In 1958, Bob Bushby purchased the
rights for an all metal single-seat racer known as the "Midget Mustang". This
racer was a design originally built in 1948 by Dave Long, who was at that time chief
engineer at Piper Aircraft. Bob built his prototype version of the Midget, N15J, and
first flew it on September 9, 1959. Its performance and capability created a demand for a
two-place version and Bob designed the Mustang II between 1963 and 1965. He flew that
first Bushby Mustang II to EAA's 1966 Rockford Convention. The only parts it shared with
the Midget were the wing ribs and the spar web.
Since then, Bob's Mustang II evolved through a 125 hp Lycoming to a 160 hp O-320, fixed
tri-gear, with wood as well as constant speed props, and even a folding wing design. Bob's
awards include winning the August Raspet Memorial Award and the Stan Dzik Memorial Award
for Outstanding Design Contribution.
Over the years, builders have added retractable gear, tip tanks, wet leading edges and
engines of up to 210 hp.
The aircraft in this test is a representative example of the breed, being powered by an
O-320 Lycoming of 160 hp with a fixed-pitch wood prop. It belongs to Jim Lewis of Concord,
California, and it is currently for sale (contact Jim at 510/938-1646).
It was built by Charles H. Chervenka of Sunnyvale, California, being completed in 1985.
It was flown about 12 hours before being sold to Art Beer of Santa Rosa, California. Art
states that because this aircraft uses an engine mount which was originally intended for
the 180 hp Lycoming, this locates the existing O-320 engine 2" farther aft than
standard, and thus makes this aircraft slightly tail heavy.
Art painted the aircraft and made several changes and refinements to it. In 1989, he
sold the aircraft to Jim Lewis. Jim had the aircraft painted with the Mustang graphic, and
performed several modifications and improvements of his own, including a 70% reduction in
cowl exit area, a harmonic balancer/flywheel and nozzled exhaust pipes. These changes
produced about 11 mph more cruise speed, according to Jim and Art. Jim, who reports having
carefully measured before and after, attributes 7 mph more speed to the harmonic balancer.
Jim owns a foreign auto repair shop in Walnut Creek, California. He was trained as an
aircraft mechanic in his youth. Jim used the aircraft to practice aerobatics and has
performed loops, rolls, Immelmans, Cuban eights and hammerheads in the aircraft. He has
pulled 5 G's with 2 aboard and 1/2 fuel and has demonstrated the 230 mph redline IAS.
This Mustang has accumulated over 360 hours total time, and has 150 hours since top
overhaul of the engine.
For these CAFE performance tests, the magneto timing was set at 27 degrees BTDC, and a
"climb" Pacesetter wooden prop of 68 x 66 was used. A closed cowl outlet and
nozzled exhaust pipe outlets were other modifications on this aircraft.
Other Mustangs have found substantial drag reductions by smoothly enclosing the main
gear brake calipers inside the wheel pants, fairing the tailwheel, reducing the cowl inlet
size, sealing the spinner to cowl gap, adding wing root fillets, etc. This aircraft did
not have these changes, and may well have been capable of even higher speeds if they had
been used. A complete discussion of modifications for the Mustang II is available from
Kent Paser, 5672 W. Chestnut Ave., Littleton, CO 80123-6041 in his book, Speed With
Economy.
The performance flight test of this aircraft was abbreviated due to the severe floods
and persistent rain in Sonoma County during December and January this year. Because of
this, the usual zero thrust glide drag curve measurements and resulting data are not
included in this report. Some propeller leading edge rain damage occurred just prior to
the rate of climb run and the climb rate may have suffered somewhat as a result.
This aircraft did not have wing leading edge stall strips which are often used to
produce stick shake or buffeting as a stall warning. The lack of stall warning
demonstrated in N402C could probably be corrected by such strips.
Chris Tieman at Mustang Aeronautics has upgraded the kit for the Mustang II to include
new features such as pre-built wing center section, spars, engine mount, landing gear and
control hardware, hydro-formed ribs, bulkheads and many other ready to install items. The
completeness of the new kit offerings makes this design much more attuned to the
fast-build philosophy which now pervades the homebuilt movement.
INTRODUCTION
It was a pleasure to have the opportunity to fly, as test pilot, in this tried and
proven aircraft design. It seemed like an excellent candidate for a CAFE APR. Judging by
the enthusiasm exhibited by Jim Lewis, the owner, it was obvious that he had enjoyed his
association with this airplane.
The previous owner, Art Beer, was on hand to greet Jim when he arrived at the CAFE
hangar. It was at that time I realized I had flown this plane briefly several years
before.
We held the standard acceptance interview with the owner regarding the various
specifics about the plane's history, any modifications, restrictions or unusual
characteristics.
Meanwhile, the technicians of the CAFE Foundation prepared the plane for its first
flight, a subjective evaluation in which various features such as cockpit layout, ground
handling, servicing, field-of-view, inflight equipment, and flying qualities are evaluated
in detail.
The plane was defueled and its empty weight and CG were determined. A video camcorder
with a link to the aircraft intercom was installed to monitor my comments and the
instrument panel readouts. The CAFE Barograph was not installed on the flying qualities
flight so as not to alter the plane's characteristics.
ACCOMMODATIONS
N402C seemed to be built with a purpose in mind. It is a day/VFR fun, fast airplane. It
has nothing installed that is not required to meet that mission. There is no heater,
defog, or lighting system installed. Therefore, it is light, simple, and has very good
performance. The rollover bar, that also serves as the windshield canopy bow, is very
sturdy and would provide excellent protection to the occupants should the aircraft end
upside-down.
The standard canopy locking system consisted of a twist lock at the top center of the
canopy bow to keep the canopy from sliding aft on the rails. This was further modified
with three overcenter canopy latch mechanisms. These latches were located at top center
and one each behind the seat on either side on the canopy rail. These latches added to the
security of the canopy in flight but seemed difficult to operate and, in an emergency
situation, would very likely hamper egress from the cockpit.
FIRST FLIGHT IMPRESSIONS
I consider my first impressions of an airplane's flying qualities to be important to
the evaluation. After several flights a pilot will learn to accommodate an item that is
initially an irritant. By doing the subjective evaluation on my very first flight, more
can be discerned.
GROUND OPERATIONS
Ground handling of the plane was very nice. Its light weight allowed for easy pushing
and the tail could easily be picked up for maneuvering in tight spots. Moving the plane
backwards on the ground required the picking up of the tail, which was not difficult,
since it weighed about 40 pounds.
Start up was quick and easy, requiring only a few pumps of the throttle. The warmup and
ground operations were routine.
All pre-takeoff checks were accomplished routinely although no organized written
checklist was provided. The light weight of the wooden propeller was evident by the quick
acceleration following throttle movement.
Braking was effective for slowing and turning sharply in parking spots. The non-swivel
tailwheel was positive and very sensitive while taxiing. I felt it was too sensitive,
causing quick movement, and required constant attention to taxiing direction.
Tailwheeled airplanes traditionally have field of view restrictions on the ground,
however this one showed a good wide field of view over the nose while taxiing.
TAKEOFF AND CLIMB
Once cleared for takeoff the power responded quickly and acceleration was swift.
Directional control on takeoff was positive except that some oversensitivity of the
tailwheel was evident. Once the tailwheel lifted off, the directional control settled down
to being very nice. Pitch and roll controls were positive and precise, making it easy to
attain and hold the desired climb attitude.
Climbing at full throttle while indicating 120 mph showed an initial rate of climb of
2000 fpm indicated on the panel's VSI. The view over the nose during the climb was
adequate to see any obstacles. A transparent green plastic sun block had been installed
over the pilot's head for greater comfort on sunny days. With a little practice, the view
through this was sufficient to see other traffic.
In this Mustang II the oil temp consistently ran below 180 degrees. Even after
sustained periods of slow flight the temperature only came up to 185 degrees. No cowl
flaps are available, nor do they seem necessary. No climb cooling test was performed.
STATIC LONGITUDINAL STABILITY
Upon leveling off at 7,000' and 120 mph IAS, the first task was to explore the static
longitudinal stability. With the airplane trimmed to 120 mph a hand-held stick force gauge
was used to measure the elevator force required to hold level flight. Each airspeed, in 10
mph increments throughout the entire speed range, was evaluated by adding or reducing
power as necessary to alter the airspeed. The elevator trim remained unchanged throughout
this test. The greater the incremental force at each successive airspeed the greater the
static stability. Having flown a variety of other similar airplanes and previously
submitted reports on the RV-6A and the Tailwind, it is my opinion that the Mustang II has
one of the best stick force gradients for all-around flying. See Figure 1.
DYNAMIC STABILITY
Dynamic stability, short period, in both stick-fixed and stick-free modes were
explored. A sampling of all airspeeds across the entire operating range were tested in
both modes. The results were completely 'deadbeat', in that when pitch doublets were
induced and the stick was then let free, no pitch oscillations or overshoots resulted.
This is evidence of the ideal dynamic stability qualities with this design.
I was unable to fully trim the elevator to airspeeds below 110 mph IAS due to the
limited travel of the electric elevator trim system.
SPIRAL STABILITY
Normally my evaluation of spiral stability would be done at both 90 and 120 mph IAS,
however, due to the inability to fully trim the elevator to 90 mph I could only evaluate
its performance at 120 mph. After carefully trimming and stabilizing in a 30 degree bank
turn, the controls were released at which time I observed the banking tendencies. After
more than 40 seconds of continued turn with no change in the bank attitude, the test was
terminated. The Mustang II thus exhibited neutral spiral stability in both directions. A
feature such as this would be beneficial to a pilot during moments of inattention. The
Mustang II gives the feel of lightness on the controls, yet is not an airplane that you
have to watch constantly to keep it under control in bank. The airplane tends to stay in
the existing attitude unless control inputs cause it to change.
ROLL DUE TO YAW
Roll due to yaw, at Va and 1.5 Vso, was examined by inducing steady state yaw with the
rudder and observing the bank required to hold the airplane on a constant heading. The
results were similar at both airspeeds examined (90 and 120 mph). Half rudder deflection
required 8-10 degrees of bank to hold a constant heading. Full rudder deflection required
15 degrees of bank. The 90 mph test was repeated with full flaps extended. Here, only 5
degrees of bank with half rudder and 10 degrees with full rudder deflection were needed.
Another way to look at the roll due to yaw or dihedral merits of an airplane is to
observe the bank while inducing yaw with the rudder (hands off the ailerons). This plane
shows a strong and positive tendency for the bank to follow the yaw input. With rudder
alone, the bank could be controlled from 30 degrees of bank in one direction to 30 degrees
bank in the opposite direction. It was during these checks that I noticed that the
airplane exhibited a stronger than normal tendency to oscillate in yaw. I decided to
further investigate this during the Dutch roll check later in the flight.
ADVERSE YAW
An adverse yaw estimation was made by slowing to 80 mph and, using full aileron,
observing the hesitation of the heading at the onset of the turn. With the short wingspan
and quick roll it responded as anticipated with very little adverse yaw. Even the most
dramatic aileron inputs yielded only 5 degrees of heading change opposite to the roll
input.
ROLL PERFORMANCE
Roll rates were also measured at 120 mph through the use of a wire grid attached to the
instrument panel and a stop watch. The right to left roll rate was 72 degrees per second,
while the left to right rate was 66 degrees per second. Figure 2 compares the roll
performance of other aircraft we have tested.
DUTCH ROLL
Dutch roll was examined by inducing doublets in yaw, pitch, and roll. Upon release of
the controls the oscillation continued much longer than normal for an airplane that had
just exhibited such otherwise strong stability characteristics. Upon further exploration I
found that with rudder alone I could excite yaw oscillations that would continue for as
many as 15 overshoots. At no time was it severe enough to present any danger. It was just
that the directional stability was not as strong as it was in roll and pitch. The
oscillation could be easily controlled with the use of the rudder as a yaw damper. It
exhibited no Dutch roll tendencies.
STALLS
The stall sequence was very interesting to evaluate. At 1300 rpm, to approach the stall
slowly, the airspeed was reduced while looking for any signal of an impending stall. There
was no electronic stall warning system installed. In flaps up configuration, the stall
occurred abruptly with virtually no aerodynamic buffeting or warning. The nose just
crisply and abruptly pitched down with mild left wing drop. The recovery was instantaneous
with the release of the stick back-pressure. Several stalls were made with exactly the
same results each time. The 60 mph panel indication of stall was consistent but will be
checked for accuracy on later CAFE flights.
Flaps were extended for comparison of the landing stall characteristics with those of
the clean stall. It was difficult to fully extend the flaps to the third notch until the
airspeed was below 85 mph. The handle could be moved to the proper position but it would
not lock into the notch and stay extended. The stall with full flaps occurred at a panel
indication of 63 mph, 3 mph higher than with no flaps. The abrupt pitch down and left wing
drop were very similar to that of no flaps.
Since the higher airspeed puzzled me, I checked the stall speeds at all flap settings.
With two notches the stall was 61 mph and with one notch it was 60 mph. The quick recovery
and very predictable nature of the stall characteristics are pleasant and not a worrisome
thing at all. However, if one desired the buffeting stall warning of some of the
production aircraft, this plane would need some added devices to create such warning.
Without the barograph and other instrumentation installed, a maximum speed run was made
at 7,500' for later comparison with the instrumented flights. The maximum IAS was 178 mph
@ 2750 rpm.
MANEUVERING STABILITY
Figure 3 shows a graph of the maneuvering stability or stick force per G obtained. This
is a measure of how much tactile feedback is provided to the pilot relative to the wing
loadings being produced by the pilot's force on the stick. Comparison is made to the other
aircraft tested thus far and reveals that the Mustang II has a good level of stick
feedback relative to the others.
APPROACH AND LANDING
After more than an hour of very pleasant flying in an enjoyable airplane it was time to
return to see its landing qualities. With the nose down the speed would build quickly due
primarily to the clean aerodynamic exterior. With the excellent visibility and fine
maneuverability it was easy to manage the flight path in the traffic pattern. Downwind was
flown at 100 mph slowing to 90 mph on final, further reducing to 80 mph in the flare.
Keeping in mind the small value the flaps had in reducing the stall speed my first landing
was planned to use only the first notch of flaps; however, with the low drag that this
setting produced it was difficult to maintain the desired glideslope. Therefore, flaps
were reset to the third notch. The touchdown and landing were straightforward and
comfortable. A three point landing was made with only a small crosswind evident from the
wind sock. The still too-sensitive tailwheel gave plenty of authority to control the
direction during the roll out.
CONCLUSION
My final subjective flight is to determine the suitability of the plane
for the continuation of the CAFE APR. This seems like an excellent choice. One interesting
note is that this is our first test aircraft that was not "new". This airplane
has been owned by three EAA members, each adding their own touches, and it has been in
continuous use facing the rigors of life on the flight line. It is in excellent condition
and has been obviously well cared for by its owner, Jim Lewis.
