Mark Langford's KR2S

Mark Langford's Homebuilt Airplane and Online Builder's Manual

Updated May 2023

I've been guilty of not updating this particular URL over the years, but I have continually updated and created many more "chapters" of the KR story, all of which are listed below. Most are in excruciating detail, such as Corvair and VW engine rebuilds, and the refurb of Jim Faughn's KR2.

As of May 2023, I'm in the process of rebuilding the 3100cc Corvair engine with a Sport Performance Aviation "Gen2" billet crankshaft with front bearing, which I'll install on the plane Joe Horton built, N357CJ. I bought Joe's plane in October of 2021, as he was finishing up the "Dr. Dean" composite-skinned KR2S, and needed the hangar space for final assembly.

If you don't see anything else on this site, please check out my Cloud and Sunset photos, made possible by having my own magic carpet and time machine!

After 1130 hours, KR2S N56ML is sidelined for the moment, after suffering a broken crankshaft during takeoff at my father's farm (see for more about that). Damage could have been much worse, but both wings had minor damage, one gear leg was broken, and the lower cowling and engine mount were damaged. I was completely was a pretty decent landing, for a heavily terraced field!

Obviously that would take a while to repair, and I was wondering what I was going to fly in the meantime. After hearing of my incident, Steve Bennett (of Great Plains Aircraft) called offering up Jim Faughn's gorgeous KR2 N891JF. That sounded like fun, and it would be interesting and informative to fly a KR2 while I repaired N56ML, so I bought it. But rebuilding the engine, updating the instruments, and bringing the rest of the VW-powered KR2 up to my standards turned into a lot more work and time than I expected! I now have over 900 hours on it, and it certainly scratches the itch. I retired in 2020 from my engineering job of 31 years,and after dealing with the highest priorities on my To-Do list, I'm nearing the point of tackling the job of getting the KR2S back in the air again.

Originally I'd planned to build a new more improved KR2S, and had bought most of materials needed to do exactly that. But then as the years passed I started looking the plane over better and decided it was still 90% good, and really wasn't that far from being flyable again. One of the things I've learned by flying the KR2 is what a great flying plane N56ML was, and repairing it would be far more expedient than building another plane! Other than a panel redo and cleaner wiring job, there are few things I'd do differently, except that I'm a lot more experienced and skilled at building composite airplanes now. I may even paint it this time!

This is my version of the KR2S. Well, I guess it's not really a KR2S has been modified in almost every conceivable way, with only the basic fuselage shape retained. I'm using different airfoils for all flight surfaces, different flap and aileron planforms to increase control effectiveness, redesigned control system, Dragonfly canopy, lots of aerodynamic details for maximum efficiency, and an engine that's almost twice as powerful as the plans call for. It's far from complete, but I've started flying it anyway! This plane will be an experimental test bed for even more improvements to the design, including tufting and wing tip optimization.

  • Empty weight: 760 pounds
  • Gross weight: 1200 pounds
  • Fuel capacity: 16 gallons
  • Top speed: 191 mph TAS (true airspeed) with 3100cc Corvair engine and Sensenich 54x54 prop (turning almost 4000 rpm), 184 mph TAS with Sensenich 54x58 (turning only 3400 rpm, and burning less fuel).
  • Fuel consumption: I get 42 mpg while flying at 160 mph TAS at 10,000' running "lean of peak", which is how I always fly after takeoff.
  • Stall speed: 57 mph with split flaps deployed, 62 mph "clean"
  • Glide ratio: 11.8:1 engine at idle or engine stopped (almost the same number)at about 80 mph, averaged from 10,000' to 2,000'.
  • Propeller: currently a wooden Sensenich 54 x 58. I've tested at least 10 different props, and this one gives me the best speed and economy with a reasonably low engine speed.
  • More Performance data (as testing continues)

    Since I've finished my plane, I've undergone a bit of a transformation from crazy airplane builder to real pilot and aircraft owner. One year I put over 45,000 miles on my airplane (that's twice around the earth), yet my car only saw 6000 miles. I now use the airplane as my personal time machine...turning long, monotonous trips into a pure pleasure, both going and returning. I can fly my plane and get somewhere at least 3.5x faster than driving, and I'm not a time waster when it comes to driving either! My airplane typically gets about 40 miles per gallon at my usual "economy cruise speed" of 160 mph at 9500' or 10,500', far better than my Volkswagen GTI or my wifes's Audi A4. If I'm not in a hurry, I can get 51 mpg if I slow down to 143 mph TAS. I burn 93 octane auto fuel (same as the cars), so clearly flying is cheaper than driving, and I don't have to stop and buy lunch!

    In the last few years I've flown to Wisconsin, central Florida, South Carolina, West Virginia, northern Illinois, northwestern Iowa, and everywhere in between. I'm planning a trip out west to see the desert one of these days. I am so eaten up with flying that I basically don't do anything else...sort of like a meth addict. My basement shop is a mess, I never watch the news anymore, I haven't washed my car in months, and I can't even find time to buy new underwear or socks! But I do manage to keep several 5 gallon cans of 93 octane fuel in the hangar (I wouldn't want to run out), my flight bag in the trunk of the car, and the key to the plane with me at all times, just in case.

    And it's obvious to those who've seen my plane that actually making it look nice (or anything short of embarrassing) is way down on my list of priorities. I'm flying the crap out of this thing, enjoying every nanosecond of it, and I don't see any relief in sight. On a recent afternoon after work I was considering going flying (despite having flown to South Carolina and back the day before) but thought I'd try to hang around and visit with the family a little, when my wife says "why are you not out's GORGEOUS out there!" This worries me a little, because I don't think life is supposed to be this good. Next time you see me, I'll probably be the guy that can't find the time to shave...

    Details of construction are at the links below, in order of construction. Photos improve as you go down through the list. The early ones were in the nineties on film, scanned on the technology of the day...

  • Opinions, recommendations, and other biased information

  • Fuselage
  • Horizontal stabilizer/elevator
  • Header fuel tank/forward deck
  • New tankless forward deck
  • Canopy frame
  • Aft deck
  • Spars
  • Stub Wings
  • Wing Tanks
  • Wing Root Fillets
  • Outboard Wings
  • Vertical stabilizer/rudder
  • Rudder Pedals
  • Instrument Panel
  • Antennas and Strobes
  • Landing Gear and Alignment
  • Composite Seat
  • Type 4 VW engine
  • Miscellaneous stuff (there are a lot of gems in here!)
  • Big Bore Corvair engine-There's a lot of stuff here!
  • Engine mount and some weight details
  • Corvair engine cowling
  • Fairings for fuel vent and transponder antenna
  • NACA duct cowling exits
  • MAC trim tab installation
  • Dual Stick assembly (and earlier single stick)
  • Bodywork
  • Electrical System
  • Fuel System
  • Air/fuel ratio sensor and indicator installation
  • Carb heat and airbox
  • Cooling air plenums
  • First engine runs
  • Airspeed Indicator calibration
  • First flights, and several others of some significance
  • Performance numbers from testing (ongoing)
  • My hangar and hangar door
  • Detonation on takeoff
  • Corvair engine annual condition inpsection
  • XM Weather installation
  • New 3100cc Corvair engine
  • Weight and balance update
  • Fiberglass spinner
  • Cloud and sunset photos
  • Dynavibe prop balancer
  • Front Bearing 3100cc current incarnation of my 3100cc engine
  • Leaning and detonation article for William Wynne's 2009 Corvair Flight Manual
  • Wing tip extension and 8 gallon wing tank construction
  • crankshafts - what you need to know about crankshafts used in aircraft engines. This is getting old!
  • Current KR2 refurb project, N891JF.

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    At the point that I started flying it, I had over 5300 hours invested in actual construction over a 12 year period, mainly because of all the changes I've made, and my habit of making every part three times! As of August 2011, I have almost 1100 hours on the plane, but have done little more in the area of construction or finish work. Maybe I'll get around to that in the summer of 2010.

    Here's daughter Claire (when barely 11 years old) doing a better job of flying the plane than I can! This was her first flight, and as you can see, she is concentrating on maintaining compass heading and altitude, and was doing a great job of it.

    Below are a few old updates that I should probably delete, but the photos might be interesting. I used to make a point of posting an update every month or so, but now I'm just out flying...

    updated March 5, 2005 (See
    Carb heat and airbox.

    The Project Update - as of October 30, 2004

    I've spent the last few days peeling the Spray Lat coating off the canopy so I could see how to taxi. It was not easy, and I learned a few secrets, which we'll get to in a minute.

    Once I could see through the canopy, I couldn't resist the urge to taxi up the street. I live on a steep hill, and I've been dying to know if I could climb it in the plane. It was a piece of cake, at part throttle even! The neighbors came out to watch the spectacle. Obviously, I don't have the canopy latches installed yet. I left the cowling off because the engine cools a lot better that way, thanks to the intake plenums. Even on this short jaunt, I learned a few things about controlability. Number one on the list is to adjust the toe brakes so I don't have to pick my heels up to apply them. My brakes will hold the plane even with full throttle. I even practiced "levitating" the tail, which I could get up at less than full throttle. This thing is really going to jump into the sky!

    The secret to removing the plastic Spray Lat coating (and how to avoid the problem to start with) is shown at the bottom of my canopy construction page.

    The Project Update - as of September 1, 2004 Today my plane was officially blessed by the FAA's DAR (designated airworthiness representative) as being ready to fly! It's not really quite ready, but legally IT IS! Now it's just the little stuff. Most recently I've permanently mounted the rudder and tail wheel control cables, and am currently sanding the wings for the final time before primer. I expect to be flying in December, 2004...

    The Project Update - as of August 21, 2004

    I've completed and ground-tested my "totally redundant fuel/ignition system". I have two completely separate fuel systems, with each circuit having separate tank pickup, fuel filter, 6 psi Facet pump (each fed by different electrical circuits), and checkvalve, and ending in a tee that leads 12" to the carburetor (with fuel pressure sensor inline). The tee is right between the check valves, so any leak in one system is isolated from the other. I figure the grand total weight penalty is about three pounds. All fittings and valves, filters, hoses, etc are Earls, and the carburetor is an Ellison EFS-3A that runs great! Airfilter box in the photo and hardware is temporary, not "flight hardware".

    The electrical system is pretty much classic William Wynne dual point/condenser, except each coil is powered by a separate battery. Both fuel and ignition systems are independent of the rest of the electrical system, and are toggled by a DPDT (double pole, double throw) heavy duty MS quality switch. One flip of the switch swaps out the entire ignition system (including battery, but excepting MSD coil switcher, coil wire, and spark plugs and wire) AND the entire fuel system (except carburetor), all the way to the fuel tank. I can't think of any better way to concentrate on "flying the plane" if something goes wrong. If flipping that switch doesn't fix it, you might as well pick out a landing spot! Flipping that switch happens without any change in fuel pressure, rpm, or any other clue that both systems were just replaced. I was bragging to my wife how I was the only guy I knew of that'd ever done this and she replied with a smile "Is that good?" I should add that WW thinks it's pretty cool too. You can check it out at the electrical page and the fuel system page.

    I'm installing seatbelts at the moment, and on to the carb heat box next. It's pretty cool to be able to roll this baby out and fire it up any time I want to. My DAR is on notice, and all paperwork has been submitted, but I don't see any way I'm going to be able to fly it to the KR Gathering in September. I still have rudder installation, canopy latches, carb heat, spinner, aileron cables, wheel alignment, etc. .

    I've also updated the John Deere dynamo wiring page.

    The Project Update - as of June 12, 2004 is the first engine runs for the Corvair engine, and a new hairdo for me!

    The Project Update - as of June 8, 2004 is the completion (almost) of the instrument panel. Almost everything is hooked up and working, and engine start is coming soon!

    The Project Update - as of May 14, 2004

    The engine is almost ready to go, with only plug wires, throttle cable, oil cooler shroud, and a few CHT and EGT wires left to run. Right now I'm in the middle of building the oil cooler shroud. In this photo you can see the oil filter and adapter with Earl's thermostat mounted to the firewall.

    The Project Update - as of April 14, 2004

    Oscar's been pestering me to do some kind of real update, so here it goes. I really took about 6 weeks off from the plane to learn how to paint again. I painted the bottom of the plane but it wasn't quite as shiny as I'd wanted, so I thought I'd sign up for a local vocation school's auto body class. The big bonus is they have a new $56,000 paint booth, and the teacher is downright evangelical about teaching you how to paint! One of the requirements is you need a project, and I'd been planning on painting my '87 2-liter 16 valve Scirocco someday anyway (it had faded to pink), so I painted it. The funny thing is that when I went to buy the paint, it was the exact same color as I'd already painted the bottom of the plane!

    Well, you can see from the above photo that it came out as nice as I could have hoped for (it helps to start with a straight car, rather than a wavy handmade airplane), so that mission's now accomplished, and I'm back on the plane with a vengeance. I've fallen in love with the "beater car" all over again though!

    I've also gotten in 25 takeoffs and landings in a friend's Champ, so I'm getting ready to fly for real. I bought a Lightspeed headset for the occasion (hows that for a clash of technologies), and I love it already.

    Other stuff I've been spending time on is the wiring of the EIS (Engine Information System) and stuff like coils, fuel pumps, and even dipstick installation. There seems to be no end to it. At least right now I can switch it on and all kinds of stuff lights up, the radio works, just about everything's ready to go except I need to fab the spark plug wires and hook up the starter to the switch. I also need an oil cooler duct (the cooler is mounted, as well as the rest of the oiling system). I've rebuilt the Weber 40 DCOE carb and the tank is full.

    I've said it every week for two months now, but I'm very close to firing this thing up!!!!

    The Project Update - as of Feb 8, 2004 is that I'm running wires, hooking up the ignition system, and routing the oil lines. I'm getting ready to run this thing in the next few weeks! I guess now I'll have to start an electrical system page, coming soon.

    The Project Update - as of November 6, 2003 , is the new cooling air plenum page.

    The Project Update - as of August 24, 2003 , is that I shot a coat of DuPont Ultimate2K urethane primer at the whole thing. See details at the new bodywork page.

    Update as of June 1, 2003 the engine is installed for the final time (I hope). Work continues, and details will follow...

    Update as of May 26, 2003 is the completion of the dual stick design and construction .

    The Update - as of March 23, 2003 is the alignment of the main landing gear (about half way down the page).

    The as of January 5, 2003 is the completion of MAC trim tab installation .

    The update for December 12, 2002 is the construction of the NACA duct cowling exits , and also an update to Stub wing fillets , which now details the bottom wing fillets.

    Most of what I've been doing is little stuff like fairing in the transponder antenna and fuel vent, and closing out the bottoms of the stub wing fillets. Those exhaust pipes will be shortened and probably replaced with small diameter mufflers. All I need to do to the bottom is finish up around the tailwheel spring, micro and sand the stub fillets, make the gear leg fairings, and shoot a coat of paint on it! Then I'll flip it over and mount the engine for the last time. I'm at the point where there are a million little things to do, so even if I only have a spare hour, I can always find something to do.

    Terry Bailey welded up this exhaust system for me. Although I like to do such stuff myself, I'm beginning to get into the "I just want to fly the thing" mode, so I was happy to let him lend a hand. The workmanship is outstanding, and since these babies are stainless steel they'll last forever!

    Project Update - as of May 26, 2002 My engine is running! I took my engine down to William Wynne's Corvair College and used his test stand and advice to break in my engine.

    The project update as of May 6, 2002 is an improvement in the rear starter setup for my CorvAircraft engine.

    as of Feb 17, 2002 is the matter of optimizing Corvair rocker arm geometry

    The project update for January 27, 2002 is the beginnings of the Corvair intake manifold.

    The update for November 24, 2001 was the Corvair engine cowling. It's coming along nicely!.

    The project update for June 15, 2001 is the Corvair engine mount , which has progressed from prototype to final product.

    The April, 2001 update is my Corvair flexplate adapter/alternator pulley.

    The February update is my Corvair engine trial assembly. It should be particularly interesting to those going with the 3100cc big bore Corvair conversion.

    Project update - as of Jan 10, 2001. This month's update is my Corvair engine DISassembly and Corvair engine ASSembly. This thing is even easier the build than a VW!

    The November 2000 update consists of my Corvair rear starter setup, where I managed to knock about 3" off of what's been done before (IF you're brave enough to dump the fuel pump and distributor in favor of electric pump and electronic ignition).

    Project Update - as of September 10, 2000 Wow! What a difference two quarts of primer makes! This is only 3 coats, so all the body work isn't quite covered, and I'll apply two more coats tonight anyway. At least now that it's all the same color I can easily see the high and low spots. And it's starting to look a lot like an airplane. This is 10 hours worth of painting with a roller (that's the way the manufacturer recommends). That's not as easy as it sounds. It took 4 hours to roll on 28 ounces of Smooth Prime. Pot life is 8 hours. I guess I'll have to add a "body work" page now...

    Project Update - as of June 25, 2000

    Despite my tough schedule at work, I have managed to do a little Corvair engine work. Some details are on my Corvair page, but I'm just getting started. All the parts are bought, the machine work (boring out from 2700cc to 3100cc) is done, and I'm just about ready to assemble the engine. I really plan to finish up the engine over the winter though. I hope to get the airframe finished, sanded, and maybe even painted, except for forward of the firewall, while the weather is still warm. That won't include wheel pants either, I'll bet. Then next spring all I'll have to do is make a cowling, paint it, and fly! Yeah, right!

    I finally got my circuit breaker/switches in and mounted them, along with the EIS (Engine Information System). That big blank space is for some kind of huge color state of the art GPS, whatever I can afford at the time that my 40 hours are flown off. I don't figure I'll need a GPS to fly around the local area.

    Project Update - as of February 6, 2000. Since I was about to mount the firewall, I torqued and marked all the nuts and bolts and made final adjustments in the rudder pedal area. Of course since my forward deck is removable, it's not THAT much trouble to work on the rudder pedals, but it is a LITTLE more trouble with the firewall mounted.

    I wanted to check my composite seat height and see if my front deck had changed shape after sitting on the table for two years, so I mounted the front deck and canopy. They can be removed together, and installed in a matter of a few minutes (four bolts and two piano hinge pins). It's all I can do to keep my kids out of there. They get a real kick out of lowering the canopy and making airplane noises.

    Project Update - December 5, 1999 See Outboard Wings for details on construction of the outer wings, ailerons, and flaps., and controls, which are already constructed at this point

    Update as of Oct 11, 1999. Well, it's starting to look a lot like an airplane. I put the aft deck back on for a little while so it would make me feel like I actually had an airplane under construction. It's fastened on with hinge pins, and only takes a minute to take off or put on.

    I needed to flip the plane to finish "glassing" the bottom of the passenger wing, so I whipped up a flip-o-matic out of scrap plywood and 2x4's. Sloppy, yes, but it worked great.

    I'm comin' to join ya, Troy! This is Troy Petteway's C-85 powered 230 mph KR2.

    This is a 2D side view of the KR as I envisioned it eleven years ago when I started the project.

    Here's what it looked like ten years later...

    Mark Langford, ML "at"

    Return to my other website, with links to a hundred other KRs, at

    Project Update)