A ramble - Not really for pilots:-
Now I don’t want to get into the deep technical here; but I do want to raise some questions related to ‘how’ the search area was actually defined – from the navigation data provided and the apparent assumptions drawn from assumed data. Basic. potted stuff follows, I know; but, I keep reading articles where ‘confusing’ terminology is worked into a theory or notion and presented as ‘hard’ fact. Without accurate flight planning data and the actual weather data for any of the assumed direction of travel; from an accurate start point, tackling the end of journey point, as purely a navigational and operational exercise, becomes the stuff of nightmare. When pure ‘guess-work’ is melded with inaccurate terminology; well, you can see where I’m heading. For instance:-
Heading – much is made of the aircraft’s ‘heading’. It wearies me to keep reading about this item. A ‘heading’ is, simply put, what the compass reads. Lets say you want to head North; but which North, there are basically two reference choices – Magnetic or True – and corrections must be made, if you wish to arrive in Albuquerque not Mecca. But the ‘heading’ is the basis on which navigational outcomes are based.
Track – simply put; the ‘track’ defines the actual path the aircraft travels. Say you still want to go North but the air through which you are travelling is moving from West to East. If you simply make your heading ‘N’ (360˚) then you will be carried East of your desired ‘track’ at a rate commensurate with the speed of the wind,. So; if Albuquerque is 200 miles North of your starting point, you will, 200 miles later be a considerable distance to the East of there, if you don't adjust the heading .
Wind Correction Angle – to avoid this embarrassment, a prudent pilot has a look at the ‘winds aloft’ prediction for the desired track and then, by a ridiculously simple method adjusts the basic heading to allow for ‘drift’. This is, surprisingly, known as the wind correction angle. The vagaries of the actual wind against those forecast become a simple matter of weighing the ‘track-made-good’ against where the aircraft actually is and a further simple correction is made to regain the desired track.
Speed – is a truly moveable feast of potential confusion. Almost every element of flight affects it, from power to weight, from temperature to altitude, from turbulence to aircraft trim. One of the basic ‘must’ have navigational speeds is the rate at which the aircraft travels over the earths surface, to wit; the ground speed. Another essential is the ‘True Airspeed’ (TAS).
TAS is, stand alone, a strange beast. A simple method of coming to terms with it is the ‘ICE-T’ formula. I= Indicated (IAS is what’s on the dial) – C =Calibrated (IAS corrected for position installation error)– E= Equivalent (EAS is CAS corrected for compressibility); from which TAS which defined, i.e. the EAS corrected for temperature and pressure altitude.
Why is the fool rabbiting on about this? Well, it is important if theory is to meet reality; for example; once you have defined the true speed of your aircraft and corrected the speed over the ground for wind; once you venture up into the higher atmosphere it really, really matters that these assumptions are correct. Above 25, 000 feet (ish) things change, the rate at which the temperature changes for example; but one of the real changes is the wind speed range and the ‘jet stream’. Anywhere between 60 to 120 knots (nautical miles per hour) is almost routine. These may be thought of as ribbons or ‘corridors’ of very fast moving air.
Just pretend you are still heading North at lets say 480 knots TAS (48 every six minutes) and the Jetstream is heading East at 100 knots. If you do not change you heading to accommodate this, for every 48 you progress North, the wind will carry you, off track to the East 10. Rather than be 10 miles off track every six minutes; you correct for the drift i.e. alter heading to the West. With high wind speeds and high wind correction angles comes a penalty. The angle of correction required reduces the value of the True Airspeed. Your 480 TAS ‘effectively’ becomes 470, due to the vectors involved.
So what cries the mob – well when you are looking for a needle in a haystack a small differential of 5 to 10 knots every 6 minutes over lets say 5 hours, becomes a huge area. Work with 5 knots x 10 = 50 miles (92.6 Kms) x 5 hours = 250 miles (463 Kms). So even an analysis of the effective TAS reduction due to wind aloft demands detailed, accurate knowledge of several factors. This element, if not acknowledged, alone casts doubt over the area of intended search.
Whether the aircraft was ‘Navigating’ to a predetermined way point or not becomes another important element. If, as many would have it the aircraft was flying a ‘Heading’ then wind and temperature data becomes essential if the search area is to be accurately defined. If the aircraft was ‘tracking’ then the effective speed become important.
When you start to operationally define this flight the odds against any sensible conclusion being drawn, without full knowledge, are slightly more than throwing a dart at a map and betting $100,000,000 that you are right.
My sincere apologies to pilots and navigators everywhere; this ramble was not intended to do any more than outline why many, taking well intended liberties in trying to define the most probable search area should not. I know none of us can define it; not accurately. We simply do not have the required information to even begin to make an educated guess. Starting with the very basics, through to the sophisticated satellite data, there has not been enough information made publicly available for constructive, nice analysis. We must rely on the integrity of the powers that be to provide those answers; but I’m ducked if I can find any that make good, sound operational sense.
Here endeth the ramble; if you managed to plough your way this far – have a CF
Toot toot.
Now I don’t want to get into the deep technical here; but I do want to raise some questions related to ‘how’ the search area was actually defined – from the navigation data provided and the apparent assumptions drawn from assumed data. Basic. potted stuff follows, I know; but, I keep reading articles where ‘confusing’ terminology is worked into a theory or notion and presented as ‘hard’ fact. Without accurate flight planning data and the actual weather data for any of the assumed direction of travel; from an accurate start point, tackling the end of journey point, as purely a navigational and operational exercise, becomes the stuff of nightmare. When pure ‘guess-work’ is melded with inaccurate terminology; well, you can see where I’m heading. For instance:-
Heading – much is made of the aircraft’s ‘heading’. It wearies me to keep reading about this item. A ‘heading’ is, simply put, what the compass reads. Lets say you want to head North; but which North, there are basically two reference choices – Magnetic or True – and corrections must be made, if you wish to arrive in Albuquerque not Mecca. But the ‘heading’ is the basis on which navigational outcomes are based.
Track – simply put; the ‘track’ defines the actual path the aircraft travels. Say you still want to go North but the air through which you are travelling is moving from West to East. If you simply make your heading ‘N’ (360˚) then you will be carried East of your desired ‘track’ at a rate commensurate with the speed of the wind,. So; if Albuquerque is 200 miles North of your starting point, you will, 200 miles later be a considerable distance to the East of there, if you don't adjust the heading .
Wind Correction Angle – to avoid this embarrassment, a prudent pilot has a look at the ‘winds aloft’ prediction for the desired track and then, by a ridiculously simple method adjusts the basic heading to allow for ‘drift’. This is, surprisingly, known as the wind correction angle. The vagaries of the actual wind against those forecast become a simple matter of weighing the ‘track-made-good’ against where the aircraft actually is and a further simple correction is made to regain the desired track.
Speed – is a truly moveable feast of potential confusion. Almost every element of flight affects it, from power to weight, from temperature to altitude, from turbulence to aircraft trim. One of the basic ‘must’ have navigational speeds is the rate at which the aircraft travels over the earths surface, to wit; the ground speed. Another essential is the ‘True Airspeed’ (TAS).
TAS is, stand alone, a strange beast. A simple method of coming to terms with it is the ‘ICE-T’ formula. I= Indicated (IAS is what’s on the dial) – C =Calibrated (IAS corrected for position installation error)– E= Equivalent (EAS is CAS corrected for compressibility); from which TAS which defined, i.e. the EAS corrected for temperature and pressure altitude.
Why is the fool rabbiting on about this? Well, it is important if theory is to meet reality; for example; once you have defined the true speed of your aircraft and corrected the speed over the ground for wind; once you venture up into the higher atmosphere it really, really matters that these assumptions are correct. Above 25, 000 feet (ish) things change, the rate at which the temperature changes for example; but one of the real changes is the wind speed range and the ‘jet stream’. Anywhere between 60 to 120 knots (nautical miles per hour) is almost routine. These may be thought of as ribbons or ‘corridors’ of very fast moving air.
Just pretend you are still heading North at lets say 480 knots TAS (48 every six minutes) and the Jetstream is heading East at 100 knots. If you do not change you heading to accommodate this, for every 48 you progress North, the wind will carry you, off track to the East 10. Rather than be 10 miles off track every six minutes; you correct for the drift i.e. alter heading to the West. With high wind speeds and high wind correction angles comes a penalty. The angle of correction required reduces the value of the True Airspeed. Your 480 TAS ‘effectively’ becomes 470, due to the vectors involved.
So what cries the mob – well when you are looking for a needle in a haystack a small differential of 5 to 10 knots every 6 minutes over lets say 5 hours, becomes a huge area. Work with 5 knots x 10 = 50 miles (92.6 Kms) x 5 hours = 250 miles (463 Kms). So even an analysis of the effective TAS reduction due to wind aloft demands detailed, accurate knowledge of several factors. This element, if not acknowledged, alone casts doubt over the area of intended search.
Whether the aircraft was ‘Navigating’ to a predetermined way point or not becomes another important element. If, as many would have it the aircraft was flying a ‘Heading’ then wind and temperature data becomes essential if the search area is to be accurately defined. If the aircraft was ‘tracking’ then the effective speed become important.
When you start to operationally define this flight the odds against any sensible conclusion being drawn, without full knowledge, are slightly more than throwing a dart at a map and betting $100,000,000 that you are right.
My sincere apologies to pilots and navigators everywhere; this ramble was not intended to do any more than outline why many, taking well intended liberties in trying to define the most probable search area should not. I know none of us can define it; not accurately. We simply do not have the required information to even begin to make an educated guess. Starting with the very basics, through to the sophisticated satellite data, there has not been enough information made publicly available for constructive, nice analysis. We must rely on the integrity of the powers that be to provide those answers; but I’m ducked if I can find any that make good, sound operational sense.
Here endeth the ramble; if you managed to plough your way this far – have a CF
Toot toot.