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On 2005-04-25 15:37:56 -0400, Peter Wendell said:
Even a true CLT machine will only be precisely CLT at one specific load. Quite true, and as you write it is the size of the moment arm that makes the difference. The arm on an RAF is over a foot! I would guess on Dennis-era Air Commands ("classic" to use his term!) it's about six inches. In re your discussion with Stu about Magnis, I'd like to state that you just flat can't eyeball vertical centre of mass. It needs to be measured. It *is* possible to design an aircraft with a high thrustline that has little or no pitch change with application of power (I am told the SeaStar Amphibian kitplane is one such). Just like it is possible to design a fixed-wing aiircraft that requires little or no trim change when adding or subtracting power (the B-17 is one such). In both cases it is extremely difficult to do, and so it is rare. Most airplanes with a high thrustline (mostly amphibians and ultralights with high-mounted engines) exhibit significant pitch change with power. But then, pitch change can't unload their wings and cause them to flap -- not so a teetering rotor. There are lots of folks that have flown many hours in unstable gyros. Yep. Some instruct in them: basically all the RAF factory guys, plus guys in their orbit like Dofin Fritts and Jim Logan to name two good instructors (yes, Dofin got his pee pee whacked and spent a year on the beach for breaking a rule. I bet he isn't going to break that rule any more). There are also too many that didn't make it. Bingo, Peter. The fact is that we now know how to build much safer gyros that are also much easier to fly. And we don't have to give up any speed or manuverability in the process. So, there is absolutely no reason not to do it. Bingo again. See, Peter, Stu, even Dennis: if you GAINED anything from a high thrust line, you could make a credible argument that the risk was worth the benefit, that it was a worthwhile compromise. But the claims made for un-stabbed and non-CLT gyros vice stabbed, CLT ones are unconvincing. Combine this with the availability of high quality dual instruction, and there's no reason that gyros can't acheive a safety record equal to, or better than, airplanes. Well, you can lead a horse to water but you can't make him drink. We are still having guys teach themselves to fly, or almost teach themselves. Crunch. More troubling, we have had some relatively low-time, but licenced and well-taught, guys prang, some fatally. That's part of what worries me -- there's always going to be the guy who will just go fly, and he is the bane of every CFI/BFI/AFI and manufacturer's existence. That syndrome, I think, is why Dennis withheld tail rotor gearboxes (I believe that was the part) from his helicopter customers until they could demonstrate training. Both helicopters and gyros can kill you dead without specific class and category training. (Type-specific is better if you can). There are many old timers who followed the Bensen method. The problem with that is that while the graduated self-instruction method in his manual seems to work if painstakingly followed, most pilot-wannabees haven't the patience and self-discipline to follow it. A Bensen B8M of course had far less energy than the gyros of today -- with its wooden blades and optimistically-rated 72 HP Mac (more like 40 HP!) it could just barely kill you (although NTSB records from the period of peak Bensen popularity shows that it did, frequently). I have only ever flown Near CLT gyros, but have learned much from those who learned on machines like yours and who find the current generation of stable gyros to be superior in every wa In the end the ASTM subcommittee working on gyro consensus standards did not require any particular way of meeting the stability standard, but did set a stability standard and required it to be demonstrated in flight test. I do not believe an unmodified HTL gyro can pass that test. -- cheers -=K=- Rule #1: Don't hit anything big. |
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