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This is a "pilot report" manufactured mainly from information in a copy of the X-15 Flight Manual that was last updated on December 29, 1961. Originally I posted it to the rec. aviation and sci. aeronautics newsgroups in the late 1980's. The current edition has some updates to reflect things I've learned since then from other sources: Books, magazines, videos, and even a little bit of personal contact with former X-15 test pilots. It's written in second person, to encourage communication of "this is what you would experience as an X-15 pilot".

Writing as a sailplane (glider) pilot, I like to think of the X-15 as the most radical of all motorgliders. It launched with its own breed of aero-tow, had stupendous performance while under power, and returned as a glider. Admittedly its glide performance had a lot in common with the former top of Mount Saint Hellens -- it was fairly similar to that of the Space Shuttle, an F-104, or a nicely shaped rock.

 

 

 

 

This pilot report is split into these four parts:

 

Part 1:

General Description & Walkaround

 

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X-15 Rollout

The X-15 is  mainly a cylindrical fuselage, 49 feet 2 inches long. "Wing root" fairings begin just aft of the cockpit and extend nearly the entire length of the fuselage on each side. From these protrude stubby wings spanning 22 feet 4 inches and horizontal stabilizers. Vertical stabilizers stand both above and below the fuselage (dorsal and ventral), giving the aircraft a total height of 13 feet 1 inch.

Let's start a walk-around at the aft end. You're immediately looking into the business end of the XLR-99 rocket engine, which consumes up to 15,000 pounds of anhydrous ammonia and liquid oxygen in about 80 seconds on a typical flight. The engine's main chamber is made of CAREFULLY shaped and welded tubing that circulates ammonia before it's burned. This preheats the fuel and cools the engine that otherwise would fry in its exhaust.

Around the rocket nozzle, below it on the ventral fin, and at the aft end of both wing root fairings, are 25 assorted drains, vents, and jettisons. The largest three are the turbopump exhaust and the jettisons for LOX and ammonia.

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Right quarter view of X-15 #2 on B-52 pylon at night. is reproduced from /files/pics/pic12.jpg on the cd accompanying X-15 - The NASA Mission Reports. This reproduces a NASA photo	Color photo of drains and vents, mainly on lower part of flange around rim of XLR-99 nozzle, is a photograph of the X-15A-2 in the US Air Force Museum, 7/25/2001, photo by author (Paul Raveling).	Rear view

If you use your XRAY eyes to peer past the LOX jettison in the left fairing you'll first see a small spherical tank holding helium at 3600 psi. This particular helium purges explosive gases from the engine compartment, preferably before they ignite. Behind that is the end of a Godzilla-sized piece of plumbing that carries LOX from its tank to the engine compartment. The right fairing looks about the same, but the plumbing there carries ammonia.

Lurking behind the XLR-99 is the turbo-pump and a maze of assorted devices and plumbing. One of the devices is a gas generator, which is the X-15's breed of catalytic converter. When you feed 90% hydrogen peroxide into it, the H₂O₂ decomposes into superheated steam and oxygen on its catalyst beds. The resulting gases drive the centrifugal turbine in the turbopump, which then drives separate compressors for the ammonia and LOX.

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View from directly aft of X-15 on the pylon of its B-52 carrier aircraft is a NASA photo.  This photo shows the 1959/1960 interim configuration using a pair of XLR-11 rocket engines, each with four chambers, instead of the single XLR-99 rocket engine.

Back on the outside, the stabilators (horizontal stabilizers also used as control surfaces) are the simplest pieces.

They have 15 degrees anhedral, or cathedral, if you prefer. They swivel together for pitch control, and move differentially for roll control, since the wings have no ailerons. These, as well as the "rudders", have opposed sets of irreversible hydraulic actuators -- you can make them push, but they won't push back, so you won't feel any air loads on the stick. Cockpit controls make up for this with a system of spring bungees to provide "natural" feel and pitch trim.

The vertical stabilizers get more complicated. Their triangular cross section provides some hypersonic stability and adequate room for several hydraulic actuators. Both dorsal and ventral fins are split  longitudinally into a fixed part and a movable part. Panels on the aft third of the fixed (inboard) sections spread apart to serve as speed brakes. It's best not to use them if you're slow (like subsonic), because the only way to close the speed brakes is to let a fairly heavy air load blow them back.

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Side view of the empennage of the #3 X-15 .

 The top of the dorsal fin and the bottom of the ventral fin rotate to act as a rudder. The ventral piece extends below the landing gear, so it has four explosive bolts and an initiator (an explosive-driven piston) to jettison it before landing. Just remember not to jettison the ventral above 300 knots or mach 3.5, whichever is lower.

The main landing gear are skids that are locked against the aft fuselage until you're ready to release them. At that time they drop into place and lock, thanks to gravity and air loads. Since they don't have wheels, you don't have brakes. They're also so simple and reliable (right?) that they also lack any device to tell you, the pilot, whether they're up or down.

The wings have no dihedral, but they do have flaps and rockets. The rockets, two per wing, are thrusters to supply roll control out where there's little if any air. Like the turbo-pump's gas generator, they're powered by hydrogen peroxide.

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The first of the three cutaway views of the X-15 is a widely reproduced NASA illustration. One of the published renditions is on page 111 of NASA book SP-4303, On the Frontier, by Richard P. Hallion.

This  cutaway view is another widely reproduced graphic,

Cutaway view from page 1-2 of the North American Aviation X-15 Flight Manual (1962).

Almost all of the fuselage's spare volume is split between the liquid oxygen tank in the forward end and the ammonia tank in the aft end. Each is divided into three interconnected chambers and a concentric cylindrical core. The LOX tank's core holds helium for pressurizing the peripheral ends of the two propellant tanks. Propellant feeds out through overgrown sewer pipes at the tank ends nearest the center of gravity.

Other tanks for hydrogen peroxide, helium, and liquid nitrogen are crammed into the fuselage at either end of the main propellant tanks and between them. The compartment between the LOX tank and the cockpit also houses two APU's (auxiliary power units), each geared to an alternator and a hydraulic pump. The APU's are also turbines powered by hydrogen peroxide from their own gas generators.

One token sample of this plumber's nightmare (or is it plumber's heaven?) is what the nitrogen supply does. It cools the No. 2 electronics compartment, the alternators, the APU upper turbine bearings, the stable platform (for inertial guidance), and the ball nose. It purges the hydraulic reservoirs and inflates canopy and electronics compartment pressure seals. And it does some more things mentioned when we inspect the cockpit. And that's simple compared to the helium systems!

Walking forward again, we'll pass the cockpit for now. Next comes the nose gear, the proud possessor of two wheels. Of course it isn't steerable, it just castors -- who needs to steer anyway with so many  miles of dry lake for the landing rollout. Like the skids, it drops by gravity and air loads, but there's a catch: At a positive AOA the nose gear door would have an air load trying to keep it closed, so it gets help. Another initiator gives it a boost, and a small air scoop opens down from it to get the airstreams to hold it open.

Up at the nose, eight rocket nozzles supply yaw and pitch control for the ballistic control system. All the  way forward is the q-ball -- a ball nose that measures dynamic pressure ("q" in aerodynamic equations) while swiveling around two axes to measure angle of attack and sideslip. These angles are worth knowing both at reentry and at low speeds, where the X-15 is least stable. However, before reentry it's up to inertial instruments fed by gyroscopes and accelerometers to tell you which way you're pointed and which way you're actually going.

 

 

Part 2:

Cockpit Check

 

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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.
	NASA photo ECN1291, illustrating a pilot in a cockpit as configured late in the research program. This photograph gives some sense of the very limited space within the cockpit, but necessarily was photographed with the canopy open. The closed canopy has very little clearance over and around the pilot's helmet.

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This reproduction of a photo and illustrations of the pilot's head restraint for use during high-G deceleration is reproduced from Apogee Books

This ejection seat diagram is Figure 1-14 (Page 1-44) in the 1962 X-15 Flight Manual. The seat was designed for use at speeds up to Mach 4 and altitudes up to 125,000 feet.

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Center Pedistal

Flight control diagram

Left Panel

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 un-pressurized 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.

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).

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.

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.

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.

 

 

Part 3:

Heading Out to Launch

 

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NASA photo ECN885, which NASA also identifies as EC65-885, shows an X-15 being carried to its launch point under the wing of a B-52.. This particular image was scanned from an original print from the estate of Maurice King, a NASA Dryden mechanic who worked on the X-15s.	Getting ready for takeoff in the predawn light.	With pilot aboard, the X-15 and its B-52 carrier aircraft near the end of preflight preparation.

You, the pilot, arrive at the Base while others are finishing final fueling and system checks in the hours approaching dawn.

You'll start with the X-15 already hanging from a pylon on the B-52 carrier aircraft. Don't bother with a nitty gritty total hardware preflight; the taxpayers thoughtfully provided a whole staff to do it for you. Anyway, you're cooped up in a pressure suit, pre-breathing 100% oxygen.

After entering the cockpit, strap in and and run through the interior check. That's 120 checklist items, ending with "close canopy". By now the B-52 is supplying power, breathing oxygen, nitrogen, and liquid oxygen to top off loss from the oxidizer tank.

That LOX loss is due in part to pre-cooling the engine, which you initiate in the captive takeoff checklist. While pre-cooling, LOX flows through almost all of its usual path to the engine, then dumps overboard at the liquid oxygen prime valve. You'll precool for 10 minutes, then start a schedule of 20 minutes off and 7 1/2 minutes on.

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The B-52 carrier aircraft rotates for takeoff on an X-15 mission.  An F-104 chase plane prepares to join up immediately.

 This B-52 is actually a Boeing NB-52A, Air Force Serial Number 52-003, known as "Balls 3" at NASA Dryden and the AFFTC (Air Force Flight Test Center) at Edwards Air Force Base.  This was the third of three B-52A models manufactured at the start of the B-52 production run.

 The second carrier aircraft was an NB-52B, which entered NASA service for this purpose in 1959. This aircraft remains in service at the time this web page is edited, having carried the X-43A Hyper-X on March 27, 2004. With delivery to the Air Force in 1955 it has already been the oldest B-52 in active service for several decades, and it stands at the brink of logging half a century of active duty.
 

 Takeoff isn't just you and the B-52.  Typical missions will add three chase planes, rescue helicopters, a C-130, and an array of ground vehicles deploying to places between your planned takeoff location and Edwards.  Some of this force goes to dry lakes that might be needed for emergency landings along the planned route of your flight.

A few things will need heat during the climb, so be sure to turn on the heaters for the windshield, your face mask, and the nose ballistic rockets (the X-15's nose, not yours). Also ask the B-52 crew about the hook heater.

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This photo from a chase plane probably was taken shortly before launch.  The visible hydrogen peroxide jettison is part of item 6 in the countdown checklist (1962 procedures),  Less obvious vapor emissions probably are from simultaneously tested jettison of LOX (liquid oxygen) and ammonia.

Once at altitude, go through the 27-item pre-launch checklist. Among other things, you'll switch to the X-15's breathing oxygen, shut off liquid nitrogen but not gaseous nitrogen from the B-52, and start the APU's.

Next comes the 29-item pre-countdown checklist. Among other things, you will:

• Stop LOX transfer from the B-52.
   
• Cycle the propellants tanks from vent to jettison, then to pressurize.
   
• Check the flight controls and trim settings. Launch control surface deflections should be 0 degrees for everything except the horizontal stabilizers, which should be 0 to 2 degrees leading edge down. Be careful - if the position's too far off when you drop, the X-15 can pivot on its pylon and slide into the engines just outboard on the B-52.
   
• Turn on instrumentation.
   
• Start the final engine precool cycle.
   
• Set the engine prime switch to PRIME. This opens the liquid oxygen and ammonia main feed valves and the hydrogen peroxide upstream safety valve for the turbo-pump, and it feeds helium to the engine control and purge systems. It takes 30 seconds to complete priming.
   
• Depress the turbo-pump idle button. This opens its H2O2 downstream safety valve, allowing the pump to begin running. When it's brought ammonia pressure up to 210 psi, the turbo-pump speed control system will take over to keep it at idle speed.
   
• Set the igniter idle switch to IGNITER. Now you have 30 seconds to finish preparations, drop, and fire the XLR-99's main chamber or to shut down. Don't leave the igniter on longer, or the XLR-99 will be damaged by overheating.

What happens when you go to igniter idle is this rapid-fire sequence:  

• The engine is purged with helium for 2 seconds.
   
• Three spark plugs are energized in the first stage igniter, which is a small combustion chamber ahead of the 2nd stage igniter and main chamber.
   
• Ammonia and gaseous oxygen enter the 1st stage igniter and start burning. The gaseous oxygen is produced by routing liquid oxygen through a heat exchanger that surrounds the turbopump exhaust.
   
• When chamber pressure rises sufficiently, gaseous nitrogen from the B-52 flows in to mix with the 1st stage igniter gases.
   
• Ammonia and LOX begin flowing to the second stage igniter, which is a larger chamber, where they're ignited by the jet of burning gas from the 1st stage. This igniter alone produces 1,500 pounds of thrust.

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This is the #2 X-15 just after being dropped from the B-52. The rocket engine would be in igniter idle just prior to drop, the pilot would tend to waste little time at this point to start the engine. At this moment the pilot also will be correcting the X-15's tendency to roll right on release. The initial roll moment is a consequence of local airflow below the B-52 wing, between its inboard nacelles and the fuselage.

When the 2nd stage igniter and main chamber build to 150 psi, about 5 seconds later, the jet into the main chamber is sufficient to light it up. You're ready to go, so ask for the countdown -- fast!

They're serious about that 30 second time limit for either lighting up or shutting down. When there's 7 seconds more of idle time allowed, an IDLE END caution light comes on. When time runs out, a NO DROP light tells you to shut it down.

So... when you get through the brief countdown and you drop, don't waste much time before moving the throttle from OFF to at least 50%. That'll light the main chamber, giving you the second part of a big one-two punch.

 Part 1 was the drop itself. Starting to fall may sound like a gentle and mellow start, but it can feel more like being catapulted straight down. In the early flights even a short countdown wasn't adequate preparation when the B-52 crew initiated the drop -- NASA soon re-rigged the system so that it would be the X-15 pilot who tripped the release, giving you at least a feeling of being just a bit more ready for the event.

 

Part 4:

Flying the Mission and Returning

 

 
 
 

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After you light the torch you need to fly precisely in the face of some unusual challenges. Let's say the mission at hand is a more or less full bore altitude flight.

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This photo, NASA number EC65-884 has been widely published and reproduced, usually in the wrong orientation -- rotated 90 degress counterclockwise. This error is perpetuated to this day on the NASA Dryden web site and has spread from there to many other published sources.  One that got it right was the September, 1962 issue of National Geographic.
	This photo from a chase plane, first published in 1962,  shows the X-15 pulling up into a climb after launch. Final climated usually was a bit more than 40 degrees for altitude flights. Sunlight refracting through the chase plane's canopy.transforms a simple image to a work of natural art.

Part 1 is to go to full throttle and pull up to just the right climb attitude. With 57,000 pounds of thrust from the rocket, maybe even 60,000 on a good day, you start at 2 G's acceleration while your tanks are full and your gross weight is about 33,000 pounds. As you burn fuel and oxidizer, with weight dropping to barely over 15,000 pounds, acceleration doubles to 4 G's. Rocket motor performance can vary depending on lots of factors that sound small, but sometimes they add up instead of cancelling each. If you compound that deviation by missing your planned climb attitude by as little as 1 degree, the results begin to look astronomical. Flying with precision that would give most pilots enormous pride, your imprecision can easily produce a 30,000 foot overshoot or undershoot in maximum altitude.

All that precise flying happens on the gages. Let's say today's mission profile puts you in a climb attitude of 42 degrees. If you glance out the windows in this attitude you see nothing but dark blue sky that's quickly getting blacker as you climb. With no visual cues and thrust overpowering gravity your sense of balance lies -- it feels as if when you pulled up the rotation never stopped and you've gone past vertical, to an inverted attitude! Those instruments connected to the gyro-stabilized inertial platform are what you need to believe to stay in touch with reality.

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This is one of several widely reproduced diagrams of an X-15 mission profile.  This particular one is Figure 5 on Page 40 of the Proceedings of the X-15 First Flight 30th Anniversary Celebration.

As you climb out of the atmosphere the aerodynamic flight controls lose their effectiveness. Here you have to transition from flying with the right hand side stick (and rudder pedals) to flying with the left-hand side stick, for the hydrogen peroxide thrusters. That's unless you have the luxury of flying the #3 X-15 -- its adaptive controller, the MH-96, lets you use only a single side stick and automatically blends aerodynamic controls and reaction controls.

On today's altitude flight either you cut the engine after an 82 second burn or the X-15 burns exhaust enough ammonia and LOX to burn out by then without your help. That's another variable that makes a big difference in peak altitude, if you have power on for an extra second you can expect a sizeable overshoot. Now you're weightless, still climbing in a ballistic arc. In a couple minutes today's flight tops out at about 300,000 feet over the high deserts of Nevada and southern Califoria.

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As you pitch over you can now catch a spectacular view of the southwest U.S. The view shown here is the Colorado River Valley from 210,000 feet.. In the words of Robert White, "My flights to 217,000 feet and 314,750 feet were very dramatic in revealing the earth's curvature ... at my highest altitude I could turn my head through a 180º arc and wow! - the earth is really round. At my peak altitude I was roughly over the Arizona/California border in the area of Las Vegas, and this was how I described it:  looking to my left I felt I could spit into the Gulf of California.  Looking to my right I felt I could toss a dime into San Francisco Bay." If the coast is clear that far north, you can just about make out Puget Sound, nearly a thousand miles away..

Coming back down you carefully establish the correct attitude for reentry into the atmosphere as a very fast glider with a truly crummy glide performance. REAL gliders are painted white to help them keep cool, by reflecting solar energy. The X-15 is painted black to help it keep cool, by radiating the heat that builds up rapidly from air friction. A few parts of the nose, wings, and stabilizers briefly hit temperatures up to 1,200 degrees and glow red hot during reentry.

Pulling out of the reentry is one of the maneuvers that lets the pilot know this is no ordinary realm of flight.  If this altitude flight topped out at 350,000 feet you can expect to be coming out of reentry at Mach 5.4 in a 40-degree nose-down attitude.  Pulling out of this dive requires pulling an average of 5 g's for about 20 seconds.  If you only need to turn through a mere 10-degree heading change at Mach 5.3, expect to pull 3 g's for 20 seconds.

There are a few unusual but modest control couplings. At low angles of attack, roll inputs couple to a favorable yaw.. Above mach 2.6, roll response gets quicker as angle of attack increases.  At least that's what the manual says -- Scott Crossfield reports that there's virtually no roll/yaw coupling, she rolls nicely.

As the X-15 slows down and drops, stability degrades and allowed yaw angles decrease. Below about 40,000 feet and mach 0.5, minimum control speed is determined by stability; above that point it's governed by buffeting at the tail. Stability margins allow you to fly AOA's up to 20 degrees, but the pre-stall buffet starts at 13 degrees.

Stability problems can be evil. Conventional wisdom says that you're NEED the electronic stability augmentation systems (or the SAS functions built into the MH-96) or your chances for a survivable reentry are puny. Hypersonic stability trouble can bite in big ways, including the sort of inertia coupling that earlier killed Mel Apt in the X-2.

Going back to being a glider approaching the landing pattern, expect a sink rate of about 150 feet per second (9,000 fpm) at mach 0.75. That gives a max L/D of almost 5:1 at 40,000 feet, but realistically you can expect closer to 4:1.

Finally, you have to land at Edwards Air Force Base. Field elevation is 2,200 feet for a somewhat groomed runway on the dry lake bed. Approach will be sort of a 360 overhead pattern; it'll actually be a tightening spiral because true airspeed drops while you descend at a constant indicated airspeed.

 

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Flight Path

 Landmarks in the pattern on this flight are:

145 seconds to touchdown, 28,900 feet: High key point

This is 2 miles short of the approach end of the runway and 1.5 miles to its right. You should hit it at 300 knots and roll into a 45-degree banked turn to the left. You'll maintain 300 knots IAS and the 45-degree bank until just before you flare.

108 seconds to touchdown, 20,900 feet:

270-degree key point: "Crosswind leg",

90-100 seconds to touchdown, below 17,000 feet:

Pressurize the propellant tanks. They were switched to Vent at burnout, but they need pressure now for two reasons:

• To prevent sand and dust at low altitudes from entering the tanks through their vents.
• To keep the tanks from collapsing. The vents may not keep up with the rapid change in ambient pressure at low altitude.

75 seconds to touchdown, 14,100 feet:

Low key point, "downwind abeam" (opposite approach end of runway, about 3 3/4 miles from it).

46 seconds to touchdown, 8,500 feet:

90-degree key point, "base leg".

30 seconds to touchdown, 5,500 feet:

Jettison the ventral.

19 seconds to touchdown, 3,500 feet:

Roll out onto the runway heading and drop the flaps. You're still at 300 knots.

15 seconds to touchdown, 3,000 feet:

Drop the gear and begin to flare. The flare is a 1.5 G pullout.

8 seconds to touchdown, on the deck, just above 2,200 ft field elevation:

End of flare; airspeed's dropping through 262 knots.

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Landing with F-104 chase plane

0 seconds:

Set it down when airspeed drops to 200 knots and ride until you stop. With no brakes and no steering, you're almost a passenger now.

Well, not entirely. You can actually steer a little bit by using the stick as if you're banking: The stabilators will shift weight from one landing skid to the other and will steer you in the direction you've moved the stick while you're fast enough.  When the speed drops off, force generated by the stabilators drop too, and you do finish the rollout as a non-steering passenger.

Finally, go through the after-landing checklists to secure everything.  As the B-52 offers its salute with a flyby, convince the folks on the ground and the ones who get out of the chase planes that a modest celebration is in order.  Or maybe a big celebration, this flight may well have been another milestone in aviation history.

 

 

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