RMI Question
Joined: Aug 2003
Posts: 240
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From: Scotland
Pointless Nonsense
I hate these style of questions - I hope this is not a real exam question for a 21st century pilot licence, although I fear it may be. 
1. The Q code was deprecated when VHF voice communications replaced morse code, and should not generally be used, ruling out answers A and B.
2. Answer C is a trick answer, since radials always run "from" the station, so the radial is on the tail, but nobody cares about that distinction in the real world either.
The great thing about the RMI is that interpretation of it is completely natural - the pointer points at the station. That's all you need to know.
Rant Over. Thanks for listening.
(In the 1950's, the answer they were probably looking for was A).
1. The Q code was deprecated when VHF voice communications replaced morse code, and should not generally be used, ruling out answers A and B.
2. Answer C is a trick answer, since radials always run "from" the station, so the radial is on the tail, but nobody cares about that distinction in the real world either.
The great thing about the RMI is that interpretation of it is completely natural - the pointer points at the station. That's all you need to know.
Rant Over. Thanks for listening.
(In the 1950's, the answer they were probably looking for was A).
Joined: Mar 2005
Posts: 1,338
Likes: 1
From: Uh... Where was I?
What is "radial inbound", here?
The pointer of the needle points at the reciprocal of the radial the airplane is . If that is what they mean by radial inbound, that's the one.
It is not necesarily QDM, since VOR radials use the variation of the station, instead of the variation at the airplane's position, so there can be a slight difference.
also, in case of failure of the rotating card, the tail of the needle will keep pointing at the correct radial, so you don't have relative bearing indication.
The pointer of the needle points at the reciprocal of the radial the airplane is . If that is what they mean by radial inbound, that's the one.
It is not necesarily QDM, since VOR radials use the variation of the station, instead of the variation at the airplane's position, so there can be a slight difference.
also, in case of failure of the rotating card, the tail of the needle will keep pointing at the correct radial, so you don't have relative bearing indication.
Joined: Sep 2007
Posts: 128
Likes: 0
From: UK
Clue:
There are no radials associated with an NDB.
RMIs are referenced to LOCAL magnetic North.
I think that answers the question, although given the imminent demise of NDBs I concur that it isn't so relevant to the real world of aviation.
Although it does demonstrate a grasp of the essentials, a bit like the DC carbon-pile VR, so does have some relevance to the world.
There are no radials associated with an NDB.
RMIs are referenced to LOCAL magnetic North.
I think that answers the question, although given the imminent demise of NDBs I concur that it isn't so relevant to the real world of aviation.
Although it does demonstrate a grasp of the essentials, a bit like the DC carbon-pile VR, so does have some relevance to the world.
Joined: Jun 2011
Posts: 4
Likes: 0
From: Egypt
RMI
If your flying inbound/outbound from a VOR staton using the RMI instrument, and the controller asks you "what is your current radial" In both cases you will look at the tail of the needle.
The head always points to the station relative to your position, which is the magnetic bearing to the station also known as QDM.
This is why i think it is A
The head always points to the station relative to your position, which is the magnetic bearing to the station also known as QDM.
This is why i think it is A
Joined: Aug 1998
Aviation Qualifications: ATPL
Posts: 6,623
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From: Ex-pat Aussie in the UK
On the RMI, the pointer arrow head (reference to VOR) represents
a- QDM
b- QDR
c- Radial inbound
A - QDM, the Magnetic Direction of the station, measured at the aircraft (i.e. with the magnetic variation at the aircraft.) This is not the correct answer, as the RMI needle presentation is set to "VOR". A VOR produces two phased radio signals, with the phase difference defining the magnetic radial at the VOR. This is the difference between using a needle presentation for a VOR, and using an ADF needle (which is the point of asking this particular question).
B - QDR - the Magnetic bearing from a station. The pointer arrow TAIL would read the bearing from the station. The arrow head is displaying:
C- the radial (as determined by the VOR's signal phase difference, referenced to magnetic north at the VOR station), inbound as you are using the head of the needle. Not good terminology, but the closest correct answer.
a- QDM
b- QDR
c- Radial inbound
A - QDM, the Magnetic Direction of the station, measured at the aircraft (i.e. with the magnetic variation at the aircraft.) This is not the correct answer, as the RMI needle presentation is set to "VOR". A VOR produces two phased radio signals, with the phase difference defining the magnetic radial at the VOR. This is the difference between using a needle presentation for a VOR, and using an ADF needle (which is the point of asking this particular question).
B - QDR - the Magnetic bearing from a station. The pointer arrow TAIL would read the bearing from the station. The arrow head is displaying:
C- the radial (as determined by the VOR's signal phase difference, referenced to magnetic north at the VOR station), inbound as you are using the head of the needle. Not good terminology, but the closest correct answer.
Joined: Aug 1998
Aviation Qualifications: ATPL
Posts: 6,623
Likes: 847
From: Ex-pat Aussie in the UK
The QDF, he asked for the:
... not the "runway QDM", or the QFU?
ICAO Q codes
QDF (what is the / here is the ... ) difference in actual height of pressure level to height of same pressure level in ICAO standard atmosphere (the 'D' - factor).
... not the "runway QDM", or the QFU?
ICAO Q codes
