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Old 07-13-2012, 07:39 AM
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klem klem is offline
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Quote:
Originally Posted by bongodriver View Post
In a nutshell Klem yes I think you got it.

as long as your calculations arrive at a density altitude, I prefer 'rule of thumb' calculations over the boffins pages of calculations personally, they may be very slightly less accurate but for the effort it takes.........

heres another one that might be usefull......

TAS increases by 2% over IAS per 1000' and this is also affected by density altitude, this has the surprising effect of increasing the TAS when temparatures are high, we normally associate hight temps with a degradation in performance.

eg.

lets say cruising at pressure alt of 10,000' at 300kts with ISA +10

2% 300kts per 1000' = 60 kts so TAS@ 10,000' = 360 kts in standard conditions.

ISA +10 = 1200' higher density altitude so 10,000' pressure alt = 11,200' density altitude which in turn means another 2% TAS increase = 366kts TAS
OK, well the calculations take place in the script so its not a problem but I'll run those "2%" estimates alongside them just for the hell of it. Hopefully find time this coming weekend.

btw I'm assuming those old A&AEE TAS charts used density altitude as well otherwise the whole measurement process is pointless. They do say 'on a standard day'.
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