ALT and TEMP operating limits CHART -???

[anavguy]

Hi, everybody!
I have a problem here, i don't know how to read this chart.
ACFT has limitation for T/O - 10000feet elevation and temp ISA+35 C.
And this limitation is easilly readable from this chart. But what about upper part of envelope? Why do we need it? And what does it mean?:ugh:
Thanks in advance.

[Piltdown Man]

Dial in the Pressure Altitude and out pops the minimum and maximum temperature operating temperature, which will also be expressed as a deviation from ISA. At higher altitudes, the minimum temperature can be an issue. There can be many reasons for the limit that is set but it's usual for none of them to be stated.

[anavguy]

So. for example, i am at FL300. What this chart tells me?

[RTN11]

That the OAT should be between -63 and -15, and if it isn't then it's outside the operating limitations of the aircraft.

[anavguy]

it is clear for me how you get -63 C, but -15 C. How you get -15 C and what does it mean?

[RTN11]

Starting from the 30, as you chose the example of FL300, moving to the right, the first line you hit is the lowest temperature the aircraft can operate at at this level, going straight down I get around -63C, although it's on a tablet so not the best resolution.

Keeping going across from the 30, and you get the the end of the box on the right, again going straight down I'm coming up with -15C. This is the highest temperature at which the aircraft can operate at this level.

Not really sure what you're not getting about this?

[Mad (Flt) Scientist]

anavguy, maybe this will help...
http://imageshack.com/a/img839/8227/g83y.jpg

I coloured in the "inside" of the chart - it's supposed to show the envelope you are allowed to operate the CRJ in - so if you are not "inside" the envelope - in the orange area in the one I just made - you are outside of the "design envelope" for the aircraft. Which means maybe - not for certain, but maybe - some stuff won't work as designed.

The envelope is chosen to try to cover MOST eventualities - usually it won't restrict you. But if it happens to be very hot or very cold one day, you might not be legally permitted to operate the CRJ.

The easiest example is actually at sea level - you have to be at or above -40C, and not above 50C. Outside that range, no-go.

[Mad (Flt) Scientist]

I wrote "CRJ" because that chart and much of what is written around it looks VERY familiar. But on reflection, I have no idea what that text about pitch rates and stability is about; I've never seen anything like that in CRJ documents. The quoted 'g' limits are so far outside of airliner norms I don't know what to make of them, to be honest. I think you have got some kind of hybrid chart and I'm not sure what to make of it.