Bob Llewellyn

As the vendors of computers know, bigger numbers sell, even if of no actual significance - the employer / employee system is obsolete, it's got to be one-man businesses in consulting or de-facto subcontract arrangements. When are we ever going to accept a shorter working week?

struth, it's too expensive to land anymore... I'm staying up there...

...I can guess... you were mowing the airstrip, and tried to race a Thruster taking off! Silly... did it have the afterburner on?

Mmmm. but it's a cheap spinal injury, and (censored due to very poor taste)

Your maths appears correct, but politically unacceptable. Please find different facts. This reply is a free service provided by the "keep the mongrels in power, oi!" newsgroup.

Tax politicians. After 2 terms in parliament, put 'em in forced labour camps. How can we lose?

but ya gotta calibrate it! Cotton duck holds much more water than braided Dacron... I use an extra-aureal sensor on my T-83 (when one ear goes cold, it's raining...)

...wasn't named after Pierre Sag, the famous Franco-Swiss sausage maker? No, forget I asked...

For 4412, 0.15 chords fwd of LE and ~0.2 chords below it should be fine between zero degrees and 16 degrees AoA, by the tests of NACA Report 563; 0.15 below would start to depress the stall speed indication. I suspect the collar on the Pitts pitot is for tuning the static just as you describe.

Sounds like low cost, high value insurance, though might become a bit of a drag in a flying school environment. The old FIAT 850 Coupe had a centrifugal oil filter inside the fan belt pulley, which caught an awful lot of crud. How many people would be up for a better oil filter at a higher cost?

A shell engineer I chanced upon, said that oils start to crack at ~86C, and the rate of cracking doubles with every 2 deg increase. As sulphuric acid starts to evaporate at 82C, running your oil at between 85C and 86C should give a very long lubricant life; and provided each run lasts long enough to get all the oil up to temp and boil off the acid, it'll give your engine a very long life. As the cracking temp is a function of the carbon-carbon bonds, I don't see how a synthetic oil would have any difference, unless it contained silicone oil(s)... which it may well. There is an awful lot of engineering tradition about an engine's friction losses due to cold oil; and it's valid for Thomas the Tank Engine. Keeping the oil cool in the Corolla marginally improved fuel consuption, and eliminated the need to adjust the valve lash.

I once fitted an oil cooler - sandwich adaptor - to a 3K Corolla; I used a car air conditioner evaporator as the heat exchanger. The oil was still golden after 12,000km. Most oil coolers are way too small!

Woohoo! They've invented magnets? When Ricardo was designing bus and rail engines to run 10,000 hours TBO, he found that better oil filtration - removing ANY particles from the oil of ANY size- gave huge benefits. Modern car engines running quasi-ceramic bores can exceed their 100,000km warranty with small particles in the oil, and you'd want a new car by then, in this year's fashionable color! So why improve oil filters? Hmmm... Ship diesels generally cool and filter their oil within a mm of its life - why would they do that, if they didn't have to?

...that's not an easy question! Here goes: Accepted wisdom (and Certification): An aircraft may be considered a bunch of pressure fields; and as they are sufficiently intense to hold an aeroplane up, it is accepted that it is virtually impossible to produce an ASI system that is both suitable for everyday use, and very accurate in all possible operating conditions. The atmosphere keeps changing, too... Therefore, Certification requires that the airspeed indicator system be calibrated, and the corrections made available to the pilot. However, most people don't like reading correction cards halfway down finals, so gradually design standards have reduced the original wild freedom AISs once had. The calibration system involves getting the static system out of the aeroplane's pressure field, by towing it on a drogue ~ 30m below and ~100m behind (less for lighties) the aeroplane (there are pictures of jet airliners with plastic funnels on hoses hanging off them!). The pitot ends up as a pivotting (self-aligning) type on a boom several chords in front of the wingtip, or if flutter is an issue, as far fowards of the LE as possible. Practical Systems: 1) Static: The laminar sub-layer of the boundary layer, in air, is always very close to static pressure - if no extra pressure field is superimposed. The innermost edge of a turbulent boundary layer - outside the laminar sub-layer - is also very close to static, if unaffected by external fields. As the boundary layer gets thicker moving aft along the fuselage, and the main causes of external pressure fields - the propellor and wing - are normally towards the front of the fuselage, putting the static port(s) as far back as can be - without the tail affecting things - is good practise. Unhappily, a sideslip will cause a pressure difference from side to side of a fuselage; and it's NOT symmetrical - "T"-ing ports on both sides reduces the error to ~1/2, it does not eliminate error. Furthermore, putting the ports on little raised discs of aluminium because it's cheaper than a flush port, risks raising the ports into that part of the boundary layer containing fluctuating pressures (the fluctuation is too rapid for the instruments to detect, but the mean pressure will vary with speed). Symmetrical flush ports 3/4 of the way back on a roughly circular glider boom rear fuselage work very well. However, if a superimposed pressure field affects both the static and pitot pressure ports the same amount, no differential - or error - is shown on the ASI (due to superimposed pressure). So, mounting the pitot & static ports very close together gets around the static problem. 2) Pitot: Most forms of pitot - whether bullet-nosed, or conical, or just bits of tube with the end hacked off - give quite accurate results at up to ~20 degrees misalignment. All airfoils (unstalled) have two zones where the positive pressure of the stagnation point becomes the negative pressure of the accelerated flow (both above and below, generally); passing through zero. It has therefore been standard practice to poke the pitot out of the LE, 0.1~0.2 chords fwd of the LE and about level with the foward extremity of the airfoil, and tweak it until the AIS meets the design standard (needless to say, the slipstream is to be avoided!). Someone who had studies their NACA reports, noticed that there is a point about 20%~30% back along the underside of most airfoils (unstalled) where the local static pressure does not change much with AoA; and also recollected that the airflow adjacent to an airfoil, is essentially parallel to the nearest surface (except right up front). They therefore stuck a pitot port and a static port on a small pylon under the wing (~0.05 chords high), and filed a bevel off the trailing corner until the pitot-static difference represented the free airspeed. Look under a Piper Cherokee wing. The static error is not an issue; crossflow is not an issue (the wing acts as a flow straightener); sideslip is not a big issue; and few people bang their heads on it. That'd be my first choice. A combined pitot-static head, as far outboard along the wing (but not near the ends of any lift struts) as practicable, and ~0.15 chords ahead of the LE would be my second. Note that putting a shroud on a pitot gives up to ~30 degrees of misalignment without significant error, although the shroud supports have to be faired and well behing the dynamic (pitot) port.

Looks very neat. Experimental I presume... I look fowards to hearing more!

Okeydokey... at this range, I'm reduced to guesses... does it do it in slips both ways? And, where's the pitot? If more than one aeroplane do it, what's the common denominator? What WAS the strange thing the dog did in the night?

Turning the horizon off in a VFR aeroplane is very dangerous:tongue in cheek:... but I trust you know this??? ...unless there's a leak in the static system? The worms are out of the can...

Want to fly sans ASI? Get a Thruster TODAY!!!

Ricardo's "turbulent" head, and then the "shock absorber" head, were - as far as I know - the ultimate sidevalve developments; 91 RON ULP is an argument to go back to them, except exhaust valve cooling is a challenge in an air-cooled application...

Oops! got the RVP effect back to front - blending puts RVP UP, not down... the fuel commences to vapourise at a lower TEMPERATURE or a HIGHER pressure. Focus, grasshopper...

Yes, I agree most RAAus operators think weight doesn't matter if the strip is long enough... Do28 blue line is below stall at MTOW; this perhaps is the standard to aim for?

Does the Lightning Bug NEED a 912????

...I thought Ernie Peugeot ran a 4-valve head in the 1912 GP? PS - Honda read Ricardo's "The High Speed Internal Combustion Engine"; the postie bike engine is designed straight out of the third edition! Darn keyboard can't spell for nuts...

Let us suppose we have 2 liquid hydrocarbons, one with a Reid vapour pressure of (say) 0.8 bar, and the other with an RVP of 0.7 bar. Mix them together. The RVP of the mix will be less than 0.7 bar. Now take low-octane petrol, add triptane, toluene, and Methylcyclopentadienyl manganese tricarbonyl (MMT); the "octane" rating is now higher - probably about 95 RON - but the RVP is very low; which is why modern cars have sealed fuel tanks and the ECU is designed to cope with variable pressures and flows in the vapour return line. Indeed, it's also the reason most cars have a fuel pump in the tank (otherwise the suction would cause vapour lock). If you put such a fuel in an aeroplane with suction lift from the fuel tank, such as a Piper Cherokee, there is a good probability of vapour lock causing EFATO at ~100ft one summer's day. If a conscientious fuel company pushes the RON up to 98 "octane" by dissolving some butane in the blend, the RVP plummets for a few days, until all the butane has evaporated and the anti-knock rating has fallen. Now, the majority of the anti-knock hydrocarbons are slower-burning than aliphatics, so the combustion cycle needs to be adjusted to compensate; the difference is generally not huge at high manifold pressures, but car engines generally have quite sophisticated systems to allow sustained running at low manifold pressures. The issue here is that PULP can comply with the commercial standard, yet have a wide range of burning rates with varied additives. 100% iso-octane + TEL (100LL) is, however, 100% iso-octane + TEL, and burns like - you guessed it - 100% iso-octane + TEL. Back to those octane-boosting additives - MMT decomposes under storage, quite rapidly in hot weather; and the byproducts of partial decomposition tend to trigger partial polymerisation of the aromatics, creating a varnish of quite pleasant light-brown colour. There's not very much of it, unless you really stew your fuel, but you don't have to varnish a fuel filter very much before the flow rate drops. (MMT is not the only culprit, but it certainly helps the process along). We could drop the MMT and add a few % napthalene, but unfortunately it will condense out of the fuel at low temperatures, forming a substance with the initial texture of soft wax. try pushing soft wax through your fuel lines and pump... If you have a supplier of PULP, whose base stock is of sufficient quality that no butane is added, and whose turnover is enough that the fuel is always fresh*, and you operate with always-fresh fuel off a coastal strip and don't climb above a few thousand feet, in an aeroplane with a gravity-fed fuel system, and a well-cooled engine, you will probably never experience a fuel-related problem. If any of the above parameters are not met, you should expect a problem at some time. *Now it's not refined here, how fresh can it be? Spark ignition requires a tightly controlled fuel for tightly-controlled results; and for spark ignition engines that climb and descend, RVP ultimately demands either a pure fuel or pressurised tanks. The steam engine is undoubtedly the future for aviation...

...used to run Peugeot 404 & 504 engines with no de-cokes, on leaded, for ~150,000 miles, then change the rings and big ends - no decoke required. Yes, modern car engines have finally caught up with 1950s vintage french car engines... it's not a fuel issue!