Me109 speedometer

[Chris65]

Howdy folks;  sorry if this has been answered but I cannot find it in the manual, Chucks guide or here.  On the 109 speedometer in BOS there is an E on the left top of the speedo and an F on the top right, I have no idea what they mean or what the little box at the top of the speedo is.  Can someone point me in the right direction?

 

Thanks.

[Skycat1969]

I think you mean the instrument that is labeled "Altimeter" in Chuck's Guide for BOS. I haven't found what the E and F are for, but the little window in between is barometric pressure.

 

This is the description from the official guide for the DCS FW 190A-8:

 

Altitude Indicator

The altitude indicator determines the altitude at which the aircraft is flying by measuring atmospheric pressure. The instrument consists of 3 parts; the needle indicates altitude in tens of meters, the lower window shows the kilometer disk, and the upper window shows barometric pressure in Millibar. The gauge is graduated from fractions of 1 km from 0.0 to 0.99. The scale is 1/100 of a km, or 10 meters, throughout. The kilometer disk shows even kilometers of altitude, rounded down. The disk can show numbers from 0 to 9, for a total limit from 0 to 9.999 meters. The information shown by the meters needle and the kilometer disk should be added. For example, if the km disk shows 3 and the needle points at 0.4, the actual altitude is 3400 meters (3 + 0.4 km).

 

Edited December 18, 2022 by Skycat1969

[LukeFF]

1 hour ago, Chris65 said:

Howdy folks;  sorry if this has been answered but I cannot find it in the manual, Chucks guide or here.  On the 109 speedometer in BOS there is an E on the left top of the speedo and an F on the top right, I have no idea what they mean or what the little box at the top of the speedo is.  Can someone point me in the right direction?

 

Thanks.

 

The E and F markings are for QFF and QFE barometric pressure:

 

Quote

In the version for pilots, the altimeter has 2 adjustable marks on the front with the designations "F" and "E", which represent the pressure values QFF and QFE. With the help of these 2 marks and a white mark behind the instrument glass, the pilot could note the prevailing air pressure at the take-off site as well as that at the landing site.

 

This standard device of the German Air Force was manufactured in very large numbers and was installed in numerous aircraft types. A fine altimeter was combined with a coarse altimeter to save space and weight.

 

The barometric device, with diaphragm cell measuring mechanism and static pressure compensation, reacts to the smallest changes in air pressure, with the dial being calibrated in meters/kilometers instead of millibars.

 

In the lower area of the dial there is a section behind which a rotatable disc is mounted, which shows the kilometers in altitude (0-10 km). The pointer itself shows the altitude (each in 100m figures, 0.0 - 1.0 km). With a complete circle of the pointer in a clockwise direction, 1 km more is displayed on the dial (altitude kilometer). If the pointer is rotated counterclockwise, the displayed altitude decreases accordingly.

 

In the upper area of the dial there is a cut-out behind which a disc for the air pressure that can be adjusted with a rotary knob (below on the front) is stored. This disc is labeled (printed or engraved) with the air pressure values from 930-1050 millibars.

 

Functionality:

 

The type of altitude measurement that is still common today, especially that of absolute altitude, is done barometrically, with the decrease in air pressure with altitude being measured by membrane cans. Barometric measurements suffice to indicate the absolute height, but the accuracy of these devices is far too low if the precise height above the ground is to be determined for pronounced blind landings (e.g. in ground fog or at night) or for bombardments from high altitude.

 

To save weight and space, this device combines a coarse and a fine altimeter. That is why the altimeter is equipped with a pointer and a number disc.

 

The fine/coarse altimeter works according to the barometric principle. The device housing has a connection on the back through which the static pressure can act on the closed, air-free membrane cans (2-3).

 

The stroke of the can is transmitted to the pointer of the display device via a lever mechanism. Since the static pressure inside an aircraft is not the same as in the free atmosphere, this is usually taken from the Pitot tube of the airspeed indicator. With the help of an adjustment wheel on the front, the device can be given any basic setting. It can also be used to correct barometric pressure fluctuations that prevail on the earth's surface. By operating the adjusting screw, the entire measuring mechanism (box system including pointer) is shifted, while the scale (dial) remains stationary.

 

https://www.deutscheluftwaffe.de/funktionsweise-hoehenmesser-fl-22320-fl-22322

 

Edited December 18, 2022 by LukeFF

[Skycat1969]

LINK: EXCELLENT condition and all dial work smoothly and correctly. (milcollectibles.com)

Edited December 18, 2022 by Skycat1969

[LukeFF]

1 minute ago, Skycat1969 said:

LINK: EXCELLENT condition and all dial work smoothly and correctly. (milcollectibles.com)

 

Since it appears the E and F tabs could be freely moved around the bezel, my guess is that they are a pilot aid to help stay within a predetermined altitude.

 

Have a look above. ?

[Skycat1969]

I did.

 

 

Edit: Found this: 

Sometimes reading alternate explanations helps me understand better. Also, I looked up the difference between QFE, QFF, and QNH. I learned something new today ... that I'll forget by next week. 

Edited December 18, 2022 by Skycat1969

[czech693]

Neat device.  Setting the altimeter to the pressure setting for zero airport elevation would be handy in flying the pattern and especially useful in flying an instrument approach.  Those who have a hard time doing mental math sometimes get the altitude wrong.  If the airport is at 1223 ft MSL and you want to fly the pattern at 800 ft above the airport, you have to remember to fly with the altimeter at 2023 ft.  Instrument approachs are even harder as your Missed Approach Point altitude is more critical.  Some airplanes have an altimeter bug that can be set on the altimeter.  But, using zero for the airport altitude is useless for flying anywhere other than the airport pattern as the terrain is given in elevation above sea level (MSL) on the sectionals, at least here in the US.  This sim doesn't give terrain elevation on the maps so it's kinda a moot point except for mission altitude.

[AndyJWest]

Good luck to anyone trying to do an instrument approach in a Bf 109. ?

[Chris65]

Thank you all for the replies.  I realized last night while watching HNIC that I wrote speedometer instead of altimeter, but you knew what I was talking about. 

 

In COD I always set my hurricane altimeter to zero, for me it works and makes landing much easier.

[Customizer171]

There's an E and an F on the altimeter in the Me 109 F.

What does that mean?

 

There's also two small red triangles at the top.

What's that for?

[czech693]