767 GE 80-c2 anti-ice in descent

[blue up]

I've found conflicting refs in our own manuals and quite a few (possibly out-of-date) refs on the web about the need to have AI on during descent with sAT below -40c. It may have been covered on here before but I understand there has been a Boeing/GE rethink in recent days/weeks.
Any thoughts? We still have a Boeing Bulletin that mandates the use of AI below -40 but the ops manual says otherwise.
PS. How hot is AI air when it leaves the bleed valve (approx)?

[GASCAN]

Bleed air from the engine is regulated at about 450f and trips off at 490f.
Regards
Gascan

[esreverlluf]

"We still have a Boeing Bulletin that mandates the use of AI below -40 but the ops manual says otherwise."
Mostly correct, though as I recollect, the Boeing Bulletin (which of course supercedes the Ops Manual) only requires TAI to be on in icing conditions AND in the presence of convective activity WHEN thrust is at idle UNLESS the TAT is greater than 10 deg C (ie on descent in convective clouds and TAT less than 10 deg C).
Hope that helps.:ok:

[None]

This is Boeing Vol I 12 Dec 06

"Engine Anti–Ice Use

Engine anti–ice must be used during all ground and flight operations when icing conditions exist or are anticipated, except during climb and cruise when the temperature is below -40°C SAT."

This is a note from a different source confirming they want us to use eng A/I in the descent in an effort to prevent flameouts (by increasing bleed air extraction) that have occurred near convective activity. This note is specifically for the GE engines.

Note: Use of engine anti-ice in descent near convective activity applies even with SAT below -40°C.

[PantLoad]

Gentlemen:

This is the 'boiler plate' axiom for anti-ice use. It's Boeing's policy...but Airbus', as well. It's a certification issue (JAA/FAA) and the engine manufacturer's policy.

There have been cases of flameouts at high altitudes, especially (but not exclusively) during descents.... idle thrust, high altitude, cold temps (colder than -40c), in the area of thunderstorms (convective activity)...where the Einsteins in the cockpit chose not to follow SOP.

DUH!!!!

"None" quoted things correctly.....


Fly safe,

PantLoad

[blue up]

Our Ops manual (and our annual refresher course) says that AI doesn't go on if the SAT temp is colder than -40c, even if in cloud of any type. Previously we'd use AI in the descent with temp below +10c at any time in cloud.

We operate GE-767s and RR-757s.

Looks like another reprint is in order.:rolleyes:

[PantLoad]

Reference Airbus 15th Performance and Operations Conference in Puerto Vallarta, 23-27 APR 2007:

"Operation in Icing Conditions in Flight...Ice Crystals: An Environmental Threat" by Helene Rebel

Specifically, this discussion was centered on the GE CF6-80E1 and the RR T500. But, the impression I got when reading this is that the principles can apply to all airframes and engine manufacturers/models.

There is a reason why the Airbus and Boeing SOP is what it is.....

The Airbus FCTM is another good reference with regard to this topic.

PantLoad