CRJ 200 w/CF34-3B1 Question

[palgia]

This question refers to the CRJ-200 with CF-34-3B1.

Quick question: Is there are mechanical linkage (ie. cables) between the throttle and the engine fuel control unit?

I know in normal N1 speed control the throttle lever position is picked up by a variable resistior in the throttle quadrant, but I would like to know if when operating in N2 mode there is an actual mechanical linkage between throttle and engine fuel control (and if so, I'm assuming you'd have a governor with flyweights in the HMU).

Thanks for your help in advance.

palgia

[barit1]

I know the military TF34 has a Woodward "gold coffee can" control closely related to the early CF6 controls (flyweight N2 governor), and I think the CF34-3A/B's are probably similar.

[flyboyike]

Originally Posted by paglia

Quick question: Is there are mechanical linkage (ie. cables) between the throttle and the engine fuel control unit?

I know in normal N1 speed control the throttle lever position is picked up by a variable resistior in the throttle quadrant, but I would like to know if when operating in N2 mode there is an actual mechanical linkage between throttle and engine fuel control (and if so, I'm assuming you'd have a governor with flyweights in the HMU).

The short answer is yes, there is a mechanical linkage. I should add that N1 speed control doesn't kick in until 79% N1, provided the speed switches are on. These switches are deferrable, however, in which case we are back to all-mechanical controls. The thrust settings get much "jumpier" in that case.

I should also add that the -3A1 engine is the same way.

[ICT_SLB]

There's no difference in the control systems between the 3A& Bs - only the time vs temperature relationships in the EICAS ITT indications change. This is because of the differing engine internal parts. Operators can strap the EICAS to retain A ratings so the increased thrust & temps of the B are taken as increased time between overhaul.

As stated the N2 is controlled via a mechanical link to a Woodward Governor mechanical fuel control and then the N1 Amplifier takes over to control to fan speed. As you're aware, if you lose either engine (have an N1 decrease of 15% or more) after advancing the throttle to TO power, Automatic Performance Reserve (APR) kicks in (a ground from the N1 Amp to the APR Relay) to give you approximately 2% extra thrust on the remaining engine.

RJ-700 & -900s have FADECs and are powered by what is really a completely different engine.