Web: www.poorboyaviation.com E-Mail: hartungj@srt.com
General flying Description April 2011 PG-7
Statistics: We try to avoid giving you hard numbers for performance, hard
numbers are elusive because of the many variables such as temperature, humidity,
engine power rating and condition, propeller efficiency, how much enclosure is
on the plane etc. You will find the Poorboy flies well and is comparable to
other Ultralights of similar power. In general if you are looking at a couple
of different planes spec’s you can count on this not being much different. We
have a video available that may help you to determine the planes flying
character, (see *Video* on this web sit). The Poorboy was designed with a
24.5ft. wingspan (12 ft. std. spars), wing tip choices can add to wingspan a
bit as you choose.
The PB-1 prototype with a 200 lb. pilot, 503dc engine, and droop tips, stalls
at 26 to 27 mph., cruse 55 to 60 easily, full power level flight may exceeding
VNE., this also exceeds legal top speed of 63 mph for an Ultralight aircraft.
This 503DC power is desirable for takeoff performance but should not use full
power in normal level flight. The 35 hp Cuyuna PB-1 stays in the speed range
better and flies very well, 35 to 50 hp air cooled engines are recommended.
The ailerons on the prototype appear to be a flap and aileron as separate
controls because of the abrupt angle change at the strut position, the control
surfaces are one piece, they are not separate and are activated by one control
arm p/wing, the angle difference is not as abrupt in the PB-U. The five degree
angle change exists on all of the PoorBoy models and is built into the aileron
to produce washout on an otherwise flat rectangular wing. The aileron angle
change is an attempt to slow the wing in stall with good stall warning.
The wing will fully stall if you aggravate the approach to stall and spins are
not approved or recommended, nor are rolls (this is an “ultralight” aircraft).
The aircraft can be built without the split aileron 5 degree angle difference
but we have not researched that option and recommend that you use the 5 degree
split. The aileron angle split is intended to keep the aircraft in the
Ultralight flight envelope by lowering stall and limiting the upper speed
range of the wing.
Stability: Pitch--- The PoorBoy is pitch stable as measured by pulling the
stick back and releasing, the aircraft will cycle a couple of times and go to
trim setting in about 2 minutes (hands off testing), trim set at slightly nose
up (climb) at 75% power. Pitch trim is set by the horizontal stabilizer leading
edge ground adjustable position.
Yaw---- is stable in one cycle, push rudder and release, plane will return to
no input skid because of P-Factor forces unless there is trim correction applied
or build in.
Roll is less stable and is effected by P-Factor and the amount of dihedral,
the aircraft has been flown at 5 degrees and 2 degrees of dihedral. The plans
call for 4 degrees dihedral, a person may choose another setting but note that
as dihedral increases roll stability increases, as dihedral decreases the
aircraft is more roll sensitive and less stable but more responsive. The
aircraft is generally not roll stable unless there are trim tabs or trim spring
tension applied and the pilot needs to fly the airplane, this is true of
co-ordination of turns also (stick and rudder). The aircraft has good roll
authority and is not touchy.
Trim adjustments are required with power setting changes, elevator trim forces
will be effected as well as aileron and rudder to a lesser degree, this is true
of Ultralights and General Aviation aircraft.
April 2011 PG-8
General flying character will remain consistent as long as you observe proper
center of gravity (CG) of 29-percent of the wing cord (based on 60” cord, about
17.5” from LE). Slight changes from this will not put the aircraft at risk + or
– ˝”, but you will notice changes on controls and trim settings. There are
limits to CG balancing points, too far forward and you wouldn’t have enough
control authority to keep the nose up, too far aft and the aircraft could become
uncontrollable and “twitchy” (stall recovery in particular). FAA has a Pilot’s
Weight and Balance Handbook (EA-AC91-23A) that is very good (you need this when
you do the center of gravity calculations and to confirm CG figures). The
aircraft is a 30 percent CG balance point design theory.
www.faa.gov/library/manuals/ aircraft/media/FAA-H-8083-1A.pdf
Take off: Apply power and bring the tail up about 1 ft. from the ground, let
speed build a bit and slowly bring the tail back to the ground angle of attack,
the plane will lift off. After liftoff level off and let your speed build a bit
and adjust your climb angle. Once airborne you can adjust the power setting,
you should not fly at full throttle unless you were in takeoff or hard climb.
Cruise speed 45 to 65 (63mph limit) is comfortable, under 35 the aircraft is
getting sloppy and your close to stall speeds.
Instrumentation: A Halls airspeed indicator and a piece of string (yaw
string), you can fly just fine with just this much as long as your engine is in
tune (carburetor main jet), and its fun. Optional instruments put the flying
instrument panel between your feet (altimeter, airspeed, rate of climb, slip
indicator ball), and the engine instruments at your left hand side panel
(cylinder head temp, exhaust gas temp, RPM, hour meter, ignition switch etc.),
you may want a compass somewhere. The degree of instrumentation is your
personal choice.
Landing: Your approach speed should be "at least" 10 to 15mph above stall, if
you trained in a General Aviation aircraft remember that ultralights have less
weight and will slow quickly without power or a steep descent angle.
Ultralights are more sensitive to wind gradient changes during descent on breezy
days (the wind will decrease as you loose altitude close to the ground and the
air will appear to fall out from under you upon flair), this is true if there
are ground obstructions to air flow such as trees or buildings. Engine out
condition should bring the pilot into approach to landing attitude immediately
by putting the nose down and maintaining at least 15 mph speed above stall
condition until flair for touch-down (standard procedure).
Note that a 35hp PB-1 is flying with some variation in performance but the overall
character is the same.