34 replies to this topic

[Lyffe]

Insall, in "Observer" - his memoirs of the RFC during WW1, makes a number of references his 'wristlet aneroid' which was "strapped around my left instep".  At the time he was an observer flying in the Vickers FB5. I assume this refers to a portable altimeter, but was this a standard issue or something he would have obtained privately?  

Whatever the answer could anyone direct me to a photograph of the instrument please?

He also refers to his wrist-watch being strapped to his other foot.  Given the confined space of the observer's cockpit, some interesting contortions must have been needed to read either instrument. I'd appreciate any advice as to how an observer would have been able to use either instrument.  

Brian

[centurion]

Lyffe, on 21 April 2012 - 10:32 AM, said:

<br>Insall, in "<i>Observer</i>" - his memoirs of the RFC during WW1, makes a number of references his 'wristlet aneroid' which was "<i>strapped around my left instep</i>".&nbsp;&nbsp;At the time he was an observer flying in the Vickers FB5. I assume this refers to a portable altimeter, but was this a standard issue or something he would have obtained privately?&nbsp;&nbsp;<br><br>Whatever the answer could anyone direct me to a photograph of the instrument please?<br><br>He also refers to his wrist-watch being strapped to his other foot.&nbsp;&nbsp;Given the confined space of the observer's cockpit, some interesting contortions must have been needed to read either instrument. I'd appreciate any advice as to how an observer would have been able to use either instrument.&nbsp;&nbsp; <br><br>Brian<br>

<br><br><p>The front cockpit in the FB5 pusher was comparatively roomy and assuming that each instrument was strapped round the instep so the dial was on top of the foot he would have been able to glance down and read them. The question is why would the observer need an altimeter?. Some FB2's had dual controls so one can only assume it was to allow the observer to fly the aircraft if necessary. With the forward gun mounting there was no place in the observers cockpit for an instrument panel.

</p><p>Before the war many aviators wore instruments about the person as cockpits were primitive or even non existent.. It was quite normal to have the altimeter strapped to the thigh so they would have been available for private puchase in 1914/15 which is when the FBE was used operationally</p>

[Lyffe]

My thanks C; in this instance there definitely weren't any dual controls.  I can't answer why Insall needed an altimeter, but his account makes several references to altitude at particular times during sorties, which suggests he must have had some means of determining it.  

In describing an operation during which the tail-wind was especially strong he writes:

"Up to that moment I had not unduly concerned myself with the strength of the wind, but now, looking down at the ground, I could scarcely believe my eyes when I saw our meeting point (with a force of BE2c's) practically underneath.  The last time I had taken any note of our position the towns of Albert and Bray and the trench-lines beyond had been a long way ahead.  I glanced quickly at my wristlet aneroid strapped round my left instep, took a note of the time from my wristwatch on the other foot, and tried to calculate the strength of the wind."  

Goodness knows why he felt moved to mention the aneroid, but he does and it interests me in respect of something else I'm working on - hence my query.

From your description I'd assume the face of the instrument must haver been quite large, but I'd dearly like to trace a photo or other image.

Brian

[Andrew Upton]

Lyffe, on 21 April 2012 - 10:32 AM, said:

Insall, in "Observer" - his memoirs of the RFC during WW1, makes a number of references his 'wristlet aneroid' which was "strapped around my left instep".  At the time he was an observer flying in the Vickers FB5. I assume this refers to a portable altimeter, but was this a standard issue or something he would have obtained privately?  

Possibly a reference to an aneroid barometer, rather than than an aneroid altimeter? In the context of trying to work out wind speed knowing the general weather conditions and changes to my mind makes more sense than knowing your height.

[centurion]

Andrew Upton, on 21 April 2012 - 04:18 PM, said:

Possibly a reference to an aneroid barometer, rather than than an aneroid altimeter? In the context of trying to work out wind speed knowing the general weather conditions and changes to my mind makes more sense than knowing your height.

Effectively the same thing. As you go higher the air pressure drops. A barometer measures air pressure not the weather - effectively if the air pressure increases the sort of barometer one had in the hall would move an arrow on a dial to set fair if it dropped it would move it to stormy weather as increases in air pressure usually are a sign of coming calm weather and falling indicates a coming storm. No real difference between an aneroid Barometer and an aneroid altimeter. This was the problem with altimeters on WW1 night fighters, a low pressure area coming in could make your altimeter show you higher than you actually were and your last thought could be "what are sheep doing in that cloud?" A barometer is used as a predictor of general weather conditions to know what current weather conditions are you look out of the cockpit.

[Lyffe]

Yes, the construction of the aneroid barometer and altimeter is essentially the same, the main difference being that the face of the barometer is graduated in millibars (or inches in WW1) and in feet on the altimeter.

The concept of sheep in clouds is fundamently correct, but it would take a really exceptional fall of pressure during the period of a sortie over a fixed area of operation to have any significant effect.  The effect would be most noticeable when flying a relatively long distance, say London to Edinburgh, with high pressure over London and low pressure over Edinburgh.

[centurion]

A number of accounts of night flying in WW1 suggest that the margin of inaccuracy in the altimeters of the day was about 150 feet which could really spoil your night when trying to locate a landing strip in the dark, especially if you wern't quite sure where you where.

[Andrew Upton]

centurion, on 21 April 2012 - 07:08 PM, said:

Effectively the same thing... A barometer is used as a predictor of general weather conditions to know what current weather conditions are you look out of the cockpit.

Effectively yes, practically no. Though they work on the same principal I don't look at the barometer before I go outside to know what height I'm at. As the goal seems to have been to work out wind strength knowing what the weather was possibly changing to and from seem very logical factors in affecting the end result.

[centurion]

Andrew Upton, on 21 April 2012 - 11:09 PM, said:

Effectively yes, practically no. Though they work on the same principal I don't look at the barometer before I go outside to know what height I'm at. As the goal seems to have been to work out wind strength knowing what the weather was possibly changing to and from seem very logical factors in affecting the end result.

 Your barometer only tells you what the air pressure is at the moment. It only predicts what the weather will be.It has zilch to do with air speed.  I assume you still look out of the window to see if its raining at the moment. 

[Starlight]

With regards the usefulness of an altimeter for an observer, knowing the altitude of the aircraft would have aided him in estimating the distance between himself (viz. the aircraft) and what he is observing (eg. landmarks, troop positions, ammunition dumps). Obviously, the higher the altitude, the further away the skyline is.

[centurion]

 Given that he says that he is estimating the force of the wind (I assume that he means windspeed) and if the wind was behind the aircraft then his watch can help him calculate the ground speed (using the distance between current position and that the last time he looked at his watch). Taking this and subtracting the normal speed of the aircraft would give him the speed of the tail wind - however the normal speed will be higher if the aircraft is in a shallow dive (and slower if climbing) so he also needs to know if there has been any change in in altitude over that distance. 

[Andrew Upton]

centurion, on 21 April 2012 - 11:14 PM, said:

  It only predicts what the weather will be.It has zilch to do with air speed. 

Still disaggree - our barometer indicates weather in degrees as "Stormy, Much Rain, Rain, Change, Fair, Set Fair, and Very Dry". Any change towards the first half from the middle is likely to be accompanied by increasing wind-speed.

[centurion]

Andrew Upton, on 22 April 2012 - 10:56 AM, said:

Still disaggree - our barometer indicates weather in degrees as "Stormy, Much Rain, Rain, Change, Fair, Set Fair, and Very Dry". Any change towards the first half from the middle is likely to be accompanied by increasing wind-speed.

But it still tells you zilch about what the wind speed is at any particular moment.

[Lyffe]

Thanks for your continuing comments gentlemen, much appreciated.  By good fortune I've traced an example of the instrument to the Barometer World Museum, at Merton near Okehampton.

Andrew,

Your barometer is stationary and the change in pressure being registered is reflecting the change at your location only.  Falling pressure sometimes indicates the approach of a depression or weather front, whilst rising pressure sometimes indicates the approach of a ridge of high pressure or anticyclone.  I use the word 'sometimes' advisedly as there is also a background diurnal change in pressure mixed into the equation - there is a decrease in pressure late in the night and during the afternoon, and an increase during the morning and evening.

That apart, a single pressure reading does not tell anything about the wind, for that you need a network of barometers located over a wide area, with all the readings made at the same time and reduced to a common level - sea level.  If the readings are plotted on a chart isobars (lines of equal pressure) can be drawn, and it's the distance apart and direction of the isobars that gives the indication of wind speed and direction.  A simple rule is that if you stand with your back to the wind in the northern hemisphere low pressure is always on your left - the reverse applies south of the equator.

However, an aeroplane mobile is not stationary, and if you placed a barometer in an aeroplane it will react to changes in pressure in two senses:

1. It will fall as the aeroplane ascends and rise as it descends - but that tells you nothing about the movement of weather systems.

For example I've attached a trace recorded by a barograph during an ascent by a DH9 over Bircham Newton on 3 May 1919; the aeroplane took off at 1002 GMT and landed at 1137 GMT.  Between those times it climbed slowly to 16000 ft directly over the airfield then made a rapid descent. The heights, in feet, are on the left; 5000 ft (the first height) equates to a pressure of 850 millibars, 10000 ft (the second height) = 700 millibars.

2. The barograph will also respond to changes in pressure as it flies across the terrain, but the changes will be very small relative to the large changes resulting from a change in altitude - as shown in the attachment.

Another thing to remember is that aviators had very little meteorological knowledge at this time - it certainly wasn't included in an observer's training in 1915-16 - but that is immaterial.  Even today it is impossible to gain any indication of present wind conditions by just looking at a barometer.

Brian

Attached Files

•  Altimeter trace.jpg   98.27K   0 downloads

[ScorpioUnbound]

What ho all.



I wonder if this is the sort of thing that was being talked about being a combined compass and altimeter from the Shuttleworth Collection.



Cheer ho.
John

Attached Files

•  Knee Altimeter and Compass Shuttleworth Collection (Sf).jpg   50.08K   0 downloads

[Lyffe]

I think we've spoken before John, but thank you for posting the image here.  For everyone else the exchange is at http://www.theaerodr...-altimeter.html .

I've been a little thrown now as my first impression was that this could well be what I'm seeking, although I think the labelling is misleading in that the instrument looks like a compass rather than compass/altimeter as described.  However, another contributor has come up with another photo of a smaller instrument strapped to a pilot's wrist that might be an altimeter given Centurion's earlier advice.  I just wonder if it is too delicate to be belted to a thickly covered arm or wrist.

Brian

[ScorpioUnbound]

Lyffe, on 22 April 2012 - 03:54 PM, said:

I think we've spoken before John, but thank you for posting the image here.  For everyone else the exchange is at http://www.theaerodr...-altimeter.html .

I've been a little thrown now as my first impression was that this could well be what I'm seeking, although I think the labelling is misleading in that the instrument looks like a compass rather than compass/altimeter as described.  However, another contributor has come up with another photo of a smaller instrument strapped to a pilot's wrist that might be an altimeter given Centurion's earlier advice.  I just wonder if it is too delicate to be belted to a thickly covered arm or wrist.

Brian

Indeed we have and I'll repeat my request here that any Shuttleworth volunteer who signs in on this site and can get oily fingers on this artefact and therefore offer a description of its functionality would put a lot of minds at rest (well two anyway).
Regards



John.

[centurion]

Or it could be in the way when operating his Lewis gun http://scilib.narod..../images/022.jpg

He might need to remove a gauntlet to be able to clear a jam and this might be difficult if he had an instrument strapped over it. If it was worn straight on the wrist the gauntlet cuff would make it very dificult to read it. As the photo on the link shows the cockpit was relatively roomy

[MikeMeech]

Hi All

I have had a look in the G1098-33c for July 1917, 'Mobilization Store Table for the Expeditionary Force RFC Aeroplane Squadron' - This is for  a 18 aircraft (Service) Sqn or the 24 aircraft (Corps) Sqn.  On page 7 two types of 'Aneroids' are listed:

'Aneroids 0-10,000 feet or 12,000 feet' of which there are 24 on the sqn.   These I believe were fitted to the aircraft as the next item is:

'Aneroids, wrist' of which there were 14 on the sqn, that was 12 Observer and 2 spare.

I hope that is of interest.

Mike

[truthergw]

How delicate were these instruments? Centurion points out that the observer had a lot to do. Perhaps too much for the altimeter to handle?

[centurion]

 BTW forgot to mention - the man in the cockpit is Lieutenant A. J. Insall himself. 

[Lyffe]

Centurion,

Thanks for your thoughts; I was coming more to that line of thinking as I had tea.  Interesting photo, typical (from my point of view) that his instrument isn't visible!

truthergw,

The instruments are remarkably robust and have few moving parts (three).  For the inside of an aneroid see ; the presentation's not the best but it gives a reasonable idea of the linkage - lasts slightly less than three minutes.

Mike,

The quote from 'Mobilization Store Table for the Expeditionary Force RFC Aeroplane Squadron' answers my question nicely.  Much obliged.

Brian

[truthergw]

I have never fired a lewis gun but I have fired a vickers and a Bren. I don't think that it would be good for an altimeter strapped to my wrist. I should think that it would at least need a minute or two to settle down before reading, as would a compass.

[Lyffe]

Digging around I've just found this item advertising wristlet altimeters in the 12 March 1915 edition of Flight:

http://www.flightglo...search=Wristlet

The manufacturer claims it's capable of being read at 2-3 yards which would fit with Insall's claim of his instrument being strapped to his foot.  

Brian

[nils d]

centurion, on 22 April 2012 - 04:29 PM, said:

Or it could be in the way when operating his Lewis gun http://scilib.narod..../images/022.jpg

He might need to remove a gauntlet to be able to clear a jam and this might be difficult if he had an instrument strapped over it. If it was worn straight on the wrist the gauntlet cuff would make it very dificult to read it. As the photo on the link shows the cockpit was relatively roomy

Centurion
One cant class the observers cockpit as "roomy",it was a bit cramped otherwise Insall would fix his instruments to the cockpit rim rather than the poor alternative of his lower limbs.That was quite a shallow cockpit and not as spacious as the FE2 gunners position.The Vickers cockpit doesnt look half as safe to me.