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Post by Tom Goodrick on Jun 17, 2010 10:03:30 GMT -5
OK. I just emailed you the latest FD files. I did make the change to more drag requiring more power in cruise. But it still meets 180 KTAS and 300 pph/e because i adjusted the fuel flow to compensate for the additional power needed. Now it uses 71.0 % TQ or 1360 ft lb with 1501 RPM or 89.6%. I saw an oil pressure of 91 psi. That should be in the green for you. Let me know if it isn't.
I made another nice ILS to a smooth landing with 20 degree flaps, touching at 78.59 KIAS and -164 fpm with only a slight round out before touching. (I cut power over the numbers and made the second turn off at 18R KHSV.)
The full-flap landing at 80 KIAS described above will probably still work fine but it did require a more significant round-out for flare. But it touched down at 54 KIAS and -191 fpm. Obviously, this plane has a lot of flexibility.
Have fun.
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Post by louross on Jun 17, 2010 12:54:06 GMT -5
I have the folllowing files saved: cfg- Jn 13, 9:34 and air- Jn13, 9:34. If I have to choose between the Jn 13 and the current ones, the Jn 13 wins. The current files: at normal cruise power, in other words torque just below the red line and prop levers fully aft, it's way over 180ias, should be around 160ias. Just inside the FAF I had to bring power all the way back to idle in order to slow. Once the flaps were full down, there were 2 choices- power levers idle and stall or bump the power up a titch and accelerate excessively. Not useable. BUT, the oil pressure was okay. Fuel flow seemed okay, but it needs to be checked again- I was pretty busy trying to keep everthing stabilized for the quick flight. Engine instruments were essentially right on during the reversing procedure, but the airplane should have slowed sooner than it did. The 6/13 panel is useable with its noted problems, this one not. Using the BGA DHC6 with the Bradley panel from premaircraft. Flight: KORD 32R; right turn SE to 2000msl; right turn intercept final to 32R. Suggestions for another test: lr.
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Post by louross on Jun 17, 2010 13:06:16 GMT -5
Add'l: with the previous files, I flew a a flight of about 1 hr. and I think I flew a flight just before that of about 30 muntes. I don't recall any real problems with power/speed at any regime of flight; just maybe some fine tuning could be done later after correcting bigger problems. It seems like there were major changes in these files. (I did use a friend's computer as he (rather foolishly) had a payware, the FD's weren't all that bad, but should have been better. Everything else was worthless- sound, panel, etc.) lr.
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Post by Tom Goodrick on Jun 17, 2010 18:58:22 GMT -5
Something is screwed up. The files I sent you this morning were: aircraft.cfg dated 6/17/10 and the .air file dated 6/16/10. Those are the files you should be testing. They were emailed this morning at about 9:30 am CDT. It would not be unheard of for email to be delayed a few hours going a long distance.
Also, check you email spam filter. I have been sending a lot of emails with similar subjects. Some spam filters will kick those out.
Those old files are probably the ones that had a minimum beta that was negative. That was a poor idea that did not work once I checked it in normal flight operations.
I am surprised you found the oil pressure okay because i think now it is too low. I looked at the default B350 with the original panel (which I havew only in FS2002) and saw that it shows oil pressure with a green arc from 100 to 125 psi. My DHC-6 shows oil pressure below that range.
I'll have the set ready to send again with a fixed oil pressure if you can't find what I emailed this morning.
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Post by Tom Goodrick on Jun 17, 2010 19:40:36 GMT -5
Sorry, I guess I missed the word "current files". You only gave the dates for the old files, the last ones I had sent.
I am having a big problem understanding this sentance:
"The current files: at normal cruise power, in other words torque just below the red line and prop levers fully aft, it's way over 180ias, should be around 160ias."
The torque was somewhere below the red line and the prop levers were pulled full back.
1. If you cruise with the torque as high as it can safely be - "just below the red line" - i wish you would have told me that and perhaps what the torque value is at that condition.
2. Why pull the prop levers all the way back? I assume in the real airplane that does not cause the props to feather. In FS it does. I just used my TPower_Panel gauge to see what was going on and at zero position for the pro levers the props went to 1450 rpm which is the minimum flying rpm. But I can't set that without looking at my TPower gauge because the levers are not fully back. When I do pull them fully back, the props feather and go to 79 degrees beta giving a negative thrust of -214 lbs with all that power from the forward power levers.
The way the FD was set to work was that with 70 to 71% torque and 1500 rpm (prop levers ahead 20% from the zero point), you'd get 180 KTAS (at 163 KIAS at 7,000 ft) and 300 pph per side.
I can boost the drag so you get 180 KTAS at a higher torque setting. But you have to tell me what that high setting should be.
And you'd better accept a prop speed that is more reasonable than " levers full aft."
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Post by Tom Goodrick on Jun 17, 2010 22:58:08 GMT -5
I have revised the engine parameters in a way I never did before. I shut off the feathering so you can pull the prop levers all the way back without engaging feathering and I reset the minimum in-flight prop speed so that now you can get about 75.5 % or 1272 rpm. I also set -1 as the minimum on-ground blade angle so that, when you pull the power lever back all the way during taxi, you get a slight braking effect. There seems to be a beta mode in taxi as you have described it, Lou. It may not be all you expect but the prop rpm does vary with the power lever during taxi (with the prop levers fully forward).
I'll have another set of FD early tomorrow. Oh yes - it now takes about 97% torque to cruise with the prop levers pulled back. You get around 180 KTAS, depending on altitude. I can even see flying like that since you can use the prop lebers to get climb power though you have to reduce torque to descend.
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Post by louross on Jun 17, 2010 23:09:25 GMT -5
First: the flight problems- At idle or a tad above, oil pressure in the yellow. At a torque that's shows about 60-70% max, oil pressure is in the green. At higher torque, oil needle is right at the red line, but not over. I should be able to push torque to the max for climb and cruise. During climb I'm showing 140ias and 1500-200fpm- way excessive. I should be able to push max torque at cruise, or reduce from max by about 10% and be indicating about 160. I let it go to see what would happen, and ias builds to 195 and crash. In order to cruise I need the torque back to where it should be when descending down the glideslope with no flaps, in other words not much above idle.
Second: never seen anything like this before in FS- With the previous file you had sent, there was an occassional "shaking"; quick, short left/right jerks, if it were smoother you might mistake for turbulence. If I change views looking out different a/c windows then back to forward, then everything is stable. But now with the new files, the "shaking" could almost be described as violent. After several seconds, the torque and prop gauge needles make repeated sudden moves to the extremes of their range and then FS freezes.
"And you'd better accept a prop speed that is more reasonable than " levers full aft"."
Oh? Is that right? You 'd better configure your FS better, or correctly. " You assume". In the real a/c pilots know what they're talking about, but others don't. So here is this: Pull the prop levers back sets them at the low prop setting- minimum rpm. In order to feather the prop, you have to over-ride a gate, and then move on into the feather position. That is to prevent inadvertant feather when the props are pulled back, or full aft. In addition, it's the same with the power levers- pull them all the way back, you get idle, not reverse thrust. Reverse thrust requires moving past a gate, engaging rev levers, or some other designed method. The twin otter uses the some other desing method method. "in FS it does". Unfortunately, apparently your system works different. Anytime I've pulled the prop levers full back they've gone to the low rpm position. This is FS9, I don't specifically remember much about FS2002 or FS2000. So in order to actually feather, I have to drag the prop lever on back into the feather position with the mouse. And this works for the DHC6's I've used, the default KingAir, a B1900, and the Frolov Dash 8, and others. Other a/c programs, such as calclassics DC6's and Olsen's DC3C have a completely different method for feathering, as does the real airplane. Now I did the level flight at 3,000 msl, which is a legit altitude, climbing to 7 wouldn't make much difference. !80 TAS, 160 IAS, 300 lbs/hr/engine are the numbers with very slight variances.
I'll reread this at some point tomorrow, but I've been burning the candle at both ends and am currently flying out of rig. lr.
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Post by Tom Goodrick on Jun 18, 2010 9:12:29 GMT -5
I have just sent another set of FD to Lou. This one allows you to pull back the prop levers all the way and not get feathering but you will see prop speed of about 75% or 1275 rpm. There's a lot more parasite drag in this set. You'll need about 97% torque to cruise. These changes should all be in the right direction.
In most FS aircraft I have seen, pulling the prop levers all the way back gives you feathering. You don't want that while flying as you have said. There is no gate in FS. But now you will see that the prop levers stop before reaching the feathered position. When practicing engine-out procedures, pull the prop lever back but leave a slight torque on the bad engine.
I found this very easy to land with any amount of flaps. Maybe that's just from the parctice I have been getting.
The reason it took me a few years to find that I could reduce the prop rpm considerably is that the minimum governed rpm is in N2 units that are 17.6 times as great as prop rpm units. Now it would be no problem to go lower if needed.
I hope you will check out all aspects of flight with this set of FD. I'll wait for several days before considering mods. Inicdentally, Lou, the relation between torque and rpm you describe for the PT6 is just a process of trying to conserve constant power. This would be noticed in the fuel flow. Unfortunately, FS does not work this way.
I am sure Lou knows this but others may want to know that when flying with flaps down on final, you are close to the backside of the power curve where adding power when slow just makes you go slower unless you have enough altitude to drop the nose a bit. Trying to maintain minimum flying speed with 20 or more degrees of flap can be dangerous (near gross). The changes made recently have only made this problem worse. But you can get a nice transient flare to a slow touchdown. Just don't start it too high.
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Post by louross on Jun 18, 2010 11:51:48 GMT -5
Now this is pretty nice. Short test flights. Take-offs and landings, normal and STOL. Short cruise at 2000 and short cruise at 8000msl. A NEW plus for the Twin Otter- props will set at 75% and can be moved forward in 1% increments to 80% (of course, they'll go to 100). A NEW plus for the Twin Otter- can do the most realistic STOL I've seen wih this a/c in FS: Props 100% 20% flaps and brakes set Controller FULL BACK Stabilize torque at about 200 lbs Push torque to max and release brakes Lift Off around 55 kts Controller forward, accelerate to 80 and flaps 10. THAT is a STOL take-off. mmmm, below Vmc? You gotit. The STOL was at around 11,300 lbs GW. You can practice STOL landings real well on 32R at KORD because you want to turn off on the parallel taxi way just before 27. At 2000msl the fuel flow was 250lbs/hr, at 8000 flow was 270 lbs per hr: should be right at 300. Props were 75% and indicating 160-162kias. The variance was the torque- 360lbs at 2000 and 440lbs at 8000. Fuel flow of 300 at either altitude and torque at 470-480 would be more accurate. The other torque settings seemed quite close as I remember them. Oil pressure was always a bit high with power applied. Idle was ?. Surge coming out of reverse- careful if the runway is short. If that can be tweaked, great. But at this point don't let anything else change. Otherwise, leave it as it is. You choice. Will fly some more later. In the mean time- Congradulations! lr.
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Post by Tom Goodrick on Jun 18, 2010 15:25:18 GMT -5
I might have a fix for the shakes but it stiffens the aircraft on all axes. I need to back off on the stiffness until just before it starts shaking. That mainly occurs when you use Instant Replay because of the coarse timing. But i don't like the shaking either.
I did see 300 pph when I was pushing for 180 KTAS. I had a higher torque. But, if you still see a low fuel flow when doing your normal cruise, we can fix it.
For now, I have been flying the Twin Otter too much. I put similar adjustments on the Beech 350 and made a nice approach through broken clouds to Asheville, NC. Then I landed with wheels firmly up.
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Post by louross on Jun 18, 2010 16:05:55 GMT -5
That's great- saves on expensive tires. lr.
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Ed Burke
Member
Healthy living is fine, but it's having fun that keeps us going!
Posts: 433
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Post by Ed Burke on Jun 18, 2010 17:59:51 GMT -5
Sounds great fellers, where can we buy one?
Ed
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Post by Tom Goodrick on Jun 19, 2010 9:07:38 GMT -5
I need a couple of more trials with intermediate MOI factors. Then I'll send you a copy, Ed, as well as to Lou. We use the BGA model from Bill's BGA FS2004 hangar. I use a DG panel and Lou uses one from a commercial model.
The shake only occurs occasionally so it is hard to know when it is "fixed."
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Post by louross on Jun 19, 2010 11:21:49 GMT -5
This is my first chance at the computer since Ed's post, so I'll respond. Once you have the files, I would suggest the following in order to give you the most realistic Twin Otter I've found for FS9- although I've tried out many, there are some that I haven't. On this note, if you really want a nice one that's as real as I've been able to find, I do hope you didn't lose any money on the purchase of the one for FS9 as there are free ones that are better. This that I describe is freeware, as is the one I'm using- I've never had the pay Otter. Here are the nuts and bolts of it: Download and install the BGA DHC6. Go to premaircraftdesign (www. ? I'll get the site if you don't have it) and download and install the Bradley DHC6 Twin Otter (for FS9) version 4.3, 10.5 Megs Panel/Gauges Package and the New Sound Package 6.7 Megs. : both downloads appear on the Bradley Air Services download page. Install the entire Bradley package. Go to you BGA folder in FS and inside the a/c folder eliminate the panel and sound folder. Copy or cut and paste the Bradley panel and sound folders (inside the Bradley a/c folder inside FS9) into the BGA folder. Eliminate the Bradley a/c folder inside FS. Add in the cfg and airfiles provided by Tom Goodrick. While flying this a/c, remember to keep the blue side up. ;D I think it was yesterday I posted the real world procedure for STOL take-off, which, by the way, works in FS. You will lift off before Vmc. Immediately push the nose down and be ready to start the flaps up to 10 at about 75kias, then UP at 85 ,90 whatever, and props back to 75-80%. I'll post real world procedures for normal and STOL ops if wanted. You'll find this particular panel to be quite accurate according to the real thing, very good views, and a great sound package. One sound has not been duplicated and I don't know why, but there is a very unique sound when taxying in beta, that I've never heard in any other a/c including King Airs. You can hear the sound in certain videos, I'll try to find one and you will definitely hear it. In real world, brakes are not necessary during taxy/maneuvering, only used at the last instant before actually stopping- it is very easy to move in and out of beta, and in doing so the only chages (other than sound) are prop rpm and taxi speed. As a matter of fact if you barely move into beta, I prop rpm doesn't change, only blade angle- might be true for all beta ops in this a/c, just can't remember. That was a long time ago-what- 4 decades?. Now, I do remember one of the ticket agents, ohh, very fine details, but can't remember her name. lr.
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Post by louross on Jun 19, 2010 12:12:04 GMT -5
Here what I was looking for- Go to youtube and you have to search "twin otter crash" which is labeled as "Twin Otter Crash" by REVPILOT September 28, 2008 Nasty failed take-off on Nothern British... .
Look at the seconds counter, lower left part of the video: at seconds numbers 9, 13, and 17 you will hear him enter beta for about 2 seconds, at the 17 mark he's in beta a second or two longer. There is no reversing in this video nor is there any evidence he even begins to enter reverse. Now you know the sound. Note he holds brakes and developes max power before releasing the brakes. Then he proceeds to crash. Why? Know idea. No wind problem. Adequate runway. Maybe, or maybe, or maybe, or.... How long is your piece of paper? I'll fill it with maybies. I did note an interesting point. Take another look- at the highway, looks like a long enough stretch, 2 lanes, smooth and flat. Make an easy take-off. lr.
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