|In 2020, Plusmodel released two BQM-34A (Q-2C) Firebee kits in 1/72 scale. I decided to do a full review of this new model, to see whether it's an improvement over the 1986-vintage Italeri BQM-34A included in the 1/72 DC-130 kit. I also checked the Black Dog 1/72 resin kit from 2019, but quickly found out that it is horrible. The review is quite extensive, but the hasty reader can go straight to the conclusions.|
The box art of kit 7028 shows a Navy Firebee just after the drop from an Air Force DB-26B, which is a bit silly. This box contains two Firebees plus various pylons. The box art of kit 7035 shows an Air Force Firebee on an Air Logistics 3000 trailer. This kit contains one Firebee plus the trailer in resin. Both box arts have one thing in common: the kit inside does not completely represent the Firebee shown. More on that in the review.
|The runner with all Firebee parts: fuselage halves, wings, tailplanes, spine, inlet lip, ventral fin and engine face and exhaust. It's included in two-fold in kit 7028. All parts are well molded with fine panel lines. However the parts are not Tamiya / Hasegawa quality, it is a sort-of short-run model.|
|The runner with all pylons, as included in kit 7028. The smallest pylons are for the A/B-26 Invader, the next size is for the P2V Neptune, and the two large types are for the DC-130A. See the overview of all DC-130A / E / H pylons on my AQM-34 website. The PlusModel DC-130 pylons have one problem in common with the pylons in the old Italeri DC-130 kit: they are too thin. The real ones are beefy structures, roughly double the thickness of the kit parts. All parts are again well molded with fine panel lines.|
|These are the resin castings for the trailer that is included in kit 7035. All parts are excellently cast from clean and sharp masters, without any air bubbles. The model looks like an Air Logistics Model 3000 transportation trailer, currently called an 'Air Force 3000 series trailer'. For Firebee use, the trailer was fitted with adapter pieces, that are included.|
|The decal sheet as included in either kit, plus the photo-etched parts for the transportation trailer (upper) and tailplane endplates (lower). I don't think I've ever seen these endplates mounted on a target Firebee, but they were common on the later versions of the longer AQM-34 recce Firebee.|
Here's a brief discussion of all versions:
the Firebee family started with the smaller Q-2A (USAF) aka KDA (Navy) aka M-21 (Army)
the second-generation Firebee as discussed here first flew in March 1960, then called Q-2C (USAF and strangely Navy too), 124E (Army), and Model 124 by the factory. It had the Continental J69-T-29 (1700 lbs)
I think that the first batch(es) had no ground-launch capability. In that case there was no JATO rocket attachment bracket under the rear fuselage, no JATO collar attachment brackets on the parachute cone, and no 'slider' brackets under the wing
in 1961 (William Tell exercise), zero-length ground-launch was introduced. Navy followed late 1962
in 1962 the designations were standardized under the 'Tri-Service System' to BQM-34A for USAF and Navy, and MQM-34D for the Army. All missiles got a three-letter designation that is decoded as follows:
B stands for 'multiple launch methods'. M stands for 'mobile launcher'
Q stands for 'pilotless drone'
M stands for 'missile'
in 1973 the General Electric J85-GE-7 (2450 lbs) was installed in a special model for the Army (Model 251) with a blunt 'bottle' nose, called 'MQM-34D Mod II'. It is shown below in the third reference drawing, but otherwise ignored in this review
starting 1983, the J85-GE-7 replaced the J69 in some Navy versions. The Navy started using the designation BQM-34S the eighties. It's not clear to me what exactly makes an 'S', since it was ordered with both the J85-GE-7 and the uprated J69-T-41 (1920 lbs). Also, normally the designation 'BQM-34A' would be followed by 'BQM-34B', so the 'S' is probably short for the feature that makes this version so different
starting 1989, the J85-GE-7 replaced the J69 in the USAF versions. The USAF retained the BQM-34A designation. As far as I can tell, the J85 version of the BQM-34A uses the same nacelle as the original version with the J69 engine
|The first drawing is from Ryan report 12460-27, dated 9 May 1960, courtesy of Gerald Balzer via Mark Nankivil. It shows that WL 20.00 runs from radome tip to parachute cone tip. It also suggests that the wing reference chord also is at WL 20.00. Note that this reference chord is that of the original shorter-chord Q-2A profile - see my analysis of the BQM-34 wing profile if interested.|
|A drawing with more measurements was found in 'T.O.1Q-2C Structural Repair Instructions' from November 1960, courtesy of Jason Hatton. However the dimensioning is often drawn sloppily, especially in the front view. One is left to guess what the dimensions applies to - take the WL 20.00 dimensions between front and side view. Luckily the first drawing contains the answer.
One confusing aspect is that some figures are slightly different compared to the first drawing. One is the fuselage station of the radome tip (0.46"), another is the overall height (0.56"), yet another the tip of the parachute cone (0.25"). Another 'interesting' difference is the vertical tail sweep: 48°1'20" instead of 48°1'2" (0.005° difference). It's not much, but still scary.
The drawing includes a few more airframe details. The skid is drawn all the way up to the front of the nacelle, but it should stop at the canted bulkhead (not drawn in). Other extras are the JATO attachement bracket under the rear fuselage, plus behind it probably a rubber bumper, and the JATO collar attachment brackets on the parachute cone.
Under the main wings, a rectangle is visible on either side. I believe these represent the ground launch 'slider' brackets under the wings, that in reality are much further inboard (FS 81.20 and BL +/-15.00 and WL 17.06). See the next drawing, and this BQM-34 photo.
|The third drawing is from Teledyne Ryan Aeronautical Company report 29369-5 'Catapult performance and interface requirements for launch of BQM-34 vehicles' from 1974, courtesy of Craig Kaston. Despite the high resolution of the original scan, the circled FS / WL / BL station figures are mostly unreadable.
The forward end of the nacelle skid is roughly defined by the 'holdback point' (aka 'keel fitting'), its location is FS 30.00 and WL -2.80. The JATO thrust fitting under the rear fuselage is at FS 144.28 and WL 6.96.
|Craig Kaston also kindly supplied this more recent drawing of the J69 powered BQM-34S (i.e. Navy ?). Interestingly it shows 'new' station numbers, like that of the pitot tube tip, FS 156.00.
If we combine the information from all drawings, FS36.00, FS112.00, FS160.00 and FS 168.50 are frame positions that we can check on the model.
|Lastly, Craig Kaston also kindly supplied this similar-style drawing of the J85 powered BQM-34S (i.e. Navy ?). It shows the set-back air intake (to increase its capture area for the increased air mass flow), and the radome pointing straight ahead, with its tip positioned 3.78" higher.|
|Typically, even this kind of dimensioned drawings cannot be relied upon to be accurate in their outline. I redrew the wing and tailplane shapes based on the on FS and BL data, and this shows many differences.|
|Because the above drawings show few if any panel lines, this drawing from 'Lightning Bugs' is also very usable. Note the offset circular hatches on either side of the nose.
It shows a fintip antenna that wasn't standard on the Firebee - I think it was used by the USAF in the late sixties. A drawing showing 'Ryan Firebee Building Block Capabilities' identifies this fin tip as both AN/DSQ-7 and '800B Doppler'. See for example: F-0891 Teledyne Ryan Firebee UAV AFA 1969 and Convair F-106 on YouTube
A set of BQM-34 photos at Tyndall from 2003
This proposal drawing from the SDASM archive C 3047 shows the dimensions of the electronics bay. But it's not clear whether these are internal dimensions, or external dimensions
I'm not looking for 100% dimensional accuracy, but the kit dimensions are an indication whether the CAD designer / mold maker did his homework, and/or had decent reference material. All three available BQM-34A (Q-2C) Firebee models were analysed.
|Ryan data||SI units||Italeri||Black Dog||PlusModel||Comments|
|source||unit||mm (1/1)||mm (1/72)||mm||diff.||mm||diff.||mm||diff.|
|Fuselage length drawing 1||FS -41.960 to |
|Fuselage length drawing 2||FS -41.5 to |
|Fuselage width||28.12 in||714||9.9||10.7||+4.8%||12.3||+24%||11.4||+15%||Drawing 2 shows 28.10 instead of 28.12. The difference is 0.5 mm in 1/1 scale and therefore ignored.|
|Fuselage height||45.89 in||1166||16.2||17.3||+6.7%||19.2||+18.5%||20.2||+24.5%||Ryan measurement could be excluding the skid and spine cover; model measurements are including these|
Drawing 2 shows 45.90 instead of 45.89. The difference is 0.25 mm in 1/1 scale and therefore ignored.
|Wing span||154.80 in||3932||54.6||56.1||+2.7%||57.7 *||+5.7%||55.9||+2.4%||* summed widths: 2 * cos45 * 31.4 + 13.3|
|Wing chord (perp. LE)||33.40 * cos45||23.62 in||600||8.3||8.9||+6.8%||8.8||+6.0%||8.7||+4.4%|
|Hor. tail span||89.00 in||2261||31.4||31.7||+1.0%||33.9 **||+8.1%||35.0 *||+11.5%||* when mounted at 45 degree sweep|
** summed widths: 2 * cos45 * 17 (av) + 9.9
|Hor. tail chord (perp. LE)||27.00 * cos45||19.09 in||485||6.7||7.0||+4.5%||6.8||+1.5%||6.8||+1.5%|
|Vert. tail LE sweep||48°1'20"||48.02 deg||~47 deg||~45 deg||note that the first drawing shown lists 48'1'2" instead of 48'1'20"|
|Vert. tail TE sweep||90 - 56°22'||33.63 deg||~32 deg||~26 deg|
|Vert. tail tip chord||22.00 in||559||7.8|
|The model was temporarily assembled with dots of CA glue. I had to bend the wings a bit to straigthen them.
The wings mount reasonably accurately at 45 degrees sweep. But the horizontal tails, with their 'natural' position in the fuselage slots, are swept roughly 50 degrees. This should be 45 degrees, and I sanded the roots accordingly. I assembled the model in my AQM-34L jig. This jig was made for the longer AQM-34L, that had the tailplanes further back, but luckily the jig's stops butted against the trailing edges of the tailplanes.
Even with the use of a jig, one needs to fine-tune the zero dihedral angle of the wings and tailplane by eye. The swept surfaces make this quite difficult.
|Compared to the Italeri, the PlusModel Firebee looks fatter, less delicate. The extra fuselage height is obvious. Also, the PlusModel vertical tail is set too vertical - this jumped at me from the first time I saw a photo of this kit.
In the lighting conditions of this photo, you can see that the fuselage + nacelle cross section shows a slight figure 8 shape / double bubble shape all the way down to the exhaust. I never noted that on the real thing, and until I find proof otherwise, I consider this to be a shape error of the PlusModel kit.
|This view also shows the slightly fatter contours of the PlusModel kit. It's mostly in the nacelle area. The radome is also visibly fatter. If my interpretation of Ryan data is correct, Italeri did the best job.|
|In a top view, the narrow (PlusModel) versus wide (Italeri) spine is apparent. I think the Italeri spine width is more correct, but the PlusModel spine has better detail, including the long lanyard running from the front of the spine to the parachute cone. The Italeri model has rather unsubtle mounting holes for the pylon.
A pet peeve of mine: the wing profile on the upper side is unrealistic on the PlusModel kit. The rear 80% of the top side is a straight line! See my analysis of the BQM-34 wing profile if interested.
|The exhaust areas of the two kits are very different, but neither is correct. The photo also shows the biggest error of the Italeri model: the shape of the rear of the nacelle. See here for the correct shape that I built on my AQM-34L.
Another small difference is the execution of the skid on the centerline of the nacelle. The PlusModel skid is shorter but wider. It starts at the canted frame, but that frame(line) is 4 mm too far back, making the skid 4 mm too short. I've seen Firebee photos that shows three parallel skids, so check your references.
Both models portray the weird cobbled-together airfoil shape on the lower side pretty accurately. See my analysis of the BQM-34 wing profile if interested.
|The PlusModel inlet lip is a rough fit, both inside and outside. The separate boundary layer splitter plate is a nice touch. The inlet size difference is obvious, and they basically represent the original J69-powered design (Italeri) and the final J85-powered design (PlusModel). The larger opening was created by cutting back the nacelle, so the inlet is set further aft, probably some 9 inches.
If you look closely, you can see the panel lines that define the radome. On the Italeri model the radome's rear edge touches the air inlet - this is correct for the original design with the small inlet and slightly downturned radome. The PlusModel has the later enlarged intake, and correctly has some distance between the radome panel line and the intake. This should be 10 ½ in = 3.7 mm, the model shows 3.0 mm. But the radome of the later version should be pointed straight ahead, not slightly down as on the model. PlusModel mixed the features of the original J69 and later J85 designs (mostly the latter), but supplies decals for the J69 version only. By the way, the radome parts of the two versions are 100% identical, it's the mounting flange that was changed.
On the PlusModel, the canted frame-line behind the intake is some 4 mm too far back. The circular hatches are ~6 mm too far back.
|Here's the Black Dog model, using the Italeri Firebee as a reference. The longer you look, the more the chubbiness becomes apparent. Combine that with wrong dimensions and plenty of other errors, and you've got a pretty hopeless model.|
quite a few major panel lines are in the wrong places:
on the front fuselage, the canted panel line is ~4 mm to far back
on the rear fuselage, the line behind and above the torsion box of the horizontal tail should be canted towards the rear. This in turn gives more room for the vertical tail to connect to the fuselage
on the vertical tail, the front panel line is parallel to the leading edge, but it shouldn't
compared to the last drawing in the 'reference drawings' section, many of the minor panel lines on the front fuselage are absent. Italeri did the same. One could also say the scale is too small for these details.
the wings look a bit bare with just engraved lines for the aileron and tip cap. I like them better with more details like Italeri, but those are raised
the balance weights of the elevators are missing
the skid is far too wide, and too short on the front side
the recessed attachment point for the trailer on the rear fuselage is missing. Italeri has a 'rubber bumper' there
the attachment points for the JATO collar on the main chute cover are absent. See for example this BQM-34 photo. Location is probably FS 196.7x and WL 18.3x (?)
too much of the root of the vertical tail is cut away where it meets the fuselage. The gap should reduced in length by ~2 mm.
the pitot tube is way too short, and it points too much upwards
all parts need some clean-up, to improve the fit
the inlet construction is a bit difficult, with two small parts. But it does give you a boundary layer diverter plate. The inlet interior is quite rough, and not easy to make smooth
I could not get the spine part to lay down without a gap. In the end I scraped some plastic from the centerline of the fuselage, which helped
the slots for the wings tails align them correctly at 45 degree sweep, but they are a very loose fit. It will be difficult that glue them on horizontally. I recommended to build a jig
the slots for the horizontals tails align them at ~50 degree sweep, but 45 degrees is correct. Again it's a very loose fit
Both kits (7028 and 7035) share the same decal sheet, that has three decal options. It's a pity that PlusModel does not provide their backgrounds. Luckily I was able to find most of the details:
Four almost identical USAF Firebees as used at the Wallace Drone Launch Facility in the Phillipines, part of US Pacific Air Forces, around 1984-1985. Serial numbers of the decals provided are 79-1756, 79-1782, 79-1784 and 79-2460. These four Firebees are visible in a row in USAF photo 'DF-ST-85-11964' and other photos made on the same occasion. Also see this NARA 'Wallace Air Station' photo search. The vertical tails are outlined in white or light gray (decals are silverish). Maybe it is reflective tape to make sea recovery in the dark easier.
The instruction tell you to use 'glossy insignia red' (i.e. FS 11136), however the USAF orders from the time specificy FS 12197 International Orange. And judging from the photos linked above, the Wallace Firebees had a yellow-ish variant of this color, more like FS 12473. Either they were painted as such in this production batch, or the scorching Philipinne sun changed the original color.
Decals for the text 'PAKISAULI SA COMMANDER / PLEASE RETURN TO COMMANDER / WALLACE AIR STATION' are provided, but not included is the text on main parachute cone: 'WARNING / EXPLOSIVE SQUIBS INSTALLED / HANDLE IAW AFR 127-100' in white or black. There are also repetitions of the 'last four' on the airframe, that are not included.
YouTube has two San Diego Air and Space Museum videos showing operations at Wallace Air Station: F 1180 Ryan Aeronautical Firebee Drone Wallace/Phillipines and F 3422 Wallace Air Force Base Ryan BQM-34 Firebee Launches (1968), showing both Air Force and Navy Firebees.
USN Firebee, as on display at the Estrella Warbirds Museum. Originally it was all white with a black radome and fin tip. It was restored with similar markings, but painted orange overall. In 2017 it was repainted white overall with the same markings, closely resembling the way it arrived at the museum. However, Craig Kaston provided photos from 2008 made at Edwards, and there it showed an extremely faded dayglow orange over a white, and several more coats of paint under that. Some original orange remained under service marking stickers that were slowly peeling off. So it probably was dayglow orange at the end of its service life.
I keep seeing 'something' in the radome, it looks like its 'stance' is halfway the downturned one of the original Firebee, and the 'straight forward' one of later versions. However it seems that it originally was a 'downturned' radome. The round badge lacks the text 'MOBILE SEA RANGE' (MSR) and other details. MSR-31 should be a stencil type font. Left side mission markers on the vertical tail should point to the rear.
USN Firebee of the Target Department of the Aerospace Operations Department of the Naval Missile Center, Point Mugu, 1963-1964. It has a checkers tail, sort of a shark-mouth and eyes. A black & white photo is shown in the magazine 'Ryan Reporter' from Spring 1964 (p7, PDF p311), similarly in 'Fireflies and other UAVs' (p80). It survived 34 or 36 missions according to the captions, and the decal shows 36 mission markers. The identity is painted on the nose, but it is very difficult to read due to the small size of the photo - I see something like 2311, 2313, 2315 or 2317. Flickr has an in-flight photo with 36 mission markers, but no visible identity. The box art is a straight copy of this photo. Alamy has an flight line photo but no visible identity.
The instruction tell you to use 'glossy insignia red' (i.e. FS 11136), and although we only have black & white photos to judge things, this color is unlikely. US Navy drone color specs are not 100% clear, but it seems that the Navy used FS 11136 Insignia Red for drones from 1946 to 1959, and FS 28915 Fluorescent Yellow-Orange after that. However FS 12197 International Orange and FS 17925 Insignia White is also specified for drones. Since the Q-2C/BQM-34 is from 1960 and later, FS 11136 Insignia Red is unlikely. That leaves FS 28915 Fluorescent Yellow-Orange and FS 12197 International Orange. The Navy color transition is visible in this undated F-2438 Ryan Firebee Maintenance video, that shows red, orange and white Navy KDA-4s. Note that the freshly delivered ones are orange.
Just maybe it's also shown in Ryan Reporter, May/June 1962 issue (p32, PDF p100). Its identity is 2317, marked as 'KD-7358 / Q-2C59-2317' on the data block. Unlikely: it has 'U.S. NAVY' instead of 'NAVY' titles. "A Ryan Firebee, flown by the Aerospace Operations Department at the Naval Missile Center, Pt. Mugu, was recently the victim of an interesting numbers game. Engine mechanics, checking the Firebee serial numbered "2317", after a recent mission noted that the engine time had been clocked at exactly 23 hours and 17 minutes and that the drone—affectionately called "Bessie" had completed its 17th hop on the Pacific Missile Range. In honor of the occasion, Pt. Mugu civilian employees Ray Hardquist (left) and George Peterson (right) strategically place a decal indicating the 17th flight."
Missing from the decal sheet are 'DRONE' stencils for USAF Firebees and 'TARGET' stencils for Navy Firebees. Also missing are small white dot decals, maybe white stickers to 'seal' inspected hatches. The later are easily made with a little paint on a needle point.
Note that all decal options are for the original J69 version with the downturned radome.
I think the PlusModel kit is a reasonably good model, but it's no improvement over the old Italeri BQM-34, except in having engraved panel lines and availability. If you're not very particular about shapes, the PlusModel kit will do nicely. But I can't 'unsee' the various shape errors of the model
it's a slightly oversized model
the model has nice variety in the decal options. A big contrast with the Black Dog model that contains no decals but costs more
PlusModel could have included many more parts to make this a much more interesting kit; there are plenty of target systems that are mounted on Firebees. More ambitious would be a ground-launch platform
errors that can be fixed quite easily:
extend the inlet forward 2 mm if you're building the original J69 design
tilt the radome 4-5 degrees up if you're building the later J85 design
shorten the span of the horizontal tails 2.3 mm on each side
ensure the horizontal tails are set at 45 degree sweep angle
add 'slider' brackets under the wings if applicable to your airframe
add JATO collar attachment brackets on the parachute cone if applicable to your airframe
replace the pitot tube with a longer one, maybe using Albion microtubing, and point it more downwards. See my AQM-34L where I tried this
move the canted bulkhead panel line on the front fuselage forward by ~4 mm, and extend the skid to that line
errors that are more difficult to fix:
correct the sweep angle(s) of the vertical tail. This will also affect the fit of the tail decals
the double bubble shape of the fuselage-nacelle area can be filled with putty
the area behind the exhaust needs extensive reshaping
|A typical Air Logistics 3000-series transportation trailer consists of a standard trailer with a custom adapter for the specific object to be loaded. The trailer is basically just two rails, two chassis frames, four wheels and a tow bar. For the Firebee, there's a tail support adapter at the rear, and a nacelle adapter at the front. The nacelle adapter is quite special: it can rotate the whole nacelle around the forward blocks. This has to do with the way that a Firebee is assembled from components.
I built the transportation trailer according to the plans. It is shown unpainted here. Strangely, all parts have numbers on their casting blocks, but these numbers are not used in the assembly drawings. That makes build step 5 a bit tricky: which of the four 'coupling blocks' goes where? I concluded it's 7 - 9 - 8 - 6, starting at the top and going clockwise in the drawing. The assembly was a *very* fiddly job, that really testing my patience. Precise alignment is difficult to achieve. The longitudinal position of the 10-piece nacelle adapter is unclear.
I replaced the 0.75 mm plastic axles by 0.75 mm spring steel wire. The real thing does not have axles, each wheel has a bracket that bolts to the chassis frame. It's easy to assemble the chassis frames at an angle to the rails. I recommend using long steel wires as visual alignment tools.
|The nacelle adapter's rear frame is too narrow to fit around the nacelle. Some material can be removed to improve the fit. Interestingly, it does fit well over my own AQM-34K/L/M model, that was based on the Italeri BQM-34A but with a modified nacelle rear end.|
By taking measurements of the built-up trailer, I could see what Air Logistics 3000-series type it tried to represent. My reference was this great Air Logistics Corporation Ground Support Catalog 1980 brochure. From the 3000A through J versies, the combination of rail length and height only left the 3000A, E or G types. The G type drops out because it had steerable rear wheels. The A and E appear to be largely identical, but the E is lighter, possibly due to material differences. My conclusion is that the kit represent either the 3000A or 3000E. We can then compare the measurements of the model and Air Logistics data.
3000A or E
|mm 1/72||mm 1/1||inch 1/1||inch (1/1)|
|Rail length||57.3||4126||162.4"||152.0"||3.7 mm decrease, easy to do|
|Rail spacing||18.2||1310||51.6"||48.0"||1.3 mm decrease, modification not recommended|
|Rail height||17.0||1224||48.2"||40.0"||2.9 mm decrease, would improve looks much|
|Wheel base||30.1||2160||85.0"||92"||2.7 mm increase, recommended|
|Wheel track||22.0||1584||62.4" #||50"||4.4 mm decrease, recommended (# based on my build with steel axles)|
|Tire diameter||8.7||626||24.7"||7.5x10||10 + 2*7.5 = 25", near perfect|
|Now that we know where the kit deviates from the real thing, we can compare the model to photos. The errors noted above are visible when photographs of the real trailer are studied. The rails indeed are positioned too high: the distance between tires and rails is too much. This requires modification of the chassis frames, not an easy job! At the same time the rail spacing could be reduced, but then the Firebee adapter no longer fits on the rails - not recommended. The wheels should be tucked in.
Photograph by Mark Nankivil, April 2003, Tyndall AFB. More photos on my AQM-34 website.
|Visible in this photo is an extra tube in the nacelle adapter, on the centerline at the bottom. The front adapter frame is tilted to match the local nacelle angle.
I don't see the double tubes that PlusModel makes you install on the nacelle adapter. Instead the single tube appears to of a larger diameter.
Photograph by Mark Nankivil, April 2003, Tyndall AFB.
|The problems mentioned above made me remember that the 12 Squared BQM-34E/F short-run injection kit also had an Air Logistics 3000 trailer. The manual states it's a 3000H model, of which the brochure says it's identical to a 3000A except for a different towbar and a 15" aft shift of the rails. The kit also includes a 3500 adapter, also shown in the Air Logistics brochure (p38). But I think a dedicated adapter was used for the supersonic Firebee. A longer towbar is required because of the long nose of this Firebee.
The 12 Squared chassis frames (lower right) match the width of the PlusModel frames, but the height is 2 mm less (10.3 mm versus 8.3 mm). This makes them ideal replacements, solving one of the PlusModel trailer's problems. Maybe the remaining millimeter can be achieved by kinking the axle wires.
BQM-34A Firebee drone 1:72 PlusModel by Peter Szabo on the '72nd Aircraft' forum. Excellent build report
Plusmodel 1/72 Ryan BQM-34A Firebee, US Navy by 'Creepy Pete' on the Britmodeller forum, showing a built model
Fire Bee BQM-34A in 1/72 by Plus Model by HGBarnes on the Kitmaker forum, a straight out of the box build report of two models
In-Box Review 1/72 Firebee BQM-34A MQM-34D on AeroScale. Rather generic review
1/72 Firebee BQM-34A s transportním vozíkem – Plusmodel or the English translation on the Czech Modelweb forum. Another quite generic review, not much to be learned from
1/72 Firebee BQM-34A s transportním vozíkem – Plusmodel – stavba or the English translation on the Czech Modelweb forum. A build report