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Does anyone still use the hp41 airborne?
01-26-2014, 04:25 PM
Post: #1
Does anyone still use the hp41 airborne?
Thanks for the community for the continued enthusiasm for the hp41 system.

Inspired by some of the amazing tools still available I assembled a collection of routines for hp41cx into a .MOD file. The core is an alarm function which performs a deduced reckoning calculation to estimate lat/long.

It is submitted for amusement only. The principal heading calculation is flawed and magnetic variation is not handled correctly.

As I have time I may refactor the DR calculations to pull out course, heading, wind correction and variation as separate variables. There are a set of routines not included to print out a navigation log of sorts using the original HP printer.

I also need to determine a new variation model.

There is a PDF manual intended mostly as a tribute to all the original cartridges:

http://www.filedropper.com/hp41slantr-g
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01-27-2014, 12:16 AM
Post: #2
RE: Does anyone still use the hp41 airborne?
1525366 Thanks

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01-27-2014, 05:36 PM (This post was last modified: 01-27-2014 05:44 PM by Geoff Quickfall.)
Post: #3
RE: Does anyone still use the hp41 airborne?
Absolutely!!!!!

Check out my youtube video at HHC2013 to see some of the programs I have. All the programs are on my CL but previous to that the 41cx because they both have an actual clock. The CX/CL has been on my DC10, B767, B737 and the B777 since 1986 and before that in the bush flying venue for ten years.

HP's at work in Aviation

Cheers, Geoff

Just looking at your documentation, great program. I remember seeing an HP41cx in a cradle mounted on a dashboard and cable connected to something. It was a poor mans GPS/FMC system. That was in the 80's at the Abbotsford airshow.
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01-28-2014, 01:42 AM
Post: #4
RE: Does anyone still use the hp41 airborne?
(01-27-2014 05:36 PM)Geoff Quickfall Wrote:  Absolutely!!!!!

Fantastic! I really enjoyed the video.

It inspires me to keep plucking at the program. I don't include magnetic variation in the heading calculation.

When I was actually using an early version of this software I was flying around Wisconsin in an old Cessna 170. I was usually pretty close to the agonic line and I didn't really have to sweat the variation. This package uses an old polynomial model and the fellow who developed it suggested I should redo the fit.

If I get really enthusiastic I'll invest in a NovRAM cartridge and see if I can build real database of US fixes.

I have a question. In your video you mention the difference between some great circle distances from your FMS and the values you would calculate. Might be due to which geodetic datum you are using versus your Boeing?

Is it possible that the airplane uses your planned altitude to compute the track length? You fly high enough that 2pi would be a small discrepancy against the charted distance?

Again, I really enjoyed the video.
Thanks
Todd
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01-28-2014, 03:30 AM
Post: #5
RE: Does anyone still use the hp41 airborne?
(01-28-2014 01:42 AM)twdeckard Wrote:  I have a question. In your video you mention the difference between some great circle distances from your FMS and the values you would calculate. Might be due to which geodetic datum you are using versus your Boeing?

Is it possible that the airplane uses your planned altitude to compute the track length? You fly high enough that 2pi would be a small discrepancy against the charted .

The airplane FMC (Honeywell) doesn't care about altitude increasing the GC distance. I prove this to the inquisitive by plotting a 200 mm line at 90 degrees to the flight path; a 5,000 nm line and a 10,000 nm line also at 90 degrees to the flight. These three plots are all the same line of longitude but only coincide when directly over the shortest. The reason is that the shorter the line the closer to the surface of the earth it is, conversely, the longer the line the more it bisects the curve of the earth. Therefore they only coincide when at 90 degrees (vertically perpendicular) to the shortest. Otherwise it is a slant view.

The real reasons, a guess, I don't correct for an oblate spheroid (the earth); vendor error, how do they round and; there datum, airport central?, tower? Geographic centre? Nav aid fix? The error is extremely small in any case and I only use it as a gross check for fuel predictions at flight planning.

Cessna 170, what year? Nice and a tail dragged to boot. Lots of time on a 180 but it had floats!
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01-28-2014, 07:24 AM
Post: #6
RE: Does anyone still use the hp41 airborne?
Very nice video! It's cool to see that the HP 41 is still useful in a Boeing cockpit after being used on board the Space Shuttle and the Concorde.
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01-28-2014, 08:34 AM (This post was last modified: 01-28-2014 08:35 AM by Geoff Quickfall.)
Post: #7
RE: Does anyone still use the hp41 airborne?
Thanks Didier,

The point of the talk was to show the HP techies that there is a place for a non graphing, higher ability science machine today.

It doesn't have to be graphing. For example, I love the prime, but I need the IR printer as I like a hard copy.

Looking forward to the 43 and love the 34s which I have converted to IR printer and clock.

Cheers,

Geoff

Of course the 41 holds a prime spot in my world as it has been with me from the 41 c to the Cv, C and now the CL :-). It is my favorite and I am lazy. Thanks to the CL it is on the flight deck and fast!
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01-30-2014, 03:54 AM
Post: #8
RE: Does anyone still use the hp41 airborne?
(01-28-2014 03:30 AM)Geoff Quickfall Wrote:  Cessna 170, what year? Nice and a tail dragged to boot. Lots of time on a 180 but it had floats!

A 1948 of course. The 180 is one of my fantasy airplanes.

Here is a picture of it parked at OSH.

   
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01-30-2014, 07:34 PM
Post: #9
RE: Does anyone still use the hp41 airborne?
Nice! Flew a 1938 Beech 18 for a season, also on floats and serial number 0004 DeHavilland Beaver on floats as well as a 1938 Nordyn Norsemen. Nothing like smell of old avionics and leather! The Norsemen and Beech I flew are in museums now. The a Beaver is the oldest one still flying as 1 thru 3 are also in museums including the smithsonian.

Cheers
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