AVSIM Commercial Aircraft Review

XTreme Prototypes


Product Information

Publisher: Xtreme Prototypes

Description: Experimental “X” Series Rocket Research Aircraft.

Download Size:
198 MB

Simulation Type:
Reviewed by: Mark Kolo AVSIM Senior Staff Reviewer - July 1, 2008


The X-15 is one of, if not the most, recognizable of the “X-Planes” tested at Edwards Air Force Base from 1946 to the present. The X-15 program was a cooperative project of NASA, the USAF, and the USN that was designed solely for the purpose of collecting data to assist with the designs of future spacecraft.

Accelerating away from the B-52 Mothership moments after starting the mighty XLR-99

The X-15 is widely considered to be the first manned spacecraft, as it reached altitudes as high as 354,000 feet during its test program that lasted 199 flights between 1959 and 1968. With the exception of the Space Shuttle, the altitude records of the X-15 have only been broken by one piloted aircraft: SpaceShipOne.

The X-15 from this package, the X-15-1, was the first X-15 delivered to the NASA/Air Force/Navy testing team at Edwards in 1958 where it flew for three years with an interim system of two XLR-11 four chamber rocket motors. After completing 21 flights with the XLR-11 power package, the X-15 was returned to North American, where it was modified to use its designed power: The 1 million horsepower XLR-99 rocket motor.

The X-15’s numerous speed and altitude records make it a contender for the title of most successful research aircraft ever flown at Edwards Air Force Base. The X-15-1 was flown for the last time on October 24, 1968 after completing 81 flights. Today, it hangs in the Smithsonian National Air and Space Museum.

Installation and Documentation

The installation of the X-15 was pretty much standard for payware today, that is, a single .exe file that required a serial number. After I entered the serial number, it was a quick installation, and I was ready to kick the tires and light the fires… or so I thought.

The documentation for the X-15 is absolutely, hands down, the best that I have ever seen for a Flight Simulator product. First off, all the provided manuals have an authentic feel that is supplemented by helpful diagrams, screenshots, and procedures that will allow you to fly the X-15 to the best of your abilities.

The “Utility Flight Manual” provides a brief historical introduction, followed by a description of the product, including screenshots comparing the Xtreme Prototypes X-15-1 to the real thing. The aircraft’s specs and description are next, followed by a complete overview of the exterior model and cockpit.

As this is a very procedure intensive aircraft, the manual’s next 45 pages cover “Normal Procedures and Checklists”. The Appendix section contains valuable “Quick Start” procedure checklists, which allow you to get to mach 6 a little bit sooner. Sticking with the authentic design of the manuals, the FSX specific manual, and the VC Supplement are separate updated files, much like you would have received as a real X-15 pilot.

First Impression

My first impression of the X-15-1 was generally good, as I performed an exterior “walk around” on the ground at Edwards AFB. I did have a bit of concern regarding the realism in all aspects of flying and viewing this aircraft, but they were soon proven wrong. The details and overall feel of this model impressed me the most, and I was very happy to see that the real X-15 was replicated very well by the folks at XTreme Prototypes.

Decending through space

During my first test flight I had quite a few issues getting off the ground. Being a typical computer “geek”, I felt that reading the manual was below me, and I tried to start the engines using Control-E like I usually do when I am in a hurry. After a minute of pounding on the keyboard, the aircraft was still sitting there with no running engine. I then consulted the Quick Start procedures section of the manual, and before I knew it, I was at 70,000 feet doing something like mach 2.8!

The first landing was more of a crash than anything, because once again, I neglected to consult the manual about procedures. I smacked down onto the dry lake bed lawn dart style - stalling, nose down, at about 150 KIAS. My best advice for your first flight in the X-15 would be to READ THE MANUAL BEFOREHAND. I tried to rely on my “Macho pilot skills” and that did NOT work well for the plane, or my ego.


VC view of breaking the sound barrier with the XLR-11 engines

The Virtual Cockpit is a new addition to the X-15-1 package, and has yet to be released for the X-15A-1 and X-15-2/3 packages. Though it is not the most detailed VC that I have seen for FSX, the virtual cockpit of the Xtreme Prototypes X-15 is definitely a great compromise between form and function.

Based on real images of the X-15’s cockpit, XTreme Prototypes did a good job of replicating this advanced research aircraft. Though not all the switches perform a function in the simulator, they do move. This is evident when dealing with the scientific instruments control panel, and adds a ton of realism to the experience of flying this research aircraft.

The amount of detail in the switch areas of the panel is very high, and the 3D modeling of the switches is crisp and well executed. As is the case with most of my flying in FSX, I prefer to do all of the procedures and switchology with a 2D panel or sub-panel, and use the VC for the actual flying part. This setup seemed to work well for the most part, but with all the sub-panels open to properly manage the XLR engines, it became quite difficult at startup and after the engine was shut down. All the gauges and moving parts worked very smoothly, and had a minimal to nonexistent hit on the frame rates.

Approaching Edwards after my first XLR-11 flight. VC view with the throttle subpanel open,

I was a bit disappointed with the blurriness of the VC textures. They were not so blurry that you could not use it, but had a bit more time been spent on the textures here, the VC could have been improved tenfold. It has come to my attention that there is a button somewhere in the VC (Covered in the manual) that allows you to start the engine in a “Control-E” type fashion, but I have not used it, and after a flight or two, the procedures will become familiar enough to just go through them anyway.

The VC lacks some of the weathering, detail and realism that some other VC’s have, but when you are darting through the sky at speeds in excess of mach 2, you are too focused on keeping the plane from entering an out of control death spiral than a few paint chips, or lack of 3D gauges. Overall the VC is much like the real X-15, in that it was not about how good it looked, but how well it performed the task it was designed to do.


The exterior of the four versions included in X-15-1 are a very accurate copy of the real aircraft. All of the X-15’s unique exterior features are executed in a way that allow for both great detail and realism, all without compromising on sim performance (Which is really important when you are flying Mach 3+ outside the atmosphere).

Many of the X-15’s exterior features are textured on (Ball Nose Instruments, Stability Jets, Filler Ports, Rivets), but they are so well done that it is difficult to notice unless you are zoomed in really close. As this model was originally designed for FS9, bump mapping and some other FSX goodies are noticeably absent.

I was pleasantly surprised to find that the X-15 did come with FSX alternate views (From B-52, Looking Back, Nose, Tail, etc.) as they allows the pilot/astronaut to inspect the aircraft more closely. The views also result in some spectacular renditions of the effects that the X-15 comes with.

A later model X-15 with tiptanks and a extra sensor pack on the tail Going vertical over Edwards at Mach 1

The only real issue that I have with the X-15’s exterior is that it seems to be too glossy under certain light conditions, and too flat in others. This is not a very big deal though, and I still rate the exterior of the X-15-1 very highly!


As the X-15 is a rocket propelled aircraft, it relies heavily on effects to ensure the realism. I am very pleased to report that Xtreme Prototypes did a spectacular job creating effects for both the XLR-11 and XLR-99 engines on the X-15. I have to say, that the first time that I started the XLR-99 motor and watched it spit out a massive exhaust flame, I thought that I was dreaming.

A shot from the chase plane of the X-15 starting the XLR-99 engine XLR-11 engines starting up The X-15-1 with XLR-11 engines burning

The effects on the X-15 add an immense amount of realism from the time you start the generators, to the time the last bit of fuel is jettisoned after a successful flight. The effects start when you fire up the APU's during the start procedures, as the exhaust begins to trail out behind the plane. The mid fuselage is covered in frost from the extremely cold temperature of the LOX (Liquid Oxygen) tank behind the cockpit. As you get closer to starting the engines, the fuel tanks pressurize and excess fuel is dumped out the pipes at the rear of the aircraft. As the turbopump comes on, a large cloud of fuel materializes behind the aircraft, which is followed by engine start.

Final approach to Edwards, jettisoning the ventral fin at 5000 feet

Depending on which power package your X-15 has, you will see from one to eight massive streams of fire shoot out from the engine nozzles. Based on the images that I have seen of the XLR-11 and XLR-99 engines in flight, the effects are faithful re-creations of the real thing!

After shutdown, the fuel has to be jettisoned before landing. This effect is much like the one that happens when the tanks are pressurized. Once the tanks are empty, the frost from the LOX tank on the fuselage disappears, and it is time to jettison the ventral fin to ensure clearance for the landing gear. The fin follows a ballistic trajectory for as long as I can see it after it is separated from the X-15.

Overall, the effects are of the highest quality that I have seen, and really completes the X-15 package.


Simply put: The Xtreme Prototypes X-15 panel is probably one of the most complex and detailed that you will ever see in a flight simulator aircraft. (Not including airliners for obvious reasons)

The main panel and numerous sub-panels completely replicate the cockpit of the X-15. Just like the VC, nearly every switch can be moved, but many (Scientific instruments again) do not have an actual simulator function. That said, I prefer to run through the procedures outlined in the manual because it adds realism to the flight.

The panel accurately represents the limited view that the X-15 pilots had. This is even truer during start up procedures, where it is nearly impossible to see outside with all the subpanels open. Any criticism on the layout of the panel would have to be directed at NASA/USAF, but I only had one small layout issue. (The ventral jettison arm and jettison controls are on opposite sides of the cockpit) Other than that, the panel is logically laid out, and all the sub panel open buttons were in good locations.

The biggest issue I had with the 2D cockpit is that some of the sub-panels have to be un-docked to be resized to a point where you can read what switches you are flipping. Much like the rest of the X-15’s features, the 2D panel has its problems, but they are very minor and do not detract from the overall package by any measurable amount.


Though I cannot confirm the accuracy of the sound set of the X-15 package, having never flown the real thing, I find that the sounds are both believable and add to the experience of flying the X-15. The sound of the canopy closing, and the tanks filling and pressurizing become familiar after the first few flights.

The sound of the bubbling LOX, and the wind roaring by the canopy accompanies the starting procedures and the landing glide (Prior to all fuel being jettisoned of course). As soon as the engine (Or engines) come to life, the cockpit is filled with a realistic rocket roar sound.

One sound that is absent from this set is a sonic boom. All the “normal” sounds are present as well (landing gear, flaps, touchdown, etc.) and seem to fit the systems in the X-15. I may sound like a broken record here, but the sounds add tremendously to the realism of the X-15.


A Tracking Camera (Photoshopped Tower) View of the X-15 in flight

The airfile/flight dynamics was my biggest concern prior to flying the X-15. I though it would be either too difficult to control, or way too easy. I am pleased to report that the X-15’s airfile provides challenging but manageable flight dynamics.

That is not to say I would recommend it for a beginner, but you do not need to be a licensed ATP either. The biggest challenge in flying the X-15 is the glide to landing. I followed the procedures laid out in the manual, but I still have a pretty poor “good” landing percentage (50%). Even though the landings were not pretty, all but two or three would have been survivable.

There are currently some issues with the Airfile/Flight Dynamics when using FSX SP2; I was not able to reach speeds of Mach 3 or altitudes over 100,000 feet. The developers know about this issue, and they are working on an update. Even with this restriction to my testing, I flew both of the X-15’s mission profiles (High Altitude, and High Speed) to the best of my abilities.

The aircraft performs predictability in all parts of the flight envelope (Very touchy at high speeds and low altitudes, and mushy at higher altitudes). If the X-15 performs even half as well in the unexplored parts of the flight envelope, SP2 pilots will be in for a real treat when the update is released.

Summary / Closing Remarks

Test System

Dell XPS 400 (Windows XP) Pentium D Processor Microsoft Flight Simulator X SP2 with Acceleration CH Products USB Yoke CH Products USB Pedals

Flying Time:
15 hours (42 Flights)

During my 42 flights with the X-15, I gained a ton of respect for the test pilots who first flew her back in the 50's and 60's (As if I did not respect them enough already).

I did have some issues with the package (Textures, Sub-panel sizes, and the SP2 issues) but they were very minor, and did little to curb my enthusiasm for the package. In my opinion, the package is very well done and realistic.

The challenges of this package make it a perfect choice for the experienced simmer, or a relatively new pilot who is willing to read a LOOOOONNNNNNNNGGGGGG manual completely. The X-15 package is a unique aircraft and is a blast to fly. It is great for throwing into any virtual pilot’s rotation for a quick flight to space and back.

I would highly recommend it to any virtual pilot who has an interest in the X-planes or other high performance aircraft.

On the ground after a flight


What I Like About The X-15

  • Unique Product
  • Well executed model, VC, and effects
  • Great Documentation
  • Challenging, but fun flight model
  • Start up Procedures (Not for everyone)


What I Don't Like About The X-15

  • Speed and Altitude issues in SP2/Acceleration (A fix is in the pipeline)
  • VC textures could be a bit sharper



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The review above is a subjective assessment of the product by the author. There is no connection between the producer and the reviewer, and we feel this review is unbiased and truly reflects the performance of the product in the simming environment. This disclaimer is posted here in order to provide you with background information on the reviewer and any connections that may exist between him/her and the contributing party.

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