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777-300ER Engine anti-ice

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777-300ER Engine anti-ice

Old 21st Apr 2023, 08:50
  #21 (permalink)  
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Originally Posted by 8che
What you are saying is that when in icing conditions as defined by Boeing, you will turn the engine ice protection off because the aircraft told you to ?
No,they are saying the opposite, safer option - leave the anti ice ON, even when clearly in clear air.
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Old 21st Apr 2023, 12:10
  #22 (permalink)  
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Originally Posted by 8che
This message is not relevant (on the ground) if the officially reported ATIS indicates icing conditions. TAT is not part of ground assessment. Ice detection is not enabled on the ground. This checklist is not relevant until airborne...
Can you please for once show where your information comes from?

The Boeing statement is to use OAT, Boeing does not anywhere say TAT cannot be used on the ground. OAT gives you more freedom, there is nowhere any requirement stated that OAT is ONLY metar reported temperature. If you decide to switch if to AUTO, fine. If you decide to keep it ON, fine, but be aware you are overruling a checklist in theory you are required to follow. I don't know any company that is going to hassle you for this decision. But don't come claiming this story about captaincy, common sense, blablabla... because you are not doing anything wrong by following the checklist. The Boeing statements on checklist creation are common for all fleets, however you abuse those statements. Boeing is not saying anywhere to "disregard" a checklist, Boeing does not say this checklist is not "relevant" in this situation.

"Common sense" is the most abused phrase in aviation by pilots, as is "we've been doing it like that for years". My request remains: show me where Boeing states B777 TAT is unreliable on the ground.

Last edited by BraceBrace; 21st Apr 2023 at 20:03.
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Old 21st Apr 2023, 13:54
  #23 (permalink)  
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Originally Posted by BraceBrace

My request remains: show me where Boeing states B777 TAT is unreliable on the ground.
Given that the FMC uses TAT to determine thrust set during TO, I sure hope TAT is not 'unreliable' on the ground...
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Old 21st Apr 2023, 16:38
  #24 (permalink)  
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Also, 777 ECL checklists can inhibited or modified when the aircraft senses it is on the ground. Boeing appear to have chosen not to do this with the ANTI-ICE ON checklist; maybe this is an omission/error on their part, or maybe itís deliberate?

As far as TAT and OAT goes, if youíre not moving very fast through the air, they are practically equivalent. Even at 100kts there is ~1C difference. If a system can measure TAT within acceptable tolerances (see above post) when at 0kts on the runway, then it can do it everywhere else on the ground and it is effectively OAT.
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