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Old 11th July 2004 | 13:44
  #35 (permalink)  
hugh flung_dung
25 Anniversary
 
Joined: Jan 1999
: CPL
Posts: 899
Likes: 42
From: Slowly decaying (disgracefully)
Sorry AWL, that's all a bit OTT - you must see very different PPL studes to mine if they can cope with that

I think there's a much simpler way:
  • plan your IAS to give an easy TAS such as 90, 100, 120, 150, etc (using IAS=TAS-2% per 1000 ft and -2% per 10 deg above ISA)
  • calculate your leg times based on still air and TAS (2/3, 0.6, 0.5, 0.4, etc)
  • modify the leg time based on the head/tail wind component percentage of TAS.
In other words:
Flying at 3000ft at ISA, 120TAS = approx 115IAS.
Still-air time is now 0.5 x distance
If flying into a 10kt HWC the leg time is increased by about 8%

So, if the distance is 40 miles the estimated still air time is 20 mins and the estimated time with wind is 20+8% = 21.6 mins.
By CRP5: time = 21.8 mins.
QED

I think the wizz wheel is a great device but lots of PPLs don't seem to bother with it; also, if MDR isn't practised regularly they are unlikely to be able to use it if they need to divert. People need a way of visualising the effect of the wind and a simple set of rules with minimal sums. Any assessments should be based on simple visual proportions of known values whenever possible (eg using the DI as an "analogue computer" to <calculate> the proportion of max drift, head/tail wind components and crosswind components).

Beagle: What's the "New Track Reference" method that you mentioned? I can't recall anything of that name.

HFD
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