It's in the question...

I didn’t say “you” banked it. Anyway. How do you explain that VNAV appears in the pitch channel window of the FMA and the Autothrottle is only ever on the left and can only do a thrust or speed (IAS or Mach) are you still sure that pitch is not in VNAV? Have you asked your old Inst instructor? Just constantly referring us to the bank answer in an ambiguous question isn’t the answer.

We all know what EASA questions are like, they won’t say autopilot or pitch channel, that is too easy, so pitch controller sounds more EASAeze. If you seriously think pitch changes are not required in VNAV, you need to have another good read of your learning material.

From my previous post:
My learning about it has been verified multiple times with open answer/oral exams. No need to ask "my instr instructor" or to "check my learning material".

Still waiting to read how the FMS can control the vertical navigation without controlling the engines.

Well I'm very pleased for you, Bulldog. You sound very confident. Good luck!

bulldog89

In the cruise it's quite simple: Pitch controls altitude, thrust controls speed. Auto or manual thrust is irrelevant.

VNAV in a Boeing is a complicated beast and understanding the FMAs as they change is vital. Pitch can be used to control Speed, Altitude, Rate of climb, Flare etc.. Whilst Thrust can also be used to control Speed, Altitude, Rate of climb etc - the only difference being the phase of flight.
It's a subject that (in detail) belongs in a type rating course, not the ATPLs.

Manual thrust, level flught: T needed 70, T set 10. FMS unable to maintain altitude, even with no speed profile set, VNAV disengages.

rudestuff

Hi, thanks for your input. I don’t wish to contradict you, but in what mode does thrust control altitude? Auto thrust modes are Thrust (N1, Climb, TO/GA ETC) Idle (During Level Chg descents and at the end of FLARE) and speed control (MCP or FMC). Anything to do with ALT or Path is Pitch Channel of the Autopilot. VNAV rate of climb will either be similar to Lvl Chg, where AP controls the IAS/Mach and a climb thrust is set, or the FMC will set a particular rate of climb in pitch combined with an Autothrust Speed.

You’re right of course, it is very type specific, but generically it’s 737 or A320 and something has to be taught to the students. I tend to concentrate on the follies of VS mode, you know, the danger of over or under speeding, and the fact that unlike Level Change, it doesn’t look specifically for an MCP set altitude, unless you are going that way.

bulldog89

Yes because YOU have mishandled the manual thrust. If you observed what was happening as the speed was dropping, the pitch angle would have been increasing to increase AoA and lift, until you approached the stall. I’m having to assume that you were asking VNAV to maintain a flight level but withought the leg information I don’t know, and how can you have an FMC VNAV profile without it calculating speeds?

mgahan

Totally agree.
It is an utter travesty that exams can be passed simply by rote-learning the question bank and makes a complete mockery of the entire ground training system. One can only question the professional attitude of candidates who think this is the correct way to pass an exam, and fear for the level of their theoretical knowlege.
It scares me when I hear kids saying "what's that got to do with aviation" - that demonstrates they don't even understand the reasons they're supposed to be absorbing knowlege, a far more fundamental failing in attitude even than whingeing they can't get access to the answers to save them learning the hows and whys.
There sounds to me to be an excessive amount of 'entitlement' going on here, people complaining they don't need background knowlege ("why do I need to know the density of Jet A1" for instance - ffs!) to enter a highly technical profession where a massive knowlege base - but expect it to handed them on a plate for the asking.

PFD

Dear PFD, this is my last message about this question as you're just avoiding the point. YOU posted a question saying "for the FMS to control", not me, not you, not "I'll just manage the throttles", just THE FMS. So, please stick to rule #1 of these stupid exams and RTFQ. In case you've already read TFQ, please tell us how is it possible for THE FMS to control climb, cruise and descent without controlling the engines.

And again, on your beloved 737 changes in pitch are just a consequence of the AP trying to correct the vertical speed it sensed, changing the elevator deflection to regain a suitable vertical speed to reach the target altitude. And no, you don't change elev defl to chase a target pitch angle, you do it to increase/decrease AoA and the Vspeed. You'd be able to finish a mechanics of flight course without even mentioning the pitch angle, it's quite irrelevant.

It's not desirable, but let's say you descend using FLCH: pitch controls speed, AT goes to IDLE then THR HOLD allowing you to adjust the thrust levers to control RoD. If you add too much power you'll actually stop the descent, and you're inadvertently controlling altitude with thrust. Add even more power and you'll actually start to climb even though it was supposed to be a descent, and with no MCP altitude to ALT CAP on, it'll keep going until it finds its equilibrium Altitude.

It manifests itself in the SIM on single engine work. I've seen someone descending, getting close to the platform ALT with manual thrust, pitch for speed. They noticed the speed was a little low and added power but it hadn't yet alt capped - so all that did was arrest the descent. When they saw that the speed hang changed, they added more power and started to climb. 🤦‍♂️

rudestuff

After THR HOLD, if you wanted to push up the power, wouldn't you have to disarm the AT though? I agree with everything you've said there by the way, and agree that if you manually increased thrust, to control speed the AP would pitch up, but the throttle isn't really "controlling" altitude, just influencing it, don't you agree? Anyway, this whole debate highlights the fact that some ATPL questions are debatable, literally, and therefore ambiguous.

At the end of the day, there are still many aircraft that have an FMS VNAV mode and no autothrottle.

bulldog89

Blimey mate, you're all over the place, you seem to be saying that VNAV DOES include pitch control, which of course it does. You also seem to think that the AP doesn't hold an altitude, just a VS.

If you do RTFQ, it says for the FMS to control vertical navigation and since you've been told that there are aircraft without autothrottle many times, that do have an FMS and VNAV, I can only assume you are just choosing to ignore that. Good luck trying to fly a complete VNAV profile without changing the aircraft pitch angle at any time, meaning attitude of course, and although I now teach Pilots, I am an ex Aircraft Engineering Technician, and seem to recall pitch angle being mentioned a few times. Maybe my apprenticeship of 3 years was a little more extensive than yours? let's just agree to disagree, and good luck flying without pitch control 😉

Genghis the Engineer

Always good to have these values committed to memory for the purpose of sanity checks. We have, however, found that the actual exams give values that differ from the ones commonly used in practice. One such example:Given: Fuel density = 0,78 kg/l Dry operating mass = 33500 kg Traffic load = 10 600 kg Maximum allowable take-off mass = 66200 kg Taxi fuel = 200 kg Tank capacity = 22 500 Litres The maximum possible take-off fuel is?

A. 17 550 kg

B. 17 350 kg

C. 21 900 kg

D. 22 100 kg


*with permission from Status Aviation - Home

The ATPL exams (or any other pilot theory exams) are a bloody joke and everybody knows it.

People just go through them, forget and move on. It's frustrating to hear to the people currently doing them, but that's the best advice: suck it up, finish them as quickly as possible, then move on!

rudestuff

That's true, but it's still a bit of a stretch to say that you can control ALTITUDE using THRUST in the FLCH mode. What's more accurate is saying that you can control VERTICAL SPEED using THRUST. As you say, indirectly by modulating the thrust, and therefore the vertical speed, you could theoretically maintain an altitude like that. But this is a retarded way to fly and nobody does this (or nobody does this intentionally at least...)

No, in THR HOLD the servos are disconnected leaving the levers free for the pilot to manipulate. No need to disarm AT.

Thank you for that. I knew that was the case on Take Off, didn’t realise it was the same in descent.

Central Scrutinizer

Agreed. You would never operate like that, I was merely trying to show that all flight modes are a combination of pitch and power and that what-controls-what depends on the FMAs at the time, and ultimately that VNAV is pretty complicated!

Percy van Staden

Clear-cut 17350 from me. Where did I go wrong?

The incorrect answers are picked smartly on this one, btw.