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Engine Runup In Icing Conditions...

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Engine Runup In Icing Conditions...

Old 24th Jan 2010, 16:40
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LEM
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Exclamation Engine Runup In Icing Conditions...

Question: Do you make a 30 seconds runup on the runway before takeoff every time there are icing conditions?


Let's elaborate a bit before we jump to conclusions:

A few years ago, when I was on the 737 classic, the manual required to make a 30" runup at 70% N1 during taxi, at intervals of 10 to 30 minutes, when operating in moderate to heavy icing conditions (visible moisture at or below 10C...).
Before takeoff this runup had to be repeated, without the 30" constraint, to observe stable engine operations before releasing the brakes.

I don't know if in the last few years they have changed this wording significantly.

Now that I'm on the A320, the Airbus manual says: "If icing conditions last longer than 30 minutes, [], the engine should be accelerated to approximately 70% N1 for 30 seconds before operating at higher thrust. []
This runup should also be performed just prior takeoff with particular attention to engine parameters to ensure normal engine operation."

Still on the 320, but having just moved to another company, where they like to personalize everything and to remake all manuals, the wording is slightly different, but the substance remains the same.

The problem is: some interpret the second part of the phrasing in a way that I think is improper.

According to them, every time you have icing conditions and you use engine anti icing for takeoff, even in rain with 9C for example, you have to runup the engine for 30 seconds before releasing the brakes, which I think is exaggerated.

I interpret this obligation as being tied to a long taxy of 30 minutes or more.

We all understand that it is a good practice to make a runup when condition deem it necessary, but my question is very precise, and I hope you will give it an honest answer: are you obliged to stop on the runway for 30 seconds every time it rains with, let's say, 9 degrees?

If everybody did that, the world would almost stop at busy airports every time it rains below 11C!

Thanks for your comments.

LEM
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Old 24th Jan 2010, 19:03
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are you obliged to stop on the runway for 30 seconds every time it rains with, let's say, 9 degrees?
We don't.
The problem is: some interpret the second part of the phrasing in a way that I think is improper.

According to them, every time you have icing conditions and you use engine anti icing for takeoff, even in rain with 9C for example, you have to runup the engine for 30 seconds before releasing the brakes, which I think is exaggerated.
Airbus FCOM 3.4.70 contains a diagram which gives indications about if and when apply the ground ice shedding procedure.
Any additional procedure is a company point of view, not a manufacturer requirement.
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Old 25th Jan 2010, 05:24
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The only mandatory I know is on the B757 with PW 2000 to run such a procedure due to FAA AD.
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Old 25th Jan 2010, 11:15
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Hi LEM,

The manual you are refering to states that you need to apply this procedure if icing conditions last for more than 30 minutes or significant engine vibration occurs, and obviously if ground surface conditions and environment permit it. Beside that, it is not forbidden to make such a run up if you feel more comfortable even after 5 minutes, but it is not required.

Ciao.
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Old 27th Jan 2010, 14:16
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You do whatever runup is required in your FCOM. Each engine type has its own requirements. My 777 manual covers about six engine variants for different models. There are two different procedures listed for before take off and two different procedures for taxi depending on the engine make and model.
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Old 27th Jan 2010, 16:19
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You do whatever runup is required in your FCOM. Each engine type has its own requirements. My 777 manual covers about six engine variants for different models. There are two different procedures listed for before take off and two different procedures for taxi depending on the engine make and model
Could you give some examples of these differences in procedures.

During low-power operations the engines have a tendancy to behave similary relative to ice acretion in the cold section. They also respond similarly to shedding ice, albeit the results may vary. Similarity in procedures between engine models is preferred for consistency in pilot decision making.
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