Model of a the famous CIA spy plane. Features motorized elevons, rotating and illuminated engines, motorized control mast and custom stickers.
Completion date: 16/06/2013
Power: electric (Power Functions)
Dimensions: length 92 studs / width 46 studs / height 13 studs
Weight: 1.002 kg
Motors: 1 x PF Medium, 2 x micromotor + 5 x PF Medium in the base
I have been tempted to try and build an aircraft for a long, long time. So long, actually, that I have bought the minifigs for this project no less than 3 years ago. It took me really long to get around to finally building it, because I had zero experience with LEGO aircraft outside the official sets, because the subject is somewhat exotic and there are few pieces that really fit it and even fewer builders that provide any points of reference. Eventually, being inspired by a whole line of great looking planes from a fellow LUGPol member mrutek, and having found a big and spectacular SR-71 by Lego Monster, I have made my first attempt at LEGO aircraft of any kind: this.
The original SR-71 Blackbird is nothing less than a legend, and a video below may explain some of the reasons for it:
If you don’t have time for watching it, let’s just put together some interesting, but not exactly well known facts:
- the SR-71 Blackbird holds the world record for the fastest air-breathing manned aircraft since 1976
- the Blackbird’s safe operational limit is the speed of Mach 3.3 and the altitude of almost 26,000 meters. What makes this plane unique is that it maintains speeds above Mach 3 for most of the flight, for a number of reasons, including the engines that need less fuel at higher speeds.
- the SR-71′s speed is limited by the engine air intake design, which could be overheated and melted at higher speeds. Back in 90′s there already was a new air intake design that would theoretically endure speeds up to Mach 6.
- the planning & preparation procedure for a single Blackbird flight is 36 hours long.
- 32 SR-71s were built and 12 lost to accidents. Not a single one was lost in enemy action.
- the Blackbird’s engines are unique turbojet-inside-a-ramjet hybrids. The cones in front of the engines are shock cones, used to slow the passing air down to subsonic speed, and they can be rectracted by a the plane’s computer at higher speeds.
- it takes a special cart housing two V8 engines to kickstart the SR-71′s engines, one at a time.
- at top speed, the Blackbird’s skin reaches temperatures as high as 316 °C. 85% of the plane’s structure is titanium, one of the few materials durable enough, and even the tires are made of aluminium/latex compound and pressurized up to 12 times the car’s tire pressure in order to withstand the heat.
- when heated up, the whole plane grows several inches longer. That required an unusual structural design, in which parts of the fuselage fit only loosely when on the ground, to expand into final shape when in air. It means, among other things, that the plane is leaking fuel, and it needs to be refueled in the air after a takeoff. A special JP-7 fuel is used for Blackbird, because it only lights in very high temperatures and thus makes the plane safe despite leaking.
- most of the wings surface is corrugated to form a skin that smooths out when the plane gets hot. That’s what the red lines on top of the Blackbird are for – they indicate to the ground crew the fragile surface that should not be stepped on.
- during Blackbird’s production, the Soviet Union was the world’s primary source of titanium. That meant that CIA bought most of the titanium for the planes from Soviets, using a number of coverup companies.
- most of the existing titanium processing technologies have been developed while producing the Blackbird. For instance, initially 80% of the delivered titanium was rejected due to metallurgical contamination, and the regular drills used for rivet holes proved useless after roughly 17 drillings.
- SR-71 is probably the only plane with constantly engaged afterburners. It’s the afterburners that create the “Mach diamonds” effect the Blackbird is famous for.
- Blackbirds have scored over 3,500 missions, surveying 260,000 square kilometers of Earth surface per hour. No less than 4,000 missiles is estimated to be launched against the Blackbirds – but not a single missile was able to catch up with the plane.
- while the plane itself uses early stealth technology for a fairly low radar signature, the hot air it leaves behind is well visible on radars.
- controlling a plane whose turning radius is about as big as an average country required a special navigation system: the astro-inertial navigation system, which required alignment before each flight and which contained data on 56 stars which it could track through a circular window on top of the fuselage behind the cabin.
- being qualified to fly a SR-71 was on the very top of what any USAF pilot could achieve. The Blackbird program put many severe requirements on the pilots, including, among others, being married. A total of 500 pilots were qualified. Only one person was ever killed in a Blackbird – Jim Zwayer, a flight-test specialist from Lockheed.
- upon landing, the pilots and the crew members need to wait for the plane to cool off before even disembarking.
- there is a Polish side to the Blackbird: the delta wing and the V-tail it’s using are both inventions of Polish sciencists: Kazimierz Siemienowicz and Jerzy Rudlicki respectively.
As for the model itself, I wanted it to look well and to be mounted on top of a control mast, somewhat in the style of the famous 8485 Control Center II set. The scale was limited by the engines’ radius, because I wanted to use perfectly round pieces rather than just approximate the round shape. As a result, the space inside the model was actually very limited despite its impressive overall size, and the silhouette looks best from above rather than from side. The look was completed by a large number of stickers that I have basically redrawn from a 1/72 scale Revell’s model, including pieces of black paper put over windshields to approximate the look of the cabin – not a pretty solution, but the only one that allowed to fit the minifigs inside.
The model was built around a simple Technic frame running through all the central hull. The frame was reinforced around the model’s center of gravity, where a mounting point for the control mast was located. Since there are no wing-shaped tiles by LEGO, only regular plates, I decided to build the winds sideways to make them smooth. That resulted in all leading edges being a whole 1 stud thick, but it allowed to model the plane’s silhouette reasonably well, and to include bricks with grille to recreate the corrugated “wing skin”. Each wing consisted of two parts with the engine in the middle, and the whole wing was attached to the hull at 5 points. I have put a lot of effort into making the model structurally solid despite its size and thin surfaces, so most connections used Technic pins, and some used axles.
Two axles were used to drive the engine cones by a PF Medium motor located in the middle of the hull, just in front of the mast’s mounting point. I have experimented with cones being retracted and expanded just like in the real plane, but the resulting mechanism was simply too large. There was also a single PF LED inside each engine, facing backwards and illuminating trans-orange antenna inside the engine nozzle. Two micromotors were installed behind the mounting point, to control the elevons. As a matter of fact, only part of the elevons was motorized – the parts between the hull and the engines, but not the parts on the outer wings. It was possible to motorize them too, but it would make any engine illumination impossible and it would make the outer wings much weaker structurally. It was also very likely that the micromotors would be unable to move elevons that large.
The small scale has prevented me from installing any sort of a landing gear, and I have toyed with the idea of adding the navigation lights, but decided that it would look stupid on a spy plane. Thus most of the functions was controlled and realized outside the actual model.
The control mast – from which the model could be quickly detached – was fairly simple, with a motorized turntable on the bottom and a sort of a cradle on the top, allowing it to rotate and to tilt the model forward/backward or left/right. Due to the model’s limited inner space I was unable to fit the center of tilting within its center of gravity – instead, it was located a little below it. That meant that the model’s center of gravity shifted while tilting, putting a lot of stress on the mast.
A “control set” could be connected or disconnected from the mast. It consisted of a joystick, a throttle and a subtractor. The joystick relied on the PF switches to provide a 3-axis control, and it also had two LEDs functioning as throttle indicators on top. It should be noted that there was no self-centering function in the joystick – instead, it was simply made symmetrical so as to stay balanced. The throttle simply used the speed dial on a LEGO rechargeable battery to provide a proportional control for the engine cones rotation and the engine nozzles illumination. The subtractor – a small studless variant described in my book – was used to move the switches controlling the micromotors, and thus to control the elevons. Thanks to it, both elevons moved in the same direction when the model tilted forward/backward, and in opposite directions when the model tilted sideways.
It was my goal not to overload the model with functions, because I didn’t want my first attempt in an entirely new area to be overdone, and I think I succeeded in that. I have learnt a lot while working on the Blackbird, and that was a goal too, as I’m planning a number of aircraft models to follow. It is unlikely that the model could include many more functions if it was bigger – but it’s very likely that it would experience structural problems caused by its size. This leads me to believe that I was able to find a reasonable balance between size, function and look in this model.