Belcher Bits BK8 North American BT-9 Page 1/6 July 2014

Belcher Bits BK8: North American BT-9

North American BT-9s in USAAC markings, Randolph Field, Texas circa 1940. Photo SDASM archive.

IntroductionNorth American’s NA-16 trainer was

the sire of a long line of military trainers,theAT-6 Texan being the most famous. How-ever, there were many other variations onthe same airframe. The prototype NA-16was rebuilt into the NA-18 and sold to Ar-gentina. The first production variant was theNA-19, bought for the USAAC as the BT-9. These aircraft used the R-975 engine withits distinctive forward exhaust collector ring,had fabric covered fuselages and all em-ployed the early wing with its straight trail-

ing edge and rounded wingtips. Several at-tempts were made to improve the nasty stallcharacteristics of these early variants…thefinal answer implemented on the AT-6 wasnew outer wing panels with a slight forwardsweep to the trailing edge, a 6" longer fuse-lage and a different shaped rudder.

The BT-9 was actually delivered infour batches. The very first production vari-ant of the North American trainers was theNA-19, 42 of which were ordered for theUSAAC as the BT-9. This was a flighttrainer with no armament provision, and can

be recognized by the curved bottom edgeof the fixed rear canopy. Another 40 NA-19As were also ordered for the OrganizedReserve as the BT-9A. These aircraft hadthe movable rear canopy (wth the straightbottom edge) and could mount a flexible gunthere. There were some other detail differ-ences inside the cockpits as well.

In late 1936, 117 NA-23s were or-dered as BT-9B. This aircraft was virtuallyidentical to the BT-9. At the same time, 67NA-29s were ordered as the BT-9C, thesebeing essentially a repeat of the BT-9A.

Resin Parts Guide

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Figure A Figure B

Figure C

In summary, the BT-9 and BT-9Bwere strictly flight trainers with fixed rearcanopy. The BT-9A and BT-9C were moreoperational trainers and could mount a flex-ible gun in the rear cockpit.

The KitThis kit includes a complete

Occidental Harvard Mk II kit, necessary

resin parts to convert the kit to a BT-9 or9B, a set of EZ Mask canopy masks and aset of decals with schemes for a couple BT-9s as well as a French NA-57 (outwardlyidentical to the BT-9).

FuselageThe BT-9s (and other early NA train-

ers) had what is known as a short-arm rear

Figure D

fuselage, which was 6” shorter than the laterT-6. The difference in length is all at the af-ter end. The elevators are actually in thesame location relative to the wing, but thelater long-arm fuselages moved the verticalfin back 6 inches. Furthermore, these earlymachines all had the fabric sided fuselages.Just for interest’s sake there were a couplelater variants which had a metal coveredshort fuselage, but all long fuselages weremetal covered.Assemble the kit interior, us-ing Figs A and B. Interior colour is interiorgreen with aluminum lacquer rollover struc-ture. Seats would have been bare metal; thepilots used seat pack parachutes. Paint theinstrument panels and side consoles black;the instruments can be picked out with awhite pencil, or by careful drybrushing.

Glue the resin fuselage halves (PartsA) together with the upper cowling piece(part 15) and forward instrument panel (part12) using Fig. C. Kit part 10 will need a lit-tle trimming to allow the fuselage halves tomate properly. When you glue on part 15 sothe panel lines up , there will be a small gapat the leading edge of the canopy rail. Fillthis gap with small scraps of plastic becausethe canopy will not fit if you glue part 15

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further back. I would also recommend leav-ing off the tailwheel until the end.

The resin fabric fuselages are com-mon for both these BT-9s, and Harvard MkIs so for the BT-9, the nose will need to bemodifed. Using Fig. D, cut off the forwardfuselage where indicated. Glue on the ac-cessory section (resin part B); the protru-sions on the back of this part should key inwith the lower section of the fuselage. Fillseams in the upper cowling area.

The resin fuselage will require somesubstantial grinding or filing on the bottomto fit well with the resin centre section. Bestto do this at this stage so you can test fit thecentre section easily.

Glue the carburetor air intake (resinpart C) on the top front of the accessory sec-tion. See Figure E.

CowlingThe cowling is supplied in two pieces

(the forward cowling as part E and the rear

cowling and engine face as part D1 or D2.The first BT-9s had four (what I assumewere) cowling vents on the sides of the rearsection. I have seen photos of these withwhat appear to be flared tubes sticking outslightly, and others where only the cowlingbulges were visible. Later BT-9s do not showthese bulges, although one photograph isclose enough to see that the bulge cutoutswere apparently covered with plain sheetmetal. Abit of a mystery here, and I provideboth a vented and non-vented part. I wouldsuggest painting the engine before assem-bly. The interior of the cowling was alsoprobably natural metal, but could have beenzinc chromate primer. Remove the mould-ing ring from the front cowling, open up thesmall hole in the right side, sand the cowl-ing lip to a smooth radius and glue to therear part, lining up the keyed slot at the top.Fill the seam between the two. This wholeassembly can be painted and attached laterif you prefer ... the cowling assembly has asmall hole on its back face which registerswith a small protrusion on the accessory sec-

tion to ensure the cowling only fits one way.

WingI recommend doing the wing sepa-

rately from the fuselage since it involves glu-ing the outer wing panels on a new centresection, it will be easier to ensure the samedihedral on both wings. Glue the outer wingpanels (resin part G) to the replacement cen-tre section (resin part F). Note that the resinpart incorporates the complete fairing strip,so the outer wing parts are centred on thebutt edge . All three parts are moulded withthe flaps raised; if you want to drop flaps,you are in for a world of work and on yourown.

A word on BT-9 wings. The firstbatches had a nasty tip stall. One early fixwas to fit slats on the outer wing leadingedges. This helped, but the problem stillexisted. Later, the wings were de-skinned,the structure twisted down 2 degrees at thetip and new wing skins installed. Unfortu-nately, this twist is impossible to identifyfrom photographs, so if you see a photo of aBT-9 without slats, it is either very early(pre-slat) or later with the twisted wing(post-slat). If you want to model one with-out slats, file off the protruberances on theleading edges of the wings and sand the areasmooth. If you want to depict an aircraft withthe slats, sand the resin slats flat on the bot-tom, and glue them in place on theseprotuberances. The slat should extend justslightly beyond the leading edge of the wing.

When dry, fit the completed wing tothe fuselage. Some filling will be requiredat the joint between the wing and the resinaccessory section, as well as a bit along theroot.

Tail AreaI recommended doing the wings first,

so that when you come to glue on the tailparts, it will be easy to line everything ei-ther in line or at right angles. The corrugatedskin vertical fin (resin part H) is glued inplace , lining up the after edge with the endof the fuselage. File that surface flat and testfit the rudder, but do not glue that in place

Figure F

Figure E

yet. It is probably better to paint the rudderseparately and glue it on later.

The port and starboard resin tailplanes(resin part J) can be glued in place and seamsfilled. Remember these should be parallelto the wing centre section.

Landing GearCheck your references … early BT-

9s were seen with full spats, while later on,the lower section was removed. Usually, thespats were the same colour as the fuselage,so it may make sense to paint these itemsseparately and glue in place when the modelis completed; note the open sections faceoutboard.

If you are opting for full spats, cut offthe spats (resin parts L) from their base andpaint. The Occidental kit provides threetires, one with a diamond tread pattern. Tossit in the spare box, and sand the line treadpatterns off the other two tires … if you canreduce their width slightly, they will lookbetter. Reduce the thickness of the wheels(part 35) by sanding the back face. Thewheels and their covers (part 36) can beglued together and painted separately fromthe tire. The inner face of the tire should benatural metal. The final step is to glue thetire into the spat.

For those a/c with lower section of thespats removed, abbreviated fairings are alsoprovided. Cut off resin parts M from theirbase; again, you may wish to paint theseseparately and glue on later. Modify the kitlanding gear as shown in Fig.G. These short-ened gear legs (painted natural metal) fit intothe holes in the fairings. The wheels and tiresare finished as above, and fit on the kit ax-les.

Figure G

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The tail wheel from the kit (part 11)is used but with modification. Cut off themounting pins and the rear section aft of thetailwheel strut. Sand the top flat and glue inposition where indicated on the dawing.Canopy

Depending on the way you like to dealwith canopies, you may want to fit the fixedportions such as the windscreen (part 49)and the rear canopy section (part 53a) priorto painting. The Occidental kit includes op-tional canopy sections for early and laterHarvards; be sure to use the early ones withthe additional canopy frames; kit parts 50a(front), 51a (middle) and 52a (rear).

This kit includes a set of EZ Maskcanopy masks for your convenience. Thisself-adhesive film is pre-cut to fit theOccidental kit canopy, and will definitelysave you time in masking. Mix a smallamount of detergent with water, use a sharpknife to lift the canopy mask section off thebacking and a pair of tweezers to dip it in

the soapy water. Place it where indicated onthe canopy; the soapy water will allow youto move it into position. Once the mask isproperly positioned, press it in place and patit dry. Once all the masks are positioned anddried, the canopy is ready for painting.

Final StepsFollowing painting, clear wing land-

ing light covers part 48 (starboard) and 48a(port) are glued in place on the port and star-board wings respectively. The Occidental kitdoes not make any attempt to show thelamps; these could be made from small bitsof sprue or railroad lamp lenses.

On the starboard side just aft of theaccessory section are two small venturi. Toosmall for resin parts, you should make theseup from stretched sprue ends.

BT-9s used a tall antenna mast fittedon the forward cowling area, just to the portside of the centreline. Fit resin part N afterall other work is completed to avoid break-

ing during handling.Glue the pitch control weights (parts

24A) to the kit prop (part 24) hub. The propis natural metal with black on the rear facesof the blades.

References:1. North American Aircraft 1934-1998Vol. 1, by Norm Avery, published byNarkeiwicz / Thompson2. North American NA-16/AT-6/SNJ,Warbird Tech Series Volume 11, by DanHagedorn, published by Specialty Press3. T-6 Texan in Action, by Larry Davis,Squadron/Signal Publications.4. Harvard! by Dave Fletcher and DougMacphail, published by DCF Flying Books.5. The Incredible T-6 Pilot Maker by W.Ohlrich and J. Ethell, published by SpecialtyPress, 1983.6. NorthAmerican’s T-6 by Dan Hagedorn,published by Specialty Pres, 2009

BT-9B, Randolph Field, Texas ca.1937.Common to USAAC aircraft of this period,fuselage was USAAC Light Blue (similar toTrue Blue FS 15102), with Yellow (similarto Orange Yellow FS 13538) wings, fin, andelevators. The anti-glare panel forward ofthe windscreen was black as were walkwayson wings.. Rudder was Insignia Blueleading edge and 13 red and white stripes.The aircraft number was carried in yellowon the blue fuselage , and in black on thewing leading edges centred between thelanding light and the fairing strip coveringthe outboard wing joint.Fire extinguisher panel was red with blacklettering.Ref: T-6 Warbird Tech, p.21

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Decal Sheet Guide

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NA-57, French Navy 1940One of 214 aircraft delivered to Francebetween 1939 and 1940, most serving withthe Armee de l’Air; the first 30 weredelivered to the Navy. These were essentiallyidentical to BT-9Bs with a few instrument-related changes. Overall painted aluminumwith a blue-white-red striped rudder.Ref: Warbird Tech T-6, p.16

BT-9, 46th School Squadron, RandolphField, Texas ca.1941. Identical markings tothose of 231. This machine has the landinggear with removed spats.Ref: Warbird Tech T-6, p.16

NA-31, Royal Swedish Air Force 1937One NA-31 was sold to Sweden withlicensing arrangements, and 136 wereeventaully built in 3 batches. Again,essentially identical to the BT-9B.There is an example in the Swedish AirForce Museum which has been built from aWirraway fuselage with the engine from aYale. As such, it is probably the only fabricfuselage North American trainer remainingin the world. The USAF museum shouldhave tried to do the same instead of tryingto pass off an ex-RCAF Yale as a BT-9!Although we do not provide the markingsfor this aircraft, they are not too difficult tosource. Dark Grey fuselage with orange-yellow wings and tailplanes.Ref: Warbird Tech T-6, p.16