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# ATPL theory questions

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# ATPL theory questions

7th Jul 2016, 23:48

Join Date: Apr 2015
Location: Airport
Posts: 72
Hi Alex, both in BGS (i've been told) and atplonline(confirmed) they have this question wrong:

Which of these statements about a reaction turbine are correct or incorrect?
It's considered that it's the same question as this one:
Which of these statements about an impulse turbine are correct or incorrect?

But they are different things. Can you confirm me that it's like this in BGS too? In class we have been taught that are different things and pressure in stator and rotor difers depending if its reaction turbine or impulse turbine.

Cheers.
8th Jul 2016, 10:48

Join Date: May 1999
Location: Bristol, England
Age: 60
Posts: 1,472
Oh this question! I will ask my CGI so I don't embarrass myself by giving you inexact information.
8th Jul 2016, 12:02

Join Date: May 1999
Location: Bristol, England
Age: 60
Posts: 1,472
From my CGI, John Crosland:

This has been a hot topic for some time, mainly because reference books are cagey in their writing and many of the early exam questions had incorrect answers. We have edited BGS Online to reflect the current situation, don't know about ATP Online.

This is quoted from Rolls Royce – the Jet Engine.

“TURBINE TYPES
There are three types of turbine: impulse, reaction, and a combination of the two known as impulse-reaction.

In the impulse reaction type turbine, the pressure drop across each stage occurs in the fixed NVG, which, because of its convergent shape, increase the gas velocity while reducing pressure. The gas is directed onto the turbine blades, which experience an impulse force caused by the impact of the gasflow on the blades.

In the reaction type, the fixed NVGs are designed to alter the flow direction only, without changing pressure. The converging blade passages experience a reaction force resulting from the expansion and acceleration of the gas.

Normally, modern gas turbines rely on the combination of both design styles, and modern aerodynamic design methods enable the characteristics of components to be tailored to maximise work output and stage efficiency.”

John has given me the lists below which he thinks are correct. Caution, the few remaining exam questions may still have arguably incorrect answers.

Impulse turbine
Nozzle guide vanes
Pressure down
Temperature down
Velocity up

Pressure same
Temperature same
Velocity down

Reaction turbine
Nozzle guide vanes
Pressure same
Temperature same
Velocity same
Direction change

Pressure down
Temperature down
Velocity up
8th Jul 2016, 18:46

Join Date: Apr 2015
Location: Airport
Posts: 72
Yes that's exactly how it is! So in the CAA exams they have it like this too? Thanks
13th Jul 2016, 19:45

Join Date: Apr 2015
Location: Airport
Posts: 72
Hi Alex, I came up with some ambiguity in a question in Met and Comms. It's when you have to file a special air report when you encounter a few elements in flight. In Met questions you are suposed to file it when you encounter SEVERE turbulence, mountain waves...
but in comms it's when you encounter MODERATE OR SEVERE for the same elements.

Do you know if CAA has changed this recently in their system as valid question? Thanks a lot!!
14th Jul 2016, 09:48

Join Date: May 1999
Location: Bristol, England
Age: 60
Posts: 1,472
The contents of a routine AIREP include turbulence of any category. A special AIREP is required when encountering severe turbulence (and a list of other phenomenon which affect the safety of aircraft). I can find a question in our databases in met which says 'all pilots encountering turbulence are requested to report it' and then leads on to test a definition of moderate turbulence, but I can't find either a question in met testing the requirement for 'severe' as against 'moderate' in a special AIREP or the equivalent question you quote in Comms. May I ask where the questions came from?
16th Jul 2016, 13:43

Join Date: May 2008
Location: UK
Posts: 522
Hi all. Is anyone able to update on the current situation regarding the concentration on new LO's and associated additional, sometimes obscure questions?

From recent experience I'd noted HPL had been tickled a bit (no bad thing as it used to be a bit of a joke), Instruments had a bit of new stuff, Gen Nav seemed easier and Met again a slight tickle but the weather's the weather. Speaking to others at the exam venue and looking on here, Op Proc and Air law sound like they've been hit badly along with Comms? Are any other subjects to be treated with caution? Thanks in advance.
17th Jul 2016, 18:31

Join Date: Apr 2015
Location: Airport
Posts: 72
I will check tomorrow probably Alex, regarding the Moderate/severe.

At constant RPM with a normally aspirated engine and a fixed pitch propeller, as altitude increases, if the mixture is not leaned:
The density of air entering the carburettor decreases and the fuel flow increases. INCORRECT.
Both the density of air entering the carburettor and the fuel flow decrease. CORRECT

Why are they considering that fuel flow will decrease?
18th Jul 2016, 10:52

Join Date: Apr 2015
Location: Airport
Posts: 72
BTW Alex, question 210754 is wrong in BGS, regarding the NGV and rotor in a reaction turbine. cheers.
18th Jul 2016, 14:48

Join Date: May 1999
Location: Bristol, England
Age: 60
Posts: 1,472
I will double check for you, but I think this one of the questions where the answer marked correct ..... isn't.
18th Jul 2016, 14:52

Join Date: Apr 2015
Location: Airport
Posts: 72
For the CAA i believe that NGV in a Reaction turbine are at constant pressure. I also found this one wrong: 210757. Its the same kind of question. Regards.

Can you confirm that CAA marks as valid that the pressure drops in the NGV in reaction turbine?

Another one i found which is contradicting other answers in BGS is this one: 210590
"The specific fuel consumption is inversely proportional to pressure altitude, at constant TAS." When the correct answer in most questions is that SFC increases/decreases SLIGHTLY with PA decreasing/increasing, so not inversely proportional and not directly proportional.

Last edited by flyfly4; 18th Jul 2016 at 15:04.
18th Jul 2016, 20:07

Join Date: Apr 2015
Location: Airport
Posts: 72
Interference (not unlawful) is 7700 mode A or C? In BGS QB it says mode A and in my book it says mode C.
19th Jul 2016, 08:48

Join Date: May 1999
Location: Bristol, England
Age: 60
Posts: 1,472
flyfly4, for your carburettor question did you look at the explanation? As altitude increases the air becomes less dense, less mass of air requires less fuel to maintain the mixture.

Concerning 210754 the question is:

"Which of these statements about a reaction turbine are correct or incorrect?

I. The pressure drops slightly across the nozzle guide vanes.
II. The pressure remains constant across the rotor blades."

and we say I is correct, II is incorrect which, given the options, I still think is correct. Again if you look at the explanation we see the suggestion that those that wrote the question believe the NGVs to be slightly convergent which will lead to a slight acceleration and a slight pressure drop. This would explain the answer which does not agree precisely with the Rolls Royce book.

210757 is similar, the explanation is similar.

210590 is:

"Regarding a jet engine:

I. The maximum thrust decreases as the pressure altitude increases.
II. The specific fuel consumption is inversely proportional to pressure altitude, at constant TAS."

'slightly' is not an option, but we would agree, and we say exactly that in the explanation. Never the less if PA increases by 60 units and SFC decreases by 1 unit it still is inversely proportional and so the answer "I is correct, II is correct" is true.

Unlawful interference is A7500, not 7700. From PANS-OPS "If there is unlawful interference with an aircraft in flight, the pilot-in-command shall attempt to set the transponder to Mode A Code 7500 in order to indicate the situation. If circumstances so warrant, Code 7700 should be used instead."

You should ask your training provider for their explanation. Who are they?

I cannot say what EASA/the CAA consider to be correct today, we only know what was said when these questions were queried in the past. We have no real-time feed!
19th Jul 2016, 10:23

Join Date: Apr 2015
Location: Airport
Posts: 72

I will check again for all the questions regarding SFC.

Regarding interference, I mean the Interference which is not unlawful. I know code 7700 should be set but in my book it says mode C and in BGS says mode A.

Regards!
19th Jul 2016, 11:57

Join Date: May 1999
Location: Bristol, England
Age: 60
Posts: 1,472
Interference which is not unlawful? Do you mean lawful interception?

The Mode A/Mode C confusion comes from light aircraft equipment which has a rotary selector that goes OFF/STBY/ON/ALT where ALT in this case means Mode A with altitude reporting but can convey the impression that Mode C exists as a discreet selectable mode. This can also make (badly written) questions confusing because one does not know whether the chap that made the question up is asking you to choose 'Mode A with altitude reporting' or trying to trick you into choosing the wrong mode. Mode C is not available on its own and you cannot select a code, it sends the encoded pressure altitude from either the ADC or the digitiser on the instrument itself. There used to be a Mode B on some equipment as well, and of course there is mode S, a selection usually referred to on the rotary switch just as XPNDR.

With the current EASA exams it is always better to go back to the source regulation and you see from my previous post how the requirement is laid out in PANS-OPS, albeit for 7500. It is quite specific "Mode A Code 7500". Yes, altitude reporting would be nice to have and help everybody concerned but that is not the requirement.

I'm afraid I don't know who wrote your book, but they are not helping you.
19th Jul 2016, 14:44

Join Date: Apr 2015
Location: Airport
Posts: 72

Regarding the question:
The EAT has to be transmitted to the pilot as soon as possible, in case the expected delay is:
10 minutes
5 minutes or more.

BGS says 5 minutes or more
ATPLonline says 10 minutes.

BGS explanation: "The correct answer is 10 minutes but we understand that the examiner has gone for 5 minutes as the answer to this question."
That means that EASA marks as correct 5 minutes?ż

Another:

Minimum Radar Separation on final approach
The minimum radar separation provided between aircraft established on the same localizer course shall be:
(plus additional longitudinal separation as required for wake turbulence)
ATPLonline 3NM
BGS 2.5 NM. (q 100314)
19th Jul 2016, 17:21

Join Date: Nov 2000
Location: White Waltham, Prestwick & Calgary
Age: 67
Posts: 3,748
Changes of over 5 minutes from the original time should be communicated by ATC as soon as possible.

I wonder if it's the usual bad phrasing?
20th Jul 2016, 11:44

Join Date: May 1999
Location: Bristol, England
Age: 60
Posts: 1,472
flyfly4,

PANS-ATM
6.5.7.1 An expected approach time shall be determined for an arriving aircraft that will be subjected to a delay of 10 minutes or more or such other period as has been determined by the appropriate authority. The expected approach time shall be transmitted to the aircraft as soon as practicable and preferably not later than at the commencement of its initial descent from cruising level. A revised expected approach time shall be transmitted to the aircraft without delay whenever it differs from that previously transmitted by 5 minutes or more, or such lesser period of time as has been established by the appropriate ATS authority or agreed between the ATS units concerned.
You will see there are two sorts of delay, an initial delay and a subsequent delay.

6.7.3.2.5 Subject to radar system and situation display capabilities, a minimum of 5.6 km (3.0 NM) radar separation shall be provided between aircraft on the same ILS localizer course or MLS final approach track unless
increased longitudinal separation is required due to wake turbulence or for other reasons.

Note 1.— See Chapter 8, 8.7.3.4.
Note 2.— An aircraft established on an ILS localizer course or MLS final approach track is separated from another aircraft established on an adjacent parallel ILS localizer course or MLS final approach track provided neither aircraft penetrates the NTZ as depicted on the situation display
.
but if you follow through the reference you find 3.0NM can be reduced to 2.5NM under some circumstances.

8.7.3 Separation minima based on ATS surveillance systems
8.7.3.1 Unless otherwise prescribed in accordance with 8.7.3.2 (with respect to radar), 8.7.3.3 or 8.7.3.4, or Chapter 6 (with respect to independent and dependent parallel approaches), the horizontal separation minimum based on
8.7.3.2 The radar separation minimum in 8.7.3.1 may, if so prescribed by the appropriate ATS authority, be reduced, but not below:
a) 5.6 km (3.0 NM) when radar capabilities at a given location so permit; and
b) 4.6 km (2.5 NM) between succeeding aircraft which are established on the same final approach track within 18.5 km (10 NM) of the runway end. A reduced separation minimum of 4.6 km (2.5 NM) may be applied,
provided:
i) the average runway occupancy time of landing aircraft is proven, by means such as data collection and statistical analysis and methods based on a theoretical model, not to exceed 50 seconds;
ii) braking action is reported as good and runway occupancy times are not adversely affected by runway contaminants such as slush, snow or ice;
iii) a radar system with appropriate azimuth and range resolution and an update rate of 5 seconds or less is used in combination with suitable radar displays; etc., etc.
You can find these documents online. Your groundschool should have them at least in electronic form and should be able to answer your queries.
20th Jul 2016, 12:23

Join Date: Apr 2015
Location: Airport
Posts: 72
Thanks a lot alex,
21st Jul 2016, 18:20

Join Date: Apr 2015
Location: Airport
Posts: 72
Contracting states shall not require the authorized agent or pilot-in-command to deliver to the public authorities concerned, before departure of the aircraft, more than some copies of General Declaration, Cargo Manifest and stores list. The numbers of the copies are :

In class we have been told that now its 3 of each. Is it the same for the CAA or we should stick to the old answer?