Baby Bus - Winging it!

[Dave Swindell]

Well I've eventually got back to the modelling desk after a week away at the parents, going down with the flu and organising a load of stuff for work. I didn't see much of Huddersfield show apart from setting up, taking down and assisting with the competition (rather nice BMI A319 in class 1) however I did manage to catch up with Geoff Eastham on the Airliner SIG display and we had a good chat about life in general and baby buses in particular.

So, this week I've been mostly doing wings. Most of what follows would have been much easier to complete after building the wing, but before attaching it to the fuselage which just gets in the way - you have been warned. Oh, and most of it applies to all baby buses.

First, the nav lights, there's two coloured lights and a strobe behind a clear fairing. To model this I first drilled a couple of 0.5mm holes into the wing where the coloured lamps are positioned. Next the recess where the clear part fits was backed with a strip of aluminium foil, shiny side out, stuck in position with superglue. Don't worry about it being oversize or try to trim it too close. Once firmly stuck poke through the foil with the point of a cocktail stick, then fill the holes with the appropriate colour paint, again don't worry too much if the paint gets outside the hole, this can easily be gently scraped away once dry. The clear covers can then be cut from the sprue and trimmed to fit, then stuck in position with superglue, which is also used to fill any gaps. Once the glue is dry trim off the excess foil with a sharp blade, then file and sand the light flush with the wingtip. It should now look something like this:-

This needs a polish with micromesh to restore full clarity.

Moving inboard a bit to the ailerons, and this excellent plan photo of G-EUNA shows that Revell have got the chord of the aileron wrong on the upper surface, its far too big. The hinge line is shown in line with the leading edge of the spoilers when it should be about mid chord on the spoiler. I took a reference as the kink moulded in the inboard edge of the aileron, and using a set of dividers with one point in the Revell hinge line, scribed a second line parallel to it for the new hinge line. The old hinge line was then filled in.

Moving inboard again, we're looking at the flap track fairings. As well as filling the sink marks on the sides, these should be flush with the top surface of the wing. The A320/A321 kits aren't too bad, but the A319 kit (and hence this conversion) has a bit of a step even after thinning the wing trailing edge. Sections of 15 thou card were glued to the top of the canoe fairing immediately aft of the trailing edge, and then filed and sanded to fill the gap. Before doing this on the outboard fairings, a 15 thou strip 0.75mm wide by 4mm long should be added so that it extends equidistance either side of the fairing, and the edges need trimming so that they're parallel to the canoe fairing. This extension can be seen on the photo of G-EUNA and here which shows the fairings flush with the wing surface.

And moving further inboard, we come to the join between the inboard and outboard flap sections. Below the wing this gap is bridged by a flexible membrane, above the wing there are large rubber seals on each flap section which extend most of the way to the trailing edge, at which point there is a noticable notch. Geoff tackled this by making a large cut along the flap join line, to be filled in with strip and rod to represent the seals, I've gone for a more subtle approach. The join line between the flap sections was heavlily scored with a P cutter, then the top edges of this line were rounded off by scraping with a modelling chisel. Scoring the line deeper gave a V notch on the trailing edge, this was rounded out using the side of a 0.5mm drill as a file to get the right shape and depth. On the underside the scribed join line was filled in. This gives the shape, the actual seals I plan to represent by painting or strips of decal film once the basic paint scheme is on.

The last mod which I've started but haven't finished, came after viewing this image in the Britmodeller A319/A320 walkround (excellent ref pics as usual). Compare it to this image taken from pretty much the same angle, and you will notice a significant difference in the above wing root fairing - there's a distinct bit of "mini area ruling" going on.

The Revell kit represents pretty closely the second configuration without the large curved fairing, but if you look closely at the earlier linked photo of G-EUNA you will see where this curved fairing extends out over the wing root, and also the fairing extends further aft and higher up on the fuselage sides. This is one of those things that isn't immediately obvious until you become "zoned in" on it, and I've been looking at a LOT of baby bus photo's recently. This appears to be a fairly recent addition to later build buses, and not confined to any particular model. It doesn't appear to have been retrofitted to earlier built aircraft, certainly not in the BA fleet as the only 2 that appear to have it are the A318's. It doesn't appear to be structural, so I assume it's something aerodynamic to get a few less GPM (gallons per mile!) To model this it's going to be a bit of good old fashioned sculpting with Miliput, and to get the fairings symetrical I've masked out the outline to use as a guide. I first roughed out the shape in pencil, then stuck 2 strips of masking tape in position over the lines, which were traced through. The tape was removed and stuck to thin plasticard, and the lines cut through the masking tape and card. The card was removed and flipped over onto the sticky side of another strip of masking tape and a mirror outline cut, then the strips were re-attached to the model to give a symetrical outline.

 

Sculpting the fairing is the next task.

The observant among you will have noticed I haven't attached the tip fences yet, they're staying off until much later in the build, cos otherwise they won't be attached for long!

One last point regarding the Revell wing, it's moulded as an A321 wing and I'd already removed the extra small canoe flap track fairings and filled the scribed lines of the split flap sections, however there's a school of thought that says the wing trailing edge should be modified to reduce the wing area as this was bigger on the A321. I firmly believe this to be a myth, which is strongly supported by Airbus who quote the same wing area for all models of baby bus. Yes, the trailing edge of the flaps was modified to produce a split flap which increased the wing area of the A321 in comparison to the A320/A319/A318 wing with the flaps extended - however when retracted the clean wing has exactly the same planform/area as the others.

Edit:- disregard this last paragraph, see below for changes to flaps.

[Caution Wake Turbulence]

Hi Dave,

looking good!

According to this, although the basic wing is the same, the flap area is bigger (even retracted):

http://www.flightglobal.com/pdfarchive/view/1993/1993%20-%200507.html

Cheers,

Andrew

[XV571]

Hi Dave,

Fantastic work on your 'cut and shut' 'bus. It's fascinating to see an alternative approach to creating the smallest member of the Single Aisle family. The extension to the fin is just how Airbus increased the height. Keep going, you're doing a brilliant job.

I'm glad the info on the Wing Tip Fences was useful; yours look spot on. Thanks for highlighting the errors in the measurements - that's what happens when you scribble them on to a scrap of paper with a very dodgy sketch . The shape should have been right - it was traced directly from the actual assembly drawing . I've now had another look at the drawings and re-measured the major dimensions and yours are pretty much bang on the actual dimensions. If I find something that shows the contours and angles of the Fence from end on I'll post the details. I'll also go back and correct the original post so there's no conflict.

Good spot on the upper wing to body fairing. I happened to see your post during lunchtime so having a rare quiet afternoon I had a look into the changes. The new fairing design is indeed intended to improve fuel burn in cruise and was introduced from MSN4007 - which coincidently happens to be G-EUNA! All A318/A319/A320 aircraft built after this will have the bigger fairing but it is not retrofittable to earlier aircraft since there's a fair amount of structural changes under the skin. At it's widest point the fairing appears to be about 200mm wider than the older version. Here's G-EUYF (MSN 4185), the first BAW A320 with the new fairing: http://www.airliners.net/photo/British-Airways/Airbus-A320-232/2457363/L/&sid=6a752840c6e9d8022d4783c47adaa5bf. A320 G-EZUG in the walkaround is MSN4681 with the new fairing whereas A319 G-EZDF is MSN3432 and has the original version. BTW the A321 has a different fairing which doesn't appear to have been modified, although I could only do a quick search. If I find anything I'll add it to the post.

For the ailerons, don't completely fill the line where the original aileron was. What I think Revell have done is mistakenly include the access panels in front of the aileron to match up with the grey painted area:

http://www.airliners.net/photo/Jetstar-Airways/Airbus-A320-232/0844990/L/&sid=5cc7deee98e8fc0512351dc62725c06c

http://www.airliners.net/photo/Iberworld-Airlines/Airbus-A320-214/0827008/L/&sid=5cc7deee98e8fc0512351dc62725c06c

Incidentally, Zvezda's A320 has ailerons with a more representative chordwise dimension.

For those that are interested, you can determine if an A320 (or A319) has CFM56-5A or -5B engines installed by looking at the third digit in the variant designation. As a quick re-cap, the first digit is the series i.e. -100 or -200; the second digit is the engine manufacturer (1 for CFMI, 2 for P&W and 3 for IAE) and the third digit covers the engine sub type and thrust. On the A320, the CFM56-5A designator is 1 or 2. On the A319, the -5A is denoted by 3 or 4. The exact breakdown for the CFM powered aircraft is as follows:

A320-111 (CFM56-5A1), A320-211 (CFM56-5A1), A320-212 (CFM56-5A3),

A319-113 (CFM56-5A4), A319-114 (CFM56-5A5),

A320-214 (CFM56-5B4), A319-215 (CFM56-5B5), A320-216 (CFM56-5B6),

A319-111 (CFM56-5B5 ), A319-112 (CFM56-5B6), A319-115 (CFM56-5B7)

The CFM powered A318s and A321s all have -5B engines.

It is possible for an A319 or A320 to change designation (although very rare) so it's best to check for the timeframe for the aircraft. The change is to go between one of the subtypes but fortunately you can't change from the -5A to a -5B or vice versa. For example, while an A320-211 can be converted to a -212 it can't become a -214; or an A319-115 be changed into a -113.

Hope this helps,

Jonathan

[stringbag]

Some fantastic info and detail being made available as a result of this thread.

Thanks to all concerned.

Chris.

[Dave Swindell]

Well, this weekend I've been mostly looking at and measuring photo's of baby bus wings. Finding good photo's from above with flaps retracted is difficult, finding one from below is impossible (well I did about 20,000 photo's on Anet and didn't find one!) Results of my labours? Well it's humble pie for tea tonight.....

Hi Dave,

looking good!

According to this, although the basic wing is the same, the flap area is bigger (even retracted):

http://www.flightglobal.com/pdfarchive/view/1993/1993%20-%200507.html

Cheers,

Andrew

Thanks for that link Andrew, an interesting article I'd not seen before. The Airbus webpages I'd saved previously (and which no longer exist having been updated) quoted the wing area for all versions as 1320 sqft/ 122.6m2. The above article gives an increas from 124m2 to 128m2 for the A321, 4m2 over the span of the flaps. This gives an increase in chord of the inner flap of approx 246mm, or 1.7mm @1/144, a substantial amount which should be noticable in photographs.

Comparing ratios of measurements taken off the photo's I found, the wing structure forward of the flaps on the upper surface is the same across all marks, but the flap chord is greater on the A321, and taking averages I came out with a scale difference of 1.6mm based on the Revell kit dimensions - ie pretty damn close to the difference calculated from the Flight article. If Jonathan (XV571) has access to the flap dimensions, I estimate the inner flap chord to be 1310mm for the A321, and 1080mm for the others.

To clarify, the Revell kit is correct for the A321, for all other versions:-

Remove the small flap track fairings

Reduce the inner flap chord by 1.6mm

Reduce the outer flap chord by 1.6mm inboard tapering to 0mm at the outboard edge.

Fill any remaining lines of the double slotted flaps

Shorten the aft end of the inboard main flap track fairings by 1.6mm

Shorten the aft end of the centre main flap track fairings by 1.2mm

Shorten the aft end of the outbd main flap track fairings by 0.4mm

Whilst on the flap track fairings, Revell mould them with all sides coming to a point at the aft end, whereas in actual fact they end in a vertical chisel edge. This can be modelled when shortening the fairings. This photo of an A321 wing clearly shows the subtle change of angle of the wing trailing edge just inboard of the aileron, and the shape of the aft edge of the flap track fairings. The A320/A319/A318 wing trailing edge is a straight line from tip to inboard flap.

I'm glad the info on the Wing Tip Fences was useful; yours look spot on. Thanks for highlighting the errors in the measurements - that's what happens when you scribble them on to a scrap of paper with a very dodgy sketch . The shape should have been right - it was traced directly from the actual assembly drawing . I've now had another look at the drawings and re-measured the major dimensions and yours are pretty much bang on the actual dimensions. If I find something that shows the contours and angles of the Fence from end on I'll post the details. I'll also go back and correct the original post so there's no conflict.

No worries Jonathan, having worked (briefly) in a drawing office, I did exactly what you're not supposed to do - scale off the drawing and ignore the (incorrect) dimensions! Came out spot on as you say :-)

Good spot on the upper wing to body fairing. I happened to see your post during lunchtime so having a rare quiet afternoon I had a look into the changes. The new fairing design is indeed intended to improve fuel burn in cruise and was introduced from MSN4007 - which coincidently happens to be G-EUNA! All A318/A319/A320 aircraft built after this will have the bigger fairing but it is not retrofittable to earlier aircraft since there's a fair amount of structural changes under the skin. At it's widest point the fairing appears to be about 200mm wider than the older version. Here's G-EUYF (MSN 4185), the first BAW A320 with the new fairing: http://www.airliners.net/photo/British-Airways/Airbus-A320-232/2457363/L/&sid=6a752840c6e9d8022d4783c47adaa5bf. A320 G-EZUG in the walkaround is MSN4681 with the new fairing whereas A319 G-EZDF is MSN3432 and has the original version. BTW the A321 has a different fairing which doesn't appear to have been modified, although I could only do a quick search. If I find anything I'll add it to the post.

I'd forgotten about the latest BA A320's with G-EUY* reg's, these are the ones that are apparently going to get the sharklets starting next month, must remember the fairing when adding the sharklets to mine! Whilst hunting for the photo's mentioned above I found several A321's with the fairing (or very similar), here's one for starters.

For the ailerons, don't completely fill the line where the original aileron was. What I think Revell have done is mistakenly include the access panels in front of the aileron to match up with the grey painted area:

http://www.airliners.net/photo/Jetstar-Airways/Airbus-A320-232/0844990/L/&sid=5cc7deee98e8fc0512351dc62725c06c

http://www.airliners.net/photo/Iberworld-Airlines/Airbus-A320-214/0827008/L/&sid=5cc7deee98e8fc0512351dc62725c06c

Incidentally, Zvezda's A320 has ailerons with a more representative chordwise dimension.

I'd noted that, but it's easier to fill and re-scribe than partially fill the line . As the photo's show, it needs modifying when I rescribe anyway.

Haven't got the Zvezda kit (got a whole stack of Revell ones though) so can't comment - how's the flaps for size?

Interesting & useful summary on the engines, thanks very much!

Now I've worked out the flap arrangement I've got a load more corrections to do!

[Smallscaler]

Hi Dave,

stunning project, I am watching with great interest, not at least 'cause I am currently doing the same conversion..

Did you already reduced the flap chord and the flaptrack fairings...? I hope you didn't, because I think this is not necessary if you use the A319 kit..

If you'll compare the wings of the A319 and the A320/A321-kits by laying them once upon the other, you'll recognize that Revell already considered the smaller trailing edge on the A319 kit..

To clarify, the Revell kit is correct for the A321, for all other versions:

Reduce the inner flap chord by 1.6mm

Reduce the outer flap chord by 1.6mm inboard tapering to 0mm at the outboard edge.

Shorten the aft end of the inboard main flap track fairings by 1.6mm

Shorten the aft end of the centre main flap track fairings by 1.2mm

Shorten the aft end of the outbd main flap track fairings by 0.4mm

Edited March 23, 2015 by Smallscaler

[Dave Swindell]

Hi Dave,

stunning project, I am watching with great interest, not at least 'cause I am currently doing the same conversion..

Hi Michael, and welcome to Britmodeller, glad you're enjoying reading this, I've just popped over to your site for a quick look, some lovely models there! Also had a quick read of the pictures of your 318 conversion (my German is restricted to deciphering technical manuals, I'll have to run it through google translate)

Did you already reduced the flap chord and the flaptrack fairings...? I hope you didn't, because I think this is not necessary if you use the A319 kit..

If you'll compare the wings of the A319 and the A320/A321-kits by laying them once upon the other, you'll recognize that Revell already considered the smaller trailing edge on the A319 kit..

Yes, I did that this afternoon (photo's & update tomorrow folks!) I'll have to respectfully disagree with you, the A319 wing and the A320/A321 are completely different moulds with different engraved details, but the flap and wing chord on both wings is identical. Measured with my verynear calipers the chord of the inner flap section on both wings pre modification was 5.3mm, post modification the chord on the A318 is now 3.8mm, the same as that on the Zvesda kit that arrived in the post this morning.

[Smallscaler]

Hi Dave,

That's really mysterious...?!

I would swear the parts I have here are shaped as I described (taken from the A319 "BA/Germanwings" / A320 "Thomas Cook" / A321 LH Retro):

The trailing edges on my A319-wing parts are nearly 2mm shorter than on the A320/321 parts, tapering to "0" at the outer edge (where the wingtip is assembled) - exactly as you describe to do the modification..

Is there a modified kit-variant? I don't think so..?!

Well, I'll try to post pictures tomorrow

Edited March 24, 2015 by Smallscaler

[Smallscaler]

Hi Dave

I took two pics this morning...

The first one shows the two different wing molds, taken straight out of the box. The flap chord is indeed ~5mm on both wings but the total wing chord is not identical. It is about ~4,1mm on the A319 and ~4,3mm on the A321 (measured with a ruler).

The trailing edge on the A321 wing is marked red so that it is easier to see on the next one..

And here's what it looks if you put the A319 wing exactly above the other - I think, the now visible red area more or less corresponds to the drawing in the Flight Magazine article..?

So, I further think, if I would cut down the A319 wings flaps on the trailing edge by 1,6mm to '0' (as mentioned), the wing chord will be too short.. (this only works by using the A320/321 wing)

The second option is scribing smaller flaps...the only problem seems to be that if you reduce the flap chord by scribing new lines, there'll be a spacing between the flaps and the air brakes that is not visible on the original. So, in my opinion, to avoid this spacing, we would have to fill in and re-engrave the air brakes completely new, too - a little bit further back..?!

Edited March 24, 2015 by Smallscaler

[Dave Swindell]

Hi Michael

Thanks for the above comparison, I should have of course checked the full wing chord before making any adjustments, and I might have picked up on what we both appear to have missed.

You've examined the wing upper halves and your conclusion is they've modified the wing trailing edge but retained the scribed detail, making the upper surface flaps appear too big and the spoilers too far forward.

May I suggest you examine the wing undersides?

You will find that the trailing edge position, flap geometry, undercarriage cutouts, wheel well doors and rear spar line are identical

If the trailing edge had been modified, it's relationship to the rear spar and undercarriage should have moved, and the flap geometry changed.

The chord of the leading edge slats and their access panels is also the same, so where's the reduction in chord gone?

Yes, they've reduced the chord of the wing torsion box by moving the front spar back and reducing the leading edge wing sweep slightly.

A319 wing (front) clamped back to back with the A320 wing (rear), T/E & wing/fuselage cutouts aligned, note the extra chord on the A320 L/E

As the spar line has moved, the main flap track fairings have aslo been reduced in chord - at the front

The difference in the Revell kits isn't confined to the wings alone.

With the wing leading edge moved back on the 319 wing, Revell have moved the cutout for the wing in the fuselage forward by a corresponding amount, so that the wing leading edge is in the same relative position it is on the A320 fuselage (on the panel line between windows 2&3 forward of the forward overwing escape) This matches photo's of the real aircraft.

OK, time for a confession, there's actually 4 baby buses on the bench, one of each type, which is why progress has slowed a little lately

Now if I compare the modified trailing edge position on the A318 & A319 it comes out on the panel line midway between windows 6&7 aft of the aft overwing exit. Checking on this photo which we've looked at before, with the modified A319:-

this is pretty much spot on for the trailing edge position.

However, on the A320, the modified wing, done exactly the same as the other 2, the trailing edge is further aft, midway along the 7th window.

Checking the L/E and T/E positions on the A321 kit vs aircraft, again the L/E appears to be in the correct position relative to the windows, but the T/E appears to be too far aft. Compare this and this (nice sharklets!) to the kit:-

We can see the L/E in the same position between windows 5&6 aft of the door, but the T/E on the aircraft is between windows 2&3 forward of the door, whereas Revell have it between windows 1&2.

To correct this on both the A320 and the A321, based on my re-examination of the kit wings this morning, the black wedge shaped area needs to be removed, and the whole wing brought forward to put the L/E back in the same position

So the conclusion I'm coming to is the Revell wings are incorrect for ANY version!

A321- leading edge sweep needs reducing/front spare moving back, and the whole wing moving forwards

A320 - leading edge sweep needs reducing/front spare moving back, and the whole wing moving forwards, plus the trailing edge mods detailed above.

A319 - trailing edge mods detailed above.

A318 - mods depending on your base kit, but from the work involved I'd go with modding an A319!

Model photo's edited in this afternoon, as I've wasted all morning researching this instead of completing the flap track fairngs as I'd planned last night!

[Dave Swindell]

Just a quick update tonight, A318 with the wing mods completed

Flap chord reduced as discussed above; flap track fairings shortened (inbd and centre by 1mm, outer by 0.5mm) ends squared up and corners rounded off; aileron hinge panels rescribed lightly; and new aerodynamic wing root fairings added with milliput. These were shaped to the masking tape outlines and smoothed off, then the masking tape lifted (peel back and away from the milliput), and then the milliput gently faired into the wing and fuselage with a wet cotton bud. Hopefully this will leave the milliput requiring a minimum of sanding to finish it off tomorrow.

The wing trailing edge mods have also been finished on the A319 and A320, still pondering on the leading edge mods for the A320 and A321, wondering if the effort involved will show any benefit at all.

[Artmaul]

Did anyone have saved all the pictures involved in this convo? I would like to see all the evidence 😊

[Dave Swindell]

On 09/01/2018 at 9:36 AM, Artmaul said:

Did anyone have saved all the pictures involved in this convo? I would like to see all the evidence 😊

Here you go @Artmaul,all my pictures should be back up for this thread, hope it makes more sense now!

[Skodadriver]

Dave, hope you don't mind me asking but did you finish this?  I'd love to see the result but I can't find it anywhere

[Dave Swindell]

29 minutes ago, Skodadriver said:

Dave, hope you don't mind me asking but did you finish this?  I'd love to see the result but I can't find it anywhere

You're wasting your time looking for finished photos of these, all 4 are sitting on a shelf in my workroom in the same state they are in in the above pictures - well maybe not, there's a distinct layer of dust on them! The only actual progress on this project in 2 years has been the procurement of a set of Braz winglets for one of them. Didn't do any modelling at all last year, though I've done a bit since Christmas (there's a severe risk of a model being finished tomorrow in fact, the first in 18 months.) There's a couple of other unfinished projects on the bench to finish off, then I hope to get at least one finished off. There's a little more detail work to do on the fuselage and U/C, then it's into the paintshop. Once work resumes I'll restart this thread, but don't hold your breath, it will most likely be autumn at the earliest - work and sailing take up most of the summer.

[Skodadriver]

Knowing the standard of your models I'm confident the wait will be well worth it!

[Artmaul]

Dave, thank you so much!