Gimpy FSX Pilot Report – IRIS Simulations Pro Series Christen Eagle

Few aircraft in history are as iconic and easily recognizable as the Christen Eagle.  The distinctive multi-color paint scheme; the history of The Eagles aerobatic team; the excellent combination of performance, value and economy; and the success of the Eagle as a kitplane have all combined to make this an airplane sought after by both real world and simulation pilots alike, worldwide.

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IRIS Simulations, an Australian developer of add-on aircraft for the Microsoft Flight Simulator platform took the excellent Long Island Classics Christen Eagle which was among the first and remains one of the very best truly aerobatic aircraft for Flight Simulator, and has upped the ante significantly.  IRIS has developed a number of great aircraft including some fantastic military aircraft (F-15E Mudhen, F-14 Tomcat and F-20 Tigershark to name a few) for FSX as well as earlier versions.  For their Christen Eagle, IRIS has modeled both the classic 4-cylinder 2-seat Eagle II, as well as the airshow special 6-cylinder single seat Eagle I.

The cockpits of both versions are very well modeled.  The primary variation from reality (in most cases) is the inclusion of the basic FSX autopilot.  As with the real-world Eagle, instruments and controls are located in both the rear (pilot) and forward (passenger) cockpits.  The pilot has all engine controls (throttle, prop, mix, starter/mags, fuel selector and the famous Christen wobble pump), also present are battery and alternator switches, avionics master and the radios – for the simulated version there is also as previously mentioned an autopilot, which is a welcome addition on long cross countries to virtual competitions or airshows, as well as the virtual $100 hamburger.  Whenever I get around to buying or building an Eagle, I am leaning heavily towards a modern lightweight EFIS, nearly all of which now sport autopilot control capabilities.

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IRIS has included a number of attractive liveries paying homage to existing aircraft as well as a few great fantasy schemes, and offers a nice paint kit, for owners who want to develop their own paint scheme.  As an aside, I used to own a small aviation graphics shop years ago and one of the real-world Eagle schemes duplicated in the IRIS package is actually one that my good friend and graphics designer extraordinaire Dave ‘Frito’ Chiarelli designed for a client we had (N540ET).


Basic Flight Characteristics

The real-world Christen Eagle is, essentially, a civilized Pitts S-2A.  Frank Christensen had tried to buy Pitts, and when he was unable to purchase the company he set out to design and build a competition biplane that could also be used as a multi-purpose sportplane.

To that end, Christensen took the basic shape and aerodynamics of Curtis Pitts’ little hotrod, and he stretched it a little here and there, but the two major differences are the incredible canopy and cockpit layout, and the addition of a wider track spring steel main gear where the Pitts sported narrow track bungee mains.

These two differences are what truly set both the real-world, and the simulated Eagle apart.  Ground handling of the Eagle, both in the real-world and in the sim is simply superior to the Pitts (compared say to Alabeo’s Pitts S-2S, or any of a number of Pitts- S-2A/B/C offerings).  It tracks straighter, and is much easier to land given the spring steel gear absorbs less than perfect landings far better than the bungee sprung affair of the venerable Pitts.

For basic straight and level flight, the Eagle is, again in the real-world and in the sim, not particularly well suited.  The airplane has such little dihedral in the lower wing that it is not in any practical sense self-correcting.  For a competition aerobat you want an airplane that does exactly what you tell it to do, and that is what the Eagle does – leave in a little roll, and it will happily continue to roll.  If you are distracted for a moment or two setting up the autopilot, or messing with the radios/GPS in the beautiful 3D cockpit, the Eagle will continue doing the last thing you told it to – so choose carefully.  This is not to say the plane is unstable, just that it once again is a very faithful reproduction of the real thing.

Another nice feature of the IRIS Christen Eagle II is you can set it up for a passenger, and it will place a female passenger in the front seat.  The plane’s performance is accurately effected, but it is a nice touch that is not necessary but kind of fun.

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In the pattern it is a rather fun machine.  The great Eagle paint scheme is a real treat to see when you look out over a wing to time your turn downwind.  Once again, like the real thing, the Eagle is a very honest airplane, so it must be flown consciously in the pattern.  Power-off descent rates can be pretty impressive, so I typically fly a simple Navy style dogleg or descending 180 from about 45 degrees off the approach end of the runway with power to maintain about 90 mph.  When I am in a hurry or feeling adventurous I might start my turn abeam the numbers with power off and in a constant slip.  The airplane simply does what you tell it to, the powerful flight controls and great power will allow you to recover from almost anything shy of a cross-controlled departure at low altitude.

Takeoff and landing are very fun, and reasonably well simulated here.  The airplane responds correctly to engine torque, and will not be controllable if you mash in full power without using your feet.  This is one area I was very interested in with respect to improving my own real-world flying.  As an amputee (below-knee, right leg) I was concerned about being able to handle taildraggers, and as a result did not log my first tailwheel takeoff/landing until I had over 350 hours in about 30 different make/model aircraft.  The use of a good rudder pedal setup in FSX (I use the Saitek Pro Rudder Pedals) is key for any transfer of muscle-memory with respect to tailwheels, and also for aerobatics.

Click here to read my overview of using FSX for Aerobatics Training, to include hardware and software recommendations and direct links.

Typical takeoff is standard tailwheel fare, line up, hold brakes and apply power, release the brakes with the stick back to keep some weight on the tailwheel.  I usually pick the tail up after 4 or 5 seconds, really before the airspeed comes alive.  Keeping the nose down, accelerate to about 75-80 mph and fly it off or let it fly itself off, climb out at 100.

Returning to the field, I usually use 1000 feet AGL, fly downwind to 45 degrees off the approach end, pull the power back to 15-17″, and settle in to a nice descending 180 dogleg, rolling out just shy of the fence at about 80-90 mph.  I prefer weheel landings in the real-world, so as I do with the A2A P-51D I wheel land the Eagle almost all the time.  Sometimes if I get a little slow the typical Pitts/Eagle 3-point landing is unavoidable, but the plane soaks up less than perfect landings fairly well.

Once on the ground, forward visibility, just as in the real-world, is pretty limited and this requires S-turns while taxiing, or open the canopy and tilt your head out (possible if you use TrackIR or FaceTrackNoIR).  Taxiing is fairly accurate from my recollection of my real-world Eagle flight – the real airplane can be built with either a free-castor or semi-steerable tailwheel.  The IRIS version sports a common FSX tailwheel that provides steering to a point then breaks free, so steer carefully.

As in the real-world, it is very satisfying to taxi up to your favorite virtual airport cafe, and shut the engine down while swinging the tail around, something tricycle gear planes simply cannot do.

Advanced Flight Characteristics

And now for the fun stuff…  The IRIS Eagle II, like its’ real-world counterpart, absolutely excels at aerobatics.  You can read about my real-world Eagle II flight here, but I just want to say it is a real treat to find a simulation that flies very much like the real thing, and the IRIS Christen Eagle really does fly very much like the real thing.

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For simple aerobatics like rolls and loops, the Eagle is a fine machine.  Roll rate is very good, and although I haven’t timed it I think at some speeds it is actually a little better than the real-world Eagle.  The sim, as is typically the case, carries more roll inertia than real-world aircraft do, and this makes it difficult for example to use a lot of roll rate in hesitation rolls because precision stops become difficult.  I haven’t added it up but I would estimate I have well over 200 hours in the IRIS Eagle II and I still struggle with roll timing unless I only use half or less roll rate.

The area where the original Long Island Classics (LIC) Eagle, and the IRIS Eagle earn their stripes as the best FSX aerobatic models is in auto-rotational and gyroscopic manueuvers.  The IRIS Eagle performs truly auto-rotational snap rolls, and spins with extreme accuracy and predictability.  For clarification purposes, a spin is an auto-rotational event, by stalling the airplane in an uncoordinated fashion, one wing lifts, the other does not, and the result is the airplane enters an auto-rotational mode along a vertical line, like a Maple seed ‘helicopter leaf’.  Continuing then, a snap-roll is basically a spin along the direction of flight.  By yawing the plane and pulling sharply on the stick, you stall the wings, and the plane spins about the longitudinal axis.  The LIC and IRIS Eagles snap and spin just like real planes, and require the same level of timing and practice – this is a massive development in simulation, and provides for great knowledge and muscle-memory transfer in my opinion.

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As with the auto-rotational capabilities discussed above, another area where the LIC and IRIS Eagle set themselves apart from most other simulations is in the faithful simulation of gyroscopic effects and maneuvers.  In aerobatics, gyroscopic maneuvers are those where the engine torque and propellor gyroscopic forces act on the aircraft, usually in low or zero airspeed conditions.  With the correct control inputs, the IRIS Eagle is capable of performing textbook Lomcevaks (forward tumbles) and Torque Rolls, again putting them in a class nearly by themselves, but with a level of fidelity that is truly unique as of this writing.  Few things in the real-world or in simulation are as satisfying as hitting a Lomcevak on a 45 degree upline, getting a solid 2-3 tumbles, and then recovering on-heading, save perhaps for nailing a Torque Roll on the top of a 1700 foot vertical line, hanging on the prop, and slowly descending backwards through your own smoke trail.

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Just like the real-world planes, timing and technique are huge inputs into the quality of any advanced aerobatic figure, but with a total cost of $30 for the add-on plane, and no fuel, oil or maintenance expense, the IRIS Eagle simply cannot be beat in terms of bang for the buck, while also providing transferrable experience.


In summary, the IRIS Simulations Pro Series Christen Eagle package is a fantastic add-on that provides a depth of realism that few aircraft I have found are able to match.  The excellent systems and graphical simulation of say the Carenado PA-46T JetProp Malibu represent a high-level of fidelity, and the IRIS Eagle package reaches the same level of execution, but in terms of performance and handling while also providing a high-quality graphic.

Whether you are only interested in a fun flyer, or are looking to fly hard and compete within the online multi-player virtual airshow and aerobatic competition world (for virtual competition aerobatics I will shamelessly plug my involvement with the FSX Air Sports Association (FASA) – and, the IRIS Christen Eagle package is a must-have.  It faithfully reproduces an airplane that set new standards for performance and appearance among kitplanes that is both a challenge as well as a joy to fly.



About acrogimp

Pilot (real world, simulator and RC), Engineer, Blogger - all around wing nut! Also, below-knee amputee, snow skier, motorcyclist. Husband, Father, Son, Brother, Uncle.
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One Response to Gimpy FSX Pilot Report – IRIS Simulations Pro Series Christen Eagle

  1. Pingback: Aerobatics group lands at Sebring Regional Airport | Sykose

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