First condition from Airforce: owning the fly-back function

Type 21 Chronograph Functionnality

It is equipped with a special mechanism called "Fly-back"

Which allows it to be instantly reset during the chronograph's operation by pressing the second button (B), without having to first stop the operation with the first button (A). When pressure is maintained on the second button, the hand stays at zero and only starts again when pressure is released.

The fly-back device enables an aircraft pilot or ship's captain to follow instructions and change headings according to a predefined course. Once a sequence has elapsed, pressure on the button launches the following sequence.

Start & Stop the chronograph: Press (A) Button

Reset the chronograph: Press (B) Button

Chronograph

second hand

360° inclined flange

Unidirectional

rotating bezel

Push button A

Crown

Minutes chronograph totalisator

Center seconds totalisator

Hours chronograph totalisator

Push button B

Window date indicator

F O N C T I O N S

The Type 21 is a very high-precision chronograph. It is equipped with a special mechanism

called fly-back enabling to measure pre-set time with continuous or interrupted operations.

This function enables to start, stop and restart the central hand telling seconds divided to the

5th as well as the hands telling minutes and hours.

The chronometer’s Start function is set by pushing the first push-button A. With a second

push on this button, the central hand is stopped. A third push on the same button re-starts

the chronometer hand. This enables to stop a time measurement and re-start it at the stop

mark.

Zero-setting function of seconds, minutes and hours is obtained by pushing the second

push-button B.

The Fly-back device allows it to be instantly reset during the chronographs operation by

pressing the second button (B), without having to first stop the operation with the first button

(A). When pressure is maintained on the second button, the hand stays at zero and only

starts again when pressure is released.

The device enables an aircraft pilot or ships captain to follow instructions and change

headings according to a predefined course. Once a sequence has elapsed, pressure on the

button launches the following sequence.

The rotating bezel completes the sums of minutes and hours by acting

as a countdown timer. For a four hour flight, the pilot enters the number

4 opposite the hour hand of the main dial, and starts the chronograph:

when the hour hand is opposite the luminous 0 mark, the four hours

have elapsed.

The tachometer measurement enables to know the plane speed when taking off on a short

runway. As a matter of fact, if the pilot has not reached the sufficient acceleration to take off

regarding a pre-set distance, he will choose to reverse the engine push in order to try to take

off again safely.