Weight, Wind
 

Starting my posting career here with homework help, I guess that is as expected. Im currently doing the performance portion of my ATPL(A) and I've been trying to wrap my head around a few concepts, I'm a fairly low time pilot (1000TT Light AC with about 850 as an instructor) with training from the US converting my licenses in Norway.

As Ive seen, people are not too fond of outright "what is the answer to my question"-threads, so I'll try first, then see how far off I am. Unfortunately, the Oxford book is pretty short on information about this subject, not really giving me what I'm looking for. If there are other databases where I can soak up information like this, tips are appreciated.



An airplane is descending with a constant IAS and zero thrust. What happens to the descent gradient when the OAT increases?

Pretty lost at this one. Safe to say, if this was a climb the answer would be obvious, the low air density would result in worse climb performance. Is it safe to assume that the opposite is true for descent gradient? That the lower air density would result in less parasite drag and therefore allowing me to keep a lower descent gradient in an engine out situation?



An airplane is descending with a constant IAS and zero thrust. What happens to the descent gradient when the airplane reaches a lower altitude?

As my only answer to the last question was as mentioned, I would now assume that due to the air density increasing as we reach lower altitudes, parasite drag would again increase and force a higher descent gradient. From reading about configuration and its effects, it seems that more drag will increase the gradient. But I also want to clarify that this is not due to the pitch down moment often associated with extending flaps and gear.




An airplane is descending with a constant IAS. What happens to the descent path gradient when tailwind is increasing?

I think I got this one, but we'll bring it in anyway, since gradient is directly related to groundspeed, I would assume that a higher ground speed would increase my gradient. Am I underthinking this?



Hopefully this doesnt annoy anyone, as I have atleast tried to come up with a homemade solution to this, feel free to flame my incompetence! (Starting to wonder if I'll even survive the ATPL(A))

EDIT: Thread title is messed up, unfortunately I cant find a way to edit it

Hey odd ball... and the below is just my opinion. You might want to double check it with the textbooks, as i might make mistakes too, that you have already have the answers are in there.

1)An airplane is descending with a constant IAS and zero thrust. What happens to the descent gradient when the OAT increases?

Please revisit the lift equation.
Constant IAS - constant Q factor.
OAT increase - increase/decrease what variable of the lift equations

what needs to be compensated to maintain the same Q factor.

FYI you might want to revisit the chapter on drag, if you are maintaining the same IAS drag remains the same...

it should bring you to the conclusion that the gradient increases.

2) An airplane is descending with a constant IAS and zero thrust. What happens to the descent gradient when the airplane reaches a lower altitude?

in this case the steps to analysis this is the same as the first question, however you do not compare/consider OAT as a factor at a instantaneous point. you compare the conditions at different altitude.

it should bring you to the conclusion that the gradient decreases, as with a down drift.

3)An airplane is descending with a constant IAS. What happens to the descent path gradient when tailwind is increasing?

I believe you want to revisit part in the book defining gradient (air/ground). air gradient is independent of wind.

tailwind decreases the ground gradient and and actual flight path angle will reduce accordingly.

Oxygen requirements - I don't get it!
 

I think I'm being stupid.
Question concerns supply requirements for supplemental oxygen for passengers in a pressurised aeroplane.
The book says:
100% of passengers: entire flight time when cabin altitude exceeds 15,000 feet but in no case less than 10 minutes.
30% of passengers: entire flight time when cabin altitude exceeds 14,000 feet but does not exceed 15,000 feet
10% of passengers: entire flight time when the cabin altitude exceeds 10,000 feet but does not exceed 14,000 feet after the first 30 minutes at this altitude.
OK so after a pressurisation failure and cabin altitude becomes 14,500 feet who decides which 30% of passengers get the oxygen and which don't?
And how does the operator know in advance how much oxygen to supply if they can't know in advance what cabin altitude the failure will cause?
I think I'm missing something very simple here

I'll have a go at this:
An airplane is descending with a constant IAS and zero thrust. What happens to the descent gradient when the OAT increases?

No change in descent gradient.
Descent gradient (much like the climb gradient) is a function of excess drag vs weight (ie. (D-T)/W ). Since thrust is zero for our question, we can use D/W. Neither changes so the air gradient will remain the same.

Hotter (or colder) air does not imply less drag if we are flying at constant IAS. Assuming no compressiblity, const IAS implies constant EAS and constant q. Weight is constant, Lift is constant, density will increase(or decrease), but speed changes to adjust for it (TAS will therefore change), Cl remains constant (as in the angle of attack is constant).If Cl (and angle of attack remains the same) so wil Cd and Drag.

I am half-way through my ATPL (H) exams, so far so good. Are average marks for each subject available in the public domain? It would be interesting to see how I measure up - it is a competition after all.

Basic ATPL QFE. question
 

I am not struggling with this and understand the differences etc, but just trying to make sense of an answer without the workings given.

According to the Met Handbook.... '1hPa change per 27ft of pressure change down to sea level"

The question goes something along the lines of

"If the QNH at Coventry (200 meters above sea level) is 1025 hPa, wha is the approximate QFE?"

My working is:

200/27 = 7.4 - round down to 7.

1025 - 7 = 1018 - A minus as the QFE would be lower than the QNH.

My answer QFE = 1018.

The answer however is 1000 HpA .

Just wondered if the mathematical derivation of this is using the above rule of "1hpa pressure change per 27ft"..

Not sure how this works out at 1000 HPa.

Hello,

Have you considered the conversion between feet and metres?

Basic ATPL QFE. question
 

You should convert 200 meters to feet and then do the calculations.

Ok I am with you...

200 meters = 656 feet.

656/27 = 24.296 - Call it 24.

1025 - 24 = 1001 hPa QFE.

So approx 1000 hPa as stated in the handbook.

Cheers.

...........RTFQ

Not heard that before...

Google it!

You will a lot during study..

Read The :mad: Question.

Also, just as important is RTFA. I think you can now work that one out. :ok:

Here's how I did it:
1hPa = 27ft = 8m

200 : 8 = 25

1025hPa - 25 = 1000

V Speeds - Help
 

Hello everybody.

If anybody could try and help me with the answers for some "advanced" questions I have come across over the years it would be greatly appreciated

1. Given that:
VEF= Critical engine failure speed
VMCG= Ground minimum control speed
VMCA= Air minimum control speed
VMU= Minimum unstick speed
V1= Take-off decision speed
VR= Rotation speed
V2 min.= Minimum take-off safety speed
The correct formula is:

a) VMCG<=VEF < V1
b) 1.05 VMCA<= VEF<= V1
c) 1.05 VMCG< VEF<= VR
d) V2min<= VEF<= VMU

2. The induced drag of an aeroplane at constant gross weight and altitude is highest at

a) VSO (stalling speed in landing configuration)
b) VS1 (stalling speed in clean configuration)
c) VMO (maximum operating limit speed)
d) VA (design manoeuvring speed)

3. The stalling speed or the minimum steady flight speed at which the aeroplane is controllable in landing configuration is abbreviated as

a) VSO.
b) VS1.
c) VS.
d) VMC.

4. Which of the following speeds can be limited by the ’maximum tyre speed’?

a) Lift-off groundspeed.
b) Lift-off IAS.
c) Lift-off TAS.
d) Lift-off EAS.

5. During the flight preparation a pilot makes a mistake by selecting a V1 greater than that required. Which problem will occur when the engine fails at a speed immediately above the correct value of V1?

a) The stop distance required will exceed the stop distance available.
b) The one engine out take-off distance required may exceed the take-off distance available.
c) V2 may be too high so that climb performance decreases.
d) It may lead to over-rotation.

6. V1 has to be

a) equal to or higher than VMCG.
b) equal to or higher than VMCA.
c) higher than than VR.
d) equal to or higher than V2.

7. The take-off safety speed V2min for turbo-propeller powered aeroplanes with more than three engines may not be less than:


8. The speed V2 of a jet aeroplane must be greater than:

a) 1.2Vs.
b) 1.2VMCG.
c) 1.05VLOF.
d) 1.3V1.

9. As long as an aeroplane is in a positive climb

a) VX is always below VY.
b) VX is sometimes below and sometimes above VY depending on altitude.
c) VX is always above VY.
d) VY is always above VMO.


10. Higher gross mass at the same altitude decreases the gradient and the rate of climb whereas

a) VY and VX are increased.
b) VX is increased and VY is decreased.
c) VY and VX are not affected by a higher gross mass.
d) VY and VX are decreased.

11. Given a jet aircraft. Which order of increasing speeds in the performance diagram is correct?

a) Vs, Vx, Maximum range speed
b) Maximum endurance speed, Long range speed, Maximum range speed
c) Vs, Maximum range speed, Vx
d) Maximum endurance speed, Maximum range speed, Vx

12. Approaching in turbulent wind conditions requires a change in the landing reference speed (VREF):

a) Increasing VREF
b) Lowering VREF
c) Keeping same VREF because wind has no influence on IAS.
d) Increasing VREF and making a steeper glide path to avoid the use of spoilers.


13. What margin above the stall speed is provided by the landing reference speed VREF?

a) 1,30 VSO
b) 1,05 VSO
c) 1,10 VSO
d) VMCA x 1,2


14. Which of the following answers is true?

a) V1 is lower or equal to VR
b) V1 is higher VLOF
c) V1 is higher VR
d) V1 is lower VMCG


15. Which statement is correct?

a) VR must not be less than 1.05 VMCA and not less than V1.
b) VR must not be less than VMCA and not less than 1.05 V1.
c) VR must not be less than 1.1 VMCA and not less than V1.
d) VR must not be less than 1.05 VMCA and not less than 1.1 V1

16. Which of the following represents the minimum for V1?

a) VMCG
b) VLOF
c) VMU
d) VR


17. Which of the following represents the maximum value for V1 assuming max tyre speed and max brake energy speed are not limiting?

a) VR
b) VMCA
c) V2
d) VREF


18. The correct formula is: (Remark: "<=" means "equal to or lower")

a) VMCG<=VEF < V1
b) 1.05 VMC<= VEF<= V1
c) 1.05 VMCG< VEF<= VR
d) V2min<= VEF<= VMU


19. Regarding take-off, the take-off decision speed V1:

a) is the airspeed on the ground at which the pilot is assumed to have made a decision to continue or discontinue the take-off.
b) is always equal to VEF (Engine Failure speed).
c) is an airspeed at which the aeroplane is airborne but below 35 ft and the pilot is assumed to have made a decision to continue or discontinue the take-off .
d) is the airspeed of the aeroplane upon reaching 35 feet above the take-off surface.


20. Which of the following sequences of speed for a jet aeroplane is correct? (from low to high speeds)

a) Vs, maximum angle climb speed, maximum range speed.
b) Vs, maximum range speed, maximum angle climb speed
c) Maximum endurance speed, maximum range speed, maximum angle of climb speed.
d) Maximum endurance speed, long range speed, maximum range speed.


21. In accordance to CS 25 which of the following listed speeds are used for determination of V2min:

a) VSR, VMCA
b) VMCG, V2
c) VLOF, VMCA
d) V1, VR.

22. In certain conditions V2 can be limited by VCMA

a) Low take-off mass, large flap extension, low field elevation.
b) Low take-off mass, small flap extension, low field elevation.
c) High take-off mass, large flap extension, low field elevation.
d) High take-off mass, small flap extension, high field elevation.


23. The relationship of the reference landing speed (VREF) to the reference stalling speed in the landing configuration (VSRO) is that VREF may not be below:

a) 1.23VSRO
b) VSRO
c) 1.1 VSRO
d) 1.32 VSRO


24. V2 has to be equal to or higher than

a) 1.1 VMCA
b) 1.15 VMCG
c) 1.1 VSO
d) 1.15 VR.


25. The value of V1 has to be equal to or higher than:

a) VMCG
b) VMC
c) VR
d) V2



26. In accordance with JAR 25 the take-off safety speed V2min for turbo-propeller powered aeroplanes with more than three engines may not be less than:

a) 1.08 VSR
b) 1.2 VSR
c) 1.13 VSR
d) VSR

May I ask whether you are doing a formal ATPL course, Jay? it would take quite a bit to explain the answers to all 25 questions but this is pretty standard stuff, it should be in your course material.

Stall question from the Belgium exam
 

Hope this is the right section to post this.

This is a question from the Belgium exam

A possible cause for the auto recovery of an airplane after a stall is
a. The angle of incidence (AOI) of the wing is larger than the AOI of the stabilizer
b. The wing surface is bigger than the wing surface of the stabilizer.
c. The AOI of the wing is smaller than the AOI of the stabilizer.
d. The angle of attack (AOA) of the stabilizer is bigger than the AOA of the wing.

1. is the right answer but why? Is the question anyhow correct and can you generalise this question for every plane?

Hi Peter,

If the AOI of the main wing is greater than the AOI of the stabiliser, the wing will reach it's critical angle of attack and stall first as the stabiliser's angle of attack will be lower due to a lower AOI presented to the airflow.

As the wing stalls first, the aircraft will usually pitch nose down as the stabiliser is still producing lift for the reason given above. As the aircraft pitches down, the wing angle of attack is reduced and it unstalls.

That's my take anyway! :)

ATPL Exam workbooks
 

With reference to CAA ATPL exams - CAP's were withdrawn earlier in the year and replaced with workbooks for the exam. Does anyone have any info on the content of the workbooks provided?

i.e. Mass & Balance, does it include conversion factors, I take it the definitions of masses has been removed, What about the level of info for SEP. MEP and MRJT?

Which CAA ATPL exam are you referring to?