Uploaded December 2024 | Updated September 2026, 2 weeks ago

---

The Air Mileage Unit allowed navigators to track an aircraft's mileage and position from its departure point in real-time. It did this by balancing pitot pressure against an artificial pressure generated by an electric fan, calculating and integrating the aircraft's true airspeed. First developed during the Second World War, AMUs continued to be used aboard long-range RAF and RCAF aircraft like the Avro Lancaster and the V-bombers well into the Cold War era.

E6B Flight Computer Video: youtu.be/__0F6JAXj8U
Sextant Video: youtu.be/RnXauBYXPSE
Drift Sight Video: youtu.be/weT_cEWoCBQ
Astrocompass Video: youtu.be/xBScbuBYv0w
Astrograph Video: youtu.be/2RJqo5oNbWk

0:00 Introduction
1:27 Pitot-Static Systems
2:33 IAS, CAS, and TAS
3:56 AMU: Basic Operating Principle
4:36 Exterior Components
6:37 Internal Components
7:55 Low-Speed Diaphragm
8:49 Motor Feedback System
9:44 High-Speed Diaphragm
10:18 Compressibility Compensation
11:08 AMU Mk. II, III, IV, and TAU
12:19 Outro

SOURCES:

Air Navigation Vol. IV, Royal Air Force, RCAF Reprint 4M-10-51

rochesteravionicarchives.co.uk/items/air-mileage-unit

youtube.com/watch?v=s8XLeLa05JM&t=640s&pp=ygUbbGFuY2FzdGVyIG5hdmlnYXRvciBzdGF0aW9u

youtube.com/watch?v=ukhTnm1YCiI&pp=ygUdbmF2aWdhdGlvbiBhbmQgYm9tYmluZyBzeXN0ZW0%3D