saab systems question

triple7

triple7

Well-Known Member
I deadheaded on a colgan saab the other day from IAH to CLL. My first time in a turboprop. Question regarding the environ's in that thing. 1) why does the #2 sit idle during boarding? air perhaps? 2)does that thing ever cool off inside? and 3) during taxi it looked like #2 was in a high idle and #1 was still in a lower idle....is there a warmup period or something?

That plane looked fun as hell to fly. Almost makes me want to leave the jet....but I like the ice crystals that fly out of Pack1 too much...lol.
 
Not quite sure I understand exactly what you're asking but I'll try to answer.

1) If you mean why #2 is running instead of all engines off it is because the Swedes did not bless the saab with an APU. So, in order to get that only slightly cooler than the cabin temperature air flowing through the gasper valves inside the plane we need an engine running.
2) If it's really warm out and the plane has been sitting and not connected to an air cart then no, not until right before landing.
3) In our attempt to cool off the plane we can turn on a high pressure bleed valve to add more air to the A/C system, in order to do that we have to keep that engine feathered at idle. If we don't the ITT on the engine with the HP valve running will shoot through the roof and we will have to seek alternate employment.

Hope it helped. :)
 
Rocketman99 said:
Not quite sure I understand exactly what you're asking but I'll try to answer.

1) If you mean why #2 is running instead of all engines off it is because the Swedes did not bless the saab with an APU. So, in order to get that only slightly cooler than the cabin temperature air flowing through the gasper valves inside the plane we need an engine running.
2) If it's really warm out and the plane has been sitting and not connected to an air cart then no, not until right before landing.
3) In our attempt to cool off the plane we can turn on a high pressure bleed valve to add more air to the A/C system, in order to do that we have to keep that engine feathered at idle. If we don't the ITT on the engine with the HP valve running will shoot through the roof and we will have to seek alternate employment.

Hope it helped. :)
Click to expand...

Ding ding ding.........triple chime as the ITT pegs the scale.........and the overtemp lights come on (also known as the resume lights....'cause if you see 'em lit up, you need to update your resume)


Oh, FYI.....the Saab is a great plane to fly.......lots 'o fun!
 
Exactly what I was asking. Thanks guys/gals. I noticed on the taxi out that one engine was noticably higher rpm. I also noted that on several other saabs i saw taxxing around IAH. Figured it had to be for a reason. I was sweating my a$$ off the whole 25 min flight. Wondered if the saab ever would eventually cool down or if it was just something you learned to deal with. It was about 80 out.

I had half a mind to sit up front and watch the guys do their thing. Seems like a whole lot more going on up there systems wise than in the jet. I must have it pretty easy..lol. I am impressed.
 
They will cool down nicely, but that requires maintenance techs who are on top of things and clean out the crap from the air conditioning ducts. You should see some of the stuff that has been pulled from those ducts. I know at Chicago Express they were pretty on top of it, maybe the Colgan guys can answer better about their maintenance.

Another thing that worked for cooling: Turning up the heat. When we'd immediately turn on the HP bleed, I'd put the temperature knob about halfway between cool and warm. That is because if you put ALL the cold air through right away, it will freeze the humid condensation in the ducts, and freeze. That reduces airflow, and can clog the system. This is especially important in places like IAH, where there is 1000% humidity ten months out of the year.

We had an ERJ once that wasn't putting out much air at all, and we were cooking inside. I decided to isolate the two packs by closing the crossbleed, and turned the temperature up to about 75-80 degrees. After about five minutes, we could hear more air flow, and slowly turning down the temperature knobs finally put out some nice, cool air. Thanks to a great Captain for showing me that trick way back when!
 
FlyChicaga said:
They will cool down nicely, but that requires maintenance techs who are on top of things and clean out the crap from the air conditioning ducts. You should see some of the stuff that has been pulled from those ducts. I know at Chicago Express they were pretty on top of it, maybe the Colgan guys can answer better about their maintenance.

Another thing that worked for cooling: Turning up the heat. When we'd immediately turn on the HP bleed, I'd put the temperature knob about halfway between cool and warm. That is because if you put ALL the cold air through right away, it will freeze the humid condensation in the ducts, and freeze. That reduces airflow, and can clog the system. This is especially important in places like IAH, where there is 1000% humidity ten months out of the year.

We had an ERJ once that wasn't putting out much air at all, and we were cooking inside. I decided to isolate the two packs by closing the crossbleed, and turned the temperature up to about 75-80 degrees. After about five minutes, we could hear more air flow, and slowly turning down the temperature knobs finally put out some nice, cool air. Thanks to a great Captain for showing me that trick way back when!
Click to expand...

OMG I am so gonna try this tomorrow!
 
FlyChicaga said:
They will cool down nicely, but that requires maintenance techs who are on top of things and clean out the crap from the air conditioning ducts. You should see some of the stuff that has been pulled from those ducts. I know at Chicago Express they were pretty on top of it, maybe the Colgan guys can answer better about their maintenance.
Click to expand...

Wow, we have soooo many planes that just don't put out any air, whatsoever. The maintenance guys mess w/ the recirc fans and the a/c control panel but I don't think they ever clean the ducts. It's really frustrating when I same thing is written up and it get's MEL'd and nothing ever becomes of it.

That being said, I don't ever fear for the mechanical structure of the planes or for my life while flying them.......but the actual maintenance leaves a great deal to be desired. The most comprehensive preflights are ALWAYS done when a plane comes out of maintenance.....it's funny that the plane winds up w/ more MEL's after it just came out of the shop then when it went in. :insane:

FlyChicaga said:
Another thing that worked for cooling: Turning up the heat. When we'd immediately turn on the HP bleed, I'd put the temperature knob about halfway between cool and warm. That is because if you put ALL the cold air through right away, it will freeze the humid condensation in the ducts, and freeze. That reduces airflow, and can clog the system. This is especially important in places like IAH, where there is 1000% humidity ten months out of the year.
Click to expand...

That's a great suggestion and it makes perfect sense. I will definitely give that a try.
 
Does putting the thing in high idle have to do with having a higher gen load on it? That's what we do on the PT6's in the 99; if we have a high gen load in low idle the gen doesn't have enough power off the low N1 output to really run the gen properly, but it'll try to put the power out. The result is ITT's creeping up until the engine over temps, so the solution is to run the thing up to high idle.
 
jtrain609 said:
Does putting the thing in high idle have to do with having a higher gen load on it? That's what we do on the PT6's in the 99; if we have a high gen load in low idle the gen doesn't have enough power off the low N1 output to really run the gen properly, but it'll try to put the power out. The result is ITT's creeping up until the engine over temps, so the solution is to run the thing up to high idle.
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Yep, sounds similar w/ the GE CT9B's. Ground idle is around 75% Ng. However, when it's used for cooling on the ground the extra load placed on the engne causes the Ng to drop (duh) so we need to give it a little more juice to bring it back to 75% or so........othwise the ITT usually spikes. When used for cooling, the ITT is required to remain below 800 C*
 
sorrygottarunway said:
OMG I am so gonna try this tomorrow!
Click to expand...

It will only help if your ducts don't look like the "before" picture. :D

GetImage
 
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