Twin Otter trim setting

[mhlarsen 4]

How does a real Twin Otter pilot know his exact trim setting (pitch)?

Using tool tips (cheat ) in FSX gives you a number, but a real pilot do not have tool tips.

Thanks

Michael

[Guest Hodge001]

Hi

Firstly my apologies to all the real pilots here ir this is incorrect, as I only fly in the FS world where I can do the least harm.

Now Im not sure if this holds true for all earlier aircraft, but as far as I know (see above) the trim wheel would have a usually white paint mark on it to show its relative position to the actual trim tabs, for example neutral trim white mark in the middle or directly up, it was then a matter of the pilot adjusting the trim wheel until the aircraft was stable, and noting the position for the aircraft at that loading and for that particular phase of flight, so he could on later flights have a good idea where the trim should be, but that was when pilots did not even have access digital watches though.

Also I just remembered the Twin Otter has a trim setting anunciator on the main panel to tell you if you do get things out of whack

Jim Hodkinson

[mhlarsen 4]

Thanks Jim for the quick reply

I have a few more though:

1. The checklist tells me to start right engine first and then left engine, but no matter what I do the start switch always goes left?

2. During first engine start Oil pressure rises and also Ng, then I set Fuel lever on. Now, starting second engine Oil pressure rises

somewhat, but Ng does not move at all, until I set the Fuel lever to on. Does this reflect the real-life engine instruments?

Happy New Year

Michael

[Guest Hodge001]

Hi Michael

The engine select had been an issue for some, and was covered in the forum previously but my failing memory cant remember what the outcome was, and to be honest it has never really been a show stopper for me anyway, but a search through previous posts for the Twin should be able provide the answer to the select switches that my grey matter can’t.

As for the engine reading during start up, I would have thought that the start up procedure would have given the same or similar instrumentation readings for both engines, and to be honest I have never noticed this on the Twin Otter, shows how much attention I give to the instruments during start up, but I think that this one is for a real turbo aircraft / engine operator to answer.

Sorry I couldn’t give a definitive answer, but I’m sure that somebody will know the correct readings you should be getting, and the next time I fire her up I promise to pay more attention.

Take care, and have a great new year.

Jim Hodkinson

[Snave 466]

It represents real-world limitations of the simulator. As for the click issue. I'm not in front of my Twotter computer at the moment but have you tried left and right mouse clicks?

[Albrecht 9]

How does a real Twin Otter pilot know his exact trim setting (pitch)?

Using tool tips (cheat ) in FSX gives you a number, but a real pilot do not have tool tips.

Thanks

Michael

Hi Michael,

here is a picture of a real Twotter trim panel:

Please login to display this image.

Looks like there is a scale.

Albrecht

[Snave 466]

lick of paint and you can put a mark on anything. But as to what relevance this might have when your picture doesn't show the load out back is open to question. Trim is dependent on CG, airspeed and other factors. That's why it's a dynamic process and normally requires pilot setting. The Twotter does have a trim interlink with the flaps whcih reduces the trim moment with application or retraction of flaps, so as long as the aircraft is in trim at Vr it should be relatively easy for the simmer to stay in trim thereafter. As you can't see the trim without Track IR anyway, it is a bit of a moot point!

[mhlarsen 4]

I have recently bought a Twin Otter 300 flight manual and I quote from the Takeoff checklist:

a. Trims - Set.

Note

The elevator trim pointer should be aligned with the forward edge of the

take-off range mark with aft cg and to the aft edge of the take-off range

mark with forward cg. The rudder trim pointer should be aligned with the

takeoff index.

I can not see this clearly in the Aerosoft instrumentation of the Twin Otter.

And as Snave points out the trim settings can only be seen with TrackIR and it can therefore only have questionable influence on this Aerosoft flight model.

One could rightfully state though, that the trim settings for a STOL aircraft should be critical for performance in an environment demanding STOL performance.

Michael

[bumprock 9]

Though not a pilot, I have spent a lot of time in small aircraft including easily a hundred small hops in Twin Otters, and most recently in Cessna 402's. Due to my interest in flight, I have always paid close attention to what the pilots were up to.

What is interesting is that some pilots fiddle a lot with the trim and others seem to set it once for each phase of flight and then, rarely touch the wheels or knobs again. It is also important to point out that they are very coarse and not fine controls. Normally they just reach down and give them a few turns in one direction or another. The only time I recall seeing a pilot or co-pilot actually look at the trim controls or read-outs is when they are doing their pre-take-off checklist. Other than than it is all by "feel" ... more art than science.

Though I would gladly defer to any of our experienced pilots out there.

Bump

[Snave 466]

You've hit the nail on the head, Bump.

Trim is a `feel` factor adjustment - what the pilot feels is more or less resistance in the controls, and dials out the need to maintain a constant - and therefore tiring - pressure to retain the desired flight attitude. Some pilots can bear the force and so trim less, others have a feel for what the aircraft will do as a result of the changes they are about to make, so can trim less. Mostly though, electric trim buttons mounted on the yoke or stick mean you barely notice that they are adjusting anything. The Twotter doesn't have electric trim, and FSX doesn't have the feedback loop needed anyway (not even the basic force feedback provides it) so that's why the point is moot - and why my alternative technique is the one to go for.

Pre-takeoff checklists cater to the need to set a `base level` prior to take-off, but are NOT the `correct` setting as this is, as I said before, derived from many factors. Even without correct trim, the real Twotter will fly perfectly well, so Michael is fundamentally incorrect in his assertion that trim settings are crucial.

To repeat what I also said before, trim is NOT a control surface, it's a force (de)multiplier so if the pilot is happy bearing the strain it makes no difference to STOL or any other kind of takeoff. Only a very few aircraft have ever been put into service where the incorrect trim setting can actually make the aircraft uncontrollable (the Westland Lysander being one, which is why the new FS Addon version is so interesting, as it gets this totally right).

FSX gets it totally and utterly wrong by making trim act as a secondary aerofoil which accentuates or reduces the control surface effect so you can get to the point where you can't apply enough `up` elevator to prevent the aircraft nosing down. If this is happening in FS it indicates poor modelling by the designer, who should be taken outside and summarily executed.

The Twotter makes no such mistake and the developers may be allowed to live, so if one uses the `5` Numpad key judiciously (that needs no explanation as it's a default control) then at Vr applies the level of trim required to adopt the desired attitude the aircraft is in trim and further changes can be made by reference to the horizon.

Hope this helps.

[mhlarsen 4]

Pre-takeoff checklists cater to the need to set a `base level` prior to take-off, but are NOT the `correct` setting as this is, as I said before, derived from many factors. Even without correct trim, the real Twotter will fly perfectly well, so Michael is fundamentally incorrect in his assertion that trim settings are crucial.

Snave,

I'm actually happy to be incorrect about the importance of trim settings on the Twotter, as I was beginning to suspect that Aerosoft left out an important part of this fine aircraft in their development.

Thanks

Michael

[Snave 466]

Michael, it's not you that's incorrect, it's the overstatement of trim effect and actually the whole damn trim system in FS!

Spend ten minutes using force feedback with FS Force 2 and FSX is a different animal, but even FSForce can only deal with what it can adjust using DirectX so what you get is force physically felt on the controller, which is nice. But the actual adjustment of the force involves the controller returning toward or away from centre. Still not `right` but a big improvement on the faux system we're lumbered with by default.