Too cold today?
 

Heard a Flyer c/s asking to descend to FL360 today as it was to cold at the level they were at. After a few mins they asked for further descent as it was still too cold. We were at FL360 a little way behind them and the SAT was ISA -9C.

Is the Embraer affected by extremely cold temps, or could there have been other factors involved?

Just curious.

I flew back from USA last week and SAT was -72, TAT was -43. I was keeping a very close eye on the fuel temp in the outer tanks as I had Jet A fuel (freezing point -40). A descent into warmer air or increase in speed will increase TAT, or you can transfer fuel before it reaches freezing point.

Fair enough, but didn't think the Cityflyer Embraers would have the endurance to be at altitude long enough for fuel temp to be a factor?

Over to someone with Embraer knowledge.....

TAT limit is -65 on the Embraer.

Any colder and you need to do something.

Only thing you can try usually, is descend.

Equals an OAT at about -93C, I guess that rarely causes trouble.

The A320 has a minimum SAT of -70 degrees - we've had to descend a couple of times once the indicator had shown an exceedence of this limitation.

WBF - Correct but by FL360 its about -67C so not too different...

(assuming Atom meant SAT...)

It is -65 SAT.

IIRC it is possible to increase, err, decrease...make the limit colder :} so it's not a hard airframe limit.

Erm... SAT!

Ta. ;)

That would explain it then.

Thanks for the replies.

Standard envelope is -65 but an AFM extension can be bought which extends the envelope to -70 with a restriction of minimum Mach .67 when operating in the extension.

Finnair definitely have the increased envelope. Not sure who else has it.

Embraer have been taking mugging lessons from the thieves at Boeing. When you buy an aircraft, it comes with a whole bunch of limitations which can be removed with cash. No modifications, just an update to your AOM. We now have a limit of -70˚C, but we bought another five to get this temperature reduction. So it sounds like the "Flyers" were not only paying attention to the SAT but also to their aircraft limitations. Good guys.

And just remember chaps. Whenever an aircraft manufacturers employee visits, charge him for the air he breathes, carpet wear, chair rental, the water he uses, the coffee he drinks and paper used in the toilet - plus seat rental, flush usage, door lock wear, hinge usage - just like they do to you.

But the classic highwaymen have got to be IBM. In the good old days, they never sold anything. They only ever leased. And that included the bugs in their OS - which you paid them to fix! The greatest degree of theft I ever heard about was when Willis Faber had to lease the colour "green" from IBM. They only ever leased blue computers but Mr Foster spec.ed green computers in their Ipswich HQ. Second to that was a disc pack upgrade in our company. An engineer would remove two jumper from a circuit board, bang in a code and voila - four times more capacity and an times eight speed improvement on an 18 month old disk pack. The performance was present already, but corporate greed decreed...

Long ago, I saw something similar.
A client had an IBM 370/115, had paid for an upgrade to the 125, and had proudly assembled his staff to watch the upgrade. The engineer arrived, removed some stuff, and pronounced the job done.

Not a happy client...

this is pretty much standard for any modern PC as well. semiconductor manufacturing isn't a precise process, and finished products need to be tested and sorted based on thermal/frequency/voltage properties and stability. They're then tiered/labelled with a "certified" minimum designation, but market demand and price segmentation may also require "derating", or even disabling certain features. It may not always make sense to design and manufacture physically different products (economies of scale...akin to airline ticket pricing, in most cases, airlines don't use 3 different aircraft for 3 different cabin classes, but put all customers into the same aircraft; marketing departments try to segment customers and maximize revenue, based on guesstimated willingness/ability to pay, and availability: they also try to sell the entire "batch" of seats, eg fill the aircraft, and may also offer "upgrades", based on availability, to "unlock" various extra features) ;)

I didn't want to start the tangent but seeing as we're already there....

I'm led to believe that Boeing charge in the order of $14000 per technical question. Not an alleviation from the manual but more something like "we don't understand what you've written here in your manual, could you explain x"

Core Lock?

Not strictly true. When Boeing produce an aircraft they design and produce what they believe the market wants, at an acceptable price. Included in this price will be an element for R & D, actual production costs, testing costs and finally, product liability insurance. As a guide, the product liability insurance premium alone for UTC in the early nineteen eighties was US$250,000,000 for one year.
Boeing could go ahead and produce an aircraft with every 'upgrade', (not 'Limitation'), included but this would take the basic price above what many customers are prepared to pay and include many items they don't want as well as above what the competition charge for a similar basic article.

If a customer now decides they want upgrades then they have to pay for them, including their production costs and the protection of product liability. See the post of deptrai above which explains why some upgrades are fitted but need to be activated.

The temps have been too cold. What is normaly -56.6C t the tropo is now -70 C

Jet fuel dpending on make can gel or freeze at -45 if it is too cold for the heat exchanger, then you must descend. Some aircraft have Core Lock issues, more than others too - as you all know.