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Trim Indicator

Technical Information

Catalogue No: C0349
Category: Flight Control
Object Type: Indicator/Instrument
Object Name: Trim Indicator
Part No: 3C789
Serial No: 406/61
Manufacturer: Elliott Bros (London) Ltd
Division: Unknown
Platform(s): Buccaneer
Year of Manufacture: 1961
Dimensions: Width (mm): 33
Height (mm): 33
Depth (mm): 64
Weight (g): 100
Location: Triple Shelf Unit, RH (indicators) [Main Store]

Trim Indicator
Type No. 3C789
Ref No.
Serial No. 406/61
Elliot Bros (London) Ltd


A Trim Indicator provides a simple visual indication of nose or tail heaviness of an airplane in flight. If the bar is horizontal and unbroken then the aircraft is correctly trimmed. The Indicator Part Number and date within the Serial Number would suggest that this little device could have been fitted to a Buccaneer.
This indicator shows trim being applied by the autostabiliser actuator. It shows that if the FCS Engage switch is moved to "OFF", the the aircraft will pitch in the direction shown by the indicator, and will require manually trimming back.
This indicator may show the error between the autopilot elevator angle demand, and feedback of the elevator angle as it is connected directly to the flight control computer and the auto trim amplifier.
Internally it is another watchmaker's masterpiece. It uses a delicate moving coil and permanent magnet, and a light watch-spring to operate the pointer.
A later version on the Lightning is shown in
Lightning Trim Indicator

Click to enlarge