Twin Otter X: open issues

[flyfalcon 1]

I'll send you a PM how you can do that yourself. Ok?

Hi Private-Cowboy,

Can you send me a Mail?

friesen-flieger@hotmail.com

Thanks a lot

[Ken Stallings 1]

What are you saying? That i`m lying? This was done as a part of the airshow, as a deliberate action. If you don`t believe it thats fine. The Twinotter had a long and fast roll prior to takeoff building more energy than during a normal takeoff. The Airshow was held at Andøya, Norway. A F-16 also did a real slow flyby with extreme AoA, at 90 kts. Only a very few of the Norwegian F16 jocks are allowed to do this manouver. But I guess that according to you is impossible too? And last but not least a P3C did a 120 degree bank. No roll mind you.

Dude! Lighten up!

I never called you a liar. To be honest I had not even read your post when I wrote what I did. I was answering another person's question about doing single engine takeoffs in a twin-engined GA airplane.

Ken

[Ken Stallings 1]

Thanks for that Ken, nicely explained.

However...(and for Trond A's benefit) :wink:

I have a Twin Otter Manual (that's the extent of my real life experiences with her!) and it states that:

she'll fly good on one engine IF....

1. If an engine fails above VMC (64 knots in a Landplane) and a decision is made to continue the take-off proceed by maintaining heading by application of rudder and lowering the wing against the live engine as necessary (to a maximum of 5 degrees). Lower nose.

2. Advance power levers up to the T5, torque or NG limit, whichever is reached first.

It then posts the best climb speed on a single engine is 80 knots IAS with 10 degrees of flaps.

It's possible, but like you say not advisable.

Haven't tried it with Aerosoft's Twin Otter yet though.

Yes, if the engine is shut down on the takeoff roll with the plane already above Vmca then it would be safe to takeoff on one engine. But, with full thrust on the good engine, getting below Vmca will kill you.

What the manual says is true in terms of lowering the nose to maintain above Vmca. It is also vital to bank about 5 degrees toward the good engine side. This is because the good engine blows high velocity air over that wing. This produces slightly more lift on that wing than on the wing with the bad engine. The key is to bank so that you counter this roll force without using more rudder. More rudder (if available) would also do it, but would also increase drag on the airframe by exposing more of the side of the aircraft to parasitic drag. The key in a single engine situation is to maintain the most drag friendly condition.

One part of your extract from the manual does not make sense to me. You cannot lower the nose on takeoff run. Obviously once the nose gear makes contact that's as low as the plane will rotate down. What you quoted sounds to me like the basic inflight emergency procedure -- it is textbook actually.

The way to gain the speed on takeoff run is to use minimal thrust on the good engine and let the plane go past Vmca. In fact, on takeoff roll the pilot makes two speed calls -- passing Vmca and reaching rotate speed Vr.

Deliberately using minimal thrust on takeoff run can be done provided you have lots of runway and do a very careful takeoff density altitude computation. For an airshow demo I'm sure that is what the pilot did. He computed that he had enough runway distance to achieve Vr without using max rated takeoff power on the good engine. Therefore, he was able to counter the asymetric thrust with a combination of nosewheel steering or asymetric braking followed by rudder as it gained effectiveness.

Cheers,

Ken

[Private-Cowboy 3]

Hi Private-Cowboy,

Can you send me a Mail?

friesen-flieger@hotmail.com

Thanks a lot

I'll write you one. Sit tight...

[daytonite_andy 0]

What are you saying? That i`m lying?

Only kidding...'lower the nose' is in the manual Ken, and as you rightly say in the emergency procedures section. I'm only an armchair pilot so using the DeHavilland manual and flying in FSX is the only experience of such an event I'm ever going to get....fortunately.

Again, I appreciate your explanation Ken. Sounds like you are more than a flight sim buff, maybe a pilot in real life?

Anyway, hasn't this post gone off topic a tad?

[Ken Stallings 1]

Andrew,

No problem, I can tell you're joking. Nothing wrong with that.

I have no time logged in a Twin Otter, but I'd sure love to!

I am a pilot. I have earned an FAA Commercial Multi-Engine Land certificate. I've flown Piper Seminoles and Beechcraft Barons. I may soon log some time in an Aerostar.

I also have my Single-Engine Land certificate and own a Cessna Skyhawk, plus am a USAF Instructor Pilot currently flying the MQ-1B Predator. In sum I have about 2,500 pilot-in-command hours. I also used to be an Instructor Navigator and have logged a total of 6,200 hours in various C-130 types.

Cheers,

Ken

[Ken Stallings 1]

Here is a nice explanation of the concepts:

http://www.av8n.com/how/htm/multi.html

Cheers,

Ken

[Albrecht 9]

pbearsailor wrote:

Now for the pickly part: I've tried power changes up and down throughout the airspeed range. I still feel the pitch change on power change is excessive. The good news is that it's throughout the airspeed range, so as Mathjis said, may be easier to fix. I think overall pitch or elevator sensitivity is slightly too high as well (but I'll acknowledge that I feel that way about nearly everything I've flown in FSX). One of the really great characteristics of the Otter is that if you trim it in any attitude, it will stay there. That means it holds a well trimmed altitude without much input and holds a trimmed attitude on approach easily. I'm personally a trim fanatic and I'd make co pilots let go of the wheel for a moment on final to show me the airplane was properly trimmed. It should stay where you want it if trimmed properly.

Hallo,

couldn't find anything about this point in the list of open issues. I also find, that it is hard to make an exact trim.

regards

Albrecht

[pbearsailor 9]

Hallo,

couldn't find anything about this point in the list of open issues. I also find, that it is hard to make an exact trim.

regards

Albrecht

I know that they are working on this issue and that progress is being made.

cheers,

steve

[Albrecht 9]

thanks a lot!

regards

Albrecht

[Ken Stallings 1]

Don't want to appear like a broken record. I just went up and tried everything to replicate an accurate feathering, including programming one of my controller's button's with the FSX prop feather command.

The interesting thing is that once in a while I could get the prop to feather automatically once I pulled the fire handle, but without pulling the associated prop lever to the feather position.

However, other times it did not work.

The autofeather is supposed to simply automatically feather the prop if the RPM value falls below a specified value. The intent is to save pilots precious time during critical phases of flight so they can avoid having a prop hang up in a non-feathered position before the engine shuts down and the system won't allow a feather.

However, if the pilot pull the throttle and pulls the condition lever to the feather position, then the prop should immediately respond and the prop should stop turning just as soon as the mixture lever is pulled to the fuel stop position.

I'm really not sure what is going on with this. It seems very complicated. In the patch, can we please just have the condition lever pulled full aft work to put the blades into the feathered position?

Cheers,

Ken

[Finn 873]

Hi Ken

I have tried the autofeathering with my current 1.10 test files (DHC6-300 old style radios) and it worked like a charm.

Maybe something in the flightmodel has changed that makes it work, cause some values has changed due to our fix for the pitch with power change issue.

Pulling the fire handle should not feather the props, not in the Aerosoft version nor in the real twotter. All they do are extinguishing the fire.

If You had failures enabled, and an engine fire occured (the engine is on fire and probably damaged), then it might lead to a feathered prop.

But I also have to emphasize that I only tested it on the -300 old style British Airways version.

Please post a detailed describtion of Your procedure for trying to trigger the auto feather.

Kind regards

Fin "Wothan" Jacobsen

[Ken Stallings 1]

Fin,

I was flying the 600 model using the beta patch just now. It is still acting very strangely. In fact, I'm noticing something else. When I shutdown the engine and then attempt an air start or a ground re-start the ITT is remaining in the full throttle position even though I have the throttle in ground idle. This isn't merely a gauge issue either because if I release brakes while on the ground, with both throttles in ground idle position, then the re-started engine still pulls the aircraft. So clearly, the engine is actually acting as though the throttle is at the full power setting. This is also indicated with the engine sound. It sounds like it's in full power.

I just re-flew the same 600 model aircraft and noticed that even if I never engage autofeather, that the props do not respond to the prop condition lever in the full aft (feathered) position. To be honest, I'm not really sure I could even replicate what I did that one time to get the props to feather with the autofeather engaged.

The only thing I can replicate is that when I pull the throttle to idle, then the prop condition lever to feather, and the mixture to idle cutoff, even if I toggle the emergency fuel shutoff switch and pull the fire handle, the prop will not feather, but windmill.

I wish I had a better report for you. But unfortunately I'm not getting the responses one would expect to see.

Sorry,

Ken

[Ken Stallings 1]

OK,

I think I may have finally broken the code here and figured out what is the deal.

If I engage autofeather and pull the fuel lever to idle cutoff, then the system recognizes the drop in RPM below beta range and then autofeathers the prop and the engine shuts down. Now, with autofeather engaged and upon engine failure, this is how it should react once the RPM's drop below beta.

However, here is where I'm finding the anomaly...

One should also be able to do a manual engine shutdown and prop feather. And this is where I'm finding the errors, and apparently have been the whole time.

I should be able to pull the power to ground idle, the prop to feather, and the fuel to idle cutoff and obtain a manual engine shutdown and feather. This is what a pilot would do as a precautionary in-flight shutdown. He would do this for various reasons such as noting an abnormal fuel flow reading indicating possible thermocoupler failure. That's just one example -- not wanting to get in the weeds, just want to point out why a pilot might want to manually shut down and feather a working engine.

Now, I have not logged time on a Twin Otter, so if one of the actual pilots come in to say that one cannot shut down and feather the prop manually, but must rely upon autofeather, then I'll back off this observation.

If however, I am right in this observation, and it is due to the way the autofeather feature was programmed with the aircraft then we arrive at an interesting quandry. I am sure most customers would not wish to lose the autofeather operation, and frankly neither would I.

It would be ideal to have both a manual and autofeather working option.

I hope this helps clarify what is happening.

Cheers,

Ken

[pbearsailor 9]

I don't want to wade in too deep here as I've honestly not spent much time with the feathering issue, so I'll just try to confine this to the real world stuff.

I never flew an Otter with autofeather so we just had the old manual system of dead foot, dead engine. :shock: Have though flown many King Airs with the autofeather however and it should be the same.

The real autofeather system isn't going to shut the engine down. Recognizing a loss of torque, it will drive the prop to feather, giving the pilot time to do the clean up when things settle down. If the model is accurate, it should respond as if the prop is feathered, i.e. less drag, but the prop should continue to turn until the condition lever (not the prop lever) is cut off. With the fuel cut off with the condition lever and the prop lever manually moved to the feather position, the engine should stop and the prop should stop as well.

Without autofeather, like the one's I flew, it's "identify, verify, feather, and secure." Same as in a piston twin and the prop should slow and stop rotation after the condition lever is pulled to idle cutoff as part of the "secure" portion of the emergency drill.

Odd thing on the Twin Otter is it actually does better on one with 1 notch of flaps instead of clean. You rarely see that.

Just personal feeling here is that I realize Aerosoft's Twin Otter is not as complex as Digital's Cheyenne. I mostly just fly it, like I did the real one, and am happy with the lack of complex systems. On the Cheyenne, however, I know effort has gone into modeling systems, so for it I do expect all these things to work properly. I'm happy that they do.

cheers,

steve

[Finn 873]

Ken, You say that You areusing the beta patch! is that the 1.01 unofficial ?

You must know that I´m one of the beta testers and right now are using the upcomming 1.10 version (not fully finished yet, but we are close :-) )

I had no problem both feathering automatically or manually !

To stop the propeller inflight You need off course to both feather the propeller AND stop the engine, either with the fuel shutoff valves (the two switches on either side of the "engine fire" procedure, below the cautionlights), or by pulling the fuel lever all the way back.

Regards

Finn "Wothan"Jacobsen

[YoYo 49]

Two good news

[Ken Stallings 1]

Ken, You say that You areusing the beta patch! is that the 1.01 unofficial ?

You must know that I´m one of the beta testers and right now are using the upcomming 1.10 version (not fully finished yet, but we are close :-) )

I had no problem both feathering automatically or manually !

To stop the propeller inflight You need off course to both feather the propeller AND stop the engine, either with the fuel shutoff valves (the two switches on either side of the "engine fire" procedure, below the cautionlights), or by pulling the fuel lever all the way back.

Regards

Finn "Wothan"Jacobsen

Using the only patch available off your website.

I'm following the established procedures to feather the prop. As Steve says, it is straightforward textbook emergency procedures. All I can say is they are working for you, but not for me, and I am verifying that the prop lever is pulled full stop aft.

Ken

[Finn 873]

Ok

Then we might have fixed it in the upcomming 1.10 update, since with that it seems to work (at least on my system).

We are on track with the next update, but it takes longer than we first thought, due to the .mdl files that needs to be edited in order to rectify the "pitch with power change " issue.

Right now the -300 old style radio version is almost finished, but we still need to fix the other versions too.

Regards

Finn

[PPanPan 0]

Ok

Then we might have fixed it in the upcomming 1.10 update, since with that it seems to work (at least on my system).

We are on track with the next update, but it takes longer than we first thought, due to the .mdl files that needs to be edited in order to rectify the "pitch with power change " issue.

Right now the -300 old style radio version is almost finished, but we still need to fix the other versions too.

Regards

Finn

Hi again Finn. Not sure if my post on my problem tuning the 'old radios' should have been here or not. Assuming it should qualify as an 'open issue', here is the link http://www.forum.aerosoft.com/viewtopic.php?p=95223#95223. (Not meaning to push, but just wanting this issue to be added to the mix!)

Cheers

PPanPan

[Ken Stallings 1]

Ok

Then we might have fixed it in the upcomming 1.10 update, since with that it seems to work (at least on my system).

We are on track with the next update, but it takes longer than we first thought, due to the .mdl files that needs to be edited in order to rectify the "pitch with power change " issue.

Right now the -300 old style radio version is almost finished, but we still need to fix the other versions too.

Regards

Finn

OK, that sounds promising. Thanks for the efforts put into the updates.

Cheers,

Ken

[Finn 873]

With the "-300 old style radios" I didn´t mean fixing the radios, but issues like:

Prop wobble

Pitch with power change

DME

Marker beacon lights

Glide slope indicator

VC lighting

etc.

I think that the old style radios won´t be touched in the upcomming patch.

If the numbers don´t change, well then it´s because the radios are not powered.

Not realistic, but no big issue either in my eyes.

Regards

Finn "Wothan" Jacobsen

[Grahame Myers 0]

Will the prop rotation direction also be changed in the upcoming 1.10 patch?

Seen from the pilots view, at the moment they turn anti-clockwise, whereas in real life they turn clockwise.

This in turn means that the torque reaction etc is wrong.

I hope this is going to get fixed, along with all the other things already mentioned.

Regards

Grahame

[Finn 873]

Yep, prop rotation is on the list ;-)

Finn

[PPanPan 0]

With the "-300 old style radios" I didn´t mean fixing the radios, but issues like:

...

VC lighting

...

Will that include the odd way the autopilot is lit at night? When you toggle Shift L, the lighting on the autopilot seems wrong to me. I guess in the scheme of things, a minor issue and perhaps one to do with Microsoft as this gauge is from the default Maule?

Also, have noticed you can see the port wing nav light through the side panel of the cockpit (where the fuse panel is). Again, a minor blip but something you could look at?

I think that the old style radios won´t be touched in the upcomming patch.

If the numbers don´t change, well then it´s because the radios are not powered.

Not realistic, but no big issue either in my eyes.

Fair enough. I just hope if it's not a big thing to fix, maybe you can add it into v1.20 (if there is one ever) as for me this little issue is important. (I used to fly real world Grumman AA5s which had these style radios and I liked to tune them prior to battery on/start up).

Anyway, thanks for all your efforts - great work.

Cheers

PPanPan