EPR Command Cursor B747-400 RR
Thread Starter
Join Date: Feb 2004
Location: Australia
Posts: 1,307
Likes: 0
Received 0 Likes
on
0 Posts
EPR Command Cursor B747-400 RR
I'm trying to figure out what the EPR command cursor is doing in this photo:
Photos: Boeing 747-412 Aircraft Pictures | Airliners.net
Idle is a normally a function of N3 and compressor discharge pressure.
During idle, does the command cursor just sit "idly" on top of the actual (indicated) EPR/IEPR?
Thanks.
Rgds.
NSEU
Photos: Boeing 747-412 Aircraft Pictures | Airliners.net
Idle is a normally a function of N3 and compressor discharge pressure.
During idle, does the command cursor just sit "idly" on top of the actual (indicated) EPR/IEPR?
Thanks.
Rgds.
NSEU
Join Date: Dec 2000
Location: on the golf course (Covid permitting)
Posts: 2,131
Likes: 0
Received 0 Likes
on
0 Posts
nseu
It looks to me at first take as if in that photo they had had all 4 engines flame out!
The actual EPR is 0.75 which is waayyy below idle EPR of about 1.02 or so. The green line towards the top of the EPR scale is the 'reference EPR' which is also displayed in green numerically on top of the scales as 1.48.
The N1 and EGT values are however consistent with an idle descent, so I would suspect as an alternative that the EPR gauges have all failed for some reason.
Sorry that's the best I can do having been up all night looking at the bl00dy things without seeing the lower screen with the secondary engines instruments and any EICAS messages!
It looks to me at first take as if in that photo they had had all 4 engines flame out!
The actual EPR is 0.75 which is waayyy below idle EPR of about 1.02 or so. The green line towards the top of the EPR scale is the 'reference EPR' which is also displayed in green numerically on top of the scales as 1.48.
The N1 and EGT values are however consistent with an idle descent, so I would suspect as an alternative that the EPR gauges have all failed for some reason.
Sorry that's the best I can do having been up all night looking at the bl00dy things without seeing the lower screen with the secondary engines instruments and any EICAS messages!
Join Date: Feb 2007
Location: Down Under
Posts: 124
Likes: 0
Received 0 Likes
on
0 Posts
Firstly that won't be a Roller EPR figure as Pratts were fitted to the Ansett Aircraft.
Secondly, and its a guess, it will show max cruise as that is what is selected as shown above the EPR figure of 1.48. MAX CRZ.
The yellow line above that probably will be max continuous.
We will leave the correct answers to some piloty types as opposed to an engineer.
Secondly, and its a guess, it will show max cruise as that is what is selected as shown above the EPR figure of 1.48. MAX CRZ.
The yellow line above that probably will be max continuous.
We will leave the correct answers to some piloty types as opposed to an engineer.
Join Date: May 2007
Location: ITCZ
Age: 72
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
The 412 was an original SQ aircraft, fitted with PW4056.
The photo is a normal descent, just like the caption says. On the PW, it's purely an EPR aircraft. No N3, just a N1 and N2.
All is well!!!!
The photo is a normal descent, just like the caption says. On the PW, it's purely an EPR aircraft. No N3, just a N1 and N2.
All is well!!!!
Thread Starter
Join Date: Feb 2004
Location: Australia
Posts: 1,307
Likes: 0
Received 0 Likes
on
0 Posts
Sorry, I should have realised that it was PW from the Ansett reference, but surely engine idle is controlled in a similar manner (with N2 and burner pressure being the controlling factors)?
It seems like the command cursor is at the bottom of the scale (why would it be anywhere else?).
It seems like the command cursor is at the bottom of the scale (why would it be anywhere else?).
The EEC should still control through two seperate engine parameters (EPR and N3 on RR, no idea about PW) depending on normal and alternate modes.
Seeing as the aircraft is trying to get down it isn't surpriseing the EPR command cursor is resting ON the commanded EPR which would be idle for a high rate of descent. It does look strange though..
During idle, does the command cursor just sit "idly" on top of the actual (indicated) EPR/IEPR?
Thread Starter
Join Date: Feb 2004
Location: Australia
Posts: 1,307
Likes: 0
Received 0 Likes
on
0 Posts
it isn't surprising the EPR command cursor is resting ON the commanded EPR
By the way, what is a normal EPR on a Roller in this phase of flight? Does it also dip below 1.0?
looking at the manuals, I see the EPR on the RR and PW are measured differently The Roller uses cold and hot stream pressures to calculate exit pressure ("IEPR"), the PW only hot stream.
Rgds.
NSEU
Last edited by NSEU; 4th Aug 2009 at 07:10.
