Iris Simulation's Pro Series Christen Eagle for FSX

By Bill Stack
14 November 2009


Screen shots by IRIS Simulations

The Christen Eagle is an aerobatic biplane available in kit form for homebuilding. It was designed by Frank Christen in the early 1970s to combine professional design with factory parts. Its gross weight is 1,578 pounds (716 kilograms). Powered by a Lycoming 200 horsepower engine, its maximum speed is 184 miles per hour (296 kilometers per hour). One model holds one pilot, and another model holds one pilot and one passenger.

In response to a request from the FSX Blue Eagles, an online aerobatic team, IRIS Simulations has released an FSX upgrade from FS2004 models of the Christen Eagle I and II.

IRIS Simulations is a family-owned business based in Melbourne, Australia. David and Karen Brice run the business out of their home "out of a love of aircraft and the community," David explains. "Karen does all our marketing and keeps the business running, and I simply put, build the planes and keep the guys in the team on their toes." The enterprise has a team of of about 20 people including 3D modelers, texture artists, and other key development people. IRIS has also made military aircraft such as the F-4 Phantom, the F-14 Tomcat, the F-15 Eagle, and the T-6 Texan.

PURCHASE FEATURES

Instant download from the Pilot Shop

YES

Installation program

YES

License key required

YES

End user license agreement (EULA) required

YES

Uninstall program included

NO

Manual included

YES

Major Features

IRIS Simulations touts the following among many features of its Christen Eagles:

Custom soundpack including new supersonic prop tip effects,
All new 3D gauges designed from the Christen blueprints.
Two visual models contracted by Frank Christen and polished by IRIS for full FSX functionality.
A superb flight model for the Eagle I and Eagle II aircraft.
A wide variety of paint schemes.

Three of the thirteen paint schemes are the single-seat Eagle I, and the remaining ten are the double-seat Eagle II.

This aircraft package is easily downloaded in a few minutes from the FlightSim Pilot Shop. A license key and an end user license agreement are required. The installation program extracts all needed files quickly and deposits them in the correct folder. The aircraft in its two models and 13 paint schemes appears in the aircraft-selection menu.

Aircraft Selection Menu
Aircraft Details Screen

Examples of Christen Eagle Paint Schemes

Screen Shots by Bill Stack

N75CE G-NUTA G-SMTH

Selected Christen Eagle Exteriors

Screen shots by Bill Stack

Visual Features

Rendering inside and outside this aircraft reflects appropriate attention to detail, accuracy, and display.

The basic aircraft and some of its paint schemes are accurate compared with pictures I found on the Internet.
All but the following four paint schemes are actual Christen Eagle skins, according to the developer: VH-DRB, VH-KAZ, VH-BUG, and G-HOST.
The level of detail inside and out is sufficient for a clear picture of the aircraft without diminishing frame rates.
Unable to find photos of real-world cockpits or instrument panels, I am unable to comment on the accuracy of IRIS Sims' cockpits. Based on the realism of the verifiable paint schemes, we can assume that IRIS Sim's cockpit, instruments, and controls are accurate.
Controls inside the cockpits move realistically, as do control surfaces outside the aircraft.
Frame rates are good. They ranged between 15 and 30 during my vigorous flight tests, and the simulator never hesitated or skipped.
Night effects are dark inside and out — there are no panel or exterior lights, there are no light switches, and the manual says nothing about lights. In response to my question, the developer said: "The Christen Eagle isn't certified for night time or IFR flight hence why no night lighting is available."

Cockpit	Engine Controls	Radios	Canopy Control
3D Virtual Cockpits
Screen shots by Bill Stack

Technical Features

Controls such as throttle, mixture, propeller are clickable.

Electrical switches (battery, alternator, etc.) are clickable.

The canopy opens and closes by clicking the Canopy lever on the right of the cockpit.

The GPS unit, which is available only in the 3D panel, is clickable to operate but not to enlarge.

There is no 2D panel. Some flight simmers say they never use them, but I believe 2D panels are often easier to read.

The radio stack is the only popup subpanel.

There are no popups for GPS, engine controls (throttles, mixture, propeller pitch) as is typical in most MSFS aircraft, users must zoom in on the 3D panel and pan left and right to read instruments and control labels. This is difficult to do while trying to keep this fast and nimble aircraft under control.

The kneeboard does not contain checklists or reference data. Users must refer to the 20-page manual for aircraft performance data and checklists, which is not as convenient as pulling down menus in the simulator.

The aircraft can take off with the canopy open, and the canopy can be opened during flight. This can't be realistic, as the wind would surely rip away the open canopy and its hardware. In response to my question, the developer said this would be fixed in an upcoming service pack.

IRIS also told me that it plans to provide some fixes in its Support Forums in mid November "to counter the damping issue that's causing some people to experience an overly bouncing aircraft!"

Single and Two-Person Versions

Screen shots by Bill Stack

Flight Modeling

Having never flown a real Christen Eagle, I have no clue about how it should perform. I tested this aircraft thoroughly, including high power, low power, steep climbs, barrel rolls, steep dives, and landings. It is very nimble and rolls with little effort. It also recovers easily from all control input — whether normal or excessive. Thus it seems to perform as would be expected of an aerobatic aircraft.

Keeping airspeed within safe zone (out of yellow) while doing dives and loops is one of this aircraft's innate challenges. Its powerful engine enables the aircraft to accelerate quickly and exceed safe speeds unless the pilot is watching closely. Since no abrupt maneuvers should be performed while the airspeed indicator needle is in the yellow caution zone, the pilot must be careful not to begin any maneuvers while the needle is in this zone and not to allow the aircraft to move into this zone while aerobatics are underway.
Ditto the RPM warning on the instrument panel. It cautions about continuous operations between 2,000 and 2,350 engine RPMs and above 2,600 engine RPMs during aerobatic flight. (In other words, try to stay between 2,350 and 2,600 during aerobatic flight.)
Pilots will benefit from knowing the terrain they are flying over. There are no navigation radios, and the GPS isn't very readable unless zoomed in.
Landing is another challenge. Visibility is blocked by the engine compartment, and there are no flaps to aid descent. Airspeed and altitude must be managed carefully, or the aircraft will land too fast, overshoot the touchdown area, or stall on approach.
Sim pilots had better know how to rely on instruments because of restricted outside views and lack of physical sensations during common and aerobatic maneuvers. Particular attention must be paid to the attitude indicator, airspeed indicator, vertical speed indicator, and RPM gauge.
Users are wise to thoroughly read the specifications and checklists in the manual because this is such an unusual aircraft.
I could not get this aircraft to do full loops. Instead of going over the top of the loop upside down, it rolls 180 degrees at the top of the loop and starts descending straight down. In response to my question, the developer said: "I've had no issues myself performing aerobatics. I would however be mindful of the weights prior to aerobatics. The aerobatic chart in the virtual cockpit crossbar will give ideal entry speeds for various maneuvers. Loops might be best achieved from a shallow dive." So I tried again, following guidance from the manual and the developer. Well, I still couldn't get it to do a full loop while adhering to specified airspeed and RPM parameters. Maybe this maneuver requires perseverance and practice in this aircraft.

Climbing	Turning	Barrel Rolling
Looping	Diving	Approaching for Landing
Christen Eagle in Flight
Screen shots by Bill Stack

Nice Features

A single-pilot version and a pilot/passenger version are offered. Both models represent real-world Christen Eagles. The passenger in the Eagle II versions can be inserted or removed by entering 110 pounds into the aircraft's payload through the Fuel and Payload menu.

The 20-page manual in Adobe format uses annotated screen shots to describe the cockpit and its instruments and controls. It also provides specifications, checklists, and several procedural recommendations.

This excellent manual is available through a clickable button that appears in the installation program when the installation is complete. But there are no other references to it afterward. I found it by searching the FSX folders, where I found a folder named "IRIS Pro Series," a subfolder named "Christen Eagle," and a secondary subfolder named "Manuals and References." This manual would be more useful to users if it were more easily accessible, expecially without kneeboard checklists and reference data.

The manual explains four flaws the developers acknowledge: The aircraft appears to float on grass or dirt surfaces, exhaust smoke appears from four feet ahead of the nose during engine startup, the pilot and passenger are not animated, and the pivot point may appear to float when opening and closing the canopy. Users are referred by this manual to an internet support forum for further information, but the forum requires registration to view its messages.

Sounds seem realistic. Having never seen or heard a real-world Christen Eagle, I have no idea what it sounds like, but these sounds seem appropriate for this type of aircraft. The developer says the sounds are based on a mixture of Christen Eagle sounds and other aerobatic aircraft he has accumulated during the years.

Several extras are available in the "Goodies" and "Paintkits & Art" folders, but there are no references to them anywhere — not in the manual or in the Internet product description. Users either stumble upon them as I did, or are tipped off as my readers are. They're automatically installed by the installation program into this folder: "C:\Program Files\Microsoft Games\Microsoft Flight Simulator X\IRIS Pro Series\Christen Eagle".

The developer responded to my inquires quickly, clearly, and courteously. This bodes well for users who need technical assistance or have suggestions or other comments.

Cockpit View
On the Ground
Aloft

Open-Canopy Views

Screen shots by Bill Stack

Cover Page
Panel Description
Checklist

Sample Pages From the Manual

Screen shots by Bill Stack

G-SKIN Exterior
G-SKIN Cockpit

Night Effects

Screen shots by Bill Stack

Screen Shots

My screen shots were made with FSX display settings on "default" because that's what I presume most flight simmers would be using and the developer does not recommend any special settings. I tested with the frame rate set on "30" and "unlimited" to see what rates were possible while flying this aircraft, and they were always within acceptable range.

Summary

This FSX aircraft is perfect for flight simmers who want unusual simulation experiences. Its greatest challenge is executing the aerobatic maneuvers while keeping the airspeed in the safe (green) zone. The manual is helpful in understanding the instruments and controls. Interior and exterior renderings are excellent. Details are sufficient for realism while not harming simulation performance. The lack of 2D panel and and subpanels and the total reliance on panning and zooming the 3D panel hinders the experience, however, because the aircraft is challenging enough to fly without having to operate the 3D cockpit at the same time. The developer seems willing to address user questions and requests and to upgrade the product as necessary. This product is a wonderful treat for flight simmers seeking something other than ordinary commercial or general-aviation flight.

Bill Stack

Learn More About Iris Simulations' Pro Series Christen Eagle

Bill Stack is author of several books about flight simulation, a regular author in flight-sim magazines, and a contributor to Flight Sim Com. His website is www.topskills.com

PURCHASE FEATURES
Instant download from the Pilot Shop	YES
Installation program	YES
License key required	YES
End user license agreement (EULA) required	YES
Uninstall program included	NO
Manual included	YES

Aircraft Selection Menu	Aircraft Details Screen
Examples of Christen Eagle Paint Schemes
Screen Shots by Bill Stack

N75CE	G-NUTA	G-SMTH
Selected Christen Eagle Exteriors
Screen shots by Bill Stack

Cockpit View	On the Ground	Aloft
Open-Canopy Views
Screen shots by Bill Stack

Cover Page	Panel Description	Checklist
Sample Pages From the Manual
Screen shots by Bill Stack

G-SKIN Exterior	G-SKIN Cockpit
Night Effects
Screen shots by Bill Stack