Airline Pilot Central Forums - Embraer Rear Engine turboprop

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Quote:

Originally Posted by hydrostream (Post 3280493)

PC-12 NGX sounds like it’s similar to the Q400. There’s a button to switch between RPM settings. That’s exactly what the “condition lever” on the Q does. There’s no fine adjustments, it just rests in detents and tells FADEC which setting you want: 1020 (NTOP/MTOP), 900 (MCL) or 850 (MCR), start/feather, or fuel off. They could have eliminated it entirely and just used buttons and it would have functioned the same, in fact there are buttons to do just that. One setting allows us to maintain 850rpm for landing even after the condition levers are moved back to 1020 (reduced NP setting). Power levers sit in a detent to command max power in the selected setting until you pull them out to adjust power.

I assumed the ATR was similar, is it not?

I don’t have any experience with either the Q400 or the ATR. What I found was the EASA certification for the PW127M which says it has a single channel engine control with hydro-mechanical backup. So I take this as pre-FADEC technology, it’s there to protect limits, but doesn’t provide the full control that newer controls do.

Quote:

Originally Posted by SonicFlyer (Post 3280048)

Hey, I'm open minded and willing to learn. Teach me.

Yaw moments have to do with lateral displacement from the center of the CG. Also, with greater displacement they use larger rudders to be able to control the yaw. Compare a 900 to a 175 and look at the difference in the rudder. It directly correlates with the placement of the engines as they’re pretty much the same engine.

Quote:

Originally Posted by kevin18 (Post 3281680)

Thank you, makes perfect sense. I was thinking on the wrong axis.

Quote:

Originally Posted by SonicFlyer (Post 3281712)

Thank you, makes perfect sense. I was thinking on the wrong axis.

... Which axis were you thinking?

Just saw something on LinkedIn from Embraer saying it’s planned to be a 70 and 90 seater.

Quote:

Originally Posted by kettlechips (Post 3281820)

... Which axis were you thinking?

My thought process went like: "If the engines are in the rear, then that means they are further away from the vertical axis, thus allowing for more yaw during a V1 cut... with a jet it doesn't matter so much but with a prop that's a lot more force to deal with"

Quote:

Originally Posted by SonicFlyer (Post 3281873)

A windmilling prop IS more force than an inop jet

But the rear displacement would only be effective arm for a force perpendicular to the longitudinal axis

Quote:

Originally Posted by SonicFlyer (Post 3281873)

The adverse leverage which a single operating engine applies is influenced more by the engine's horizontal distance from the CL than by it's for/aft distance from the CG.

Once yaw occurs you do get a little additional yaw force from the engine moving horizontally out from the CG as the tail swings. But you'd never notice that because the yaw also swings the v.stab out into the breeze at the same time.

Back in the late 80's they were flying the CBA123 pusher, a 19 seat proof of concept... The aircraft was quite fast and quiet... Cost killed it for a 19 place aircraft... Take the concept and advances of 30 years and they may have a winner... Time will tell, they just don't need to over engineer the thing to keep the cost in line with the market... My 10 yen...

Cheers

Quote:

Originally Posted by ZeroTT (Post 3281919)

A windmilling prop IS more force than an inop jet

But the rear displacement would only be effective arm for a force perpendicular to the longitudinal axis

Auto-feather eliminates the windmilling issue. I talked to a guy who flew the Piaggio Avanti. He said that engine failures were extremely easy to deal with.