Critical Engine

Perhaps its because of the design of the aircraft is different? Maybe there would be different effects on low speed on different kind of wings (perhaps the new design reduces the drag when that side of the engine failed, causing the yaw would be less significant)

@Gary Law @Drunk Good point! As @Gary Law mentioned, some instructor would say, "NEVER turn into the dead engine due to control difficulty." Lets look into this. What is the worst situation for handling in Engine Failure?

1) Power setting: As we discuss before, as engine fail, there will be a yawing moment (regardless if that is critical or not) As the operating engine running at its max power ; and the yawing moment will be the most significant. (More power on the live engine; more performance but also need more force to counteract the yawing moment. )

2) Low speed: At low speed, less airflow over the airfoil and the flight control is not as effective, compare to high speed. So the flight control might not have enough authority to counteract the engine yawing force under Vmc. And thats the concept of VMC.

that's why the handling quality is not as good when flying close to Vmca; and you dont want to risk that. ( might not have enough altitude to recover) As we discuss, you shall have more understanding, and turning into dead engine is do-able, only if the handling quality assured. ( Above Vmca) -give yourself some margin (couple kt above the Vmca and turn gently)

For the second question, whats the different in 'Old' and 'New' aircraft?

the concern here is the yawing force; so as we discuss before, the Newer aircraft generally have a better design of Counter-rotating propeller(CRP). By having CRP, it eliminate the issues with critical engine. As the thrust line is closer, the moment arm will be shorter and yawing force will not be as significant comparing to those 'Old' conventional aircraft. -side note: ATR is conventional. therefore, ATR does have critical engine like other conventional design.

@Drunk As aforementioned, the ATR has critical engine; and good that the ATR has ATPCS to aid the pilot, by autofeather the failed propeller to minimize drag. -sidenote. When practicing V1 cut on the ATR, we need to put full rudder to compensate the yawing force.

@Dreamer From my understanding, #1 and #4 engines are critical. As you said, they both have the longer Arm and more yawing moment compare to #2 and #3.

But I would assume the yawing moment wont be as significant as the Twin jets, or easier to manage. As the inner engine is still producing thrust and they might have the luxury to reduce the thrust on the operating side to minimize yawing moment. (depends on performance)

I talked to some 747 pilots before; they said IFSD is not a problem for them; if performance and fuel is permitted; they dont need to divert. They can continue the flight to the destination.

(not like other Twin Jet: IFSD --> LAND ASAP)

@ATVpilot why turning bleed will help performance? And what does ifsd stand for?🙏🏻

Before I explain, u need to understand where the bleed come from. The bleed comes from the high pressure compressor (it is simiply stealing energy from the engine) So by shutting them off, reserve all power within the engine. IFSD In flight shut down

As I know there are a few types of Piper having counter-rotating propellers.

On the counter rotating prop aircraft, It dramatically enhanced the aircraft handling during engine out. However, since the aircraft needs 2 different set of engines and prop, usually cost more for Maintenance . (Compared to conventional, same part can serve either side of the engine)

@Drunk

thanks for your reply!

Good thots, but thats not exactly correct!

As you can see from the note I sent, ‘the descending blade of each prop produces more thrust than the ascending blade.‘ so on the conventional design(both prop rotate clockwise),the thrust line of the left engine is closer to the fuselage, compare to the right engine. Therefor, if left engine fails, it would have a bigger turning moment; (most adverse conditions) thus, left engine is the critical engine. that’s only explained about P-factor.

please have a look on that picture! Let me know about bout your thot~