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Crossunder
12th Dec 2003, 18:03
Hi all!

Your aircraft is in a descend, with a pitch down attitude. You then decide to pitch even more down. Has the pitch angle now increased or decreased? I'd say it has increased, because the angle between a/c long. axis and the horizon has increased, but some say that the already negative angle is now even "more negative", thus meaning that the pitch angle has decreased?
Any of you techies out there with a clear definition on this, as this is creating some confusion on the ATPL PE exam...

Thanks.

Port Strobe
12th Dec 2003, 18:46
I don't know for sure in the exact context you're referring to but assuming there is some sort of remotely methodical sign convention applied to this then I'd say it must decrease, since -5 is less than -3 say for example. If it doesn't follow this then by saying increasing pitch angle it is still fairly ambiguous, whereas using a proper sign convention removes the ambiguity and can only mean pitching down, be it from +10 to +5 or -1 to -3, it doesn't matter.

Hope this helps a bit, and I'll repeat that I don't know for sure in this specific application, so if someone does know then I'm open to correction but this seems by far the most sensible way to tackle this problem.

Crossunder
12th Dec 2003, 19:45
To clarify:


14. Pitch angle during descent at a constant mach number will:

a) Increase.
b) Decrease.
c) Increase at first then decrease.
d) Stay constant.


Another example of not knowing which answer to pick, even though you know exactly what will happen to TAS vs. altitude and MNo etc. Obviously you'd have to pitch more down in order to achieve a higher TAS when Local Sped of Sound increases.

Captain Stable
12th Dec 2003, 20:18
Given the phrasing of the question, I would say that the pitch angle increases.

mono
12th Dec 2003, 20:19
Pitch angle decreases, angle of descent increases.

With this sort of question I was always taught that it is best to further clarify your answer on a separate sheet, as you have done in your previous post. This shows the examiner that you understand the theory and have a dispute with regard to the phrasing of the original question

Maximum
12th Dec 2003, 20:29
long time since I was involved in ATPL exams, but applying the terminology used in the real world, when instructing I would say, for example, "increase your nose-down pitch attitude to maintain a constant mach number". Likewise, "decrease your nose-down pitch attitude to reduce speed".

Another way of thinking about it, look at the markings on the artificial horizon - they don't have a minus number for nose down -they simply increase away from zero degrees in both directions, nose up and nose down.

So, my answer to the question using this logic would be:
a.) increase.

Unfortunately however, who can ever be 100% sure that the powers that be are using the same logic?;)

safetypee
13th Dec 2003, 00:24
I agree with Maximum.
Is it too much to expect that examiners will relate their questions to the operation of real aircraft from the flight deck? If they were to do so then pitching the aircraft more nose down increases the attitude. Just refer to the ADI / EFIS, the numbers get larger. All the fancy aerodynamics / engineering speak of positive and negative is taken care of by the brown / blue bits.
KISS

FE Hoppy
13th Dec 2003, 01:09
a) Increase


I think the question is fine. When do we ever use - or + ?
Never its up or down increasing in both directions from 0.

Captain Stable
13th Dec 2003, 01:16
FE Hoppy - agreed 100%.

Imagine you sitting in the right-hand seat, in the descent, and the skipper says "I suggest you increase the pitch angle a tad".

What are you going to do? Which way do you take the nose?

ALL common sense says "down".

Keith.Williams.
13th Dec 2003, 22:48
This is one of those cases where perfectly logical arguments can be given for two diametrically opposite answers.

It is a JAR ATPL Performance question and different schools teach different inerpretations. So if every student remembers axactly what they have been taught, some will get the mark in the examination and some will not.

The real problem is that the CAA do not do any meaningful analysis of exam results. Worse still, they hold copies of the notes used by each of the schools, but spend little or no time examining and comparing them. If they did any meaningful analysis, they could identify the areas in which each school was doing badly and get them to sort out their problems.

After each examination most schools lodge a number of appeals. In a few cases these are successful. But the CAA are very secretive and do not discuss questions openly. The most common response to appeals is "inaccurate feedback". They rarely give any further explanation for the rejection of an appeal.

In the case of the pitch atitude in a constant mach descent question, I always advise my students to pick the "increase" option and to lodge an appeal based on the fact that different schools and different text books give different definitions. Sadly the CAA response appears to be to view these appeals as "Oh no not that old chestnut again....will these students never learn?"

Problem, What problem?????

*Lancer*
14th Dec 2003, 15:02
Every manual I've ever seen talks about Pitch UP and Pitch DOWN rather than positive or negative pitch... PFDs have pitch angles marked, but not in '+' or '-'

I've always thought of it as increasing the pitch down, not decreasing the pitch...

WillieTonka
25th Nov 2005, 07:22
When describing aeroplane pitch angles all aircrew will start from a level attitude and then measure all angles from there. They will talk about pitch up and pitch down. If they want to descibe an aircraft that is increasing its angle of climb they will say that the aircraft is pitching up and when increasing it's angle of descent they will say that it is pitching down. Like everything in aviation it avoids confusion by getting the message across unambiguously. Like many others, I really don't understand why the CAA have chosen to cloud this very simple everyday terminology in their exams. If you want to get the answer correct you have to tick (b) decreases. This is a bit like a driving examiner saying that he would like you to decrease your turn angle when what he really means is that he wants you to turn left! Why are they trying to confuse us? In my view the correct answer should be 'increased pitch down attitude". After all the climb/dive angle numbers on the ADI are increasing in both directions from level, aren't they?

Pilot Pete
25th Nov 2005, 12:49
the skipper says "I suggest you increase the pitch angle a tad".

As a 'skipper', I would use better communication and be less ambiguous with my F/O and actually say;

"I think you want to pitch down a tad more old chum", or depending on urgency; "PITCH, PITCH!" or ultimately; "I have control!"

Glad to hear you lot aren't getting it any easier than in my day!:p
Bless the cotton socks of the CAA eh?

Good luck.

PP

bookworm
25th Nov 2005, 14:37
I remember reading a chirp-like report about an FO flying an approach, whose skipper suggested that he "put the flap in". The resulting action was the opposite of what the skipper intended.

Anything that relies on a sign convention is open to misinterpretation. It would be good practice to phrase questions unambiguously.

Capt Pit Bull
26th Nov 2005, 09:21
The basic issue here is that of you don't define a proper system of coordinates, you are screwed.

As soon as you start sayings things like "its an increase in this case but a decrease in another case" you should be getting a sense of a poorly constructed coordinate system.

Unfortunately we have this in aviation.

e.g. write down the equations for a climb, as taught in your typical pilots ground school.

they are based on climb angle.

Repeat for the descent.

they are based on descent angle.

If you compare the equations you will note they are exactly the same except for the presence of a minus sign anytime the angle crops up.

In otherwords you couild just have one set of equations, say for the climb, with the proviso that if the answer comes out negative your climb is negative (i.e. a descent).

This thread is a good example of non standardisation and the need for professionals in any technical field to have a decent scientific education.

Unfortunately we don't have such a thing any more.

CPB

mupepe
26th Nov 2005, 11:57
"Another example of not knowing which answer to pick, even though you know exactly what will happen to TAS vs. altitude and MNo etc. Obviously you'd have to pitch more down in order to achieve a higher TAS when Local Sped of Sound increases."
If you keep constant Mach while descending, your TAS/EAS will increase so basically you'll have to decrease pitch for this question :confused: NO

Keith.Williams.
26th Nov 2005, 17:43
All of the schools have learned much more about the JAA CQB since my earlier post in this thread. It is now widely known that the answer to this question is that pitch angle decreases in a constant mach descent. So if the objective is to get the mark in the examination, then "decreases" is the one to pick.

A similar problem concerned the question of why step climbs are carried out. The options included "to comply with ATC requirements" (or words to that effect), and "to maximise range"(or words to that effect). Different schools argued for different options. It is now known that the JAA answer is "to fly as close as possible to the optimum altitude as aeroplane mass reduces".

These answers have been proved to be correct (or at least to be the ones that get the marks in the exam) by various students who have scored 100% in the Performance exam.