Starting PT6 in cold weather

[ILblog]

Hi

Yesterday I was starting PC12 in small mountain airport. With -15 C temperature and both batteries just on 24V I knew that it could end with hang start. There was -23 C in the night so I knew that chemical process in batteries will be very very bad.

Batteries were able to rotate compressor to 15% Ng when I put fuel on. Well the burning process started succesfully but I Ngs were just around 35%, a little bit bellow minimum required 40% (above 40%, the starters are disengadged, and we consider starting process finshed).

Well since I fly turbine in EC120B also, I did something, what I was lerned to do on helicopter, and it helped. Since the ITT looked very, very good, I just added a little bit of fuel by moving power lever a little bit. It helped to rotate compressor above 40%.

I not sure, if this is allowed on PT6.

Is there anyone, who can give me some tips, on starting PT6 in cold weather?

My plane has the standard lead-acid batteries, and I care them very well. Do you think, that Ni-Cad batteries could work better?

My batteries are 9 months old. Do you think It can help if I fully recharge batteries, just before my flight to mountains?

[LindbergB767]

Nicad work better
But what you should do when you know it will be very cold, bring your battery inside the night before
And also if you have electricity close to your plane put an electric car warmer in the turbine intake the night . Just remove it in the morning
It will be easier to start

[S.F.L.Y]

Hello, as far as I remember what you did is the recommended procedure on the TBM.
You can also consider using a portable GPU to assist the starting process.

[inbalance]

Pilatus recomends to put the condition lever in flight idle during cold starts. Did you do that ?

Inbalance

[ILblog]

Nope, I didnt use flight idle.

Adding a little bit of power to help acceletate Ngs seems to me like good practice. In fact flight idle just puts more fuel.

[S.F.L.Y]

I agree with inbalance, additional fuel should be provided through the condition lever and not power lever. Using the flight idle allows the fuel to be distributed through two different sets of injectors.

[TUIFly]

We have PC-12's here in Russia.

When temperature is below 0,
on start up when NG rises to 14% we put handle to flight idle untill it rises to 50%,when back to the ground.This is a normal cold weather operation recommended by Pilatus.
(In fact it's same if you will move PCL,just more fuel that's it)

I had some flights near North Pole at various places in Siberia with temperatures about -45 with no problem.

Yes,it's take bit longer to start engine,but during my 1,5 year of PC-12 flying it has never failed to start.

Only battery voltage is downsizing fast, so you should be carefull with and in cold weather like -20 or lower it's better to start with ground power on.

[ILblog]

Thank you all very much for your help.

[manitoubrian]

The POH states that if the OAT is 5 deg C or below you should go directly to flight idle until the Ng is above 50. Then back to ground idle.

Flew to Leeds today and the No 2 battery dropped to 16v in the start. OAT -1

[rigpiggy]

Since the P3 bleed to the pneumatic bellows doesn't normally allow to much extra fuel until about 60%, however jazzing the power lever "may temporarily allow enough fuel to accelerate the N1. Don't know the 12, but maybe leave the bleed air "on" as this will release back pressure on the turbine, allowing better start.