Flitzer Basics
Light Aircraft Association - Type Acceptance Sheet for the Flitzer Z-21
December 29, 2001
The Flitzer was developed from an early, personal requirement for an uncompromisingly 'vintage type' aeroplane, which would make no concessions to the constraints of powerplant or other anachronisms which would have arisen were the machine to be based on a pre-existing marque, from whatever country or time period, whose engine type is no longer available, or would be wildly expensive.
It had to be light, handy in manoeuvre, and simple to construct, using the minimum practical number of metal fittings on what is essentially an all-wood design. It had to have excellent short field performance, and be capable of operating out of very short, unprepared strips. It had to have a very good rate of climb, potentially for aerobatics, but also to provide terrain clearance out of confined areas. It had to be easily dismantled into handy-sized components, each of which had to be manageable, where possible by one person working unassisted.
It had to be quick enough so that it could make relatively long cross-country flights without being they're being too protracted, economic to operate, and with a good fuel endurance.
By using the ubiquitous VW 'Beetle' motor as the basic powerplant, the overall cost has been kept down, and ALL the above requirements have been fulfilled. Although the present propeller is holding the revolutions at 300 rpm below approved maximum of 3300 rpm, rate of climb still averages 750 fpm and Vmax is around 91 mph. indicated. It is one of very few VW-powered biplanes built anywhere, and one of the very few biplanes, worldwide, which has a genuinely good performance on a VW motor.
The handling is exemplary, with steep turns at relatively low speed providing a turn rate of 360 degrees in 7 sec. Take off is rapid, the aircraft breaking ground 7 secs. after the application of full throttle (prototype with EFS-2 carb.) Landing is straightforward, from an initial approach of 60 mph. (55 mph. practical - with the larger 'plans' tailplane) either from a slipping turn, a curved approach, or 'straight in' using peripheral data for assessing the flare, with no difficulty experienced in keeping straight with bursts of power against rudder on the roll out, despite the lack of brakes or steerable skid. Brakes and a limited caster tailwheel are also available.
Trimmed flight is achieved via throttle position, the CG location providing a very stable platform at V cruise. Power of manoeuvre in pich is enhanced by the 45%-30% CP travel, which provides for a very agile machine when manoeuvring. The aeroplane will fly 'hands-off' in cruise trim, small adjustments being made only to cater for fuel burn over time. At Vc the machine will return to level flight attitude 'stick free' in one half-oscillation when displaced to maximum pitch deflection, positive or negative, and the stick released: ie. dead-beat damped in cruising flight. Roll rate with the basic Z-21 two-aileron sportplane is very brisk, and ensures its suitability for aerobatic flight in the future, although the Z-1 Type S is the intended basic aerobatic variant, which is yet to be cleared in the UK.
Structurally the Z-21 will hold no surprises for anyone who has built a free-flight or radio-controlled scale model biplane to a reasonably large scale.
March 01, 2002
The Flitzer is an all-wood design, using traditional constructional methods.
The fuselage is all spruce (primary structure), with various thicknesses of
birch plywood skinning, and the wings and tailgroup are also of spruce, with
some Douglas fir in key areas.
Wings are piano-wire drag-braced internally, and these and the tailplane
feature a 1.0 mm plywood 'D' box leading edge. All flying surfaces are
Ceconite, Stits, or cotton covered.
The following data covers much of the philosophy behind the specification in
more detail, method of construction, general handling and operating
techniques. I hope that this will answer many of your questions.
Primary fuselage construction is spruce, longerons being 5/8" x 5/8"
cross-section, with 5/8" x 1/2" 'doublers' from firewall to aft the cockpit
on the top longeron, and for a shorter section on the bottom. Firewall
bulkhead/engine mount support is a ply-skinned spruce structure with ash
hardpoints. Wing spars are spruce, apart from the rear upper spar which is
Douglas fir, due to the higher compressive end-loading on this spar. Tail
unit is mostly spruce. Birch plywood gussets are used, and the fuselage is
ply skinned, using 1.5 mm, 1.2 mm and 1.0 mm in various areas. A 2.0 mm
ply floor is fitted and the tank bay is 2.0 mm ply decked. Wings are 'D'
boxed to the front spar rear edge with 1.0 mm ply. All flying surfaces are
fabric covered (Dacron, Ceconite, Stits etc.)
Main undercarriage is 1" dia. 16 SWG 4130 tubing, faired to a streamline
cross-section with balsa and fabric, etc., bungee sprung.
Tailskid is a rocking hardwood skid, pivoted on a bracket from a ventral
skeg assembly, restrained by bungees. The undercarriage provides a very
smooth ride over relatively coarse terrain and the machine handles
beautifully on grass without brakes or a steerable skid. Wheel brakes and a
castering tailwheel adaptation is an option.
Controls are 1/8 stainless steel extra flexible cable, and all runs are
short, direct, and low drag. Ailerons are 1:1 in operation, non
differential, but there is almost no adverse aileron yaw, and all controls
are light and powerful. No trimming system is fitted, nor needed with the
Z-21.
Interplane struts are hollow-box timber construction, ply-skinned, and
faired to streamline section with spruce. Cabane is a trestle-type 'A' frame
in 5/8" 17 SWG 4130. Engine mount truss is similar in 16 SWG. Most fittings
are flat, and all will be available soon as laser cut items, precision bent
to shape, where necessary, in the UK.
Although the Flitzer was designed to fulfill the old UK 'Semi Aerobatic
Category', this category has now been discontinued, and while the original
Z-1 prototype (with the smaller, slimmer tailplane) using mild steel
fittings, had a minimum reserve factor of 1.5 x the 3.8g Normal Category
requirement (ie. nearly 6g) much of the structure had RFs of greater than 2.
These elements were addressed in the 'plans version', and this improved
model is the Z-21, although no new analysis has been carried out to increase
the basic design to 'Fully Aerobatic' standard. The dedicated aerobatic
variant, the Z-1 Type S, is intended to fulfill this requirement, but no
stressing has been carried out in this version as yet. The type is under
construction in Canada and France, with others planned in the UK and USA.
The Type R is in the design stage, being the Rotec radial powered variant of
the Type S, with a shorter forward fuselage, Douglas fir longerons, an
increased chord lower wing, of deeper section (to match the upper wing, the
wing panels both of the Z-21 and of the basic Type S being of different
chords, upper & lower, as well as of unequal span on the 'S'). The 'R' has
more wing area to help maintain a similar wing loading to the other
single-seat Z-types, to compensate for the 220 lbs. dry weight of the 110
hp. radial.
In manoeuvre terms, the prototype (with the thinner stab.) has been
stall-turned (hammerheads), performed falling leafs, and also slow rolls
beautifully, similar to a moderately powered 2-aileron Pitts (commented on
by a Pitts builder). I haven't looped the prototype, due to the retention
of the early tailplane, which is constructed like that of a Pietenpol, and
of the same profile. Piets have been looped, and they are heavier than the
Flitzer, with a bigger tailplane, which is not braced in such a mechanically
advantageous manner as that of the Z-1. However, I see no reason to
experiment with the prototype Flitzer until such time as I decide to
construct and fit a new tailplane corresponding to that featured on the
plans.
Other variants such as the SK26 'Fighter', (all Doug fir primary); and the
Z-1M Flitzer Meteor, a lightweight cut-down Flitzer racer with fabric
covering for Mosler, Carr-Twin, Franklin, or other horizontally-opposed
motors remain as 50% completed prototypes for the moment. The last of the
Z-types to have been detailed is the Z-2 Schwalbe, a two-seater, retaining
the basic look of the original, featuring the low-profile elliptical
fin/rudder of the Type S, and spanning 19.5', and of some 16' in length.
Two of these are likely to be constructed in France, along with about four
Types 'S', while another Z-2 is underway in Australia.
So far three Z-types have flown: the prototype Z-1, and two Z-21As, the
'wide-bodied' version (24" fuselage width) being 2" wider than the Z-21.
All but the widest pilots find the standard 22" model perfectly wide enough!
February 28, 2004
Question:
I thought I finally had them straight in my mind! What is the status of the Z-3, single seat, classic lines fo the Z-1, but built for the A/C/Corvair?
Answer:
VW-derived motors (60 -80 hp.), and small, lightweight radial-types:
The Z-1 was the prototype, and all the 'smaller engine' types were Z-1s with various letter-suffixes.
Rotec R2800 radial adaptations (110 hp.):
The Z-1 Type R was an adaptation of the Z-1 Type S Stummelflitzer, ie. adapted to take a bigger, heavier engine, ie. the Rotec R2800 radial. The SK26 was a parallel development of the Flitzers, whose Doug fir primary structure and more radical departure in appearance from the Z-Types, as well as its 'Russian styling' evoked the name Maksimov (a contemporary Soviet test pilot) and SK for Samolet Kombinat or Skorostnyi Krylo, (Aeroplane Combine or Speedwing), respectively, the '26 being the putative year of its design. This aeroplane broadly followed the appearance of the Polikarpov I-5, and there was no need for a designation change following its adaptation, also for the Rotec R2800.
Purpose-built aeromotors, ie. Continental motors and in-line engines of bigger capacity.
The Z-3, so designated as it is the second of the purpose-designed Flitzers for the bigger engines (A-65, C-90, C-85) the first being the Flitzer F.2 Tiger (so designated to salute the Fieseler F.2 Tiger of aerobatic fame).
For VW-derived motors of minimum 80 hp. or others:
The Z-2 is a 'natural' designation for the two-seater, (once called the Zweisitzerflitzer) now termed the Schwalbe.
'Series' (plans-built):
The Z-21 (first double-digit designation) became the series designation for the plans-built basic Flitzer with the bigger horizontal tail.
I know this sounds complicated, but it stems from the desire to retrospectively rationalise the designs, which appeared piecemeal at different stages and dates, many not having been intended for plans-building, being one-off paper studies. However, at various times, individuals have pressed for one or other 'specials', such as the SK26 and the Goblin, which has then resulted in my taking these projects on full-heartedly, and creating more work for Gary :0(.
John Theron is extremely keen on the Z-3 (which is the old designation for the so-called Superflitzer - a term he didn't like). We came up with the name 'Falke' (Falcon) since the aeroplane looked more aggresssively 'fighter-like' than the Flitzers, even more so than the Stummels, and the name Flitzer Falke rolled of the tongue rather well...... The origins of this model are three-fold:
1/ Responding to the continuing expression of interest among, mostly US potential builders, for a Flitzer type that can be powered by heavier motors, such as the Continentals, or Corvair motors, which also require a longer installation length and greater fuel capacity. These motors would completely unbalance the airframe of the standard Flitzer, not only ruining its appearance, but would impact on fuel capacity if the airframes were radically altered for the fitting of these motors, or demanding other radical airframe changes, ie. stagger increases - which would destabilise the structure, demanding steel-tube 'N' struts, and stronger spars, or stagger reduction (ie. moving the lower wing forward) this requiring a radical fuselage re-design, and which would still not resolve the fuel problem. Fuel containment in the upprer wing would really demand an independent centre-section, as on the SK26, further radical redesign.
2/ Responding to the call for a bigger all-round single-seat aeroplane, with a bigger cockpit and greater potential payload, to accept the larger pilot, as well as utilising the larger engine option and greater fuel containment. Wing span and area would also be slightly increased, to maintain the same approximate wing-loading as the lighter Flitzers.
3/ Taking advantage of some pre-existing parts built for experimantal Flitzers, such a an intermediate Z-2 tailplane, and the original fin and rudder which I built for the prototype Stummelflitzer before the Praga engione appeared, which then ressulted in the re-design of that aeroplane, with the longer-chord elliptical fin/rudder, which is now standard, and also being used on the Z-21s. The 'big wings', now intended for the Z-3, were part of the earlier consideration of a 'big-winged' Flitzer Z-21, spanning 19', and illustrated on one of the Flitzer plan sheets, this aeroplane having at that time been provisionally designated Z-21A. This designation now only applies to the wider fuselage element that was drafted for this Z-21 model.
In many ways, the Falke is the answer to your own interest in a bigger, single-seat, Flitzer-type, which you've considered as a modified Z-2, with a 'suppressed' firewall for the bigger engine, and flown as a single seater. There would be likely less room for additional baggage on the Falke however, as it is really no longer than a standard Z-21, this compactness creating the very pugnacious appearance that is so satisfying, the fuselage being deep enough to 'bury' even the tallest pilots out of the slipstream.
I hope this lot clarifies the situation. As Cliff stated, it's getting to be as difficult to decipher as Waco designations. Or maybe Egyptian hieroglyphs.
The Jungflitzer was merely a suggested designation for the 90% Jungmeister Tribute, which has effectively lost out to the last, and best, F.2 Tiger evolution! This latter is also a design with the larger pilot in mind, if necessary, but more particulary for bigger, in-line engines, from the Cirrus on up.
Cheers,
Lynn
