IAS to TAS formula
Guest
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IAS to TAS formula
Greetings all,
I am working on an Excel Flight Log spreadsheet, and was wondering if I had the OAT and the Density Alt I can convert IAS to TAS?
Is there a formula to do that? Or should I rely on my trusty E6B?
Jost poking some fun with Excel
Cheers
I am working on an Excel Flight Log spreadsheet, and was wondering if I had the OAT and the Density Alt I can convert IAS to TAS?
Is there a formula to do that? Or should I rely on my trusty E6B?
Jost poking some fun with Excel
Cheers
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Guest
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The formulae at Ed Williams Aviation Formulary (url above in the post by The The)work to 2/3 places of decimals and match up with all the FMS readouts that I have seen. However... can anyone tell me what the value of "k" is for a typical installation?
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Smurfjet,
Not so much a formula as a 'rule of thumb'. Works when conditions are close to ISA and at altitudes not flight levels.
The TAS and IAS will vary by 1.8 kts/1000'.
eg. If we're cruising at 10'000 and indicating 145kts then TAS will be 163kts.
ie 1.8(kts/1000')X 10(lots of 1000')= 18kts
145kts (IAS)
+
18kts = 163kts (TAS)
Also works just as well the other way around!!
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This will give you a quick answer that comes faily close to the real deal:
Use 2% of IAS per 1000 ft and add to IAS:
Example: IAS is 200 Knots at 25 000 ft
therefore 2% X 25000 divide by 1000 = 25
= 50% of IAS
50% of 200Knots + 200 KNOTS = 100 + 200
= 300 Knots TAS
Use 2% of IAS per 1000 ft and add to IAS:
Example: IAS is 200 Knots at 25 000 ft
therefore 2% X 25000 divide by 1000 = 25
= 50% of IAS
50% of 200Knots + 200 KNOTS = 100 + 200
= 300 Knots TAS