One way to find out if you've reached the stratosphere | Jet Quick Tips

Disclaimer: This is a rule of thumb that can only tell you some of the time if you've crossed the stratosphere when the ISA deviation is near zero and the temperature remains constant while climbing.
*All inflight footage was taken under part 91*

[@hazikaiyan5903]

Straight to the point. I wasn't expecting a 13 second video! 😂

[@PeterStaniforth]

The first 5 seconds of that were stunning, I could sit up there all day.

[@brandoncenteno1834]

you will know you're at the stratosphere when you climb through the tropopause - the point at which you encounter an isothermal layer, before temperature increases with height throughout the stratosphere.. signed, a former meteorologist turned soon to be airline pilot :P

[@CJPanichi343]

Best wishes on your journey!

[@KiwisCassie]

Very neat video! Subbed

[@Alpha.Foxtrot.Niner.Zero.]

Please correct me if I am wrong, but let’s assume, that we are at 10.000 ft AMSL, and our OAT is -5 °C. It will still show ISA 0 °C, and we will be nowhere near the Stratosphere. Best regards

[@CJPanichi343]

This concept only applies really applies (and only as a rule of thumb) when you're in the upper flight levels.

[@waffleboi7935]

good to know

[@thecia8331]

Nice video, what plane is this on?

[@CJPanichi343]

Learjet 60

[@thecia8331]

thanks!@@CJPanichi343

[@humongousballs]

⁠@@CJPanichi343Does it feel tight to sit in a Learjet or is it alright once you’re sitting down? I was once in a Learjet 45 and the back was already tight enough but the cockpit looked tiny. Especially with that center pedestal you have to climb over!

[@CJPanichi343]

@@humongousballs The 60 is generally pretty roomy and comfy (unless you're taller than 6'), although you still have to do that awkward center pedestal shimmy.

[@beck4283]

How does hitting the stratosphere change operations typically?

[@CJPanichi343]

The largest positive effect of flying in the stratosphere is that there is rarely ever turbulence or weather to deal with. You are generally above the tops of most thunderstorms.

[@beck4283]

Ah, tysm!

[@kurtreber9813]

Isn't this where the coffin happens?

[@bobbyderen5661]

Flew Jets for 30 years. First I've heard of this.

[@teelve]

@@kurtreber9813 Stratosphere and Coffin Corner are unrelated. The Coffin Corner is defined by the altitude where your low stalling speed (due to insufficient airflow on the wings) and high stalling speed (due to supersonic flow on the wings) are very close together.

[@thestormchasingconcorde6184]

can you use SAT aswell?

[@CJPanichi343]

SAT is the basis for ISA calculations, so yes you could in theory. However, you'd need to have a chart handy to interpret the SAT temperature with respect to your altitude in order to definitively find out the base of the stratosphere.

[@alanb.4660]

From 36,000 feet to 51,000 feet msl, the standard temp is -56 °C....not sure what your are trying to say@@CJPanichi343

[@calvinnickel9995]

No. You simply look at the SAT and see that it’s steady with altitude change. If it is, you’re literally in the stratosphere.

[@crystalthewolf8945]

interesting that older learjets use the same PFD and ND as the CRJs

[@CJPanichi343]

I used to fly the CRJ before this so it was quite an easy transition for me.

[@Mattblackaviation787]

So the deviation will always be near 0 at the beginning of the stratosphere?

[@CJPanichi343]

yes

[@Jayson-c4h]

Yes due to the Ozone layer it’s actually gets hotter as you climb until a certain point (very high up there). You can also tell when there’s thunderstorm clouds and at the top it gets flattened like an ANVIL

[@Mid-Michigan-Outdoors]

@@Jayson-c4h It's when the updraft hits the stratosphere right? (For your thunderstorm bit)

[@cloudstreets1396]

So on a standard day the stratosphere begins at the surface?

[@yudodisbro]

​​@@cloudstreets1396no the deviation temp here from the ISA standard atmosphere model is what we are looking at. Not the absolute temp. By definition the stratosphere has a constant temp of - 57°C thus the deviation from that temp will always be near 0.

[@justin8894]

Air!

[@michisvet2922]

Yes, but ISA +1 refers to the actual temp (56.5 degrees above FL360) plus one so 55.5. Am I missing something here or is it just one degree deviation from ISA? Because then this doesn't give any indication on whether we are in the stratosphere. Rather if the temp remained constant through the climb above the tropopause and TAS remained same. Correct me if I am wrong please.

[@CJPanichi343]

@@michisvet2922 you’re not wrong-on a standard day. This method only applies on a non standard day where widespread ISA deviation exists (which is more than 50% of the time)

[@calvinnickel9995]

I’m sorry but this isn’t correct. The stratosphere isn’t always - 56.5°C and it doesn’t always start at 36,000 feet. Meaning you can have an ISA dev +/- Take a flight through the ITCZ and you’ll see. The only way to tell is looking at your SAT gauge and seeing that it doesn’t increase or decrease with altitude.

[@CJPanichi343]

Read the description.

[@TheMonsterOfTheDeep]

Keyword: "On a non-standard day"

[@mikeseabrooks7978]

what aircraft is this?

[@CJPanichi343]

Learjet 60

[@bruno84]

This is nonsense! You can climb all the way from the ground till the tropopause with an isa -0. The only way you can suspect you have reached the tropopause is when you continue climbing and the temperature stops decreasing.

[@CJPanichi343]

As a general rule of thumb, if you've been climbing through an ISA deviation and it drops to about 0 dev., you can suspect that you've hit the stratospheric tropopausal boundary. It's only a rule of them and of course there are edge cases that don't exactly conform to this.