Rare, NEW, original and working condition WWII German Luftwaffe Ln.28330-1 radio altimeter AFN 101 A, 1944. It was used in the Do 335, He 219, Ju 88, Bf 110 and other German aircrafts. Instrument is complete and comes with connectors.
Designation: Radio altimeter AFN 101 A
Requirement mark: Ln.28330-1
Device number: 124-1409 B-1
Measuring range: 0-150m / 0-750m
Manufacturer: hcd
Year of construction: approx. 1944
Installed in: Dornier Do 335, Heinkel He 219, Junkers Ju 88, Messerschmitt Bf 110
Particularities:
2 measuring ranges selectable
How AFN 101 works:
The method of measuring altitude that is still common today, especially absolute altitude, is done barometrically, with the decrease in air pressure with altitude being measured using membrane cans. Barometric measurement is sufficient to indicate the absolute height, but the accuracy of these devices is far too low if the exact height above ground is to be determined for blind landings (e.g. in ground fog or at night) or for high-altitude bombings. These measurements are carried out electrically using ultra-short wave devices. The radio altimeter is used to measure/display the exact altitude above ground. The complicated radio measuring system was usually installed in the wing. A signal is sent from the transmitter (transmitting antenna) towards the ground (land, water, snow, mountains, etc.) and then reflected back to the receiver (receiving antenna). The current altitude can be displayed directly using a frequency counter and a moving coil instrument (AFN 101a). The radio altimeter can display 2 different measuring ranges (0-150m / 0-750m height above ground). The preselection of the respective measuring range can be preselected using the switch knob on the lower front of the housing. The measurement accuracy of the FuG 101a system was +/- 10% of the respective flight altitude. The device was particularly helpful and important when flying over water, over mountains and of course during night flights, where barometric altitude measurement could only provide inaccurate measurement results of the actual “height above ground”.