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/sci/ - Science & Math

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File: 40 KB, 800x485, Bundesarchiv_Bild_146-1989-039-16A,_Schwerer_Bomber_Me_264.jpg [View same] [iqdb] [saucenao] [google]
11730172 No.11730172 [Reply] [Original]

How did planes measure their speed in the past? Any instruments or calculations?

>> No.11730190

Same way cars did — a speedometer.

>> No.11730278

>>11730172
their airspeed or their relative ground speed?

>> No.11731883

>>11730278
Relative to the ground

>> No.11731984
File: 22 KB, 438x281, Faa_pitot_static_system.jpg [View same] [iqdb] [saucenao] [google]
11731984

So for the most part you'll only ever measure your instantaneous speed relative to the air mass in which you're flying (Indicated Airspeed/True Airspeed). This is most useful for staying in the air, as it's the speed at which air is moving over your control and lifting surfaces. This is done with a pitot-static system (pic related) which combines measurement of ram air pressure (force from forward speed of air ramming into a tube) and stagnation pressure (ambient pressure from altitude).

Ground speed needs to be calculated by essentially timing how long it takes to traverse between two points on the ground. This is not straightforward and is the main reason that most planes that had a mission dependent on this sort of thing had a dedicated navigator crewman. Particularly if it had to be done for periods away from the ability to make observations, such as at night or for extended periods over water.

Observation points might be:
>Large cities, particularly with distinctive buildings such as cathederals
>Natural features or formations, mountains, lakes, rivers
>If at night, sextant readings of the stars
>radio beacon direction finding (which is probably worth its own post. Google 'battle of the beams')

>> No.11731993

>>11731984
Thanks for helping me anon.

>> No.11731996

>>11731984
>>radio beacon direction finding (which is probably worth its own post. Google 'battle of the beams')
This
NDB or VOR

>> No.11732032

>>11731984
>pilot tube
I've watched enough air disasters to know how this episodes ends.

>> No.11732078

>>11732032
Please post incident reports.

>> No.11732130

>>11732078
Generally? Pitot freezes over, stops working/becomes inaccurate. Pilot doesn't realise he's fucked, gets too slow on landing approach and drops like a brick without the altitude to recover.

>> No.11732229

>>11732130
WOOP WOOP
PULL UP

>> No.11732524

>>11730172
Pitot tubes