Max drift calculation
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like i said you use the same method for drift calcualation, but on your legs if you have a head wind and are slower you just recaluate your ETA. This is why for example on a 15 min leg you have a chx point 1/2 way (7min 30) and you then simply work out your new ETA. You also put away your map for the whole flight, only getting it out 30 secs or so before your next ETA and then refresh for what you are looking for. (as you memorise your route before t/o)
The whole system is geared towards low level navs where you cannot afford to be blundering around with a wheel/staring at a map every 30 secs.
Clock and compass are the most important instruments when doing a nav.
The whole system is geared towards low level navs where you cannot afford to be blundering around with a wheel/staring at a map every 30 secs.
Clock and compass are the most important instruments when doing a nav.
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Oh for gods sake
for nearly every training single windspeed divided by two will work, its this anal attention to detail that will mean somebody flying into a hill or landing with the gear up.
It only really going to be useful in the case of an in flight diversion (as in the PPL skill test) at which point you will be using a hand drawn line to track to and an ETA based on either 1, 1.5 or 2 miles per minute so what if the max drift is out by 2 or 3 degrees IT DOESNT MATTER!!!!!!
You would do the student a better service by getting his head outside and emphasising that a QDM call (if available) would better serve his purpose.
I would be delighted if one of my students simply added or subtracted 5 or 10 or 15 degrees instead of confidently announcing 13 degrees left drift required which unfortunately didn't take into account the 10 degrees that he has been flying off heading whilst he/she worked it out!!!
It only really going to be useful in the case of an in flight diversion (as in the PPL skill test) at which point you will be using a hand drawn line to track to and an ETA based on either 1, 1.5 or 2 miles per minute so what if the max drift is out by 2 or 3 degrees IT DOESNT MATTER!!!!!!
You would do the student a better service by getting his head outside and emphasising that a QDM call (if available) would better serve his purpose.
I would be delighted if one of my students simply added or subtracted 5 or 10 or 15 degrees instead of confidently announcing 13 degrees left drift required which unfortunately didn't take into account the 10 degrees that he has been flying off heading whilst he/she worked it out!!!
No - what G/S do you plan with?
You surely don't just assume still air and then cuff it on observed times at fixes? In the example I gave, what G/S did you use to work out your ETA at the turning point prior to take-off?
And yes, I have done some low level flying in my time. At 420 KIAS, for example, the correction to make good time was based on 'increase KIAS by same numerical value as seconds early or late and maintain for the numerical value of miles per minute'. Thus 10 sec early at fix, fly at 420-10=410 for next 7 min. It worked very well.
But medium level requires proper pre-flight computer work in low speed (<180 KIAS) aircraft as errors are induced to a far greater extent if the wind differs from the planned W/V than in fast aircraft at low level.
Having (presumably) worked out an MDR G/S in your pre-flight planning, what technique do you apply to your track distances to obtain an accurate ETA?
You surely don't just assume still air and then cuff it on observed times at fixes? In the example I gave, what G/S did you use to work out your ETA at the turning point prior to take-off?
And yes, I have done some low level flying in my time. At 420 KIAS, for example, the correction to make good time was based on 'increase KIAS by same numerical value as seconds early or late and maintain for the numerical value of miles per minute'. Thus 10 sec early at fix, fly at 420-10=410 for next 7 min. It worked very well.
But medium level requires proper pre-flight computer work in low speed (<180 KIAS) aircraft as errors are induced to a far greater extent if the wind differs from the planned W/V than in fast aircraft at low level.
Having (presumably) worked out an MDR G/S in your pre-flight planning, what technique do you apply to your track distances to obtain an accurate ETA?
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Do 90 - acute wind angle then use clock analogy to get headwind/tailwind component.
E.g. Track is 180
Wind is 240/30. So 90 - 60 = 30
30, so take half of the windspeed, gets headwind component of 15kts.
Hence, groundspeed for planning on this leg is IAS - 15kts (say 75kts for average GA ac).
To work out fix times, do simple leg distance / groundspeed calc.
E.g 42nm leg = 42/75 x 60 = 36 mins
Then work out proportional distances/times to fixes on the leg, ideally at some good fraction like 1/4 or 1/3 way along.
I don't think you have to bother about temp. differences etc.. on the IAS
E.g. Track is 180
Wind is 240/30. So 90 - 60 = 30
30, so take half of the windspeed, gets headwind component of 15kts.
Hence, groundspeed for planning on this leg is IAS - 15kts (say 75kts for average GA ac).
To work out fix times, do simple leg distance / groundspeed calc.
E.g 42nm leg = 42/75 x 60 = 36 mins
Then work out proportional distances/times to fixes on the leg, ideally at some good fraction like 1/4 or 1/3 way along.
I don't think you have to bother about temp. differences etc.. on the IAS
Some of the posts on this thread will make very useful discussion points at the next instructor seminar....
No wonder so many airspace busts happen if people are so glib about accurate pre-flight planning.
No wonder so many airspace busts happen if people are so glib about accurate pre-flight planning.
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i agree, there is no excuse for airspace busts, that is down to poor airmanship. if you are planning to fly near airspace always us ground points in relation to where the airspace is, there is no excuse.
Worked out the G/S yet?
Minimise sources of error by applying the well known principles (or at least they were when I was taught navigation in the RAF):
PLAN ACCURATELY
FLY ACCURATELY
THINK AHEAD
Minimise sources of error by applying the well known principles (or at least they were when I was taught navigation in the RAF):
PLAN ACCURATELY
FLY ACCURATELY
THINK AHEAD
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Not sure if BEagles comment about glib planning refers to anything I said in my post..... anyway, if we are talking about Nav planning I think you also need to consider the context. For example, if I was on a PPL or CPL training course, overseas landaway etc... I would plan with whizz wheel and do a full PLOG etc... If I was just doing a localish landaway, say Leicester to Sheffield City I would draw on the route, work out wind corrected headings, ground speeds, times at fixes etc.. with MDR and back that up with a GPS route to same points. Flying it I would use my fix times backed up with the 'time to' type function on my GPS as a cross check. I don't think that's gash?
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Surely it's important in this type of discussion to remember that mental mathmatical gymnastics requires a person with the mental ability and agility more related to a selected and young RAF trainee, flying and 'living' aviation on a daily basis.
Most of us in general aviation may be as bright as them but are not necessarily as young or as regular in our practice of in-flight mathematics.
Nothing can replace the experience of our more mature years but there is little doubt that, for the hobby flyer, nothing can better detailed pre planning for any flight - anything which will reduce mental effort during the actual flight must contribute to safety.
In G.A. we have the luxury of a) time to pre plan and b) aircraft with lower speeds and less demands on the pilot than military aircraft, e.g. we do not have weapon systems to manage or low heights to negociate.
Most of us in general aviation may be as bright as them but are not necessarily as young or as regular in our practice of in-flight mathematics.
Nothing can replace the experience of our more mature years but there is little doubt that, for the hobby flyer, nothing can better detailed pre planning for any flight - anything which will reduce mental effort during the actual flight must contribute to safety.
In G.A. we have the luxury of a) time to pre plan and b) aircraft with lower speeds and less demands on the pilot than military aircraft, e.g. we do not have weapon systems to manage or low heights to negociate.
Neither do I, blagger. What you describe is a blend of pragmatism and experience.
UAV689's method has yet to be explained, but it does not seem particularly sound....
UAV689's method has yet to be explained, but it does not seem particularly sound....
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you are taught to get round a nav route safely and in the easiest manner possible, you work dont work out your g/s just your heading correction using MDR. because your using well defined points, memorising your route exactly (after leg 1 I turn right to 220 should cross a power lines and see a lake to my right etc) and your using these HAT chxs pre and post turning point. Simple, easy, safe fail proof. If your running late or fast you just recaluate your new ETA based on the what the time difference is , eg 30 secs late after first half of leg your gonna take an extra minute for the whole leg. As you have now excess power to catch up on lateness whats the point of working out GS. Never bust airspace in my life and don't plan to, and knowing how fast you are going will not stop you busting airspace, but more likely make you do it if you have your head down, working out a complicated formuale.
I am sure the big boys in the RAF using all those techniques you speak of, but for EFT its not needed.
I am sure the big boys in the RAF using all those techniques you speak of, but for EFT its not needed.
How can quantify any observed errors unless you have an accurate original assumption against which to assess them?
You need to work out your G/S pre-flight in order to be able to quantify your observed errors. Pre-HAAT and post-HAAT are not relevant in this context.
Do you actually know how to do so? Seemingly not.
Still waiting for your solution to the problem I set you.
You need to work out your G/S pre-flight in order to be able to quantify your observed errors. Pre-HAAT and post-HAAT are not relevant in this context.
Do you actually know how to do so? Seemingly not.
Still waiting for your solution to the problem I set you.
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In response to BEagles problem, think the GS with whizz wheel is 100kts and with the MDR method is 103kts. On a 40nm leg would be 30s difference in timing for example.
Of course, all this is based on forecast winds - think that is another thread in itself! It'd be interesting to see what people use for planning winds - I tend to use the spot forecast, but also have a look at METARS of airfields along the way and approximate the 2000ft wind to just check there is no wacky differences around.
Of course, all this is based on forecast winds - think that is another thread in itself! It'd be interesting to see what people use for planning winds - I tend to use the spot forecast, but also have a look at METARS of airfields along the way and approximate the 2000ft wind to just check there is no wacky differences around.
I came up with 104.5 knots using a web-based planning tool, and 105 using MDR:
Wind is 40 deg off, so about 3/4 to apply to the headwind, that's 15 knots, G/S is 105.
Which is 7/4 miles per minute and makes ETA estimates very simple.
The point which blagger and I have both made is that use of MDR for pre-flight planning is insufficiently accurate unless you also work out the planned G/S and corresponding fix point ETAs before flight. But it would be just as quick to use the whizz-wheel - particularly for time v distance estimates.
Using still-air IAS for low level high speed flying is one thing, ignoring W/V for pre-flight planning in a plastic puddlejumper at 3000 ft quite another. In the example I quoted, you would start your navigation exercise with an immediate 14% error which is wholly unacceptable. Try that on a PPL Skill Test and you will certainly fail.
Wind is 40 deg off, so about 3/4 to apply to the headwind, that's 15 knots, G/S is 105.
Which is 7/4 miles per minute and makes ETA estimates very simple.
The point which blagger and I have both made is that use of MDR for pre-flight planning is insufficiently accurate unless you also work out the planned G/S and corresponding fix point ETAs before flight. But it would be just as quick to use the whizz-wheel - particularly for time v distance estimates.
Using still-air IAS for low level high speed flying is one thing, ignoring W/V for pre-flight planning in a plastic puddlejumper at 3000 ft quite another. In the example I quoted, you would start your navigation exercise with an immediate 14% error which is wholly unacceptable. Try that on a PPL Skill Test and you will certainly fail.
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these errors are so small, no one will fly at exactly the correct speed for exactly the whole leg, at precisley the correct heading. which i why the dead reckoning method works, and if from 30 secs/1 min away from your waypoint or further if you see it simply fly to it! would be interesting to see how many UAS studes have bust airspace in comparsion to ppl studes..i agree the proper planning is needed but in real life it is over the top.
Glider pilots regularly fly in excess of 500 kms without calculating any of this before they fly, just drawing a route on the map.
Glider pilots regularly fly in excess of 500 kms without calculating any of this before they fly, just drawing a route on the map.
PLAN ACCURATELY
FLY ACCURATELY
THINK AHEAD
UAV689, what you describe is thoroughly gash and unprofessional. Neither is it 'Dead Reckoning'.
Glider pilots, incidentally, are unlikely to maintain a precise track due to the availability of lift, so your comparison is invalid.
All my UAS students were able to plan accurately - are things really so dumbed-down nowadays?
Failure to complete proper planning is not 'over the top' - it is pure laziness.
FLY ACCURATELY
THINK AHEAD
UAV689, what you describe is thoroughly gash and unprofessional. Neither is it 'Dead Reckoning'.
Glider pilots, incidentally, are unlikely to maintain a precise track due to the availability of lift, so your comparison is invalid.
All my UAS students were able to plan accurately - are things really so dumbed-down nowadays?
Failure to complete proper planning is not 'over the top' - it is pure laziness.
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Beagle
2 straightforward reply's please.
Do you have your nav students take a whiz wheel and ruler in the air with them?
What is the procedure you advocate for diverting to an unplanned alternate airfield lets say due to a blocked single runway?
And with all due respect, all this talk of low level nav at 420knots and vulcans has absolutley no relevance here, lets base the rest of this thread on a Cessna 152/172 shall we.
head down nav planning in flight or trying to do complex mental arithmetic in flight is bollox imho
2 straightforward reply's please.
Do you have your nav students take a whiz wheel and ruler in the air with them?
What is the procedure you advocate for diverting to an unplanned alternate airfield lets say due to a blocked single runway?
And with all due respect, all this talk of low level nav at 420knots and vulcans has absolutley no relevance here, lets base the rest of this thread on a Cessna 152/172 shall we.
head down nav planning in flight or trying to do complex mental arithmetic in flight is bollox imho
Pre-flight - Dalton or its electronic sibling.
In-flight - MDR. Never a whizz-wheel!
In flight diversion:
Draw line from nearby landmark to diversion aerodrome using chinagraph and edge of checklist.
Measure distance using miles scale on back of checklist (which ours have as I designed them that way!) - write on laminated back of checklist.
Use checklist like parallel rule to nearest VOR rose - draw line through rose and read off track.
You now have track and distance.
Apply MDR wind to establish heading and groundspeed - you should have worked out max drift prior to flight and drawn a wind arrow on your chart.
My checklists have nice clear laminated backs upon which to scribble your sums. But don't forget to l
kout!
Set off when ready; fly heading and time backed up by visual confirmation.
I agree that high speed low level techniques are not relevant to low speed medium level navigation.
In the Vulcan one had a navigator to work such things out. Two actually...
In-flight - MDR. Never a whizz-wheel!
In flight diversion:
Draw line from nearby landmark to diversion aerodrome using chinagraph and edge of checklist.
Measure distance using miles scale on back of checklist (which ours have as I designed them that way!) - write on laminated back of checklist.
Use checklist like parallel rule to nearest VOR rose - draw line through rose and read off track.
You now have track and distance.
Apply MDR wind to establish heading and groundspeed - you should have worked out max drift prior to flight and drawn a wind arrow on your chart.
My checklists have nice clear laminated backs upon which to scribble your sums. But don't forget to l
kout!Set off when ready; fly heading and time backed up by visual confirmation.
I agree that high speed low level techniques are not relevant to low speed medium level navigation.
In the Vulcan one had a navigator to work such things out. Two actually...
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So....
to quote you "Worked out the G/S yet?"
Whats the ground speed on the diversion because you need an ETA becuse you may stumble into the CAS beyond your destination.
Whats the Ground speed, No Whizz wheel, no internet application you have 25 hours on a C150 and probably 2 to three hours ground instruction on Nav???
You are using a transposed radial from a VOR that might be 60 miles away on the other side of your map, on your knee , in a cramped cockpit whilst flying the airplane and trying to remember what your instructor said.
I'll say again - complex mental arithmetic in the above situation is prone to error and worse still gross error, he/she might work out the drift to the degree and apply it incorrectly.
Simple concepts: -
Wheres the wind? is it pushing or pulling? therefore am I doing 1, 1.5 or 2 miles per minute.
Where do I want to go? if i point straight at my destination will I be left or right of it therefore will I employ 5 or 10 or 15 degrees of heading change to allow for the drift.
Why complicate matters significantly to get a very small increase in accuracy at the speeds we are discussing.
Accurate well tutored preflight planning is essential but at this level and at these speeds lets just use the principal of kiss
to quote you "Worked out the G/S yet?"
Whats the ground speed on the diversion because you need an ETA becuse you may stumble into the CAS beyond your destination.
Whats the Ground speed, No Whizz wheel, no internet application you have 25 hours on a C150 and probably 2 to three hours ground instruction on Nav???
You are using a transposed radial from a VOR that might be 60 miles away on the other side of your map, on your knee , in a cramped cockpit whilst flying the airplane and trying to remember what your instructor said.
I'll say again - complex mental arithmetic in the above situation is prone to error and worse still gross error, he/she might work out the drift to the degree and apply it incorrectly.
Simple concepts: -
Wheres the wind? is it pushing or pulling? therefore am I doing 1, 1.5 or 2 miles per minute.
Where do I want to go? if i point straight at my destination will I be left or right of it therefore will I employ 5 or 10 or 15 degrees of heading change to allow for the drift.
Why complicate matters significantly to get a very small increase in accuracy at the speeds we are discussing.
Accurate well tutored preflight planning is essential but at this level and at these speeds lets just use the principal of kiss
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Pre plan or blag
I've not listened to such a lot of rubbish for a long time!
The basics of navigation training is not about blagging your way around the home counties or wherever else is just down the road. GPS is a fantastic tool and so at one time were VOR's thus considered. However, the RNAV computations and the software of the modern GPS exploit the very same traditional navigation techniques for which so many of you in your ignorance treat with such contempt.
I wonder how many of you reinventors of the wheel have been any great distance away from the comfort of home flying to the range of your aeroplane over unkown country with few known features WITHOUT the aid of our modern kit. If you have you will not be one of those who choose to ignore the very well defined principles of PLAN, PLAN, PLAN. Do the work on the ground in comfort with a cup of tea and a bacon butty or work your nuts off shouting for MUM! when your completely lost - the choice is yours.
Whatever your choice please do your students a favour and teach them properly for they may need those basic skills sometime in the future which will save them from becoming a fool to circumstance.
Should the worse happen they won't be shouting mum, they'll be cursing YOU!
The basics of navigation training is not about blagging your way around the home counties or wherever else is just down the road. GPS is a fantastic tool and so at one time were VOR's thus considered. However, the RNAV computations and the software of the modern GPS exploit the very same traditional navigation techniques for which so many of you in your ignorance treat with such contempt.
I wonder how many of you reinventors of the wheel have been any great distance away from the comfort of home flying to the range of your aeroplane over unkown country with few known features WITHOUT the aid of our modern kit. If you have you will not be one of those who choose to ignore the very well defined principles of PLAN, PLAN, PLAN. Do the work on the ground in comfort with a cup of tea and a bacon butty or work your nuts off shouting for MUM! when your completely lost - the choice is yours.
Whatever your choice please do your students a favour and teach them properly for they may need those basic skills sometime in the future which will save them from becoming a fool to circumstance.
Should the worse happen they won't be shouting mum, they'll be cursing YOU!