737NG CFM engine temperature drop
Thread Starter
Joined: Apr 2008
Posts: 30
Likes: 0
From: Middle East
737NG CFM engine temperature drop
Does anyone know how much the temperature drops in the inlet of a CFM or similar jet engine? I work in China and they insist that engine anti ice isn’t mandatory at 10 degrees C, I know it’s unbelievable but I’d like to give them some “evidence” thanks
Joined: Feb 2017
Posts: 1,013
Likes: 15
From: Isla Grande
Joined: Feb 2017
Posts: 1,013
Likes: 15
From: Isla Grande
Joined: Jun 2001
Posts: 591
Likes: 36
From: The middle
As Flying wild said. Just nod your head and agree, and take the money.
after all how many times have you got distracted, or had a sudden drop in temperature, and not switched it on until maybe +5 or + 6, and how many times have the engines stopped as a result? If you’re anything like me then the answers will be a few times and never, so it’s probably not worth stressing if they want you to turn it on at 9 degrees instead of ten.
after all how many times have you got distracted, or had a sudden drop in temperature, and not switched it on until maybe +5 or + 6, and how many times have the engines stopped as a result? If you’re anything like me then the answers will be a few times and never, so it’s probably not worth stressing if they want you to turn it on at 9 degrees instead of ten.
Joined: Mar 2002
Posts: 4,569
Likes: 1
From: Florida
are we talking in the air or on the ground?
on the ground the air is sucked, in the air it's rammed. The 10C limit is close enough to be safe. Play with it and you take your chances with engine icing while in visible precip (snow, ice, fog, rain).
I suppose that if you define all the condtitions somebody could make a calculation of temp along the surfaces in an inlet and the fan blades
on the ground the air is sucked, in the air it's rammed. The 10C limit is close enough to be safe. Play with it and you take your chances with engine icing while in visible precip (snow, ice, fog, rain).
I suppose that if you define all the condtitions somebody could make a calculation of temp along the surfaces in an inlet and the fan blades
Joined: Apr 2010
Posts: 1,319
Likes: 100
From: IRS NAV ONLY
FCOM is very clear. And if they insist... well, you know why you're getting paid all that money.
Thread Starter
Joined: Apr 2008
Posts: 30
Likes: 0
From: Middle East
Thank you all. After 3 years of flying here it’s more to convince the future generation of FO’s that it’s not a good idea, apart from that I keep my head down but alas my desire to fix things gets in the way...
Joined: Jan 2013
Posts: 263
Likes: 0
From: Seattle Area
My understanding is that the requirement to turn on cowl (inlet lip) anti-ice, which also raises the idle setting, at temperatures above 0C TAT has more to do with the indicated TAT range at which you can have supercooled water droplets due to atmospheric convective or precipitation action and the difference between OAT and TAT rather than any temperature drop the air experiences passing through the inlet. As said above, in high speed flight and in low speed low power flight the air temperature rises slightly as it slows down in the inlet.
Joined: Mar 2002
Posts: 4,569
Likes: 1
From: Florida
Again the original OP never defined the operating conditions regarding flight e.g. are we ramming air (in-flight) or sucking air (on taxi out or in.) and where is the ice assumed to be forming (on the inlet surfaces or on the engine surfaces). There are different levels of protection involved.
Joined: Jul 2013
Aviation Qualifications: Non-Aircrew
Posts: 5,672
Likes: 3,317
From: Everett, WA
Again the original OP never defined the operating conditions regarding flight e.g. are we ramming air (in-flight) or sucking air (on taxi out or in.) and where is the ice assumed to be forming (on the inlet surfaces or on the engine surfaces). There are different levels of protection involved.
In flight, (at least on Boeing), selecting engine anti-ice increases the idle speed to insure the bleed air used for anti-ice is warm enough, with enough pressure to do the anti-ice job.
Joined: Mar 2002
Posts: 4,569
Likes: 1
From: Florida
Just to add, after reviewing the early historical records of engine related icing, the safety gurus in the industry took note of the variances between manufacturers, AC and engines regarding ambient temperature "limits" in precips (we hadn't known about super-cooled at that early time). Indeed these early limits did vary by 5 degree C. The decision was made to harmonize at +10C to avoid confusing pilots transferring between products. This decision seems to have worked out well where it has been followed and is embraced uniformly
Thread Starter
Joined: Apr 2008
Posts: 30
Likes: 0
From: Middle East
Thanks for the info, I was mainly referring to takeoff as this is where they tell the FO’s it’s not necessary but as you correctly point out, this is where the temperature drop is at its greatest
