SAT limit?

[wiggy]

Heading eastbound over the Baltic Monday PM we heard several calls to ATC from crews on a shorthaul type, possibly 737-800's, demanding descent because of the OAT/SATs. Now I agree it certainly was tad parky :uhoh:, it was down to around minus 70 celsius at FL 350 overhead Helsinki/ Saint Pete's, but from the discussion it sounded like there was an AFM SAT/OAT limitation triggering the concern, not fuel temp - was that the likely issue?

(FWIW I'm a dyed in the wool Long hauler, had fun and games because of the Fuel temp more than once but never seen a AFM OAT/SAT low temp limit for cruise, hence the question)

[TopBunk]

Wiggy

The A320 family has an SAT limit of -70degC. Could have been that type you heard requesting lower.

[shaftsburn]

I used to work for a company in the Baltics.

On the B737 classics there was a minimum temperature of around -72C laid down in the FCOM limitations.

I've not seen this limitation anywhere in other company OMs.

[EMB170]

E135/145/Legacy have 65C

[Trackdiamond]

For clarity...is it a Fuel storage and delivery limitation or is it an engine ignition/combustion limit?

[wiggy]

Thanks Guys, that all makes sense and ties in with the comments we heard. Must admit that there was so much concern being expressed over the airwaves that it even had us diving into our manuals to check to see what we had missed in the most recent amendments :uhoh:.....

[Tiennetti]

Incident: Eva Air A332 near Simferopol on Dec 29th 2010, loss of cabin pressure (http://avherald.com/h?article=43561f7b)

The actual ambient temperature of -70 to -72 degrees Centigrade was lower than the certified minimum temperature of -64 degrees Centigrade permitting the temperatures around the probes to drop to zero degrees Centigrade or lower.

[Piltdown Man]

There is a minimum temperature limit for aircraft stated in their AOMs. And we have to stick to it. But this is really a financial limit. The world leaders in extracting cash for paper are Boeing and other manufacturers have copied their lead. I fly an Embraer and we used to have a limit of -60˚C. But part of the sales package we negotiated when we purchased additional aircraft was an increase in the operational envelope regarding temperature. The minimum temperature (SAT) we can now operate is -70˚C. The only modification required was a new page in the AOM. I believe the same is true, to some extent, for some other limits like ZFWs, MLWs etc. The manufacturer places an artificial limit on their their product and charges you for each step you take to make the limit more reasonable.

So remember, if ever you sell an aircraft manufacturer a table, tell them they can only use it on Mondays, Wednesday and Fridays, during daylight hours. Charge a premium for night time and additional days. And whenever it's resold, make sure the initial restrictions are re-instated and screw the new owner for the same relaxations. It's a policy they should understand - because they do it with their products.

[VNAV PATH]

These graphs are included in the Airplane Flight Manual, which is not the usual FCOM. It shows a flight enveloppe with OAT/SAT, and pressure altitude altitude. Some Airlines includes it in their FCOM or not ; it's called sometimes environnemental enveloppe chart.


AmericaWest experienced such limitations in Arizona few years ago on a big heat wave.

[A-3TWENTY]

A330 is -78ºC and I found -76 over Russia.

[Garnitur]

A340 as well -78°C and TAT -53°C

Had both on a flight over Russia but we didn't had to descent

[C_Star]

A320 has the lower SAT limit decreasing with altitude. Had to climb once or twice to stay within limit :)

[ImbracableCrunk]

It could have been a fuel temp limit if it was a 737.

[shaftsburn]

http://www.b737.org.uk/images/environmentalenvelope.gif