B737 PMC (CL) vs EEC (NG)
Thread Starter
Join Date: May 2006
Location: 3 NM on final!
Posts: 225
Likes: 0
Received 0 Likes
on
0 Posts
B737 PMC (CL) vs EEC (NG)
Does anybody know the difference between engine PMC's installed in Classic series and EEC's installed in NG's? A technician told me they are completely different. Any book where I can find a detailed description of both systems?
Thanks in advance!
Thanks in advance!
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
The classic uses a basic hydromechanical fuel control for N2 governing, accel/decel fuel scheduling, and VBV and VSV servo control. The engine will run fine on pure hydromechanical systems; the electronic PMC fine-tunes this to achieve N1 control.
The 737NG has fully electronic control - all the above functions are handled by FADEC.
The 737NG has fully electronic control - all the above functions are handled by FADEC.
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
NG's have a HMU instead of a MEC
(Well, that may not be quite true. I think there's an overspeed governor in the HMU - in case all else fails )
Join Date: Apr 2004
Location: near EDDF
Posts: 775
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by barit1
I think there's an overspeed governor in the HMU - in case all else fails
Overspeed Governor
A mechanical overspeed governor can prevent an N2 overspeed condition.
When the overspeed governor senses an N2 overspeed condition, it causes
the bypass valve to open more. When the bypass valve opens more, less fuel
goes to the FMV. This causes the N2 speed to decrease. This is an alternative
N2 overspeed protection from the EEC. The EEC monitors the condition of the
overspeed governor.