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Questions on Obstacle Clearance

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PostPosted: Tue Apr 17, 2012 3:49 am    Post subject: Questions on Obstacle Clearance Reply with quote

Arrow If for aeroplane in Performance Class B the intended take-off flight path requires track changes of more than 15 deg, with the pilot unable to maintain visual navigation accuracy , the clearance of obstacles within "900m" of track need be considered.

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Arrow Following a take off limited by the 50 ft screen height, a light twin climbs on a gradient of 5%. It will clear a 160 m obstacle in relation to the runway (horizontally), situated at 5000m from the 50 ft point with an obstacle clearance margin of:

a) 105 m <- Correct
b) 90 m

The important point in this simple problem is to cater for the 50 ft point. If you dont you'll end up with the wrong answer of 90m which is present in the options.

The obstacle is at 5000m or 16400 feet from the 50 ft point and is 160m or 525 ft high.

5% gradient means the aircraft is climbing 5 feet for 100 feet horizontal distance.

Therefore for 16400 ft horizontal distance it will be at a height of:

5/100 x 16400 = 820

Since the starting point was at 50 ft above the ground the correct aircraft height will be 820+50 = 870 feet

The difference between aircraft at 870 feet and obstacle at 525 feet is 345 ft or 105m.

Arrow Regarding the obstacle limited take off mass, which of the following statements is correct?

a) A take off in the direction of an obstacle is also permitted in tail wind condition <-- Correct
b) Wind speed plays no role when calculating this particular mass
b) The obstacle limited mass can never be lower than the climb limited take off mass
c) The maximum bank angle which can be used is 10 deg

Arrow An operator shall ensure that the net take off flight path clears all obstacles. The half width of the obstacle corridor at the distance D from the end of the TODA is at least:

a) 90m + 0.125D <-- Correct
b) -90m + 1.125D
c) 90m + D/0 125
d) 0.125 D

Arrow Which speed provides maximum obstacle clearance during climb?

a) The speed for which the ratio between rate of climb and forward speed is maximum <-- Correct
b) V2
c) V2 + 10 kt
d) The speed for maximum rate of climb
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