DM41L at work

[Geoff Quickfall]

okay,

lots of responses and I will ignore the language associated ones. English is my second language, I don't have a first language unfortunately.

Paul and HrastProgrammer

1. I had a 1996 Magellan GPS which i suctioned cupped to the rear cockpit windshield of the 737-200. The aircraft had no GPS capability. It cruised up to 36000 at Mach .74. The GPS functioned perfectly although it was not licensed for aviation use. It was fun to play with at the time. The reason it had to be on the rear cockpit window was that the windows are two panes sandwiching a liquid vinyl inside heated by clear aluminum sheeting which keeps the vinyl and window warm. This creates a barrier to radio reception. The main front and large side windows are heated on the 737 and interfered with the handheld GPS reception. Another problem is when it is stuck to a window you can only receive from the satellites on that side of the aircraft.
2. the DC10! that brings back memories but substitute the HP 48 with my 41CX running the same programs the DM 41L is shown to have loaded plus a few more like critical point, point of no return, optimum altitude, anti skid inop, full lido flight plan with printer capability plus a few others.
   

Walter, may be impractical but still usable. I wrote these for the 41CL in 1986 while on the DC-10. The largest on board computer on that airplane had 4K worth of memory. The 41CX saved a lot of time!

For a thorough explanation of these programs including formulae and etc. see my presentation for HHC2013: HP calculators in aviation

• The first three routines starting from the left of the user keyboard reference: load waypoints; great circle; intermediate latitude are calculated by the on board flight management computers so they are redundant, EXCEPT as an independent calculation free of any bugs that may be present in the vendors data base. Also, when in the middle of the Atlantic with an air traffic control route change, the routines provide a crosscheck to the on board flight computers. The crosscheck is usually provided by the hardcopy flight plan but when the route changes the flight plan does not reflect the new true track and great circle distance needed for crosschecking. The intermediate latitude check provides an independent crosscheck to the onboard systems also. At my airline it is standard procedure to plot on the chart a point 2 degrees after each waypoint and check the latitude.
• Temperature Corrections: The onboard altimeters do not correct for temperatures below 0'C and significant altitude errors occur the greater the temperature is below 0. Some aircraft have this function built into the altimeter where the current outside air temperature is dialed in. B777 do not nor did the DC 10, 767, and 737 that I flew. Hence, instead of using a chart with interpolation required I use the actual formula to produce the actual altitudes. See my 2013 presentation for a more detailed description including the formula used.
• Fuel in Tank: Ever since the Gimli (click on GIMLI for an article) incident checking the fuel placed on board by the fueler in litres converted to Kgs and comparing that to the gauges in Kgs the Fuel in Tank program is very useful. Either that or a pad, a calculator and a pen.
• Break schedules: for long haul flights, well there is an APP for that but not as flexible as my program written in 1986 and still useful today. Usually the 41CX or the 42S and now the printing Woodstocks along with the IR printer accompany me and hard copies of the breaks are produced. Can't get the APP to print!
• world time program: the clock on board is GMT, the onboard computer tells us the arrival time in GMT, this program prompts for the destination airport and gives you the time of day, day and date.
• flight time program: great routine and uses extended memory. once started provides a countdown timer, chronograph, and calculates the current time, day and date plus the estimated arrival time day and date. very useful when you are walking the cabin during the flight and someone asks.
• set gmt and alarm: the calc is always in GMT so when I use it as an alarm clock in different time zones this program will calculate the correct time given the airport three letter code and set the alarm.
  

So while one can get by without the calculator and the routines, life sure is easier with it. So I disagree with your friends analysis of 'impractical'.

For all those commenting on stuff in the flight deck not locked down. These photos were for demonstration purposes here during a smooth flight. The calcs reside in my flight bag. I have yet to be hit by flying HPs over the last 40 years of flying!

Cheers and happy new year!

Geoff

p.s. I am getting used to the keyboard layout even though it may violate the sensibilities of some