Sequoia Aircraft in conjunction with aeronautical engineer David B. Thurston performed extensive and detailed systems modernization and re-engineering on the Falco. The kits, and the elaborate list of prefabricated parts, pre-configured systems, instructions, builder newsletters and other product support for this aircraft are exemplary among homebuilt designs. Sequoia Aircraft further distinguishes itself by offering their builders a thorough 40 page Falco Flight Test Guide and a very sophisticated performance analysis software program called Benchmark.

This wood aircraft is constructed using the adhesives Penacolite G-1131 (also used on the Bellanca's and French Robin aircraft) and/or the more popular Aerolite glue, originally used on the deHavilland Mosquito and later on production Falcos.

Larry Black offered his 160 hp Falco N572AB for this APR. His careful flight test preparations and enthusiasm were a major contribution to this report. Five test flights were made in all. The first two were subjective flying qualities evaluations, followed by 2 flights conducting zero thrust glides. The final flight determined the stall speeds. It should be noted that the climb rates demonstrated in these tests were performed at weights above those more commonly used for this aircraft and were made at a higher speed than the nominal best rate of climb speed. The zero thrust glide results were incomplete due to some technical difficulties and are therefore omitted here.

The equipment list for N572AB included a Terra Tri-Nav C, dual Terra TX-720 comms and dual Terra TN 200 navs, an Apollo GPS 2001 NMS, a David Clark Isocom, a Terra TM-23 marker beacon receiver, a Davtron A301C digital OAT, a single channel Alcor EGT, 3 point belt/harnesses, electric flaps and landing gear, and a central throttle quadrant.

This aircraft exhibited a high level of refinement and completeness with systems that were all matured. The only modifications recommended by the CAFE Board were the addition of a restrictor orifice in the manifold pressure sensing connector, the addition of a recirculating fuel line from the engine driven pump to the fuel tank, an adjustment of the spinner bulkhead runout, and a linkage revision to the control stick to increase the stick forces.

In the performance tests, several different power settings were evaluated at approximately 10,000' density altitude as well as 8,000' and 6,000' density altitudes. The takeoff distance was that observed as the ground roll from brake release using a short field takeoff technique.

The CAFE Foundation was very impressed with the show quality work- manship and finish of this aircraft.

FLYING QUALITIES REPORT

BY C.J. STEPHENS - CAFE Foundation Test Pilot

This was the first opportunity for the CAFE Foundation to conduct an APR on an all wood aircraft. From the moment of its arrival in Santa Rosa for testing, Falco N572AB's show-stopping qualities were obvious. Everything from the beautiful, taut fabric covering of the control surfaces to the gorgeous white finish was done with exact precision. Larry Black, the owner/builder, was justifiably proud of his work.

After a brief flight with the owner to go over the Falco's idiosyncrasies and cover special procedures, I performed the first of two subjective evaluation flights. Otis Holt (5'10", 150 lbs.) occupied the right seat for this flight, which was conducted at gross weight with the C.G. located 25% aft of the forward limit. I am 6' and 170 lbs.

Keeping an open mind is important when evaluating an unfamiliar airplane. All rumors and prejudged ideas must be ignored; instead it is just what you see and what you think about your actual experience that are important. Even before the actual preflight where specific items are inspected it is helpful to walk around the plane taking in all of its lines, design features and quality of construction. Then it is time to go to work and learn facts and specifics.

All of the documentation and checklists that were presented with the airplane were excellent. A through checklist was laminated in plastic and was very useful. To someone in an unfamiliar airplane a quality checklist greatly increases the comfort level of operation.

Upon sitting in the cockpit we discovered the seats to be too high, putting our heads too close to the bubble canopy. This was quickly remedied by substituting 1" thick cushions for the installed 2.5" cushions. The problem thus solved, adequate headroom now existed for each of us. It should be noted that the headroom would be less than ideal for someone over 6' tall. On the second flight (with C.G. 25% forward of the aft limit), Cris Hawkins (6'3", 190 lbs.) occupied the right seat and noted occasionally touching his head on the canopy. It did appear that room existed within the fuselage for lower seats to be installed with adequate cushions. The seats were on rails, adjusting easily fore and aft, allowing for varying leg length of different pilots.

The large bubble canopy also slid very easily on its rails and seemed to be an excellent installation. The locking mechanism was simple to understand and made a positive lock once in position. The instrument shroud and cowl as viewed from the cockpit sloped away nicely so as not to be a visual obstruction on the ground or in the air.

The cockpit had a conventional layout. The three power levers were of the center mounted, color coded, lever type. Instrumentation was the standard array with enough gyro instruments for comfortable instrument flying. The markings on the airspeed indicator were not to my liking, with large and small tick marks every 5 kts., but with numerical references only every 50 kts. (i.e. 50, 100, 150). I found this took some getting used to because of the interpolation required. In time, I think a pilot would adapt to the sparseness of the numbers. The right side rudder pedals did not have brakes. Though not a problem, it would be a consideration should the aircraft be used for instruction from the right seat. The control stick was long and curved, which was a little unusual. The grip was in the natural position but the stick curved away to the floor mount to provide clearance for the seat and wing spar.

The fuel system, having a 20 gallon header tank well forward of the C.G., and another 20 gallon aft of the luggage area, required some active management on the part of the pilot. Depending on the aircraft's loading, it would be fairly easy to violate the allowable C.G. range by depleting most of the fuel in one tank before switching to the other. Normal procedure with N572AB is to take off and climb on the header tank, then switch back and forth as needed to maintain balance.

THE SUBJECTIVE FLIGHTS

After priming the engine with the boost pump, it sprang to life with the enthusiasm of an Olympic athlete. Taxiing using the effective and positive steering during ground maneuvering was easy and natural. The toe brakes were very effective.

All of the ground operations seemed straight forward and proceeded in a logical fashion in accordance with the written checklist. Flaps were set to 15 degrees for takeoff as recommended. A very nice and well marked elevator trim wheel was set to the recommended position. The magnetos checked out O.K. with the only note being that the panel-mounted analog tachometer read 70-80 rpm below the accurate digital tachometer. A dual function volt/amp meter had been installed and worked well, providing an accurate indication of the condition of the electrical system.

Control during takeoff was positive and I had no difficulty tracking the Falco straight down the runway center line. Rotation was smooth and easily controllable to establish the 110 kts. climb speed. As was recommended, the flaps were retracted first. However, upon doing so the airplane settled noticeably unless elevator was used to compensate. This probably explains the recommendation to retract the flaps first. Should runway contact be made in such a situation, it would then simply be a touch down and not a prop strike.

Landing gear retraction employs an electric motor driving a worm gear and flex cable arrangement. Once the up cycle was complete, it was recommended that the manual drive handle be engaged and given the last turn or two to firmly close the gear doors. This was a fairly cumbersome operation to perform just as the climb was being established and traffic pattern demands were high.

Field of view over the nose and in all directions during the climb was excellent. The outside air vent provided plenty of fresh air for cooling. The heater was excellent for cabin heat as well as providing two very nice outlets for windshield defog.

STATIC LONGITUDINAL STABILITY

I used a hand held stick force gauge to take measurements throughout the entire level airspeed envelope. The results appear in the accompanying table. It was necessary to use a slight descent to obtain the data at 160 kts. Note the flattening (then reversal) of stick force as the speed reached the slow end of the test. Each time the speed was reduced to below 100 knots an exhaust smell was observed in the cockpit.

DYNAMIC STABILITY

Pitch doublets were induced with stick inputs to examine natural dynamic stability. The data was recorded using both the stick fixed and stick free method. The Falco, like all of the other homebuilt aircraft tested thus far by the CAFE Foundation, exhibited a very high level of dynamic stability, with excellent damping and no overshoots.

TRIM

There were no provisions to trim the Falco for aileron or rudder in flight. However, there was a very adequate elevator trim system that provided sufficient control throughout the entire normal airspeed envelope.

MANEUVERING STABILITY

The maneuvering stability graph shows how the stick force compares to other airplanes analyzed by the CAFE Foundation. As you can see, the stick forces are very light. Although this makes the Falco a joy to fly, care must be taken to use very light elevator input force to prevent excessive G-loads during maneuvering flight.

The Wittman Tailwind W10 is the only other aircraft thus far measured with similarly light stick forces.

SPIRAL STABILITY

This was examined by setting up a level trimmed turn, releasing the controls, and recording the banking tendencies exhibited. During all attempts in both directions neutral spiral stability was experienced. The Falco requires such light control forces to change bank angle that the stick break-out force itself influenced roll response during the spiral stability check. By that I mean that just the friction within the system was enough to influence which way the plane would bank when the controls were released.

ROLL RATES

Roll rates and stick forces were recorded with full deflection at both 91 kts. and 120 kts. The stick force increased noticeably from 4 lbs. to 10 lbs. as the IAS increased from 91kts. to 120 kts. The feed-back force was the same amount in both directions.

STALLS

The stall characteristics demonstrated by the Falco were comfortable but quick, requiring a light touch on the part of the pilot. On each stall the right wing would drop slightly as the plane abruptly stalled and the nose dropped. A mild aerodynamic buffet could be felt through the control stick just prior to the stall itself. An electronic warning was installed and would activate at 8 kts. prior to stall during clean stalls but did not activate at all during the landing configuration stalls. Stall recoveries were positive and immediate upon the relaxing of the back stick force and reducing the angle of attack. The airspeed indicator in N572AB's panel showed that the stalls to occur at the following IAS:

    Fwd C.G., clean config:     65 kts.
    Aft C.G., clean config:     66 kts.
    Aft C.G.,  landing config:  60 kts.

These should be compared to the values measured by the CAFE Barograph in the table of CAFE Measured Performance. (Altitude loss during stall peaked at 78 feet per second with a worst case demonstrated total loss of 448 feet prior to recovery in stalls performed by the owner with the CAFE barograph monitoring altitude.)

TRAFFIC PATTERN/LANDINGS

After a very busy hour and a half spent rigorously working through the flight test protocol, the return flight to the field finally offered a chance to relax, enjoy, and become one with the aircraft. By the time we reached the traffic pattern area, I had acquired a high comfort level with the Falco.

Field of view was excellent during the return and descent. The low wing and easy maneuvering made it exceptionally easy to see and avoid traffic while maneuvering for pattern entry. The Falco's clean aerodynamics allowed the plane to carry good speed throughout the descent.

Again during the gear extension it was recommended that the hand crank be operated to ensure snug full extension. This is quite distracting during a time when the cockpit work load is the highest at a busy airport. One noticeable feature of the design is a rapid airspeed bleed-off when the gear and initial landing flaps are extended. As a consequence, the pilot is manually snugging the landing gear down just as the airspeed is dissipating more rapidly than expected. I feel this would require special emphasis in training and rigid discipline to prevent difficulties, especially for a low-time pilot. A significant power increase is required when transitioning from level clean flight to landing configuration to overcome the added drag of flaps and gear.

All other events in the traffic pattern seemed to be well within the normal expectations. The approach and flare are very straightforward. I chose to carry a little power until just prior to touch down and found it very easy to consistently make nice landings. The landing gear has a firm feel when it touches down and it tracks very straight down the runway.

CONCLUSIONS