RJSAviator76

In cruise flight, is there anything in your SOP's against selecting CON on the TRS to maintain higher airspeed and not get the LIM flag on your FMA?

We're having two different schools of thought:

1) Selecting CON merely allows the engine to use more power only if it needs to, and it doesn't lead into exceedance if it does use the power beyond what's allocated under normal CRZ setting.

or

2) If it was intended to be that way, CON would equal CRZ setting, therefore leaving it in AUTO/CRZ is the only way to do it.


Thoughts?

goaround2000

If CON setting is anything like the 145 (which I'd imagine it would be), then the answer would be no! No you should not use CON unless you're in an emergency situation. CON thrust setting makes the engines work at a much higher temperature than intended, thus causing much more wear and tear.

There have been cases at certain companies (I won't mention which ones), where guys rode CON on climb out all the way, in one case for up to 30 minutes and nearly fried the number 2 as per mx records.

So, in short CON should be for emergency situations only, i.e. single engine.

__________________
"There's nothing more difficult than to initiate a new order of things" -Machiavelli

iPilot

Max continuous mere means the engine can run and run and run and not burn out. Doesn't say anything about doing it efficiently or allowing it to meet TBO times. I imagine you won't risk poping one ever while flying but you certainly won't make the maintenance guys (or the accounting department) very happy.

ToiletDuck

I fly the 145 but watch your temps when you select CON. If your temps jump then you're working against yourself unless you need it. Temp=wear on an engine=more cost to your company. Higher output=more fuel burn= more cost to your codeshare. I don't know how much quicker the engine would wear but I'm sure it's significant.

Schwartz

What's wrong with LIM on the FMA? Above about 30k the thrust ratings are almost all the same N1 anyway. It should stay in CLB-1 or 2 until it speeds up to the selected cruise speed, right?

Just like the 145, CON & GA are the same thrust rating. At my last company (the 145), we were prohibited from selecting CON unless directed by the QRH. At Compass, nothing prohibits us from selecting CON on the TRS page, but there is no normal situation that calls for it.

__________________
I see your Schwartz is as big as mine.

ExperimentalAB

If you're selecting CON for normal Ops, you need a good chat with a CP and MX guy. Are we really that dumb??

__________________
Fly 'er like you're with a woman.

RJSAviator76

I agree, but one difference for those unfamiliar with 170 is that unlike the 145, 170 has autothrottles, so selecting CON merely allows autothrottles to cross the CRZ threshold but not exceed max continuous threshold.

Yeah, you stay in CLB-1 or 2 until you reach your cruise speed, but if your speed drops off later in cruise and you get the LIM on your FMA, my question is if there's anything that states that it is not recommended.

TillerEnvy

The only time I've used CON power is in the sim when it's called for on a single engine climb out. We use climb 1 on a pretty regular basis and only get LIM if we're climbing in V/S or FPA modes. You won't get LIM in FLCH mode. The 170 climbs a lot better than the 175 when we're heavy, so you will normally see LIM in the 175 when you're trying to maintain 290 in the climb and at least 1500'/minute above 27K or so.

UpThere

You know whats really sad about this thread..... E170/190 in the REGIONAL forum. No regional shold be flying 170s or 190s, and I can say that because I fly for a one!!!

iPilot

The best thing any pilot can do in any "normal" situation is to just stick to the book. If something (anything) happens and they see you had the engines configured improperly you'll have quite the carpet dance in front of you. Worst case the plane won't cruise as fast, oh well.