EPR Ram Effect

[speedjet]

Q: Do EPR increase or decrease during take-off due ram effect?

I have 2 different sets of notes and they contradict each other.

[18-Wheeler]

It definitely decreases.

[Aussie]

Yeah decrease!!!

[The Messiah]

Handling the big jets should clear it up for you.

[woftam]

It's been a LONG time but here goes from memory.
EPR is a ratio of PT2 (engine inlet pressure) and PT7 (exhaust pressure).
As speed increases during T/O PT2 pressure increases due to ram effect whereas PT7 does not benefit from this ram effect. Result? Decrease in ratio=decrease in EPR as T/O roll progresses.
Hope this helps.

[GetOffMyBack]

Considering the above, does the EEC compensate for the drop in EPR?

If it does drop by how much?

[Givin It All I Got Capt'n]

FADAC fitted enignes with EEC, or PMC on the older engines, will compensate for the loss of N1 or EPR with an increase in a/c speed...