Ps76
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The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 9:43 am

Hi

My recent passenger flight on the B777 was delayed a little because the Captain told us there was a problem with the anti-ice bleed air on the right engine on the flight over. He said roughly the hot air bleed was meant to turn on automatically but hadn't done so so he was asking to have it locked in the on position. Was just wondering if I heard this right/what it might mean - I think he was only talking of engine anti-ice but would locked mean it would be running the whole time for the right engine for the flight. Would that mean a little less power available in the right engine. Also if the anti-ice didn't turn on automatically would there be a means to use it manually.

Many thanks for the help,

P.
 
OPNLguy
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 9:55 am

On the 737 (and by extension, I assume the 777), when an engine A/I valve is inop, you have two choices: you can wire (secure) it open, or wire it closed. If you wire it closed, there's no performance hit (and it's a relatively minor one anyway), but you can't fly into any icing conditions, which at this time of year may be hard to avoid. If you wire it open, you can operate into icing conditions, and it sounds like that's what they were doing so they could operate your flight.

There's no "manual" way to do this in flight, so you wire it one way or the other while on the ground.
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Ps76
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 10:11 am

Hi,

The flight was flying the North Atlantic (in the East direction). Amazingly there were people who really disliked the delay (although with further flights etc. to make I understand). But flying over the North Atlantic with only one engine having anti-ice would not have made my idea of fun!

Many thanks,

P.

[Edited 2006-12-21 02:13:55]
 
fr8mech
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 10:27 am

It is common to de-activate the valve in the open, or partially open, position (depending on a/c type). Yes, less power is available, so there is a performance penalty, but the aircraft is unrestricted due to icing issues.

A common misperception about icing: temperature really has little affect. It's all about visible moisture. Just about anytime there is visible moisture, you have an icing restriction. This is rarely an issue at altitude, but climbing and decending through clouds and rain present the issue. You need to also look at your alternates when determining whether you have icing issues.
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OPNLguy
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 10:41 am

Quoting Fr8Mech (Reply 3):
A common misperception about icing: temperature really has little affect. It's all about visible moisture. Just about anytime there is visible moisture, you have an icing restriction.

When I used to give dispatcher exams, this was one point I tried to drive home to applicants. When it comes to deciding yea/nay on an icing-related MEL deferral, one first goes to the definition of "icing" as it exists in the MEL, i.e. "An atmospheric environment that may cause ice to form...yada yada yada." Doesn't have to be in an area forecast (or not); doesn't have to be actually pireped (or not), just that it may form, and that you have to look closely at things.

[Edited 2006-12-21 02:43:23]
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Ps76
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 11:12 am

Hi,

Was just wondering if the left engine would also have the force to anti-ice on for power symmetry. If not then would something like 2x90% N1 make a little yaw to the right. Flying manually, would the pilots have to account for this effect, and might the autothrottle also know what the engines were individually making and even it for flying automatically.

Many thanks, P.
 
zenarcade
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 7:45 pm

I don't think this has been covered yet but I'll ask anyways. When an engines anti-ice system is wired to be always on is their a redundancy system which automatically controls temperatures?

I'm not familiar with the intricate workings of engine anti-ice systems but I'm assuming that having them on for the whole duration of a long flight can't be good in terms maintenance and part life.


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zeke
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 8:36 pm

Quoting Ps76 (Reply 5):
Was just wondering if the left engine would also have the force to anti-ice on for power symmetry. If not then would something like 2x90% N1 make a little yaw to the right. Flying manually, would the pilots have to account for this effect, and might the autothrottle also know what the engines were individually making and even it for flying automatically.

The performance reduction would be minor, unnoticeable in terms of hand flying, it would need to be taken into account for takeoff/landing performance.

Wing anti-ice would be another thing, it had a much higher demand for bleed air.

Quoting Zenarcade (Reply 6):
When an engines anti-ice system is wired to be always on is their a redundancy system which automatically controls temperatures?

Not familiar with any automatic temperature control for engine-anti ice, it is normally just a high pressure bleed pickup into the inlet space so that the inlet is heated from within.

Quoting Zenarcade (Reply 6):

I'm not familiar with the intricate workings of engine anti-ice systems but I'm assuming that having them on for the whole duration of a long flight can't be good in terms maintenance and part life.

That is a question for the mechanics, I dont see it would be a problem.
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Ps76
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 21, 2006 11:27 pm

Many thanks for the information/replies,

P.

[Edited 2006-12-21 15:28:35]
 
charlienorth
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RE: The Engine Anti-Ice Locked To The On Position?

Fri Dec 22, 2006 5:51 am

Quoting Zeke (Reply 7):
Quoting Zenarcade (Reply 6):

I'm not familiar with the intricate workings of engine anti-ice systems but I'm assuming that having them on for the whole duration of a long flight can't be good in terms maintenance and part life.

That is a question for the mechanics, I dont see it would be a problem

It would not be a problem.I might add an MEL like this would be corrected as soon as it could be given the operational issues.
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meister808
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RE: The Engine Anti-Ice Locked To The On Position?

Fri Dec 22, 2006 2:06 pm

Quoting Zenarcade (Reply 6):
I'm not familiar with the intricate workings of engine anti-ice systems but I'm assuming that having them on for the whole duration of a long flight can't be good in terms maintenance and part life

The sheer volumes of air flowing past the heated components while the engine is running have enough cooling effect to keep the heated components from overheating.

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OPNLguy
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RE: The Engine Anti-Ice Locked To The On Position?

Fri Dec 22, 2006 2:14 pm

Quoting Meister808 (Reply 10):
The sheer volumes of air flowing past the heated components while the engine is running have enough cooling effect to keep the heated components from overheating.

True, but we're talking about anti-icing, i.e. keeping certain parts heated so ice doesn't form on them...  Wink
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troubleshooter
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RE: The Engine Anti-Ice Locked To The On Position?

Fri Dec 22, 2006 5:52 pm

Quoting Zenarcade (Reply 6):
When an engines anti-ice system is wired to be always on is their a redundancy system which automatically controls temperatures?

On the 737, for example, the pressure downstream of the intake anti-ice valve is monitored by a switch. Normally valve regulates the pressure around 50 PSI. The valve receives an electrical "CLOSE" signal from the px switch if the pressure rises to approx. 65 PSI (which means a valve regulation malfunction). The temperature is not regulated. Duct pressure is the limiting factor!

If, like in this case, the intake anti-ice valve is (mechanically) locked in the open position the above described safety circuit is no longer available.

[Edited 2006-12-22 09:54:34]
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777wt
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RE: The Engine Anti-Ice Locked To The On Position?

Fri Dec 22, 2006 10:07 pm

Quoting Ps76 (Reply 5):
Was just wondering if the left engine would also have the force to anti-ice on for power symmetry. If not then would something like 2x90% N1 make a little yaw to the right. Flying manually, would the pilots have to account for this effect, and might the autothrottle also know what the engines were individually making and even it for flying automatically.

The FADEC's in the engines takes care of this  Wink
 
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RE: The Engine Anti-Ice Locked To The On Position?

Fri Dec 22, 2006 10:12 pm

Quoting Ps76 (Reply 2):
The flight was flying the North Atlantic (in the East direction). Amazingly there were people who really disliked the delay (although with further flights etc. to make I understand). But flying over the North Atlantic with only one engine having anti-ice would not have made my idea of fun!

Let me tell you something as I do engine anti-ice locked open maintenance which is once in a while thing...

Would you rather have a delay for a out of service aircraft while the troubleshooting takes place then AOG sourcing and shipping out a new engine anti-ice valve plus the time to R&R it?

Or would you rather take a small delay and the flight will be dispatched safe?
 
troubleshooter
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RE: The Engine Anti-Ice Locked To The On Position?

Sat Dec 23, 2006 11:55 am

Quoting Ps76 (Reply 5):
Was just wondering if the left engine would also have the force to anti-ice on for power symmetry. If not then would something like 2x90% N1 make a little yaw to the right.

You will not have any thrust assymetry. 2 x 90% N1 is 2 x 90% N1!!! The only difference you might observe is a slightly higher EGT on the engine where the anti-ice is constantly "ON".
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meister808
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RE: The Engine Anti-Ice Locked To The On Position?

Sat Dec 23, 2006 2:17 pm

Quoting OPNLguy (Reply 11):
True, but we're talking about anti-icing, i.e. keeping certain parts heated so ice doesn't form on them...

Hmm... true, but, the way I look at it, the volume of air is something of a temp regulator for the heated parts.

Quoting Troubleshooter (Reply 15):
You will not have any thrust assymetry. 2 x 90% N1 is 2 x 90% N1!!! The only difference you might observe is a slightly higher EGT on the engine where the anti-ice is constantly "ON".

Not exactly... 90% N1 is going to be a certain RPM, so if both engines are turning at the same RPM (90% of N1, in this case) and one is losing a little bit of pressure to bleed air, then it will generate slightly less thrust. As for the EGT, I'd say that is probably negligible, but someone with more experience than I would have to back that up.

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CosmicCruiser
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RE: The Engine Anti-Ice Locked To The On Position?

Sat Dec 23, 2006 11:03 pm

As for the MD-11 it's not really that big a deal. The valve (there's 3 diff manufacturers for the anti-ice valves) is locked open, you enter "anti-ice valve failed open" in the perf. computer, after start you make the switch agree("on"), and you enter a 2% overburn in the FMS comp. There's a consideration to limit HIGH power settings on the ground so not to overheat the cowl. That's it. We just had this on one leg of my last trip.
 
BH
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RE: The Engine Anti-Ice Locked To The On Position?

Sun Dec 24, 2006 10:53 pm

With the anti-ice locked open you will also see an increase in fuel burn over the other engine with the valve in the closed position.

The extra fuel burn is an indiction to the flight crew that the valve is stuck open if they are having indication problems.
 
troubleshooter
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RE: The Engine Anti-Ice Locked To The On Position?

Tue Dec 26, 2006 3:02 am

Quoting Meister808 (Reply 16):
Not exactly... 90% N1 is going to be a certain RPM, so if both engines are turning at the same RPM (90% of N1, in this case) and one is losing a little bit of pressure to bleed air, then it will generate slightly less thrust. As for the EGT, I'd say that is probably negligible, but someone with more experience than I would have to back that up.

Sorry, I can not agree with this. If both engines are running at 90% N1 and one engine has anti-ice on, you will see a slightly higher EGT on that side. The reduction in thrust due to the bleed air extraction is compensated by a higher fuel burn (this gives the higher EGT). The result is both engines are running at 90% N1 with the same thrust.
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BH
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RE: The Engine Anti-Ice Locked To The On Position?

Tue Dec 26, 2006 5:03 am

Quoting Troubleshooter (Reply 19):
Sorry, I can not agree with this. If both engines are running at 90% N1 and one engine has anti-ice on, you will see a slightly higher EGT on that side. The reduction in thrust due to the bleed air extraction is compensated by a higher fuel burn (this gives the higher EGT). The result is both engines are running at 90% N1 with the same thrust.

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ThrottleHold
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RE: The Engine Anti-Ice Locked To The On Position?

Wed Dec 27, 2006 11:11 pm

I flew this week with the same problem. Received an ECAM warning in flight of aan engine anti-ice valve open, when the switch was off. On the ground, we had the valve wired open and the defect deferred. The only performance implications were a 4% increase in fuel burn and a slight restriction on Approach Climb Limit, but only at high temps of around ISA +9 if I remember right.
There was no appreciable difference in engine N1 or thrust, but there was a slighlty higher EGT.

Quoting OPNLguy (Reply 4):
When I used to give dispatcher exams, this was one point I tried to drive home to applicants. When it comes to deciding yea/nay on an icing-related MEL deferral

Deciding?? Thats the PIC's job.
 
AAR90
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RE: The Engine Anti-Ice Locked To The On Position?

Thu Dec 28, 2006 1:43 am

Quoting Ps76 (Thread starter):
but would locked mean it would be running the whole time for the right engine for the flight. Would that mean a little less power available in the right engine. Also if the anti-ice didn't turn on automatically would there be a means to use it manually.

There would be a slight reduction in MAXIMUM thrust capability for that engine compared to the engine without anti-ice valve open. Normally not a consideration unless you are at maximum weights. The valve on the engine is physically locked open by maintenance so there is no means to operate it manually or automatically... it is locked open.

Quoting Zenarcade (Reply 6):
When an engines anti-ice system is wired to be always on is their a redundancy system which automatically controls temperatures?

In all turbine engines I'm aware of, no temp control. On the ground at idle there is not enough bleed air flow to keep the surfaces warm -which is why engines need to be "run-up" periodically during ground delays in icing conditions. In flight the outside airflow is enough to cool the heated surfaces.

Quoting Zenarcade (Reply 6):
...but I'm assuming that having them on for the whole duration of a long flight can't be good in terms maintenance and part life.

Theoretically, yes. Not normally done so it is not something that is actually tracked by maintenance (that I know of). Airlines will want to get the problem fixed relatively quickly to regain the lost (however slight) performance and remove weight ($$ revenue $$) restrictions.

Quoting Troubleshooter (Reply 15):
You will not have any thrust assymetry.

At thrust settings less than maximum this is true. At maximum thrust setting there is a slight difference in N1/EPR (one engine having bleed air drawn off while the other does not) and therefore a slight thrust assymetry. Slight rudder to correct --no big deal.  Wink
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