Written Test Question

[rdebord]

Greetings
I am studying for my sport pilot airplane written test. I am using both the Gleim book and the asa test prep software. There is 1 question that is referenced in both where they have different answers as correct. Here is the question and possible answers.

What is the effect of advancing the throttle in flight?

A) Both aircraft ground speed and angle of attack will increase.
B) Airspeed will remain relatively constant but the aircraft will climb.
C) The aircraft will accelerate, which will cause a turn to the right.

According to Gleim the correct answer is A
According to ASA prepware the correct answer is B

I called ASA and talked to them and they said Gleim is not wrong and we are not wrong it is just different wording of the question. I told him the wording was exactly the same the only difference was the answers. He did not want to hear that and kept repeating neither of them had the wrong answer.
Can anyone shed any light on what answer the FAA considers to be correct?
Thanks

[3Dreaming]

I'm not sure which answer the FAA wants, but here is what happens and why.

An airplane has basically one specific angle of attack for each airspeed. To maintain level flight with that one angle of attack and airspeed there is basically one power setting for the given conditions that day. The angle of attack and airspeed numbers won't change, but the power required can change depending on weight and other factors. If you increase power the airplane will initially accelerate. This will cause it to pitch nose up, causing it to slow back down to the speed for which it was trimmed. Because of the excess power above what was needed for level flight the airplane will climb.

The real world answer is, "B) Airspeed will remain relatively constant but the aircraft will climb".

[Merlinspop]

I agree; B. If you're trimmed hands free and straight and level (as you should be and is a fair assumption for the question), adding power will cause the airplane to climb at about the same airspeed.

[Half Fast]

Both are incorrect. The effect of advancing the throttle in flight is that the engine coughs and dies and then the aircraft descends.

But since that's not one of the available choices, go with B.

[FastEddieB]

I think it's a terrible question, which is why there's debate over the correct answer.

It forces you to make assumptions.

IOW, are you advancing the throttle with hands off the controls? One answer.

Or are you pitching to maintain altitude, as you normally would? Another answer.

Even "C" is defensible - there are things built into a plane to correct for spiraling slipstream*. That will be ideal at normal cruise. If the advanced throttle took the plane out of that balanced range, it might actual yaw and ultimately turn right.

But a properly constructed question should have a clear best answer - I don't think this one does.


*One of those is to offset the leading edge of the vertical stabilizer to the left a few degrees. On some planes, like my Citabrias, that offset is clearly visible.

[rdebord]

Thanks for the replies. I agree the question is very poorly worded. I guess I will go with B if I get the question on the test. It seems like quite a few of the questions are poorly worded. I do not think they are doing a good job of determining your understanding of a subject if the question is worded wrong.

[HAPPYDAN]

As I recall, there used to be a similar question. Simply, "Advancing the throttle in fight will...." and the answer was simply "cause the airplane to climb". It sounds like the question and answers have been rewritten (to make them more confusing?). I vote B, although maybe a volunteer can go up and verify.

[Half Fast]

A, B, and C can all be correct. I would probably go with B since the increased airspeed would add downward force by the horizontal stabilizer thus pitching the nose up.

I'd go with B also, but I don't think I concur with your rationale. If the plane remains at the same angle of attack (no pitch up whatsoever), just increasing the throttle will increase airspeed, hence faster airflow over the wing, and hence more lift. Anytime Lift > Weight, the aircraft will climb.

[FastEddieB]

Anytime Lift > Weight, the aircraft will climb.

This can get very complicated very fast.

Here, it's more accurate to say, "Anytime Lift > Weight, the aircraft will accelerate upwards". Thereafter, the forces will again balance, but with the airplane still climbing.

I think. Like I said, it gets complicated.

[3Dreaming]

A, B, and C can all be correct. I would probably go with B since the increased airspeed would add downward force by the horizontal stabilizer thus pitching the nose up.

I'd go with B also, but I don't think I concur with your rationale. If the plane remains at the same angle of attack (no pitch up whatsoever), just increasing the throttle will increase airspeed, hence faster airflow over the wing, and hence more lift. Anytime Lift > Weight, the aircraft will climb.

Aircraft will climb due to increased lift from the wings. Angle of attack will increase due to increased downward force on horizontal stabilizer (many people don't realize the horizontal stabilizer exerts a downward force, not upward). Increased angle of attack will result in more increased lift and perhaps, reduced airspeed. That would depend on the amount of power added. It does get complicated.

When you increase power the airplane will start to accelerate. The increase in speed is what causes the increased down force on the tail causing the airplane to pitch up. Once pitched up the airplane will slow back down to the speed for which it was trimmed. The angle of attack will be the same as when the airplane was in level flight. However the pitch (deck) angle will be greater. Remember for each airspeed there is basically only one angle of attack. This is something I demonstrate to students on the second or third lesson.

[rdebord]

Anytime Lift > Weight, the aircraft will climb.

This can get very complicated very fast.

Here, it's more accurate to say, "Anytime Lift > Weight, the aircraft will accelerate upwards". Thereafter, the forces will again balance, but with the airplane still climbing.

I think. Like I said, it gets complicated.

I got an email response from gleim today. They had C as the correct answer. They referred me to chapter 4 of the "Handbook of Aeronautical Knowledge". Here is the language he used.
"During straight-and -level flight when thrust is increased and the airspeed increases, the AOA must be decreased. That is,if changes have been coordinated, the aircraft will remain in level flight, but at a higher speed when the proper relationship between thrust and AOA is established. If the AOA were not coordinated (decreased) with an increase of thrust, the aircraft would climb. But decreasing the AOA modifies the lift, keeping it equal to the weight, and the aircraft remains in level flight."

Thanks again for all the replies to my question.

[Merlinspop]

Whether you get this question on the test, this would be an excellent thing to bring up during your oral exam. You could probably get the examiner going for 20 minutes on this one.

[drseti]

Option B is the most consistent with the way I teach. But the best answer is D - fuel burn will increase.

[FastEddieB]

Option B is the most consistent with the way I teach. But the best answer is D - fuel burn will increase.

Assuming you don't concurrently lean the mixture!

Way to many assumptions need to be made on this one!

[3Dreaming]

Option B is the most consistent with the way I teach. But the best answer is D - fuel burn will increase.

Assuming you don't concurrently lean the mixture!

Way to many assumptions need to be made on this one!

I tell my students, don't over think it. Answer the question as asked without assuming anything. In my opinion from teaching ground school the past 6 years, The FAA puts the specific words they want in the questions. If you go making assumptions you are adding something to the equation the FAA did not want there.