ATPL theory questions
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Hi
Q.1. When switching on the weather radar, after start-up a single very bright line appears on the screen. This means that the:
scanner is not rotating
scanning of the cathode ray tube is faulty
Q.2. On switching on the AWR a single line appears on the display. This means that:
the CRT is not scanning
the antenna is not scanning
Whats the main difference between the two?
Q.1. When switching on the weather radar, after start-up a single very bright line appears on the screen. This means that the:
scanner is not rotating
scanning of the cathode ray tube is faulty
Q.2. On switching on the AWR a single line appears on the display. This means that:
the CRT is not scanning
the antenna is not scanning
Whats the main difference between the two?

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Long time since I did this but I THINK its 81000/50 = 1620 but can't remember
why!
why!
The 81000 is one million divided by 12.36, the latter being the "radar mile"

Q.1. When switching on the weather radar, after start-up a single very bright line appears on the screen. This means that the:
scanner is not rotating
scanning of the cathode ray tube is faulty
Q.2. On switching on the AWR a single line appears on the display. This means that:
the CRT is not scanning
the antenna is not scanning
Whats the main difference between the two?
scanner is not rotating
scanning of the cathode ray tube is faulty
Q.2. On switching on the AWR a single line appears on the display. This means that:
the CRT is not scanning
the antenna is not scanning
Whats the main difference between the two?
For question 2, if the CRT is working correctly but the antenna is not scanning, then only the radar returns from the area in line with the scanner would be displayed. Whether or not these would produce a very bright line would depend upon what returns were being received from that area.
Last edited by keith williams; 21st Jan 2013 at 22:16.
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Battery life
Hey,
I recently heard a few questions asked at some interviews but cant find the answer anywhere.
The question was, by law how long must a battery last if power is lost. I have a feeling its 30 mins but I cant be sure. I have checked EU ops and cant find the answer anywhere. Anyone know what it is for a fact?
I recently heard a few questions asked at some interviews but cant find the answer anywhere.
The question was, by law how long must a battery last if power is lost. I have a feeling its 30 mins but I cant be sure. I have checked EU ops and cant find the answer anywhere. Anyone know what it is for a fact?
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Ground school for CPL (H)
Hello Everyone.
I am looking for regular or part time ground school for CPL(H) Exam. Is there any in the UK and how much it cost?
Any suggestion is much appreciated.
Cheers
I am looking for regular or part time ground school for CPL(H) Exam. Is there any in the UK and how much it cost?
Any suggestion is much appreciated.
Cheers
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How does one do this one:
If a radar pulse contains 300 cycles of RF energy at a frequency of 600 MHz, the physical length of the pulse is:
1550 metres
150 metres
1.5 metres
0.15 metres
thanks
If a radar pulse contains 300 cycles of RF energy at a frequency of 600 MHz, the physical length of the pulse is:
1550 metres
150 metres
1.5 metres
0.15 metres
thanks
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"Q.1. When switching on the weather radar, after start-up a single very bright line appears on the screen. This means that the:
scanner is not rotating
scanning of the cathode ray tube is faulty"
Interesting - as one who used to service monitors my first port of call would be the power supply
Deben - check out the big ad on the right
scanner is not rotating
scanning of the cathode ray tube is faulty"
Interesting - as one who used to service monitors my first port of call would be the power supply

Deben - check out the big ad on the right
If a radar pulse contains 300 cycles of RF energy at a frequency of 600 MHz, the physical length of the pulse is:
1550 metres
150 metres
1.5 metres
0.15 metres
1550 metres
150 metres
1.5 metres
0.15 metres
c = 300 000 000 m/sec. f = 600 MHz = 600 000 000 cycles/sec
Wavelength = 300 000 000 / 600 000 000 = 0.5 metres
Pulse length =cycles x wavelength
Pulse length = 300 cycels x 0.5 m/cycle = 150 metres
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Thanks Keith
I was getting uptil 0.5 meters but could'nt figure out that Pulse length = cycles x wavelength
Can you please explain this one too:
What is the PRF given 50 micro second pulse width and a range of 30 nm:
1620 pps
810 pps
3240 pps
3086 pps
Thanks
I was getting uptil 0.5 meters but could'nt figure out that Pulse length = cycles x wavelength

Can you please explain this one too:
What is the PRF given 50 micro second pulse width and a range of 30 nm:
1620 pps
810 pps
3240 pps
3086 pps
Thanks
Last edited by Haroon; 26th Jan 2013 at 11:34.
To produce unambiguous range information the radar system must remain silent between pulses for sufficient time for the pulse to travel out to the furthest target and return to the antenna.
The distance traveled by the signal = c x travel time
The travel time = the time between the transmission of successive pulses, which is equal to 1/PRF.
So distance traveled by the signal = c x 1/PRF which = c / PRF
But the signal must travel out to the furthest target and back to the antenna, so maximum range to the furthest target is half of the distance that the signal travels.
So maximum range = c / ( 2 x PRF)
Rearranging this equation gives
PRF = c / ( 2 x max range)
C is the speed of light, which is approximately 300 000 KM/sec or 162 000 NM / second.
For a range of 30 Nm the above equation gives
PRF = 162 000 NM/sec / ( 2 x 30 NM) = 2700 pulses per second
So your initial calculation was correct, but 2700 pps is not an option in this question.
BUT EASA CQB 15 does contain the following similar question.
The maximum pulse repetition frequency (PRF) that can be used by a primary radar facility in order to detect targets unambiguously at a range of 50 NM is?
A 713 pps
B 610 pps
C 1620 pps
D 3240 pps
The correct answer to this question is option C 1620 pps
This can be calculated at follows
PRF = 162 000 NM/sec / ( 2 x 50 NM) = 1620 pulses per second
The 50 micro second pulse width quoted in your question does not affect the maximum range, but will determine the minimum range.
The distance traveled by the signal = c x travel time
The travel time = the time between the transmission of successive pulses, which is equal to 1/PRF.
So distance traveled by the signal = c x 1/PRF which = c / PRF
But the signal must travel out to the furthest target and back to the antenna, so maximum range to the furthest target is half of the distance that the signal travels.
So maximum range = c / ( 2 x PRF)
Rearranging this equation gives
PRF = c / ( 2 x max range)
C is the speed of light, which is approximately 300 000 KM/sec or 162 000 NM / second.
For a range of 30 Nm the above equation gives
PRF = 162 000 NM/sec / ( 2 x 30 NM) = 2700 pulses per second
So your initial calculation was correct, but 2700 pps is not an option in this question.
BUT EASA CQB 15 does contain the following similar question.
The maximum pulse repetition frequency (PRF) that can be used by a primary radar facility in order to detect targets unambiguously at a range of 50 NM is?
A 713 pps
B 610 pps
C 1620 pps
D 3240 pps
The correct answer to this question is option C 1620 pps
This can be calculated at follows
PRF = 162 000 NM/sec / ( 2 x 50 NM) = 1620 pulses per second
The 50 micro second pulse width quoted in your question does not affect the maximum range, but will determine the minimum range.
Last edited by keith williams; 26th Jan 2013 at 13:52.
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Thanks for the explanation Keith.
That's what I thought. However I got confused with the post:
Regards
That's what I thought. However I got confused with the post:
81000/50 = 1620
81000 is one million divided by 12.36, the latter being the "radar mile"
81000 is one million divided by 12.36, the latter being the "radar mile"
Last edited by Haroon; 26th Jan 2013 at 15:13.
I have not used the Radar Mile method before but doing a GOOGLE search revealed this.
If we use PRT = the Pulse Repetition Time
PRT = 1 000 000 micro seconds / PRF
Range = PRT / 12.36 from GOOGLE extract
PRT / Range x 12.36
For 39 NM range
30 NM x 12.36 = 370.8
PRF = 1000000 microseconds / PRT = 1000000 / 370.8 = 2696
Which is approximately 2700.
For 50 NM range
50 NM x 12.36 = 618
PRF = 1000000 microseconds / PRT = 1000000 / 618 = 1618
Which is approximately 1620
Radar timing is usually expressed in microseconds. To relate radar timing to distances traveled by radar energy, you should know that radiated energy from a radar set travels at approximately 984 feet per microsecond. With the knowledge that a nautical mile is approximately 6,080 feet, we can figure the approximate time required for radar energy to travel one nautical mile using the following calculation:
A pulse-type radar set transmits a short burst of electromagnetic energy. Target range is determined by measuring elapsed time while the pulse travels to and returns from the target. Because two-way travel is involved, a total time of 12.36 microseconds per nautical mile will elapse between the start of the pulse from the antenna and its return to the antenna from a target.
This 12.36 microsecond time interval is sometimes referred to as a RADAR MILE, RADAR NAUTICAL MILE, or NAUTICAL RADAR MILE.
1 Radar Kilometer = 2 · 1000 m = 6.66 µs (1)
3 · 108 m/s
1 Radar Mile = 2 · 1852 m = 12.35 µs (2)
3 · 108 m/s
The range in kilometers to an object can be found by measuring the elapsed time during a round trip of a radar pulse and dividing this quantity by 6.66.
The range in nautical miles to an object can be found by measuring the elapsed time during a round trip of a radar pulse and dividing this quantity by 12.36.
A pulse-type radar set transmits a short burst of electromagnetic energy. Target range is determined by measuring elapsed time while the pulse travels to and returns from the target. Because two-way travel is involved, a total time of 12.36 microseconds per nautical mile will elapse between the start of the pulse from the antenna and its return to the antenna from a target.
This 12.36 microsecond time interval is sometimes referred to as a RADAR MILE, RADAR NAUTICAL MILE, or NAUTICAL RADAR MILE.
1 Radar Kilometer = 2 · 1000 m = 6.66 µs (1)
3 · 108 m/s
1 Radar Mile = 2 · 1852 m = 12.35 µs (2)
3 · 108 m/s
The range in kilometers to an object can be found by measuring the elapsed time during a round trip of a radar pulse and dividing this quantity by 6.66.
The range in nautical miles to an object can be found by measuring the elapsed time during a round trip of a radar pulse and dividing this quantity by 12.36.
If we use PRT = the Pulse Repetition Time
PRT = 1 000 000 micro seconds / PRF
Range = PRT / 12.36 from GOOGLE extract
PRT / Range x 12.36
For 39 NM range
30 NM x 12.36 = 370.8
PRF = 1000000 microseconds / PRT = 1000000 / 370.8 = 2696
Which is approximately 2700.
For 50 NM range
50 NM x 12.36 = 618
PRF = 1000000 microseconds / PRT = 1000000 / 618 = 1618
Which is approximately 1620
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ATPL Met exam
Hi everyone,
I would just like some peoples thoughts on the ATPL Met subject.
I have the Oxford OAA CDs for Module 1 of the CATS course which are excellent and I'm going to be properly starting Met tomorrow. Generally, Met seems to be one of the harder subjects of the ATPL course and I'm just wondering how many weeks or even months people are taking to study for Met?
I have been studying 5 - 6 hours a day and would appreciate someone giving me an indication of just how big/complex the subject is and their experiences.
Thanks in advance
I would just like some peoples thoughts on the ATPL Met subject.
I have the Oxford OAA CDs for Module 1 of the CATS course which are excellent and I'm going to be properly starting Met tomorrow. Generally, Met seems to be one of the harder subjects of the ATPL course and I'm just wondering how many weeks or even months people are taking to study for Met?
I have been studying 5 - 6 hours a day and would appreciate someone giving me an indication of just how big/complex the subject is and their experiences.
Thanks in advance
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Can't really comment on amount of time to spend as I went integrated and completed the whole syllabus in 2 weeks
but what I will say is that it's (for me) probably the most interesting subject, try to enjoy learning it - you'll find it one of the most useful subject and most important to retain when you're flying.
Good luck!

Good luck!
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Hi
The range to a required waypoint presented by RNAV system is:
plan range or slant range depending on RNAV settings
plan range
slant range
neither plan range nor slant range
Isnt it always plan range that is presented?
thanks
The range to a required waypoint presented by RNAV system is:
plan range or slant range depending on RNAV settings
plan range
slant range
neither plan range nor slant range
Isnt it always plan range that is presented?
thanks