X-15A-2 Accuracy Review

Special Hobby, 1/32 scale

by Daniel W. Rees

HyperScale is proudly supported by Meteor Productions
 

You may also follow this link to see Kent Eckhart's FirstLook review of Special Hobby's 1/32 scale X-15A-2 elsewhere on HyperScale.

Special Hobby 1/32 Scale North American X-15A-2 Kit Accuracy Review:

The good news is that the kit looks like an X-15A-2!

Most of the major elements of the kit are accurate according to my personal measurements and confirmed in the three references listed below. Later I’ll list some corrections to enhance what is actually a good kit, but even if you decide not to make any of these corrections you’ll still have a pretty good model worthy of your showcase.

The history of the X-15A-2 and specific fit of the Special Hobby 1/32 kit will be and has been covered elsewhere, so this analysis will concentrate on the technical accuracy of this kit. The Special Hobby X-15A-2 kit was released at the 2007 IPMS National Convention in Anaheim in August 2007. Dave Klaus at Meteor Productions lent me his kit so I could review it for accuracy.

I had the opportunity to measure the only existing X-15A-2 at the Air Force Museum in Dayton, Ohio. I was lucky enough to be able to spend nearly two full days on this project at the museum.

The museum policy is that the aircraft shall not be touched as it hastens the corrosion and damage to the aircraft due to oils left behind from human hands. Instead, I dropped plumb bob lines to do the measurements. I located the critical points of the aircraft, dropped a plumb line from that point, and marked the locations on the floor. I was then able to measure the distances between those marks to come up with my measurements.

Three specific books were also critical to confirming the kit’s accuracy. They are the Aerofax Datagraph 2, North American X-15/X-15A-2, by Ben Guenther, Jay Miller, and Tony Panopalis; X-15 Photo Scrapbook, compiled by Tony R. Landis and Dennis R. Jenkins; and Hypersonic: The Story of the North American X-15, Dennis R. Jenkins and Tony R. Landis.

I have never met any of these authors but I commend them all for their efforts on researching and publishing on such an important research aircraft. These books should be in your library if you’re interested in the X-15. I would also like to thank the staff of the National Museum of the United States Air Force for allowing me access to measure the aircraft.

As you would guess, I took these measurements some time ago in preparation for scratch-building a 1/32 model myself. And, of course soon after Special Hobby announced their 1/32 kit was coming, so my scratch-building project went on the shelf in anticipation of the injection molded kit.

Now on to the review!
 

Corrections Required for the X-15A-2

• Fuselage length

• Nose “Q-Ball” holes

• RCS nozzles on the nose & wings

• Nose bay location

• Nose gear door

• Cockpit/ejection seat

• Skylight compartment just behind the cockpit

• Optical port

• Wings-to-fuselage location

• Wing flaps size

• Horizontal stabilizers

• Horizontal stabilizer hinge fairing

• Main landing gear skid pads

• Exhaust nozzles

And, for certain configurations:

• Modified lower vertical stabilizer missing

• Dummy scramjet is not represented in the kit

• External fuel tanks missing

The published overall length of the X-15A-2 is 52 feet, 6 inches. The measurements of the actual aircraft, based on my plumb bob drops at the Air Force Museum, revealed an overall length of 51 Feet, 11.5 Inches from the tip of the nose to the aft end of the exhaust cone, a 6.5-inch difference.

Actually it is fairly common for the published dimensions of research and formerly classified aircraft to differ from actual measurements. For example, when I measured the Tacit Blue airframe at the Air Force Museum, again using plumb bob drops, I discovered the fuselage was substantially (about six feet) different from the published dimension! The X-4, again a plane I measured at the AFM, has a vertical height at the tip of the fin that is nearly three feet LESS than the published dimension (and no, it was not because of flat tires!).

The good news is that the kit fuselage is only .1-inch too long, and even better, it’s easily fixed. Just glue the Q-Ball (part A-6) in place on the nose, measure aft .1 inch, then cut off that .1 inch. Round off the nose section to create a “new” Q-Ball section. Very easy!

The Reaction Control System (RCS) holes scribed on the nose of the kit should be drilled out for a better scale appearance. Note that the RCS on the kit are in the correct locations, and are NOT at the common 12, 3, 6, and 9 o’clock positions. Check page 49 of the Aerofax Datagraph 2, North American X-15/X-15A-2, by Ben Guenther, Jay Miller for proper location and offset.

The wing RCS units are scribed on the wing are also in the correct locations, but also need to be drilled into the upper and lower surfaces of each wing. Again, check your photographic references.

The forward edge of the nose gear bay is .06 inches too far aft of the correct position. This is essentially impossible to fix, and not really off by enough to worry about. If you decide to correct this minor flaw, the leading edge of the nose gear door is located .98 inches from the (corrected) nose.

The nose gear wheel well and nose gear door are .10 inches too long. Again, this is not worth fixing, and would be a major job in any case. If you decide to correct the nose gear door, the door is 1.20 inches long, .44 inches wide at the door’s aft edge, and .50 inches wide at the door’s forward end.

The cockpit is very basic, as is the ejection seat. Both could use replacement.

The Skylight research compartment, shown as a scribed rectangle on the turtledeck just aft of the canopy, is too short and too narrow. The actual dimensions are 20 inches long by 17 inches wide, which is .625 inches by .531 inches, centered on the existing door. You can reach the same result by scribing new lines .16-inch outboard of the existing panel lines for the width and scribing a new panel line .10 longer on the aft end of the compartment.

The optical port on the bottom of the fuselage (about 20 feet aft of the nose) is too small, in the wrong location and lacks its raised fairing. Since I did not measure this specific location on the Air Force Museum bird, see page 60 of the Aerofax Datagraph 2, North American X-15/X-15A-2, for a photograph of the port and the fairing. Another excellent view of the location and configuration of the optical port can been seen on the cover of Hypersonic: The Story of the North American X-15.

The kit wings need to be moved forward by .1 inches to be accurately located. This is another exceptionally easy task. Just enlarge the forward end of the wing tab locating slot in the fuselage by .1 inch and glue the wing in place. The distance on the kit from the corrected nose to the correct wing leading edge location is 10.6 inches. The angles and dimensions of the wing outlines are accurate.

The flap outlines are too small and in slightly the wrong location, and are easy to rescribe. The correct leading edge span of the flap is 1.688 inches long; the flap chord at the wing root is 0.96 inches; and the chord at the outside edge is .39 inches.

The horizontal stabilizers are in the correct location, but are too short by 3/16th inches, although the leading and trailing edge angles are correct. This was probably caused by Special Hobby measuring the “footprint” of the stabilizers, which have considerable anhedral, rather than the same-plane length. Cutting Edge already has a replacement part available for the horizontal stabilizers. The leading edge of horizontal stabilizers should be 1.14 inches aft of the trailing edge of the kit wing.

The horizontal stabilizer hinge fairing is the wrong shape and should be corrected. See the photograph on page 57 in the Aerofax Datagraph 2, North American X-15/X-15A-2.

There are some minor problems with the landing gear, which are supplied in the kit in both the “landing” and “flying” configurations. The gear is comprised of a front skid pad that actually touched the earth and a rear support strut that attached the skid pad to the aircraft.

Surprisingly, the front skid pads are NOT the same length in the kit’s “flying” and “landing” configurations. The “flying” (or folded) configuration has the correct length for the skid pad.

For the “landing” configuration, the front skid pad should be shortened by .05 inches measured from the aft end forward. The resulting part should be 1.20 inches long.

The rear support strut is also not the same length in the “flying” and “landing” configurations in the kit, but the change you may want to make will depend on which configuration you are modeling.

For the “flying” configuration, cut the front skid pad and rear support strut apart at the scribed line and ADD .24-inches from the front end of the rear support strut section. Glue the two parts back together, rescribe the line, and you’re ready to go. When you’re finished, the overall length of the combined assembly should be 2.35 inches.

For the “landing” configuration, the correction is more difficult because to make it will significantly decrease the strength of the landing gear, which in this case are supporting the weight of the model.

The rear support struts are .21-inches TOO LONG in this configuration. The obvious fix would be to cut the strut at the point where its diameter changes, the REMOVE .21-inches from the larger piece at the end where you just made your cut. Glue the two parts back together with something inside to add extra strength and you’re finished. The finished strut should be 1.39 inches long.

The small holes in the periphery of the engine exhaust nozzles will look much better if they’re drilled out. As cast, the holes lack depth.

The modified lower vertical stabilizer is not represented in this kit. This additional stabilizer was used to carry various payloads such as the dummy scramjet that was attached during the speed record run. The modified lower vertical stabilizer is 2.72 inches long, with the height at leading edge of .55 inches, and a trailing edge height of .71 inches.

The dummy scramjet is not represented in the kit and must be scratch-built, although there are rumors Special Hobby plans to release this version later. Page 85 from the X-15 Photo Scrapbook shows the dimensions of the scramjet in inches and centimeters.

For the speed record run there were six pitot tubes attached to the leading edge of the modified lower vertical stabilizer. Depending on the specific mission, as many as ten pitot tubes could have been attached to its leading edge. Consult your photographs to ensure the correct numbers of pitot tubes are represented.

You may be able to obtain the generally very good set of X-15A-2 drawings published in the Quarterly Volume II – Issue 5, July 2005 issue of Sky Models magazine. I ordered my copy of the magazine from The Squadron Shop. In my case, I corrected the Sky Model drawings based on my own measurements.

One important error in the Sky Models drawings is that they show the fuselage length as .1 inch too long. All of the error is at the very tip of the nose. If you move the tip of the nose on the drawing aft by .1 inch, everything else on the fuselage lines up very nicely.

Finally, I am a long-time friend of the owner of Meteor Productions, Dave Klaus, and I have supplied research for some of his projects in the past. This was done as a friend helping a friend with a project; I am not an employee of Meteor.

Review Text Copyright © 2007 by Daniel W. Rees
Page Created 20 September, 2007
Last updated 24 December, 2007

Back to HyperScale Main Page

Back to Reviews Page