performance question...
 

lads i could do with some help...

An aircraft has a gradient of climb of 7% after take off.There is an obstacle having a height of 320ft at a distance to 5400ft from the distance to the 50ft point.The clearence of the obstacle would be..?

thanks for your help......

Using pythagoros (sp?):-

5400ft is the adjacent

7% = 0.07 = Tan(x) (approx and good enough)

Tan(x) = Opposite / Adjacent

Opposite = 0.07 * 5400 = 378

378' - 320' = 58'

The question is worded ambiguously and strangely (must be a real JAA one then!), but I assume that the 320' is AGL so add on the 50' screen height to get the total clearance of 108'

Hi guys,

Im sitting the JAA perf on the 6th Sept, my 2nd attempt having marginally scraped through 2months ago.
Wondering if at this late stage any of you guys have new feedback questions, as mine are from late june...
Be really much appreciated,
look forward to your replies.

D.

The question is asking for the height the a/c will clear the obstacle.

The known facts:

Obstacle 5400' from the screen height position.
Obstacle height = 320'
Climb gradient 7% or 0.07 after take-off. The take off ends at the 50' point from the wording of this question so this means the climb gradient commences 50' above the ground.

Because the gradient is measured from 50' above ground level then you need to measure the top of the obstacle from the same point ie 50' above the surface. This means the obstacles 'height' for gradient purposes is

320'-50' = 270'.

To find a/c clearance you need to find how high the a/c will have climbed above the 50' point when it gets 5400' along track.

Gradient = 'rise over run'

The problem supplies the climb gradient & the 'run' distance so transposing the formula to isolate the 'rise' part gives:

(Gradient x run) = rise

Once you have that 'rise' figure ie climb height above the 50' level, subtract the obstacle's height above this 50' level (270') from it to find the clearance.

i like high wing drifters way of thinking...where would be without that good old greek guy Piethagoras(sp?:ok: ) i wonder if he was a fatty?


cheers r

If you need any kind of Feedback for the ATPL, try to look at

www.aviationpilots.com

They got alot of feedback from the JAA ATPL under their Examhelp.
And they are saying that they are opdating all the time.
Might be worth looking at.;)

Cheers for the link 'aviationpilots.com' TKPILOT, not sure if its my computer or the web site itself but couldnt seem to open the link for the JAA Perf Exam help (just got a blank screen)

Any more suggestions help!!
:{

D.

Download or reinstall Adobe Acrobat.

You may like to try these practice questions. I'm afraid the cut + paste job has messed up the spacing a little, but they should still make sense. I suspect that I have made a mistake in one, but I am sure somebody will point it out to me.

It is always worth doing lots of practice prior to the exams. The CAA have been doing work to clone many of their calculation questions to trip up students who simply learn the answers to past questions.



1. What would be the obstacle clearance in a 5% gradient take-of climb given the following data?

Obstacle height 160m above the airfield elevation.
Obstacle 5000m from the screen.
Screen height 50 ft.

a. 90m.
b. 105m.
c. 200m.
d. 250m.


Answer 1. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((5/100 x 5000m) – 160m = 105 m (option b).


2. What would be the obstacle clearance in a 7% gradient take-of climb given the following data?

Obstacle height 260m above the airfield elevation.
Obstacle 5000m from the screen.
Screen height 50 ft.

a. 90m.
b. 105m.
c. 200m.
d. 250m.


Answer 2. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((7/100 x 5000m) – 260m = 105 m (option b).


3. What would be the obstacle clearance in a 5% gradient take-of climb given the following data?

Obstacle height 360m above the airfield elevation.
Obstacle 4700m from the screen.
Screen height 50 ft.

a. 90m.
b. 110m.
c. 200m.
d. The aircraft will not clear the obstacle.


Answer 3. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((5/100 x 4700m) – 360m = -110 m

This means that the aircraft will hit the obstacle at 110 m below its top. So the aircraft will not clear the obstacle (option d).


4. What would be the obstacle clearance in a 4.5% gradient take-of climb given the following data?

Obstacle height 300m above the airfield elevation.
Obstacle 6000m from the screen.
Screen height 50 ft.

a. 190m.
b. 15m.
c. 200m.
d. The aircraft will not clear the obstacle.


Answer 4. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((4.5/100 x 6000m) – 300m = -15 m

This means that the aircraft will hit the obstacle at 150 m below its top. So the
The aircraft will not clear the obstacle (option d).


5. What would be the obstacle clearance in a 6.7% gradient take-of climb given the following data?

Obstacle height 250m above the airfield elevation.
Obstacle 5600m from the screen.
Screen height 50 ft.

a. 190m.
b. 125m.
c. 140m.
d. The aircraft will not clear the obstacle.


Answer 5. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((6.7/100 x 5600m) – 250m = 140 m (option c).


6. What would be the obstacle clearance in a 3.5% gradient take-of climb given the following data?

Obstacle height 275m above the airfield elevation.
Obstacle 6900m from the screen.
Screen height 50 ft.

a. 95m.
b. 115m.
c. 275m.
d. The aircraft will not clear the obstacle.


Answer 6. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((3.5/100 x 6900m) – 275m = -18.5 m

This means that the aircraft will hit the obstacle at 18.5 m below its top. So the aircraft will not clear the obstacle (option d).


7. What would be the obstacle clearance in a 5% gradient take-of climb given the following data?

Obstacle height 160m above the airfield elevation.
Obstacle 4000m from the screen.
Screen height 50 ft.

a. 55m.
b. 105m.
c. 200m.
d. The aircraft will not clear the obstacle.

Answer 7. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((5/100 x 4000m) – 160m = 55 m (option a).


8. What would be the obstacle clearance in a 8.5% gradient take-of climb given the following data?

Obstacle height 160m above the airfield elevation.
Obstacle 4000m from the screen.
Screen height 50 ft.

a. 95m.
b. 105m.
c. 195m.
d. The aircraft will not clear the obstacle.

Answer 8. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((8.5/100 x 4000m) – 160m = 195 m (option c).


9. What would be the obstacle clearance in a 3.5% gradient take-of climb given the following data?

Obstacle height 360m above the airfield elevation.
Obstacle 6500m from the screen.
Screen height 50 ft.

a. 55m.
b. 117.5m.
c. 200m.
d. The aircraft will not clear the obstacle.

Answer 9. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((3.5/100 x 6500m) – 360m = -117.5 m

This means that the aircraft will hit the obstacle 117.5 m below its top. So the aircraft will not clear the obstacle (option d).


10. What would be the obstacle clearance in a 2.5% gradient take-of climb given the following data?

Obstacle height 60m above the airfield elevation.
Obstacle 5000m from the screen.
Screen height 50 ft.

a. 80m.
b. 65m.
c. 120m.
d. The aircraft will not clear the obstacle.

Answer 10. This type of problem can be solved using the standard equation:

Clearance = Screen height +((%/100) x ground distance) – obstacle height above field.

50 ft = 15 m so inserting this and the data provided in the question gives:

Clearance = 15m + ((2.5/100 x 5000m) – 60m = 80 m (option a).

The link works great on my Computer but yes try to download Adobe Acrobat Easy to find on google.com
www.aviationpilots.com are opdating theyr JAA ATPL questions and should be getting ALOT more Questions in.