The need for (ancient) speed - measurement

[JDK]

This news item on a laser-actuated aircraft speed measuring device made me think of how old the most common types actually are.

http://www.abc.net.au/science/articles/ ... thscience3

Interesting.

We're all aware of pilot tubes, and noted that it's not spelled 'pilot' but probably not wondered any further. In fact it was invented by a French engineer, Henri Pitot in 1732! That predates powered aviation by a good 170 years... But it's not the oldest aircraft speed measurement device by a long shot...

I've seen two other kinds of airspeed measuring devices, and I idly wondered if there were more:

One is widely used on certain inter-war biplanes and is a principle well known to Leonardo da Vinci, so even older.

The other I came across on a Great War fighter type, and is a familiar type of device in regular use today on the ground, but dating to at least 1450 in concept but in the form used in aviation, dates to 1846.

Can anyone identify the two I've vaguely described, and add any other types to the list?

Just a mildly fun quizette and no prizes, just a warm feeling. Answer, if not nailed before then, tomorrow.

Regards,

[Baldeagle]

Anemometer type ASI on WW1 German aircraft? Also used on the 1903 Wright Flyer.

Some WW1 and 1920s types (Hanriot HD-1) used a venturi tube to compare suction against static instead of pressure against static.

[The Inspector]

A piece of stiff wire bent 90 degrees and screwed to a piece of wood with a paddle on the downleg and a marked scale on the piece of wood which is attached to a wing strut, faster you go, the more the paddle end is pushed aft and the higer the pointer moves up the scale.
Some things never go out of style or functionality, among others, the old piece of string in front of the windscreen has been standard on the B-47, F-14, F-18 (I believe) as a 'never fails' side slip indicator.

[Cubs]

How about a spring loaded flat plate with a pointer on the free end?

[Steve Nelson]

I remember when I was hanging around an ultralight field back in the early 80s, most had these plastic tube type airspeed indicators. Of course the materials were modern, but I suppose the basic design could go back quite awhile.

SN

[JDK]

Impressive response! 100% on my items, too, plus a couple of others...

Anemometer type ASI on WW1 German aircraft? Also used on the 1903 Wright Flyer.

In this case it's on Kermit Weeks' Albatros, seen at the Classic Fighters airshow, Omaka, NZ.

How about a spring loaded flat plate with a pointer on the free end?

Indeed!

a wind-pressure driven airspeed indicator on a 1930s deHavilland Moth. This mechanism was known to Leonardo da Vinci. [J Kightly]

http://www.culture24.org.uk/places%20to ... l/tra17625

Interesting item, Steve, I'd not come across that before, so a good score. I suspect it's technically a simple version of a pitot tube as it works on a direct pressure fliud column, as the pitots we are used to do, but better insight / classification welcome.

The Inspector's string is a yaw indicator, and goes back (on heavier than air aircraft at least) to 1911 if possibly before, as on the Bristol Military Biplane and other Boxkite derivatives.

Regards,

[Baldeagle]

I think the Wright Brothers were the first to use the yaw string, here's (mis-dated) film from 1909 at Centocelle in Italy, first film taken from an airplane I believe, showing the yaw string at work on an early Wright:

http://www.youtube.com/watch?v=vKX4d50tnmk

And question, how old is the venturi principle??
(edit: looks like it was 1797, http://en.wikipedia.org/wiki/Giovanni_Battista_Venturi )




-

[Dave Hadfield]

That paddle-blade type on the strut is the only one I ever trust on Moths.

Dave

[Baldeagle]

The Musee de l'Air at Le Bourget has an early version of the spring type flat plate ASI, from before WW1, on display. It's a bit different than the Johnson (US) or the Moth type, with the pointer being horizontal against a vertical scale, attached at a 90 degree angle to the arm holding the flat plate, which works against a small coil spring. Can't find any photos of it, although I've seed adverts for them in the pre-WW1 magazines-




-

[JDK]

Thanks for the input folks!

Anyone got more, or more background (those adverts, makers, history et al.)?

Also I was wondering about the physics behind the flat plate ASI - does it stay relatively accurate, or at the higher end of the speed envelope, does it loose precision - I ask, because if you look at it, the angles involved at higher speeds indicate less 'plate' relatively acted on by the airflow...

Interesting that the "1907/9 Centocelle in Italy" film is given also (see below) as a French made film, in an Austrian archive and with German titles, but no location (or Italian connection mentioned). So was it really Italy?

http://www.europafilmtreasures.eu/fiche ... htm?ID=322

Regards,

[shrike]

Also I was wondering about the physics behind the flat plate ASI - does it stay relatively accurate, or at the higher end of the speed envelope, does it loose precision - I ask, because if you look at it, the angles involved at higher speeds indicate less 'plate' relatively acted on by the airflow...

I do recall seeing one on a Tiger Moth calibrated as " Too Slow", "About Right" and "Too Fast", but at the time I was more interested in the owner's daughter than esoteric questions of physics<G>

[Baldeagle]

James, it's pretty well known footage among the Wright fanatics, April 24, 1909 at Centocelle. I'll check with my Wright connections and see if anyone knows who the cameraman was.




-

[The Inspector]

'Accuracy' on a Wright Flier or simular early airplanes @ about 45 mph? The flat plate indicators were probably no good above about 75 mph and should have been stamped 'REFERENCE ONLY' and as aviation progressed rapidly I'm certain that the requirement for more info went right up too ('you never know when I may need to shoot a precision approach using CAT III in about 100 years').

[barnbstormer]

"hi-tech" early French system.

[The Inspector]

'....carry the six.... add 9.....divide by'