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Anemometers and Airspeed Indicators

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This is something of a spin-off from Olham's 'Albatros D.V Cockpit Variations' thread. To me it's always been a rather confusing subject given the paucity of information (that I've found) on the subject. Especially as regards to airspeed measurement.

 

Lets see if I have this right.

* The Germans went down the line of using 'Anemometers' for measuring airspeed. The actual speed dial could either be mounted on the wingstrut with the vane, or mounted within the cockpit? Was there any rhyme or reason for not placing it in the 'obvious' location? I.E. the cockpit

 

* The British used the pitot tube for airspeed measurement, with the dial mounted in the cockpit. I'm guessing that British dials would have been highly prized by German aviators?

 

* What did the French use?

 

Now both the anemometer and the pitot tube (in various forms) had been around for more than a century prior to the age of flight, and were quite widespread in both civil and naval use. Yet I gather that many (early) aircraft were not fitted with them. Given the crucial need to know airspeed, especially in relation to either stall or overstressing, one would think that it would be the primary instrument fitted to any aircraft.

 

By the by does anyone have a complete list of which aeroplanes in the Great War didn't have an airspeed indicator or some sort or another?

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First off, you have to be sure you're arguing from the right assumptions. Did WW1 pilots really have a "crucial need" to know their airspeed? I contend that unless they were doing dead-reckoning navigation, they did not. As evidence, I cite my own experience in OFF, where I can't remember the last time I needed to know more about my airspeed than what my eyes were telling me. And this is sitting at my desk, without any tactile feedback from the seat of my pants, no wind in my face, etc. Seriously, the only instruments I ever use with any regularity in OFF are the slip indicator, the tachometer, and (after a disorienting fight across the lines) the compass.

 

On your list of types of ASIs, you forgot one, though. Some planes had a metal rod with a piece of sheet metal welded to the end of it. When the plane was at rest, the rod hung straight down but as the plane moved, the wind on the sheet metal bent the rod back. Thus, the rod acted as the needle of a gauge and was hung on a strut in front of an arc with various speeds marked off on it.

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Did WW1 pilots really have a "crucial need" to know their airspeed? [...] I cite my own

experience in OFF, where I can't remember the last time I needed to know more about my

airspeed than what my eyes were telling me.

 

My same thought. I have been flying in a motorised sailplane, and even piloted it for a bit, and I couldn't only

see when we got too slow (climbing to steep), but also kind of feel the forward energy drop towards zero.

I know that this seems to get lost without visual confirmation (in clouds), but combined with vision it is present.

 

...the only instruments I ever use with any regularity in OFF are the slip indicator,

the tachometer, and (after a disorienting fight across the lines) the compass.

 

Even worse here: I only need to know my Altitude occasionally, and the compass.

Flying an aircraft with fragile lower wings makes you learn to be careful with airspeed (in dives).

You just KNOW, what you better not dare.

 

The only "gauge" I am missing in these kites is a coffee machine. :search:

 

.

Edited by Olham

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.

 

It's called seat-of-the-pants flying for a very good reason. My experience in ultralights has shown me that the pilots of these early kites trusted the "feel" of what was happening far more than they looked to the instruments to tell them. And as far as forward air speed was concerned, you could likely be as accurate as you needed to be by simply tying streamers to your outboard wing struts. When those lost their flutter and began to droop you could make book that a stall was coming PDQ. As things developed and the need came along for highly accurate aerial navigation air speed indicators came into their own, (as did a host of other instruments), but throughout most of WWI they were not looked at as anything of great importance.

 

.

 

And a coffee machine Olham? Yes, I suppose an espresso maker would be too heavy.

 

.

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@ Olham:

You really need to look at your tachometer more often. It's about the single most important instrument in any plane with synchronized guns. This is because synchronization only worked reliably within certain RPM bands. If you fired while at the wrong RPM, you could shoot your prop off. That's why the tachometer was so big and mounted at the top center of the instrument panel, so you could easily glance quickly down at it before pulling the trigger.

 

This isn't modeled in OFF but it's something I do anyway just for immersion.

 

@ Lou:

I used to fly sailplanes and the slip indicator was a short piece of string taped at its lower end to the outside of the windshield. If you were slipping, it would lean over to the side instead of pointing straight up. It worked the opposite of the ball, however. If the string was leaning to the right, you applied left rudder.

 

The reasion I use the slip indicator in OFF is because if you don't have that centered, your bullets will go off to the side of where you're aiming. So, besides checking my tachometer just before I shoot, I also check the slip indicator.

 

@ Hasse Wind:

Yup, that's the 1 thing I like about the SPAD :).

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So - the tachometer here is rather an instrument to show the RPM of the engine?

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.

 

No Olham, it shows you how fast you're spinning. :grin:

 

 

 

 

Yes, the tach is there to indicate engine RPMs.

 

.

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Damn - and I always thought the tachometer shows your speed???

On my motorbike, or in German cars, a tacho is for showing your speed. Seriously.

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.

 

Over here in the States the tachometer shows engine RPMs while the speedometer shows vehcile speed. So Olham, what do you call the instrument on your dash that indicates engine RPMs?

 

.

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Drehzahlmesser.

 

When I enter "Tachometer" in German WIKIPEDIA, it gives me what you call speedometer.

When I click on "English" then, it also says "speedometer".

Edited by Olham

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Whoops, never mind. Asked and answered already....

 

Well, whatever you call it, for God's sake be sure to glance at it before pulling the trigger ;)

Edited by Bullethead

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"Revolutions-counter" so to say. Counts the RPM.

Edited by Olham

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Oddly enough the RCAF T-33 a 50's era jet trainer had simple slip indicator on the nose of the aircraft. It consisted of a white stripe painted on the anti-glare section of the nose with a red cord attached to the forward end. Of course the instrument panel also had a turn and bank indicator. I have a picture but have no Idea how to post it.

 

Tony

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Lou, we have on German motorbikes a Drehzahlmesser (RPM-counter)

and a Tachometer (Speedometer).

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The use of term Tachometer in English for (RPM-counter) is very strange to me too, being Greek...

The word is Greek and means literally Speedometer (tachytis=speed + metron=meter).

Edited by elephant

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Hmmm. Maybe this confusion came about because the 1st engines (steam) were stationary powerplants for mills, factories, mines, etc. As such, the only speed that mattered was RPM, so the inventers coined the word "tachometer" for that. Then, when steamboats, trains, and other motor vehicles came along, it became important to know how fast the vehicle was moving. But the word "tachometer" was already being used for RPM so they had to invent "speedometer".

 

This is all just a guess, but I could see it happening.

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elephant, that's what I also found out - thanks!

 

Bullet, in Greece and in Germany, Tachometer has never been used in the term of RPM counter.

That confusion must belong to the British (who passed it on to America) - they always have a bit

of their own ways in Europe (driving on the left side of the road - imagine I would try that here... !)

:big_boss::hyper::pilotfly:

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Here is a Tachometer from the VW Golf - the numbers show "kilometers per hour".

 

 

 

(But, to complete the confusion: all Tachometers DO of course gain their shown values

from the revolving speed of the engine).

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And now, to add even further confusion: I have just found an item on EBAY -

an original WILHELM MORELL Tachometer in original casing (!).

If only I had the money...

 

Well, and this tachometer seems to be based on the RPM (Uml/min = Umläufe pro Minute).

Seems you had to calculate your speed from these values - not sure.

 

 

 

 

The airspeed was read from the external device fixed to the wingstrut, as was already noted here.

Here is a quote from "THE VINTAGE AVIATOR" report "Notes on flying the D.Va" by Gene deMarco:

 

“The engine has a tremendous amount of power...”

 

As the take off is started you are amazed at how much movement can be seen in the upper wing relative

to the fuselage, the first instinct is to close the throttle and look for some missing brace wires.

Fortunately a little experience with this type prepared me for this, and I kept going. The movement comes

from the lack of cross bracing in the center section area and the monocoque fuselage changing shape as it

becomes airborne. The engine has a tremendous amount of power and the Albatros climbs well, you need

to look out on the Right hand wing strut to see the airspeed, a small wind driven anemometer displays the

airspeed in Kilometres Per Hour. The airspeed indicator in itself is a work of art.

 

[from Gene deMarco's 'Notes on flying the D.Va' at "The Vintage Aviator" website.]

Edited by Olham

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PS: there are other pages with more instruments in that site - really good quality pictures; like this "Barograph".

 

 

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...and last not least: the RPM counter. (Uml. p. min. = Rounds per minute).

 

 

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Ah, but no! A speedometer (Tachometer to you, Olham) gets it's speed from the output shaft of the transmission, as the rpm's of the motor can be the same at different speeds depending on what gear you are in!

 

It's amazing the things I learn on this forum... no doubt my favorite!

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