Critical Engine on the 747?
 

Is there a critical engine on the 747 and if so...which one...and why? Thank you

Handling the Big Jets will give you the answer. :)

I really don't want to have to purchase a whole book to find out one answer. I have been using a lot of my old college books but none of them seem to have any 747 stuff in them.

are you studying for interview? If so, being too cheap to buy a great book is a good reflection of your enthusiasm;)

No.
Though Vmcg & Vmca are quite different with one or two engines out on the same side.

..unless of course you happened to be taxiing a Saudi 743 in Aug01 with just #2 & #3 alight...and knew nothing about the hydraulic system...in which case I would say that #1 would be critical.....but that's just being pedantic.

Clowndown, the correct answer that they are looking for is that which is the into wind engine on the takeoff role. Simply explained as a xwind from the left will apply a yawing moment to the left with all engines running.....lose # 1 and the yawing moment is compounded. Conversely lose # 4 and the yawing moment is not as great.

Good luck

Upwind, outboard on four engine aircraft.

Nope, its the downwind outboard.

To be absolutely correct:

It depends on whether the aircraft has positive or negative weathercock stability......

On the 4-engined jet I fly, which has POSITIVE Weathercock, the AFM states that the Critical Engine is the OUTER Engine on the UPWIND side.:confused:

@four reds

Yes, that's how understand the forces.

regards

One would hope that in the two years that have lapsed since this thread began that Clowndown may have discovered the answer....

It's obviously still topical for some people, including you!!!!!

FOUR REDS,

Purely tongue in cheek old chap. Never noticed this thread before.

Pc

Paracab, understood. Thanks:ok:

This topic (and quite a few similar) regularly arises on PPRuNe. Suggest that a search on "critical engine", "Vmcg", and "Vmc" (or "Vmca") will give you more than a coffee's worth of reading.

Certification things of interest are

(a) directional control characteristics
(b) loss of systems

while the typical interview question tends to relate to the crosswind consideration (which, basically, is ignored at certification). The thing to keep in mind here is that Vmcg is determined for nil wind (7 kt under the UK requirements) ... if you happen to be in a critical takeoff situation, with a decent crosswind ... then don't have an engine failure.

Traffic: ...Brakes are available without motors No. 1 & 4 turning; it would require only rudimentary systems knowledge. :eek:

Also had the Saudi crew crossfed the power to the proper HYD Systems they wouldn't have had the problem either.

What Saudi crew? There wasnt ANY flightcrew in the cockpit.

Mutt.

Surely he meant 'crew' in the sense of 'the people crewing the aircraft'? After all, 'flightcrew' wasn't used.