## [DM15] Aeronautical Calculations

Contributed software for the DM10, DM11, DM12, DM15 and DM16 goes here.

Please prefix the subject of your post with the model of the calculator that your program is for.
Walter
Posts: 1713
Joined: Tue May 02, 2017 11:13 am
Location: Close to FRA, Germany

### Re: [DM15] Aeronautical Calculations

grsbanks wrote:
Wed May 20, 2020 5:17 pm
France adopted the metric system in 1795, so that's 225 years ago.

Germany, however, did so in 1872 according to Wikipedia, so that is only 148 years ago... Looks like Walter's clock has a drift of 52/148 years, so that's just over 350000 ppm.
That's just one year after it was united - pretty hard to do it much faster.

France created the metric system AFAIK. But the metric system and the USA, this is an old and really sad story, be it for 225 or 200 or whatever years. Especially since the USA officially declared to join the worldwide standard in the Seventies of last century...
Until they reliably do what they solemnly declare, we've to devote a significant part of calculator functionality to conversions of units being obsolete for 95% of mankind.
DM42 SN: 00041 β
WP 43S running on this device

HP-35, HP-45, ..., HP-35S, WP 34S, WP 31S, DM16L
AlanW
Posts: 14
Joined: Sat Mar 07, 2020 6:35 pm
Location: UK

### Re: [DM15] Aeronautical Calculations

Guenter wrote:
Wed May 20, 2020 9:24 pm
AlanW wrote:
Tue May 19, 2020 11:18 pm
Conversion between True Airspeed, (TAS), Computed Airspeed (CAS) and Mach Number (M) for a given Altitude in ....
Although CAS is a computed airspeed, CAS denotes "Calibrated Airspeed". BTW TAS is a computed airspeed also.

Günter
I agree and will change 'Computed' to 'Calibrated'

'Computed Air Speed' corrects for position error, which is the error in static pressure measurement due to the shape of the aircraft body causing a pressure change over the static pressure sensor. 'Calibrated Air Speed' additionally takes the non-linearities of the pressure sensors into account. It is 'Calibrated Air Speed' that is displayed to the pilot. BS2G199:1984 is a theoretical calculation and assumes zero position error and zero sensor non-linearity errors, so states the equations in terms of 'Calibrated Air Speed' . I will update the documentation with this and the other two corrections later today (I have to start work in a few minutes).

Many thanks, Alan
AlanW
Posts: 14
Joined: Sat Mar 07, 2020 6:35 pm
Location: UK

### Re: [DM15] Aeronautical Calculations

All errors identified to date have now been corrected in the original post (including the description in the hp15c simulator save file)

Alan
AlanW
Posts: 14
Joined: Sat Mar 07, 2020 6:35 pm
Location: UK

### Re: [DM15] Aeronautical Calculations

Verification check of program.

Data from BS2G199:1984 Table 4

Code: Select all

Height (ft)	CAS (kts)	M		TAS (kts)
0		150		0.2268		150.00
0		300		0.4535		300.00
0		600		0.9071		600.00
0		875		1.3228		875.00
20000		150		0.3321		204.00
20000		300		0.6513		400.10
20000		600		1.2421		763.05
20000		875		1.8474		1134.86
40000		150		0.5134		294.47
40000		300		0.9653		553.68
40000		600		1.8294		1049.27
40000		875		2.8123		1613.03
60000		150		0.7939		455.35
60000		300		1.4260		817.88
60000		600		2.8525		1636.13
60000		800		4.0200		2305.75
80000		150		1.1757		681.14
80000		300		2.1721		1258.42
80000		500		3.6787		2131.23
100000		150		1.7377		1020.53
100000		350		3.9470		2317.98

All tests pass to the precision of the original data, except 80,000ft 150kts CAS, where the calculated TAS is 0.01 kts different.

I also inspected the code and removed an unused function which got in by mistake.

DM15L Verification against above data

Code: Select all

Height (ft)	CAS (kts)	CAS to M	M to TAS	TAS to M	M to CAS
0		150		0.2268		150.00		0.2268		150.00		Pass
0		300		0.4535		300.00		0.4535		300.00		Pass
0		600		0.9071		600.00		0.9071		600.00		Pass
0		875		1.3228		875.00		1.3228		875.00		Pass
20000		150		0.3321		204.00		0.3321		150.00		Pass
20000		300		0.6513		400.10		0.6513		300.00		Pass
20000		600		1.2421		763.05		1.2421		600.00		Pass
20000		875		1.8474		1134.86		1.8474		875.00		Pass
40000		150		0.5134		294.47		0.5134		150.00		Pass
40000		300		0.9653		553.68		0.9653		300.00		Pass
40000		600		1.8294		1049.27		1.8294		600.00		Pass
40000		875		2.8123		1613.03		2.8123		875.00		Pass
60000		150		0.7939		455.35		0.7939		150.00		Pass
60000		300		1.4260		817.88		1.4260		300.00		Pass
60000		600		2.8525		1636.13		2.8525		600.00		Pass
60000		800		4.0200		2305.75		4.0200		800.00		Pass
80000		150		1.1757		681.15		1.1757		150.00		Pass
80000		300		2.1721		1258.42		2.1721		300.00		Pass
80000		500		3.6787		2131.23		3.6787		500.00		Pass
100000		150		1.7377		1020.53		1.7377		150.00		Pass
100000		350		3.9470		2317.98		3.9470		350.00		Pass