I guess I'm having a hard time with this. I can't find anything that written up about cecos.
It seems common knowledge in the world of the internet that cecos are modulated but that doesn't mean it is correct.
All I know is that the 2 ceco systems I've used definately had to be modulated. If the systems needed adjustments, then maybe the old guys were ok with that. As far as my experience goes, there's a big difference between the bendix and ceco and that's what I know.
It's already documented in the Rolls Royce 250-C20 Operation & Maintenance Manual. The CECO was designed to start without any modulation, if adjusted correctly. It was also designed to allow, unlike the Bendix FCU, a modulated start. Below are excerpts from the Rolls Royce manual.
Set it up correctly and it will start without modulation. Note those two adjustments on the CECO "Start Derichment" & "Light-off Adjust"
Click photo to enlarge
Well Dan, as far as the RFM is concerned, there shouldn't be any difference to the pilot. And I went back to the 206A RFM to see if Bell put a note in there about it.
I'd say...and I'm guessing here...that the outfit you worked for probably had the CECO's set up incorrectly for some reason...personal preference perhaps? In my experience, the CECO and Bendix were interchangeable as far as how the ship started. The fact that the CECO offers a small amount of adjustability on the TOT during the start doesn't mean you should have to avail yourself of it every time.
Then again...I've known pilots who SWEAR that they can "modulate" a Bendix in a B-model. And I'm here to tell you, after tens of thousands of starts of Bendix-equipped C-20B's over the years...*IF* there is any modulation of the TOT available to the pilot, it is TINY...and probably very FCU-specific...and probably illusory. They THINK they're affecting the TOT but they're probably not. I've tried and tried to squeak the throttle back in the various ships I've flown (206B's and Bo-105's), and all I ever get is cut-off.
Rolls Royce 250-C20 Operation & Maintenance Manual (72-00-00 pg. 62)
The 250–C20 Series engines each have two qualified control systems; they are:
The MC–40 (250–C20, –C20B, –C20J) control system manufactured by the Chandler Evans Control Systems Division of Coltec Industries.
The DP–N1 (250–C20) or DP–N2 (250–C20, –C20B, –C20F, –C20J), (control)/AL–AA1 (governor) control system manufactured by the Bendix Engine Controls Division of Allied Signal.
C. Starting Modes.
Starting procedures are given for an automatic start mode (CECO or Bendix system) and for a modulated start mode (CECO system only).
Automatic Start Mode:
The throttle is advanced directly to the IDLE detent when desired N1 cranking speed is reached.
Modulated Start Mode:
The throttle is advanced toward the IDLE detent in increments as required to increase TOT and N1 speed at a steady rate that remains within specified limits.
Rolls Royce 250-C20 Operation & Maintenance Manual (73-20-04 pg. 207)
F. Lightoff Adjustment
Make the lightoff adjustment by trimming the screw with a 5/64 in. Allen wrench to obtain engine starting fuel and exhaust gas temperature requirements. Turn the screw clockwise to decrease lightoff fuel flow.
G. Start Derichment Adjustment
The start derichment adjustment can be used to modify the starting fuel flow to improve cold weather starts, stagnated starts, or high altitude starts. Make the adjustment using a 1/4–in. Allen wrench having a 1/2 in. (13 mm) offset (or CECO wrench STD 67181). Turn clockwise (when viewed from end of adjustment screw) to enrich fuel flow for faster and hotter starts. Turn counter–clockwise for leaner fuel flow when starts are too hot. The normal setting is with the travel limiting screw at bottom center. Check the starting peak TOT after each setting until satisfactory starts are made.
Edited by iChris, 01 July 2014 - 04:06.