CFI Pop Quiz #109 - Lift and Load

[Chris Burgess]

What changes take place regarding lifting force and load factor produced by the rotor system when a gyroplane goes from straight and level flight into a 45 degree banked turn while maintaining constant altitude?

A) Total lift must increase; load factor will increase
B) Total lift must increase; load factor will remain constant.
C) Total lift will remain constant; load factor will increase.

[GyroRon]

I say it is A

[Paul_Zurawski]

Answer (A)

[Doug Riley]

If "lift" is carefully defined as the force that opposes gravity, then lift doesn't increase (the gyro still weighs the same). OTOH, rotor thrust does need to increase in order to provide centripetal force to make the turn. Therefore C is a better answer.

[JByrd]

There is the body axis (ref to the airplane) or the stability axis (ref the earth). I think the context of the question refers to the body axis since load factor is involved, therefore A.

Jim

[Chris Burgess]

Load factor increases in a 45 degree bank and additional lift is required to maintain altitude. "A" is the correct answer.

[Aussie_Paul]

If "lift" is carefully defined as the force that opposes gravity, then lift doesn't increase (the gyro still weighs the same). OTOH, rotor thrust does need to increase in order to provide centripetal force to make the turn. Therefore C is a better answer.

Doug, in a 45*bank the gyro weighs approx 30%?? more. At 60* bank angle it weighs double. Have I got something mixed up here??

Aussie Paul. :)

[Doug Riley]

Paul, I was trying to tease out the difference between real weight and apparent weight. Earth's gravity doesn't change because you happen to be turning. The pull of gravity on the gyro is exactly the same as during straight and level. The extra thrust that the rotor has to make is not to support the weight of the machine, but to create some additional force needed to pull the gyro around the turn -- centripetal force.

From the pilot's point of view, it might as well be real weight,though -- it feels like weight, and it makes the rotor work harder just like real weight.

Jim got even more subtle, bringing in the two different sets of definitions that different kinds of engineers would use.

[Brent Drake]

I think its C Due to the G force in a bank

[ventana7]

C is correct.

Doug,
It is generally referred to as horizontal component of lift. Since you are using a portion of the lift as a horizontal vector.

Or as Paul said the G force infact makes the gyro "weigh" more.

[Doug Riley]

Well, the FAA apparently wants it to be A, so those studying for the test should note that fact carefully. Often the expedient thing to do with these tests is to find out what the testers want and give it to them... even if you know better. The questions are sometimes ambiguous or vague and selecting the answer means picking the "least bad" one.

This particular question boils down to definitions, about which even knowledgeable folk have to agree in advance before they can talk to each other.

IMHO, the important thing to know outside of the test environment is that the rotor must work harder to effect a turn, and THAT will require either more angle of attack or more airspeed.... leading to a need for more power to hold altitude.

[Aussie_Paul]

Ok Doug, I see what you were getting at. Thanks.

Aussie Paul. :)

[Cobra Doc]

Actually, there be some pretty smart fellers in the FAA. (Doug, I know saw this coming and being the kind of guy I am...) Notice it says "load factor". The question doesn't address the variable of weight or the constant of mass. The correct answer be A.

[jdalexa]

Being that I learned from you Chris, I'm getting these. Wow, you really poured a lot of info into my head in the short period I trained with you.