solved Takeoff: Bleeds on or off? What about Anti-Ice?

[cosmic_3000]

Hello all,

Like the title says, what the is normal procedure for bleeds/packs when taking off? What about wing and cowl de-ice?

Thanks!

Edited March 1, 2018 by Morten

[Litjan]

These days, many airlines opt to take off with packs off - this puts less strain on the engines and you can reduce take-off thrust even more.

One method is to simply turn off the packs - this will cause the cabin to be not pressurized, which is not a big deal...unless you forget to turn on the packs again. Another disadvantage is that it gets warm in the cabin pretty quick, so I would not do that in the summer or if you expect to wait for take-off clearance more than a few seconds.

A second method is to keep the APU running and supply the packs.

The engine-anti-ice needs to be on during taxi already if you encounter icing conditions (<10C, moisture) - and you should turn it on for take-off if you expect to enter low clouds with the TAT <10C.

Wing anti-ice is only used if you can visibily see icing on the airframe - so you would not turn in on in anticipation of icing. You need to include it in your take-off calculation if you could possibly need it while climbing out to a safe altitude, though. It does not work on the ground anyway - you could turn it on already, then the valve would open up on lift-off.

Jan

 

[mga010]

I always take off with APU on in the sim. I do not have to pay the fuel. :-)

[cosmic_3000]

Awesome thanks for the info! I do have several question about the day-to-day operations with this aircraft, would the general discussion forum be a good place to post?

[mfor]

Well there's a Flight Operations sub forum....

 

.... and we've been moved there

Edited September 6, 2017 by mfor

[Rodeo]

On 9/6/2017 at 8:19 AM, Litjan said:

One method is to simply turn off the packs - this will cause the cabin to be not pressurized, which is not a big deal...unless you forget to turn on the packs again. Another disadvantage is that it gets warm in the cabin pretty quick, so I would not do that in the summer or if you expect to wait for take-off clearance more than a few seconds.

I can't remember where I read this, but apparently sometimes the "packs off" takeoff would be accomplished by turning off the engine bleeds (but leaving the packs themselves on auto), is this a real thing?

[Litjan]

5 hours ago, Rodeo said:

I can't remember where I read this, but apparently sometimes the "packs off" takeoff would be accomplished by turning off the engine bleeds (but leaving the packs themselves on auto), is this a real thing?

This may be done when the APU is supplying the packs - it is not allowed to have both APU bleed AND engine bleed on at the same time (you get the DUAL BLEED) warning EXCEPT with the engines at idle. This is to avoid the stronger engine bleed to push air into the APU (reverse flow).

Turning off bleeds would accomplish the same thing as turning off packs - but you would rob yourself of the pneumatic system and couldn´t use wing anti-ice or use the engine starter (in case you wanted to restart a flamed out engine).

Cheers, Jan