X-15 Cockpit Check

X-15 pilot report, part 2:
X-15 Cockpit Check

This is a cozy place, don't mess with it if you're claustrophobic. Admittedly it has just a bit more room than a sailplane cockpit, but there's LOTS of stuff in it and you can't see much when the canopy is closed. You get two windows barely larger than slits to peer out of -- the rest is utterly metallic and opaque.

One of the nice touches on top is a head brace that folds downward in front of you.That makes deceleration at reentry a fair bit easier to handle. Another necessary nicety is that the windows are double glazed. In early flights the X-15 pumped Heated gaseous nitrogen between the panels keeps them from icing over. This wasn't entirely trouble-free, so it wasn't long before the nitrogen gap was replaced by a transparent electrical heating element.

The cockpit is unpressurized below 35,000 feet, but it's air conditioned. Above 35K it's pressurized to 3.5 psi by nitrogen. Your pressure suit gets another nitrogen feed to keep it at 3.6 psi.

The ejection seat is almost an airplane itself. If you need it, it'll unfold fins, put you in a nice attitude, escort you to low altitude, then blow pieces of itself away and deploy your chute. According to the manual, it will "permit safe pilot ejection up to Mach 4.0, in any attitude, and at any altitude up to 120,000 feet". You get your choice about how much to trust those limits, such an ejection has never been done.

Seat diagram: medium scale large scale

Once settled in the seat, you're looking at about 130 odd gages, switches, lights, and controls of assorted descriptions.

First, there's a conventional center stick and rudder pedals. There's also a console stick at your right hand for use when G loads make it difficult to use the center stick. Both are mechanically coupled together and to a system of bell cranks that sum their inputs with those from the Stability Augmentation System (SAS).
X-15 cockpit, early configuration
A horizontal stabilizer position indicator is located on the cockpit wall next to the console stick. This is a must-check item before dropping from the B-52 carrier aircraft and before beginning reentry.
Flight control diagram
A third stick, for the ballistic control system, is at your left hand. When the ballistic control rockets are armed, you can:

Move it left or right to control yaw
Rotate it to control roll by firing wing thrusters
Move it up or down to control pitch

Other ballistic inputs come from the Reaction Augmentation System (RAS), which is the no-air equivalent of the SAS.

The same left-side panel houses the speed brake lever and the throttle. The throttle allows a choice of "off" or any thrust setting between 50% and 100%. In the early days it could go down to 30%, but the XLR-99 rocket motor was prone to flickering out when it was developing only a measly 4 1/2 tons of thrust.

The main instrument panel is divided into three sections: Engine instruments on the lower left, APU's on the lower right, and flight instruments at top center. Both engine and APU sections are mainly an assortment of pressure gages, temperature gages, fire warning lights, and sundry switches.

X-15 iinstrument panel, 1962 configuration

Legend identifying X-15 instrument panel gauges and controls

The most prominent flight instrument is a big attitude indicator, planted squarely in the middle. It looks fairly ordinary, but it's accurate throughout 360 degrees of rotation around any axis you care to name.

Scanning clockwise around the attitude indicator, starting just below it, the flight instruments are...

Roll rate indicator, calibrated to 200 degrees per second. The X-15 is pretty agile in roll, but you need to limit the rate to no more than 50 degrees per second in some conditions for the sake of stability.
Altimeter: Looks ordinary, but it has a cutout that unveils warning strips when you're dangerously low -- under 16,000 feet.
Airspeed: Usable from 100 to 1,000 knots; has a vernier drum to show speed to 1 knot anywhere in this range.
Angle of Attack: Reads -10 to +40 degrees. Stay below +20 degrees to avoid stability problems, or +17 1/2 after jettisoning the ventral.
Accelerometer: Reads +12 to -5 G's. Allowed load factor ranges from +3/-2 G with a full load of propellant to +7/-3 G at burnout weight.
Azimuth indicator: A high class compass. Like the attitude indicator and the next few instruments, its reference is the gyro-stabilized platform in the "Inertial All-Attitude Flight Data System".
Inertial height (altimeter): Shows altitudes up to 1 million feet. The little hand reads hundreds of thousands, the big hand reads tens of thousands.
Inertial speed: Calibrated for any speed up to 7,000 feet per second. That translates to 4,150 knots or 4,773 mph.
Inertial vertical velocity: Reads up to 1,000 feet per second (60,000 fpm) in increments of 100 fps.

We'll skip the remaining cockpit clutter, only because it's generally less amusing, though some of it will appear in the test flight.

This pilot report is split into these four parts:

    1. X-15 General Description & Walkaround
    2. X-15 Cockpit Check
    3. X-15 Flight: Heading Out to Launch
    4. X-15 Flight: Flying the Mission and Returning

Related to all four sections:

Photo credits and pointers to related resources
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Send questions and comments on the SierraFoot X-15 pages to Paul Raveling.
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