One more thing: it is called Position Error, Leigh. I hope you told your students about it.
I once built a couple of precision digital altimeters for RAAF ARDU to determine this on the PC 9. Nowadays you'd use GPS but this was just before GPS. The aircraft had one precision altimeter in the back seat and one on the ground and was flown over at about 100 feet AGL while being tracked by kinetheodolite. It was interesting that you could see the altimeter on the ground go down by 1 to 2 feet as the PC 9 passed overhead. By recording the temperature, the altimeter readings and the geometric height about the ground the static pressure error could be calculated at all speeds from 70KIAS to 250KIAS by doing successive passes at 10 knot increments. Mike > On 22 Dec 2014, at 8:52 pm, Mike Borgelt <[email protected]> > wrote: > > Well I'm on record somewhere as having said that the Blanik was the greatest > disaster ever to befall Australian Gliding on account of the maintenance > intensive nature of the beast. I got my inspectors rating at a course where > we worked on amongst other things.....a Blanik. At the time I remarked that > the damn thing was too hard to maintain. 18 months earlier I arrived at RAAF > Pearce as met man and the met office was on a mezzanine floor in a Macchi > maintenance hangar. The Macchis looked strangely familiar in pieces and as I > found out later, handled about the same as Blaniks( very nicely). When your > design expertise is jet trainers I guess it shows that your glider structure > looks like that of a jet trainer. > > I'm well aware of the way the commies operated them. When the thing had done > its hours the People's Gliding Commune Number 3567 would put in a requisition > and if all went well sometime later the People's Glider Factory Number 3 > would organise to deliver a new one. > > Now the one thing about all the Eastern Bloc gliders I have flown (last time > I counted it was about 60 different gliders and sub types from all > manufacturers) that their handling qualities are all excellent. Even under > the collectivist system, some people took pride in their work and they always > took the time to make the handing nice. I've even seen a quote from a USAF > General who flew a Mig 21 that had somehow been acquired and said it was the > nicest handling little fighter he'd ever flown. > > I've flown an IS 28 at least once. The instructor in the back ( Malcolm > Jinks) said he didn't think much of it but I thought it was fairly > unremarkable. Certainly didn't standout as horrible like the 45 minutes I > once had in a Phoebus C or the Ventus A/B unless you put on winglets and do > the aileron throw mod I designed and remove any friction as much as possible. > Now go and check the span, aspect ratio, airfoil sections of the 21 and the > 28 and get back to us. > > Also flown a K 21 a couple of times in California for a few hours. Nice > enough and I agree a better glider to own as long as you buy the PU paint > option. So how maintenance intensive has the Vorgelat gel coat problem been? > T35 ain't much better and it is a disgrace that the manufacturers still offer > this. > > If you were thermalling the Blanik as you say, I guess you never heard of the > concept of induced drag. It may have been indicating 25 knots but if you look > up the wing sections, the Reynolds numbers and do the calculation you'll > likely find that the CAS was a fair bit higher than that as that wing cannot > reach such high lift coefficients.Likely you'd have done better by flying a > bit faster at something resembling minimum sink at that bank angle. > As for flaps, a K21 doesn't even have any. Dick Johnson's tests on flapped > gliders had some very interesting information on what flaps do and don't do. > An LS 8 is just an LS 6 with the flaps fixed in a slight negative setting. > > Mike > >> On 22 Dec 2014, at 6:58 pm, Leigh Bunting <[email protected]> wrote: >> >> Gee Mike, >> >> I can see that you have never had to work on these "eastern-bloc" metal >> gliders. I consider that they were a Communist plot to send western glider >> pilots mad. >> >> I spent 30 years working on Blaniks and they were a nightmare to keep tight. >> Forever replacing control circuit bearings for one thing. I understand that >> IS28's are similar. I have many, many more hours tearings Blaniks apart and >> putting them back together than sitting in the cockpit, even though a Blanik >> is quite nice to fly. The only thing in a Blanik I never took apart was the >> oleo strut. >> >> Back in the days Mike Burns was CTO, I said to him that I could ground every >> Blanik in Australia because one AD required measuring spar pin holes to >> 3-decimal places with tolerances to 4 IIRC. I had access to metrology >> equipment that could measure those numbers. Our Blaniks were out of spec >> then and I imagine no used Blanik then or now would comply - if that joke of >> an AD is still applicable. >> >> After we sold our last Blanik, I followed the new owner down to the airfield >> gate and locked it behind him so he couldn't get back in if he changed his >> mind. Then I went to the RTO/A and had all my metal ratings removed, so now >> I cannot even DI a tin can. >> >> These things were never meant to last as long as we have had them. >> Especially in our dusty climate. In the Communist countries, I'm led to >> believe that they replaced them regularly. I'm sure they never slaved over >> them like we have. There are even odd individuals who LIKE working on the >> things. These people are very 'special' to be politically correct. >> >> Having flown an IS28 once, I find your comparison to an ASK21 puzzling. >> Maybe on paper, but certainly not in practice. I found that you could >> thermal the thing with negative flap and it didn't appear to make any >> difference to positive flap. It's front pole was even longer than a >> Blanik's. I seem to remember feeling like having to look around my hand to >> see ahead. Anyway, the IS28 is nowhere near as pleasant as an ASK21. At >> least in a Blanik, I could thermal with full flap, elevator and trim against >> the back stops and 25kts or less on the dial. >> >> Let us know how many hours you have flying a Blanik, IS28 and ASK21 and I'll >> dig out mine so we can compare experience. >> >> Cheers and happy xmas, >> Leigh Bunting >> >>> On 22/12/14 15:08, Mike Borgelt wrote: >>> Shameful is what it is. It is well known that metal aircraft have two >>> problems when they age: >>> Fatigue and corrosion, both of which can be inspected for and rectified if >>> required. >>> Now it may not be economical to do the rectification but that can depend on >>> the particular circumstances of the owner. >>> Nothing to do with calendar life at all and an IS28 is hardly obsolete for >>> the purposes for which it is flown. As I have noted before, an ASK21 is >>> essentially a fibreglass IS 28. Look them up in Martin Simon's book on >>> sailplanes 1965 to 2000. >>> What a pity we don't have in this country an organisation dedicated to >>> promoting the interests of glider pilots and glider owners. >> >> _______________________________________________ >> Aus-soaring mailing list >> [email protected] >> To check or change subscription details, visit: >> http://lists.internode.on.net/mailman/listinfo/aus-soaring > > _______________________________________________ > Aus-soaring mailing list > [email protected] > To check or change subscription details, visit: > http://lists.internode.on.net/mailman/listinfo/aus-soaring _______________________________________________ Aus-soaring mailing list [email protected] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
