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Ferranti FTS 21T turn and slip indicator

introduction permalink: http://www.amateurtele.com/index.php?artikel=334&id=#1528
In aviation, the turn and slip (or bank) indicator variant are essentially two aircraft flight instruments in one device. The pointer indicates the rate of turn, or the rate of change in the aircraft's heading. The 'spirit level' indicates whether the aircraft is in coordinated flight, showing the slip or skid of the turn.

The slip indicator is actually an inclinometer that at rest displays the angle of the aircraft's transverse axis with respect to horizontal, and in motion displays this angle as modified by the acceleration of the aircraft.[1] The most commonly used units are degrees per second (deg/s) or minutes per turn (min/tr).

The turn indicator does not respond to roll an pitch, only to yaw changes.

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connections / powersupply permalink: http://www.amateurtele.com/index.php?artikel=334&id=#1529
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pin
function
details
wire color
A
power input+28 VDCred
B
power input+28 VDC returnblue
C
chassis ground-green wire
D
dial illuminationapproximately +5VDCblack
E
not connected--
F
dial illuminationreturnblack


electrical power
The gyroscope and power indicator flag needs 28 VDC to pins A (positive) en B (negative/return). The current draw is approximately 270 mA continious. The power consumption (and heat generation) is therefore approximately 7,56 Watts. The power indicator flag is connected to the power input so has no separate connections. The power indicator flag is hidden at 15,5 VDC or higher voltatges.

downspin time
After removing the power, the gyroscope keeps spinning for quite a while. The spin down time is measured at approximately 10 minutes and 30 seconds.

pricing permalink: http://www.amateurtele.com/index.php?artikel=334&id=#1530
Expect a price tag of about 25...50 for this device in used condition.

indicators permalink: http://www.amateurtele.com/index.php?artikel=334&id=#1533
power indicator
The power indicator is a flag indicator to see if there's voltage applied to the instrument. The turn indicator works on a electrical powered gyroscope. The flag will (dis)appear at the threshold level of approximately 15,5 VDC. No flag means normal operation (power applied) and the striped marker indicates that the electrical power is absent or better said: below 15,5 VDC.

turn indicator
...to be written...

slip/bank indicator
...to be written...
Source: Text: https://en.wikipedia.org/wiki/Turn_and_slip_indicator

teardown permalink: http://www.amateurtele.com/index.php?artikel=334&id=#1535
There was lead tape around the housing which forms a seal between the front part and the cylindrical housing.

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The three recessed bolts which are radial placed in the rear panel needs to be removed. In the back plane of the rear panel are three small bolts placed. These three bolts presses a ring to the rear panel squeezing a rubber gasket ring to the housing creating an airtight housing. The three bolts can be removed, but loosening is probably sufficient. Applying some torque to the housing and the front plate, the housing can be slit to the rear of the device.

raw data permalink: http://www.amateurtele.com/index.php?artikel=334&id=#1543
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safety permalink: http://www.amateurtele.com/index.php?artikel=334&id=#1548
I was informed by Erik that it's possible that gyroscopes can be made of beryllium. High quality instrument grade beryllium can be used to get the desired level of performance. Gyroscopes are rotating with a very high speed so the gyroscope should be perfect balanced to avoid instability/damage. The desired performance and repeatability is possible using light weight materials like beryllium. Aluminium can also be used, but beryllium alloys like beryllium copper is probably used for high quality instruments. Beryllium copper is also known as BeCu (of CuBe).
Beryllium bronze and spring copper, is a copper alloy with 0,5...3 percent beryllium and sometimes other elements. Advantages of the combination is it's high strength so the gyroscope won't explode due to forces. Other advantages are that it is non-magnetic and non-sparking which is convenient for tools in explosive environments.

Beryllium alloys present a toxic inhalation hazard during manufacture. In solid form and as finished objects, beryllium copper presents no known health hazard. However, inhalation of dust, mist, or fume containing beryllium can cause serious health damage (lungs). IARC and NTP lists beryllium as a carcinogen.

warningBeryllium is carcinogen!
Avoid scratching, filing, sanding the metal to prevent spread of particles.

noteAs long as the metal is not damaged, it's rather safe to handle the metal.



Due to the copper coloured gyroscope in this instrument, it's very likely that the gyroscope is made of an beryllium alloy. The cylindrical bronze coloured 'ring' is the rotating part of the gyroscope.

klik hier voor de mobiele versie. (Beta test.)


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