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Peregrin XS-302

Chris Christiansenís first design

By Patrick Panzera, EAA 555743, PPanzera@eaa.org

This article first appeared in the December 2004 issue of Contact! Magazine. Some of the information is now dated, and some of it has been updated for Experimenter. But the article is interesting, educational, and ties in with the accompanying Savor article in this issue. At the time of writing, the plane was a few hundred hours from flying. Since then it has flown, but as Chris put it, the Rotax never hooked up like planned. A Jabiru replaced it, then another Rotax, but it seems that the power-to-weight ratio was never there. A high-power engine is still needed; Chris jokingly suggested an all-aluminum V-6, but with the advances in engine technology, especially with regard to direct injection, he may not be too far off. Currently, the project is on hold.

Chris
We first met Chris at COPPERSTATE (CS) 2003. We’ve since caught up with him again at COPPERSTATE 2004 and were able to update some of our photos. Photos shot at CS-2003 show the Peregrin in grey primer. Photos where the plane is in white were shot at CS-2004.

Chris Christiansen is an avid flyer with extensive time in ultralights and hang gliders. The Peregrin (no “e” after “n”) project is an attempt at a bit of notoriety, as Chris is bitten by the bug to set and break records. He feels that his best chance to make it into the record books is by way of the experimental powered flight category, specifically in class C-1.a/0 (661 pounds gross takeoff weight or less). Chris has no formal education after high school, but he’s certainly not letting that stop him. At the time of our interview, this project occupied 100 percent of Chris’s time.

Chris is 24 years old, but his appearance could easily lead one to believe he’s much younger. Although he gets confused for a high schooler from time to time, his slight frame has allowed him to design a plane that’s very small and yet still easy for him to enter and exit; his size and weight will go a long way in aiding performance. The average sized person, even by FAA standards, doesn’t stand a chance of piloting this miniature, high performance airplane.

The Peregrin is essentially a mixture of a lot of different aircraft which have caught Chris’s eye in the past. He’s taken the construction methods used in plans-built composite Rutan-type aircraft to create solid foam core wings. He also employs moldless construction techniques to create the highly complex compound curves which give the little airplane its sleek “Lancair” appearance. The flying surfaces, as well as the retractable landing gear, are reminiscent of the early Lancair line of kit aircraft. Every control surface will be 100 percent balanced with the exception of the flaps, which will be locked when they are in the up position to hedge against the possible chance of flutter.
 
Chris studied Martin Hollmann’s books on aircraft design, which he found especially helpful in selecting aspect ratios as well as airfoil choices. A NACA 63-215 airfoil was selected for the wing of the Peregrin. This airfoil is used in some very fast aircraft like the AviaBellanca Skyrocket II, Mooney M20 series (at the root), KIS TR-1, and the ViperJet. Chris figured that it would be a good choice for his plane, as his goal is to keep the plane as fast as possible without being overly unstable. He’s looking for pitch stability, good roll control, and minimal adverse yaw.
 
I asked Chris about his timeline. He projects that, with enough money, he could easily have it up in the air in as short as three months, and that’s the main reason for publishing this article. Although we don’t usually publish articles about projects in the works, Chris needs our help. When I met Chris at COPPERSTATE 2003, I asked him point-blank why he spent money on a display if he wasn’t selling plans or kits. His answer was simple: He was looking for sponsorship. I think that Chris has a really good chance at breaking multiple records for both speed and time to climb, and he has a really good start at it; I figured I’d put this article together and see what comes of it. Hopefully we can help Chris meet his goals. If you are interested in sponsoring Chris or know someone who might be interested, by all means contact him!

The Engine
The engine is a run-of-the-mill, liquid cooled, 670 cc, 2-cylinder, 2-stroke, 100 hp (at 6,500 rpm) Rotax snowmobile engine. It’s hard to beat the power-to-weight ratio of these little alternative engines, which makes it a good choice for this small plane. All the initial flights will be with this configuration, but Chris does have the option of turbocharging it for the altitude time to climb records. Six pounds of boost (Rotax claims) is good for up to 150 hp for about 5 minutes. But is there room for a turbo? Yes.

Engine
The engine photos don’t show a propeller speed reduction unit (PSRU aka redux), but Chris will be running a belted redux, with a ratio of 2.09:1. You can see a little glimpse of it in the first photo in this series.

The turbo is slated to go in the section behind the engine compartment, where the expansion chamber currently resides. The turbo (when installed) will be of the “blow through” variety, feeding the carbs with compressed air.
 
The Propeller
Chris is making a wood composite, two-blade, fixed pitch propeller, with future plans to go with a cockpit controllable propeller if the need should arise. At present, a ground adjustable, three-blade composite propeller is installed and will be used for initial flight tests.
 
The Landing Gear
The gear structure, as with the dampening system, (as far as the elastomeric “donuts” are concerned) as well as the trailing link, are all similar to early Lancair, but the gear retraction system is totally Chris’s design. A manual cable pulls everything up. The system also unlocks with a cable and typical gas struts (used for trunk lids and rear hatches on cars) to push everything back down. A spring-loaded, over-the-center position lock will hold everything in place.

Landing gear

All the metal parts were MIG welded (metal inert gas) by Chris and were heat-treated afterwards. “Welding is self-taught, which is why it’s not the prettiest thing you’ve ever seen,” Chris told us, but to me, the welds look just fine. Each time Chris did any welding, he would usually weld scrap material (as a test piece) of the same diameter and thickness as the finished piece, which he would later test to destruction.

The Exhaust System
The exhaust system is typical for a two-stroke; it has a very large tuned pipe (expansion chamber), and keeping things close in around the engine (keeping frontal area to a minimum) Chris was able to run the pipe back through the engine firewall, into the fuselage, to an area between the firewall and a secondary firewall, right in front of his feet. Doing this has allowed Chris to make an augmented exhaust system, with the exhaust dumping out of the radiator ducting plenum, drawing radiator cooling air out with it. This also helps with drag reduction, as there is only one exit for both radiator cooling and exhaust. There will be a muffler in the system when it’s complete.

Belly
The cooling air inlets straddle the nose wheel well. In the photos above, the nose gear door is not installed.

Cooling Air / Radiator
Chris is using dual NACA inlets to feed his radiator, cool the exhaust pipe chamber, and to augment exhaust. The inlet air is routed around the nosewheel. The shape of the compartment which houses the radiator is somewhat venturi-like, and Chris hopes that this will aid in cooling while on the ground.

The inlet air coming in from the two NACA inlets on the underside of the nose section, as well as the two little ones (one each side of the cowl), all exit through a small opening between the two main gear wheel wells.

Rear view
The small opening just above the nose wheel is the outlet for the cooling air and exhaust.

After the incoming air does its chore, it’s exited out the rear and blended with the slipstream in a manner which should not add much drag.

Since the exhaust system (expansion chamber and potentially a future turbocharger) is contained inside the fuselage, part of the inlet air is designed to help cool the compartment. With the exhaust system reaching 500 degrees, there’s real concern.

The Fuel System
An 8-gallon header tank up front and a 4-gallon reserve tank in back makes up the 12 total gallons of fuel Chris will have onboard. The 4-gallon reserve will probably never be used; it’s just there in the event of the occasional cross country jump. When throttled back and properly leaned, Chris should have a range of about 400-450 miles, at about 250 mph. The reserve tank is plumbed to the header via an electric pump. Filling the reserve tank is done by way of the return line back from the header tank. It’s plumbed with a return line in the event that Chris ever goes with an electronic fuel system.
 
With the fuel tanks not being located on or near the CG, there is a slight shift of CG with fuel consumption. Halfway through consuming the front tank, the plan is to switch to the rear if fuel is available. Chris can’t let the front tank run out all the way especially if he has baggage in the rear. Twenty pounds of baggage and 4 gallons of fuel up-front, with a 150-pound pilot, is right at the aft limit. Should Chris find himself there, he’ll need to transfer fuel forward as soon as he can.
 
A sight tube is used for reading the level of the header tank, and at the moment, a sight tube is also used to read the level of the rear tank. Chris hasn’t decided yet just how he’ll read the tube behind him, but I’m sure a mirror would do the trick. Chris told me that he really has no need to check it while in flight because there’s no need to do anything but dump it all to the front. It’s not like he’ll be running off of it or transferring only part of it. Chris is utilizing an electric Facet automotive pump for fuel delivery, as well as a mechanical pump that comes with the Rotax engine.

Starter
At the time of this writing, the Peregrin had no starter. Chris has had trouble finding an electric starter that will work for his Rotax, as all the right angle drives he can find have the starter motor clocked at either the 1 o’clock or 11 o’clock position. Chris needs a 12 o’clock drive (straight up and down) due to the narrow cross section of his engine compartment. “No company has been accommodating or willing to modify their starters for us; they just tell us to change our airframe,” Chris told us. “That’s not going to be happening, so now it’s starterless.”

The Wings
The wings are solid “blue” foam core construction, assembled around a built-up composite box spar. The first thing that caught my eye about the wing is how it connected to the fuselage, and just how reminiscent of high performance gliders it is. The center section is bonded to the fuselage. The outer few feet are attached by way of the wing spar (which extends beyond the root by 2-3 feet) sliding into a rectangular socket in the center section. The spars do not overlap, but rather they miss one another by about 18 inches, tying into the main carry-through. Access to the spar attachments is through the wheel wells. Five bolts is all it takes to disconnect all the aileron controls and both wings.

Spar
Photo courtesy Chris Christiansen

The spar is built of box construction, made up of two C sections. It’s built primarily of E fiberglass with carbon rods in the corners. In Chris’s opinion, this makes for a lighter spar and about twice the strength (tensile and compression) as using unidirectional glass laid flat. “If we had used unidirectional tape for the spar caps, it would have added 20 pounds, which would have been terrible,” Chris told us. The spar lay-up uses vacuum bagged, room temperature cure epoxy.

Spar
The wing spar lay-up being vacuum bagged. Photo courtesy Chris Christiansen

There has been no load testing yet; it’s all based on numbers right now and Chris plans to fly it before he does any load testing. (Chris does plan to load test it before he pulls any real G’s.) The calculations show that plus or minus 6 G’s, ultimate of 9 to 9.

The plane is small enough that it might have been built with a one-piece wing, permanently attached, but Chris estimates that making the wings removable, as he has, maybe added ten pounds to the empty weight. Ten pounds added to the overall weight isn’t much, but on the aircraft that only weighs 300 pounds to begin with, it’s somewhat substantial. Chris feels that for ease of maintenance and ground transportation, he had to do it. “The wings detach for trailering 7-1/2 foot width,” Chris told us. “We can just put it in a trailer and take it somewhere and roll it back home, and we don’t have to fly it and abuse the aircraft. Or if it breaks down at an airport, we can just drive there and pick it up and bring it back home to work on it instead of bringing everything there.” 

The wing tips are an elliptical shape which taper back to a nice little “shark” tip. As with any wing tip design, there’s always the debate on whether it works or not. Some are designed for drag reduction, some to increase effective span, and some just have no thought put into them at all. Aesthetically, these wings are a winner, no argument. Theoretically, there is a drag reduction with the 60-degree swept angle.

The wing root fillet would probably be one of Chris’s favorite parts on the plane, just for pure sexiness. “It’s got a nice curve to it,” Chris said, “but it may be aerodynamically wrong. The back curve is probably a little too high; it should be drafted a little lower. If we run into some problems there we are going to have to chop it up and make it a little straighter and less curvy.”

The flaps have four positions: 0, 15, 30, and 45 degrees. Chris will probably change this as he feels there just might be too much flap angle, and 0, 10, 20, and 30 degrees seems much more appropriate to him at this point.

Canopy

Canopy
Chris made his own canopy. The only obvious flaw which would give away the fact that it’s homemade is in an area that’s perfect for a canopy vent, which Chris plans to install. The canopy has a four-pin latch system which slides through the canopy rails, interconnecting to each. When locked from the outside, Chris has to walk around the plane to latch both sides--a little inconvenient but overall very simple.

Controls
The controls consist of a single side stick on the right, throttle and mixture on the left, with rudder pedals and toe-operated brake cylinders. Chris is still undecided about which brake system to use. He’ll probably change from the nylon wheels, which he currently has installed, to new aluminum wheels and opt to use dual puck disc brakes.

Panel

Instrument Panel
Instrumentation will consist of a digital engine management system (Grand Rapids EIS) stripped down for ultralight use. It consists of just the basics: tachometer, water temp, OAT, highest (of the two) CHT, altimeter, VSI, and highest (of the two) EGT.

In addition to the digital screen on the EIS, the Peregrin's panel will host a whiskey compass, analog G meter and ASI, as well as an iPAQ (electronic pocket organizer or PDA) to run the Anywhere Map GPS software.

The Airframe
The compound curves of the plane were created by carving the actual contour out of foam blocks and massaging the shape until it was perfect. Chris then “sealed” the foam with cellophane packing tape. Carbon cloth then covered the “plug” which was wetted out with epoxy resin. This produced a single layer “shell,” which when cured, was pulled from the plug and placed upside down in a cradle.

Fuselage
Photo courtesy Chris Christiansen

The carbon can hold its shape pretty well on its own, but the cradle keeps it dimensionally stable when adding the foam to the inside. Once the foam was in place, a layer of carbon (over the foam) completed the “sandwich.”

Centerfold

We hope to write more about this plane and builder as things progress and records are set and broken. We wish Chris well with all his future endeavors.

Logo
Chris’s motto, painted on the side of the plane.

Type

Fixed wing, single place

Empty Weight              

300-325 lbs

Useful Load                    

235 lbs

Gross Weight

550 lbs

Normal Fuel Load

8 gallons

Full Fuel Load 

12 gallons

Engine, Maximum Power

100 hp @ 6,500 rpm

Propeller

2-blade fixed pitch

Wing Data

Area

26 sq ft

Span

15.3 ft

M.A.C.

24 in

Airfoil

NACA 63-215

Aspect Ratio

6.75:1

Taper Ratio

1.67:1

Twist

2 º washout

Dihedral

5 º

Horizontal Tail Data

Area

6.75 sq ft

Span

5 ft

Root Chord

18 in

Tip Chord

12 in

Airfoil

NACA 63-009

Vertical Tail Area

4.75 sq ft

Landing Gear

Retractable tri-gear

Performance, Race Weight @ Sea Level

Stall Speed, with flaps

60-70 mph

Maximum speed

270+ mph

Max cruise speed

230-250 mph

Rate of climb

3,000 fpm

Range

450+ nm

 

 
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