TwOtter Unwanted Ground Handling Issue (TOUGHI) ^^

[HBE66 2]

hi everyone!

im having a little issue with the twin otter. after starting the engines, i want to release the parking brakes for pushback.

but although i have the power leavers on "0" (ZERO) the twotter moves forward, strong enough to pushback the pushback during pushback, right through the wall =/

is there a way to handle the twotter, without having to use F2-F3 to find the neutral position?

that method is a pain for landings etc

thank you!

PS: while parking breaks are on, i have a torque pressure of 7, prop rpm 40, gg rpm 68%, auto-feather activated according to manual, only warning light on is "reset props"

[Snave 466]

Pull Condition Levers to Low Idle. SOP on PT6's.

[HBE66 2]

aaah GREAT! that did the job

so i only need the mixture on full during startup?

after startup it remains on idle untill next startup?

thank you!

[Snave 466]

It's NOT a `mixture` lever. That's for piston props. They work quite differently.

Turbine engines idle at far higher levels of thrust than piston engines and the only way to `throttle` them is to use the Condition Lever, which controls the Fuel Control Unit (FCU) on PT-6's. In more advanced aircraft the CL will ALSO control the prop speed, but not in the Twotter, it's FADEC is the `Finking And Digits of the Eedjit in Command...`

The Condition Lever stifles the fuel flow to reduce the amount of idle thrust produced. It does NOT affect the mixture - the air/fuel ratio as does a piston prop mixture lever.

[HBE66 2]

aaaah theres the confusion =)

i was already thinking "wont the props just turn off if i do that?"

so the condition leaver can basically be understood to controll howmuch fuel is injected? (independant of the air, as it is already compressed)

- high condition leavers for takeoff etc (when much power is needed)

- idle condition leavers for taxy etc (when only little power is needed)

- cutoff (when going home ^^)

thank you

[Snave 466]

aaaah theres the confusion =)

i was already thinking "wont the props just turn off if i do that?"

so the condition leaver can basically be understood to controll howmuch fuel is injected? (independant of the air, as it is already compressed)

- high condition leavers for takeoff etc (when much power is needed)

- idle condition leavers for taxy etc (when only little power is needed)

- cutoff (when going home ^^)

thank you

You got it. The High Idle may also be needed for complex air conditioning and pressurisation systems (again, not an issue in the Twotter: For air con open the window, for pressurisation, fart).

[Avian 1]

Well I can take off in the Twotter with the prop levers fully back and the fuel levers almost at cutoff and not only take off but reach full speed, are you sure this is modelled properly? (this is the floatplane, but that shouldn't make any difference)

I mean I could be wrong, but it seems not right to me.

[Snave 466]

Well I can take off in the Twotter with the prop levers fully back and the fuel levers almost at cutoff and not only take off but reach full speed, are you sure this is modelled properly? (this is the floatplane, but that shouldn't make any difference)

I mean I could be wrong, but it seems not right to me.

Think about what you are asking. You are asking about TAKE OFF performance in a thread about low IDLE.

Could it be, do you think, that the idle affects only the bottom end of the power curve..? Does idle affect top end performance in a fuel-injected car? Motorcycle? Jet ski? House-sized marine 2-atroke diesel?

As long as the supply/demand cycle is within limits fuel will be delivered to a turbine until fuel is removed. If the metering system recognises a full power demand why would it even matter what the idle setting was?

Only if the metering affects not just low idle but right the way through the power curve would what you are asking be correct.

So why would the lever be flagged `low idle`..?

Would it not then be flagged, badged and known to all as the `low power` lever..?

Perhaps it's called `low idle` for a reason?

[Avian 1]

Well considering that the levers have  a full range of positions from cut off to full flow (one assumes) and also that it was suggested that they could also be used to control the power surge during startup, it is hardly unreasonable nor illogical to think that they would equally influence the amount of fuel flowing to the engines at a higher setting when the throttles are opened, but they are set almost fully back, naturally if the condition levers are tied to the throttles in such a way that the throttle overides the condition levers setting then what you say makes sense, but I did not know that, and there is nothing obvious to indicate it either, so your somewhat sarcastic answer, while appreciated for it's technical info, is less so for it's lack of social grace.

We can all learn something everyday, and not everyone who enjoys flight simming is an airplane expert.  

[Snave 466]

Well considering that the levers have  a full range of positions from cut off to full flow (one assumes) and also that it was suggested that they could also be used to control the power surge during startup, it is hardly unreasonable nor illogical to think that they would equally influence the amount of fuel flowing to the engines at a higher setting when the throttles are opened, but they are set almost fully back, naturally if the condition levers are tied to the throttles in such a way that the throttle overides the condition levers setting then what you say makes sense, but I did not know that, and there is nothing obvious to indicate it either, so your somewhat sarcastic answer, while appreciated for it's technical info, is less so for it's lack of social grace.

We can all learn something everyday, and not everyone who enjoys flight simming is an airplane expert.  

Well you don't appear to be taking the lessons on board. Doing the simplest of Google searches would provide you with the answers that you shouldn't really need to ask here. This is a FSX/FS2004 aircraft forum, not a `learn what you need to know about PT-6 engines` forum. Hence the tone of my reply. You could do your own research in a matter of seconds, and never need to interrupt a thread with some off-topic meandering that really didn't have any relevance to the original question. But you did, so I did. And here we are.

The condition lever does NOT adjust fuel flow from cut off to full flow. How many times does this need to be explained? It has just three positions, EXACTLY as indicated - cut off, low idle and high idle. Nothing more. And certainly nothing less. The lever does NOT function anything like a `mixture` lever in a piston prop - possibly where your confusion is coming from.

Cut off is - unsurprisingly - OFF

High Idle will give an N1 of about 70%

Low idle gives a minimum of 52%

..resulting in a small adjustment within a narrow Ng range which reduces residual thrust and fuel burn to ease the burden on brakes, or the amount of Beta needed in taxiing.

That's it.

It is perfectly possible (and in many PT6-equipped aircraft standard operating practice) to keep the condition lever in Low Idle at all stages of operation (except engine off and startup, to be pedantically accurate).

Also, in the interest of technical accuracy, there are different types of turboprop engine that require different handling to those in the Twotter, and indeed there are different approaches to the use of that lever in different aircraft equipped with different versions of the PT6. Again, beyond the scope of discussion here.