Balanced field takeoff planning - informal reference

[Chris Smith 9]

Hi fellow pilots,

 

I'm a tad bit obsessed about knowing when to (and not to) use flex temps. Since we do not have a TOPCAT tool for this beautiful bird, yet, I've started putting together my very unscientific method for determining when to use a flex temp. I'l share it here and continue to tweak based on experience and feedback. This is really a reference for me, but if others find it useful feel free to use it with your planning! 

 

I'll update the image below with an actual spreadsheet, but here is a scan of my table so far. I welcome any suggestions to make this better. I realize it's super basic and doesn't take into account altitude or temperature but it's mostly to help me guess better as to what settings I should use  Please note the values are computed from my very own trial and error with different settings (took about 2 hours to do the tables below). The distance with takeoff roll is how much estimated runway is used before the mains lift off of the ground. I then mentally add 1,000 to 1,500 feet for a good sense of comfort.

 

How I use it -  an example:

 

Say I'm at KLGA flying to KMCI in a CRJ900 at  TOW of 80,500. Departure runway length is 7,000ft. Looking at the table, I'd be getting a bit nervous now seeing Flaps 20 would give me a takeoff roll of 7,000 ft at full thrust at a mild temperature of 59F. But if I use flaps 8 and full thrust, I would use about 6,375FT. Say the temperature is 80 degrees, then this would probably be closer to 7,000 FT. In this case, I would probably boot some passengers or chance it with the previous settings and maybe turn off the packs

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As you can see, it's totally unscientific but it helps me stop worrying about how much runway I'm going to use until I have a better mechanism. The CRJ700 seems to be a beast and using a Flex temp of 55 seems to work for most scenarios. The CRJ900 on the other hand is a bit more of a runway hog.

 

 

 

 

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[Chris Smith 9]

Yes, 55C is what my flex temp was. I used 59F for the weather when I was doing my testing.

 

49C is the maximum setting? Also, those performance charts for each runway - is that something you can share?