DHC-3 Otter VirtualCol - Piston Engine Fixes.

[BendyFlyer]

I really liked this model of the Otter and it had potential but had some serious bugs. I have played around with the piston engine variety (Wasp) and corrected a number of errors in the aircraft.cfg file with respect to the engine and propeller. I am now seeing the correct MP/RPM for this constant speed wasp and it now behaves correctly. No luck with the Turbine variety so far. Oh and don't install the update it rewrites the config files into a wierd way so that the piston gets turbine values and it screws up the indexes. Don't know what it was supposed to do. Just re-install the original oh and there is a set of modified VC textures about which are worth putting in.

I am quite happy now with the model and it goes as I would expect a Otter should. Still hard to slow down on water at min rpm or idle so just kill the engine, then it stops.

Anyway here are the relevant sections of the config file. Cut and paste them into your config for the f,g and s varieties in FSX


[piston_engine]
power_scalar=1.0 //Piston power scalar
cylinder_displacement=149.3 //Cubic inches per cylinder
compression_ratio=6.1 //Compression ratio
number_of_cylinders=9 //Number of cylinders
max_rated_rpm=2250 //3100 //2250 //Max rated RPM
max_rated_hp=600 //Max rated HP
fuel_metering_type=1 //0=Fuel Injected, 1=Gravity Carburetor, 2=Aerobatic Carburetor
cooling_type=0 //0=Cooling type Air, 1=Cooling type Liquid
normalized_starter_torque=0.3 //Starter torque factor
turbocharged=1 //Is it turbocharged? 0=FALSE, 1=TRUE
max_design_mp=38.5 //Max design manifold pressure, (inHg)
min_design_mp=10 //Min design manifold pressure, (inHg)
critical_altitude=8000 //Altitude to which the turbocharger will provide max design manifold pressure (feet)
emergency_boost_type=0 //0=None, 1=Water Injection, 2=Methanol/Water injection, 3=War Emergency Power
emergency_boost_mp_offset=0 //Additional manifold pressure supplied by emergency boost
emergency_boost_gain_offset=0 //Multiplier on manifold pressure due to emergency boost
fuel_air_auto_mixture=0 //Automixture available? 0=FALSE, 1=TRUE
auto_ignition=0 //Auto-Ignition available? 0=FALSE, 1=TRUE
max_rpm_mechanical_efficiency_scalar=1.0 //Scalar on maximum RPM mechanical efficiency
idle_rpm_mechanical_efficiency_scalar=1.0 //Scalar on idle RPM mechanical efficiency
max_rpm_friction_scalar=1.0 //Scalar on maximum RPM friction
idle_rpm_friction_scalar=1.0 //Scalar on idle RPM friction








[propeller]
thrust_scalar=1.0 //Propeller thrust scalar
propeller_type=0 //0=Constant Speed, 1=Fixed Pitch
propeller_diameter=9.08 //11.35 //Propeller Diameter, (feet)
propeller_blades=3 //Number of propeller blades
propeller_moi=59.0 //Propeller moment of inertia
beta_max=35.0 //28.0 //Maximum blade pitch angle for constant speed prop, (degrees)
beta_min=12.0 //Minimum blade pitch angle for constant speed prop, (degrees)
min_gov_rpm=1100 //Miminum governed RPM
prop_tc=0.1 //Prop time-constant
gear_reduction_ratio=1.2 //1.0 //Propeller gear reduction ratio
fixed_pitch_beta=0 //Fixed pitch angle of fixed pitch prop, (degrees)
low_speed_theory_limit=80 //Speed at which low speed theory becomes blended in (feet/second)
prop_sync_available=0 //Prop synchronization available? 0=FALSE, 1=TRUE
prop_deice_available=0 //Prop de-icing available? 0=FALSE, 1=TRUE
prop_feathering_available=0 //Prop feathering available? 0=FALSE, 1=TRUE
prop_auto_feathering_available=0 //Prop auto-feathering available? 0=FALSE, 1=TRUE
min_rpm_for_feather=0 //Minimum RPM for prop feathering
beta_feather=0 //Feathering pitch angle (degrees)
power_absorbed_cf=0 //Coefficient of friction for power absorbed by propeller
defeathering_accumulators_available=0 //Defeathering accumulators available? 0=FALSE, 1=TRUE
prop_reverse_available=0 //Prop reverse available? 0=FALSE, 1=TRUE
minimum_on_ground_beta=0 //Miminum pitch angle on ground, (degrees)
minimum_reverse_beta=0 //Minimum pitch angle in reverse, (degrees)

[falcon409]

I was more interested in the Turbine version than this one. I worked with a guy from the development team last year for about a week testing changes to see if it was possible to get it to function correctly. It finally did (sorta) and he promised that a final version with some "extras" would be forthcoming. . .none of that ever happened. To be honest, I don't think they have a very good grasp on proper FDE's. . .certainly this airplane was a bust. I still have it, but never flew it after the testing phase was completed. . .never was quite right.

[BendyFlyer]

Falcon, I agree re the Turbine variety and your comments re the FDE. The piston engine parameters were all over the shop, prop too big, RPM too high, cyl capacity too low, etc etc. These have all been adjusted and the power output and speeds are now in line with Wasp powered Otter. Goodness I even got so excited about it I tried my hand at a bit of painting and that was ok too (for a complete novice with the paintbrush).

Anyhow I was only interested in the piston engine variety, goes with my interest in aeroplanes of that vintage.

[ChrisJD]

Hi BendyFlyer. Thanks for taking the trouble to at least sort out the piston version - I think the turbine is a lost cause. I was one of the members last year that falcon mentioned about the problems & I am also waiting for the promised updates!
However, you mentioned VC updates for the otter - could you tell me where I can get these from? Much appreciated - I will be trying out your engine updates later. Regards, ChrisJD

[BendyFlyer]

Hi BendyFlyer. Thanks for taking the trouble to at least sort out the piston version - I think the turbine is a lost cause. I was one of the members last year that falcon mentioned about the problems & I am also waiting for the promised updates!
However, you mentioned VC updates for the otter - could you tell me where I can get these from? Much appreciated - I will be trying out your engine updates later. Regards, ChrisJD

Hi the VC textures were on flightsim.com file was called : vcol_dhc3_vc_texture.zip or do a search for Otter in FSX.

As a matter of interest you can also put authentic Wasp sounds by modifying the Ford Tri-Motor sound package (Available via the Tri-Motor website I think). That sound set contained a cfg and instructions on how to convert the sounds into a single wasp and they sound pretty good. Took a little doing but was worthwhile.

I am pretty happy with the outcome and will be recreating the Qantas PNG flights for my own fun. I thought the VCol original piston engine model was quite good visually although the textures were a little slapdash and well the modelling had/has some bugs but the main ones are sorted now for me, except there is no heading bug but you just get it straight and level and use the AP as a wings leveller hold the altitude. There are some water behaviour issues but they relate to the contact points and that is a world of angst trying to get them sorted and is just an FSX thing with amphibians and flying boats. It is acceptable and just a bit touchy that is all.

Still it will probably be awhile before any one else has a go at the Otter.

[falcon409]

I went back to my communications with Jose from VCol last year when he and I were attempting to get a handle on why the Turbine version was unable to sit on the ramp at idle and not eventually gain speed to the point of taking flight. It has been a year, as it turns out, that we worked on the problem (he adjusting the cfg file info and me testing) which eventually got to a point that it was much better. At that point he promised an update with some "extras" included. That never was released. So I've written to him again to ask what happened to the promised update and why his company has failed to even admit there was a problem (he told me at the time that it had never come up in the beta testing and that I must have something configured incorrectly).

I don't expect that anything will come of this obviously. My guess is that this was shelved and forgotten or simply dumped in the trash, otherwise we would have seen something in all this time. Since I didn't persist they figured they dodged a bullet and that was the end of it so they went merrily on their way to the next project.

[ChrisJD]

Thanks BendyFlyer - got the VC update. Will look for the Tri Motor later. ChrisJD

[gaab]

Thanks for the piston engine fixes. Will try them soon.

I completly second your comment on the virtualcol update. I had to check and fix each fltsim entry !
I took this opportunity to restructure the textures by creating a new directory for the panel only (using the CalClassic model).
It simplified the process of updating the vc textures and save some precious SSD space

Goodness I even got so excited about it I tried my hand at a bit of painting and that was ok too (for a complete novice with the paintbrush).

I like very much your skin. Will you share it ?

Gérard

[Portia911]

Thanks for posting these engine tweaks, BendyFlyer!

[Helldiver]

I really like the Otter BendyFlyer. Could you tell me where I can get it. It's a famous plane that has been overlooked.
Another rugged one is the Noorduyn Norseman.
There was four, painted Olive Drab, at Beverly airport after the war. Selling for $400 each. They stood unsold for almost a year until someone bought the batch.

[Portia911]

You can get it here, Helldiver:
http://www.pcaviator.com/store/produ...9&cat=0&page=1
or direct from VirtualCol:
https://www.virtualcol.com/v.php

. . . but you might wait for a sale (Father's Day; 4 July), as VirtualCol often reduce their prices (30-50% off).

[BendyFlyer]

Gerard sure happy to share it will see if I can upload it later today. Its not perfect but it is my first real repaint effort that seems to have worked.

Cheers

Bendy

[BendyFlyer]

Hi all, the Qantas DHC3 Floats skin has been uploaded and is in the FSX Civilian Props section of the library. Now it is an rar file type but I dont use winzip but it should be no problems to unzip and install.

The Qantas DHC3 Wheels is in the FSX Civilian Props Skins directory of the library.

Why the difference in locations, finger trouble sorry@!

[BendyFlyer]

Feel like I doing a rebuild on this bird. Anway here are the reference speeds for the Otter:

V liftoff 52 kts
V 50ft 62kts
Vclimb 65 kts


Vapp 90kts -70kts
Vat 60kts




Vfe 82kts
Va 110kts
Vno 116kts
Vne 159kts


Vstall F zero 65kts
Flaps Climb 58kts
Flaps tkof 52kts
Flaps land 47 kts


Max TKOF and LAND Altitude 6000ft

Cruise 30"MP/2000-2250 RPM*

Basically it comes of at about 55 knots, level then climb at 65 kts cruise 105-115 kts, approach 90 knots coming back to 70 knots for the last 1000 feet, 60 knots across the 300ft mark and coming across the fence 50kts.

A Bit like the Beaver only ever had two speeds, so for the Otter you will not go wrong using climb and approach 65 and cruise 105 and that is about it. You can finesse the rest later.

* The Otter Wasp engine with a Hamilton Standard propeller was what was called a variable pitch prop as opposed to a Constant Speed Unit where RPM was controllable from min to max by varying the blade angle. The Otters propeller acted as a fixed pitch propeller and that is the way it was flown you merely changed the throttle to vary the power and relied on MP settings. The propeller lever served to change the pitch from fine to coarse, which mean in the cruise you could bring the lever back and get a lower RPM about 2000 RPM and for all the other operations the propeller was left to give 2250 RPM. I think it is this combination (variable pitch prop) that is not coded for in FSX and caught out the designers and why the engine performance seemed so out of whack!

Yes and it handles a bit stiff but its got a big fat lifting wing and lifts a big load and it did not have a huge surplus of power to do all this but it had no vices and handles predictably and gently once you get used to it. Have fun!

[gaab]

Hi Bendy,

Thanks you for your repaints.

As you mentionned in your first post that you started from the original (not updated) aircraft.cfg, I though you could be interested to know what modifications were brought to the piston engine and propeller sections.

I am a long time user of WinMerge (diff program) from my past developper life and use it regularly to view what is bringing an update !
So, I re-installed the original package and saved a copy before applying the update.

Here are my findings

- the update allow prop feathering, but, so far, I don't see in the panel were to activate it !!!

- cylinder displacement (115.4 -> 130.7) and compression ratio (6.0 -> 6.8) were increased by the update : you are going a step further for the cylinder (149.3)

- propeller moi, pitch angle and reduction ratio were also updated, but not the propeller diameter.

- in the contact point section, as mentionned in another mod, the damping ration was increased, giving a much stiffer gear.

In the panel, a VOR has been replaced by an HSI and in the VC a set of switch was added (all coming from the turbo cab).
The Vcol_dhc3t_otter.CAB was updated to handle this new set of switches.

The internal models have been modified (to make the VOR/HSI substitution may be ???).

I can post images of the initial/updated piston and propeller sections if you are interested.

Gérard

[gaab]

Bendy,

Thanks to your post, I am flying again with this aircraft.
I had forgotten how fun it was.

Gérard

[BendyFlyer]

Gerard correct you will see that I decreased the max RPM tp 2250. The issue was the reduction gearing which was 3.2 in real life and that did not work in the cfg so I played with a number of gearings and found that the 1.2 gearing value now gave correct max RPM . The cylinder capacity 149.3 was corrected to the data given by P&W for the Wasp (My references were the P&W Manual a Type Certificate issued and a supplemental type certificate which provided values for the piston and turbine engined varieties. I also reduced the prop length to 9.8 that fitted to a Wasp Otter and Hamilton Standard Prop.

Anyway glad your enjoying this aeroplane again I certainly am with the single Wasp sound set it gives a nice low RPM rumble which is my recollection of flying these type of aeroplanes in the real world.

[gavinc]

Hi,
sorry to resurrect such an old thread but this way it keeps the fixes together.

If anyone (other than me) still flies the VirtualCol Otter they might find this helpful.

For reasons that I can't quite figure out I fly this plane a lot (despite its flaws), maybe it is because I spend so much time flying around the Pacific NorthWest.

One thing that has always driven me nuts is the behaviour of the amphibian on floats. If you start at a water runway it immediately bounces all over the place and crashes, if you try to land it porpoises and bucks.

Finally got fed up and went and took a look at the contact points. Comparing them to the default Beaver I noticed that the front and back float points were way too close together. Moved the back set closer to the water rudder and the behaviour on the water is much more civilised.

Try replacing your floats contact points with the following

//Floats
point.6=4, 6.119, 5.689, -7.580, 2200, 0, 0.0, 0.0, 0.35, 2.5, 0.30, 0.0, 0.0, 2, 0, 0
point.7=4, 6.119, -5.689, -7.580, 2200, 0, 0.0, 0.0, 0.35, 2.5, 0.30, 0.0, 0.0, 2, 0, 0
point.8=4, -12.875, 5.689, -7.080, 2200, 0, 0.0, 0.0, 0.35, 2.5, 0.20, 0.0, 0.0, 3, 0, 0
point.9=4, -12.875, -5.689, -7.080, 2200, 0, 0.0, 0.0, 0.35, 2.5, 0.20, 0.0, 0.0, 2, 0, 0

and see how she behaves.

thanks
Gavin

[BendyFlyer]

Gavinc, think it is a good thing to keep a thread like this going and the involvement of everyone interested and who use the VirtualCol Otter (Its the only VC and internally modelled one for FSX).

I cannot say I really noticed the on water behaviour issues but confess there were a few things that I did not like. I will revisit with your fixes. Amphibians and Flying Boats are difficult in FSX because of the ESP FSX's data engine, I have spent countless hours with some of JBK's flying boats trying to get them to sit correctly in the simulated water and I have to confess I have no idea how FSX treats them. The critical issue is the model and its datum points as the contact points have to fit the sections in the model, so that it sits in simulation like it was on water whereas in real life displacement, hull shape and hence buoyancy come into play as does water drag. So far FSX does this not to badly but as to how it is done I have no idea.

[BendyFlyer]

GAAB I somehow overlooked your 17th of JUne post or did not read it properly, would you like to post that information. I now have a and AIR file editor to help pick up and correct errrors so will have a look at all that as well. Only point I have is that the Otter (piston engine) variable speed prop was non feathering so there is no feathering control. In real life the pitch was controlled by oil pressure and if oil pressure was lost (Engine stopped or was damaged) they would courtesy of the counterweights go to a fine pitch and stay there. I have flown quite a few older aircraft with this type of propeller and while they gave you a little better cruise performance in real life they were not much better than a good fixed pitch prop.

How did the panel mods work out?

[BendyFlyer]

Update re cfg v air file. Well I have discovered that they did not include piston engine data in the air files for the piston engine versions. The data is there but for turboprop variable pitch props only, so it is a wonder that it works at all. Shows you the power of the cfg as far as FSX is concerned. Not sure if the data in re piston engines can be built back into the air file, perhaps but this is going to take a lot of work, i.e it might be awhile. It also goes part of the way to explaining why the turboprop version is such a mess as well. To be charitable I think somebody forgot what was what for a while and put it out anyway.

[gaab]

GAAB I somehow overlooked your 17th of JUne post or did not read it properly, would you like to post that information.

[/QUOTE]
No problem. In the mean time, I discovered you were aware of the August 2015 update.
Comparison between wheel piston aircraft.cfg (initial / udate of august).






Hope, it's what you were asking for ?

For checking updates, I recommand to use the OpenSource WinMerge (available on SourceForge). I could not live without !
For example, it helps me a lot to identify commun textures (for some FSX port-over) in order to save space using "texture.cfg" FSX possibility.

How did the panel mods work out?

I just identify that feathering was enabled, but did not modify the panel.

After reading the thread "VirtualCol Problem" were Falcon409 was describing his problems with the turbo version, I discarded it.
I should try it... on some nice airfied of Falcon409

Gérard

[BendyFlyer]

Hi,
sorry to resurrect such an old thread but this way it keeps the fixes together.......

....Finally got fed up and went and took a look at the contact points. Comparing them to the default Beaver I noticed that the front and back float points were way too close together. Moved the back set closer to the water rudder and the behaviour on the water is much more civilised.

Try replacing your floats contact points with the following

//Floats
point.6=4, 6.119, 5.689, -7.580, 2200, 0, 0.0, 0.0, 0.35, 2.5, 0.30, 0.0, 0.0, 2, 0, 0
point.7=4, 6.119, -5.689, -7.580, 2200, 0, 0.0, 0.0, 0.35, 2.5, 0.30, 0.0, 0.0, 2, 0, 0
point.8=4, -12.875, 5.689, -7.080, 2200, 0, 0.0, 0.0, 0.35, 2.5, 0.20, 0.0, 0.0, 3, 0, 0
point.9=4, -12.875, -5.689, -7.080, 2200, 0, 0.0, 0.0, 0.35, 2.5, 0.20, 0.0, 0.0, 2, 0, 0

and see how she behaves.

thanks
Gavin

Gavin that fix/change works fine, no porpoising on the water or other incorrect stuff that I can tell. Seems to sit more level. The floats are probably just still a little high out of the water compared to the real thing - here are a couple of pics of the Qantas Otter off Samarai Island in the lat 1950's, and they actually may be a little short in length when I eyeball the model but it depends I guess on the floats that were fitted. The Qantas Otters had there floats done by De Havilland at Bankstown in NSW but I can find no specific data as what float type was actually fitted.:



Thanks anyway makes it a little better again.

[BendyFlyer]

GAAB red the update changes - I would stick with the ones I put in. They are still way out for this engine and I would trust the P&W Manual more the VirtualCol sorry to say. They still don't understand this was not a feathering propeller but a simple variable pitch prop. So there is no feathering. On another level, feathering is not really necessary on a single engine aeroplane(except perhaps a turbine but that relates to the way blade angle is handled when the engine stops in a turbine which is very different to a prop control in a piston engined aircraft).

The drag from a stopped prop in a single engine aeroplane is basically a minor problem if the engine has stopped altogether and yes a slight change in the pitch angle will help the glide, so you would have coarse pitch until you were assured of landing in the emergency field picked then move it to fine pitch, that is all. For a multi-engine aeroplane it is however very important because of the drag factor and rolling moments and the amount of rudder authority you have to control the roll which results. classic example is look at the De havilland Mosquito it had a very very small fin and rudder as a consequence it had a single engine minimum control speed which was about 80-90% higher than its rotate speed, in other words you lost an engine below that speed you had no choice to shut the other down and pick a field to land in as the rudder could not provide enough control to overcome the roll/drag forces. Fin and rudder area is very important in cross wind handling as well, big fin good cross wind control, little fin poor crosswind control. One look at the Otter tells me it would have good crosswind handling capacity the lower dorsal fin is there to help directional control and overcome the resistance of the floats in a turn.

[gaab]

I contacted VirtualCol concerning the Otter.

I got an answer that they were working on a new update (no date of release).

Let's cross our finger...

Gérard