Could my tomtom have saved lives

dizzyfergy · Posted: Fri Aug 31, 2007 9:04 pm Post subject: Could my tomtom have saved lives

Probably on the wrong forum, but it is Friday night and I have had a few shandys.
Having just watched a discovery program on sky about an aircraft crashing due to a pair of sensor ports been blocked up , preventing the correct altitude and air speed been shown , the question is after noting on my tom-tom how the trip master add-on program displays speed and altitude , could providing the tom-tom could pick up a signal through the aircrafts window be able to correctly monitor its air speed and altitude and thus give the air crew enough information to avoid the aircraft crashing . This is probably one for the tech guys out there.

mikealder · Posted: Fri Aug 31, 2007 9:42 pm Post subject:

Most certainly not, the Static ports that were blocked by tape supply information about air pressure and feed information to the aircrew and black boxes within the jet that contrl the moving surfaces on some aircraft types, a satnav device within an aircraft would not indicate true air speed, altitude or attitude - therefore the information offered to a pilot would be of very little benefit - Mike
Thread moved to a more suitable section - Mike

dizzyfergy · Posted: Fri Aug 31, 2007 10:20 pm Post subject:

Yes i understand your answer ,but the programme also indicated the if the pilot and co pilot had basic information about the aircrafts speed and altitude they could have possibly flown the aircraft till they could gain a visual reference of there altitude and air speed ( ie when day light broke) the basic question was could my tottom using the tripmaster software give a reasonably acurate altitude and airspeed to enable the crew to fly the air craft, till daylight broke, or how acurate is the display in relation to altitude and speed up to the speeds and altitude a commercial airliner flies.

mikealder · Posted: Sat Sep 01, 2007 9:23 am Post subject:

Lets just look at the two technologies for a while:

Aircraft use kcas (Knot's Calibrated Air Speed), this is where a combination of pitot and static pressure are used to provide an airspeed indication.
Altitude uses static pressure, further adjustment is made by the aircrew when they dial in to the altimeter the local barometric pressure (the local Air Traffic Tower will radio this information to them).

Now look at what GPS will supply:
Speed output for automotive use will be in MPH or KPH, it might even be possible to display Knots BUT this is not kcas which is required at slow speeds to avoid stalling.
Altitude, GPS is never too good at accurate height finding, when it does display an altitude it is not relative to sea level, neither can it be locally corrected for UNLESS the aircraft contains digital terrain map that has the GPS altitude and terrain relative to the GPS altitude. I certainly wouldn't trust it for flying at low level.

The crucial part is down to how fast the aircrew can detect a system failure and work out what is wrong, only then can corrective actions be taken. Working out there is an airspeed problem in flight and then getting a TomTom device out putting it on the windscreen, waiting for a fix etc....
I just don't think this would work, the engineering units employed and the subtle differences that are required for aircraft airspeed would result in the same outcome to the one you watched last night - Mike

dizzyfergy · Posted: Sat Sep 01, 2007 2:11 pm Post subject:

Guess i can leave my tomtom in the suitcsae next time i fly.
Thanks for the intresting info though.

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