Flying the X-15 for Flight Simulator

The flight model of the X-15 for Flight Simulator has been tuned for the computer pilot to have fun and to learn about this incredible airplane while maintaining stability and control of the aircraft at all flight regimes allowed by the simulator. We do not pretend that the flight model truly reproduces the exact flight characteristics of the real X-15 rocket plane but we tried our best to develop a unique add-on aircraft that is fun to fly while pushing the simulator to its limits and simulating nearly every step and procedure of a typical X-15 mission.

The X-15 add-on aircraft has been designed to simulate rocket propulsion and its related fuel systems including, in the case of the X-15, the use of three different propellants and their pressurization methods. Therefore, "CTRL-E" (the standard Flight Simulator auto-start command) will not work with the X-15 as it does with conventional FS aircraft.

Since we are taking off from the ground and because there is no B-52 carrier aircraft to fly our virtual X-15 to a proper altitude and heading before launch, we should treat the X-15 as, well, a "B-52 addon" until we reach our intended "launch point". This means that we should aim for a Mach .78/FL370 launch while respecting the X-15's limitations.

(You can also use the slew mode or the map view to position the aircraft at launch altitude and speed. Taking off from the ground is rather fun however, and is something the real-world X-15 pilots could not do!)

We found that the best way to achieve takeoff is to accelerate on the runway centerline with the engine at "idle" (which still yields about 50% thrust with the XLR-99 engine) and to leave the throttle in this position until the actual launch (Mach .78/FL370). Note that half-throttle is achieved by only igniting half the combustion chambers on the XLR-11-equipped aircraft: upper engine chambers 1 and 3 and lower engine chambers 1 and 3 together.

The airspeed indicator on the X-15 main instrument panel is provided with a "barberpole" (actually a small red pointer on the left upper side of the instrument) which limits the airspeed at low altitudes to around 690 KIAS. As the aircraft climbs through 26,000 feet, the barberpole pointer moves to allow higher airspeeds thus reflecting the lower air density. The important thing to remember is that the indicated airspeed must be kept below the barberpole indicated value. You may refer to the kneeboard reference tab for other airspeed vs altitude limitations, but then again, you do this for every aircraft you fly, don't you?

Rotate at 260-280 KIAS in a smooth but swift pull-up to about 35 degrees nose-up while retracting the gear. You may want to use the pitch error pointer (the small horizontal pointer on the left side of the attitude indicator) and the pitch angle set control knob (a separate instrument located at the lower right corner of the attitude indicator) to fine tune your pitch angle.

Before takeoff, select the pitch angle you want with the pitch angle selector control knob (the small lever must be clicked to get positive angles). As you maneuver the aircraft to within +5 or -5 degrees of your selected pitch, the pitch error pointer on the left side of the eight-ball will act as a vernier pitch indicator which you can use for fine-tuning the pitch angle. Initial pitch-up and precise pitch angle control was an essential part in every X-15 mission. You should first approximate the desired pitch angle with the ball and then focus on the pointer for precise adjustments. The pointer moves in the same direction as the ball so it acts as a magnifying glass for pitch.

Be careful not to take too long to achieve the correct pitch or the airspeed may get out of hand. In this case, you may need to pitch up to very steep attitudes in order to regain airspeed control (remember the engine "idles" at 50% thrust).

As you climb through FL370, check your IAS and try to maintain at least 350-400 KIAS by carefully adjusting your pitch. Remember that you should be flying trimmed and leveled at around Mach .78 and FL370 before fully opening the throttle.

Once the launch altitude and speed are attained, you may proceed with the launch itself, which in our case is merely a question of setting the throttle to 100% (and/or igniting all the chambers on the XLR-11 engines) since the normal start-up procedures were performed on the ground. Once again (as during most X-15 missions), you should pitch up to about 30-35 degrees (in reality, each mission called for a very accurate angle, which can be set with the attitude indicator's vernier pointer and the pitch angle selector knob) and watch the X-15 accelerate. Be careful not to exceed 100,000 feet in FS2004 because the simulator has an unpredictable behavior beyond that point. Also, Mach 4.65 seems to be a hard limit of the sim. Could this be the famous "wall" mentioned by so many test pilots in the late 40's?

Some X-15 instrument panels are provided with a dynamic pressure gauge (upper center section of the main panel, above the attitude indicator) which allows you to "see" how much air is actually hitting your wings and control surfaces. On the low side of the gauge (low airspeeds or very high altitudes) you see that not much control is possible below 250 psf (hence the high rotation speeds on takeoff). Unfortunately, the ballistic control rockets on the X-15 are not (yet) supported in Flight Simulator so control at very high altitudes and at very low dynamic pressure is kind of touchy. Be careful not to exceed the maximum dynamic pressure and acceleration values (again, you may refer to the reference tab of the kneeboard) or structural damage and/or "skin overheating" may occur!

During your mission, it is recommended to use an extra spot view, as visibility out of the cockpit is rather limited, especially at high pitch angles. It also makes for some great screenshots!

An engine timer (stopwatch) was installed in the X-15 equipped with the XLR-99 engine. The timer was automatically started during the ignition sequence and would tell the pilot when to shut down the engine, depending on the mission's objectives (altitude and speed to be attained). You can use the engine timer (located on top of the main instrument panel of your X-15 addon) for the same purpose.

If we exclude the climb to the launch altitude (during captive flight), a typical X-15 mission would last for about 10 minutes, of which about 60-90 seconds saw the engine burning (note that the run time was substantially longer on the airplanes equipped with the XLR-11 engines). The remainder of the flight was maintaining course while on a ballistic trajectory at several times the speed of sound, holding the correct angle-of-attack for reentry into the earth's atmosphere without being consumed, decelerating and finally, gliding our way back home. This is the way you should fly the X-15 for Flight Simulator as well.

Get to know the Mojave Desert and the emergency landing sites that this incredible landscape has to offer and try to make it back to Edwards or land on some dry lakes, as Flight Simulator provides you with many strips and Air Force bases in the area. Be aware however that at X-15 speeds and altitudes, the distances between the landing areas appear quite short and therefore require accurate descent planning.

Of course, flat sand does the trick as well, as long as it is not too soft. Approach at 300 KIAS (flaps down, 100 feet AGL), drop the gear right before flare and touchdown at 174-200 KIAS. Don't forget to jettison the remaining propellants and the lower ventral before landing.

Refer to section V in the manual for complete approach and landing procedures.

Happy record-breaking!