View Full Version : Starting/Cruising

14th Sep 2004, 14:13
Dear all,
what do you monitor on startup and in cruise - EPR or N1 or N3?
Do you understand EPR and do you find it difficult to control to?
what would you like to control to? Personally i think percentage thrust would be a good display. Thoughts?


15th Sep 2004, 10:43
EGT and Oil pressure should be the two main inds you monitor at start up. As for EPR vs. N1 you shouldn't have a problem to control to either if you have a serviceable engine!!

Capt Claret
15th Sep 2004, 15:22
Start up

Ignition on, starter operating,
N2, to know when to add fuel,
1001, 1002, 1003.... light off by 1010,
N1 increasing,
Oil Pressure rising,
N2 rising,
Rate of TGT rise to abort if overtemp,
out of periferal vision, Low Oil Press unnunciator, extinguish,
Starter Operating light out,
Ground Idle N2 within limits.


N1, no EPR gauges,
Oil press/temp,
N2, TGT, Fuel flow.

Old Smokey
18th Sep 2004, 01:45

The 2 previous posters here have come up with good common-sense parameters to monitor during start, even with engines with Auto-Start / Auto-Start Protection, good airmanship and cockpit management dictate that critical parameters be monitored.
Do you understand EPR and do you find it difficult to control to?
EPR in it's simplest form of explanation is Pressure Out Vs Pressure In, not much more complex than that. It's no more difficult to control to than setting an N1, EGT, Fuel Flow or any other engine parameter.
what would you like to control to?
I'm presently stuck with EPR, but would prefer N1. My primary dislike of EPR is the effect of icing on the credibility of EPR.
Personally i think percentage thrust would be a good display
Personally I think percentage thrust would be a useless display. Jet engines are primarily limited by Pressure (monitored by EPR), Engine Speed (monitored by N1/N2/N3), and Turbine Temperature (monitored by EGT/TGT/JPT etc.). Setting to an actual value of thrust monitors none of these limitations.

Takeoff, MCT, and Climb thrust will be set to the most limiting of these 3 limitations. Cruise thrust will be 'as required' to maintain the scheduled Mach No. or CAS, within the limits of MCR of course.

During Approach, we all have an initial 'ball park' EPR / N1 / Fuel Flow to set for typical approach configuration and speed, and adjust thrust from there as required to satisfy the Speed Trend Vector, or CAS variation in the absence of a Speed Trend Vector.