Whizz-wheels, computers and MDR
MDR is my favourite nav method as the pilot navigator is forced to get his head round the anti-intuitive way in which wind affects an aircraft's progress over the ground. It's amazing that nearly all text's are full of stuff about getting groundspeeds and headings, time of flight etc using whizz-wheels and computers and how to operate them, but little about the elementary maths and trigonometry that lie at the heart of all aircraft navigation.
The main problem is guessing the wind vector. My plogs prepared the night before a xc were often a waste of time as the wind had obviously changed by the time a flight actually got going. Getting an up-to -date wind vector in flight seems to be something that nobody seems interested in but if you can get that, ie KNOWING that the wind is 20kts from 260 degT rather than going by the 214 which is only a forecast, I would have thought that was an extremely useful bit of information from which the headings and groundspeeds can be worked out by MDR, and should give accurate headings and eti’s.
I designed a bit of kit for this very purpose but it can do the lot ie pre-flight planning and en-route nav as well. It works extremely well.200yds off target in 20 nautical miles in a 70kt microlight. But you have to up-date the wind vector especially at low level.
The other thing I found out by monitoring the wind vector was that a change was often a warning that new weather was on the way. MDR gives the escape route in a worsening situation -- a huge confidence builder on lengthy navex's.
MDR is less accurate than the whizz-wheel but, as has been mentioned, not enough to make any difference in the air. Add in an accurate up-to-date wind vector and it beats any ground-based pre-flight plan hands down.
MDR ought to be in the syllabus. No wonder so many newly qualified PPL's reach for the GPS. Reason. They are uncertain, and lack the confidence to make en- route adjustments unless conditions and terrain allow easy pilotage. At least that was my experience, until I came across MDR, which was never mentioned once in all my time, training for the PPL.
Why is MDR better than the whizz-wheel? MDR tells me, not only that a wind at 45deg to the track produces three quarters of the max drift, but why. The Whizz- wheel only tells me that the drift is such and such. Lose or forget the whizz-wheel, flight computer, GPS, no batteries, electrical failure, press-onitis, low cloud-base, wind vector alters and your on your way to getting lost and making a nuisance of yourself.
Another advantage is speed. You can get the answers in the time it takes someone to get their whiz-wheel out of the flight bag and it’s even faster than a computer where you have to get into the program and print out the results. These devices do the calculations quicker than I can do them, but not if you count the time to bring them into operation, especially in the air.
Nice to know that if everything fails you can still make a good fist of getting to safety, unaided, in an unfamiliar area.
As for over the North sea, if the met conditions were favourable, should be possible, but in anything less, that’s going to be one for the GPS.