Roost Air Lounge => The Classroom => Topic started by: Stef on February 21, 2006, 10:15:57 PM
Title: New category
Post by: Stef on February 21, 2006, 10:15:57 PM
Here's a new category for you! I thought it would be a good thing to have a special place where we can conduct some practical eLearning... Where rookies can aks questions and the masters among you can share their knowledge (also among themselves of course). It's sort of a side-track to the "Aviation related topics" area. Rules for this category: there are no stupid questions.
Title: Re: New category
Post by: Plthijnx on February 22, 2006, 02:27:14 AM
ok, i'll be first.....
i just landed a job with a major pipeline company here in houston and am going to have some extra $$ that i'm probably going to throw towards getting my sling wing add-on. question: do i have to take any written exams? will my headset work in the robinson r-22? how many "bad habits" am i going to have to "shed"? here is a link to Helicopter Services Inc. (http://www.heliserv.com/main/index.htm) the school that i'm looking at for my training....Freddy
Title: Re: New category
Post by: Sleek-Jet on February 22, 2006, 03:34:01 PM
What ever you do.... don't do this... (http://www.hummingbirdhelicopters.us/movies/helocrash.wmv) ;D ;D
I've kicked around the idea of getting my swing wing rating. There is a place here in town that advertizes a private for a fixed wing pilot for about 8000. Don't know what's involved.
Title: Re: New category
Post by: Plthijnx on February 22, 2006, 08:09:58 PM
holy crap!! that's one lucky dude!
Title: Re: New category
Post by: Gulfstream Driver on February 22, 2006, 10:40:58 PM
Wow. Darwin runner up?
Title: Re: New category
Post by: Frank N. O. on February 22, 2006, 10:53:14 PM
Nice forum-idea, especially with these nice guys and gals here :)
Regarding the award-winner then I think I've heard the story behind it, he just bought it at started flying, appearently with either little or no helicopter training, and as you can see it was right in the middle of aircraft parking, he was lucky, I wonder if he lost whatever license he may or not have had for that stunt. Btw, he flies just I do, except I do it in a flightsimulator program and would never fly one in real life, at least not as a pilot, although I have heard it's actually easier in real life than at least Microsoft Flight simulator 2004.
Has anyone here made a video showing normal taxi and take-off procedures done correctly, showing the control-movement? I'd love to see that.
Frank
P.S. I do know that for any simulator then what controls you use is paramount, and the stiff unprecise Logitech joystick I have to use is not good, not for fixed-wings either but a yoke is expensive, but I've got a plan to build my own.
Title: Re: New category
Post by: Stef on February 22, 2006, 11:17:17 PM
I've seen this video before... This guy is not only lucky he didn't kill himseld, but also that he didn't kill innocent bystanders!! In my opinion he should go to jail for that!
@ Frank: Ah, another thing you want to build yourself? You should change your name into McGyver! ;) ;D ;D
Title: Re: New category
Post by: Gulfstream Driver on February 23, 2006, 12:27:21 AM
The problem with sims is there's no "seat of your pants" feel. I always flew IFR in the plane better than the sim.
Title: Re: New category
Post by: fireflyr on February 23, 2006, 12:38:42 AM
What ever you do.... don't do this... (http://www.hummingbirdhelicopters.us/movies/helocrash.wmv) ;D ;D
I've kicked around the idea of getting my swing wing rating. There is a place here in town that advertizes a private for a fixed wing pilot for about 8000. Don't know what's involved. [/quote
LMAO---omygod, Let's hope he can't reproduce!!!!!!
Title: Re: New category
Post by: fireflyr on February 23, 2006, 12:52:25 AM
I'm with Gulfstream on the sims, the only time i've ever spun in IFR (obviously) was on a rented sim at the airport.
IMC is easy in a airplane compared to any sim I've ever flown and I believe that's why they're an excellent training aid.
I fly one every spring before I go down for my annual 135 ride, it does help.
Title: Re: New category
Post by: Plthijnx on February 23, 2006, 01:23:39 AM
hehe, my friend today had to do a CAT3 approach this morning into IAH in the MD-11 he flies and now he has to go to Georgia to do a sim ride to stay current. the kick in the but is he only needed ONE landing and now he has to do a checkride! LOL! sucks for him but i get to raz him about it!
Title: Re: New category
Post by: Frank N. O. on February 23, 2006, 10:54:42 PM
Stef: Lol, actually my friends just knows me as Frank and they know I have a ton of ideas spanning everything from planes, cars, computers, games, etc. I'm very versatile and creative, and I've been like that forever, I got it from my dad, he was like that too, a big kid, loved life (and the freedom of driving) and I got some logic from my mom so I don't waste all the few money I have, great combo :D I also have a plan already laid out to build a frame with a real carseat and real carpedals for my driving-sim and hooking them up to my game-pedals so I wouldn't need to dismantle it and loose the programmed calibration, I plan on using early Ford Mondeo parts btw since they fit me well (aka Ford Contour and Mercury Mystique).
I love sims, and have spent many long thoughts on how to bridge the gap between sitting in the real thing and sitting in front of a monitor so I could maximize the use of the simulator and controls is the big problem, especially with flightims since you have to use key-combos and mouse-clicks to use controls and levers you'd use by hand in a completely different way in real life, and I'm very practical minded in terms of learning controls so sims don't do much good in advanced planes that have several controls and when using navigation and radio-systems, but then again as you said yourself, there's no seat-of-the-pants feel so small planes won't be simulated proporly either, or cars for that matter. I have a force-feedback joystick but flying the Cessna in FS2004 didn't seem realistic at all for me, when pulling back I had constant backpressure unless I pushed it rapidly forward and then pulled back again, then it would be kept back. I haven't flown wildly in real life but that doesn't seem realistic compared to how the plane mouvred in the air and thereby how the airflow would affect the control-surfaces.
For a real-life question though, I'd like to know how effective it is to have an adjustable propeller (called constant-speed right?) and what the trick is to adjust the engine-power together with it, with either a piston or gasturbine engine. Also, how come a piston engine has a manual mixture control but a turbine doesn't?
Frank
Title: Re: New category
Post by: Gulfstream Driver on February 24, 2006, 12:34:21 AM
First, on your flight sim, you might be able to trim the plane so your force-feedback stick doesn't give you any trouble. I assume you have the realism turned up...
Adjustable pitch (or constant-speed...same thing) props allow the pilot to select engine RPM separate from engine power. They are more efficient than fixed pitch props because they are adaptable to each phase of flight. Generally, you want to adjust manifold pressure (power) so that it is equal or lower than engine RPM so that it's easier on the engine. Throttle (black) controls manifold pressure and the Prop Lever (blue) controls RPM. I found a pretty good website that explains a lot of physics behind the concept.
I'm not sure about jet engines...I know basically how they work, but we never discussed why there isn't a mixture handle. I do know that higher is better with jets.
Piston engines have a mixture lever because the engine burns fuel most efficiently at a 15:1 air to fuel ratio. More than that, and your just dumping extra fuel out the exhaust manifold. Less, and the engine runs rough. The ideal amount of fuel actually going into the engine is going change depending on altitude, so you need to be able to adjust the mixture.
Title: Re: New category
Post by: Sleek-Jet on February 24, 2006, 02:06:35 AM
A constant speed propeller is an adjustable pitch propeller, but an adjustable pitch propeller is not necessarily a constant speed prop. ;D
A constant speed prop's pitch is determined by a govenor that supplies oil pressure to the hub of the prop. A set of fly weights and springs adjusts the pitch to maintain the selected RPM.
An adjustable pitch prop can either be changed on the ground (most are this way) or the blade pitch can be made in flight using a cable controll. They will not hold a selected RPM however, and behave like a standard fixed pitch prop in flight.
The best way to set power is to adjust the throttle to the desired manifold pressure (most of the altitudes that I fly at makes that wide open throttle), then adjust the prop controll to the desired RPM. Finally, lean to best power or best range... or however you run the engine.
I always find what RPM the engine runs smoothest at (the "sweet" spot) and then find the manifold pressure for the desired power output.
Title: Re: New category
Post by: Frank N. O. on February 24, 2006, 02:22:07 AM
Thanks for the link, I should however have re-phrased part of my question, being a car-enthusiast and having my dad work on his own cars since he was young then I know about lambda-1 (14.7:1), however I don't know why all piston-engined airplanes I've ever heard of have the mixture controlled manually when, as you said yourself, there is only 1 optimum setting and why gasturbine-engined planes doesn't have such a control, although judging from real and simulated cockpits from a Caravan it seems to have two or three other types of fuel-controls besides the throttle (Emergency Power, fuel cut-off switch and some other fuel lever next to the throttle on the other side of the emergency power).
To my understanding then a variable propeller is sort-of like a gearbox on a car, to allow running the engine at lower rpm while maintaining thrust, I didn't know there was more than one type of variable propeller though, but now I know why it's called constant speed. While on the subject, just to confirm, feathering a propeller means adjusting the pitch to minimum drag, normally only in case of engine failure correct? Although then I wonder why the Caravan's cockpit have thrust-reverse controlled by the throttle lever and not the prop lever. Ah so many questions :D
Thank you both for the replies, and thanks for the link :) Speaking of teaching material, can anyone recommend the private pilot book by Rod Machado? I was thinking of buying it (even though a pilot license isn't exactly in the cards anytime soon). Frank
Title: Re: New category
Post by: Sleek-Jet on February 24, 2006, 02:38:29 AM
Automotive carbs usually only operate a one altitude most of the time, thus they can get away with a fixed mixture setting supplied by the jets and or metering rods.
Airplane carbs have to be able to operate over a wide range of altitudes, from sea level, all the way to 15000 feet or even higher. So, a way of adjusting the mixture is required for optimum profomance. At higher altitudes, leaning for best power is mandatory for satifactory perfomance.
The mixture controll on aircraft carbs is essentially a movable metering rod.
As far as the Caravan and all those power levers... what would be the mixture lever in a piston engine is the "condition" lever for a PT6... it essentially turns the fuel on and off. The throttle lever on a turbine is the "power" lever, and it adjust the fuel metering to the power section. The more fuel and air, the more power a turbine engine will make, until you either reach a temperature limit or a power limit set by the manufacturer. There is no lean or rich mixture, a tubine engine needs as much fuel as there is air to burn it with. That's why higher is better. The less air there is, the lower the fuel burn.
Keep in mind that a gas turbine is a completely different animal than an internal combustion piston engine.
There was a really good set of article in AOPA pilot a few years ago about the fuel metering circuit and power outputs in turbine engines. If I can find them, I'll post them here.
The "beta" range, or reverse, is on the power levers as a mater of lowering pilot work load. The didn't always used to be there. I've seen older aircaft with "reverse" pitch toggle switches.
Title: Re: New category
Post by: Gulfstream Driver on February 24, 2006, 04:22:08 AM
Yes, feathering is used only in real emergencies. Can you imagine the resistance for a running engine if it had to spin a prop that's 90 o to the direction of travel?
I've heard that Rod Machado is quite good. He adds humor to his lessons, which makes them easier to read. I like Jeppeson, because they have very good pictures. I've never used anything else. The King programs are supposed to be very good, as well, but they're quite dry.
Title: Re: New category
Post by: Inept on February 24, 2006, 05:16:27 AM
I've used the King system for my instrument rating, and now for my commercial license. Saying they're dry is like saying that the ocean is wet. They're mind-numbing. That having been said, they are loaded with good information, and since they are videos, you can rewatch the sections you zone out on. It's like a boring academic lecture at college, except that you can pause the lecturer, and no one will complain if you bring beer into the classroom with you. ;D
Title: Re: New category
Post by: Gulfstream Driver on February 24, 2006, 03:41:32 PM
Not a lot of people complain about beer in a college classroom, either. ;)
Title: Re: New category
Post by: Plthijnx on February 24, 2006, 10:22:43 PM
Yes, feathering is used only in real emergencies.....*snip*
not necessarily. in twin training and on the check-ride the applicant has to demonstrate securing an engine (usually the left).....just sayin' :D
Title: Re: New category
Post by: Gulfstream Driver on February 25, 2006, 01:09:29 AM
But, if you do your multi in North Dakota in January, you practice securing, but the instructor zero-thrusts the engine. :)
Title: Re: New category
Post by: Plthijnx on February 26, 2006, 05:12:27 AM
yeah, i did plenty of zero thrust throughout my twin training.....however one thing that i wasn't expecting was that on my check ride i had to secure the engine while under the hood. took me by surprise but i just followed the check list proceedures and all was well. the scenario given to me was that "we were losing oil pressure and had to shut down and secure the engine to save it for landing." my D.E. was/is the type of guy that i'd of loved to have had for all of my checkrides. he makes sure you get your money's worth. it's not only a checkride but also a lesson. he loves to teach. anyway, i could give him props all day long but for the discussion, he had me secure the lefty and then shoot my ILS into Galveston. the only thing i goofed on was i "ducked under" once i reached DH rather than follow the GS to the runway. eh, i was trying to impress him by landing on the numbers...oh well, we both got a chuckle out of it.....Freddy
Title: Re: New category
Post by: Frank N. O. on February 28, 2006, 02:57:26 AM
Thanks for the explanation about the levers :) For me it would be most logical to have the reverse-pitch a part of the main prop-pitch control after feathering but people are different so no problem there, and sometimes you can learn a different system, I do also see an advantage in the system since you normally throttle back when landing and then with that control-system you can go back over a click or something and go straight into reverse thrust.
I know planes have to be a lot more sturdy and reliable than cars but how come there's no automatic mixture system now that there is also fuel-injection instead of carbs, also eliminating risk of carb ice according to articles I've read.
In MS Flightsimulator both the King's and Machado have been in the instructor section for several versions and yes the King's might be more dry but when one wants to fly they tell the facts straight and calmly as one would need them, but I guess it depends on one's personality if that works for you, in fact I read one place that you should make sure you chose an instructor you're on wave-length with otherwise the instruction won't work as well.
Frank
Title: Re: New category
Post by: Gulfstream Driver on February 28, 2006, 04:36:49 AM
The student-instructor relationship is an important one. If you don't click, it makes it a lot harder to teach. My first student was very quiet and reserved, and extremely hard to read. I could never tell if he was excited or not. Made it difficult to figure out how to teach him.
Title: Re: New category
Post by: fireflyr on February 28, 2006, 11:51:16 AM
The new FADEC systems seem to be the answer to the engine control complexity in light aircraft, as usual for aircraft, it's taking time for them to be implemented but they are coming. Anyone out there flown one yet?
Title: Re: New category
Post by: Frank N. O. on April 14, 2006, 06:26:36 PM
I see we're still waiting to hear from a FADEC pilot but in the meantime can someone give me an idea of what an ultralight with a "chambered wing" is? That was such a thing my best friend Chey soloed in. Googling for that didn't gave any real results either. She did say it was controlled with a stick and had kind of a windshield so it wasn't a motorized handglider.
Frank
Title: Re: New category
Post by: Gulfstream Driver on April 17, 2006, 06:11:27 PM
is that chambered or cambered?
Title: Re: New category
Post by: Frank N. O. on April 17, 2006, 07:49:34 PM
I'm pretty sure she wrote chambered because I remember it puzzled me but maybe the h was an error since she was a bit under the weather and tired last we talked, she sadly has a lot on her mind health-wise atm (btw I always make sure if she wants to talk or rest when she's not feeling good). Having a 9 hour time difference is a big problem even if I currently sleep off-set almost the same amount of time.
Frank
Title: Re: New category
Post by: Gulfstream Driver on April 18, 2006, 04:32:15 AM
That's too bad about your friend.
The only thing I can think of that might be a chambered wing is a parachute. They do make paragliders where you basically hang a frame and an engine below a parachute....Not sure if that's what she's talking about.
Title: Re: New category
Post by: fliboye on June 02, 2006, 05:11:16 PM
the caravan has the reverse thrust triggers on the throttle because as you force the oil into the prop hub to push the blades to a negative angle you must in crease the engine speed so you do not over temp the engine it is a reverse flow engine which means the air is sucked in the back of the engine and pushed through to the front same as a king air. to answer the question the prop lever only controls prop rpm and the mixture controls engine speed on the ground hi and low/ fuel metering for another word. It is agreat airplane to fly cruise at 160kts. downhill at 175kts to the MM and stop by the first taxi way. by the way it stalls dirty at 45kts. waaaaaaahooooo!!!!!! ;D 8) :P
Title: Re: New category
Post by: Frank N. O. on June 02, 2006, 06:56:14 PM
Gulf I must've forgotten to reply to this, last I asked then she said it did have a small enclosure and instruments so it probably wasn't a hang-glider-wing but I'll try to ask her again later.
Fliboye: Thank you very much for that detailed explanation, that was very informative and I like information about vehicle technology :)
Frank
Title: Re: New category
Post by: ZAIZAI on July 20, 2006, 09:07:48 PM
Eh? A diver driver that I have tons of respect for, he is top dog in the Swedish Air force (I could kill for his job, some of the time), anyway he feathers the prop (DHC-Singel Otter, turbo prop) when loading jumpers. Darn the thing turns so slowly you can count the blades!
Have a question(s) about turbines and turbo-props. I know how a gas-generator work but how do you transfere the energy produced to the prop? In thrustor jets I understand the concept, but it gets a bit hazy for me when a prop is involved.
-Helicopters, is the main rotor shaft, power turbine and gas generator physicly connected to each other or is the gas generator rotating freely supplying gas to the power-turbine which via a reduction gearbox supply power to the rotorshaft? Is the gas-generator and powerturbine on the same rotating spindle or are they not joined?
-Turbo-props, same question really?
-Are there any instances where the powerturbine is hanging on the same shaft as the gasgenerator? Not jets...
Title: Re: New category
Post by: Mike on August 12, 2006, 06:54:19 PM
Eh? A diver driver that I have tons of respect for, he is top dog in the Swedish Air force (I could kill for his job, some of the time), anyway he feathers the prop (DHC-Singel Otter, turbo prop) when loading jumpers. Darn the thing turns so slowly you can count the blades!
Have a question(s) about turbines and turbo-props. I know how a gas-generator work but how do you transfere the energy produced to the prop? In thrustor jets I understand the concept, but it gets a bit hazy for me when a prop is involved.
-Helicopters, is the main rotor shaft, power turbine and gas generator physicly connected to each other or is the gas generator rotating freely supplying gas to the power-turbine which via a reduction gearbox supply power to the rotorshaft? Is the gas-generator and powerturbine on the same rotating spindle or are they not joined?
-Turbo-props, same question really?
-Are there any instances where the powerturbine is hanging on the same shaft as the gasgenerator? Not jets...
I am not a turbo prop of much of a fixed wing guy but our SEAT's here at the base (single engine air tankers) run turbo props and one of them (the one with the Pratt&Whitney engine) puts his props into feather when he is idling and getting loaded with retardant to not blow the ground crews away when they load him. I am assuming that's what your buddy is doing when he is loading jumpers..... There is no real problem with the feathering since the engine is not direct drive. It might get warm a little because the power turbine might turn a lot slower than the gas producer.
On helicopters the gas producer and the power turbine is not mechanically connected as well (you couldn't start it unless you'd put in a seperate clutch) and they link up later at full speed only by what is called "gas coupling" when the essentially turn the same speed or close to it. The gas producer and the power turbine are usually two drive shafts with one of them being hollow and the other one turning inside the first one without any mechanical connection between eachother. That way you don't need a clutch when you start the engine. You speed up the gas generator with its compressor wheels and its turbine wheels and the power turbine is just another wheel you "hang" in there to drive something with it (in case of the helo, the gearbox that drives the rotor).
I hope I explained that ok. ;D Sorry for responding so late. I can't always check out all the threads. If you have any more questions, fire away! I am ready!
Title: Re: New category
Post by: Frank N. O. on August 20, 2006, 02:47:02 PM
After reading about the ladybug in the pitot-tube then I'd like to ask something (while hoping it hasn't been replied to here before). In flightsims there's usually a switch named alternate static, is that related to the pitot tube for the instruments relying on vacuum or am I mixing a lot of things together? And why is the pitot-tube usually on the leading edge on the wing and not the nose, is that so the pilot can check it visually (since I've often seen it placed on the left wing).
Greetings Frank
Title: Re: New category
Post by: fireflyr on August 20, 2006, 03:46:15 PM
After reading about the ladybug in the pitot-tube then I'd like to ask something (while hoping it hasn't been replied to here before). In flightsims there's usually a switch named alternate static, is that related to the pitot tube for the instruments relying on vacuum or am I mixing a lot of things together? And why is the pitot-tube usually on the leading edge on the wing and not the nose, is that so the pilot can check it visually (since I've often seen it placed on the left wing).
Greetings Frank [/quote Good question Frank, |:)\ The pitot tube is generally located on the wing on single engine aircraft so as not to be affected by propeller wash---it supplies ram air, the pressure of which expands a bellows device which in turn operates the airspeed indicator needle so it needs to be in an area of undisturbed airflow to give an accurate reading. Multi engine airplanes generally have the pitot mounted on the nose. The static side of the A/S indicator, rate of climb indicator, and the altimeter are routed to an outside area of the aircraft where the pressure is neutral and the alternate static source (which vents the instruments to the cabin) is to be used if the static port becomes plugged. On aircraft without an alternate static source, the glass on the rate of climb instrument can be broken as a field expedient if the static port becomes plugged. In 40 plus years of flying, I have never experienced a plugged source of either, but it can happen and a pilot should be aware of the potential and be able to fly the airplane (VFR) in that condition. That's another good reason why instructors should teach with the panel covered (again VFR). Hope this helps and I'm sure some sharp instructor will correct my simplistic explanation. 8) Jim
Title: Re: New category
Post by: fireflyr on August 20, 2006, 03:48:05 PM
How the heck did I quote myself in the previous post----DUH!!!! :-\
Title: Re: New category
Post by: Frank N. O. on August 20, 2006, 03:49:56 PM
LOL thanks for the reply. I think the problem is that there's one (quote) too many in the text.
Frank
Title: Re: New category
Post by: spacer on August 21, 2006, 02:40:37 AM
If the chambered wing spelling is correct, and it is a powered 'chute, they do have some really elaborate chassis for those things nowadays. A windscreen isn't farfetched at all, and a bunch of 'em look kinda like brightly painted flying dune-buggies. Some have bodywork, though I've never seen an entirely closed cabin, but I wouldn't put it past some folks to try it. I guess it'd take the open-air charm out of it, and at 30mph or so, that's really what it's all about.
Title: Re: New category
Post by: fireflyr on August 21, 2006, 11:02:59 PM
If the chambered wing spelling is correct, and it is a powered 'chute, they do have some really elaborate chassis for those things nowadays. A windscreen isn't farfetched at all, and a bunch of 'em look kinda like brightly painted flying dune-buggies. Some have bodywork, though I've never seen an entirely closed cabin, but I wouldn't put it past some folks to try it. I guess it'd take the open-air charm out of it, and at 30mph or so, that's really what it's all about.
HUH ??? ???
Title: Re: New category
Post by: Frank N. O. on August 22, 2006, 12:20:34 AM
Thanks for the info :)
Jim: In case the ?-mark was why he typed this then I'm sure he's replying to a question I asked a while ago in this thread about the flying machine my best friend Chey had solo'ed in but the description she could remember kind-of contradicted the std. types of ultralights but he could now say that there were all kinds of variations on the types.
Frank
Title: Re: New category
Post by: spacer on August 22, 2006, 03:47:44 AM
Chamber-wing... a parafoil with chambers which inflate when you get a little airflow into them. The term may not be 100% accurate, but IIRC it was. (http://www.buckeyeaviation.com/gallery/firstflight/images/lisa.jpg)
Title: Re: New category
Post by: fireflyr on August 22, 2006, 12:51:35 PM
I gotcha!!!, thanks ;D
Title: Re: New category
Post by: happylanding on August 23, 2006, 04:25:05 PM
What the hell is that?!?!? A kind of redbull strange things flying competition winner????????????????????????
Title: Re: New category
Post by: fireflyr on August 25, 2006, 02:33:22 AM
What the hell is that?!?!? A kind of redbull strange things flying competition winner????????????????????????
No my little Alpine Alice---it's merely a way some folks get thier kicks in the air (not me though) ;D
Title: Re: New category
Post by: Frank N. O. on August 25, 2006, 06:05:12 AM
LOL Alpine Alice. I got a reply from Chey on the subject when I asked if it looked like the above picture: "No, two-seater, side-by-side, high-wing pusher. No body, just framed, except for a small windscreen above the instrument panel since Turlock has lots of insect activity :D very much like this, except for the single seat and no windscreen" http://web.mit.edu/dtan/www/Quicksilver.jpg
Frank
Title: Re: New category
Post by: tundra_flier on September 07, 2006, 03:21:08 AM
OK, they ment Cambered wing then. As in Under cambered. On an undercambered wing the bottom surface is curved up towards the top surface. Generally a very high lift, but also high drag airfoil. Most of the early ultralights, and even a few modern ones, used single surface wings. Meaning they only had fabric covering on the top, the bottom structure was open. This is the most extream version of undercambering.
My ultralight had what was termed a 60% wing. it had a bottom surface, but only for 60% of the cord. Sort of a compromize between a single surface and full dual surface wing. My was the hang-glider with seat and engine style, usually called a "trike" these days. It was an Antares MA-33 with UFO wing. Sweet flying wing, very responsive and great glide. 45 to 50 mph cruise.
Phil
Title: Re: New category
Post by: Herk Fixer on September 17, 2006, 03:05:32 AM
-Helicopters, is the main rotor shaft, power turbine and gas generator physicly connected to each other or is the gas generator rotating freely supplying gas to the power-turbine which via a reduction gearbox supply power to the rotorshaft? Is the gas-generator and powerturbine on the same rotating spindle or are they not joined?
-Turbo-props, same question really?
-Are there any instances where the powerturbine is hanging on the same shaft as the gasgenerator? Not jets...
Hey ZAIZAI,
I noticed your question on turboprops hadn't been addressed yet, so I'd like to give it a shot!
Some turboprop engines, like the T-56 installed on the C-130 and L-188 Electras, have propellers that are driven through a reduction gearbox. Our RG has a 13:1 reduction ratio. The constant-speed prop turns at just over 1000 rpm (I don't have the exact figure in front of me right now!), while the core engine turns at an efficient 13000 rpm.
Other turboprops, like the PT6 described before, use a more direct drive for the propeller; via a turbine in the exhaust stream.
Most of my experience with engines is with pure jets; I was amazed at how much more complex the power package became when you bolted a propeller on the front!
Title: Re: New category
Post by: Baradium on September 17, 2006, 04:12:52 AM
Other turboprops, like the PT6 described before, use a more direct drive for the propeller; via a turbine in the exhaust stream.
Most of my experience with engines is with pure jets; I was amazed at how much more complex the power package became when you bolted a propeller on the front!
I don't know if a PT 6 is more direct drive for the prop. It's a "free turbine" design. After the last power turbine to run the compressor section there is an additional power turbine to run the propeller. After this there is an a gear box for the propeller. We can adjust our prop speed independant of engine N1 rpm (think engine core speed). We have a torque guage for each engine telling us how many ft/lbs we are putting through the prop. RPM range is 1400 to 1750 for the props. In this way the PT6 performs like a more complicated piston engine with regards of how you operate it.
We also actually have a gap between the last compressor power turbine and the output power turbine instead of a shaft that just spins inside another.
On a PT-6 you feather the prop when you shut the engine down, and it's not harmful to feather in flight or on the ground (providing you aren't trying to power the engine!) What happens is that now at idle you are running torque to the prop instead of almost none to just turn it at flat pitch at a relatively low speed. Wehn I was doing my flight training in the 1900 we feathered props in flight (with the engine running) to more accurately simulate single engine manuevers. You shouldn't do that with a piston engine, however! You probobly can't do it on a herc either from the sound of it.
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the caravan has the reverse thrust triggers on the throttle because as you force the oil into the prop hub to push the blades to a negative angle you must in crease the engine speed so you do not over temp the engine it is a reverse flow engine which means the air is sucked in the back of the engine and pushed through to the front same as a king air. to answer the question the prop lever only controls prop rpm and the mixture controls engine speed on the ground hi and low/ fuel metering for another word. It is agreat airplane to fly cruise at 160kts. downhill at 175kts to the MM and stop by the first taxi way. by the way it stalls dirty at 45kts. waaaaaaahooooo!!!!!!
The 1900 has a PT-6 as well (just a different version with more turbines and more power output), our reversers are detents on the power levers just like a standard jet. The caravan has triggers because cessna decided to do it that way. ;)
Here's what our power levers do: You have Idle, normally called "flight idle" Forward is more power like conventional. Behind idle you have a detent (lift the lievers up), and go back into "ground fine." Ground fine starts at a flatter than normal pitch and goes back into a slight reverse. Then you hit another detent to lift past to get to "reverse" range. Now, you aren't in full reverse yet, but at this point rpms start coming up and the prop goes further back in pitch until you get full reverse.
There is no "mixture" on a turbine. The condition lever just controls idle speed and fuel cuttoff (to shut down). Turbine engines control power output by fuel flow, just like a diesel engine. Increasing fuel increases power, decreasing decreases it. BUT, your throttle on a turbine doesn't control fuel flow. It controls N1 rpm governor setting. The governor adjusts fuel flow on its own to keep the RPMs there. Mechanical injection diesels actually use the same method. Mashing the throttle on one doesn't increase fuel directly, just governor RPM setting. ;)
-Ryan
Title: Re: New category
Post by: Herk Fixer on September 17, 2006, 11:47:36 PM
Thanks Ryan for the description of the PT-6! I had remembered the power turbine, but had forgotten about the gear box. On the Herk, with the RPMs constant, we use torque and TIT (Turbine Inlet Temperature) as our indications for power with 19,600 in-lbs of torque and 1077 degrees C TIT being the max.
Most of our engine-out procedures are done in the simulator. You don't see many props feathered for training, but there is the famous photo of an early model Herk flying along with three of the four feathered!
Title: Re: New category
Post by: Baradium on September 18, 2006, 12:19:14 AM
Thanks Ryan for the description of the PT-6! I had remembered the power turbine, but had forgotten about the gear box. On the Herk, with the RPMs constant, we use torque and TIT (Turbine Inlet Temperature) as our indications for power with 19,600 in-lbs of torque and 1077 degrees C TIT being the max.
Most of our engine-out procedures are done in the simulator. You don't see many props feathered for training, but there is the famous photo of an early model Herk flying along with three of the four feathered!
You use TIT instead of ITT?
Interesting. Sounds like your N1 is kept constant as well? On our engines the N1 is variable. We set power based on torque and ITT (Interstage Turbine Temperature). Torque and RPM is power output, but ITT is a limiting factor. N1 can also limit, but most of out engines don't put out enough power that they reach the N1 limit before temping out in ITT. ;)
Title: Re: New category
Post by: Gulfstream Driver on October 10, 2006, 09:28:12 PM
I guess my comment about feathering the prop should have been more specific to piston engines. I do realize that turbines are quite often feathered without damage to the engine. My multi experience has been solely in the Seminole, where if you feather the engine while pulling power, you'll do some damage.
Title: Re: New category
Post by: BrianGMFS on October 11, 2006, 06:23:45 PM
Our King Airs run at idle feathered all the time (PT-6) especially when we're doing ground power starts. the plug is at the intersection of the right nacelle and the right wing on the right side... about 4 feet aft of the prop... gets a little breezy there if it's not featherd when I'm pulling the plug.
Brian
Title: Re: New category
Post by: Baradium on October 12, 2006, 03:03:55 AM
Our King Airs run at idle feathered all the time (PT-6) especially when we're doing ground power starts. the plug is at the intersection of the right nacelle and the right wing on the right side... about 4 feet aft of the prop... gets a little breezy there if it's not featherd when I'm pulling the plug.
Brian
Our plugs are on the left side, but we don't start that engine with it plugged in. We can do cross generator starts (a kingair can't?) so we start #2 and then get unplugged and then start #1 (which is right in front of the plug). Not very nice of them to make you unplug with that engine running. ;)
