DR Navigation
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DR Navigation
Hello,
The AIP states that a VFR flight may use the IFR techniques (Navaids, GPS etc) if the pilot is rated to use them, for navigation, as well as the map reading techniques. However there is no mention of use of dead reckoning here which is what I am currently using during my night VFR rating. What are the position fixing requirements for this? Is this a permitted navigation technique at night when I have no reference to the ground?
The AIP states that a VFR flight may use the IFR techniques (Navaids, GPS etc) if the pilot is rated to use them, for navigation, as well as the map reading techniques. However there is no mention of use of dead reckoning here which is what I am currently using during my night VFR rating. What are the position fixing requirements for this? Is this a permitted navigation technique at night when I have no reference to the ground?
For night VFR you can either navigate visually or by navaids you're rated on.
If you choose navaids and have the equipment / training to use them(which may include an approved GPS) you need positive fixes as per the AIP IFR requirements for navigation.
Otherwise you're back to the VFR position fixing requirements, ie a positive fix every 30 minutes by identifying something on the ground. You said you have no reference to the ground, but that's not correct - if the weather's clear, as it should be if you're punching off on a NVFR nav, you will be able to use DR techniques combined with identification of ground lights to get positive fixes.
If it's a DR nav to the back of nowhere on a really dark night without the possibility of identifying townships or whatever on the way, you should probably rethink your route!
On a nice moonlit night you'll be able to see clouds, horizon, ground features etc and have that nice feeling of knowing where you are, but of course that's not going to happen all the time.
NVFR will always be fraught on a super black night because you won't know you're about to go into cloud until you're in it, but that's where a (hopefully) good forecast and go / no go decision come into it.
It comes back to the whole idea of NVFR - as I understand it, it exists in the regs to allow you to have a bit more flex regarding getting somewhere after last light, or launching before first light. In reality though, there's no restrictions on moon state or anything like that, so nothing to preclude you launching off into complete darkness with all the issues that come with that (illusions, possibility of CFIT, possibility of inadvertent IMC, etc etc).
If you choose navaids and have the equipment / training to use them(which may include an approved GPS) you need positive fixes as per the AIP IFR requirements for navigation.
Otherwise you're back to the VFR position fixing requirements, ie a positive fix every 30 minutes by identifying something on the ground. You said you have no reference to the ground, but that's not correct - if the weather's clear, as it should be if you're punching off on a NVFR nav, you will be able to use DR techniques combined with identification of ground lights to get positive fixes.
If it's a DR nav to the back of nowhere on a really dark night without the possibility of identifying townships or whatever on the way, you should probably rethink your route!
On a nice moonlit night you'll be able to see clouds, horizon, ground features etc and have that nice feeling of knowing where you are, but of course that's not going to happen all the time.
NVFR will always be fraught on a super black night because you won't know you're about to go into cloud until you're in it, but that's where a (hopefully) good forecast and go / no go decision come into it.
It comes back to the whole idea of NVFR - as I understand it, it exists in the regs to allow you to have a bit more flex regarding getting somewhere after last light, or launching before first light. In reality though, there's no restrictions on moon state or anything like that, so nothing to preclude you launching off into complete darkness with all the issues that come with that (illusions, possibility of CFIT, possibility of inadvertent IMC, etc etc).
Ok, now it gets interesting. My dictionary lists dead reckoning, but acknowledges DED reckoning. There seem to be naval references to Dead Reckoning dating to the 1600's, although there is no explanation of the source for Dead. It acknowledges that DED reckoning has stronger rationale.
I am sure I have read something by someone serious saying it should be DED reckoning. This may have been something like one of Max Conrad's books, or something of that stature.
So, I now have no idea. So for the moment you say potato..........
I am sure I have read something by someone serious saying it should be DED reckoning. This may have been something like one of Max Conrad's books, or something of that stature.
So, I now have no idea. So for the moment you say potato..........
Nope, it's 'deduced' or 'deductive' reckoning. 'Dead' reckoning would be relevant to doing the accounts in a funeral parlour.
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I think the origins of "D" in D.R. are lost in the mists of time. I've seen it written & argued both ways, with good reasons given for each. It certainly does pre-date aviation though.
Crunch...!!
Iceberg !! Dead (meaning straight) ahead..cried the Captain.
By my Ded.reckoning, we shouldnt be here !..cried the Navigator.
Alas, precise ship's position doubtful.
Iceberg ?, well it was just in the way.
And the rest is history.
By my Ded.reckoning, we shouldnt be here !..cried the Navigator.
Alas, precise ship's position doubtful.
Iceberg ?, well it was just in the way.
And the rest is history.
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JSeward,
the requirements for this stuff should be spelled out to you during your training as part of gaining the rating.
If not, then I would be highly questionable of the training you are recieving...the fact you asked here highlighted a flag for me.
An N-VFR rating is easy to obtain, difficult to maintain, let alone master.I often find I have an instructor along for the ride due currency.
NVFR is possibly harder than IFR, definatley one of the more challenging ratings that MUST be respected!
Enjoy
Jas
the requirements for this stuff should be spelled out to you during your training as part of gaining the rating.
If not, then I would be highly questionable of the training you are recieving...the fact you asked here highlighted a flag for me.
An N-VFR rating is easy to obtain, difficult to maintain, let alone master.I often find I have an instructor along for the ride due currency.
NVFR is possibly harder than IFR, definatley one of the more challenging ratings that MUST be respected!
Enjoy
Jas
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Thanks jas,
I have done only 1 short Nav so far which was less than 30 minutes to the destination so I suppose DR navigation was suitable then, and my instructor was also reading the Garmin 430 so I suppose if he is doing that then on our Navs we are legal. I was just wondering if using DR alone was a suitable method but it appears not to be.
Or maybe it is if you have a "full time flight navigator"?
I have done only 1 short Nav so far which was less than 30 minutes to the destination so I suppose DR navigation was suitable then, and my instructor was also reading the Garmin 430 so I suppose if he is doing that then on our Navs we are legal. I was just wondering if using DR alone was a suitable method but it appears not to be.
Or maybe it is if you have a "full time flight navigator"?
A sensible answer...
NVFR ranges from being as easy as day VFR to harder than IFR. NVFR gets harder than IFR because IFR is pretty much a binary state. You see out or you don't. NVMC can be less clear with some optical illusion effects thrown in for good measure. IFR trains you to fly the instruments at the exclusion of all else, NVFR is a shandy.
A NVFR rating teaches many good things, some instrument skills and a better understanding of NAVAIDS. When I used the NVFR rating it was almost exclusively for coming home 30 min - 1 hour after dark. Flying back into a familiar city area that is well lit falls (in my opinion) at the low risk end. But if you are going to use it a lot or for flights predominantly at night, you should get an instrument rating.
My view would be that you focus in DR during training so you show yourself how accurate you can be, but when you fly it for real, have every aid possible working & helping you. I recall that during my training (pre GPS) I successfully navigated to a one horse town whose only light was a single street light and about 2 houses. Its good to know you can do this.
NVFR is that, VFR at night. The minimum instruments are less than you might think. Your instructor was using the 430 because they all cheat. Like day VFR, most of your night navigation will be by reference to the GPS. You should be fluent with its operation.
A lot of emphasis is placed on engine failures in training, but the truth is you are many times more likely to have an alternator, vacuum pump or landing light failure. If you have an alternator failure, you'll shut everything down and fly with only the 430 & txp working, there should be enough battery to get you to where you want to go.
I won't fly at night in a single anymore, although I used to a lot. I'd be very cautious about flying NVFR or IFR in a single without an auxillary vacuum pump or back up electric AH
NVFR ranges from being as easy as day VFR to harder than IFR. NVFR gets harder than IFR because IFR is pretty much a binary state. You see out or you don't. NVMC can be less clear with some optical illusion effects thrown in for good measure. IFR trains you to fly the instruments at the exclusion of all else, NVFR is a shandy.
A NVFR rating teaches many good things, some instrument skills and a better understanding of NAVAIDS. When I used the NVFR rating it was almost exclusively for coming home 30 min - 1 hour after dark. Flying back into a familiar city area that is well lit falls (in my opinion) at the low risk end. But if you are going to use it a lot or for flights predominantly at night, you should get an instrument rating.
My view would be that you focus in DR during training so you show yourself how accurate you can be, but when you fly it for real, have every aid possible working & helping you. I recall that during my training (pre GPS) I successfully navigated to a one horse town whose only light was a single street light and about 2 houses. Its good to know you can do this.
NVFR is that, VFR at night. The minimum instruments are less than you might think. Your instructor was using the 430 because they all cheat. Like day VFR, most of your night navigation will be by reference to the GPS. You should be fluent with its operation.
A lot of emphasis is placed on engine failures in training, but the truth is you are many times more likely to have an alternator, vacuum pump or landing light failure. If you have an alternator failure, you'll shut everything down and fly with only the 430 & txp working, there should be enough battery to get you to where you want to go.
I won't fly at night in a single anymore, although I used to a lot. I'd be very cautious about flying NVFR or IFR in a single without an auxillary vacuum pump or back up electric AH
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"Dead" or "Ded"
If you've started night navs and you don't know the answer to that question, I'd be looking for a new instructor / school. If you go delving into the AIP you'll find the answer - in short your primary means of navigating is always DR, supported by various aids. eg map reading, ground based nav aids and GPS. From memory Night VFR requires the destination to be equipped with a serviceable navaid you're trained on and the aircraft equipped with or if it hasn't then you need an alternate so equipped within a specified distance or flight time.... I think it says something like that? Good luck!
AIP GEN 3.3
4.10 For Aircraft Flown at Night Under the VFR: the area to be considered must be:
a. the area specified in para 4.8 or 4.9 for aircraft navigated by means of a radio navigation system; or
b. within a radius of 10NM from any point along the aircraft’s nominal track.
However, the pilot of an aircraft who has positively determined by visual fix that a critical obstruction has been passed may nevertheless descend immediately to a lower altitude, provided that the required obstacle clearance above significant obstructions ahead of the aircraft is maintained.
4.10 For Aircraft Flown at Night Under the VFR: the area to be considered must be:
a. the area specified in para 4.8 or 4.9 for aircraft navigated by means of a radio navigation system; or
b. within a radius of 10NM from any point along the aircraft’s nominal track.
However, the pilot of an aircraft who has positively determined by visual fix that a critical obstruction has been passed may nevertheless descend immediately to a lower altitude, provided that the required obstacle clearance above significant obstructions ahead of the aircraft is maintained.
Ps, for other position fixes as per ENR 1.1 Paras 19.4 & 19.5, the AIP do not specify IFR only.
Last edited by MakeItHappenCaptain; 22nd May 2013 at 11:21.
The alternate requirement unless there's a ground based NDB or VOR at destination has now been changed so you don't need one if you have an approved GNSS receiver and are trained to use it.
MakeItHappen..., are you implying that NVFR requires a visual fix to descend once a lower LSALT applies to a route segment? I read your comment that way the first time but now I'm not sure. Anyway, if you are, that's not quite correct. You may use IFR radio navigation techniques to descend to a new altitude without ever sighting the ground. You could choose to use IFR LSALTs directly from a chart, or calculate x-bearings, or use a bearing/DME fix etc. However, if you wish to descend *immediately* you pass a limiting obstacle, then the fix must be visual.
The difference is that radio nav position fixes must include a buffer. A visual fix does not.
The difference is that radio nav position fixes must include a buffer. A visual fix does not.
Last edited by Tinstaafl; 23rd May 2013 at 00:46.