After a long break from the project, I have to take a few steps back before I can continue to work on the project, firstly because I forgot how the software (blender) works and also because of that, I decided to upgrade to a newer version of Blender (2.82), learn how to work with this and convert the old model to the new software.
After two days of trying, watching youtube tutorials and revisting nearly every part, restoring textures and particle locations, I am back to where I had left some 6 months ago.
I also managed to add the final touch to the cockpit shape, now it finally looks like a Caravelle!
With the new version of Blender, the Texture paint option on the 3d model finally works, which makes texturing much easier. Basically I can now generate a texture in blender, draw markings on the 3d model, save the texture and then use the markings to finish the texture in Photoshop. I’ve made a new exterior texture this way.
The first new additions to the project are the exterior doors, including animations and transparent cockpit windows.
The landing gear was modelled and animated, so I thought just texture it and mirror to the other side right?
Well that process took me about three days.
Unlike the 737, which has a pretty simple landing gear, namely one oleo strut, one retract scissor and a single axle with two wheels.
The Caravelle has a complex construction with 20 moving parts: according to the AFM:
A gear leg support, connected to a drag linkage and a tri-hedral linkage assembly. wheel support arms, a balancing arms, pivoting at the centre of the gear leg, connected to the main shock strut and at the rear to the auxiliary shock strut and a compensating rod. two dual wheels arranged in a tandem.
To make things really interesting, the gear retracts over the hinge axis tube, which is angled over the X,Y and Z axis. Blender does support rotation over all axis, however because the gear retract animation is based on a few keyframes, it is essential to make the rotation over 1 of three axis. In other words I had to insert an armature (previously known as bone) to make the animation.
To duplicate the gear I had to perform these steps for all 20 moving parts of the gear structure:
- Select an part
- add mirror modifier, reference to zero
- Apply transformation
- Edit mode, isolate only poligons on the right side
- press P to separate selection
- Object mode, select new part and set new name
- Set parent to mother object on the right side
- Apply all transformations
- Set 3d cursor to hinge point
- Set part origin to 3d cursor
After duplicating the parts with their animation I had to animate the gear retraction. Luckily I was able to copy the bone for the main strut, calculate the angle of change per keyframe and calculate new keyframes.
For the retraction cylinder and piston I just re-animated the motion for both sides.
But! Result! I have now two fully textured, animated, retracting main landing gears
I still have to add the gear bay doors, but I’ll save that for after I’ve done the wings. (the current wing object is just a placeholder)
The attitude indicator with flight directors and the airspeed indicator were one of the first parts that I made for the Caravelle, it was at an early stage in the learning process, so I decided to pick it up and re-do.
First I moved the attitude indicator to a new layer and reserved a larger texture area for the instrument. basically 1/6th of a 2048×2048 texture, more or less. based on photos from the Transavia Caravelle in the Dutch aviation museum and from illustrations in the AFM I managed to make a fairly accurate textures.
The flight director bars didn’t work properly, this is because the FD datarefs are supposed to be parented to an attitude indicator, however if you look at the default aircaft in x-plane, it’s not done.
For example, when you turn on the flight director in heading mode, and you select a heading to the left, the flight director bar moves to the left. you can roll in to follow the bar, but the bar will never centre. This is obviously not how it should work.
To counter this error, (i’ve sent bug reports to Xplane in the past but to no avail) I decided to make a mechanical bank angle corrector in my 3d model. it turns the roll needle in correspondence with the actual bank angle. which means, if the flight director is commanding a 30 degree left bank, and you roll the airplane to 30 degree left bank, the FD roll bar will centre, indicating that you have the correct attitude. so now if you keep the bars centred, you will do exactly what the autopilot would do if it were engaged.
A youtube video from finland showed the first ever autoland of an airliner, (a caravelle 10b3) which showed also how the flight directors behave. sadly it has been removed by the author, but I kept a few screenshots.
The airspeed indicator has a more detailed, but still blurry picture in the AFM, but I was able to make out the brand name, KOLLSMAN 1701 series K-3 D-9 unit.
With that, a good google search and a very detailed disctription of operation in the AFM I was able to correctly draw the textures, animate the needle, drum and barber pole.
The red indicator is set to M.76 on the tiny mach scale to indicate that the mach pointer will indicate that when it comes ‘alive’. On the ground it is set to VMO 302 knots, above the change over altitude it will indicate MMO. (.76). The local speed of sound is purely based on temperature, however just like the real gauge, there is no temperature input to the gauge. only altitude, so it has a realistic instrument error at non-ISA temperatures.
One of the most challenging parts of this project, despite that I have access to the AFM, which contains detail technical drawings and measurements, is that everything is hand-drawn, scanned and not really to scale.
I have taken the side view with all the stations, straitened it out as much as possible in Photoshop, added a ruler, and set it to scale on a flat square in blender. This way I can set all my objects to either a ruler, or a station line to achieve the most accurate model possible.
There are a numbers that are given, they can be added in plane maker and that’s it. For example. Take-off thrust delivered by the Rolls Royce Avon in ISA, Sea level and at 8100 RPM is 11700 Lbs.
It is a single spool engine so N1 = N2 and the N2 bypass ratio is zero.
There are numbers such as wing span, chord, angle of incidence of wings, etc cetera.
To find the realistic performance I have to find wherethe nubmers are not given so I can tweak, and performance tables to have a set target to aim for.
For cruise performance I am focussing my efford at teh Jets2 page in plane maker engines setting.
The power curve for thrust setting with N1 is not given by the manual, shifting the curve will allow me to set the thrust given at a certain power setting.
My initial setup is: FL360 (max). at 45 tonnes (max for that level). should give an IAS of 207 and a fuel flow of 2260 on 2 engines.
It also allows me to find the right amount of fuel consumption per lb-thrust. There is no need to be super accurate here, it’s quite common to have a few percent higher fuel flow than the factory advertisement.
Take-off performance is a different story. The thrust is given, the drag is the only variable. Wheel drag is the most significant at low speeds, Aerodynamic (parasite) drag on higher speeds. The time to 90 seconds is given in the performance tables. (23 seconds at MTOW).
Another variable which is technically given, is the compressor inlet area, however tweaking this number as a large impact on acceleration of the aircraft (accelerate in high or low gear, with the same amount of power).
It turns out, the best performance I get with a very extreme curve, 9.99 to 1.00. It makes sense though for a zero bypass turbojet. below 40% there is basically no thrust available.
With the body coeff of drag value I was able to tune the parasite drag to give reasonable descent performance. I am happy with the results, I can now fly the plane by the numbers (withing 5% accuracy or so).
With a walkaround video from last year, a few pictures and technical drawings, the nose wheel came to life. One day to model and texture, two days to animate!. Mostly because I didn’t know how to animate with armatures (bones) and link those to xplane datarefs and now I do!
Procedure to mirror complex parts with animations that cover multiple axis (xyz).
Animate with armature, not directly in the object. Parent the movable part to the bone. Animate in Pose mode. (Note, dataref won’t turn yellow or green, this is a known bug) Important, add data-ref in bone properties, not object properties. Set (in pose mode) transform to axis angle. set X Y OR Z to 1.00, the others to 0.00 and lock X Y Z rotation axis.
Parent all parts (in tree with branches) to one stationary (non-animated) part. Select that parent part and apply all transformations.
If a part was already paired, ensure all animations are cleared, apply all transformations, un-pair, alt-P and clear all transformations)
Select the entire tree and duplicate (select hierarchy, Shift-D, enter)
Mirror: X Global, then apply all transformation to all parts. Then go to Edit mode, select all poligons and recalculate normals.
It may be nessesary to change the + or – sign in bone animatiotions to get the correct movement.