LoonyBob

Under static conditions, propellors are running with a very high degree of recirculation, which remains significant up to 20~30kts foward speed (light aircraft). Recirculation gives a weird spanwise inflow velocity distribution on the blades, and so a weird lift (thrust) distribution - not very representative of flying conditions.. A look at fixed pitch props on TC'd aircraft (Cherokees, 172s etc) shows that a maximum static RPM of ~85% of full power RPM, will allow a healthy RoC, and WOT level flight without engine overspeeding; a 65% cruise of 1.5~1.6 Vs1 is typical, but 75% gives not much increase, as the prop is becoming depitched. This can be tweaked by adding a bit of pitch - a "cruise" prop - at the expense of a longer TOD. Fitting a CS prop to such a beast will give markedly better TO performance, simply because the engine is allowed to develop near full power for the entire TO roll and initial climb. At the top end, the CS prop will not change the airframe's power needs, but should offer 5~8% better cruise. Whilst Cherokee 172s are somewhat draggy, RAAus machines range from very draggy to very clean; however, a static WOT RPM of ~85% of full power RPM is a good starting point. Note that most fixed pitch props for TC'd aircraft have "overtwisted" blades (twisted beyond optimal performance for the speed range in question), because (a) tradition [most propellor makers still don't use blade element theory!], and (b) it tends to meet the overspeeding requirements for certification without much difficulty. Most (all?) composite RA blades are a tad undertwisted, which limits the propellor's efficient speed range. In summary: a CS prop will yield near-optimal TO performance for any aircraft, though not much if Vs1 >= 30kts; and should give optimal cruise, but not huge increases, subject to blade twist. A VP prop is a step in the right direction. The D18 gets a ground roll of ~110m, a healthy climb, and will cruise at Vno on a fixed pitch prop. The climb and fuel burn can be improved by drag reduction, and reducing the TO roll by ~15m is not worth the weight of a "live" prop...

Ye canna break the Laws of Physics, but it's fun to try!!! The Moni has a couple of design features to avoid it being too slippery, which of course impact the L/D; personally, I'd clean it up and fit airbrakes. Yes, V tails have two problems in an incipient or full spin, being (a) spanwise migration reducing the Cl, and (b) the control surfaces moving in opposition in yaw, and together in pitch... you can't get full down elevator with any rudder input. If the "conventional" spin recovery response doesn't work, cycling the elevators with anti-spin rudder is one of the options. In all honesty, if one is serious about going cross-country in an RAAus aircraft, large fuel capacity is more use than insane cruise speeds...

Re is speed x chord, J160 @ 56kt is same wing Re as T500 @37kt...

The trick of 382 is the Clmax is higher at very low Re than at higher Res, which is the opposite of most airfoils. It does make Thrusters (with more wing "ribs" than the early ones!) quite well mannered trainers... 4412 a la Rod is actually less draggy than it "should" be... perhaps a tiny detail in his development of the profile, perhaps a remarkably good flap-wing interaction. I'm with Nev on spoilers/lift dumpers; they're magic when spot-landing a glider... mind you, I've become quite enthusiastic about severe sideslips, which give as much glideslope modification, but with divebrakes you can slow down after the flare; and lift dumpers allow use of the wheelbrakes immediately on touchdown.

So described by student pilots, I am told!

Check out Gottingen 382(?)... there's a low Re report out there somewhere!

The Darts in CSIRO's F27 ("Cyrano") produced 250~280lbs per, depending on atmospheric & flight conditions (& TIT)...

Sydney West Welcamp? have a look at the airspace around Brisbane West Welcamp...

The HS is meant to be of sufficiently less aspect ratio than the wing, that the wing always stalls first. Not all designers make sufficient allowance for reynolds Number effects... Hey, Thorpe HSs are great, structurally and aerodynamically - and, with a properly set up tab, stable too; just not forgiving of poor execution... I personally don't like the birdstrike resistance...

NACA 23012 is very close to NACA 2412 with built-in reflexed flap, and it has a slightly higher Clmax; unfortunately, that form of variable geometry doesn't achieve what you want! Reflexing flaps tend to help overall aircraft L/D in cruise, because as the speed goes up and the nose comes down, most aeroplanes start getting separation off the underside of the fuselage. Assuming only mild convection (Europe, North America), Vno is set by Vb. The lower the aspect ratio, the less the (vertical) gust sensitivity, which is mainly why US aeroplanes are fond of an AR of 6.0 (Hersheybar Cherokee, Cubs, some Maules, etc). Unfortunately, this increases the induced drag... If one flies in a Strayan summer, convection can be strong enough to stall the wing, so Va becomes Vno. One needs some serious variable geometry to get an advantage... F111 style works!

The Traumahawk empennage, in a spin, enters a non-destructive state of flutter (it's not true aeroelastic flutter; merely, excited by vortices shed from the fuselage, the top of the fin waves about 4" laterally, and the HS bends on it); which both scares the crap out of instructors, and causes cracking in the structure at the base of the fin (and who knows where else, if you keep it up?). Most won't do it in an incipient, and some allegedly won't do it at all; but several operators in SEQ have experienced it in the last 30 years, and taken spin training off their agendae. WTF they used a T tail on a "spinnable" aircraft, I cannot begin to guess...

When I held a Shotfirer's Licence, it became clear that the science of explosives was a burnt and buried book to the populace at large. By allowing this state of ignorance to continue, we are all protected from both peaceful idiots who want to do high-energy landscaping, and malicious twerps who want to throw a very loud tanty. If I were to debate, on an open forum, the pros and cons of homemade IEDs, then that information would be widely available for a long time. None of us should use this forum to present practicable mechanisms for terrorism, because most all of us are likely to come up with better ideas than your average agro gronk.

Indeed. I would point out that a road vehicle could also carry and dispense the sort of payload in question. My T83 would barely get through plate glass, and you'd carry more walking with a backpack...

Ah - no, but... As far as I know, hardening gasket compounds are verboten in GA (they certainly used to be!), because of the risk of a blob getting free and blocking an oil gallery down the track; "Aviation Form-A Gasket" (non-setting tarry goo) and fibre gaskets, and a lot of swearing, were/are the traditional approach. I don't know a way to wipe off squeezeout from the inside of an assembled crankcase... That said, I've had very satisfactory results on car engines, with Permatex products, by cleaning scrupulously, and allowing the sculpted poop to cure before final assembly.

I consider the problem, in GA and RA, to be the lack of a spinnable trainer that is economically practicable. WTF do we not all do 3 hours with the GFA, where they have spinnable trainers and a great deal of currency on the manouvre??

The single engined tricycle Cessnas were an early form of spin-resistant aeroplane, although before that buzzphrase. BECAUSE they kept the CG so far fowards and used TE-stalling airfoils with stacks of washout, they don't have an adequate VS to recover from a developed spin, or even a steep incipient. The Cirrus is not designed with spins in mind, and was uncertifiable until political pressure was applied... from memory, BRS became a substitute for spin recovery...

Yes, Thrusters spin quite briskly...

That wing planform inspired a few later deigners, too! Will it fit into G?

Only if you've got a separation trigger at he rear edge of the canopy! A badly rigged Traumahawk does, and it costs a couplea hundred fpm in climb to boot; straight-back Cessnas, Cherokee relatives, and most gliders do not. Notchback Cessnas may, depending also upon flap setting... light aircraft that get "on the step" - that is, you have to exceed the desired cruise speed/height, then push it down and set power, to get an economical cruise - are aircraft that have separation from the top of the rear fuselage; by exceeding the desired cruise speed briefly, the rear fuse sticks up into the breeze ("favourable pressure gradient"), and the flow reattaches... Re gliders, Nev was alluding to the way the downwash behind the wing is taken into consideration, in order that they can thermal on the point of stall without separation, and zoom between thermals at insane speeds, also sans separation... they give NOTHING away from performance.

Cessna singles are normally set up so that the landing flap reduces the stalling AoA enough to lift the HS out of most of the ground effect.

Yes, depending upon the degree of destabilisation from a tractor propellor... The Thorp T-18 and Fletcher FU-24 are examples of aeroplanes with VS size reduced because of the long rear fuselage, as is the Lancaster... it's called "tail volume coefficient", and is expressed as: (wing area / VS [or HS] area) * distance between wing 0.25C and stabiliser 0.25C. If you are concerned about spin recovery, that distance is often squared. The higher the aspect ratio of the stabiliser in question, the "stiffer" it is - that is, the greater the rise in corrective force for a given angular displacement. For non-all-moving stabiliser light aircraft, a useful rule of thumb is that the HS wants to be about 20~25% of the wing area, and the HS ~15%; and stick then back as far as the propellor requires (then watch out for the wing wake with flap!). Cessna mostly burke the issue, by limiting the rearwards extent of the CG range such that they never need spin damping from the VS, and the pendulum stability of the high-wing layout removes the need for a powerful HS. Do NOT exceed the rearward CG limit! The V-tailed Bonanza is just bloody dubious; the early, lower-powered ones unquestionably showed adequate stability, except for the slight dutch roll syndrome; but the higher powered ones don't stack up for spin recovery, at least on paper... The majority of gliders (all single-seaters) are built with the knowledge that the pilot is wearing a parachute, and their airworthiness requirements don't require demonstration of a recovery from a 3-turn fully developed spin (neither do RAAus aircraft... - unless the term "developed spin" has crept into the ASTM recently!). The Navion is probably the best basis for figuring sizes for the empennage, as Piper caught Thorp's all-moving HS disease (the maths for setting up the anti-balance tab to achieve positive stick-fixed AND stick-free stability is quite complex), and Cessna cheated. The cruciform tail Bonanzai are also pretty good. Note that, whilst positive stability is the prime desideratum, it is possible to have a HS too small to rotate the aeroplane into the stalling attitude on landing, as the HS enters the ground effect; most high-wing aircraft push this issue, as the pendulum stability term becomes too great for, say, a Piper Cub HS. The Cub solved this by having an immensly powerful trim - more powerful than the elevator; which was made illegal for new designs after it caused fatalities. The Maule M5 is an interesting study.

I'll throw this out: Did RAAus finally get the go-ahead for CTA endorsements, because Badgery's Creek is going to close (CTA) off the whole Sydney basin to lowlife scum like us?

95:10 has a stall speed limited by wingloading, which automatically limits the cruise etc (physics); 101:55 had 40?kts clean stall, the ASTM (LSA) had 40kts clean in the USA, 45kts clean in Aus. Since the root bending moment the wingspar has to cope with is a function of the span, and the spar strength is a function of the square of the depth, and the spar stiffness (flutter resistance) is a function of the cube of the depth, pushing the span up very quickly pushes the weight up. Also, as the airfoil 2-dimensional L/D is very sensitive to the thickness-chord ratio, deepening the spar means increasing the chord in proportion; the inverse cube law again pushes the weight up fast. A bigger wing needs a bigger HS for positive longitudinal stability, and bigger / further out ailerons mean a bigger VS, both of which require a stronger rear fuselage, all of which put more energy into the undercarriage, hey poop it won't climb, get a bigger engine... How many RAAus aircraft have much more than 10m wingspan or 12 square metres of wing? Re the speeds, if you're prepared to have marginal hot & high performance at MTOW (PA-28-140? VP2? asthmatic J-160 with big wheels & no spats? T83 with the original 277?), then cruise will be about 1.6~1.75 x the clean stall speed. If you manage a better power to weight, especially with a cleaner airframe, you can see Vno = 2Vs1, and with an RAAus wingloading, climb will be spritely. More is possible, but that low wing loading means convection will tend to break your teeth as Vno gets up, and the limit load factor will exceed 4G at not much over 100kts. M. DelaMontez's polygonal wing (which also incorporates 3 airfoil changes and rather tricky washout) manages to trick the problem, to the stage that the D18 has a Va twice Vs1, but Vno = 2.25Vs1 (i.e. 90kts). The Thruster T300 uses one of the very few airfoils known to have a LOWER Clmax at higher Re, thus allowing Newton H. to push the Vno (Vb) up to match the Va, at 72kts, which is also Vc for that aircraft. I have given the matter considerable thought, as I personally want an RAAus owner-maintained single seater with a Vno of 250kts... and I imagine I will continue to do so!

CASA is a body corporate, and liable to sue or be sued in its own name. So it need to cover its arse... LAME maintenance is used for GA singles, which are allowed into Controlled Airspace. by using the same maintenance standard, CASA is observably protecting the peole on the ground from those huge speedy dangerous ultralights crashing through their roof... It's a legal defence, which is now the primary criterion of all CASA decisions (thanks again, Mr Keating!)

We've actually got the second AUF Pilot Certificate (number 00002) around here somewhere... issued to the founding president of the AUF, George Markey. The 400lb weight limit for 95:10 was based upon a Skycraft Scout with a largish pilot, and was fairly comparable with FAR Part 103 at the time. A few wags suggested that it meant a crashing Ultralight wouldn't penetrate a tiled roof, but I've never seen that in print (the maths kinda works out, though!). The AUF was a result of the CAA trying to pre-empt HORSCOTS* 1986, by refusing to parley with anything but a single national group representing all Ultralight flyers. The AUF was hammered into being just in time. HORSCOTS 86 had, as one item on its agenda, the related issues of the high incidence of ultralight prangs in the media, and the vexed issue of "illegal" heavy ultralights, and two-seaters being used for training, which the CAA were denying (a) existed in any quantity, and (b) there was a need for. I had the pleasure of seeing Kyril B. of the CAA respond to the Chair with the statement that the CAA knew of approximately 25 overweight ULs. including 2-seaters, and thought there may be as many as 50 in the country. At this point, Geo handed the Chair a list of signatures of the ~1,200 people who had been willing to sign their names as operating overweight/2 seat ultralights... The summary was: (1) Training is a critical safety factor; the CAA is responsible for the safety of every aircraft that flies in Australia; therefore, the CAA had to make UL training practicable. (2) Operating a flying school is providing a service, and under the TPA customers are entitled to a "reasonable" standard of safety; so the CAA better get off its chunk and write Design (Airworthiness) Standards for 2-seat UL trainers. The existing Thrusters and Drifters were swept up under the ghastly CAO 95:25, while 101:55 was being writ. 101:55 targetted 1000lb (450kg), after a number of aeronautical engineers argued that anything less was anti-safety and ludicrous to boot, with BCAR-S in mind. US EXperimental was the founding father of most recreational aviation as we know it; and a fundamental precept of Experimental was, "these aircraft must be useless as commercial products / unable to compete in any way with Certified light aircraft". Ever since BeeCessnaPiper got that in stone, all recreational aviation has been fighting the nonsense idea that RA aircraft must be as small/light/slow/useless as governments can possible mandate. I note that the heaviest US Experimental aircraft I wot of, had an MTOW of 475,000lb (from memory), and the fastest had a maximum level speed of Mach 2.6... Meantime in Oz, sometime during the '90s the High Court determined that there was no Constitutional reason that adults should be forbidden from indulging in such dangerous activities as "Extreme Sports", and so a proposed ban on commercial skydiving was nipped in the bud... yes, we were that much of a nanny state. After 101:55 had been flourishing for a while, some US pilots took note, and bitched about not having an equivalent until the ASTM were told to create LSA, which still followed the US penchant for dangerously low stall speeds, but allowed 600kg MTOW (up from the proposed 1,200lb). Some Oz pilots (and manufacturers) took note...