of that configuration in X-Plane! So, the technical reports have been taken into X-Plane, and the results match flight-test on large aircraft where these pitch changes can be most precisely measured.

Engine improvements:

Better jet engine modeling: We now have single-spool and twin-spool jets selectable in Plane-Maker!

We used to have only a single GEARED spool, giving the appearance of a twin-spool jet but not REALLY tracking n1 and n2 separately. Now, you can select single or twin-spool jets in Plane-Maker to really get the jet engine dynamics better in the spool-up and spool-down, watching N2 lead N1 on the spool-up, or the other way around on the spool-down. I have validated this model against careful recordings of engine starts and throttle run-ups and shut-downs taken on a (real) Airbus A-320 to make sure they match perfectly. (I’m working with some Airbus pilots to make an Airbus sim for actual Airbus pilot training, so I’m getting the Airbus engines and flight control systems really dialed in, to satisfy Airbus pilots that want to use X-Plane for training).

As well in Plane Maker you can specify the correlation between N1 and N2, so even though the two can turn freely from each other, aero loads will ultimately drive them to the ratio you specify in Plane Maker (which varies with N1 and N2!) Jet N1/N2 windmilling are now a bit more accurate, based on windmilling data I found in a POH for the Boeing 737.

Nice little improvement in the manifold pressure model for non-turbo airplanes (ones where you entered critical altitude of zero in Plane Maker engine window), where the sim now understands that lower back-pressure at altitude for non-turbo airplanes provides a bit more power per inch of manifold pressure. So, a nice little bit of improvement in the manifold pressure model.

Nice little carb ice improvement: We now look at the actual dynamic pressure and resulting Bernoulli effects in the Venturi tube itself to see when ice will form! So this is a nice way to use physics to predict carb ice.

Free N1 turbo (old)

This is the PT6 turboprop model from X-Plane for many years now, where the N1 is used as the compressor Ng in the real engine. This is a rather old model, and using N1 for Ng is perhaps a bit awkward, when you understand how the real engine works.

Free N2 Turobrop

This is the NEW PT6 turboprop model, where the N2 is used as the compressor Ng in the real engine. This is the new model, which is more accurate and very carefully matched to real PT6 performance. This uses N2 for Ng, which makes a lot of sense, when you understand how the real engine works. As well it uses N1 for the turbine that is attached to the prop, so the N2 drives the torque, and the N1 is spun by that, just like a high-bypass turbofan engine. So, this use of N2 for the Ng makes much more sense, and the model is more accurate as well, so this is the new turboprop model that you should use.

Fixed turboprop

Unchanged for years, roughly modeled after the Garret turboprops. A much better Garret model is indeed coming!

Jet 1 spool

This is the jet engine model from X-Plane for many years now, and is simply not as good as it could be. This model always has the N1 spinning at a ratio to N2 that was a simple power curve. This is good enough to mimic a real jet engine sort of closely, if you don’t look at how fast the various turbines spin up and down compared to each other, and how they differ under load vs windmilling. It was just barely good enough to work, but not as good as I want for X-Plane now.

Jet 2 spool

This is the new jet engine model for X-Plane: The N2 is the power turbine in the hot section, spinning up and down as fuel is applied. Totally INDEPENDENTLY from that, the N1 is spun by the torque generated from N2, spinning the bypass fan. This is more accurate, since N2 can surge while N1 takes some time to respond, and N1 can windmill briskly even if N2 is shut down and barely spinning. So this is a nicer model because each system can spin up or down ahead of the other to really bring those dynamics into the sim!

Body drag and sideforce improvements:

OK this one is NICE! Look at the fuselage and nacelle and misc bodies section in Plane Maker: now there is a RECOMMENDED Cd (coefficient of drag) for that body!

AFTER you have entered the V-speeds for your airplane, AFTER you have entered the geometry for that body, you can see that recommended Cd and use that as your Cd if you like. This Cd looks at the V-speeds of the plane to estimate Reynolds number, which it then uses to estimate skin friction drag, which it then applies across the surface area of the body, which it then multiplies based on the thickness of the body compared to its’ length, which it then compares to the frontal area of the body to predict a reasonable coefficient of drag if the body is streamlined and in un-disturbed airflow. Whew!

So, this is a really nice way to get a good guess at the Cd for an airplane fuselage, and all the other parts on the airplane. Historically, people have not known what Cd to enter for the fuselage and other parts, so this is a really nice way to get a good estimate based on known skin friction drag and wetted area and aspect ratio.

Also, we have refined the side-force on bodies tp be more accurate, and also improved WHERE on the fuselage that side-force is applied! The force application occurs at 25% of the body length at zero sideslip or angle of attack, and moves back to 50% of the body length at 90 degrees offset to the airflow, following a curve in between. So the bodies now have better lift and drag estimates, as well as proper placement of that force at the right point on the body.

Now, various reports I could find do a decent job of estimating WHAT the side-forces are on a streamlined body, but i could find few references clearly showing WHERE those forces act. So how to find out?

I need to find the pivot point of a streamlined body at various angles of attack… how to do that?

Answer: THIS!

And this is very cool: Wings and stuff that are INSIDE of bodies are now automatically hidden from the airflow!

Ditto the parts of wings that are inside of engine nacelles! Cool! This takes away that little bit of lift on twin-engine props, for example, that have the nacelles hiding away part of the wing! This adds a nice little extra bit of realism, especially if you have wings going inside the fuselage or something like that, where the wings do not see any air and therefore need to be removed from any airflow.

You see, the simplified theory says that the lift of the wings goes across the fuselage, but we are now better than that: We now find the lift and drag and location for those forces on the fuselage and nacelles and all other bodies, so the time has come to take the wings OUT of the bodies so lift is not double-computed! So that is the next level of realism, and is done automatically: You don’t have to take any action to hide the bits of the wings that are hidden away inside the fuselage or nacelles: Just hit control-m a few times in the external view when in flight to see how the lift vectors of the wings are gone for all parts of the wings that are hidden away inside a fuselage, nacelle, or misc body.

A few tweaks for gliders:

We now have give tow and get tow and also get winch locations.. so we have all 3 hook locations now. As well winches we have speed commands: faster/slower winch!

DEFINE_CMND_KEY(cmnd_win_faster ,”sim/flight_controls/winch_faster” ,”Winch faster. (for gliders).” ,0,0)

DEFINE_CMND_KEY(cmnd_win_slower ,”sim/flight_controls/winch_slower” ,”Winch slower. (for gliders).” ,0,0)

I cannot imagine ever choosing anything except “FASTER!”, but I admit that some people use the sim differently than me.

Trim and flight control deflection times are now a bit better:

When you enter the deflection time of either flight control or trim in Plane Maker, X-Plane automatically scales that time DOWN for deflection-directions that are smaller in magnitude. So the control or trim SPEED is the same in both directions, even if the deflection is smaller in one direction than another. This holds constant trim speeds and control deflection speeds, regardless of direction and deflection, which is how the mechanical systems typically behave in reality.

Various systems improvements:

Also, for other flight-model improvements, we now have:

Flap lockout if wings are swept. This keeps the flaps from deploying by mistake when the wings are swept, as is done in the real F-14.

Sweep lockout if flaps are down. This keeps the flaps from deploying by mistake when the wings are swept, as is done in the real F-14.

Auto-flaps near the stall, but only partial deployment, as is done in the real F-14.

Auto-speedbrakes with pitch input for precise glideslope control to carrier landings, called “direct-lift-control” as is done in the real F-14.

Fuel tanks can be set as being in any wing, so the fuel load sweeps back and comes inward with increasing wing-sweep, to really get that center of gravity aft, and moment of inertia in roll down, as happens in the real F-14.

We now have 3-dimensional specification of the tail-hook location, which useful for airplane that have tail-hooks, like the F-14.

We now apply the actual arresting-gear hook location to the arresting wires on the carriers to see if we have made arresting-gear contact.

We used to just check the airplane-center location for arresting-wire contact, but this oversight has now been corrected and we check for the actual hook location.