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ATPL exams are not fair!

Old 26th Apr 2021, 17:38
  #41 (permalink)  
 
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It was bad enough when I did my ATPL in the 90s. Being an electronics engineer, I had to essentially ignore all of my personal knowledge and learn the explanations that the CAA thought were right. I could understand why things like Air Law needed memorisation as there was little logic, but if you used sound scientific principles in many of the technical subjects you ended up with the wrong answer.

Can’t imagine how difficult it is these days...
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Old 26th Apr 2021, 18:21
  #42 (permalink)  

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I've been through mine in 2001. It is sad to read the whole thing still is a functional prototype.

BTW, anyone remembers "Four Forces Aviation"?
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Old 26th Apr 2021, 18:45
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Remember briefly using Four Forces Aviation ground school notes for a time. Didn't seem to last too long, if I remember correctly there might have been some legal or copyright issues?
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Old 26th Apr 2021, 20:57
  #44 (permalink)  
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bulldog89

Okay, so I just tried VNAV via FMS on a 737, without autothrottle, no problem, although i had to control the throttle obviously. So if someone is saying the right answer is autothrottle, they're wrong. If anything it's pitch control, but of course the better answer would be the pitch channel of the autopilot. Trouble is, a student might know that and won't have to pay for another exam 😒
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Old 26th Apr 2021, 22:18
  #45 (permalink)  
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In 1993 I was one of the first people to take the new HPL exam for the PPL, which was newly introduced. I just learned the material and passed.

There was a chap at the club who failed it at about the same time. He was, of course, a medical doctor
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Old 27th Apr 2021, 02:12
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Genghis the Engineer

Okay that makes a lot of sense. I get it now thanks

Last edited by Sleepsleep; 8th May 2023 at 09:38. Reason: cringe removal
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Old 27th Apr 2021, 03:46
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PFD

This question is exactly why I DID use the banks (yes, more than one).

Anyway, it is also clear that the question is referring to a fully automated VNAV, so both auto pitch and throttle are needed. It is also to be said that it would be possible to design a fully automated VNAV system without controlling the pitch angle, but not without auto-power/thrust control.
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Old 27th Apr 2021, 07:40
  #48 (permalink)  
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Now you’re just trying to justify your answer. Where in the question does it say Fully Automated and what aircraft is it? Also could you explain how VNAV PTH is possible at varying air speeds without controlling pitch angle? I’m intrigued.
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Old 27th Apr 2021, 11:17
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I don't have to justify anything to you.
I answered correctly because I've finished my exams last year, using the banks.
This being said if I remember correctly on the 737 as an example the vertical profile is managed with alt, vspeed, airspeed and elevator deflection.
It would also be possible to design a VNAV system based on the AoA or any other useful reference (es: accelerometers), but not without controlling the engines. Anything without engines control is not an automated VNAV system.
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Old 27th Apr 2021, 12:56
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I think the point is, Bulldog, you are arguing a posteriori because you know what the marked correct answer is. We have to put ourselves in the position of a candidate who does not have that knowledge, but otherwise understands the system, and that would make that a very difficult question to answer, likely resulting in the 'pitch controller' being chosen.
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Old 27th Apr 2021, 13:38
  #51 (permalink)  
 
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PFD

It will maintain VNAV path regardless of airspeed until it reverts to VNAV SPD. In VNAV ALT it would hold altitude until the stall. So I agree with you, but there is no logic in ATPL exams.
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Old 27th Apr 2021, 14:10
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You can control altitude with an auto-throttle but not, necessarily, a pitch controller.

If you use the throttles only, the aeroplane will - with a bit of lag - maintain the trimmed speed, and climb or descend according to the excess or deficiency of thrust. (Steady state climb performance is dictated by how much more - or less - thrust than gravity you have, and not the pitch angle of the aircraft or power of the elevator. Otherwise you could steadily climb quite nicely in any glider just by pulling back on the stick.)

Pitch alone, on the other hand, is inadequate because the thrust setting can still endanger the aircraft. For instance, the thrust may be to low to safely climb the aircraft without losing speed and stalling, but the aircraft pitches up anyway. Or you may have too much power and you exceed VNE as you pitch down for the descent. You still need to control throttle setting by hand, but you don't have to control pitch by hand, so long as the aircraft is trimmed to fly at the speed you want it to.

In reality you would use both pitch and power for a VNAV controller (pitch to prevent "long-period" oscillation round the climb angle and power to establish the climb rate) but if you could only use one it would have to be power.
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Old 27th Apr 2021, 15:50
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But 'thrust' is not encompassed in the term 'autothrottle', Cap'n, you can set manual thrust. This is the 'thrust' of the argument. Climb angle (FPA) is defined by (thrust-drag)/weight. This is why gliders cannot climb like a powered aircraft, no thrust. They are converting kinetic energy to potential energy.
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Old 27th Apr 2021, 18:56
  #54 (permalink)  
 
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Sure! You could set manual thrust in the same way you can set manual pitch trim.

But thrust would need to vary, however, unlike trim, for climb and descent.

And remember, the question asks what the most basic requirement of an automatic VNAV capability is.

Which is the most basic: auto-throttle only (one system) or pitch controller + pilot controlled throttle? (two systems - for the sake of argument, pretend the pilot is glued to the aeroplane.) In other words, which requires the least amount of interaction with the aircraft?

It's auto-throttle alone.

Yes, both methods will produce a working VNAV controller, but this is yet again one of those questions where you have to get into the head of the examiner and choose the most-right answer.

Which brings us to the point above that the question banks aren't fit for purpose because they shouldn't require mental gymnastics like this.

(Also you are quite correct about climb performance being excess thrust over weight, not gravity. Ooops. Been a few years since I've done this.)
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Old 27th Apr 2021, 21:32
  #55 (permalink)  
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bulldog89

Hmm so you’re saying that if you are in VNAV with the autopilot on, on a 737 and you are controlling the throttles, that it isn’t automated?
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Old 28th Apr 2021, 05:27
  #56 (permalink)  
 
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Just stop. The question is not type specific, and ATHR+manual pitch is just as valid as AP+manual throttle.

Being type specific I've already told you that on the 737 the VNAV profile is obtained without using the pitch angle as an input.
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Old 28th Apr 2021, 05:39
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Alex Whittingham

To be honest I've picked the correct answer on the first try: then the banks confirmed I could do the same in the real exreal exam.

The point is that an instructor is trying to use this question as an example of ""wrong answers in the exams", but this is not the case. It's an ambiguous question for sure, but in my opinion the correct answer is (as usual) just "the most correct answer". Again, this is exactly why the banks are made for.
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Old 28th Apr 2021, 05:54
  #58 (permalink)  
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bulldog89

You clearly don’t understand what happens in VNAV especially in VNAV PTH. What about the aircraft that have a VNAV mode and no auto throttle?

But from your other replies, yes you’re right, the question is ambiguous. It talks about a ‘system’ and Autothrottle certainly is, so maybe it’s the right answer in the question writers head, who knows, and there’s the problem, who knows?

Now tell someone who didn’t just “Bank it” and got 74% that the exams are fair.

BTW, just because the banks (ATPLQ?) say it’s the right answer, doesn’t mean it is.
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Old 28th Apr 2021, 11:12
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Please, tell us again how it would be possibile to auto climb and level with constant speed in VNAV without an automated engines control.
From the study material is crystal clear that VNAV is to be intended as a fully automated flight, not some form of hybrid systems with 3/axis control and manual engines management.

Anyway, for the third time, the 737 doesn't use the pitch angle to control the VNAV path, AT on or off.

Edit: Wait a minute. I've never said I've just banked it...I studied and used the banks, it's a different thing.

Last edited by bulldog89; 28th Apr 2021 at 11:35.
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Old 28th Apr 2021, 11:22
  #60 (permalink)  

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I fly a Challenger 350 with Collins Proline 21 avionics and autopilot. We don't have autothrottles. We can use VNAV for descent and climb but we have to "be the autothrottle". As we also do RNAV approaches (LPV etc) and therefore VNAV must be engaged, I'd say you can use VNAV without autothrottles....

Now what the ATPL exams want is another thing, they are not based in reality most of the time.
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