Think I learnt about flying today...
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Forgot to add...
I was under the impression that GPS was not allowed to be used as a primary navigation aid and was only there as a backup to correct flight planning and VFR chart navigation. Although I have to add that I also think, can't remember fully, that that is for IFR nav.
However, prudence says that if its fitted it would be useful to have it on and pre-programmed as a back-up! Especially as most units will 'hot-start' very quickly if switched on where they were switched off but can take up to 2 minutes if moved significantly from their last sattelite 'snapshot'.
Cheers
I was under the impression that GPS was not allowed to be used as a primary navigation aid and was only there as a backup to correct flight planning and VFR chart navigation. Although I have to add that I also think, can't remember fully, that that is for IFR nav.
However, prudence says that if its fitted it would be useful to have it on and pre-programmed as a back-up! Especially as most units will 'hot-start' very quickly if switched on where they were switched off but can take up to 2 minutes if moved significantly from their last sattelite 'snapshot'.
Cheers
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I was under the impression that GPS was not allowed to be used as a primary navigation aid and was only there as a backup to correct flight planning and VFR chart navigation. Although I have to add that I also think, can't remember fully, that that is for IFR nav
If you can find a reference for any of the above, a lot of people are going to learn a lot.
Fortunately it's all completely false; the product of internet pilot forums, UK aviation magazines printing any old rubbish, CAA publications which freely mix up personal opinion of some ex RAF retired navigator with law, sentiments from various people at CAA "safety" seminars, and PPL instructors who don't like students getting ahead of the syllabus.
If you can find a reference for any of the above, a lot of people are going to learn a lot.
Fortunately it's all completely false; the product of internet pilot forums, UK aviation magazines printing any old rubbish, CAA publications which freely mix up personal opinion of some ex RAF retired navigator with law, sentiments from various people at CAA "safety" seminars, and PPL instructors who don't like students getting ahead of the syllabus.
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I was under the impression that GPS was not allowed to be used as a primary navigation aid and was only there as a backup to correct flight planning and VFR chart navigation.
Having said that, what is primiary and secondary navigation is all very academic. In practice we then to use more than one method of navigation, and question them when they don't agree. Which one is primiary and which is secondary doesn't really come into it.
dp
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Why, if the pilot does not intend to use the GPS in the normal course of the flight, should it be switched on?
If they don't consider it an emergency aid, then no. Forget about it, and when the workload increases in an emergency situation, leave the gps in the flight back, and work with what's available to you.
If things calm down.....such as if you had entered IMC, and then emerged into VMC on top....then by all means get it out. But when the chips are down, your having an inadvertent IMC encounter....that's not the time to be trying to find it, and having to start setting it up.
dp
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I've only just chanced upon this thread and would like to add my tuppence-worth....
To the posters who think a downdraft can't force an aircraft to the ground: of course it can! It's exactly the same physics as windshear which still kills people. The moving air stream can change direction and speed extremely rapidly, whether due to an inversion, ground features etc. An aircraft has a certain mass, and therefore momentum, and therefore requires a certain amount of time to adjust its flight profile to match the new wind speed and direction it is operating within. Most people understand that windshear can be deadly if a rapid airspeed loss occurs near to the ground, since the aircraft may be unable to accelerate sufficiently to maintain flying speed. Why is it any different when an aircraft is descending rapidly towards the ground and is unable to accelerate rapidly enough in the vertical plane to avoid impact?
Another analagy might be when driving down the motorway, and there's a nice laminar airflow over your bonnet and windscreen. Light particles such as dust or smoke have so little mass and therefore can be easily lifted within the airstream over the car. Anything a bit heavier can't accelerate up so quickly, so insects mostly hit the screen instead of being flung over the car.
Which has caused me some work with a bucket and sponge these last few days......
To the posters who think a downdraft can't force an aircraft to the ground: of course it can! It's exactly the same physics as windshear which still kills people. The moving air stream can change direction and speed extremely rapidly, whether due to an inversion, ground features etc. An aircraft has a certain mass, and therefore momentum, and therefore requires a certain amount of time to adjust its flight profile to match the new wind speed and direction it is operating within. Most people understand that windshear can be deadly if a rapid airspeed loss occurs near to the ground, since the aircraft may be unable to accelerate sufficiently to maintain flying speed. Why is it any different when an aircraft is descending rapidly towards the ground and is unable to accelerate rapidly enough in the vertical plane to avoid impact?
Another analagy might be when driving down the motorway, and there's a nice laminar airflow over your bonnet and windscreen. Light particles such as dust or smoke have so little mass and therefore can be easily lifted within the airstream over the car. Anything a bit heavier can't accelerate up so quickly, so insects mostly hit the screen instead of being flung over the car.
Which has caused me some work with a bucket and sponge these last few days......
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Fair enough, things have moved on since I last flew in a light aircraft 
I seem to recall, also by re-reading my post, that I stated 'I was under the impression' hence putting forward that I wasn't 100% sure, so thanks for the venhement reply.
I do, however, have experience of GPS integrity warnings, RAIM (Receiver Autonomous Integrity Warning) outages and power failures.
The problem with GPS, and with every aid, is that it is just that, an aid to navigation. Albiet within RNAV IFR airspace it is essential, for VFR flying in VMC it is not. The total reliance upon a single piece of equipment for navigation is folly hence the CAA requirement to train without in order to instill the basics of clock, map, ground. This may seem archaic in the current technological climate but if it all goes wrong then at least the pilot can revert to the basics of map reading.
I disagree with those who see it as a piece of the devil kit destroying our pure aviation, seat of the pants capabilities but I do see a need to fly without it.
It is easier to fly with the basics of navigation under your belt and then revert to the assisted aids when needed, i.e. in times of emergency. Thus allowing the pilot to offload and gain situational awareness. There is also nothing wrong with student pilots getting ahead of the game and learning GPS theory and usage, just don't let it hinder the basic skills or, in the worst case, mask or overide them.
hope that clears my position up a little
I seem to recall, also by re-reading my post, that I stated 'I was under the impression' hence putting forward that I wasn't 100% sure, so thanks for the venhement reply.
I do, however, have experience of GPS integrity warnings, RAIM (Receiver Autonomous Integrity Warning) outages and power failures.
The problem with GPS, and with every aid, is that it is just that, an aid to navigation. Albiet within RNAV IFR airspace it is essential, for VFR flying in VMC it is not. The total reliance upon a single piece of equipment for navigation is folly hence the CAA requirement to train without in order to instill the basics of clock, map, ground. This may seem archaic in the current technological climate but if it all goes wrong then at least the pilot can revert to the basics of map reading.
I disagree with those who see it as a piece of the devil kit destroying our pure aviation, seat of the pants capabilities but I do see a need to fly without it.
It is easier to fly with the basics of navigation under your belt and then revert to the assisted aids when needed, i.e. in times of emergency. Thus allowing the pilot to offload and gain situational awareness. There is also nothing wrong with student pilots getting ahead of the game and learning GPS theory and usage, just don't let it hinder the basic skills or, in the worst case, mask or overide them.
hope that clears my position up a little
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These "GPS" debates always degenerate into the same arguments. I don't have a problem with any of this, but was suprised at some of the people who have jumped on me further back (who I happen to know are professional jet pilots, and they know what I do, and they should know better).
However, I don't think you quite meant to say
The problem with GPS, and with every aid, is that it is just that, an aid to navigation
If everything is no more than an aid to navigation, what do you actually navigate with then??
In your airliner you are totally dependent on an FMS with multiple INS inputs, with DME/DME corrections when you can get them. That's pretty good and anyway you would just ask for vectors if it all packed up. Or, if way out over the ocean, fly the current heading to the next WP, etc, but I doubt that has ever happened.
Flying VFR, you can be map reading with a compass and a stopwatch, but that is not 100% reliable either (far from it, as well all know!). Yet for some reason, map reading is some sacred ritual which can never go wrong, and everything else is just an "aid" to it.
However, I don't think you quite meant to say
The problem with GPS, and with every aid, is that it is just that, an aid to navigation
If everything is no more than an aid to navigation, what do you actually navigate with then??
In your airliner you are totally dependent on an FMS with multiple INS inputs, with DME/DME corrections when you can get them. That's pretty good and anyway you would just ask for vectors if it all packed up. Or, if way out over the ocean, fly the current heading to the next WP, etc, but I doubt that has ever happened.
Flying VFR, you can be map reading with a compass and a stopwatch, but that is not 100% reliable either (far from it, as well all know!). Yet for some reason, map reading is some sacred ritual which can never go wrong, and everything else is just an "aid" to it.
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Originally Posted by IO540
In your airliner you are totally dependent on an FMS with multiple INS inputs, with DME/DME corrections when you can get them. That's pretty good and anyway you would just ask for vectors if it all packed up. Or, if way out over the ocean, fly the current heading to the next WP, etc, but I doubt that has ever happened.
Hilarious,
Well done for finding the airbus nav fit. The FMGS is a good bit of kit that locks, freezes and is generally regarded as being over complicated. It also takes all inputs and outputs and promulgates them to the systems. The older systems don't use GPS as a primary system and therfore requires constant checks against radio nav aids. They are also reknowned for freezing, drop ontop an electrical failure and you have no ND or PFD and your back to an aeroplane.
If you can't see that flying an aircraft, VFR within VMC as many PPL pilots are required to do, without the reliance on GPS is important then what is? Up to this point the CAA has ensured that, at least within the check rides, the GPS is off, for good reason. Poor map reading needs to be identified and corrected. If you think that a PPL pilot should wander off on a nav leg without planning on a chart and following that then I despair, probably along with a large amount of people on these boards.
I think you will find that most, if not all professional pilots have all trained this way and have that fall back option. If not then lets type limit aircraft to GPS and non GPS fitted aircraft in the same way that the US seperates automatic and manual cars.
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Re Mountain wave etc.
Some corrections to the quotation that Mercenary Pilot showed:
The description is of a simple mountain wave system, as first identified by glider pilots years ago, with a simple airstream and mountain set up. Life in reality can be much more complicated.
I was in mountain wave last week with a windspeed at height of 17 knots. Some of us thought we detected some with only 10 knots.
Waves can be easily up to 45 degrees angled to the general wind direction, and some of my colleagues last week found it at approximately 90 degrees, i.e. up-and-down wind, not just across.
Interference patterns happen in wave. Herringbone cloud formations appear on satellite photos, just like interference in ripples on the surface of a flowing stream when going over more than one obstruction.
Hills and valleys channel winds into unpredictable local variations of wind direction and strength.
Some wave at low wind speeds has vertical components as high as the wind speed. Too complex to explain here, but in essence a streamline can be deflected vertically in a local area.
Vertical currents, up and down, can be encountered very close to the ground - certainly 1-200 feet and there have been cases of two windsocks on different parts of the airfield showing wildly different directions, even 180 degrees opposed. If caused by rotor, the wild, turbulent down draught can be very close to the ground - I have been towed through some.
Last week, while picking a field to land out in, I saw a wind pattern in a crop radiating outwards from a central spot - had to be a down burst reaching the ground and spreading out there. (Wind speed at the time was about 15 knots on the ground where I landed, 20 knots in the air.)
Chris N
=====================
The description is of a simple mountain wave system, as first identified by glider pilots years ago, with a simple airstream and mountain set up. Life in reality can be much more complicated.
I was in mountain wave last week with a windspeed at height of 17 knots. Some of us thought we detected some with only 10 knots.
Waves can be easily up to 45 degrees angled to the general wind direction, and some of my colleagues last week found it at approximately 90 degrees, i.e. up-and-down wind, not just across.
Interference patterns happen in wave. Herringbone cloud formations appear on satellite photos, just like interference in ripples on the surface of a flowing stream when going over more than one obstruction.
Hills and valleys channel winds into unpredictable local variations of wind direction and strength.
Some wave at low wind speeds has vertical components as high as the wind speed. Too complex to explain here, but in essence a streamline can be deflected vertically in a local area.
Vertical currents, up and down, can be encountered very close to the ground - certainly 1-200 feet and there have been cases of two windsocks on different parts of the airfield showing wildly different directions, even 180 degrees opposed. If caused by rotor, the wild, turbulent down draught can be very close to the ground - I have been towed through some.
Last week, while picking a field to land out in, I saw a wind pattern in a crop radiating outwards from a central spot - had to be a down burst reaching the ground and spreading out there. (Wind speed at the time was about 15 knots on the ground where I landed, 20 knots in the air.)
Chris N
=====================
