cvfd1399 0 #1 December 8, 2004 I have a few questions about the Otter since I am a Otter baby. I am refering to a regular otter with the long nose(-300?) that is used for jump ops. What rpm range does the 3 blade prop on a regular otter normally spin at? I was sitting right next to the right prop on a load the other day and thought how messed up it would be if for some reason the prop broke apart and came throug the body into the cabin. How much fuel is it capible of holding in both tanks? Do you use both tanks equally at the same time, or is it seperate. How do you keep a C.G.? Do you use a bit in one, then use a bit in the other or does it not really matter. How much needs to be kept in reserve? How many DZ's have the little compartment in the rear open for people to sit. At a boogie I heard about a guy that would climb in the back where he had a sleeping bag and a pillow and took a nap on the way to alt. How bad is a blow out on the front or rear tires on takeoff. It seems that if it happened near take off roll speed you could just power through it since most of the weight is being taken off the tire. I am sure that it is flown by cable is there any sort of back up? What is the clicking noise when it starts to fire off? is is some sort of glow plug, or spark plug? I can see how a turbine stays running at high rpm's, but how does it start off. I know there is a starter, but it does not spin it up that fast. Like on a 4 stroke motor, you only need that 1 explosion every 3 turns to keep things going. It sems that in a turbine that a "power stroke" needs to be occuring constantly. I am used to the 4/2 stroke/rotary theory that a power stroke happens at one time, and it is hard to comprehend that in a turbine that "power stroke" is constantly occuring. I understand there are no pistons only compressor blades and fuel injectors, but how does it contain the combustion? Is it in something that resembles a turbo housing on diesels? What is the max air speed in a dive(140knots)? Like in free fall is there anything you can do to cause drag in a dive other than having speed braked installed(can you do that on a otter) turn the blades full sideways, flaps? Also I understand it that feathering the prop means turning it lenthwise so that it produces the least drag to the relative wind, what is the term for turning them so that they are flat if you look at them from the nose. Can you turn them around and force air forward a bit to slow you down. I always thought the pilots did this, b/c it makes a different sound, but I now think that that is just the sound it makes when it goes from the "power" setting to the "feathered" setting. Quote Share this post Link to post Share on other sites
nacmacfeegle 0 #2 December 8, 2004 "ok I think that is all I got for now" Are you sure?-------------------- He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson Quote Share this post Link to post Share on other sites
IanHarrop 41 #3 December 8, 2004 My favorite picture of "Twin Otters""Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy Quote Share this post Link to post Share on other sites
cvfd1399 0 #4 December 8, 2004 Ya bastards Answer my questions Quote Share this post Link to post Share on other sites
IanHarrop 41 #5 December 8, 2004 QuoteYa bastards Answer my questions I don't know no stinking answers! Planes and pilots are like cabs and cab drivers. They just get me to where I want to get out. I think what really gets those big things in the air is MAGIC. It just doesn't make sense that such a big thing with a couple of fans on the front and some guy with a hangover at the controls gets into the air!"Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy Quote Share this post Link to post Share on other sites
cvfd1399 0 #6 December 8, 2004 No I lied.... Why when they shut down a load we have to wait a minmum of 20 minutes before we start it up again? Does it have to cool down before so there isn't a "cook off" when you try to start it again, or is that just a DZ/DZO thing that if you are going to go through the trouble of doing it might as well make it 20 minutes? Also I heard that turbines do not like to be shut down does it harm them a little bit over time besides the obvious heat/cool stresses that occur to metal? Quote Share this post Link to post Share on other sites
mr2mk1g 10 #7 December 8, 2004 QuoteAlso I heard that turbines do not like to be shut down Best I know is that it costs $$$ to start them up again which is a high wear activity adding to the $$$ of servicing… but take that as being next to a whuffo answer. Quote Share this post Link to post Share on other sites
diverdriver 5 #8 December 8, 2004 QuoteYa bastards Answer my questions Are you a pilot? "Regular Otter" refers to one that has PT-6-20 engines on it. The pull 550 SHP max on T/O. "-300" Otters are super otters that come with PT-6-27 engines on it. It does have the long nose and many have long range wing tanks. The normal tanks are in the belly. Yes, you are sitting on them. No fuel tricks are needed to keep it in balance. Just fill them evenly. The max fuel in the belly is (from memory) 1200#s in the front tank and @1400 #s in the aft tank. When topped off you want to burn down the aft tank for about 30 minutes with crossfeed to even them out. The prop turns at about 1950 RPM for takeoff (again from memory). What else did you want to know?Chris Schindler www.diverdriver.com ATP/D-19012 FB #4125 Quote Share this post Link to post Share on other sites
cvfd1399 0 #9 December 8, 2004 I wonder why it cost money to start them up, does it use alot of fuel to start them up compared to flight idle(hellicopter term does it still apply)? Quote Share this post Link to post Share on other sites
cvfd1399 0 #10 December 8, 2004 No I am not a pilot. But the people reading this were probbaly wondering so that they would never get near my aircraft lol. I have been just wondering little trivial things about Otters. Quote Share this post Link to post Share on other sites
diverdriver 5 #11 December 8, 2004 QuoteNo I lied.... Why when they shut down a load we have to wait a minmum of 20 minutes before we start it up again? Does it have to cool down before so there isn't a "cook off" when you try to start it again, or is that just a DZ/DZO thing that if you are going to go through the trouble of doing it might as well make it 20 minutes? Also I heard that turbines do not like to be shut down does it harm them a little bit over time besides the obvious heat/cool stresses that occur to metal? You can wait to start a PT-6 but you don't have to. This "hot start" issue has more to do with Garret engines than Pratt & Whitney. But this "rule" is carried over to all turbines. What I normally do is motor the engine until the T5 temp is down to about 120 and then start. They start just fine. The clicking you hear is the ignitors popping. Shutting down an engine is not the problem. It's the starting that wears on the engine. The start always heats up the parts more than continuous operation. Now, if you are starting it from cold there is a greater thermal increase range it has to go through. That is why you must wait at least 2 minutes before taking off so that the temps can stabalize through the engine before "putting the coals to it".Chris Schindler www.diverdriver.com ATP/D-19012 FB #4125 Quote Share this post Link to post Share on other sites
IanHarrop 41 #12 December 8, 2004 here's a couple of places to check out: History: http://www.exn.ca/FlightDeck/Aircraft/Milestones/dhtwinotter.cfm actual characteristics: http://www.aoc.noaa.gov/aircraft_otter.htm If you've got MS Flight Sim you can even fly one http://www.abacuspub.com/fsd/catalog/s541.htm"Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy Quote Share this post Link to post Share on other sites
cvfd1399 0 #13 December 8, 2004 Which flight sim is that 2003? I will go pick it up tonight. Quote Share this post Link to post Share on other sites
IanHarrop 41 #14 December 8, 2004 Check the link to be sure but I think it said that it works with both 2002 and 2004"Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy Quote Share this post Link to post Share on other sites
cvfd1399 0 #15 December 8, 2004 Thanks alot I knew you had to be lurking around here today. I took a observer ride in san marcos for the hell of it b/c I had always jumped out, but never rode it down. That was a ride like no other. If I remember right we dove down until it reached what I thought was 140 knots the line was near red, then we leveled off, bled the speed down, then dove again! It was fun plenty of 0g's. Quote Share this post Link to post Share on other sites
cvfd1399 0 #16 December 8, 2004 Cool I have the combat flight sim already. I am going to pick up the 2004 tonight on the way home. Thanks Quote Share this post Link to post Share on other sites
IanHarrop 41 #17 December 8, 2004 Yes today I lurk.... need to get my ass in gear though... have fun with Flight Sim. I do, although I've never tried the Twin Otter mod."Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy Quote Share this post Link to post Share on other sites
nacmacfeegle 0 #18 December 8, 2004 "I am sure that it is flown by cable is there any sort of back up?" You are normally wearing it.-------------------- He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson Quote Share this post Link to post Share on other sites
racer42 0 #19 December 8, 2004 Pratt & Whitney and GE both have pretty cool websites explaining the basic nature of turbine engines.L.A.S.T. #24 Co-Founder Biscuit Brothers Freefly Team Electric Toaster #3 Co-Founder Team Non Sequitor Co-Founder Team Happy Sock Quote Share this post Link to post Share on other sites
koz2000 1 #20 December 8, 2004 The reason it doesn't look like it's running that fast is because it has a gear reduction box between the power-turbine and the prop-shaft. The N1 turbine speed is about 19000rpm at 100%. A interesting fact is that the PT6 prop shaft is only connected by air to the power section. You can actually start a PT6 w/ someone holding the propeller and it won't move. That's also why you get a lag when you apply power to the engine. THe original PT6 did not have a reversible prop, but since then all variants have had reversers. The -20, -21, -27, -28, -34 , -41, -42, -67, etc.... all can move the prop 8 to 11 degrees past beta (zero thrust ) to achieve reverse. Quote How bad is a blow out on the front or rear tires on takeoff. It seems that if it happened near take off roll speed you could just power through it since most of the weight is being taken off the tire. It's worse to blow a nose than a main tire. however most blowout occur on landing not takeoff, since the tire is going from 0 to 60-80 kts instantaneously.. QuoteI am sure that it is flown by cable is there any sort of back up? That's why you have a parachute....______________________________________________ - Does this small canopy make my balls look big? - J. Hayes - Quote Share this post Link to post Share on other sites
cvfd1399 0 #21 December 8, 2004 [crowd laughter] [/croud laughter] Quote Share this post Link to post Share on other sites
cvfd1399 0 #22 December 8, 2004 So beta is when it is like a giant blender, prop looks thin when viewed from the wing tips, and feathered is when it is a giant windmill props looks thin from when viewed from the nose. After the AC was tied down last weekend I took a few minutes looking at the prop. It was alot thinner and a lighter sounding matereal than you would expect. I rocked it back and forth a few times and you could hear the gears meshing. The small dings, and paint chips on the props are generally caused by rocks and debris kicked up on TO and Landing, or is that marks caused by hitting ice/hail? Can an otter get vertical if you build speed then turn it straight up, or will it stall before you can get it there. Assuming light fuel, and no load. Can they do barrel rolls, or back loops? Quote Share this post Link to post Share on other sites
nacmacfeegle 0 #23 December 8, 2004 Thank you, thank you very much. I'm here 'til Thursday. Try the veal.Google will answer many of your questions, and some even you haven't thought of yet, search also for DHC-6. By way of compensation for my misdirected mirth, here's a pretty cool shot for serious otter fans.-------------------- He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson Quote Share this post Link to post Share on other sites
cvfd1399 0 #24 December 8, 2004 Yea I did all that, just wanted specific skydiving stuff. I built a DHC-7 model, they make a single otter model too, cant find a twin otter the bastards that make both models left her out I was going to paint it in the kinghts paint scheme after seeing their -7 on the internet(pic attached) Quote Share this post Link to post Share on other sites
Zep 0 #25 December 8, 2004 Don't know if it's just me, or maybe others have thought about it When your sitting next to the prop an watching it out of the window how many of you have thought about what would happen if it came unglued I know I have. Also is thier any reason that the prop rotates anticlockwise (looking from the front)? Gone fishing Quote Share this post Link to post Share on other sites
