Ace The Tech Pilot Interview- Clarification On Answer

[Tamilvimani]

Hi guys, I am revising my technical knowledge and one of the books I am reading is "ACE THE TECHNICAL PILOT INTERVIEW" by Mr GARY V. BRISTOW.

First of all, I hope Mr BRISTOW is a PPRUNE member. I would like to give my thanks for his superb effort in producing a concise tome of reference for the practising pilot in a question and answer format.

There is one subject in the book where I do not agree with the answer or need further light. I hope someone can help..

at page 60. Question: "How does a crosswind affect the critical engine?"

Answer: "A crosswind, depending on the direction, can either help to restore or aggravate the yawing moment of an aircraft with a failed critical engine. For instance a failed critical number 1 engine will cause a yaw to the left. A crosswind from the left will apply a restoring force to the aircraft's fuselage, whereas a crosswind from the right will aggravate the yawing moment further to the left due to the sideways force experienced on the right side of the aircraft' fuselage (which is from the right to the left).

At page 195 he substantially says the same when he says that with an engine failure between V1 and VR and if you had maximum crosswind it is better to lose the UPWIND engine. "This is so because the crosswind would then oppose the yawing moment of the downwind engine"

My question/doubt.:Is it not a fact that an aircraft tends to "weather cock" into the wind due to the keel surfaces which are substantially bigger in area and act as a 'sail'. Therefore a crosswind from the opposite side of the failed engine should counter the yawing moment of the failed engine. (ie its better to lose the downwind engine).

Thanks

[popay]

Tamilvimani, I agree with you. I know this book and there is a lot of good and usable stuff there, but this particular example, i think is wrong.
From own experience, during take off with cross wind from the left the A/C tends to turn into the wind, due to large fin surface located at the most distance from the pivot point, which aggravates the yawing moment into wind side. Having under this conditions engine number one failed strengths the yawing to the left even more, so you need to add right rudder. I would say it’s wrong, but maybe I am wrong. That’s how I feel it and you usually get in the sim, if the instructor wants to have fun.
Cheers.

[c.w.nelson]

Hi guys

Yes, that book certainly does sound mixed up. If you were to lose engine 1, the resulting yaw (to the left in that particular case) would most certainly be INCREASED by the influence of a crosswind from the left. This crosswind would indeed attempt to weathercock the aircraft in the same direction as the assymetric yaw. As popay correctly pointed out, the presence of keel behind the aircraft's CG will always attempt to cock the aircraft into wind and hence the book doesn't seem to make much sense!
A publishing error perhaps?

Hope this helped
Best Regards

[RoyHudd]

Is the author at bmi (LHR). Just curious.

[ATIS]

Another one to watch out for which had me puzzled was the topic on dutch roll. The author states that the upgoing wing stalls and so therefore drops. Surely you'd feel pre stall buffet. Other books state that its the opposing force on the fin that keeps the motion going.

[Tamilvimani]

Thanks for all your replies. I am glad some of you agree with me. I always feel that one's own logic has to be satisfied before a proposition or answer can be accepted.

tamilvimani